With the ever-increasing need for wireless communication and the emergence of many systems, it is important to design broadband antennas to cover a wide frequency range. The aim of this paper is to design a broadband patch antenna, employing the three techniques of slotting, adding directly coupled parasitic elements and fractal electromagnetic band gap (EBG) structures.The bandwidth is improved from 9.3 to 23.7%. A wideband ranging from 4.15 to 5.27 GHz is obtained. Also, a comparative analysis of embedding EBG structures at different heights is also done. The composite effect of integrating these techniques in the design provides a simple and efficient method for obtaining low-profile, broadband, and high-gain antenna. By the addition of parasitic elements the bandwidth was increased to 18%. Later on by embedding EBG structures the bandwidth was increased up to 23.7%. The design is suitable for a variety of wireless applications like WLAN and radar applications.

In this paper, an orthogonal frequency-division multiplexing (OFDM) waveform radar sensing approach is demonstrated based on field measurements at C-band. We demonstrate a concept that is based on the exploitation of typical wireless communication transmissions to perform passive, distributed radar sensing. Our concept is based on an OFDM radar that operates in the modulation symbol domain and can be well integrated into existing OFDM receivers. The measurement setup and the signal processing steps for the OFDM radar are described. The results show that the passive, distributed radar sensing approach can be used to detect and localize moving cars and even pedestrians in automotive intersection scenarios.

A single-fed circularly polarized microstrip antenna is proposed where the antenna structure exhibits truncated corners in the radiating square patch. The truncated corners square patch structure is loaded with a circular slot and is resonating at 2.25 GHz with circular polarization. Furthermore, the proposed antenna is stacked using an upper circular patch thus achieving a dual-band circularly polarized pattern. The dual-band antenna resonates at 2.25 GHz in the first band and with impedance bandwidth ranging from 4.4 to 5.5 GHz in the second band. The size of the proposed stacked structure is compact compared with the conventional circularly polarized stacked antenna designs. Proposed structures are fabricated and fed using Subminiature version A (SMA) connector. The measured results are in good agreement with the simulated. The antenna shows stable radiation characteristics for the entire band of operation.

A microstrip transmission line fed fork-shaped planar antenna is proposed for Bluetooth, WLAN, and WiMAX applications. The antenna made of a microstrip feed line, fork-shape patch on one side and defected ground plane on the other side of dielectric substrate. A fork-shape is formed by two side circular arms and a rectangular central arm. The inverted T-shaped ground plane with a rectangular slot in the center arm is used to increase the bandwidth with better impedance matching of the lower band. The antenna is practically fabricated to validate the design. The antenna resonate dual band to cover an entire the WLAN and WiMAX bands. The antenna shows the measured bandwidth of 410 MHz (2.26–2.67) and 3.78 GHz (3.0–6.78 GHz) at lower and upper bands, respectively.

In this contribution, we study the design and experimental characterization of a reconfigurable transmitarray in X-band with reduced focal distance. To this end, we consider an illumination with four feed horn antennas in two different configurations. The focal distance and the horn configuration in the focal plane have been optimized with an in-house simulation tool. The effects of source placement errors and excitation unbalances are also studied. The numerical results show a reduction of the focal distance by a factor 1.8 if compared with the single-source case, for a reconfigurable 400-element transmitarray designed in X-band. Moreover, generation of multiple beams is considered and demonstrated numerically for spatial power combining applications. The experimental results obtained in radiation are in good agreement with the numerical predictions. This multiple-source transmitarray exhibits similar radiation performances as the single-source one in terms of gain, bandwidth and beam tilting capabilities, but with about half its volume. This technique seems very attractive for a better integration on various platforms such as vehicles, drones, aircrafts, buildings, etc.

GaN technology has gained a lot of attention in Europe over the last few years for various domains including RF electronics. After a few years of active observation, United Monolithic Semiconductors (UMS) has taken the decision to introduce a GaN technology family in its portfolio. Based on its extensive experience of III–V technology and the intensive support and collaboration with partners and European research institutes, UMS has developed the capability to produce state-of-the-art GaN devices and circuits. The present paper will summarize the current status achieved and illustrate it with a few representative examples. Aspects covering material, devices, and circuits will be addressed.

An optoelectronic oscillator (OEO) under the influence of a weak interference has been investigated. The system equation of the OEO under the influence of interference has been derived. A novel technique for calculating the lock range of the oscillator using the harmonic balance method in presence of interference has been demonstrated. Theoretical analysis coupled with experimental results has been presented.

This paper presents the design of a high-power dual-band power amplifier (PA) for envelope tracking (ET) operation and its characterization in concurrent dual-band ET operation modes. The design approach relies on the specific actual signal probability distribution and the prototype was conceived for the WCDMA 3GPP DL signals. The paper discusses the impact of the ET-shaping function influence on the linearity versus mean efficiency trade-off, for both single and concurrent dual-band cases. The technique was applied to a concurrent 870 and 2140 MHz ET-PA designed around a GaN HEMT device. The ET friendly design method led to performance very close to those observed at each single band. Over a bandwidth of 100 MHz and for PAR = 6.5 dB, the measured results reported a mean DE better than 71 and 54%, with a peak power higher than 55 and 54 dBm, at the two frequency bands, respectively. When evaluated in concurrent dual-band mode with two WDCMA signals at 6.5 dB PAR each, the ET-PA exhibited an estimated average total power of 49.5 dBm with 57.1% average drain efficiency.

This paper presents recent advances on reconfigurable reflectarrays at the University of Perugia. In particular, the activities carried out in the framework of the FP7 project ARASCOM (“MEMS and Liquid Crystal based” Agile Reflectarray Antennas for Security and COMmunication). As for ARASCOM outcomes, the purpose of the project is the design of a very large reconfigurable reflectarray controlled with micro-electro-mechanical systems (MEMS) for mm-wave imaging system at 76.5 GHz. A system with sufficient resolution to detect concealed weapons impose challenging requirements on the antenna, which shall be made of hundreds of thousands elements. The problem has been addressed by exploiting some innovative solutions and architectures that will be described in this document. In particular, the dimensioning of the reflectarray, the proposed 1-bit geometry of elementary cell, and the innovative biasing control architecture are reported together with the MEMS design and fabrication and the experimental results of a demonstrating board that validated the adopted procedure.

A magnetic dipole quasi-Yagi antenna based on a dielectric resonator (DR) is proposed in this letter. The dominate TE1δ1 mode of the rectangular DR is used as a magnetic dipole which can be differentially fed by the coplanar strip line (CPS). Thanks to the DR employment, the proposed antenna has several advantages such as compact size and flexible design which means the 3-D dimensions of the DR can be easily adjusted to cater for various applications. Meanwhile, the gain of the proposed DR quasi-Yagi antenna is higher than that of traditional electric dipole counterparts. Furthermore, since the DR driver is horizontally polarized, both the metal strip and DR can be used as a director for enhancing the end-fire gain. To verify the design concept, a prototype operating at the X-band is fabricated and measured. Good agreement between the simulated and measured results can be observed.

We present the realization of a cooperative radar system for ranging applications with integrated data-transmission capability. The simultaneous transmission is performed by the radar-hardware without the necessity of additional components or an auxiliary data-link. Therefore, the data are directly embedded in the transmitted chirp of a frequency-modulated continuous-wave radar sensor. A second station, acting as receiver, uses an identical, but unmodulated chirp for down-conversion. The resulting signal then is processed by a non-coherent demodulator setup, extracting the communication data. Measurement results from transmission of messages with different bit-rates are shown. By utilizing existing radar-hardware a transmission rate of up to 256 kbps is possible, without the need of a dedicated transceiver. Additionally, a method to optimize the ranging results by variable distribution of the available signal power between distance-measurement and communication system is presented.

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.

Artificial neural networks (ANNs) have acquired enormous importance in computing of the performance parameters of microstrip antennas due to their generalized and adaptive features. However, recently the concept of support vector machines (SVMs) has become very much popular in performance parameters computation due to several attractive features over ANNs. Specifically, SVMs outreach ANNs noticeably in terms of execution time. Likewise, ANNs are having multiple local minima problem, whereas a global and unique solution is provided by SVMs. In this paper, several performance parameters like: resonant frequency, gain, directivity, and radiation efficiency of slotted microstrip antennas with modified ground plane are computed with the help of SVM formulation. Comparisons of different parameters of simulated and computed values are illustrated. The achieved radiation patterns at particular resonant frequency in different planes are included as well. A prototype of the optimized antenna is also fabricated and characterized. A good agreement is attained among the computed, simulated, and measured results.

A compact monopole antenna backed with a 1 × 2 textile-based artificial magnetic conductor (AMC) array is proposed. Textile was mainly selected for the AMC materials according to an investigation that took place between different AMC substrate materials, where it was settled that the textile one displayed the highest antenna gain and efficiency. The monopole antenna and the AMC, distanced apart by 5 mm, combined form the integrated design. It operates at 2.4 GHz, which was particularly selected as the resonant frequency for wirelessly sending the subject's symptoms data via Wi-Fi, with realized gain and total efficiency of 6.76 dBi and 88.4%, respectively, in free space. Separated by 3 mm from the specific anthropomorphic mannequin human hand model, it displays a realized gain and total efficiency of 4.06 dBi and 44.39%, respectively, in a flat condition. Furthermore, it exhibits a specific absorption rate (SAR) of 1.8 W/kg averaged over 10 g of tissue. When bent over the human hand model, it performs well and exhibits a maximum SAR of 0.521 and 0.406 W/kg, averaged over 1 and 10 g of tissues, respectively. As a result of such outcomes, the proposed integrated design can be nominated for wearable hand/wrist and Wi-Fi applications.

In this paper, a simple synthesis technique to obtain the geometrical parameters of the modified circular ring for angular and polarizations (perpendicular and parallel) stable frequency selective surface (FSS) has been discussed. The geometrical parameters of the modified circular ring FSS structure have been achieved using the proposed synthesis technique, which is based on the equivalent circuit (EC) approach. In addition to this, the numerical analysis is also discussed to determine the values of EC parameters, which depends on the basic system level characteristics such as frequency of operation and reflection/transmission coefficients. The analytical results are supported using the full-wave three-dimensional electromagnetic (EM) simulators such as CST Microwave Studio and Ansoft HFSS. The sensitivity of the structure to the perpendicular and parallel polarized EM wave up to 50° angle-of-incidences (AOIs) has been discussed. The stability over different AOI is attributed to the appropriate thickness of the structure with its small unit-cell dimensions. We have also fabricated and experimentally tested the proposed FSS structure.

Differential signaling is very common for high frequency integrated circuit design. Accurate multimode de-embedding at multigigahertz frequencies, however, is a major challenge. The differential and common-mode parameters can be obtained by converting the measured four-port nodal S-parameters into the mixed-mode form. Under certain conditions, it is possible to separate the modes and consider only the entries corresponding to the differential S-parameters. This allows to reduce the measured 4 × 4 matrix to a 2 × 2 matrix and consider the differential device as a two-port network. Thus, the standard de-embedding techniques, derived for two-port networks, can be applied to differential S-parameters. The purpose of this paper is to investigate the applicability of this approach for on-wafer measurements. We describe analytically the conditions under which this method is valid. As an example, a 2:1 transformer, manufactured in Infineon's 0.13 μm CMOS (complementary metal-oxide semiconductor) process, has been characterized. On-chip de-embedding structures have been fabricated using the same process. The results obtained using Short-Open, Thru-Line, and Thru-Line-Reflect de-embedding techniques are compared. Additionally, the results are verified by simulation of a device under test having high-mode conversion.

A high impedance surface (HIS) consisting of metallic square patches electrically connected one to each other with resistors is shown. Tunability of the absorption factor is achieved by the resistor value. The absorbing band of the loaded HIS is determined by the phase of the signal reflected by this structure. The main contribution of the paper is to demonstrate the absorption behavior over a wide range of incidence angle for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations. Using an equivalent circuit the resistor effect is investigated. It is shown that at resonance, the judicious choice of the resistor may lead to a significant absorption. The use of a waveguide simulator to characterize the performance of the loaded HIS is investigated. These methods have been used to design an ultra-thin absorber about λ8.4 GHz/35 thick.

This paper presents an analysis of totem-pole (TP) stages for driver applications and summarizes the major design constraints for an optimization with respect to P1dB, OIP3, and bandwidth. It is shown, that for matched drivers, in contrast to the widely applied common collector (CC) stage, class-AB TP stages offer higher output power and much higher power-added efficiencies (PAE) at comparable bandwidth. A combiner chip in 0.25 μm SiGe Bipolar CMOS (BiCMOS) verifying this concept in hardware as output driver is demonstrated proofing the increased achievable output power, which was measured greater than +0.1 dBm. This is approximately 11 dB higher than for a conventional CC driver. Furthermore, a concept is proposed, where the TP stage can act as a broadband matched driver for differential or balun operation ranging down to DC. As verification a broadband driver design using a class-AB TP stage is presented, which has a 3 dB bandwidth of 7.9 GHz and delivers up to +4.3 dBm into a 50 Ω load, which is 17 dB higher than its CC counterpart. At this output power it consumes a DC power of 12.3 mW and yields a PAE of 16.1%.

Confocal microwave imaging for breast cancer detection relies on accurate knowledge of the average dielectric properties of the patient-specific breast. When accurately estimated, coherent addition will occur at the tumor site, producing a clear and sharp image thereof. Conversely, if the average dielectric properties are poorly estimated, a blurred, unfocused image will be reconstructed, potentially obscuring cancerous lesions. Several methods have been proposed to estimate the patient-specific average dielectric properties, for example, time-of-flight estimation. However, such methods are specific to the individual imaging hardware, can be susceptible to multipath propagation and assume the chosen paths are representative of the whole volume. In this paper, a novel method to estimate the patient-specific average dielectric properties is presented, based on focal quality metrics (FQMs); used historically to measure the clarity and focus of microscopic or digital photographic images. These FQMs are applied to confocal microwave breast images to assess their focus, and hence estimate the patient-specific average dielectric properties. In this way, FQMs can be used to generate the optimum microwave image of the breast. The performance and robustness of these FQMs for microwave breast imaging applications is examined in this paper and preliminary results are presented and discussed.

A dualband rejection filter and a triband rejection filter are proposed in this letter, both of which are implemented by cascading spoof surface plasmon polaritons (SSPPs) of the same structure but with diverse rejection bands. Compared with traditional ones, the proposed filters provide more compact structures, wider rejection bands, and better independent tunability. In the proposed filters, the rejection bandwidth, the center frequency of the rejection band and the filter's cutoff frequency can be adjusted independently. And the different rejection bands in the same filter also can be independently controlled. Agreements between the dispersion of SSPP units and the S21 of filters are also presented. Measurement results demonstrate that both filters load multiple rejection bands on the 27.7 GHz wide low-pass band and all the rejection bands locate in Ku and K bands. The average rejection bandwidth and the average rejection depth of the two filters are 1.49 GHz and 42.1 dB, respectively.