A four-stage distributed amplifier utilizing low-loss slow-wave shielded (SWS) transmission lines is implemented in a standard 0.13 μm Complementary Metal-Oxide-Semiconductor (CMOS) technology. The amplifier when biased in its high current operating mode of IDtotal = 46 mA (at Vdd = 2.2 V, Pdiss = 101 mW) provides a forward transmission gain of 11.3 ± 1.5 dB with a 3-dB bandwidth of 17 GHz and a gain-bandwidth product of 74 GHz. The noise figure (NF) under the same bias condition is better than 8.5 dB up to 10 GHz. The measured output-referred 1-dB compression point is higher than +2 dBm. The amplifier is also measured under low-bias condition of IDtotal = 18 mA (at Vdd = 1.15 V, Pdiss = 20.7 mW). It provides a transmission gain of 6.6 ± 1 dB, a 3-dB bandwidth of 14.8 GHz, a gain-bandwidth product of 35.5 GHz, and a NF of better than 8.6 dB up to 10 GHz. Despite using a simple four-stage cascode design, this distributed amplifier achieves very high-gain-bandwidth product at a relatively low DC power compared to the state of the art CMOS distributed amplifiers reported in the literature. This is due to the incorporation of low-loss SWS coplanar waveguide (CPW) transmission lines with a loss factor of nearly 50% of that of standard transmission lines on CMOS-grade Si substrate.

The design and full-wave analysis of an antenna system for ultra-wideband radio direction finding applications is presented. The elliptical dipole antenna is selected as antenna element due to its robust circuital and radiation properties. The influence of the conformal deformation on the antenna performance has been studied in details. A suitable radome is designed to enhance the antenna front-to-back radiation ratio, as well as to increase the environmental durability of the structure. The considered antennas are optimized for their adoption in two different sub-arrays covering the [250, 950] MHz and [0.9, 3.3] GHz frequency bands, respectively. A uniform circular array (UCA) with five elements is used for the array topology. The full-wave analysis of the whole array structure is carried out in order to evaluate the coupling between the antenna elements. In particular, a novel calibration technique is developed in order to compensate for the mutual coupling between the array elements, possible variations in the antenna characteristics, and the effects of the array bearing structure. The performance of the designed array in terms of direction-of-arrival estimation is thoroughly analyzed and discussed.

In this paper, the design, simulation, and fabrication of a novel printed rectangular slot antenna with a band-notched function suitable for 2.4 GHz wireless local area network (WLAN) and ultra-wideband (UWB) applications is presented and investigated. Two pairs of slits are introduced into the ground plane to realize band-notched function, by tuning the position, length, and width of which a suitable rejected frequency band can be obtained. To improve the impedance matching, a rectangular cut is also made in the ground plane so that the antenna can cover 2–12 GHz frequency range. According to the measured results, the proposed antenna has a large bandwidth totally satisfying the requirement of 2.4 GHz WLAN and UWB systems, while providing the required band-notch function from 5.1 to 5.9 GHz. The study of transfer function and time-domain characteristics also indicates the band-notched function of the antenna. The radiation patterns display nearly omni-directional performance and the antenna gain is stable except in the rejected frequency band (5.1–5.9 GHz). Moreover, group delays are within 1.5 ns except for the notch band. These features make it a promising candidate for UWB wireless applications. Details of this antenna are described, and the experimental results of the constructed prototype are given.

A fully integrated transmitter (TX) and receiver (RX) front-end chipset, produced in 0.25 µm SiGe:C bipolar and complementary metal oxide semiconductor (BiCMOS) technology, is presented. The front-end is intended for high-speed wireless communication in the unlicensed ISM band of 9 GHz around 60 GHz. The TXand RX features a modified heterodyne topology with a sliding intermediate frequency. The TX features a 12 GHz in-phase and quadrature (I/Q) mixer, an intermediate frequency (IF) amplifier, a phase-locked loop, a 60 GHz mixer, an image-rejection filter, and a power amplifier. The RX features a low-noise amplifier (LNA), a 60 GHz mixer, a phase-locked loop (PLL), and an IF demodulator. The measured 1-dB compression point at the TX output is 12.6 dBm and the saturated power is 16.2 dBm. The LNA has measured noise figure of 6.5 dB at 60 GHz. Error-free data transmission with a 16 quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) signal and data rate of 3.6 Gbit/s (without coding 4.8 Gbit/s) over 15 m was demonstrated. This is the best reported result regarding both the data rate and transmission distance in SiGe and CMOS without beamforming.

Doubled frequency optical two-tone generation and optical single sideband (SSB) modulation by the dual-electrode-type electro-optic (EO) modulator with a single Mach–Zehnder (MZ) interferometer were considered. We theoretically showed that redundant spectrum components in the modulated optical signals, which are caused by the imbalance of light splitting ratio between the two arms of the interferometer, are significantly suppressed by controlling the input power ratio of RF modulation signals applied to each electrode. This effect was confirmed by the experiment, where an optical two-tone with the redundant components 49.8 dB lower than the primary two-tone components in intensity level was obtained. This method is also valid for suppression of undesired frequency components of RF signals that are generated at a photo detector from the optical two-tone waves propagated through a dispersive optical fiber.

This paper analyzes the noise properties of balanced amplifier configurations in terms of noise waves and discusses the effect of various amplifier configurations on the noise and signal parameters. It shows how the noise generated in the load on the input coupler of a balanced amplifier deteriorates the amplifiers noise resistance parameter with respect to that of its component amplifiers. The properties of two new balanced amplifier configurations will be discussed, which enable the reduction or elimination of this deterioration.

An empirical model has been proposed which provides an excellent fit to the drift of pull-in and release voltages of a MEMS capacitive switch due to bulk dielectric charging. This model correctly fits the linear time dependence over short time spans and transitions to a logarithmic dependence over longer time spans. Using this model to fit measured data enables a quick and efficient determination of the rate of dielectric charging, as well as providing a worst-case prediction of when the switch will fail due to dielectric charging. This model has been used to explore the impact of applied voltage, temperature, and duty factor on switch lifetime.

In this paper, an accurate neuro-fuzzy-based model is proposed for efficient computer-aided design (CAD) modeling and optimization of microwave circuits and devices. The adaptive neuro-fuzzy inference system (ANFIS) approach is used to determine the scattering parameters of a microstrip filter and is applied to the optimization design of this microstrip filter. The ANFIS has the advantages of expert knowledge of fuzzy inference system and learning capability of artificial neural networks. The neuro-fuzzy model has been trained and tested with different sets of input/output data. Finally, different results, which confirm the validity of the proposed model, are reported.

A study of the electrical performances of AlInN/GaN High Electron Mobility Transistors (HEMTs) on SiC substrates is presented in this paper. Four different wafers with different technological and epitaxial processes were characterized. Thanks to intensive characterizations as pulsed-IV, [S]-parameters, and load-pull measurements from S to Ku bands, it is demonstrated here that AlInN/GaN HEMTs show excellent power performances and constitute a particularly interesting alternative to AlGaN/GaN HEMTs, especially for high-frequency applications beyond the X band. The measured transistors with 250 nm gate lengths from different wafers delivered in continuous wave (cw): 10.8 W/mm with 60% associated power added efficiency (PAE) at 3,5 GHz, 6.6 W/mm with 39% associated PAE at 10.24 GHz, and 4.2 W/mm with 43% associated PAE at 18 GHz.

The design of agile active antennas requires an efficient modeling methodology in order to quantify the impact of other components on the array radiation pattern, and especially the influence of power amplifiers (PA). Therefore, the performance prediction of PA on TX chains is of prime importance. This article describes two different approaches for active antenna applications. The first one concentrates on PA macro-modeling, which takes into account a large output load impedance mismatch with a voltage standing wave ratio up to 4:1. A PA behavioral model based on nonlinear scattering functions was developed and extracted from CW measurements. The model validity was checked by comparison with the measured data. The second one describes a novel technique for synthesizing a given radiation pattern, whereas taking into account the mutual coupling and calculated matching impedances (ZL ≠ 50 Ω) of each antenna in the array according to frequency and pointing angle.

A highly integrated transceiver microwave monolithic integrated circuit (MMIC) manufactured in a 200-GHz SiGe:C production technology is presented, applicable for sensing- and broadband communication applications. To simplify the analog frontend, the fully differential design is based on a homodyne architecture. It comprises an LO signal generation unit based on a wideband 60 GHz fundamental Voltage Controlled Oscillator (VCO) and an on-chip prescaler, covering the full operational frequency band of 57–64 GHz. Within this bandwidth, the upconverter exhibits an upconversion gain of 23.6–26.4 dB and a maximum output-referred 1-dB compression point of 14 dBm. The downconverter provides a Double Sideband (DSB) noise figure of 9–12 dB with a downconversion gain of 37–71 dB. On chip AC-coupling of the receiver IF-output with a lower −3 dB cut-off frequency as low as 16 kHz eliminates mixer DC-offsets and enables on-chip Intermediate Frequency (IF) amplification. The whole transceiver MMIC draws a current of 415 mA from a single 3.3 V supply and requires few components externally to the chip.

A novel waveguide called multilayer porous waveguide (MPW) is proposed as microwave low-loss transmission lines. MPW is a fully rectangular dielectric waveguide composed of several periodically rectangular air gaps in a bulk dielectric that can be easily formed by placing several dielectric substrates in interval with air gaps. The loss and propagating characteristics of both TE and TM modes in MPW are studied. The TE mode confined in the air gaps has a lower loss than the TM mode spread out in air gaps and dielectric; however, the loss of TM mode is still less than that of conventional microwave waveguides. Finally, MPW is an artificial material with desirable electrical permittivity and loss that can be used in structure of conventional waveguides.

Among other reliability concerns, the dielectric charging is considered the major failure mechanism which hinders the commercialization of electrostatic capacitive radio frequency micro-electro-mechanical systems (RF MEMS) switches. In this study, Kelvin probe force microscopy (KPFM) surface potential measurements have been employed to study this phenomenon. Several novel KPFM-based characterization methods have been proposed to investigate the charging in bare dielectric films, metal–insulator–metal (MIM) capacitors, and MEMS switches, and the results from these methods have been correlated. The used dielectric material is plasma-enhanced chemical vapor deposition (PECVD) silicon nitride. The SiNx films have been charged by using a biased atomic force microscope (AFM) tip or by electrically stressing MIM capacitors and MEMS switches. The influence of several parameters on the dielectric charging has been studied: dielectric film thickness, deposition conditions, and under layers. Fourier transform infra-red (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) material characterization techniques have been used to determine the chemical bonds and compositions, respectively, of the SiNx films. The data from the physical material characterization have been correlated to the KPFM results. The study provides an accurate understanding of the charging/discharging processes in dielectric films implemented in electrostatic MEMS devices.

A dual wideband design of Sierpinski carpet fractal-shaped planar monopole antenna with a coplanar waveguide (CPW) feed is proposed in this letter. Wide impedance bandwidth of 22% at lower resonance from 4.88 to 6.08 GHz and 41.7% at higher one, which ranges from 9.5 to 14.5 GHz, is obtained. Measured realized antenna gain is around 5 dBi at the lower band centered around 5.5 GHz and are around 4.5 dBi at the higher band. A fabricated prototype is developed with good agreement between simulation and measurement.

This paper reports on a novel voltage-mode class-S power amplifier for the 450 MHz band, based on GaN–HEMT monolithic microwave integrated circuits (MMICs). It achieves a peak output power of 3.4 W for a single tone at 400 MHz, encoded in standard band-pass delta-sigma modulation with 1.6 Gbps sampling frequency. The corresponding efficiency is 38%, peaking at 52% for 0.5 W output power. In order to demonstrate the influence of coding efficiency, additional measurements using a periodic square-wave signal were performed (class-D operation), which yield a maximum output power of 7 W with 64% efficiency. To the author's knowledge, these are the best results in this frequency range achieved so far with the voltage-mode class-S configuration. The paper discusses behavior at power back-off and the influence of the loss mechanisms.

An in vitro system for 2.45 GHz microwave (MW) exposure with real-time fluorescence measurements is proposed. This system is specifically designed for the measurement of those biophysical parameters of living cells or membrane models which can be quantified by spectrofluorometric methods (e.g. membrane generalized polarization (GP), membrane fluidity, membrane potential, etc.). The novelty of the system consists in the possibility to perform fluorescence measurements on the biological samples simultaneously with their exposure to MW. The MW applicator is an open ended coaxial antenna which is dipped into a cuvette. The distribution of electromagnetic field and specific absorption rate (SAR) in the cuvette are provided from a rigorous electromagnetic numerical analysis performed with a finite difference-time domain (FDTD) based tool. With this system, fluorescence measurements were used to calculate the membrane GP values of giant unilamellar vesicle suspensions that were acquired during exposure to a 1.2 W incident power. For this power, the SAR distribution and mean SAR value for the whole volume were calculated based on temperature measurements made at different positions inside the cuvette.

This paper provides an overview of the research carried on in the EASY-A project concerning the design of antennas for different applications in the unlicensed band around 60 GHz, and their integration into compact RF front-ends. Different antenna configurations, in conventional microwave substrate and low-temperature co-fired ceramics (LTCC), were studied and fabricated. The results comply with the requirements established for various scenarios.

This paper explores the characterization of dielectric and conductive properties of carbon nanotube (CNT) networks. This is carried out by building planar transmission lines where conventional metallic traces are replaced by CNT networks. The proposed transmission lines with CNT networks are presented. Experimental realization and repeated two-port microwave measurements of proposed transmission lines enable the accurate extractions of their fundamental parameters showing percolation effects due to presence of CNT networks. The frequency-dependent phase velocity characteristics show a dramatic reduction compared to the speed of light in vacuum. The large magnitude of extracted complex permittivity for CNT networks also exhibits its percolation performance. The effects of CNTs' bulk density on measured and calculated parameters are explained. The results presented in this paper demonstrate the feasibility and the potential of building transmission lines and radio-frequency (RF) circuits elements using CNT networks.

This paper focuses on the behavioral modeling of the passive RF blocks from frequency-domain samples. This work is based on vector fitting (VF) approach which is a robust method for MIMO system identification in the frequency domain. This paper addresses firstly the problem of convergence using envelope transient (ET) on complex circuits, i.e. power amplifiers (PAs), where linear sub-circuits are widely described through S-parameters matrices derived from ElectroMagnetic (EM) simulations. An alternative way leads to combine VF method with an RLC synthesis process at the circuit level. This approach is validated on a simple circuit case and generalized to MIMO systems. Second application is the behavioral modeling of MIMO blocks at system level in a high-level spice-like system simulation tool which allows “Control Flow” simulations. The proposed approach combines on one hand the VF method with and impulse responses evaluation on the other hand. In consequence, bilateral behavioral models of MIMO system can be efficiently achieved irrespective of the number of access. This method is validated at once on simple and complex MIMO blocks. As a result, the topological behavioral modeling of complex PAs, which distinguish linear sub-circuits and nonlinear ones, is now possible in a high-level time-domain CAD tool.

In this work, we analyze the pressure sensing of a thin film molybdenum/aluminumnitride/molybdenum (Mo/AlN/Mo) microwave/RF MEMS filter fabricated by a simple technology. After an experimental characterization in a frequency range between 1 and 36 GHz, we focused on the piezoelectric effect due to the stress properties of the piezoelectric AlN layer by applying forces by means of weights. Variations in the bandpass region of the microwave/RF filter are observed by proving high sensitivity also for low applied weights. We check by a properly designed three-dimensional (3D) finite-element method (FEM) tool the pressure-sensing property of the proposed device. Finally, we analyze the bad gap property of a chip with central defect around 40 GHz.