A compact quad band slot antenna with high isolation suitable for multiple-input–multiple-output (MIMO) applications is developed. The quad bands are achieved by introducing slots in a modified, size reduced circular patch antenna. The single-antenna element consists of a substrate sandwiched between a modified circular patch with F shape slot, a feeder line and a via running between the radiating patch and the feeder line. The proposed design resonates at the frequencies of 1.8 GHz (1.7–1.88 GHz), 3.6 GHz (3.50–3.76 GHz), 5.4 GHz (5.25–5.38 GHz), and 7.2 GHz (7.15–7.35 GHz) covering the GSM II, WIMAX, wireless local area network (WLAN), and C-band applications, respectively. The independent tuning of frequency bands is achieved by varying the length of the slots. Orthogonally placed two- and four-element MIMO antenna system are fabricated, tested, and the measurement results are presented. The separation between each element is reduced to 0.085λ while introducing slotted and pulsed stubs to improve isolation between elements. A detailed analysis, including mutual coupling, low correlation, diversity gain, and total array reflection coefficient had been reported. The two- and four-element MIMO antennas achieved correlation as low as 0.005, mutual coupling ≤−15 dB, and diversity gain nearly 10 dB.

A novel design of compact and light-weight horn mounted cylindrical dielectric resonator antenna (CDRA) fed by substrate integrated waveguide (SIW) resonator has been investigated for high gain and multiband applications. SIW resonator contains two closely spaced longitudinal slots of equal length and unequal width to excite the CDRA. These slots are responsible for introducing triple resonating bands. The excited mode in dielectric resonator by longitudinal slots is EH11δ mode. The achieved impedance bandwidths are 65, 180, and 240 MHz at resonant frequencies 9.78, 10.58, and 11.84 GHz, respectively, for |S11| <−10 dB. Copper-taped horn enhances the gain of antenna more than 2 dB for all resonating bands. The measured peak value of gain is 9.3 dBi at ~11.84 GHz.

In this work, multi-mode resonator technology is applied to finline bandstop filter (BSF) to improve its performance. A finline BSF with two transmission zeros in the stopband is realized by using a new kind of dual-mode finline resonator proposed in this paper. The bandwidth of the designed filter is clearly broadened to three times that of the traditional finline BSF without enlarging its size. Its measured bandwidth under 20 dB rejection is about 600 MHz and the insertion loss in the passband is below 0.4 dB including the insertion loss of two finline-to-waveguide transitions. There is a good agreement between the simulated and measured results.

A planar circularly polarized (CP) monopole antenna (MA) with dual-band operation for the IEEE 802.11a/b/g wireless local area network (WLAN) is proposed. By introducing dual strip-sleeves shorted at the ground plane, the excitation of dual-resonant modes can resemble the 2.4/5.2 GHz bands required for WLAN operations. The obtained impedance bandwidths (RL ≧10 dB) across the operating bands approach 260/988 MHz and the 3 dB axial-ratio bandwidth of about 103/710 MHz for 2.4/5.2 GHz bands, respectively. The model proposed in this study reflects more advantages in physical implementation as its overall volume is only 40 × 40 × 0.8 mm3, 22% smaller than other conventional CP MAs. The measured peak gain and radiation efficiency are about 4.1/3.3 dBic and 94/84%, respectively, and demonstrate nearly bidirectional patterns in the XZ- and YZ-planes.

This paper shows the contribution of slow-wave coplanar waveguides on the performance of power amplifiers operating at millimeter-wave frequencies in CMOS-integrated technologies. These transmission lines present a quality factor Q two to three times higher than that of the conventional microstrip lines at the same characteristic impedance. To demonstrate the contribution of the slow-wave transmission lines on integrated millimeter-wave amplifiers performance, two Class-A single-stage power amplifiers (PA) operating at 60 GHz were designed in standard 40 nm CMOS technology. One of the power amplifiers incorporates only the microstrip lines, whereas slow-wave coplanar transmission lines are considered in the other one. Both amplifiers are biased in Class-A operation, drawing, respectively, 22 and 23 mA from 1.2 V supply. Compared to the power amplifier using conventional microstrip transmission lines, the one implemented with slow-wave transmission lines shows improved performances in terms of gain (5.6 dB against 3.3 dB), 1 dB output compression point (OCP1dB: 7 dBm against 5 dBm), saturated output power (Psat: >10 and 8 dBm, respectively), power-added efficiency (PAE: 16% instead of 6%), and die area without pads (Sdie: 0.059 mm2 against 0.069 mm2).

A modified compact Y-junction substrate-integrated waveguide (SIW) four-way power divider (PD)/combiner is proposed in this paper. The proposed approach is based on the traditional Y-junction waveguide. By using direct transition structure from SIW to half-mode SIW, four-way PD that provides equal power split to all four output ports is achieved. The even- and odd-mode equivalent circuits are given to analyze and design the PD. The measured results validate the proposed design methodology and show good agreement with the simulation results. The measured 17 dB return loss bandwidth and 1.2 dB insertion loss bandwidth of this four-way PD are both about 2.5 GHz.

This paper describes a method to analyze open or closed elliptical structures with constant axial ratio by a Body-of-Revolution (BoR) Finite Element Method (FEM). The method is based on Transformation Optics, a coordinate transformation that maps the elliptical shape to a circular shape, for which BoR-FEM represents a greatly efficient tool for the analysis.

In this paper, material selection has been done for dielectric substrate material in microstrip patch antenna (MPA) for three distinct classes of wireless communication applications using Ashby's approach. This material selection procedure is based on the creation and evaluation of Ashby's chart of different material indices. These material indices in turn affect the device performance indices, which decide the best possible dielectric material to be used as substrate for MPAs. In this work, quality factor, relative permittivity, and temperature coefficient of resonant frequency are chosen as material indices of MPA's dielectric substrate to get relevant performances. Ashby's selection chart shows that 0.75MgAl2O4–0.25TiO2 material for millimeter waves applications, Ca[(L1/3Nb2/3)0.85Ti0.15]O3−δ for mobile base station applications, and (Ba0.95Ca0.05)O–Sm2O3–4.5TiO2 ceramic for mobile phone miniaturization applications are the promising materials that allows best overall performance in MPAs for wireless communication.

This paper presents a hardware efficient receiver architecture, to be used in low-cost, ultra-high rate 60 GHz wireless communication systems. The receiver utilizes a simple, feed-forward carrier recovery concept, performing phase and frequency synchronization in the analog domain. This enables 1-bit baseband processing without a need of ultra-high speed and high precision analog-to-digital conversion, offering a strong simplification of the system architecture and comparatively low power consumption. In a first prototype implementation, the receiver is realized in a low-cost SiGe technology as two separate ICs: the 60 GHz/5 GHz downconverter, and the intermediate frequency synchronous demodulator. The simple synchronous reception concept is experimentally validated for up to 3.5 Gbit/s data rate, which constituted the limit of the existing experimental setup. Furthermore, the downconverter demonstrates that low-cost technologies (fop/fmax ~ 0.75) can be used to realize short-range data links at 60 GHz, with low-noise amplifiers in a more performant technology as needed.

The paper has proposed a multilayer, polarization rotation featured, low radar cross-section (RCS) antenna using electromagnetic band-gap (EBG)-based frequency selective surface (FSS) at 8.25 GHz. Cross-shaped EBG unit cells offer zero reflection phase and −25 dB reflection magnitude at 8.25 GHz. The FSS layer consists of eight cross-shaped EBG unit cells sandwiched between two substrates to offer high absorptivity at the desired band. The circular patch antenna resonating at 8.25 GHz is placed on the top substrate having a lower dielectric constant. Four circular-shaped patches are etched at the four corners of the top layer and are coupled with two feed lines which are aligned 90° to each other at the bottom layer and interconnected diagonally to achieve polarization rotation. The proposed antenna offers a gain of 6.72 dB and an in-band RCS of −21.4 dBsm. Incident energy is backscattered into eight directions separated by angle ϕ = 45°. The proposed antenna has the RCS reduction band of 7.7–9.4 GHz. It offers normalized polarization rotation ratio more than 0.8 within the −40° to 40° angular region at the frequency band 8–8.5 GHz. The measured result using the fabricated prototype agrees well with the simulated one.

In this paper, a triple-band bandpass filter using a multi-mode half-mode substrate integrated waveguide (HMSIW) cavity is presented. In this design, back-to-back connected half-mode defected ground structure (DGS) is loaded into the HMSIW cavity, which generates the first passband. The first four modes of HMSIW cavity are TM110, TM120, TM310, and TM320. They have been used to generate second and third passbands. The slot line perturbation is used to shift the modes close to each other. Here, TM110 and TM120 constitute second passband, and TM310 and TM320 give third passband. Moreover, the notch band is designed using embedded open-circuited stub to improve the attenuation between the second and third passbands. The proposed filter is designed and fabricated on RT/Duroid 5880 substrate with a thickness of 0.508 mm. The measured results are in line with simulated ones for each of the passbands, and the center frequencies are 6.28, 13, and 19.12 GHz.

This paper presents and discusses several methods for predicting the low-frequency (LF) noise at the output of a mm-wave detector. These methods are based on the extraction of LF noise source parameters from the single diode under a specific set of bias conditions and the transfer or conversion of these noise sources, under different operating conditions including cyclostationary regime, to the quasi-dc output of a mm-wave detector constructed with the same model of diode. The noise analysis is based on a conversion-matrix type formulation, which relates the carrier noisy sidebands of the input signal with the detector output spectrum through a pair of transfer functions obtained in commercial software. Measurements of detectors in individual and differential setups will be presented and compared with predictions.

The contribution of this paper is to propose a novel rat-race hybrid coupler of arbitrary coupling coefficient. Traditionally, the rat-race hybrid couplers are built by various loop-alike transmission-lines of multiple quarter-wavelength, and in this paper, we approach the coupler design by using a circular substrate integrated waveguide (SIW) cavity (SIWC). The employed SIWC supports two mutually orthogonal degenerate modes, and cavity field is formed by the two modes in an arbitrary weighting ratio which defines the proposed rat-race coupler's coupling coefficient. The cavity is excited by a microstrip combined coupling slot with the microstrip along a specifically chosen direction. The energy of each degenerate mode can be solely extracted by an associated subminiature version A (SMA) whose position is carefully determined. The isolation between the coupling slots is assured by their perpendicular layout, and the isolation between the SMA probes is obtained by the orthogonality of the two degenerate modes. Experiments are conducted on the 3- and 10-dB coupling coefficient samples to verify this novel rat-race coupler design. The measurements agree well with the simulations, and circuit's good performance is observed in terms of coupling precision, isolations, and small phase imbalances.

Based on vector network analyzer Measurements, a model for the specular reflection behavior of printed circuit boards in the Terahertz range has been derived. It has been calibrated to suit the behavior of the measurements using a simulated annealing algorithm. The model has been tailored for integration to ray-tracing-based propagation modeling.

This paper reports an investigation and a proposed solution to design Class E power amplifiers above the theoretical maximum frequency allowed by the adopted active device. Starting from the traditional time domain analysis, a numerical algorithm has been developed and presented in order to extend Class E feasibility through the optimization of the output voltage waveform. A hybrid Class E amplifier in laterally diffused metal oxide semiconductor (LDMOS) technology has been designed and measured. The final amplifier shows an output power of more than 10 W with an associated efficiency of 49% (power added efficiency (PAE) = 45%) over a 100-MHz bandwidth around 2.14 GHz.

We investigate the frequency diverse array (FDA) for joint radar and communication systems. The basic idea is to use the transmitter/receiver modules of the radar system for communication purpose during listening mode as a secondary function. The radar will be performing its routine functions during the active mode as a primary function. An FDA at the transmitter side will be used to produce an orthogonal frequency division multiplexed signal, which is proposed for the communication system. The directivity of the radar antenna, FDA in this case, provides an additional advantage to mitigate the interferences other than the Direction of Interest (DoI). The proposed technique allows two beampatterns to be transmitted sequentially from the same FDA structure. Due to the communication signal transmission in the mainlobe of the second beampattern, the bit error rate achieved in the mainlobe is better than the existing techniques using the sidelobe transmission for communications. At the receiver, both incoming signals of radar and communication will share a different spatial angle. Simulation results indicate the novelty of the idea to suppress the interferences in terms of DoI. Furthermore, we analyzed the signal-to-interference ratio and Cramer–Rao lower bounds for angle and range estimation for the proposed technique.

This paper proposes a microstrip antenna with reduced in-band and out-of-band radar cross-section (RCS) by subtracting the area of weak scattered current on the ground plane. Fourteen square slots were subtracted from the ground plane, reducing in-band and out-of-band RCS while maintaining radiation performance. Modified and reference antenna surface current distributions were simulated and analyzed in radiating and scattering modes. Two antenna prototypes were fabricated and measured to verify the simulation. The proposed antenna RCS was reduced compared with the reference antenna in the frequency range 1–4.4 GHz, including in-band and out-of-band frequency bands. Maximum in-band and out-of-band RCS reduction was 16.3 dBsm at the working frequency, and 19.3 dBsm at 3.4 GHz, respectively

In the present paper, we present a dynamic gate biasing technique applied to a 10 W, S-band GaN amplifier. The proposed methodology addresses class-B operation of power amplifiers that offers the potential for high efficiency but requires a careful attention to maintain good linearity performances at large output power back-off. This work proposes a solution to improve the linearity of class-B amplifiers driven by radio frequency-modulated signals having large peak to average power ratios. An important aspect of this work concerns the characterization of the dynamic behavior of GaN devices for gate bias trajectory optimization. For that purpose, the experimental study reported here is based on the use of a time-domain envelope setup. A specific gate bias circuit has been designed and connected to a 10 W – 2.5 GHz GaN amplifier demo board from CREE. Compared to conventional class-B operation with a fixed gate bias, a 10-dB improvement in terms of third-order intermodulation is reached. When applied to the amplification of 16-QAM signals the proposed technique demonstrates significant ACPR reduction of order of 6 dB along with error vector magnitude (EVM) improvements of five points over 8 dB output power back-off with a minor impact on power-added efficiency performances.

A polar transmitter driven by digital input signals for envelope and phase is demonstrated, using a band-switching output resonator to achieve multiband operation. A new digital pulse width modulation algorithm is also shown to partially suppress spurious signals associated with the digital input envelope signal. The transmitter consists of a current-mode class-D (CMCD) CMOS power amplifier (PA), together with a buck converter with a dead-time generator for improved efficiency. The CMCD PA is tuned by band-switching capacitors that can handle up to 9 V, and is measured to have approximately 30 dBm output power with 31–35% drain efficiency under single-tone testing. The proposed spurious signal reduction technique works to partially suppress quantization noise without increasing power consumption. Overall efficiencies of 27.1/25.6% are obtained at 30.2/28.9 dBm continuous wave (CW) output powers and 0.85/1.75 GHz carrier frequencies, respectively. Spur suppression of 9–10 dB peak is achieved when the proposed algorithm is applied with wideband code division multiple access (WCDMA) modulation.

In this paper, an array antenna with asymmetric antenna fed network is presented. Total size of the proposed array antenna (with 2 × 2 elements) is 90 × 90 mm2 and distance between elements (fed by fed) is λ0/2 (λ0 = wavelength in free space). The proposed antenna is fed by coaxial cable that isolated input impedance from impedance of the array antenna feed network. The measured impedance bandwidth of the coaxial fed circular polarization array (S11 < −10 dB) is 47.9% from 4.6 to 7.5 GHz (1.63:1), and the measured 3-dB axial-ratio bandwidth is 42% from 4.7 to 7.2 GHz. The peak gain of antenna is 9.1 dBic.