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Comments on a paper which suggests a ring hybrid adopting a Marchand balun. Use of the main concept that the ring hybrid consists of an in-phase divider and a balun; Comparison between measured and theoretical results of a Marchand balun without an in-phase power divider.

This paper proposed a method of synthesizing absorptive common-mode filters (A-CMFs) analytically with high absorption efficiency and two designable absorption bands. The proposed method is carried out by a novel circuit architecture and its analysis procedure. In differential mode, the integrity of the differential signals is maintained, and in common mode (CM), two absorption frequency bands can be obtained theoretically. These bands are designable with the analytical equations derived in this paper, so a dual-band or broadband A-CMF design can be easily synthesized by our proposed method. The authors also show that this method can make any one of R-CMFs “upgrade” to an A-CMF by simply adding an additional circuit, and this might be a revolutionary progress for the currently used CM-suppression techniques. To make the proposed concept more understandable, an example is used to demonstrate how the synthesizing methodology works, where a broadband A-CMF with its absorption bands located at 2.4 and 3.6 GHz is designed and implemented. Furthermore, a test sample of this A-CMF is fabricated on a four-layer printed circuit board. It is measured on a probing station, and the measured results are very similar to the simulated results. Finally, a comparison table of all the related works is given, showing that this proposed method really makes a significant improvement for A-CMF techniques. It is worth noting that this circuit design can provide a broadest 95%-absorption band to our best knowledge. [ABSTRACT FROM AUTHOR]

In this paper, we propose a compact topology for high-frequency bandpass filters using coaxial cavities embedded in a bed of nails, including a complete design procedure combining equivalent circuit models and full-wave simulators. The resonance generated around a shortened cylindrical nail of the bed hosting structure is used as the basic element of the proposed filter, which is fed through groove gap waveguides. For design purposes, an equivalent circuit model of the considered resonance is first obtained, and then the coupling levels between resonators are recovered with the distance between adjacent shortened nails. In order to validate the proposed structure and its design procedure, a filter prototype with a bandpass response (centered at 30 GHz and with relative bandwidth of 1.7%) has been designed, manufactured, and measured. Good experimental results, in terms of insertion losses (with a minimum value of 1.6 dB) and return losses (greater than 16.6 dB in the whole passband), have been achieved. [ABSTRACT FROM AUTHOR]

Fully coupled transient analysis of electromagnetic (EM)-circuit systems is highly desirable for a number of applications. Over the last decade or so, there have been several papers that present effective solutions to this problem within the context of full-wave differential or integral equation solvers. The method typically espoused is as follows: discretize the underlying EM system, couple with the circuit subsystem self-consistently, and then solve the coupled system. Within this framework, nonlinearities are easily accounted for in the solution process. This is in direct contrast to frequency domain analysis, wherein one defines ports that couple the EM and circuit subsystems, i.e., the representation of the EM system using an effective impedance/admittance as seen at the circuit terminals. This approach permits: 1) solution only at the circuit level and 2) one can readily incorporate different circuits without having to solve the coupled system repeatedly. Achieving the same functionality in the time domain is a challenge. In this paper, we present a solution to this problem. We will prescribe the means to effectively represent the EM subsystem in terms of a transient admittance, thus facilitating a solution to the coupled system via a circuit-level solve. Several results are presented that serve to validate the proposed approach and demonstrate its effectiveness. [ABSTRACT FROM AUTHOR]

In earlier papers, analytical formulas were derived to estimate the maximum crosstalk in the frequency domain for systems with electrically long signal lines. These formulas were developed to give designers intuitive feedback as to the causes for crosstalk problems and methods for maximum crosstalk reduction. In one of these papers, the maximum crosstalk estimates are based on intuitive relationships for infinitely long transmission lines. While the resulting model is quite simple and easy to understand, its limitations are poorly understood. In another paper, the maximum crosstalk estimates are based on a mathematically rigorous integral formulation, but the resulting model is relatively complex. This rigorous model is derived assuming the signal lines are weakly coupled and the transmission line characteristic impedances are approximately the same over the entire lengths of the aggressor and victim circuits. The following paper illustrates how the less rigorously developed estimates, based on infinitely long transmission lines, may be derived from the mathematically rigorous maximum crosstalk estimates for lossless and homogeneous transmission lines in the frequency domain. The resulting derivation provides insight into the limitations and mathematical validity of the less rigorous estimates that are not available in the original paper. The mathematically rigorous maximum crosstalk estimates are shown to have fewer and less restrictive assumptions than the estimates based on infinitely long transmission lines. Measurements and simulations are presented that validate results and illustrate maximum crosstalk estimate limitations. [ABSTRACT FROM AUTHOR]

This paper proposes a new class of multisine excitations that allows efficient characterization of nonlinear circuits. By offsetting the frequency of tones, one can distinguish between different intermodulation products in a multisine response. This property leads to many applications for nonlinear circuit characterization, such as in-band distortion measurements, memory effects characterization, and model performance assessment. Some applications are highlighted in this paper, focusing especially on the characterization of memory effects. The effectiveness of the approach is demonstrated with a series of measurement results. [ABSTRACT FROM AUTHOR]

This paper presents the design consideration on a converged Rx surface acoustic wave (SAW) duplexer module for integrated RF front end. Two different matching-circuit and notch-circuit configurations were examined with importance placed on electrical characteristics (insertion loss and isolation of duplexer) and simplification of module, respectively. From circuit simulations and examinations, we verified that a simplified design was best in terms of both characteristics and space in the case of a finite inductor's Q. We also fabricate a quad-band converged Rx module (Band I + II, V + VIII) using an SAW duplexer and verified that its electrical characteristics agree well with our simulation results. [ABSTRACT FROM AUTHOR]

The performance of additive manufactured (AM) RF circuits and antennas is continuously improving, and in some cases these AM components are comparable to state-of-the-art circuits made with traditional manufacturing techniques. Medium to high-power waveguides made with AM methods such as copper-plated plastics, selective laser melting (SLM), and copper additive manufacturing (3-D CAM) have shown good performance up to terahertz frequencies. In this paper, binder jetting (BJ) metal printing is characterized using electron beam microscopy [scanning electron microscopy (SEM)] and energy dispersive spectroscopy. The RF performance of the 3-D-printed circuits is benchmarked with Ka-band cavity resonators, waveguide sections, and a filter. An unloaded resonator $Q$ of 616 is achieved, and the average attenuation of the WR-28 waveguide section is 4.3 dB/m. The BJ technology is tested with a meshed parabolic reflector antenna, where the illuminating horn, waveguide feed, and a filter are printed in a single piece. The antenna shows a peak gain of 24.56 dBi at 35 GHz. [ABSTRACT FROM AUTHOR]

A class of self-isolated harmonic oscillator (SIHO) with a feedback-loop structure is able to significantly reduce the pulling effect without involving extra circuit complexity such as a buffer amplifier. In the first part of this paper, the operation principle of the SIHO is theoretically studied through equivalent circuit models and X-parameter techniques. Closed-form expressions are derived to represent the respective linear and nonlinear equivalent impedances of SIHO subnetworks perturbed by varied load and injected signals. A conventional feedback-loop oscillator structure delivering the fundamental tone is used for comparative study. Such a modeling technique reveals the physical principle and behavior parameters that have an impact on the pulling effect. The experimental verification of the SIHO operation principle and modeling is presented as the second part of this paper. To this end, a harmonic measurement and design system is proposed and implemented for the design of an exemplary SIHO, which delivers a 4-GHz signal with 16.6-dBm power, 28% dc-RF efficiency, and −136.5-dBc/Hz phase noise at 1-MHz offset. The design process does not rely on circuit simulation software packages or a prior knowledge of the large-signal model of transistors, thus demonstrating the concept of a model-free nonlinear circuit design automation based on the experimental optimization. The SIHO circuit model is validated with the measured X-parameters of its nonlinear subnetwork. [ABSTRACT FROM AUTHOR]

A comprehensive method to synthesize negative group delay (NGD) in the microwave regime with a maximally flat response is proposed in this paper. This method is based on transversal-filter topologies; it will be shown that by choosing proper coupling coefficients of each tap of a transversal filter, we can realize NGDs with maximally flat characteristics at the output of the transversal filter. The desired coefficients to realize maximally flat NGDs with various amount of group delay are analytically derived and tabulated in this paper. Furthermore, the results are verified experimentally through microwave transversal-filter approaches in both passive and active ways using multi-section asymmetric directional couplers and distributed amplifiers. [ABSTRACT FROM PUBLISHER]

This paper describes a method for characterizing mixer noise in terms of several noise parameters. A measurement method for extracting the noise parameters is proposed and verified with simulations of a mixer and measurements of two mixers. Direct measurements of single-sideband noise figures are accurately represented by the measured noise parameters, which fully characterize the noise figure of the mixers for all harmonic impedance loading conditions. Over 606 measurements, the maximum error between the measured and modeled noise factors was less than 0.12 dB. This is the first paper that proposes and verifies a method of mixer noise parameter measurements. [ABSTRACT FROM PUBLISHER]

This paper presents the design of an RF energy-harvesting circuit when excited by signals with a time-varying envelope such as multi-tone signals or digitally modulated signals with random modulation. The input matching network and the output load of a rectifier circuit are simultaneously optimized using harmonic balance in order to maximize its RF–dc conversion efficiency. This paper focuses on identifying the optimum load value, which corresponds to maximum efficiency for different types of input signals. The efficiency curves versus the load value show a single optimum efficiency point, which is a different for signals with a time-varying envelope and continuous wave (CW) signals. Specifically, for the series diode rectifier that was considered, the optimal load shifts to larger values as the signal peak-to-average-power-ratio (PAPR) increases compared to a CW signal with the same average power. As a result, for certain load values a signal with a time-varying envelope can result in a larger efficiency value than a CW signal. The peak efficiency value does not necessarily improve by using a signal with a time-varying envelope. A UHF rectifier prototype is built and its performance is evaluated experimentally showing good agreement with simulation. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of irregular pulsed RF signals on the pulse-to-pulse (P2P) stability of a microwave power GaN HEMT amplifier. This study is based on both the time-domain envelope measurements and nonlinear circuit envelope simulations of P2P stabilities. Measurements and simulations are performed with an irregular pulse train that integrates a long silence (i.e., off-time) between each periodic burst of RF pulses because of its influence on temperature and trap behaviors of GaN HEMTs. The first aim is to experimentally characterize the impact of silence durations and output mismatching on the amplitude and phase P2P stabilities of a 10-W S-band GaN HEMT amplifier. The second objective is to assess the ability of nonlinear HEMT models to fit the time-domain measurements of pulse-to-pulse stabilities. This final part of the paper is focused on the relative impact of electrothermal and drain-lag models on the nonlinear circuit envelope simulations of pulse-to-pulse stabilities. It is demonstrated that both the thermal and trapping effects have to be considered to fit the complex behavior of measured pulse-to-pulse stabilities for microwave GaN HEMT power amplifiers. [ABSTRACT FROM AUTHOR]

By adding a complex isolation component between two 90^\circ transmission lines at an arbitrary phase angle from the input terminal, a small Wilkinson power divider provides physical separation and electrical isolation between two output ports. General design equations for the complex isolation component are derived from even- and odd-mode analysis. Parallel and series RLC circuits are chosen to realize complex isolation components, respectively. Considering the bandwidths of S22, S33, and S32, inductors in both parallel and series RLC components are omitted to get the widest bandwidths; mathematical proof and design examples are also presented in this paper. A coupled line section with a compensating capacitor is introduced to reduce the circuit size, where characteristic impedances between even and odd mode are different in the coupled line section, and their electrical lengths are also different in inhomogeneous medium. Mathematical equations and simulation examples prove that the compensating capacitor compensates the characteristic impedance difference in the homogeneous medium and the electrical length difference in the inhomogeneous medium. Finally, an experimental circuit shows good agreement with the theoretical simulation. [ABSTRACT FROM AUTHOR]

Non-Foster elements are highly desired to overcome the bandwidth limit of electrically small antennas, cloaking, and metamaterials. However, they are prone to be unstable and thus it is quite challenging to implement non-Foster circuits in practice. Hence a rigorous and effective method of analyzing the stability should always be the priority when designing a non-Foster network. This paper applies normalized determinant function to analyze the stability of non-Foster circuits. A floating-version negative capacitor based on Linvill’s negative impedance converter is taken as the example. Factors affecting the stability in the practical design are thoroughly investigated, including device parasitics, dc biasing, distributed transmission line in the layout and load impedance. Circuit parameters are substituted with practical values to reduce the complexity of calculation. Finally, experiments are conducted to verify the analysis. [ABSTRACT FROM AUTHOR]

A flip-chip-assembled W-band receiver composed of a 90-nm CMOS chip and an integrated-passive-device (IPD) carrier is presented in this paper. The chip which integrates a low-noise amplifier, a single-sideband mixer, a frequency doubler (FD), and a wide-band variable-gain amplifier, is flip-chip packaged to the IPD carrier through a low-loss interconnect. The simulated loss of the interconnect without any compensation network is only 0.95 dB at 94 GHz. The FD can provide differential output without any additional lossy balun required, effectively increasing the FD output power, and hence relaxing the local oscillator generation circuit design. The experimental results show that the proposed packaged receiver can provide a variable gain from 11.3 to 48.2 dB, while having an input 1-dB compression point from −43.7 to −29 dBm as the RF frequency is 90 GHz. The intermediate bandwidth and minimum noise figure can be 1.0 GHz and 7.8 dB, respectively. The proposed receiver only consumes 73.9 mW from a 1.2-V supply. As compared with prior works, the proposed receiver exhibits higher gain, lower noise, and lower power dissipation even though a less-advanced 90-nm CMOS technology is adopted. To the best of the authors’ knowledge, this is the first W-band CMOS receiver assembled on an IPD carrier reported thus far. [ABSTRACT FROM AUTHOR]

This paper presents a tunable reflection/transmission coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/transmission coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/transmission coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8–1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a novel concept for realizing an RF power limiter for protecting superconductor digital receivers. A lumped-element niobium (Nb)-based filter is used as a protection circuit. It consists of lumped-element resonators formed using spiral inductors and metal–insulator–metal capacitors integrated on a multilayer Nb process. The circuit operates as a filter at low-power levels and as a reflector at high-power levels. The lumped-element filter circuit is studied in detail to explain the performance of the filter at high-power levels. It is concluded that some of the lumped-element inductors switch from being inductors when operating at low-power levels to being capacitors when operating at high-power levels. When the lumped-element inductors switch to capacitors, the filter circuit that consists of LC resonators switches to a circuit that consists of capacitors, causing the input power to be reflected back. Both the theoretical and experimental results are presented to verify this phenomenon. In addition to applications in RF power limiters, the concept can be employed to realize transmit/receive (T/R) switches in order to isolate the (T/R) circuit from the receive circuit. [ABSTRACT FROM AUTHOR]

Low-frequency resonances with low stability margins affect video bandwidth characteristics of power amplifiers. In this paper, a nonconnectorized measurement technique is presented to obtain the low-frequency critical poles at internal nodes of a hybrid amplifier. The experimental setup uses a high-impedance probe connected to a vector network analyzer to obtain a fully calibrated closed-loop frequency response that is identified to get the poles of the device at low frequency. Compared to previous connectorized solutions, the approach avoids the ad hoc insertion of extra RF connectors to access the low-frequency dynamics of the amplifier. In addition, it simplifies the characterization at multiple internal nodes, which is worthwhile for an efficient detection and fixing of critical low-frequency dynamics in multistage power amplifiers. The technique is first applied to dc steady-state regimes and compared to the connectorized approach on a single-stage amplifier. Next, it is applied to a three-stage amplifier to show its potential to detect the origin of the undesired dynamics and the most effective way to increase stability margin. Finally, the technique has been extended to the large-signal case to increase its usefulness for the design and diagnosis of high-power amplifiers. [ABSTRACT FROM AUTHOR]

This paper presents a quasi-static surface-based partial element equivalent circuit (PEEC) model for electromagnetic problems consisting of coupled conductors and heterogeneous dielectrics of finite size. The PEEC model is based on the surface equivalent principle. Unlike the traditional surface-based PEEC models, in which the integral equations are set up by enforcing the field continuity in the true field region, the homogeneous integral equations in this model are obtained by enforcing the tangential null field condition in the null field regions. Simplified integral equations are obtained under the quasi-static assumption, in which the circuit elements carrying electric currents and magnetic charges on the dielectric surfaces are vanished. Consequently, the size of the subcircuit describing dielectrics is reduced significantly compared to the full-wave surface-PEEC (S-PEEC) model. Since the quasi-static S-PEEC model only contains frequency-independent circuit elements, it can be conveniently used for time-domain simulation. Three numerical examples are presented to validate the new PEEC model for typical embedded RF passive components, packaging and interconnection problems in both the frequency domain and the time domain. Excellent agreement is observed between the results of the proposed PEEC model, S-PEEC model, and those of commercial software within the quasi-static frequency range. [ABSTRACT FROM AUTHOR]

In this paper, a new method is proposed to synthesize a linearity-enhanced Doherty power amplifier (DPA) without deteriorating its efficiency. This method determines the combiner network parameters so that a predefined amplitude-to-phase (AM–PM) characteristic is produced while maintaining proper load modulation and consequently good back-off efficiency. The predefined AM–PM characteristic is chosen to be the inverse of the main transistor to enhance the overall DPA linearity. For proof-of-concept validation purposes, a linearity-enhanced DPA circuit prototype is designed to provide linear overall AM–PM characteristics over the frequency band of 4.7–5.3 GHz. Meanwhile, its input matching network is designed to minimize the amplitude-to-amplitude (AM–AM) distortion by properly selecting the source impedances. The measurement results of the DPA prototype under continuous-wave stimuli reveal AM–PM and AM–AM characteristics with maximum phase and gain compression/expansion below ±1° and ±0.25 dB, respectively, when the input power level is swept up to a saturation level of 39 dBm over 4.9–5.3 GHz. Furthermore, when driven with carrier aggregated signals with modulation bandwidths of up to 160 MHz and a peak-to-average power ratio equal to 7.4 dB, the DPA prototype maintains an adjacent channel leakage ratio of better than −40 dBc with a drain efficiency in the excess of 40% and an average output power of 32 dBm, without resorting to any additional linearization schemes. The proposed DPA methodology paves the road for the application of the DPA technique to 5G massive multiple-input and multiple-output transmitters with relaxed linearity requirements as it avoids the extra complexity and power consumption overhead associated with dedicated linearization schemes. [ABSTRACT FROM AUTHOR]

The performance of additively manufactured microwave passive elements and interconnects continues to improve as better materials, and process techniques are developed. In this paper, laser-enhanced direct print additive manufacturing (LE-DPAM) is used to fabricate capacitors and inductors for coplanar waveguide (CPW) circuits. Acrylonitrile butadiene styrene is used as the dielectric that is printed using fused deposition modeling, and DuPont CB028 conductive paste is deposited using microdispensing. These two techniques are combined with picosecond-pulsed laser machining to achieve $\simeq 12$ - $\mu \text{m}$ slots on printed conductors, producing aspect ratios greater than 2:1. The same laser is used to fabricate vertical interconnections that allow for the fabrication of multilayer inductors. Inductances in the range of 0.4–3 nH are achieved, with a maximum quality factor of 21, selfresonance frequencies up to 88 GHz, and an inductance per unit of area of 5.3 nH/mm2. Interdigital capacitors in the range of 0.05–0.5 pF are fabricated, having a maximum quality factor of 1000, a capacitance per unit area of 1 pF/mm2, and selfresonances up to 120 GHz. All the components are made on the center line of a CPW that is 836- $\mu \text{m}$ wide. The results show that LE-DPAM enables the fabrication of compact passive circuits that can be easily interconnected with MMIC dies, which at the same time can be manufactured as part of a larger component. This enables the fabrication of structural electronics that are functional into the millimeter-wave frequency range. Bounds on the inductances and capacitances per unit area are related to material and geometry limitations. [ABSTRACT FROM AUTHOR]

This paper presents a novel design procedure for the class-EM amplifier. The numerical design procedure is applied to the design of the class-EM amplifier, which achieves simple and accurate designs for high-order circuits. As a result, no tuning process is necessary in the circuit implementations. In this paper, two types of auxiliary circuits are considered, namely, the zero-voltage switching class-E amplifier and the zero-voltage switching class-E frequency doubler. The class-E auxiliary amplifier has a lower driving power and a higher output power capability than the class-E auxiliary frequency doubler. On the other hand, the class-E auxiliary frequency doubler has lower number of the non-zero-current switchings than the class-E auxiliary amplifier and no on-interval of the antiparallel diode of the MOSFET. The laboratory experimental results agreed quantitatively with the numerical predictions, which validate the effectiveness of the proposed design procedure. [ABSTRACT FROM AUTHOR]

A new method of deembedding a test fixture effect from the data of microwave measurements is presented in this paper. It is shown that the traditional unterminating problem (the problem of finding fixture characteristics) being posed in a finite frequency range may be reduced to a problem of fitting the characteristics of the ‘thru’ experiment. The latter is proposed to be solved by using the genetic algorithm (GA). A special trick is suggested to take fixture power loss into consideration, which is sometimes necessary to increase the goodness of fitting the characteristics. Physically correct constraints for optimization variables and optimal parameters of the GA are discussed in this paper. The method is applicable for all microwave fixtures, except for those whose characteristics are influenced by the relative position of the adapters comprising the fixture. The method does not have any specific frequency limitation and does not require any calibration standards. The results of the experiments performed have validated a high efficiency of the method proposed, and confirm that the accuracy of a deembedding problem solution is close to the goodness of fitting data of the ‘thru’ experiment. [ABSTRACT FROM AUTHOR]

In this paper, the concept of the transmission phase shift of an impendance-matching network (IMN) has been introduced. The generalized two-port network parameters of the matching circuit, which matches an arbitrary complex load to a different complex source impedance incorporating the transmission phase, has been derived. In general, the IMNs are electrically asymmetric; however, there exist only two distinct values of phase shifts (180° apart) for a given source and load impedance for which the networks are symmetric, irrespective of the choice of design topology. Simple examples of symmetric matching networks like single and parallel transmission lines (TLs) have been studied. The design equations of several asymmetric matching networks like the stepped-impedance, the $\Pi $ -type, and the T-type network for a given load and source impedance with desired phase shift have been derived. The concepts of allowed and forbidden regions for such matching circuits, in the impedance phase-shift plane, have been established. Two prototype impedance transformers have been fabricated and measured to establish the proposed concept. [ABSTRACT FROM AUTHOR]

This paper delivers a considerable improvement in the framework of the statistical simulation of highly nonlinear devices via polynomial chaos-based circuit equivalents. Specifically, a far more efficient and “black-box” approach is proposed that reduces the model complexity for nonlinear components. Based on recent literature, the “stochastic testing” method is used in place of a Galerkin approach to find the pertinent circuit equivalents. The technique is demonstrated via the statistical analysis of a low-noise power amplifier and its features in terms of accuracy and efficiency are highlighted. [ABSTRACT FROM AUTHOR]

Coupled electromagnetic resonances have various important applications in microwave engineering. Among them, the newly discovered electromagnetically induced transparency (EIT) has attracted much interest. In this paper, we explore the use of configurable electrically induced transparency to construct a microwave “diffractive medium” whose air-like optimally matched transparency and metal-like optimally reflective opacity can be conveniently switched by a binary dc voltage. Different from EITs based on closely coupled resonances, we use decoupled electrically induced resonances to achieve a low-loss transparency along with an optimal impedance matching with air. Satisfying the condition of a lossless perfectly matched layer, such transparency and opacity can be obtained in a wide range of incident angles. We validate our approach by experimentally demonstrating two electrically controlled steering antennas based on diffractive grating effect, both with thin planar apertures and binary digital control circuits. The proposed approach can be extended to higher frequencies, achieving configurable diffractive devices at millimeter-wave and terahertz frequencies. [ABSTRACT FROM PUBLISHER]

The distributed power detector is an alternative detector topology to overcome the wideband input matching limits of traditional matching techniques. A distributed power detector absorbs the bandwidth limiting parasitic junction capacitance of the diode in a traveling-wave structure. This paper presents a detailed theoretical analysis of the diode-based distributed power detectors. A lumped-element transmission line model is used to design the power detector with wideband RF input matching. Furthermore, a generalized analytical expression for the current and voltage responsivities of an ${n}$ -section power detector is derived. The noise analysis of the power detector is also carried out to predict its frequency-dependent noise equivalent power (NEP). The analysis is experimentally validated by designing two- and three-section distributed power detectors using packaged Schottky diodes on a PCB substrate. The three-section design demonstrates a measured video bandwidth of at least 46 MHz and a measured $S_{11}$ below −10 dB from 0.1 to 5.3 GHz. A maximum voltage responsivity of 17.57 kVW−1 is measured at 5.3 GHz. It achieves a measured input-referred square-law dynamic range of at least 51 dB for a ±1-dB error. The design has a measured NEP of less than 9.6 pW/ $\sqrt {\mathrm{ Hz}}$ for the entire bandwidth of operation. Simulations and measurements show a very good agreement with the developed theory. [ABSTRACT FROM AUTHOR]

Folded reflectarray antenna features high gain, low profile, and low sidelobe level, but also faces several challenges in scannability, manufacturing, assembling, and integration with planar circuits, especially at millimeter-wave and terahertz frequencies. To alleviate these issues, this paper presents a slot antenna based on substrate integrated waveguide (SIW) to replace conventional horn. This SIW slot antenna is then inherently integrated with reflectarray elements in the same single-layered printed circuit board (PCB) for the first time. Moreover, this folded reflectarray is able to scan its narrow beams in 2-D, by controlling the polarizing grids. The whole reflectarray is fabricated by the commercial low-cost PCB process and can be highly integrated with planar active circuits. Measured results show that the proposed reflectarray achieves a 2-D scanning zone of 14° $\times$ 14°, a gain of 27.4 dBi, and a cross-polarization level less than −24 dB. The proposed folded reflectarray is promising for several application scenarios including millimeter-wave high-resolution imaging and fifth-generation communications. [ABSTRACT FROM AUTHOR]

The empty substrate integrated waveguide (ESIW) technology is recently receiving special attention, since it preserves the many advantages of SIW circuits but provides an enhanced behavior due to avoidance of dielectric filling. Many circuits have been designed in the ESIW technology, including several filters with different performances. The next challenge is to achieve the maximum possible compactness degree for these circuits. In this paper, we present the design of a multilayer empty substrate integrated filter with the same performance as if it were manufactured in a single layer but significantly increasing its compactness and mechanical resistance. [ABSTRACT FROM AUTHOR]

In this paper, series feed networks based on composite right/left-handed transmission line for dual-polarized frequency scanning phased array antenna are presented. The proposed all-passive feed networks provide unique frequency dispersion and adjustable current amplitude distribution, which enable continuous backward-to-forward beam scanning capability as well as the directivity, beamwidth, and sidelobe level controllability of the incorporated array antenna. The working mechanisms are demonstrated through broadband dual-polarized aperture-coupled antenna elements and series feed networks that support uniform/binomial current amplitude distributions. Backward-to-forward frequency beam scanning and wide range beam shaping capability for dual-polarization states of the proposed phased array are validated in both simulation and measurement. [ABSTRACT FROM PUBLISHER]

Modern wireless network operators are consistently looking for improvements in the wireless access infrastructure that minimize size, weight, and power. Therefore, compact multiband RF and wideband RF solutions offer an attractive role in forthcoming fifth generation networks. This paper presents a novel compact wideband RF transmitter architecture that is based upon an undersampled digital predistortion (DPD) methodology. The proposed architecture minimizes the required number of RF/analog components in the system by using RF-DAC-based direct RF sampling at the forward transmitter data path and one undersampled analog-to-digital conversion (ADC) with certain bandpass filters at the DPD sampling receiver path. Extensive experimental results validate that the DPD-enabled RF transmitter bandwidth can be significantly increased using the proposed multirate track-and-hold amplifiers architecture. Experimental tests achieved multiple GHz DPD bandwidths with satisfactory linearization performance via very compact sampling receiver that has one undersampled ADC. Particularly, we evaluated three application scenarios: 1) three-band carrier aggregated LTE signals (each one occupying 20-MHz instantaneous bandwidth), the linearization performance achieved 50-dBc adjacent channel power ratio (ACPR) with more than 1-GHz bandwidth using ADC running at 76.8 and 61.44 MSPS; 2) single-band LTE signal with continuous 100-MHz instantaneous bandwidth, the linearization performance achieved −48-dBc ACPR using 61.44-MSPS ADC; and 3) single-band LTE signal with continuous 20-MHz bandwidth at 4 GHz, the linearization performance achieved −54-dBc ACPR using 61.44-MSPS ADC. [ABSTRACT FROM PUBLISHER]

This paper presents a differential eight-path bandpass filter with tunable center frequency and bandwidth. Fully differential Miller compensated Butterworth Gm-C biquads are used to implement the active low-pass filters required in the structure of the eight-path filter. The -3-dB bandwidth of each Gm-C filter can be tuned from 2.5 to 51 MHz by means of six digital bits. The center frequency of the eight-path filter can be tuned from 100 MHz to 2 GHz by varying the frequency of the 12.5% duty cycle clocks applied to the gates of the switches in the filter. A wideband low-noise amplifier (LNA) is designed to precede the eight-path filter and acts as an active single-to-differential converter while providing a moderate voltage gain to compensate for the noise produced by the eight-path filter. The LNA has a noise canceling common-gate common-source with 20 dB of gain and a noise figure (NF) of 1.8 dB. The filter and LNA are designed and fabricated in 180-nm CMOS process. The circuit operates in 100 MHz to 2 GHz frequency range, achieving a voltage gain of 19 dB and a total NF of 3.3 dB. The achieved out-of-band input third-order intercept point of the circuit is +23 dBm, and the power consumption of the filter is approximately 32.3 mW, while the LNA consumes 16.5 mW. [ABSTRACT FROM AUTHOR]

In this paper, a low-temperature co-fired ceramic (LTCC) diplexer is presented with compact size and high isolation. By using the common stub-loaded resonator shared by two channel filters, combining and matching networks are eliminated and only three resonators are used to design the two second-order channel filters, resulting in simple structure and miniaturized size. A novel transmission path is utilized to not only realize the higher channel filter but also prevent the signal at the lower frequency band. And a specific coupling region is selected to simultaneously realize the coupling strength required by lower channel filter and a transmission zero at higher-band frequency. In this way, each channel filter can generate a transmission zero at the passband frequency of the other channel filter, resulting in high isolation. Moreover, the bandwidths and center frequencies of the two channel filters can be individually controlled due to the design flexibility of the multilayer LTCC structure. For demonstration, a diplexer operating at 3.5 and 5.5 GHz is fabricated. The core circuit has the compact size of 1.9 mm $\times1.7$ mm \times2$ mm or 0.054~\lambda _{g} \times 0.048 \lambda _{g} \times 0.057~\lambda _{g} . Within the 3-dB passbands of the lower and higher channel filters, the measured isolation levels are better than 40 and 45 dB, respectively. [ABSTRACT FROM PUBLISHER]

A new method is proposed for the design of large-scale wideband resonator-coupled bandpass filters and diplexers. Corrected group delay responses of sub-circuits in combination with space mapping are used to compute the physical dimensions from the coupling matrix model. The coupling matrices are designed using the available theories. The method is based on dividing the structures into many sub-circuits and calculating the group delay responses of the reflection from which the coupling parameters and cavities’ resonant frequencies can be extracted. Using a linear space mapping, the structures are optimized efficiently. Depending on the structure’s complexity, few to no full-wave optimization is needed to tune the structures to the true designated filtering function. Bandpass filters and diplexers with bandwidths up to approximately 22% have been designed successfully using the proposed approach. A novel stacked cascaded quadruplet filter has been developed using this method. The design of wideband all-pole filters and diplexers are addressed in the paper. [ABSTRACT FROM PUBLISHER]

In this paper, an incoherent radar network based on integrated radar sensors is presented. It consists of radar sensor nodes with independently generated frequency-modulated continuous wave-modulated transmit signals, performing both monostatic and bistatic distance measurements. An architecture to operate such a cooperative bistatic network is introduced and an optimal parameterization of the system is presented. Several nonidealities of frequency synthesizers, that are important for such cooperative radar networks, are discussed and their influence on system performance is evaluated. A prototype of the cooperative bistatic network has been realized using highly integrated radar sensors at 122 GHz. Radar measurements using the prototype prove the feasibility and potential of the network approach. The complete signal processing chain is presented, including an adapted multilateration algorithm for target position estimation using all measured distances. [ABSTRACT FROM PUBLISHER]

In this paper, a unified method is introduced and formulated for deriving the equivalent circuit model of a guided wave structure as well as its characteristic impedance for any mode. This method is developed through the combination of a generalized multimode calibration and a full-wave simulation, and it is applicable to the fundamental mode as well as higher order modes. The method is verified for both TEM and non-TEM propagating modes and is applied to extract the characteristic impedance and circuit model of non-TEM guided-wave structures. This scheme allows for the effective use of a commercial electromagnetic field simulator in removing inherent numerical simulation noises or errors. Extracting circuit parameters through this technique for establishing equivalent circuit models can overcome the shortcomings encountered in the modeling of guided-wave eigenvalue problems as well as in the design of multimode structures. [ABSTRACT FROM PUBLISHER]

In this paper, we show a new bandstop filter circuit topology. Unlike conventional bandstop filter circuit topologies, the new circuit topology has inter-resonator coupling structures. The presence of these inter-resonator coupling structures enables convenient switching from a bandstop to a bandpass filter. Using the new bandstop filter topology, this paper demonstrates a design of a frequency-agile bandstop-to-bandpass switchable filter. The filter is composed of tunable substrate-integrated cavity resonators and can be switched to have either a bandstop or bandpass response. Switching is achieved by turning on and off switches placed within the filter structure. A prototype of the proposed design is fabricated and the concept is verified experimentally. [ABSTRACT FROM AUTHOR]

A 2.4/5.7-GHz dual-band Weaver-Hartley architecture, using 0.18-μm CMOS technology, is demonstrated in this paper. The 2.4-GHz signal is set to be the image signal when the desired signal is at 5.7 GHz, and vice versa. Since the Weaver and Hartley systems are combined into this architecture, the demonstrated architecture rejects not only the first image signal, but also the secondary image signal. The image-rejection ratios of the first image signal and the secondary image signal are better than 40 and 46 dB, respectively. In this paper, a diagrammatic explanation is employed to obtain the image-rejection mechanisms of the Weaver-Hartley architecture. [ABSTRACT FROM AUTHOR]

This paper develops a novel ultra-wideband bandpass filter by cascading a broadband bandpass filter with another broadband bandstop filter. Properly selected impedances of transmission lines achieve broadband bandpass and bandstop filters and make independent designs possible. Detailed design and synthesis procedures are provided; moreover, agreement between measured and theoretically predicted results demonstrates feasibility of the proposed filter. Due to its simple structure, the ultra-wideband bandpass filter newly introduced in this paper is suitable for integration in the single-chipped circuit or implementation on printed circuit boards. [ABSTRACT FROM AUTHOR]

This paper presents the application of a fast and accurate layout-level statistical analysis methodology for the diagnosis of RF circuit layouts with embedded passives in liquid crystalline polymer substrates. The approach is based on layout-segmentation, lumped-element modeling, sensitivity analysis, and extraction of probability density function using convolution methods. The statistical analyses were utilized as a diagnosis tool to estimate distributed design parameter variations and yield of RF circuit layouts for a given measured performance. The results of statistical analysis and diagnosis were compared with measurement results of fabricated filters. Statistical methods were also applied for design space exploration to improve system performance, as well as estimation of yield and diagnosis of faults during batch fabrication. [ABSTRACT FROM AUTHOR]

This paper presents the design of an optimized test and application setup for surface acoustic wave (SAW) filters. These structures have been investigated, including the test devices, by simulation techniques based on full-wave methods and common SAW simulation methods. In this paper, the simulation technique will be explained in detail, focusing on the interfaces of the simulation models. Parasitic electromagnetic effects in the test and application setup will be analyzed by simulation and measurement. This paper demonstrates the possibility of accurate performance prediction of SAW RF filters using specially designed test setups in the measurement and an optimized application environment, e.g., in mobile phones. Modular parts for such test setups and the application environment are discussed. [ABSTRACT FROM AUTHOR]

This paper presents experimental results on the measurement of the magnitude and phase response of RF and baseband signal paths made with a power detector. The frequency response is obtained by measuring the magnitude and phase of the output of the power detector when the forward path is excited by a pair of tones. This technique provides a means for making vector measurements using a scalar detector. Instruments, like network analyzers, commonly use a mixer and sinusoidal source to downconvert the signal for digitization and measurement. The downconversion in this paper is performed using a power detector and an extra tone in the excitation signal itself, drastically reducing hardware complexity. Important applications of this technique include the characterization of the digital-to-antenna path of a software radio and the equalization of the antialiasing filter in a wide-band arbitrary waveform generator. Three examples of measurement, one at low frequency and two others at radio frequencies, show that the errors in the measured response are comparable to those obtained using conventional network analyzers. [ABSTRACT FROM AUTHOR]

This paper provides a broadband measurement method at W-band for printed circuit board (PCB) properties using multiple substrate integrated waveguide (SIW) resonators, i.e., SIW multi-resonator method. Eight SIW resonators are designed in series fed by a rectangular waveguide through coupling slots. All resonators operate at TE101 mode with different resonant frequencies. Multi-resonator Foster form is employed to obtain unloaded resonant frequency of each SIW cavity. After introducing the testing procedure, a number of samples based on different PCBs are fabricated and accurately measured to verify the feasibility of this method. [ABSTRACT FROM PUBLISHER]

This paper reports a fully integrated 40-nm CMOS power amplifier (PA) for E-band applications. A neutralized bootstrapped cascode amplifier (NBCA) topology is proposed to enhance the power gain and output power at millimeter wave (mm-Wave) frequencies while maintaining the stability. A broadband 4-way differential parallel-series power combiner is employed to further increase the output power. Besides, both interstage and input passive networks are optimized to improve the bandwidth and common-mode stability. Occupying 0.25 mm^2, the proposed PA achieves a measured output power of 22.6 dBm with 19.3% peak power-added efficiency (PAEMAX). The 2-stage PA has a measured power gain of 25.3 dB. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of a bidirectional distributed amplifier (BDDA) in a 0.18- $\boldsymbol \mu \text{m}$ CMOS process. The performance of the BDDA is theoretically analyzed, and the optimum number of gain stages ($n_{\text {opt}}$), maximum achievable power gain ($G_{P}$), and circuit bandwidth are formulated. In addition, a new formula for proper choice of the number of DA stages (i.e., $n$) is offered where dc-power consumption of the circuit ($P_{\text {dc}}$) is also considered. This formula optimizes $G_{P}/P_{\text {dc}}$ , and it is preferred over the conventional $n_{\text {opt}}$ formula. To validate the theoretical analyses, a 2–12-GHz BDDA with high output 1-dB compression point of +16 dBm and small-signal gain of 10 dB is fabricated. The BDDA chip occupies 1.89-mm2 die area, and its average measured noise figure and $P_{\text {dc}}$ are 6.8 dB and 0.38 W in the high-power mode and 6.5 dB and 0.13 W in the low-power mode, respectively. [ABSTRACT FROM AUTHOR]

Based on multi-cell modified-T circuits, this paper proposes a novel circuit topology to realize a common-mode bandstop filter with differential-mode all-pass characteristics for high-speed digital differential circuits. The circuit behaviors for both differential and common modes are analyzed based on symmetrical network analysis techniques. Two transmission zeros at common mode can be synthesized by the derived formulas. The proposed design flow is used to realize a test sample in the integrated passive device process. Simulated and measured results are in good agreement. The common-mode suppression band (\vert S{ cc21}\vert < -10~{\dB}) is from 1.6 to 4.7 GHz, whose fractional bandwidth is nearly 100%. The cutoff frequency of the differential mode can maintain up to 10 GHz with a constant group delay. Moreover, eye diagrams under different signaling rates all perform well. Compared with the other literature, the proposed common-mode filter has a very wide common-mode stopband, the highest differential-mode cutoff frequency up to 10 GHz, and the most compact circuit size of 0.017~\lambdag\times 0.016~\lambdag . [ABSTRACT FROM PUBLISHER]

In this paper, a three-way reconfigurable power divider/combiner is proposed based on novel switch element with matching network (SEMN) and reconfigurable impedance transformer network (RITN). A good matching performance and a high isolation of the SEMN with one p-i-n diode can be obtained by the parasitic inductance and reverse capacitance of the p-i-n diode involved in matching circuits. With different parameters of one p-i-n diode under forward bias and reverse bias, the reconfigurable impedance matching can be obtained by the RITN with a simple structure. By using four RITNs and nine SEMNs, the three-way reconfigurable power divider/combiner can provide seven different states in the three-path mode, the two-path mode, and the single-path mode. For verification, a 5-GHz three-way reconfigurable power divider/combiner is designed and fabricated. In the three-path mode, measured insertion losses from port 1 to transmission ports (port 2, port 3, and port 4) are less than 0.74 dB and the isolations between transmission ports are higher than 32.1 dB. In the two-path mode with three states, the measured insertion losses are less than 0.93 dB; the isolations between transmission ports, transmission ports and isolation ports, and port 1 and isolation ports are higher than 27.5, 35.1, and 30.5 dB, respectively. In the single-path mode with three states, the measured insertion losses are less than 1.13 dB; the measured isolations between transmission ports and isolation ports are higher than 28.8 dB, and the isolations between port 1 and isolation ports are higher than 28.2 dB at the design frequency. [ABSTRACT FROM PUBLISHER]

In this paper, a substrate-induced drain-current noise model is developed in addition to the channel thermal noise to explain the non-white-noise characteristic found in the measured drain-current noise in the gigahertz range. The substrate-induced drain-current noise model is derived from the proposed small-signal equivalent circuit with a substrate coupling network and a substrate thermal noise source. The model parameter extraction method utilizing Y-parameter analysis on the proposed small-signal equivalent circuit is demonstrated. The model for the total drain-current noise, the gate-current noise, their cross-correlation, and thereafter the four noise parameters is presented and verified experimentally. Excellent agreement between simulated and measured noise data has been obtained over different dimensions and operating conditions. [ABSTRACT FROM AUTHOR]

With the aid of tri-operational mode synthesized transmission lines, an innovative heterogeneous integrated phased array having the functions of beam-switching and retrodirection in three individual bands is proposed and demonstrated. The key innovation is the array feeding network, capable of automatically reconfiguring its topology into three states without applying any active switch. In the low band, the feeding circuit, and hence, the entire system function as a beam-switching array using the Butler matrix for communication and positioning. In the mid and high bands, the integrated array rearranges its feeding network into pairs of isolated delay lines and becomes a Van Atta array and a phase-conjugating array, respectively, to re-radiate the signals to the direction of arrival. The core building blocks are the three-channel selector, tri-mode coupler, and diplexer, all realized by synthesized transmission lines with rigorous design formulae. The operational principle is first introduced, followed by the design and implementation of the key components. A phase compensation scheme is discussed to complete the tri-mode array design. This unique concept is experimentally verified using the radiation characteristics of the integrated array at the end of this paper. [ABSTRACT FROM AUTHOR]