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This study describes the design and implementation of a small printed ultra-wideband (UWB) antenna for smart electronic systems with on-demand adjustable notching properties. A contiguous sub-band between 3–4.1 GHz, 4.45–6.5 GHz, or for both bands concurrently, can be mitigated by the antenna. Numerous technologies and applications, including WiMAX, Wi-Fi, ISMA, WLAN, and sub-6 GHz, primarily utilize these band segments remitted by the UWB. The upper notch band is implemented by inserting an open-ended stub with the partial ground plane; the lower notch band functionality is obtained by etching a U-shaped slot from the radiating structure. The basic UWB mode is then changed to a UWB mode, with a single or dual notch band, using two diodes to achieve reconfigurability. The antenna has a physically compact size of 17 × 23 mm2 and a quasi-omnidirectional maximum gain of 4.9 dBi, along with a high efficiency of more than 80%, according to both simulation and measurement data. A significant bandwidth in the UWB region is also demonstrated by the proposed design, with a fractional bandwidth of 180% in relation to the 5.2 GHz center frequency. Regarding compactness, consistent gain, and programmable notch features, the proposed antenna outperforms the antennas described in the literature. In addition to these benefits, the antenna's compact size makes it simple to incorporate into small electronic devices and enables producers to build many antennas without complications. [ABSTRACT FROM AUTHOR]

Antenna design has evolved from bulkier to small portable designs but there is a need for smarter antenna design using machine learning algorithms that can meet today's high growing demand for smart and fast devices. Here in this research, main focus is on developing smart antenna design using machine learning applicable in 5G mobile applications and portable Wi-Fi, Wi-MAX, and WLAN applications. Our design is based on the metamaterial concept where the patch is truncated and etched with a split ring resonator (SRR). The high gain requirement is met by adding metamaterial superstrates having thin wires (TW) and SRRs. The reconfigurability is achieved by adding three PIN diode switches. Multiple designs have been observed by adding superstrate layers ranging from one layer to four layers with interchanging TWs and SRRs. The TW metamaterial superstrate design with two layers is giving the best performance in gain, bandwidth, and the number of bands. The design is optimized by changing the path's physical parameters. To shrink simulation time, Extra Tree Regression based machine learning model is used to learn the behavior of the antenna and predict the reflectance value for a wide range of frequencies. Experimental results prove that the use of the Extra Tree Regression based model for simulation of antenna design can cut the simulation time, resource requirements by 80%. [ABSTRACT FROM AUTHOR]

A compact flexible multi-frequency antenna for smart portable and flexible devices is presented. The antenna consists of a coplanar waveguide-fed slotted circular patch connected to a rectangular secondary resonator (stub). A thin low-loss substrate is used for flexibility, and a rectangular stub in the feedline is deployed to attain wide operational bandwidth. A rectangular slot is etched in the middle of the circular patch, and a p-i-n diode is placed at its center. The frequency reconfigurability is achieved through switching the diode that distributes the current by changing the antenna's electrical length. For the ON state, the antenna operates in the UWB region for −10 dB impedance bandwidth from 2.76 to 8.21 GHz. For the OFF state of the diode, the antenna operates at the ISM band (2.45/5.8 GHz), WLAN band (5.2 GHz), and lower X-band (8 GHz) with a minimum gain of 2.49 dBi and a maximum gain of 5.8 dBi at the 8 GHz band. Moreover, the antenna retains its performance in various bending conditions. The proposed antenna is suitable for modern miniaturized wireless electronic devices such as wearables, health monitoring sensors, mobile Internet devices, and laptops that operate at multiple frequency bands. [ABSTRACT FROM AUTHOR]

The design of smart antenna system for handheld devices has been a challenge for years. In this study, an attempt is made to try to solve this challenge by applying an optimal design method for the antenna arrays introduced previously. The method is based on the optimisation of the power transmission efficiency between two antennas. During the optimisation, the smart antenna array to be designed is used as transmitting antenna, and a testing antenna is introduced as receiving antenna, positioned in the far-field region. The maximum (minimum) possible radiation may then be achieved in the direction of the testing antenna if the power transmission efficiency is maximised (minimised). A compact low-profile smart antenna system has been designed using the method, which works at GSM-900 and PCS-1900 band and employs four identical inverted-F antennas as radiating elements. The dimension of the whole system is 140 mm x 80 mm x 7 mm, suitable for the application in handheld devices or other customer-premises equipment. [ABSTRACT FROM AUTHOR]

A small-scale optical device incorporated with an optical nano-antenna is designed to operate as the remote artificial eye using a tiny conjugate mirror. A basic device known as a conjugate mirror can be formed using the artificial eye device, the partially reflected light intensities from input source are interfered and the 3D whispering gallery modes formed within the ring centers, which can be modulated and propagated to the object. The image pixel is obtained at the center ring and linked with the optic nerve in the remote area via the nano-antenna, which is useful for blind people. [ABSTRACT FROM PUBLISHER]

A novel elliptic-function low-pass filter (LPF) is Presented, which consists of a Electromagnetic band gap on the ground plane. The Electromagnetic band gap provides the required wideband attenuation in stop band, while the slot provides steep transition from pass band to stop band. A 5.425 GHz five-pole LPF is developed and experimental results show that it has a sharp cutoff frequency response. The measured pass band insertion-loss is below 1.2 dB, and the rejection band over 15 dB is from 5.425 GHz to 8.25 GHz, Which increases from 2.95 GHz. [ABSTRACT FROM AUTHOR]

In this paper, switched beam smart antenna systems are investigated to improve the performance of wireless networks. The microstrip technology of antenna arrays with Butler matrix topology as a beam-former is used to implement the switched beam smart antenna system. The optimum design of a 4x4 planar Butler matrix array, operating at 5.6 GHz for WLAN applications. System's design and optimization was based on computer simulations. [ABSTRACT FROM AUTHOR]

A dual-band and ±45° dual-polarized antenna is proposed for 2G/3G mobile communications in this paper. The proposed antenna consists of five elements for the lower band and ten elements for the upper band. Results for a single element and antenna array are presented. The front-to-back ratio is from 25 dB to 30 dB, and the axial cross polarization ratio is from 19 dB to 22 dB in a single low band unit. The dual-band array achieves a bandwidth of 15.7% (820-960 MHz) for the lower band and a bandwidth of 23.7% (1710-2170 MHz) for the upper band, covering the frequency bands required by 2G/3G systems. Simulation results show that the gains for antenna array are 15.7 dBi for the lower band and 19.1 dBi for the upper band, which is suitable for base stations applications. [ABSTRACT FROM AUTHOR]

A formula for the complex transmission coefficient between the receiving and transmitting antennas is derived. The formulas define the nomenclature of the normalized parameters of satellite system antennas and are the basis for estimating the error in measuring the distances between the electrical phase centers of antennas. [ABSTRACT FROM AUTHOR]

The method of a T-shaped antenna loading T-shaped slots for multiple band operation is presented in this paper. Inspired by the fractal antenna, the proposed method is intended to be used for designing multiple band antennas. Through loading T-shaped slots in the terminals of a T-shaped antenna, dual or triple operating bands can be achieved. In order to validate the feasibility of this method, this type of antenna is designed and simulated. The antennas are respectively fed by two different feeding transmission lines (microstrip transmission line and coplanar waveguide (CPW) transmission line) for the purpose of identifying the method that can be commonly used. The parametric analysis in detail has been given to explain the effects of the key parameter variations. For WLAN and WiMAX applications, the antennas are fabricated and measured. Both simulated and measured results are presented to demonstrate the feasibility of these designs. [ABSTRACT FROM AUTHOR]

A design of stacked square-ring patch antennas with quadri-polarization diversity is proposed. The polarization switching is realized with a 1-to-4 reconfigurable feeding network composed of a quasi-lumped coupler and PIN diodes. The size of the feeding network is less than 0.01\lambda0^{2}, where \lambda0 is the free-space wavelength of the operating frequency. In addition, by controlling dc voltages, the operation of the feeding network can be varied among four different modes. The performances of the stacked patch antenna and the reconfigurable feeding network are respectively exhibited. A prototype that integrates the feeding network into the inner slot of the lower square-ring patch of the stacked patch antenna is designed and constructed. The prototype can provide dual orthogonal linear polarizations and dual orthogonal circular polarizations at 1.98 GHz. Details of the experimental results for the prototype are shown. [ABSTRACT FROM PUBLISHER]

This paper presents a switched smart antenna system, designed to provide a reliable communication between a Center for Integrated Operation of a distributor of electric power and automation devices such as electrical switches remotely controlled. The smart antenna system is controlled by an electronic device which sets de direction of the main lobe of an antenna array to the automation device. [ABSTRACT FROM AUTHOR]

A new planar bow-tie antenna is proposed here for UWB applications. The self-complementary principle has been applied to a planar triangular monopole antenna along with bending the microstrip feed line. The antenna has a wider frequency band compared to the traditional bow-tie antenna, complies with the UWB requirements and it is directly matched to the (SMA) connector via 50Ω microstrip feed line. This antenna has a simple shape which overcomes the complicated matching techniques using baluns or impedance matching sections that are commonly used in bow-tie antennas for widening their limited bandwidths. Another improvement on this new bow-tie antenna is achieved through fractal self-similarity repetition of the triangular shape on each of the patch and its complimentary slot. The simulation results obtained from the CST and HFSS software packages are verified by experimental measurements. [ABSTRACT FROM AUTHOR]

A new compensation method for the mutual coupling of adaptive antenna arrays composed of wire elements is introduced. For the antenna array composed of wire elements, the new compensation method can decouple the terminal voltages with high accuracy for both the 1-D incident signals and 2-D incident signals. The new compensation method is based on the mutual coupling grid and the transient mutual coupling coefficient proposed in this paper. By contrast with the CMIM and RMIM, the new compensation method can provide better compensation for the DOA estimations. Even for the ultra compact antenna array and the incident signals inclined with respect to the azimuth the new compensation method can work well. The numerical results verify the validity and the effectiveness of the new compensation method. [ABSTRACT FROM AUTHOR]

In this paper, a high gain, low side lobe level Fabry Perot Cavity antenna with feed patch array is proposed. The antenna structure consists of a microstrip antenna array, which is parasitically coupled with an array of square parasitic patches fabricated on a FR4 superstrate. The patches are fabricated at the bottom of superstrate and suspended in air with the help of dielectric rods at 0.5?0 height. Constant high gain is obtained by resonating parasitic patches at near close frequencies in 5.725-5.875 GHz ISM band. The structure with 9x9 square parasitic patches with 1.125&lambda0 spacing between feed elements is fabricated on 5&lambda0 x 5&lambda0 square ground. The fabricated structure provides gain of 21.5 dBi associated with side lobe level less than -- 25 dB, cross polarization less than -- 26dB and front to back lobe ratio of more than 26dB. The measured gain variation is less than 1dB and VSWR is less than 2 over 5.725-5.875 GHz ISM band. The proposed structures are good candidates for base station cellular systems, satellite systems, and point-to-point links. [ABSTRACT FROM AUTHOR]

This work presents the results of the synthesis of a lightweight inexpensive reconfigurable planar array antenna. The antenna structure is based on four circular patches. The sources points and some discontinuities on the patches can be electronically reconfigured by means of radio-frequency (RF) switches in order to modify the radiation pattern. In particular, the main lobe could be steered towards a desired direction to obtain an optimal management of wireless resources. An experimental prototype has been realized and tested. Numerical and experimental results are reported and compared to assess the reconfigurable capabilities of the proposed antenna prototype. [ABSTRACT FROM AUTHOR]

This paper presents a novel planar antenna with a reconfigurable radiation pattern. The proposed layout consists of N ≤ 2 monospaced planar bowtie antennas selected one by one by means of a pair of PIN diodes. Experimental results referring to the case of N = 2 and N = 4 are reported and discussed demonstrating the feasibility and effectiveness of the proposed design approach. [ABSTRACT FROM AUTHOR]

An infinitesimal dipole model (IDM) for an antenna including mutual coupling is used to model the radiation patterns of aperiodic arrays. Each radiating element is modelled by a set of infinitesimal dipoles. The mutual coupling between the elements is calculated and the far field radiation pattern of the antenna is computed in a fast and efficient manner. An invasive weed optimisation algorithm is employed to find both the IDMs and the aperiodic array. The simulation results using IDM are verified with a full-wave analysis. [ABSTRACT FROM AUTHOR]

This paper presents the designing of two Swastik-shaped patch antennas operating at 5.8GHz which is designated for IEEE802.11b WLAN communications. The first proposed antenna is designed on a single layer of Rogers RO4350 resulting in a narrowband response of bandwidth 60MHz. The second proposed antenna is designed as two layered (air, Rogers RO4350) structure and has resulted in improved bandwidth. The obtained bandwidth is 210MHz which is 3.5 times of the bandwidth of the first antenna. The antennas are probe feeded. The Ansoft HFSS is employed for designing the antenna [ABSTRACT FROM AUTHOR]

In this paper an approach for indoor localization based on already installed communication transceiver infrastructure is presented. Only marginal additional hardware is required to implement the localization functionality. The idea is to use a power level detection evaluation of the received signals in communication receivers to localize participants. In the planned configuration the power transmitted from mobile terminals is received by a leaky wave cable. Its length and coupling properties are dimensioned according to the dynamic range of two access points connected to the two cable heads. In order to adapt the problem to circuit-based analysis techniques the leaky wave cable is represented by a distributed antenna system. Thereby the considered design consists of a cascade of coupling structures with broadband Vivaldi antennas connected to the coupling ports. An experimental system has been built and also tested using an automated frequency domain measurement setup. Measurement results relating the system bandwidth to positioning accuracy show good agreement with theoretical investigations. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of statistical analysis of the characteristics of an adaptive antenna array tuned by the Hebb algorithm with allowance for the weight-vector fluctuations in the case where signals with different levels of autocorrelatedness of the input-signal readouts arrive at the antenna array. Expressions for the correlation function of the output signal and the power spectral density at the antenna-array output are obtained. It is shown that fluctuations lead to distortions of the output signal of the adaptive antenna array and appearance of additional terms in the formulas for these characteristics. [ABSTRACT FROM AUTHOR]

In this article, a compact design of a flexible planar inverted-F antenna (PIFA) is proposed for triple-band (GSM/DCS/PCS) mobile phone application. The main radiating element of the antenna, which generates the GSM and DCS resonant modes, is printed on a flexible printed circuit board (FPCB) and rolled in a form of cylinder. To improve the construction stability of the antenna, a metallic rod is inserted into the centre of the rolled antenna. The metallic rod acting as a parasitic element of the antenna also generates the PCS resonant mode. The antenna prototype was fabricated and measured. Good agreement between the measurement and simulation results is obtained. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 891–894, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24197 [ABSTRACT FROM AUTHOR]

The capability of non-planar adaptive antennas for suppressing interference in GPS applications is addressed. An optimization problem based on power minimization of incident signals is formulated, resulting in a solution that maximizes the signal-to- interference-plus-noise ratio at the output of the antenna array and subsequently the carrier-to-noise-ratio of a GPS satellite signal. Spherical adaptations of a planar seven element controlled reception pattern antenna array are presented for various low-horizon interference environments. [ABSTRACT FROM AUTHOR]

The diversity gains achievable in the generalised distributed antenna system with cooperative users (GDAS-CU) are considered. A GDAS-CU is comprised of M largely separated access points (APs) at one side of the link, and N geographically closed user terminals (UTs) at the other side. The UTs are collaborating together to enhance the system performance, where an idealised message sharing among the UTs is assumed. First, geometry-based network models are proposed to describe the topology of a GDAS-CU. The mean cross-correlation coefficients of signals received from non-collocated APs and UTs are calculated based on the network topology and the correlation models derived from the empirical data. The analysis is also extendable to more general scenarios where the APs are placed in a clustered form due to the constraints of street layout or building structure. Subsequently, a generalised signal attenuation model derived from several stochastic ray-tracing-based pathloss models is applied to describe the power-decaying pattern in urban built-up areas, where the GDAS-CU may be deployed. Armed with the cross-correlation and pathloss model preliminaries, an intrinsic measure of cooperative diversity obtainable from a GDAS-CU is then derived, which is the number of independent fading channels that can be averaged over to detect symbols. The proposed analytical framework would provide critical insight into the degree of possible performance improvement when combining multiple copies of the received signal in such systems. [ABSTRACT FROM AUTHOR]

A combined antennas and propagation study has been undertaken with a view to directly improving link conditions for wireless body area networks. Using tissue-equivalent numerical and experimental phantoms representative of muscle tissue at 2.45 GHz, we show that the node to node |S21 path gain performance of a new wearable integrated antenna (WIA) is up to 9 dB better than a conventional compact Printed-F antenna, both of which are suitable for integration with wireless node circuitry. Overall, the WIA performed extremely well with a measured radiation efficiency of 38% and an impedance bandwidth of 24%. Further benefits were also obtained using spatial diversity, with the WIA providing up to 7.7 dB of diversity gain for maximal ratio combining. The results also show that correlation was lower for a multipath environment leading to higher diversity gain. Furthermore, a diversity implementation with the new antenna gave up to 18 dB better performance in terms of mean power level and there was a significant improvement in level crossing rates and average fade durations when moving from a single-branch to a two-branch diversity system. An Antennas and Propagation Approach to Improving Physical Layer Performance in Wireless Body Area Networks [ABSTRACT FROM AUTHOR]

A method for scanning of the main beam of phased array antennas in a wide angular range is presented. The method utilizes several smaller flat antenna panels, arranged in an array of panels, each of the panels pointed in the direction of the main beam of overall antenna. The output signal of the overall antenna is summation of the signals from all antenna panels. Investigation of the array performance of such structure with respect to the distance between the panels and sidelobe level of the antenna structure is presented. [ABSTRACT FROM AUTHOR]

A modification of the synthetic-plane-wave-based holographic technique for determining radiation patterns and aperture fields of medium-gain horn antennas is proposed. The modification is based on using both the sum and difference of the near field and reference signals to form the hologram via simple low-cost amplitude-only near field measurements. This approach when compared to the previous version, where only the sum signal is used, allows increased sample spacing, and also provides an improvement in quality of the final results. The effectiveness of the modified technique is confirmed by both calculated and measured results obtained for pyramidal and conical horn antennas at 10 GHz frequency. [ABSTRACT FROM AUTHOR]

A generalized method for the analysis of microstrip antennas, which are placed on or embedded in hemispherical multilayer structures, is presented. By using corresponding full-wave equivalent circuits, the dyadic Green's functions of these structures and their system equations for the tangential field components at the interfaces can be analytically derived in a simple way. The numerical results are verified with commercial software codes. Some effects of the curvature and the ground plane on the input impedance of microstrip antennas are shown. [ABSTRACT FROM AUTHOR]

A new technique is proposed to increase the bandwidth (BW) of a Z-Iike slot antenna for operation at 2.4 GHz and 5GHz, over the industrial-scientific-medical (ISM) bands and the Hiperlan2 bands. By splitting two side slots of the Z-like slot antenna into two or three fingers, several additional resonances can be created. After careful optimization of the geometrical parameters of the antenna, the resonances are merged and thus a wide impedance bandwidth is obtained. [ABSTRACT FROM AUTHOR]

In handheld communications devices there is not much room for the placement of antennas. This problem is exacerbated when more than one antenna is needed for use in a MIMO communications system. It is then useful to be able to utilize some of the existing device structure to form the required antennas. In this article, we show how the characteristic mode theory can be used to achieve this in a way that results in antennas with the low envelope correlation preferred for MIMO antennas. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1724–1727, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23509 [ABSTRACT FROM AUTHOR]

In this letter, the design of a planar antenna compliant with FCC requirements for ultra-wideband (UWB) transmission systems is described. With reference to a planar geometry on a dielectric substrate, the shape of the antenna is described by means of a spline-based representation and it is determined by means of an optimization process aimed at finding the optimal descriptive parameters that allow to fit the user-defined electrical and dimensional requirements. The reliability and effectiveness of the antenna prototype are assessed through simulations as well as experimental measurements. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1975–1978, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23519 [ABSTRACT FROM AUTHOR]

A cost-effective approach for initialisation of an adaptive antenna based on the constant modulus algorithm (CMA) is proposed. The technique utilises 1 bit phase shifters and a power detector, which are normally integrated with a multibeam antenna, to determine the maximum power beam direction. Consequently, the beam is exploited as an initial beam for CMA. Development of hardware-assisted initialisation is discussed. In addition, field programmable gate array implementation of a CMA processor and associated control circuitry is presented. Several simulations are performed to evaluate the performance of the proposed initialisation technique. In addition, the developed prototype is tested with a phase array antenna designed for operation at the IMT2000 frequency of 1.95 GHz. Experimental results confirm superiority of the proposed technique. [ABSTRACT FROM AUTHOR]

An electronically tunable broadband E-shaped patch antenna (ESPA) is proposed and analyzed using equivalent circuit concept. The effects of notch parameters such as notch length, width, and position are analyzed to select the optimum values for broadband operation of ESPA. Under the optimum conditions of ESPA, the effect of bias voltage of tunnel diode on the performance of the antenna is also analyzed. The theoretical investigations of the proposed antenna reveal that the tunable band of operation between 1.055 GHz (bandwidth 42.54%) and 1.324 GHz (bandwidth 49.77%) can be achieved by adjusting the bias voltage only. It is noted that the radiative power of the proposed antenna can be enhanced up to 5.67 dB as compared with the E-shaped patch antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1341–1347, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23362 [ABSTRACT FROM AUTHOR]

A two-element diversity planar antenna for a multiple-input multiple-output application is proposed. By adopting two Y-shaped radiators, the antenna provides wideband impedance matching characteristics over the desired frequency band. To reduce the mutual coupling between two radiating elements, three stubs are inserted in the ground plane. Good impedance matching and improved isolation characteristics are observed. The measured impedance bandwidth of the proposed antenna ranges from 2.27 GHz to 10.2 GHz for a return loss of less than 10 dB. Parametric analysis has been conducted to investigate the effect of radiator length and the insertion of stubs on the impedance bandwidth and isolation characteristics. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1352–1356, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23389 [ABSTRACT FROM AUTHOR]

A broadband differential fed integrated antenna operating between 0.9 and 2.3 GHz suitable for future software defined radios is presented in this article. Two distributed amplifiers in push-pull configuration are connecting directly to a modified differential fed bow-tie antenna, which also performs the dual function of signal combining and radiation. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1320–1324, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23384 [ABSTRACT FROM AUTHOR]

A design scheme of a quarter-band internal antenna is proposed for use in GPS, UMTS/WCDMA, ISM, and SDMB bands. The folded metal plates of the three branches are mounted on a dielectric-coated ground plane for size miniaturization and durability. For a multiband operation the sectional antenna corresponding to each band was designed, combined, and finally trimmed. The return loss of the suggested antenna was calculated by a commercial HFSS simulator and the results are compared with measured return loss, which shows a good agreement between them. Gain and radiation pattern are also measured by the field measurement system in an anechoic chamber. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1227–1232, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23345 [ABSTRACT FROM AUTHOR]

A metamaterial spacer to decorrelate two closely spaced antennas has been designed and tested. The metamaterial spacer exhibits an artificial magnetic conductor (AMC) behavior around 2.6 GHz. Its performance has been checked against a simple metal spacer (PEC), providing a quasi orthogonal radiation pattern and good results in terms of decoupling and decorrelating a two-antenna system. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1414–1417, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23365 [ABSTRACT FROM AUTHOR]

The phase of the elements of a phased array feed are optimized to yield a maximum directivity for front fed and offset cylindrical parabolic reflector antennas. Calibration improves the reflector antenna performance, especially for front fed reflectors with larger feeds. [ABSTRACT FROM AUTHOR]

B ackscatter radio systems, including high frequency radio frequency identification (RFID), operate in the dyadic backscatter channel-a two-way pinhole channel that has deeper small-scale fades than that of a conventional one-way channel. This paper shows that pinhole diversity is available in a rich scattering environment caused by modulating backscatter with multiple RF tag antennas-no diversity combining at the reader, channel knowledge, or signaling scheme change is required. Pin- hole diversity, along with increased RF tag scattering aperture, can cause up to a 10 dB reduction in the power required to maintain a constant bit-error-rate for an RF tag with two antennas. Through examples, it is shown that this gain results in increased backscatter radio system communication reliability and up to a 78% increase in RF tag operating range. [ABSTRACT FROM AUTHOR]

A novel design of trapeizform U-slot folded patch feed antenna is presented in this paper. It is optimized by an evolutionary based optimization scheme which is capable of producing an antenna design that has a wide impedance bandwidth but small in dimension size. The optimized design was also experimentally verified by its hardware prototype in which 101.3% measured impedance bandwidth (VSWR ⩽ 2) was obtained compared with its simulated bandwidth of 104%. Also, both the effectiveness of the optimization methodology and the proposed antenna configuration have been justified through comparison results. [ABSTRACT FROM AUTHOR]

We present a novel wideband multiple-input, multiple-output (MIMO) channel model, which we refer to as the structured model. The structured model is based on the eigenvalue decomposition (EVD) of the wideband channel correlation matrix. It does not assume the scatterers at the receiver fade independently of those at the transmitter. It also models correlation between delay bins in the power delay profile (PDP). With preliminary data gathered using McMaster's wideband MIMO Software Defined Radio (the WMSDR) in fixed outdoor locations, and Brigham Young University's (BYU) wideband channel sounder in fixed indoor locations, we show good agreement between modeled and measured data. The two platforms used and the environments in which the data were collected were very different. The proposed model performed equally well with both data sets, demonstrating its robustness. [ABSTRACT FROM AUTHOR]

We report measurements of the capacity of a 2.4 GHz vertically-polarized 3 x 4 multiple-input multiple-output (MIMO) system in which both ends of the wireless link are located in a hallway. This scenario is of interest due to the increasing mobility of wireless devices, and because hallways have previously been re- ported to create difficulties for MIMO propagation. In this paper we focus on the variation in capacity as a function of position as one side of the wireless link is moved laterally (i.e., vertically and horizontally) in the hallway. We find not only significant degradation in MIMO capacity due to rank collapse, but also identify considerable variability due to changes in the signal strength. The capacity along a vertical cut is found to be relatively constant about 7.5 ± 1 bpsfHz for a reference signal-to-noise ratio (SNR) of 10 dB at a range of 12 m, which is significantly less than the ideal maximum of 11.5 bps/Hz. The capacity along a horizontal cut is found to be about 6.7 ± 3 bps/Hz under the same conditions, dominated by a large-scale signal strength variation which can be attributed to identifiable propagation mechanisms. We also consider the performance relative to simpler rank-1 (diversity/beamforming) schemes, with and without channel state information. [ABSTRACT FROM AUTHOR]

A scattering technique for measuring reactive antenna input impedance is described. The antenna scattering is measured with three different loads: an open circuit, a conjugate match, and a reactive match. The load reactances tune the antenna into resonance at the measurement band. Theory and error considerations are presented, as well as measurement results of two ultra high frequency radio frequency identification antennas. The measurements were performed in a gigahertz transverse electromagnetic mode cell. The measured impedances are within about 10% of the simulated values for a dipole-like antenna. The results of a planar inverted-F antenna are somewhat more complex, but also supported by the presented simulations and the coaxial impedance measurement results. [ABSTRACT FROM AUTHOR]

A method of moments model is presented to analyze Archimedean spirals that are printed on a layered dielectric sphere. The model is derived assuming an arbitrary location of the spiral. Input impedance, current distribution and far-field results are presented and are shown to be in good agreements with other methods. [ABSTRACT FROM AUTHOR]

A differentially fed rectangular dielectric resonator antenna (DRA) is studied using the finite-difference time-domain (FDTD) method. The fundamental TE111 mode of the rectangular DRA is excited at 2.4 GHz, with a 10-dB differential impedance bandwidth (ISddljI < -10 dB) of 10.4%. To verify the theory, measurements were carried out, and reasonable agreement between theory and experiment is obtained. The effects of the magnitude and phase imbalances on the DRA impedance and radiation pattern are investigated. [ABSTRACT FROM AUTHOR]

A new, low-cost, switched-beam and fully adaptive antenna array suitable for 2.4 GHz ISM applications is proposed in this paper. The array comprises of four elements, equal in number receiving RF and IF components, as well as a microcontroller based unit which is responsible for the control of the array. The array is designed with the aid of a custom genetic algorithm, while measurements results are presented indicating consistency between design and implementation. In addition, multipath fading mitigation capability of the array is demonstrated via channel measurements results. [ABSTRACT FROM AUTHOR]

A compact pattern-reconfigurable planar fractal antenna is presented. Simulated and measured results showed that four switchable directional patterns, covering ranges from 300° to 360° and from 0° to 60° in the x-z and y-z planes, respectively, could be obtained around 8.4 GHz. The return losses were better than 10 dB. Finally, the pattern reconfigurability of the planar fractal antenna is described by means of a characteristic-mode analysis. [ABSTRACT FROM AUTHOR]

This paper is focused on using plasma as a substitute for metal in a frequency selective surface (‘FSS’). FSSs have been used for filtering electromagnetic waves. Each FSS layer has to be modeled using numerical methods, and the layers are stacked in such a way to create the desired filtering. Genetic algorithms are used to determine the stacking needed for the desired filtering. This is a complicated and numerically expensive process. We developed a method to replace metal in an FSS with plasma elements. Our plasma FSSs can be tuned to a desired filtering by varying the density in the plasma elements. This could save much of the routine analysis involved in the standard analysis of the conventional FSS structures. The user simply tunes the plasma to get the desired filtering. Plasma elements offer the possibility of improved shielding along with reconfigurability and stealth. Plasma FSS can be made transparent by turning the plasma OFF. This extends our previous scientific achievements in the development of the plasma antenna. [ABSTRACT FROM AUTHOR]