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.

In this paper, we report a new high-speed and high-power switching circuit based on GaN HEMT's. The elementary switching cell, composed of two GaN HEMT's and two resistors, acts like a power threshold comparator with high-output voltage. Theoretical analysis of static and dynamic circuit operation points out the dependence of efficiency and switching speed to the main circuit elements. Four switching cells are then combined together thanks to SiC Schottky diodes to design a multi-level power switch that can be used as a power supply modulator for envelope tracking power amplifiers. The designed four-level supply modulator, based on Nitronex GaN HEMT's, exhibits more than 75% of efficiency for an envelope signal up to 4 MHz, a switching frequency of 20 MHz and output voltages in the range of 12–30 V.

This work presents a wideband amplifier, in 12–19 GHz frequency range, with noise figure lower than 1.35 and 26 dB of gain developed in the frame of European Component Initiative program, supported by European Space Agency. By using a flexible biasing, this amplifier allows us to reach a significant linearity, output power at 1 dB compression up to 19 dBm, or to reduce the DC consumption close to 210 mW. This versatility implies that a user has a low-noise amplifier) or medium power amplifier in a single chip. The D01PHS process, from OMMIC foundry, has been chosen in order to realize this MMIC, thanks to linearity capability, and also thanks to a significant potential for low-noise amplification.

This paper outlines an original shape optimization library backed by a three dimensional (3D) full-wave electromagnetic (EM) simulator, combining several efficient structural optimization techniques and suitable for viable computer-aided design (CAD) of complex microwave components. The microwave components are modeled by finite element method (FEM) and their dimensions and shape are optimized using four techniques: design of experiments (DOE), level-set method (LS), topology gradient (TG) method, and genetic algorithm (GA). The various methods allow determining the optimal geometry, shape or topology of 2D or 3D objects within the microwave device, by minimizing iteratively a cost function related to the desired specifications. Typical demonstration illustrates the versatility of the proposed library based on the design of a dual mode dielectric resonator filter in order to improve its unloaded quality factor by keeping the same frequency isolation, their accuracy and efficiency are verified by the available measured results.

The silicon/porous silicon (PS) hybrid substrate is an interesting candidate for the monolithic integration of radiofrequency (RF) circuits. Thus, passive components can be integrated on the insulating PS regions close to the active devices integrated on silicon. Regarding silicon, hybrid substrates allow the improvement of RF circuits performances. To demonstrate it, coplanar waveguides have been integrated on glass, silicon, and localized PS substrates. The characterization results show that the substrate losses are reduced with PS.

This paper presents the work carried out to assess the feasibility of miniature directive antennas. It is based on an analysis of the physical limits of antenna directivity in general and in particular as a function of their compact dimensions. A state of the art is done to identify and classify techniques to increase the directivity of compact antennas.

A high-directivity switched-beam antenna in the V-band is presented and includes a circularly-polarized transmit-array realized in a low-cost printed technology associated with a focal source array integrated on high-resistivity silicon. The measurements show a maximum gain of 12.1 dBi, a 3-dB gain-bandwidth of 57.8–70 GHz, and an axial ratio below 5 dB. The antenna exhibits five beams pointing from −22° to +23° in one plane, its size of 25 × 25 × 10 mm3 is compatible with the integration in different multimedia communication devices.

We present a study on using carbon nanotubes (CNTs) as the radiating part of resonant antennas in order to reduce their dimensions. A mesoscopic electromagnetic (EM) model for CNTs was developed to allow the simulation of RF devices in classical EM solvers while retaining the specific properties of CNTs. A circuit approach is also used to provide a physical interpretation of the results on monopole antennas and trend prediction. These techniques constitute a platform to study the trends and trade-offs involved in the design of these antennas. Finally, these results are used to assess suitable fabrication techniques for CNT-based short resonant antennas and conclusions are drawn on their potential applications.

In this paper a novel approach for determining the four noise parameters of FET devices over frequency is presented. Such methodology is made of two parts: the first one allows to straightforwardly extract single-frequency noise parameters from source-pull data; the second one extends this capability to multi-frequency, source-pull data to obtain a full description of device noise behavior over frequency by means of at most 10 constant parameters (depending on the required accuracy). The whole process is automated via a software routine and does not need a previous knowledge of the FET equivalent circuit's topology, or the values of its elements. This peculiarity makes the proposed method very well suited to quick characterization campaigns of active devices, avoiding the burden of a whole set of prior, different measurements and the relevant, critical extraction procedures, which are strongly dependent on the device.

An accurate and very large band (30–110 GHZ) lumped element equivalent circuit model of capacitive RF-MEMS components based on a standard 250 nm BiCMOS technology is presented. This model is able to predict the effect of the fabrication process dispersion, synthesize new components and monitor the failure mechanisms. Moreover, a reliability study is performed in order to define a screening criterion (VPOUT > 36 V and |VPIN − VPOUT| ≤ 1) based on which a selection of the devices with optimal performance in terms of RF and lifetime performance can be made. Finally, a very quick effective technique (non-intrusive) is proposed to carry out this operation.

In this paper, the design analysis of a multi-way and high-power radial combiner is presented. This combiner incorporates a rigid stripline-type combining structure. This analysis, based on an equivalent circuit model and segmentation of the radial transmission line, provides simple design formulae. The developed methodology, after fine-tuning with the help of an electromagnetic full-wave simulator, is physically demonstrated by developing a high-power (16 kW average) and high combining-efficiency (98.9%) 16-way combiner at the center frequency of 505.8 MHz. Its efficient and repeatable performance, fabrication-friendly structure, and absence of the heat-related problem, caused by the isolation resistor, are the main features of this design.

In the present work, a novel multistrip monopole antenna fed by a cross-shaped stripline comprising one vertical and two horizontal strips has been proposed for wireless local area network (WLAN)/Industrial, Scientific, and Medical band (ISM)/International Mobile Telecommunication (IMT)/BLUETOOTH/Worldwide Interoperability for Microwave Access (WiMAX) applications. The designed antenna has a small overall size of 20 × 30 mm2. The goal of this paper is to use defected ground structure (DGS) in the proposed antenna design to achieve dual-band operation with appreciable impedance bandwidth at the two operating modes satisfying several communication standards simultaneously. The antenna was simulated using Computer Simulation Technology Microwave Studio (CST MWS) V9 based on the finite integration technique (FIT) with perfect boundary approximation. Finally, the proposed antenna was fabricated and some performance parameters were measured to validate against simulation results. The design procedure, parametric analysis, simulation results along with measurements for this multistrip monopole antenna using DGS operating simultaneously at WLAN (2.4/5.8 GHz), IMT (2.35 GHz), BLUETOOTH (2.45 GHz), and WiMAX (5.5 GHz) are presented.

Implantable antennas have recently been receiving substantial attention for medical diagnosis and treatment. In this paper, a coplanar waveguide-fed monopole antenna for industrial, scientific, and medical (ISM) band biomedical applications is proposed. The antenna has a simple structure is placed on human tissues such as muscle, fat, and skin. The designed antenna is made compatible for implantation by embedding it in an FR4 substrate. The proposed antenna is simulated using the method of moment's software IE3D by assuming the predetermined dielectric constant for the human muscle tissue, fat, and skin. The antenna operates in the frequency of ISM bands, 2.4–2.48 GHz. Simulated and measured gains attain −7.7 and −8 dBi in the frequency of 2.45 GHz. The radiation pattern, return loss, current distribution, and gain of these antennas were examined and characterized.