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To meet the challenges of African agriculture, particularly food self-sufficiency, job creation and wealth, the agricultural contract model is being promoted by some governments and international donors in the framework of a performative discourse on the virtues of partnerships between agro-industries and producers. However, agricultural contracts give rise to contradictory interpretations. Some see it as a model that would have spillover effects on the rural economy, while others see it as a strategy of predation of agricultural resources, which is harmful to local communities. On both sides, analyses remain focused on ethical and sometimes ideological issues. The operating conditions of the contracts and their impacts in terms of development are little addressed. Our contribution, based on sociological surveys conducted in Senegal, aims at objectively characterizing the forms of interaction (positive or negative) between agricultural contracts and the development of the territories where the rice sector is located. On the basis of these issues of articulation between agricultural development and territorial development, we are proposing a methodological approach to carry out this type of diagnosis. At the scale of the regions dominated by rice growing, we highlight that the territorial trajectories are contrasted in relation to the interaction between the agricultural model and territorial development. This diagnosis is interpreted through the knowledge of the systems of actors, in particular with the help of two indicators, namely centrality, which gives an indication of the issues of territorial governance, and the density of social relations, which provides information on the importance of the agricultural contract in relation to other modes of relationship building. With regard to the insertion of agricultural contracts, the structure of the networks of actors makes it possible to identify a centralized mode of governance at the level of the national agricultural bank and a few agro-industrial enterprises. Nevertheless, informal relationships and traditional local structures (families, friends, neighbors) persist and function in parallel with the agricultural contract, calling into question the political discourse regarding the transformative potential of agricultural contracts. [ABSTRACT FROM AUTHOR]

To meet the challenges of African agriculture, particularly food self-sufficiency, job creation and wealth, the agricultural contract model is being promoted by some governments and international donors in the framework of a performative discourse on the virtues of partnerships between agro-industries and producers. However, agricultural contracts give rise to contradictory interpretations. Some see it as a model that would have spillover effects on the rural economy, while others see it as a strategy of predation of agricultural resources, which is harmful to local communities. On both sides, analyses remain focused on ethical and sometimes ideological issues. The operating conditions of the contracts and their impacts in terms of development are little addressed. Our contribution, based on sociological surveys conducted in Senegal, aims at objectively characterizing the forms of interaction (positive or negative) between agricultural contracts and the development of the territories where the rice sector is located. On the basis of these issues of articulation between agricultural development and territorial development, we are proposing a methodological approach to carry out this type of diagnosis. At the scale of the regions dominated by rice growing, we highlight that the territorial trajectories are contrasted in relation to the interaction between the agricultural model and territorial development. This diagnosis is interpreted through the knowledge of the systems of actors, in particular with the help of two indicators, namely centrality, which gives an indication of the issues of territorial governance, and the density of social relations, which provides information on the importance of the agricultural contract in relation to other modes of relationship building. With regard to the insertion of agricultural contracts, the structure of the networks of actors makes it possible to identify a centralized mode of governance at the level of the national agricultural bank and a few agro-industrial enterprises. Nevertheless, informal relationships and traditional local structures (families, friends, neighbors) persist and function in parallel with the agricultural contract, calling into question the political discourse regarding the transformative potential of agricultural contracts. [ABSTRACT FROM AUTHOR]

• New receivers for time synchronization of MIMO systems in the presence of interference are proposed. • These receivers are compared with those of the literature from a performance and a complexity point of view. • The optimization of the number of transmitted antennas is investigated for deterministic and random channels. • Receivers of the literature without interference are compared in a unified framework with the GLRT1 receiver. The time synchronization of (M × N) MIMO systems has been studied this last fifteen years, for both single-carrier (SC) and multi-carriers links. Without any interference, most of the available receivers assume orthogonal sequences. With interference, the current most powerful receiver is a generalized likelihood ratio test (GLRT) receiver, assuming unknown, stationary, circular, temporally white and spatially colored Gaussian noise. However, this receiver is more complex than its non-GLRT counterparts, which, unfortunately, do not perform as well in most cases. In this context, the purpose of this paper is to get new insights into the time synchronization of SC MIMO links, both without and with interference, in order to overcome the limitations of the available receivers. In the absence of interference, the MIMO GLRT receiver is computed and compared to the existing ones in a unified framework, enlightening its better performance. In the presence of interference, as the complexity is an important issue in practice, several ways to decrease the complexity of the available GLRT receiver while keeping its performance are proposed, enlightening the great practical interest of the proposed schemes. Finally, the optimization of the number of transmit antennas is investigated, enlightening the existence of an optimal value of M depending on the channel matrix. [ABSTRACT FROM AUTHOR]

Linear beamformers are optimal, in a mean square (MS) sense, when the signal of interest (SOI) and observations are jointly Gaussian and circular. Otherwise, linear beamformers become suboptimal. When the SOI and observations are zero-mean, jointly Gaussian and noncircular, optimal beamformers become widely linear (WL). They become nonlinear with a structure depending on the unknown joint probability distribution of the SOI and observations when the latter are jointly nonGaussian, assumption which is very common in radiocommunications. In this context, the paper aims at introducing, for small-scale systems, third-order Volterra minimum variance distortionless response (MVDR) beamformers, for the reception of an SOI, whose waveform is unknown but whose steering vector is known, corrupted by nonGaussian and potentially noncircular interference, omnipresent in practical situations. Properties, performance, complexity, and adaptive implementation of these beamformers in the presence of nonGaussian and potentially noncircular interference are analyzed in this paper. These new beamformers are shown to always improve, in the steady state, the performance of Capon beamformer for nonGaussian/circular interference, whereas some of them improve the performance of the WL MVDR beamformer for nonGaussian/noncircular interference. These new beamformers open new perspectives for spectrum monitoring of nonGaussian signals and for radiocommunication networks using such signals. [ABSTRACT FROM AUTHOR]

Tourism development has been a particularly intense area of negotiation in the Spanish countryside since the 1990s because of its major role in public policies for the economic restructuring, the regionalisation of policy instruments and its own intersectoral nature. This leads us to examine how the coordination takes place within the actors engaged in the tourist development of Sierra de Albarracín. This research adopts an inductive approach to the social relations that underlie the construction of a tourism project territory. From the meeting between the methodology of the social network analysis and the analytical framework of the School of Proximity, the procedure presented here helps to understand the logics of territorial construction. Cooperation appears more fictitious than the policy instruments of governance envisage. Questioning both cooperative and conflictive proximities offers new clues for the evaluation of public policy instruments. [ABSTRACT FROM AUTHOR]

Widely linear (WL) receivers have the capability to perform single antenna interference cancellation (SAIC) of one rectilinear (R) or quasi-rectilinear (QR) co-channel interference (CCI), a function which is operational in global system for mobile communications (GSM) handsets in particular. Moreover, SAIC technology for QR signals is still required for voice services over adaptive multiuser channels on one slot (VAMOS) standard, a recent evolution of both GSM and enhanced data rates for GSM evolution (EDGE) standards, to mitigate legacy GSM CCI in particular. It is also required for filter bank multicarrier offset quadrature amplitude modulation (FBMC-OQAM) networks, which are candidate for 5G mobile networks, to mitigate intercarrier interference at reception for frequency selective propagation channels in particular. In this context, the purpose of this paper is twofold. The first one is to get more insights into the existing SAIC technology, and its extension to multiple antenna called multiple antenna interference cancellation (MAIC), by showing analytically that, contrary to what is accepted as true in the literature, SAIC/MAIC implemented from standard WL filtering may be less efficient for QR signals than for R ones. From this result, the second purpose of the paper is to propose and to analyze, forQRsignals and frequency selective fading channels, an SAIC/MAIC enhancement based on a three-input WL frequency shift receiver, making QR signals always almost equivalent to R ones for WL filtering in the presence of CCI. The results of the paper, completely new, may contribute to develop elsewhere new powerful WL receivers for QR signals and for both VAMOS and FBMC-OQAM networks in particular. [ABSTRACT FROM AUTHOR]

Between 2007 and 2013, the European Rural Development Policy targets were supported by the LEADER policy, an instrument that can be interpreted differently according to each country. Based on the examples of France and Lithuania, we studied the way in which the institutional organization of the device at local level helps to understand the stakeholders system and how adaptable it is to situations in each of the corresponding countries and project areas. A comparative approach, based on a joint methodology of investigation and analysis, was used on four project areas: Joniškis and Ignalina in Lithuania, and Gévaudan-Lozère and Pays Coeur d'Hérault in France. It shows that, in all cases, a form of "municipalization" of the LEADER programme, or at least a strong integration of the association sector, is dominant and seems to be established. Studying the network of stakeholders helps to identify the interknowledge as well as the interdependency relationships that lie at the heart of the system. The development of the "social capital of individuals" is often an entry point, if not a cornerstone, of the stakeholders system in place. Finally, it is through the analysis of the project selection process that we can truly grasp the characteristics of the new public action mode, in particular by studying the allocation of projects in these local areas. [ABSTRACT FROM AUTHOR]

Fourth-order (FO) high resolution direction finding methods such as 4-MUSIC have been developed for more than two decades for non-Gaussian sources mainly to overcome the limitations of second order (SO) high resolution methods such as MUSIC. In order to increase the performance of 4-MUSIC in the context of multiple sources, the MUSIC method has recently been extended to an arbitrary even order 2 q ( q ≥ 2 ), for square arrangements of the 2 q th-order data statistics, giving rise to the 2 q -MUSIC algorithm. To further improve the performance of 2 q -MUSIC, the purpose of this paper is to extend the latter to rectangular arrangements of the data statistics, giving rise to rectangular 2 q -MUSIC algorithms. Two kinds of rectangular arrangements, corresponding to redundant and non-redundant arrangements are considered. In particular, it is shown that rectangular arrangements of the higher order (HO) data statistics achieve a trade-off between performance and maximal number of sources to be estimated. These rectangular arrangements also lead to a complexity reduction for a given level of performance, which is still increased by non-redundant arrangements of the statistics. These results, completely new, open new perspectives in HO array processing. [ABSTRACT FROM AUTHOR]

Between 2007 and 2013, the aims of the European Policy for Rural Development have benefited from the LEADER policy instrument that can be differently interpreted depending on countries. From two case studies, France and Lithuania, we analyze how the institutional organization of the device at local level allows understanding the system of actors and how it fits to the situations of each country and the corresponding project territories. A comparative approach based on a common survey and analysis methodology was carried out on four project territories, Joniškis and Ignalina in Lithuania, and Gėvaudan-Lozere and Pays Creur-d'Hėrault in France. It shows that, in all cases, a form of “municipalization” of the LEADER program, or at least a strong integration of the associative sector, prevails and seems to be achieved. Analyzing the network of actors allows identifying the relations in terms of mutual acquaintance but also of interdependence within the system. The formation of the “social capital of individuals” is often an input key, and even a keystone of the system of actors in place. Last, the review of the project selection process leads to a real understanding of the features of the new public action mode by analyzing the distribution of projects in these same local territories. [ABSTRACT FROM AUTHOR]

This article will address the receipt procedures of the European local development program, LEADER, in France and Lithuania. We will use an empirical approach to focus on groups of actors who have supported, at local level, the LEADER device. Formally, these local action groups (LAGs) proceed in the creation of networking partnerships. These engage local stakeholders in a collective approach by interdependence links, more or less complex and more or less intense. These links are the basis for a local action system which reexamines the organization of the local area. From the study of the configuration of local partnerships in the LAGs of Gevaudan-Lozère (France) and Joniškis (Lithuania), the research asks about the transformation at local level of the public action mode in two different national contexts. Priority is given to the monographic study, the analysis of the composition of actors' networks in charge of local development, then the nature of linkages between individuals of these networks. This article will help to understand how local action systems face the interplay between national logics of institutional transfer and local context effects. [ABSTRACT FROM AUTHOR]

Abstract: Widely Linear (WL) Minimum Mean Square Error (MMSE) estimation has received a great interest these last 20 years for second order (SO) noncircular signals. In the context of radio communications networks, it has been shown in particular that WL MMSE receivers allow to implement Single Antenna Interference Cancellation (SAIC) of one rectilinear interference, such as Binary Phase Shift Keying (BPSK) or Amplitude Shift Keying (ASK) interference, or of quasi-rectilinear interference, such as Minimum Shift keying (MSK), Gaussian MSK (GMSK) or Offset Quadrature Amplitude Modulation (OQAM) interference, hence their great interest for Global System for Mobile Communications (GSM) cellular networks in particular. However, one may wonder whether WL MMSE receivers remain attractive for SO noncircular nonrectilinear interferences, not so scarce in practice. The purpose of this paper is mainly to answer to this important question by giving, in a self-contained and unified way, some new insights into the behavior, properties and performance of the WL MMSE beamformer in the presence of arbitrary noncircular signals and interference which are not necessarily rectilinear. It is shown in particular that, surprisingly, WL MMSE receivers lose their practical interest for strong interferences which are not rectilinear. This breakthrough thus generates a new open problem for the choice between linear and WL MMSE receiver corresponding to the detection of rectilinearity (and/or quasi-rectilinearity), instead of noncircularity, in a given noisy observation. Although this question is out of the scope of this paper, we finally propose preliminary tools based on blind source separation methods to solve this problem. [Copyright &y& Elsevier]

Power amplifier (PA) design for 160-GHz applications in an advanced SiGe heterojunction bipolar transistor (HBT) technology with saturated output power (Psat) in excess of 10 dBm is presented. The architecture is based on a three-stage pseudodifferential configuration that was implemented in SiGe HBT evaluation technology with f\max of 400 GHz. At saturation, a PA breakout circuit delivers 10 dBm with 20-dB gain. From 150 to 170 GHz, the small-signal gain is within 20–32 dB and the output referred 1-dB compression point (P1\ dB) is 8.5 dBm at 160 GHz. High output power was possible due to optimum device sizing, efficient layout, and accurate EM modeling. To our best knowledge, this is the highest output power reported for silicon PAs operating beyond 120 GHz. [ABSTRACT FROM AUTHOR]

The LEADER Program, introduced in 1991 as part of EU rural development policy, is a mainstay for local action in Europe. Based on local partnerships bringing together entrepreneurs, elected representatives and associations on a voluntary basis, it exemplifies the principles of cooperation and subsidiarity, and thus helps strengthen local democracy. Researchers and development practitioners agree on its innovativeness and potential for "transferability", since each member state enjoys a degree of freedom in applying it. Not only may each EU country arrange the program's objectives in line with its own priorities, it also has wide room for using the financial means granted to it and determining how to implement the program. This article focuses on the conditions for transferring the Leader approach (2007-2013) to all 27 EU member states. How have the latter interpreted and transposed this European model? Do the regulations for forming "project territories" and thawing up local development strategies lead to practices in compliance with the view that the EU is trying to promote? [ABSTRACT FROM AUTHOR]

An introduction to the issue is presented which discusses the implementation of the European Union's Leader program for rural development, its implications for local government in post-communist member states, and how it fosters the latter's "bottom-up" Europeanization and democratization.

The transfer of the local development model in the framework of the Common Agricultural Policy (2007-20 13) implies learning a new form of public action based on initiatives borne by local stakeholders. One of the objectives of the LEADER Program is to improve the governance of rural areas through a bottom-up approach to local development. Are the conditions for carrying it out it in each country's institutional context capable of boosting citizen participation in collective actions and consolidating local democracy? Defined and formulated at the EU level, the Leader approach has been transposed by member states in different ways and incorporated in each country's system of local government in line with political strategies for establishing "action areas" that differ in their territorial coverage and articulation with institutional units. Empirical research sheds light on how local action groups have been shaped through the formation of partnerships and networks. The positions adopted by a few mayors on the local scene provide evidence of the emergence of a genuine political leadership. [ABSTRACT FROM AUTHOR]

Noise parameter (F\min, Zopt, and R n) measurements of SiGe HBTs are provided for the first time in the 70–170-GHz range. In the W-band, this is accomplished by integrating on a single chip a source impedance tuner with the device-under-test and a low-noise amplifier with 3.8-dB noise figure. Noise-figure measurements were performed over multiple source impedances using a commercial single-sideband downconverter. In the D-band, where off-chip setup losses are overwhelming, the source impedance tuner, the transistor under test, and the entire receiver with a noise figure of 10 dB were integrated on a single silicon die, and direct noise-figure measurements were conducted first on the test setup with the transistor under test, and next on the reference receiver without the test transistor. Both analog and digital source impedance tuners, based on n-MOSFET variable resistors, n-MOSFET switches, and accumulation-mode varactors, have been designed and characterized. Finally, the existing technique to extract the SiGe HBT noise parameters from Y-parameter measurements, without any noise-figure measurements, is refined to include noise correlation and is validated up to 170 GHz. The measured source–pull and Y-parameters results show that the minimum noise figure of state-of-the-art SiGe HBTs remains below 5 dB throughout the D-band. [ABSTRACT FROM AUTHOR]

Orthogonal space-time block codes (STBC), and the Alamouti scheme in particular, are of particular interest in multiple-input multiple-output (MIMO) systems since they achieve full spatial diversity over fading channels and are decoded from linear processing at the receiver. Nevertheless, due to the expensive spectral resource, increasing network capacity requires the development of interference cancellation (IC) techniques allowing several users to share the same spectral resources without impacting the transmission quality. In this context several IC schemes have been developed during this last decade, where each user is equipped with multiple antennas and employs STBC at transmission. However, these IC techniques require multiple antennas at reception, which remains a challenge at the handset level due to cost and size limitations. For this reason, low complexity single antenna interference cancellation (SAIC) techniques, currently operational in GSM handsets, have been developed recently for single antenna users using real-valued modulations or complex filtering of real-valued modulations, by using a widely linear (WL) filtering at reception. Extension to multiple antennas at reception is called multiple antenna interference cancellation (MAIC) technique. The purpose of this paper is to extend the SAIC/MAIC technology to users using both real-valued constellations, such as amplitude shift keying (ASK) constellations, and the Alamouti scheme at transmission. A WL minimum mean square error (MMSE) receiver, completely new for IC purposes in the context of radio communications systems using the Alamouti scheme, is proposed and analyzed. This receiver, which corresponds to the maximum likelihood (ML) receiver for synchronous intranetwork interferences, is able to separate up to 2 N Alamouti users from N antennas at reception, hence SAIC capability for N = 1. [ABSTRACT FROM PUBLISHER]

Problems related to "trajectories of evolution" lie at the center of the analysis of economic transformations in the Czech Republic since the early 1990s. Given the major political breakthrough represented by 1989 and membership in the EU in 2004, rural society in the Czech Republic has responded in a variety of ways to the new requirements made by the marketplace and by EU directives in economic matters. Deep social and cultural changes, partly legitimated by national or EU projects and policies, have modified how Czech rural areas are used (residence, leisure activities or tourism depending on the place) and how society views these areas. This diversification of economic activities in the countryside has not affected all places in like manner. Some have switched to being residential or touristic zones, while others have retained (or even reinforced) farming or industrial activities. These changes in economic activities and their distribution in rural areas are analyzed in terms of a global/local dialectics at the scale of the whole country. How do rural activities and territorial dynamics fit together in quite differentiated geographical settings? [ABSTRACT FROM AUTHOR]

• We extend, for R and QR data-like MUI and arbitrary propagation channels, the standard two-input SAIC/MAIC WL receivers to data-like MUI with an arbitrary non-zero residual FO, showing that SAIC/MAIC remains possible in this case. • We prove that for a data-like MUI having a non-zero residual frequency offset and spectrally overlapping with the SOI, the extended two-input SAIC/MAIC WL receiver is less efficient for QR signals than for R ones. • We extend, for QR data-like MUI and arbitrary propagation channels, the enhanced three-input SAIC/MAIC WL receiver aleady introduced to data-like MUI with a non-zero residual residual frequency offset, allowing a SAIC/MAIC improvement with respect to the extended two-input SAIC/MAIC WL receivers. • We analyze, both analytically and by simulations, for both R and QR data-like MUI, the impact of the non-zero MUI residual frequency offset on the performance of the proposed extended two and three-input WL FRESH receivers. Widely linear (WL) receivers have been developed in the past for single antenna interference cancellation (SAIC) of one rectilinear (R) or quasi-rectilinear (QR) data-like multi-user interference (MUI) or co-channel interference (CCI) in particular. The SAIC technology has been implemented in global system for mobile communications (GSM) handsets in particular and has been further analyzed for voice services over adaptive multi-user channels on one slot (VAMOS) standard. It remains of great interest for several current and future applications using R or QR signals, such as anti-collisions processing in radio frequency identification (RFID) or in satellite-AIS systems and to densify 5G and Beyond 5G (B5G) networks through one dimensional signaling or over-loaded large MU-MIMO systems. It may be required to cancel the inter-symbol interference (ISI) of control and non-payload communications (CNPC) links of unmanned aerial vehicles (UAV) and the inter-carrier interference (ICI) of filter bank multi-carrier offset quadrature amplitude modulation (FBMC-OQAM), which are now candidate for B5G mobile networks. For these challenging applications, the development of enhanced WL filtering based SAIC or Multiple Antenna Interference Cancellation (MAIC) receivers for R and QR signals may be of great interest. Such a receiver, corresponding to a three-input WL frequency shift (FRESH) receiver, has been introduced recently for QR signals. However this WL receiver is not robust to a data-like MUI having a residual frequency offset (FO), which occurs for most of the previous applications. In this context, the paper first extends, for arbitrary propagation channels, the standards (for R and QR MUI) and the enhanced (for QR MUI) SAIC/MAIC WL receivers to MUI with a non-zero FO. Then, it shows the less efficiency of the two-input WL receiver for QR MUI with a non-zero FO and the performance improvement obtained with the three-input WL receiver. Finally, it analyzes, both analytically and by simulations, for R and QR MUI, the impact of the MUI FO on the performance of the proposed receivers. The results of the paper should allow the development of new powerful WL receivers for UAV CNPC links, anti-collisions AIS systems and for FBMC-OQAM networks in particular. [ABSTRACT FROM AUTHOR]

Fourth-order (FO) and, a short while ago, 2qth-order, q ≥ 2, high-resolution methods exploiting the information con- tained in the FO and the 2qth-order, q ≥ 2, statistics of the data, respectively, are now available for direction finding of non-Gaussian signals. Among these methods, the 2q-MUSIC methods, q ≥ 2, are the most popular. These methods are asymptotically robust to a Gaussian background noise whose spatial coherence is unknown and offer increasing resolution and robustness to modeling errors jointly with an increasing processing capacity as q increases. However, these methods have been mainly developed for arrays with identical sensors only and cannot put up with arrays of diversely polarized sensors in the presence of diversely polarized sources. In this context, the purpose of this paper is to introduce, for arbitrary values of q, q ≥ 1, three extensions of the 2q-MUSIC method, able to put up with arrays having diversely polarized sensors for diversely polarized sources. This gives rise to the so-called polarization diversity 2q-MUSIC (PD-2q-MUSIC) algorithms. For a given value of q, these algorithms are shown to increase the resolution, the robustness to modeling errors, and the processing capacity of the 2q-MUSIC method in the presence of diversely polarized sources. Besides, some PD-2q-MUSIC algorithms are shown to offer increasing performances with q when resolution in both direction of arrival and polarization is required. [ABSTRACT FROM AUTHOR]

For nonstationary observations, potentially second-order (SO) noncircular, the SO optimal complex filters are time variant (TV) and, under some conditions of noncircularity, widely linear (WL). Moreover, for applications such as spectrum monitoring or passive listening, the sources' waveforms are unknown and no training sequence or spreading code is a priori available. In this context, this paper aims at introducing the time invariant (TI) WL minimum variance distortionless response (MVDR) beamformer for the optimal reception of an unknown signal, whose waveform is unknown but whose steering vector is known, corrupted by potentially noncircular interferences. Its properties, performance, and adaptive implementation in noncircular contexts are analyzed in this paper. This optimal beamformer is shown to always improve, in the steady state, the performance of the well-known Capon's beamformer for noncircular interferences. Moreover, it should be noticed that this optimal beamformer allows the processing of up to 2 (N 1) rectilinear interferences from an array of N sensors. Finally, at the end of this paper, a TV extension of this TI WL MVDR beamformer is presented to process SO noncircular interferences having a nonnull carrier residue or frequency offset. [ABSTRACT FROM AUTHOR]

From the beginning of the 1980s, many second-order (SO) high-resolution direction-finding methods, such as the MUSIC method (or 2-MUSIC), have been developed mainly to process efficiently the multisource environments. Despite of their great interests, these methods suffer from serious drawbacks such as a weak robustness to both modeling errors and the presence of a strong colored background noise whose spatial coherence is unknown, poor performance in the presence of several poorly angularly separated sources from a limited duration observation and a maximum of N - 1 sources to be processed from an array of N sensors. Mainly to overcome these limitations and in particular to increase both the resolution and the number of sources to be processed from an array of N sensors, fourth-order (FO) high-resolution direction-finding methods have been developed, from the end of the 1980s, to process non-Gaussian sources, omnipresent in radio communications, among which the 4-MUSIC method is the most popular. To increase even more the resolution, the robustness to modeling errors, and the number of sources to be processed from a given array of sensors, and thus to minimize the number of sensors in operational contexts, we propose in this paper an extension of the MUSIC method to an arbitrary even order 2q (q ≥ 1), giving rise to the 2q-MUSIC methods. The performance analysis of these new methods show off new important results for direction-finding applications and in particular the best performances, with respect to 2-MUSIC and 4-MUSIC, of 2q-MUSIC methods with q > 2, despite their higher variance, when some resolution is required. [ABSTRACT FROM AUTHOR]

For nonstationary observations, potentially second-order (SO) noncircular, the SO optimal complex filters are time variant and, under some conditions of noncircularity, widely linear (WL). For more than a decade, there has been an increasing interest in optimal WL filters in radiocommunications contexts involving rectilinear signals such as binary phase-shift keying (BPSK) signals. In particular, it has been pointed out that single antenna interference cancellation (SAIC) may be performed by such filters in the context of BPSK cellular networks. Recently, it has been shown that, by a simple algebraic operation of demodulation on the baseband signal, the minimum shift keying (MSK) and Gaussian MSK (GMSK) modulations can be made to approximately correspond to a BPSK modulation, allowing the application of the SAIC concept to the GSM cellular network at the mobile level, being currently studied for standardization, and offering significant improvements of the network's capacity. Despite the increasing interest in optimal WL filters in rectilinear or quasi-rectilinear contexts, many questions about their behavior and their performance have still arisen. The purpose of this paper is to gain insight into the behavior, properties, and performance of optimal WL array receivers, and thus of the SAIC technology, for the demodulation of BPSK, MSK, and GMSK signals corrupted by noncircular interferences. [ABSTRACT FROM AUTHOR]

For about two decades, many fourth order (FO) array processing methods have been developed for both direction finding and blind identification of non-Gaussian signals. One of the main interests in using FO cumulants only instead of second-order (SO) ones in array processing applications relies on the increase of both the effective aperture and the number of sensors of the considered array, which eventually introduces the FO Vitual Array concept presented elsewhere and allows, in particular, a better resolution and the processing of more sources than sensors. To still increase the resolution and the number of sources to be processed from a given array of sensors, new families of blind identification, source separation, and direction finding methods, at an order m = 2q (q ⩾ 2) only, have been developed recently. In this context, the purpose of this paper is to provide some important insights into the mechanisms and, more particularly, to both the resolution and the maximal processing capacity, of numerous 2qth order array processing methods, whose previous methods are part of, by extending the Virtual Array concept to an arbitrary even order for several arrangements of the data statistics and for arrays with space, angular and/or polarization diversity. [ABSTRACT FROM AUTHOR]

Most of the second-order (SO) and higher order (HO) blind source separation (BSS) methods developed this last decade aim at blindly separating statistically independent sources that are assumed zero-mean, stationary, and ergodic. Nevertheless, in many situations of practical interest, such as in radiocommunications contexts, the sources are nonstationary and very often cyclostationary (digital modulations). The behavior of the current SO and fourth-order (FO) cumulant-based BSS methods in the presence of cyclostationary sources has been analyzed, recently, in a previous paper by Ferréol and Chevalier, assuming zero-mean sources. However, some cyclostationary sources used in practical situations are not zero-mean but have a first-order (FIO) cyclostationarity property, which is, in particular, the case for some amplitude modulated (AM) signals and for some nonlinearly modulated digital sources such as frequency shift keying (FSK) or some continuous phase frequency shift keying (CPFSK) sources. For such sources, the results presented in the previous paper by Ferréol and Chevalier no longer hold, and the purpose of this paper is to analyze the behavior and to propose adaptations of the current SO BSS methods for sources that are both FIO and SO cyclostationary and cycloergodic. An extension for deterministic sources is also proposed in the paper. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the behavior of current second and higher order blind source separation methods for cyclostationary sources. Blind source separation in cyclostationary context; Behavior analysis of the empirical estimators in cyclostationary contexts; Application in radiocommunications context; Computer simulations; Conclusions.

Deals with a study which presented the virtual array (VA) concept by an alternative way that is easier and more direct to handle than that using the virtual cross-correlation tool. Hypothesis of the study; Concept of the VA; Examples of VA; Conclusion.

Calculates the optimum linear-quadratic array receiver in a non-Gaussian environment by using the deflection criterion and evaluate some of its performance. Statement of the problem; Optimal performance in a spatially fourth-order white noise; Gain in deflection; Conclusion.

• A closed-form expression of the SINR at the output of a family of third-order Volterra MVDR beamformers is given. • Interpretable closed-form expressions of this SINR are derived in the particular case of 2 sensors in the presence of single digitally linearly modulated interference. • These closed-form expression allow us to quantify the impact of the pulse-shape filtering (pulse shape filter, oversampling factor and initial sampling time). • This sensitivity study proves that the high performance gain of these third-order Volterra MVDR beamformers with respect to the Capon algorithm for a square pulse shape filter are lost in the presence of intersymbol interference. Linear beamformers are optimal, in a mean square (MS) sense, when the signal of interest (SOI) and observations are jointly Gaussian and circular. Otherwise, optimal beamformers become non-linear with a structure depending on the unknown joint probability distribution of the SOI and observations. In this context, third-order Volterra minimum variance distortionless response (MVDR) beamformers have been proposed recently to improve the performance of linear beamformers in the presence of non-Gaussian and potentially non-circular interference, omnipresent in practical situations. High performance gains have been obtained for binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) interference having a square pulse shaping filter in particular. However in practice, for spectral efficiency reasons, most of signals use non-square pulse shaping filters, such as square root raised cosine filter. It is then important to analyze the sensitivity of third-order MVDR beamformers to interference pulse shaping filter, which is the purpose of this paper. [ABSTRACT FROM AUTHOR]

This paper proposes unprecedented Expectation Propagation (EP)-based receivers for Circular Faster-Than-Nyquist (CFTN) signaling. This concept yields a Minimum Mean-Square-Error equalizer for InterSymbol Interference (ISI) processing combined with a block which we call Constellation Matcher in charge of the symbol estimates realignment with the constellation. From this framework, we explore different scheduling strategies leading to iterative EP-based receivers with our without decision feedback. Then, by extending the family of the EP process to a subset of non-circular Gaussian distributions results in a Widely Linear (WL) equalization. This new WL-EP receiver best fits the CFTN model, allowing enhanced performance at the cost of a slightly increased complexity. Also, we propose to restrict the Gaussian family to circular Gaussian distributions with identity covariance matrices up to a scaling factor. Combined with CFTN, this particular family allows a low-complexity Frequency-Domain processing of the equalization without requiring any cyclic prefix. The proposed EP-based receivers for CFTN are then evaluated for different spectral efficiencies and computational complexities. Our simulations show that they completely handle the ISI up to 5 bits/s/Hz and double the spectral efficiency compared to Nyquist signaling with almost no performance loss. [ABSTRACT FROM AUTHOR]

In this article, the electrical model of a millimeter-wave (mmW), silicon-based noise source is developed in the frequency range up to 325 GHz. The model is studied as a function of the biasing current and the structure size. The noise source is based on a Schottky diode realized on the 55-nm SiGe BiCMOS technology from STMicroelectronics, Crolles, France. Due to the ability of being integrated on silicon, this noise source can be used for high-frequency in situ noise characterization of advanced silicon CMOS or bipolar technologies in the mmW range. In previous study, the diode was used as a noise source when biased near the avalanche regime, and an excess noise ratio (ENR) up to 20 dB has been achieved in a frequency range up to 260 GHz. In this article, the ENR value of the diode is retrieved from the electrical model and compared to the value extracted by measurements. The extracted ENR value was also studied for several diode sizes and biasing currents and measured up to 325 GHz, with a good agreement with the modeling. [ABSTRACT FROM AUTHOR]

This paper addresses the behavior of a classical multiantenna GLRT test that allows to detect the presence of a known signal corrupted by a multipath propagation channel and by an additive temporally white Gaussian noise with unknown spatial covariance matrix. The paper is focused on the case where the number of sensors M is large, and of the same order of magnitude as the sample size N, a context which is modeled by the large system asymptotic regime M \rightarrow +\infty , N \rightarrow +\infty in such a way that M/N \rightarrow c for c \in (0,+\infty ). The purpose of this paper is to study the behaviour of a GLRT statistics in this regime, and to show that the corresponding theoretical analysis allows to accurately predict the performance of the test when M and N are of the same order of magnitude. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, the problem of testing impropriety (i.e., second-order noncircularity) of a sequence of complex-valued random variables (RVs) based on the generalized likelihood ratio test (GLRT) for Gaussian distributions is considered. Asymptotic (w.r.t. the data length) distributions of the GLR are given under the hypothesis that RVs are proper or improper, and under the true, not necessarily Gaussian distribution of the RVs. The considered RVs are independent but not necessarily identically distributed: assumption which has never been considered until now. This enables us to deal with the practical important situations of noncircular RVs disturbed by residual frequency offsets and additive circular noise. The receiver operating characteristic (ROC) of this test is derived as byproduct, an issue previously overlooked. Finally illustrative examples are presented in order to strengthen the obtained theoretical results. [Copyright &y& Elsevier]

Abstract: A performance analysis of likelihood ratio test (LRT)-based and generalized likelihood ratio test (GLRT)-based array receivers for the detection of a known real-valued signal corrupted by a potentially noncircular interference is considered in this paper. The distribution of the decision statistics associated with the LRT and GLRT is studied. This allows us to give exact closed-form expressions of the probability of detection (P D) and false alarm (P FA) for two LRT-based receivers. Then, asymptotic (with respect to the data length) closed-form expressions are given for P D and P FA for four GLRT-based receivers. Finally, in order to strengthen the obtained results, some illustrative examples are presented. [Copyright &y& Elsevier]

The classical higher order MUSIC-like methods based on a simultaneous search for all directions of arrival (DOA's) show: i) a capacity for processing underdetermined mixtures of sources; ii) a high robustness with respect to both a Gaussian noise with unknown spatial coherence and modeling errors; and iii) a better resolution than algorithms based on second order statistics. However, these methods have some limits: for a finite number of samples, they show poor performance for sources exhibiting quasi-colinear DOA's. In order to overcome this drawback, two new sequential MUSIC-like algorithms are proposed in this paper, namely the 2q-D-MUSIC and the 2q-RAP-MUSIC (q ≥ 2) algorithms. These methods are based on a sequential optimization of proposed generalized noise and signal 2q-MUSIC metrics, respectively. That allows us to learn and then to take into account the level of correlation between sources. A comparative study, both in terms of performance and numerical complexity, is performed showing the interest of the proposed techniques when some sources are angularly close. Eventually, an upper bound of the maximum number of sources which can be processed by the 2q-MUSIC-like techniques is given for all q. This improves recent work on the 2qth-order virtual arrays. [ABSTRACT FROM AUTHOR]

A growing interest has been focused on silicon-on-insulator (SO!) technologies over the past years. Yet, few studies were carried out regarding the integration of vertical SiGe heterojunction bipolar transistors (HBTs) using such substrates: This paper deals both with the integration of a SiGeC HBT on thin-film CMOS-compatible SO!, and a comprehensive study of its electrical behavior based on physical simulation and electrical characterization. Various aspects of the optimization of device performances are described, considering process or layout improvements. [ABSTRACT FROM AUTHOR]

The problem of blind separation of overdetermined mixtures of sources, that is, with fewer sources than (or as many sources as) sensors, is addressed in this paper. A new method, called Independent Component Analysis using Redundancies in the quadricovariance (ICAR), is proposed in order to process complex data. This method, without any whitening operation, only exploits some redundancies of a particular quadricovariance matrix of the data. Computer simulations demonstrate that ICAR offers in general good results and even outperforms classical methods in several situations: ICAR i) succeeds in separating sources with low signal-to-noise ratios, ii) does not require sources with different second-order or/and first-order spectral densities, iii) is asymptotically not affected by the presence of a Gaussian noise with unknown spatial correlation, iv) is not sensitive to an over estimation of the number of sources. [ABSTRACT FROM AUTHOR]

For about two decades, numerous methods have been developed to blindly identify overdetermined (P ≤ N) mixtures of P statistically independent narrowband (NB) sources received by an array of N sensors. These methods exploit the information contained in the second-order (SO), the fourth-order (FO) or both the SO and FO statistics of the data. However, in practical situations, the probability of receiving more sources than sensors increases with the reception bandwidth and the use of blind identification (BI) methods able to process underdetermined mixtures of sources, for which P > N may be required. Although such methods have been developed over the past few years, they all present serious limitations in practical situations related to the radiocommunications context. For this reason, the purpose of this paper is to propose a new attractive BI method, exploiting the information contained in the FO data statistics only, that is able to process underdetermined mixtures of sources without the main limitations of the existing methods, provided that the sources have different trispectrum and nonzero kurtosis with the same sign. A new performance criterion that is able to quantify the identification quality of a given source and allowing the quantitative comparison of two BI methods for each source, is also proposed in the paper. Finally, an application of the proposed method is presented through the introduction of a powerful direction-finding method built from the blindly identified mixture matrix. [ABSTRACT FROM AUTHOR]

Presents a study which addressed the problem of estimating the second-order statistics of a frequency-selective Rayleigh channel. Problem statement and signal model; Estimation of the channel covariance matrix; Improvement of channel estimation using the channel covariance matrix.

A new method to induce tensile stress in a PDSOI NMOS device for RF applications is proposed, which is based on relaxing a SiGe layer built underneath silicon. By means of TCAD simulations, we demonstrate that stress transfer from SiGe to Si occurs by means of at least two different mechanisms: SiGe relaxation due to amorphization and the formation of Stacking Faults during recrystallization. By considering both phenomena, a tensile stress of 0.5 GPa can be injected into the silicon channel. Moreover, the impact of annealing steps on the detrimental out-of-SiGe Ge diffusion has been simulated by considering an inter-diffusion model, showing the importance of adapting the PDSOI process flow to account for the presence of the new stressor. [ABSTRACT FROM AUTHOR]

The system and transistor-level design of low-power millimeter wave (mm-wave) active tags in silicon is discussed in detail. Two active mm-wave tags with identical system architecture, padframe, and chip size were designed and fabricated in 55-nm SiGe BiCMOS and 45-nm SOI CMOS technologies, respectively. They feature a three-stage low-noise amplifier (LNA), a wake-up detector, a BPSK modulator, and two variable gain output stages, each driving a separate transmit antenna in antiphase. The wake-up detector can be used to switch OFF all the blocks except for the LNA and detector, thus further reducing power consumption. The measured performance of the SiGe and SOI chips is remarkably similar: 19- and 20-dB gain, 9- and 8-dB noise figure, and 25-/10.8-mW (active/idle) and 18-mW power consumption, respectively. The SiGe tag was flip-chip-mounted on a mini-PCB with one receive and two transmit antennas for system level functionality tests carried out over a distance of 5 m. The SiGe-tag wake-up sensitivity was verified to be −62 dBm, in excellent agreement with simulation results. [ABSTRACT FROM PUBLISHER]

Two types of industrial transistor technologies have been studied using atom probe tomography (APT). Both 14 nm node high-K metal-oxide-semiconductor field effect transistors (MOSFETs) on ultrathin body and buried oxide and 320 GHz Ft Si/SiGe Heterojunction Bipolar Transistors (HBT) embedded in a 55-nm BiCMOS chip have been analysed and their atomic distribution has been mapped. Due to the limitations of routine characterisation techniques, boron can remain invisible in such nanometric sized structures. Also, size effects can induce differences between the actual device and larger test zones used for monitoring these technologies. This paper presents results obtained by APT from two advanced nodes, in contrast to complementary techniques. Using different methodologies, including specific APT-friendly test structures and multiple-impact data filtering, the dopant behaviour in these structures can be better understood. An unexpected boron distribution in both the MOSFET source/drain and HBT base regions has been highlighted. [ABSTRACT FROM AUTHOR]

This paper presents a small-signal characterization work on a recently developed 55 nm SiGe BiCMOS technology from STMicroelectronics. The SiGe HBT from a prototype BiCMOS 55 nm process was investigated up to 325 GHz. The full S-parameters from DC to 325 GHz under multiple bias conditions are presented for the first time for a SiGe HBT. A usual and simple approach for the off-wafer calibration associated to an on-wafer de-embedding procedure was used and remained valid up to 325 GHz thanks to a size reduction of the test structures. The extracted 300/325 GHz f T /f MAX couple, reached at 14 mA/μm 2 collector density and 1.2 V collector-emitter voltage, was validated up to 325 GHz. [ABSTRACT FROM AUTHOR]

Optimization of Heterojunction Bipolar Transistors is crucial for improving RF capabilities of modern BiCMOS technologies. Fully-implanted collectors are meant to reduce fabrication complexity and Super Shallow Trench Isolation (SSTI) structures are used to reduce the consequent high base–collector capacitance. Ion implantation can induce lattice defects in silicon and carbon plus phosphorus co-implantation helps reducing them, even if it cannot avoid formation of dislocations generated by bad recrystallization of the implantation-induced amorphous silicon layer. Defects within the device are known to impact functionality and must be avoided. Understanding of the interaction between implantation-induced amorphization and substrate stress due to isolation structures is required for ensuring a reliable integration. Amorphous layer positioning with respect to substrate surface is investigated as the main defect-generation mechanism. Incomplete surface amorphization is shown to induce multiple types of dislocations affecting device functionality. Total surface amorphization ensures almost ideal current characteristics. Silicon clusters appear at high phosphorus/carbon ratios with no impact on functionality. Stress induced by isolation structures is not responsible for dislocations generation but modulates speed of the recrystallization fronts, impacting defects placement. [Display omitted] • Defects can form in substrates doped with amorphizing ion-implantation. • Degree of surface amorphization influences defect formation during Solid Phase Epitaxial Regrowth. • Stress induced by isolation trenches modulates recrystallization speed an therefore defects formation. • Device functionality is impacted by defects within junctions. • Total surface amorphization avoids any recrystallization-induced defect. [ABSTRACT FROM AUTHOR]

This paper investigates alternative topologies of silicon germanium heterojunction bipolar transistors designed and fabricated in the state-of-the-art BiCMOS process from STMicroelectronics for improved safe-operating characteristics. Electrical and thermal behaviors of various structures are analyzed and compared, along with a detailed discussion on drawbacks and advantages. The test structures under study are different in terms of emitter-finger layouts as well as the metal stacks in the back-end-of-line. It is observed that the multifinger transistor structures having nonuniform finger lengths with wider area enclosed by the deep trench and higher metallization stacks yield an improved thermal behavior. Therefore, the safe-operating area of multifinger transistors can be extended without degrading the RF performances. [ABSTRACT FROM PUBLISHER]

This paper describes a methodology for extracting and verifying the high-frequency model parameters of the HICUM L0 and L2 models of a silicon–germanium HBT from device and circuit measurements in the 110–325-GHz range. For the first time, the non-quasi-static effects, missing in the HICUM/L0 model, are found to be essential in accurately capturing the frequency dependence of the transistor maximum available power gain beyond the inflection frequency for unconditional stability. Furthermore, it is demonstrated that the optimal partitioning of the area and periphery components of the junction base–emitter, base–collector, and collector–substrate capacitances, and of the internal and external base and collector resistances can only be determined from S-parameter measurements beyond 200 GHz. The extracted models are validated on state-of-the-art linear and nonlinear circuits (amplifier, voltage-controlled oscillator (VCO), and VCO + divider chain) operating at frequencies as high as 240 GHz. [ABSTRACT FROM AUTHOR]

A D-band SiGe HBT total power radiometer is reported with a peak responsivity of 28 MV/W, a noise equivalent power (NEP) of 14–18 \fW/Hz^1/2, and a temperature resolution better than 0.35 K for an integration time of 3.125 ms. The 1/f noise corner of the radiometer is lower than 200 Hz. Fabricated in a developmental technology with 270-GHz fT and 330-GHz fMAX, it includes a five-stage low-noise amplifier (LNA) with 4–7-GHz bandwidth and over 35 dB of gain centered at 165 GHz, along with a square-law detector with an NEP below 6 \pW/Hz^1/2 up to 170 GHz. An average system noise temperature of 1645 K is obtained using the Y-factor method and a noise bandwidth of 10 GHz calculated from the measured S21(f) characteristics of the radiometer. The reduced 1/f noise corner frequency in the presence of the amplifier, compared to that of the detector, appears to indicate that, unlike in III–V radiometers, LNA gain fluctuations are not a problem in SiGe HBT radiometers. The circuit consumes 95 mW and occupies \ 765\,\times\ 490∼\mu\ m^2. Wafer mapping of the radiometer sensitivity and of the amplifier gain was performed across different process splits. The mapping results demonstrate that the radiometer can be employed as a relatively simple and area-efficient transistor noise-measure monitor, useful in SiGe HBT vertical profile optimization. [ABSTRACT FROM AUTHOR]

The overall purpose of this paper (including Part I, in this issue) is the prediction of the ultimate electrical high-frequency performance potential for SiGeC heterojunction bipolar transistors under the constraints of practical applications. This goal is achieved by utilizing most advanced device simulation tools with parameters calibrated to existing experimental results. This Part I outlines the overall scaling procedure and then focuses on the vertically scaled structure. According to isothermal device simulation, the “ultimate” doping profile yields a peak transit frequency fT of almost 1.5 THz, a \BVCEO above 1 V (dependent on BE bias) and a zero-bias internal base sheet resistance of about 3 \k\Omega/\sq. The reasons for achieving a higher product fT \BV \rm CEO ( > \1.5\ \THzV) than anticipated from the classical Johnson limit are explained. Finally, it is found that fT is limited by the minority charge stored in the BE junction and that \BVCEO is mainly determined by the tunneling mechanisms in the base–collector space-charge region. [ABSTRACT FROM PUBLISHER]