This paper, following up on the previous work, investigates the effect of the input coupler's load termination of a balanced amplifier in a beam-steering system. The noise generated in this load termination deteriorates the amplifier noise resistance, which increases the noise temperature due to a varying active reflection coefficient at the antenna ports as a function of scan angle. In reducing this effect, the balanced configuration is made more favorable for radio astronomy applications. By lowering the value of the impedance termination on the fourth port of the quadrature coupler an improvement in noise temperature sensitivity is achieved at the cost of reduced power matching.

Large-signal (L-S) characterization of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on silicon designed to operate at different millimeter-wave (mm-wave) and terahertz (THz) frequencies up to 0.5 THz is carried out in this paper using an L-S simulation method developed by the authors based on non-sinusoidal voltage excitation (NSVE) model. L-S simulation results show that the device is capable of delivering peak RF power of 657.64 mW with 8.25% conversion efficiency at 94 GHz for 50% voltage modulation; whereas RF power output and efficiency reduce to 89.61 mW and 2.22% respectively at 0.5 THz for same voltage modulation. Effect of parasitic series resistance on the L-S properties of DDR Si IMPATTs is also investigated, which shows that the decrease in RF power output and conversion efficiency of the device due to series resistance is more pronounced at higher frequencies especially at the THz regime. The NSVE L-S simulation results are compared with well established double-iterative field maximum (DEFM) small-signal (S-S) simulation results and finally both are compared with the experimental results. The comparative study shows that the proposed NSVE L-S simulation results are in closer agreement with experimental results as compared to those of DEFM S-S simulation.

The microstrip active patch antenna behaves like a resonant circuit/cavity with multiple resonant frequencies; furthermore, depending on the non-linearity of the device, it generates significant amount of second harmonic radiation. The location of the device on the patch that maximizes the fundamental radiated power output is found to be not the position corresponding to the minimum second harmonic content in radiated power. An optimum location of the diode on the patch has been suggested. The paper also discusses the modification of the behavior of the active antenna, which is first an oscillator; and then a radiator, under injection-locked condition. The results are presented with respect to a Gunn-mounted rectangular patch.

This paper presents a close but a beginner's perspective and a comprehensive review of microstrip filters with defected ground structure (DGS). The concept of DGS is inspired by photonic/electromagnetic bandgap structures (EBG/PBG) and metamaterials that are employed in microwave components to achieve a variety of performance enhancement features. Modeling of DGS and metamaterials as an L-C equivalent lumped circuit is much simpler in comparison with complex EBGs/PBGs. In this review, we have given a detailed account of the microstrip filters using DGS.

This paper presents a detailed procedure to design substrate integrated waveguide (SIW) Tee-junctions with wide-range split-power ratio (from 1:1 to 1:8) and phase-balanced outputs. A set of curves was generated using an electromagnetic (EM) simulator to graphically determine the required parameters for the desired junction. Since such curves are provided, no further electromagnetic simulation is required when applying the proposed method. Input return loss at central frequency is guaranteed to be better than 18 dB. If an optimization procedure is required, the parameters obtained from this methodology may be used as initial values for such a process. Moreover, design rules are given for implementing 1 → 2N unequal power dividers with phase-balanced outputs. To demonstrate the accuracy of the proposed graphical method, three implementation examples are provided: two Tee-junctions and a 1 → 4 power divider.

An analytical model is presented to improve the performance of the equilateral triangular microstrip antenna (ETMA). An improved model is presented taking into account the insertion of an air gap between the substrate and the ground plane, and High Tc superconducting material (HTS) for the triangular patch. The full-wave spectral domain technique in conjunction with the complex resistive boundary condition is used to calculate the characteristics including resonant frequencies, bandwidths, and radiation efficiency. Numerical results for the air gap tuning effect on the operating frequency and bandwidth of the high Tc superconducting triangular microstrip antenna (HTSTMA) are presented. The effect of temperature on resonant frequency and bandwidth of the HTSTMA are also given. The computed data are found to be in good agreement with results obtained using other methods.

Simple internal multiband monopole antenna with low specific absorption rate (SAR) for most wireless communication applications is presented in this paper. The proposed antenna is an unequal arms monopole antenna with a meander stripoin the other substrate side. The antenna has a simple structure and it is sufficiently small in size to be easily fitted on the housing of a mobile phone or a universal serial bus (USB) dongle with size 20 × 50 × 0.8 mm3. The antenna is designed to operate in different bands to cover most of allocated wireless communication bands in the frequency range from 0.9 to 6 GHz. The proposed antenna has an acceptable average gain of about 2.75 dBi and an average efficiency of about 85% while providing a monopole radiation pattern in both horizontal and elevation planes, with average half-power beam width of 65° in the elevation plane. The simulation and the experimental results of the antenna are in agreement. The SAR in the human head is investigated by using CST 2012 Microwave Studio Hugo Voxel Model.

Detailed analysis of the polarization tracking modules for Ku band active phased array antennas is presented. The proposed transmitter (14.0–14.5 GHz) and receiver (12.25–12.75 GHz) modules are based on the low temperature co-fired ceramic (LTCC) technique, containing orthogonal dual channels with different phases controlled by phase shifters. The effect of amplitude and phase inconsistency between two channels on polarization tracking performance is analyzed. The validity of the analysis is verified by the measurements of the manufactured prototypes. The measured patterns of the active phased array antenna are given to illustrate the effects of the modules on polarization agility, which may be used for Ku band satellite antennas on mobile terminals.

A waveguide shunt slot-fed microstrip patch antenna (WGMPA) element is proposed and analyzed with method of moments (MOM) using entire-domain basis functions. The developed analysis has been utilized to obtain parametric observation of power-coupling versus transverse offset of feeding slot from the waveguide axis. Expressions for the radiation pattern as a summation of contributions of individual basis functions are reported. The proposed element is amenable to building-up series-fed linear arrays by a simple cascading of elements at the through-end of the feeding waveguide. The authors propose that arbitrary amplitude excitations may be applied to such linear arrays for desired tailored array pattern characteristics. The required transverse offsets for each array element may be computed using the reported parametric result. As a demonstration of concept, two distributions are designed – uniform amplitudes and Dolph–Chebyshev for reduced side lobes. Computed element patterns from MOM are used with an array factor formulation for arbitrary element positions. Both modules show radiation characteristics closely matching the expected directivity and sidelobe envelopes. Analysis validation is achieved using a proven finite element method (FEM)-based solver; the comparison is close and is reported. Efficacy of the waveguide shunt-slot fed patch element for building linear array modules with prescribed amplitude distributions is thus established.

This paper presents a new approach for improving the localization of passive ultra high frequency radio frequency identification (RFID) tags in line-of-sight channels using a received signal strength indicator (RSSI) technique. In practice, the complex propagation in the indoor channels and also the variability of some parameters of the RFID equipment itself introduces significant amount of errors when the operation of localization carries out the RSSI technique. Indeed, as the calculation is based on a trilateration, the incomplete knowledge of the propagation and some parameters of RFID tags leads to estimate distances which are wrong, and therefore the localization cannot be correct. In order to overcome this drawback, the proposed method takes into account the presence of unknown parameters relying on a dichotomous algorithm which includes probabilistic parameters. The presented simulation results are in good agreement with the expected theoretical results. Experimental results show that the proposed method strongly increases the accuracy of the estimated position of tags. Compared to other approaches based on the improvement of the RSSI technique, this method does not require too much complexity in terms of materials (no need for specific architecture or reference tags) and processing (fast and simple algorithm).

Broadcasting is an inevitable operation in networks. This paper addresses the issues related to broadcasting such as node interference and latency delay in ad-hoc networks .These problems could be overcome by our proposed algorithm approximate directional routing protocol (ADRP) which is mainly inspired by the existing on-demand directional routing protocol (DRP). DRP is also similar to Dynamic Source Routing (DSR). The use of directional antennas for broadcasting is gaining acceptance in ad-hoc networks. The key benefits of smart antennas are minimum energy consumption and bandwidth conservation. Although excess of literature is directed toward the use of smart antennas, a powerful protocol for reducing redundancy, end-to-end delay, and interference is being researched. One such protocol is ADRP. ADRP is a reactive protocol that combines the effect of DRP and approximation algorithm that finds optimal solution for broadcast problems. Omni-directional antennas are capable of wide angle signal transmission. Compared with omni-directional antennas, its successor directional antennas have come up with significant advantages of reducing packet redundancy and interference by gaining higher signal-to-noise ratio. The duo pack will considerably decrease end-to-end delay and node interference giving out significant performance benefits thereby substantially increasing throughput.