LInear amplification using Non-linear Components (LINC) is an architecture that achieves linear power amplification for radio-frequency (RF) transmitters. This paper describes the impact of RF power amplifiers (PAs) class on the overall system performances. The linearity and efficiency of the LINC transmitter with different PA classes (AB, B, C, D, E, F, F−1, and J) are evaluated and compared, in terms of error vector magnitude (EVM), adjacent channel leakage ratio (ACLR), and power added efficiency (PAE), for a 16QAM modulation having 5.6 dB peak to average power ratio. Simulations are performed using a gallium-nitride high electron mobility transistor (GaN HEMT) for a power amplifier with an output power of 10 W at 900 MHz.

In this article, different 2D and 3D mask styles for synthesizing large array pattern shaping to meet the requirements of modern applications are realized. The composition of the different beam pattern shaping is achieved by comparing the array factor with the proposed masks whose details (upper and lower borders) are predefined according to the designer. The generated pattern shapes are as follows: unscanned 2D single-pencil beam, scanned 2D pencil beam, 2D multi-beam scanning, 2D wide flat beam with little ripple, unscanned 3D single-pencil beam, 3D multi-beam scanning, and footprint (or contour) pattern for linear and planar arrays. The process of constructing these patterns is followed by predicting the amplitude-only weights (i.e., the phase weighting is considered zero in all computations) of the elements using the particle swarm optimization algorithm. In all proposed masks, different sidelobe levels are controlled, ranging from −20 to −100 dB. Also, the radiated beamwidth is controlled, ranging from 0.1334 rad (7.6 deg.) to 0.4 rad (23 deg.). The analysis and construction of linear and planar array arrangements depend on the formulation of antenna array theory through the implementation of the proposed (estimated) equations using MATLAB code. The simulation results showed the effectiveness of the proposed methods in controlling the pattern shape according to the required modern trends.

In this paper, miniaturization of fractal geometry with defected ground structure (DGC) concept has been experimentally verified at S-band (2–4) GHz. The design starts with a self-symmetry structure using conventional Vicsek snowflake-box fractal antenna. The same has been used in third iteration to achieve miniaturization. This proposed microstrip patch antenna (MPA) is resonating at 2.12 GHz with acceptable gain and broadside radiation. The miniaturization of about 87.26% when compared to conventional fractal MPA is achieved. The fractal unit cell is optimized for miniaturization and bandwidth by carrying out parametric study and applying the DGS shapes like rectangular and U-shaped slot etched in the ground plane of Vicsek snowflake-box fractal microstrip antenna. A fractal microstrip antenna is designed for wireless applications at 3.95 GHz. The fractal microstrip antenna is simulated using HFSS-V15 simulator. It is observed that the maximum size reduction of 87.26% is achieved in the third iteration of the Vicsek snowflake-box fractal radiating patch. The proposed fractal patch antenna is designed and fabricated using epoxy substrate of FR-4 with dielectric constant of 4.4 and thickness of 1.6 mm. The simulated results are compared with the measured results.

A high image rejection 38 GHz demodulator in TSMC 65-nm CMOS process is presented. To achieve better than −40 dBc image rejection ratio (IRR), a low I/Q mismatch 45° LO power splitter of sub-harmonic mixer is proposed. In this design, the 45° LO power splitter is composed of a Wilkinson divider, a series delay line with electrical length of 45° on one side of the divider, and a shunt 90° transmission line on the other side. This configuration is attractive because of its design simplicity and easy fabrication. Compared with the conventional techniques that utilize capacitors and inductors instead of the shunt 90° transmission line, the proposed LO power splitter can alleviate the issue of process variation. The demodulator demonstrates an IRR lower than −40 dBc from 37.5 to 41.5 GHz. In addition, conversion gain is 1.3 ± 0.9 dB from 33 to 41 GHz with 6 dBm LO power. The total direct current power consumption is 78 mW from 1.0 V supply voltage. At the modulation scheme of 4096-QAM, the proposed demodulator demonstrates 1.7% (−35.1 dB) error vector magnitude (EVM), which is very close to the EVM measurement floor 1.6% (−36 dB) of our millimeter-wave signal analyzer.

The paper presents a two-dimensional (2D) extended envelope memory polynomial model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital predistortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art 2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error of −51.7/−51.6 dB and adjacent channel error power ratio of −63.1/−63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are three times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio of −55.8/−54.6 dB for channel 1/2 and is 7–10 dB lower than those resulted with the 2D-DPD model and 2–4 dB lower compared with the DB-GMP model.

The temperature dependence of the dielectric parameters of tissues and tissue-mimicking phantoms is very important for non-invasive temperature measurement in medical applications using microwaves. We performed measurements of this dependence in the temperature range of 25–50°C using distilled water as a reference liquid commonly used in dielectric property studies. The results were compared with the literature model in the frequency range of 150–3000 MHz. Using this method, the temperature dependence of dielectric parameters of a new muscle tissue-mimicking phantom based on agar, polyethylene powder, and polysaccharide material TX-151 was measured in the temperature range of 25–50°C. The temperature dependence of the dielectric properties of this new muscle phantom was fitted to that of the two-pole Cole–Cole model and the deviation of the results between measured and modeled data was quantified.

The purpose of this paper is to disclose improved crystal based frequency source system covering design techniques and experimental methodologies for the stabilization of phase noise performance of X-band phase-locked loop (PLL) at 10.6 GHz. Phase noise performance of PLL-based unit under test (UUT) is prone to disturbance occurred in random vibration profile frequency spectrum. UUT self-resonance plays vital role in occurrence of disturbance in random vibration profile. The stabilization of phase noise performance during dynamic (random) vibration condition is achieved by following methodologies, i.e. vibration-isolator compensation techniques, purification tactic for reference crystal of PLL, and spatial location analysis for finding out mounting position of reference crystal. Spatial analysis helps to filter out UUT self-resonance frequency from random vibration spectrum which leads to reduction of frequency resonance pickups during random vibration testing.

The present paper presents a very efficient technique for enhancing the pointing accuracy in beam-waveguide (BWG) antennas and its application to the deep space antenna DSA2 of the European Space Agency. The proposed technique permits to achieve a twofold result: on the one hand, it provides a solution to the beam aberration issue, arising when the antenna simultaneously receives from and transmits to a spacecraft moving in the transversal direction. On the other hand, it allows to perform a fast conical scan to enhance the pointing accuracy of the antenna. Both results are achieved by simple linear displacements of feeds and mirrors located in the lower part of the BWG, with a very limited deterioration of the antenna gain. The required displacements of feeds and mirrors are determined through a fast optimization algorithm, based on a top-down approach, which requires repeated physical–optics analyses of the lower part of the beam waveguide only, with a significant reduction in the computing time.

This paper presents design, fabrication, and testing of a palm tree structured monopole antenna for wideband applications. The proposed antenna has a wide impedance bandwidth (−10 dB bandwidth) from 4 to 10.4 GHz. Palm tree antenna of compact size 23 mm × 20 mm is designed and fabricated on an FR4 substrate of thickness 1.6 mm. To validate the design, a mathematical relationship between the parameters of the palm tree geometry and the lower cut-off frequency has been established. Parametric study has been carried out to obtain optimum wideband characteristics. The prototype is experimentally validated for the band 4–10.4 GHz within ultra-wideband operations. Transfer function, impulse response and Group delay has been plotted in order to address the time domain characteristics of the palm tree antenna with fidelity factor values. The possible applications cover 5.2–5.8 GHz WLAN, C-band operations, 5.5 GHz WiMAX, and Wireless USB.

This paper presents the development of a reconfigurable receiver to undertake challenging signal processing tasks for a novel polarimetric radar system. The field-programmable gate arrays (FPGAs)-based digital receiver samples incoming signals at intermediate frequency (IF) and processes signals digitally instead of using conventional analog approaches. It offers more robust system stability and avoids unnecessary multichannel calibrations of analog circuits for a full polarimetric radar. Two kinds of dual-orthogonal signals together with corresponding processing algorithms have been investigated; the digital implementation architectures for all algorithms are then presented. Processing algorithms implemented in FPGA chips can be reconfigured adaptively regarding to different transmitted waveforms without modification of hardware. The successful development of such reconfigurable receiver extends our radar capacity and thus yields tremendous experimental flexibility for atmospheric remote sensing and polarimetric studies of ground-based targets.

Patch antennas with a meandering slot and different distributions of grounded metallic vias are presented in this paper. The meandering slot is adopted to stimulate dual-band operation, while the number and position of the grounded metallic vias are suggested to achieve different radiation performances. The characteristics are analyzed in detail where we find that the existence of the vias also improves the impedance matching. Four samples are designed, where dual-band with both linear polarization, dual-band with circular- and linear-polarization, and single band with linear polarization are obtained, respectively. The samples are finally fabricated and the measurement results agree well with the simulation results.

This paper presents a comprehensive study on the design of a 30 GHz, circularly polarized (CP), single horn-fed, metallic electromagnetic band gap (EBG) antenna. Three different approaches have been studied in order to create a 20 dBi antenna with an axial ratio (AR) lower than 1 dB over a 500 MHz bandwidth. Based on theoretical and experimental results, a conclusion is given on the best solution to obtain the desired characteristics. Perspectives and guidelines are also given for the design of multi-feed EBG antenna as a reflector focal feed for Ka-Band Space Applications.

All textile integrated dual-band monopole antenna with an artificial magnetic conductor (AMC) is proposed. The proposed design operates at 2.4 and 5.8 GHz for wearable medical applications to monitor the heartbeat. A flexible and low-profile E- shaped CPW dual-band textile antenna is integrated with a 4 × 4 dual-band textile AMC reflector to enhance the gain and specific absorption rate (SAR). The SAR is reduced by nearly 95% at both 1 and 10 g. The design was measured on the body with a 2 mm separation. The simulated and measured results appear in high agreement in the case of with and without AMC array integration. The measurement was performed in the indoor environment and in an anechoic chamber to validate the design based on reflection coefficient and radiation pattern measurements.

In this paper, we present a miniaturized ultra-wideband (UWB) bandpass filter (BPF) with multiple transmission zeros (TZs), which is based on transition technology of microstrip with short-circuited coplanar waveguide (CPW). The ground plane of the BPF contains a multiple mode resonator (MMR)-based CPW which is capacitively linked through the dielectric to two open-circuited microstrip lines on the top. The MMR is initially designed to allocate its lowest three resonant modes quasi-equally inside the designated UWB spectrum (3.1–10.6 GHz). This is followed by optimization of microstrip lines to provide a good broadband response possessing minimum insertion loss, two TZs at the lower and upper passband edges that improve selectivity and a wide stopband with appreciable attenuation. Later, multiple-folded split ring resonators are coupled to the BPF to inject dual passband TZs. The predicted theory in simulation is verified against measured result and is found to be in good agreement. The prototype covers a substrate area of only 14.6 × 9.2 mm2.

A compact multi-layer N-way power-dividing structure with good isolation and output return loss performance is proposed. The isolation network is circularly distributed that constitutes a closed ring-shaped architecture. The equivalent circuit model is given and the [S] matrix is developed to analyse and design the power-dividing structure. Finally, a six-way power divider centered at 2.1 GHz is designed and fabricated. The measured and simulated results agree well with each other. The total size of the power divider is 0.13λg × 0.19λg.

This paper proposed a compact planar monopole antenna operating at 5 GHz (5.180–5.825 GHz) industrial, scientific and medical (ISM) radio band. The antenna constructed with 20 mm × 12 mm radiating element and 25 mm square of the ground plane in FR4 substrate provided −10 dB bandwidth of 1 GHz (5.4–6.4 GHz). To improve the bandwidth, parasitic elements are added with the monopole antenna. A capacitive feed is also incorporated in the design. It observed that the proposed antenna with parasitic elements provides a larger impedance bandwidth of about 3 GHz (5.1–8.1 GHz), which is three-fold improvements over the one without parasitic patches. The prototype of the antenna that operates at 5.8 GHz frequency range is fabricated and characterized using a near-field measurement system. A good agreement is found between the simulation and measured results.

This letter presents a novel tunable coupling structure to simplify the design complexity of the miniaturized fully tunable filter by using open ring and varactors. Based on the proposed novel tunable coupling structure, a fully tunable bandpass filter is implemented with independently tunable operating frequency and bandwidth. The tunable resonator and tunable coupling structure can be easily combined to improve Out-of-band suppression performance. The design procedure of a fully tunable bandpass filter consists of five tunable cavities and tunable coupling rings is also proposed. A prototype of the proposed fully tunable filter is built to verify the design experimentally. Good agreement between simulated and measured results is obtained.

The detailed synthesis of a direct access ring filter topology fully controlled with the following targeted specification (center frequency, low transmission zero frequency, and matching level in the passband) is hereby presented. For this topology, the lowest achievable bandwidth is limited by technological constraints. Thereby a solution consisting in adding capacitive loads is proposed. The associated synthesis is also given and discussed. Both syntheses are illustrated with 60 GHz integrated planar filters implemented in the IHP 130 nm BiCMOS technology. Various 3 dB fractional bandwidths from 18 to 8% are targeted, some of them require the implementation of the capacitive loaded solution. The latter allows us to lower the bandwidth limit of the nominal topology as well as to get a high miniaturization, up to 3.4, depending on the capacitance value. Thanks to good measurement results, this implementation highlights the high efficiency, reliability, and versatility of the synthesis without the need of tuning simulations or post-simulations.

This paper considers and compares the numerical characterization of regular planar antenna arrays from two viewpoints. In the case where the array is sufficiently large, the well-known infinite array idealization applies and a very efficient simulation method is presented which combines array theory with a specialized form of the finite-element method called the transfinite element method (TFEM). Alternatively, a more direct approach is discussed in which the entire antenna array is simulated as a finite structure using recent advances in the domain decomposition method (DDM). Taken together, the two methods provide a comprehensive simulation method for regular arrays from small order to very large order.

A compact dual-band microstrip bandpass filter (BPF) is presented for application at the frequencies 2.4 and 5.84 GHz. The proposed main resonator consists of two L-shaped resonators. To improve the upper-stopband of the proposed filter, modified U-Shaped resonators are accepted. The operation mechanism of the filter is investigated based on proffered equivalent-circuit model and transformation function. The sketched dual-band BPF attends the insertion loss less than 0.1 and 0.4 dB Also the return loss is 26 and 28 dB at 2.4 and 5.84, respectively. This proffered filter structure is proper for Bluetooth and wireless local area networks and other wireless communication systems. An overall good agreement between measured and simulated results is observed.