Through-the-Wall Imaging is an ever-expanding area in which processing time, scanning time, vertical, and horizontal resolutions have been tried to improve. In this study, several methods are investigated to obtain efficient reconstruction of through-the-wall imaging radar signals with high resolution. Microwave radar signals, which are produced in YTU Microwave Laboratory, are processed by compressive sensing (CS). B and C scanned reflection data samples collected between 1 and 7 GHz frequency band are taken randomly at 1/4, 1/2 of whole amount and reconstructed by CS method. Considering the signal structure, 10 and 20 compressible Fourier coefficients are taken through CS to analyze the difference between them. In addition, we applied synthetic aperture radar (SAR) processing, also combined with SAR-Multiple Signal Classification over raw data. Experimental performance results are given and shown in the figures with high quality.

Piezoelectric materials have a strong interaction between their mechanical and electrical properties that translates into innovative components and circuits architectures. This work describes an original method using the electromechanical properties of the aluminum nitride (AlN) piezoelectric material to characterize its vertical extension when an electric field is applied. The novel techniques based on measurements of a planar parallel plate AlN capacitor without and with bias employing an impedance analyzer. The parallel plate capacitor theory and piezoelectric material analysis are used to calculate the vertical displacement of the AlN film.

This paper presents the design and implementation of an inverse class-F power amplifier (PA) using a high power gallium nitride high electron mobility transistor (GaN HEMT). For a 3.5 GHz continuous wave signal, the measurement results show state-of-the-art power-added efficiency (PAE) of 78%, a drain efficiency of 82%, a gain of 12 dB, and an output power of 12 W. Moreover, over a 300 MHz bandwidth, the PAE and output power are maintained at 60% and 10 W, respectively. Linearized modulated measurements using 20 MHz bandwidth long-term evolution (LTE) signal with 11.5 dB peak-to-average ratio show that −42 dBc adjacent channel power ratio (ACLR) is achieved, with an average PAE of 30%, −47 dBc ACLR with an average PAE of 40% are obtained when using a WCDMA signal with 6.6 dB peak-to-average ratio (PAR).

Carbon nanotubes (CNTs) are a unique group of materials with high aspect ratio, mechanical and electrical properties, which are of great interests in the field of interconnects, and radio frequency applications. In order to incorporate CNTs into any of these applications successfully, one important issue that has to be resolved is the critical parameters (temperature and reactant gases) associated with the growth of the CNTs. As such, the effect of these growth requirements on the adjacent components should be studied. In this work, we examined specifically the effect of carbon nanotubes growth on the underlying metallization, in particular gold, dedicated for radio-frequency-based applications. The gold coplanar lines were annealed at 800°C in a plasma-enhanced chemical vapor deposition (PECVD) system to simulate the worst-case condition. The reflection and transmission parameters were analyzed using a probe station connected to a vector network analyzer. Carbon nanotubes grown on different barrier layers were also characterized using a scanning electron microscope and Raman spectroscopy to identify a suitable barrier layer for gold. Our results showed that it is promising to integrate carbon nanotubes grown using PECVD onto Au coplanar waveguide without degrading the S-parameters measurements up to 20 GHz.

In this paper, a new reconfigurable microstrip fractal ultra-wideband antenna with a capability of variable rejection frequency bands is presented. The main patch of this antenna has two modified C-shaped gaps. Also, on these c-shaped gaps, 10 ideal MEMS switches are used to produce band-notch frequencies at six different frequencies of: 5.4 GHz (5.2–5.5), 5.8 GHz (5.7–5.9), 6.1 GHz (5.9–6.3), 7 GHz (6.9–7.2), 7.9 GHz (7.7–8.1), and 8.4 GHz (8.2–8.6). This antenna is fed by a 50 Ω microstrip line and works in a wide bandwidth of 2.9–11 GHz. The antenna is designed and fabricated on an inexpensive substrate of FR4. Dimensions of the antenna are 31.2 × 38.4 mm. Measurement and simulation results are in good agreement.

To prevent far-field radiation characteristics degradation while increasing bandwidth, an attempt has been made to design and fabricate a microstrip antenna. An electromagnetic band gap (EBG) structure, including a layer of a metallic ring on a layer of Rogers 4003C substrate, is used. For a better design, a patch antenna with and without the EBG substrate has been simulated. The results show that the bandwidth can be improved up to 1.6 GHz in X-band by adding the EBG substrate. Furthermore, using this structure, a dual-band antenna was obtained as well. Finally, to validate the simulation results, a comparison has been done between simulation data and experimental results which demonstrate good agreement.

A compact size hybrid fractal antenna is proposed for the application in wideband frequency range. The proposed antenna structure is the combination of Koch curve and self-affine fractal geometries. The Koch curve and self-affine geometries are optimized to achieve a wide bandwidth. The feed circuit is a microstrip line with a matching section over a rectangular ground plane. The measured impedance matching fractal bandwidth (S11 ≤ −10 dB) is 72.37% from 1.6 to 3.4 GHz. An acceptable agreement is obtained from the simulated and measured antenna performance parameters.

This paper presents, a dual-band bandpass filter using asymmetric stepped impedance stub loaded open loop resonator (OLR) for WLAN and WiMAX application. The outer OLR is realized to operate at lower passband of 2.45 GHz which is directly coupled to input and output ports whereas the asymmetric stepped impedance stub that loads the outer resonator contributes to 3.5 GHz passband. The introduction of asymmetric stepped impedance stub provides further control of improving the upper passband edge selectivity of second passband and in shifting the spurious modes away from second band thereby contributing to the wide upper stopband. The insertion loss is within 1.5 dB for each passband with 10 dB passband bandwidth of 250 MHz at both bands. A stopband up to 10 GHz is also obtained. A prototype is developed and the s-parameters obtained from electromagnetic simulation, equivalent transmission line model and measurement are in close agreement. The overall dimension of the filter is 25.45 × 15.89 mm2 which renders it a compact size.

This paper presents performances achieved with InAlGaN/GaN HEMTs with 0.15 µm gate length on SiC substrate. Technology Computer Aided Design simulations were used to optimize the heterostructure. Special attention was paid to the design of the buffer structure. I-V measurements with DC and pulsed bias voltages were performed. CW measurements at millimeter waves were also carried out and are detailed in the following sections. The technology, optimized for power applications up to 45 GHz, demonstrates a current gain cut-off frequency FT of 70 GHz and a maximum available gain cut-off frequency FMAG of 140 GHz. CW Load-pull power measurements at 30 GHz enable to achieve a maximum PAE of 41% associated with an output power density of 3.5 W/mm when biased at VDS = 20 V. These devices, with an improved buffer structure show, reduced recovery time in pulsed operating conditions. These improved characteristics should have a positive impact for pulsed or modulated signal applications.

This paper presents a novel approach for the determination of True-Speed-Over-Ground for trains. Speed determination is accomplished by correlating the received signals of two side-looking radar sensors. The theoretically achievable precision is derived. Test measurements are done in two different scenarios to give a proof of concept. Thereafter a series of field measurements is performed to rate the practical suitability of the approach. The results of the measurements are thoroughly evaluated. The test and field measurements are carried out using a 24 GHz frequency modulated continuous wave radar.

A highly integrated silicon platform (Hi-Mission) for high frequency applications is introduced. This platform utilizes heterogeneous Multi-Chip Module-Deposited (MCM-D) technology with integrated passive devices together with silicon and GaAs Monolithic Microwave Integrated Circuit (MMIC) technology developed for the automotive Ultra Wide Band (UWB) radar (short-range radar) frequency band from 77 to 81 GHz. Developments are described in the area of MCM-D process development, MMIC, integrated phased array antenna, module design, and assembly process development. The demonstrator is composed of two test vehicles designed for conducted and radiated measurements, respectively. Test results are presented at the component and module level.

The design, analysis, fabrication, and testing of a four-port multiple-input multiple-output (MIMO) antenna is reported in this paper for automotive communications. The MIMO antenna is constructed using the basic antenna element exploiting a slot geometry. Two such antennas are developed on the same microwave laminate to develop a two-port MIMO antenna. Two such microwave laminates are interlocked to create the four-port MIMO scheme. The most distinct feature of the proposed architecture is that the inter-port isolation is well-taken care without the need for an external decoupling unit. The four-port MIMO antenna has an overall volume of 32 × 15 × 32 mm3. The prototype MIMO antenna is fabricated and the measurements are carried out to validate the simulation results. The antenna offers ultra-wideband (UWB) characteristics covering the frequency range of 2.8–9.5 GHz. The average boresight gain of the antenna ranges from 3.2 to 5.41 dBi with the peak gain at 8 GHz. The simulated efficiency of the antenna is greater than 73% within the operating bandwidth. The MIMO parameters such as envelope correlation coefficient, diversity gain, and mean effective gain are evaluated and presented. The appropriateness of the proposed antenna for deployment in the shark fin housing of the present-day automobiles is verified using on-car performance estimation.

This communication reports significant isolation improvement utilizing planar suspended line (PSL) technique in ultra wideband (UWB) antenna for Multiple Input Multiple Output (MIMO) application. The antenna exhibits dual-band notched characteristic in Wireless Local Area Network (WLAN) band covering 5.45–5.85 GHz range; and in 7.15–7.95 GHz range for X-band downlink operations in satellite communication. Band-notching characteristics have been obtained by employing a single Elliptical Split Ring Resonator (ESSR) placed adjacent to each microstrip feed line of the radiating element and duo of “Y”-shaped strips employed within the circular ring of individual radiating elements. Two elements antenna occupy a compact space of 20 × 36 × 1.6 mm3 exhibiting huge measured impedance bandwidth (S11/S22 < −10 dB) covering 3.1–11.5 GHz and significant isolation of >21 dB in the almost entire band of operation. The electrical performance of antennas has been analyzed in terms of various MIMO parameters. Measured results demonstrate good accord with simulated results proving the competency of proposed antenna in high-density package systems and massive MIMO applications.

In this paper, a new miniaturized frequency agile filter-antenna with a wide reconfigurable frequency band is proposed for interweave cognitive radios (CRs). A tunable bandpass filter (BPF) composed of a symmetrical ring resonator is cascaded to the feed line of an ultra-wideband planar antenna. The structure of the proposed ring resonator BPF is simple and compact so that the total size of the proposed filter-antenna is smaller than that of a conventional system made of a separate antenna and BPF. The reconfigurability of the proposed filter-antenna is achieved by changing the operating frequency of the BPF by loading the ring resonator with a single varactor diode at its center. The fabricated prototype has successfully achieved a wide operational bandwidth of 1.43 GHz which covers continuous narrow bands from 4.65 to 6.08 GHz. Moreover, the operating tunable narrow bands have stable radiation characteristics. Good agreement between measurement and simulation results is demonstrated.

Different from traditional multiple-input and multiple-output (MIMO) radar, the frequency diverse array MIMO (FDA-MIMO) radar generates beampattern that is dependent on both range and angle, making it applicable for joint range–angle estimation of targets. In this paper, we propose a novel time reversal based FDA-MIMO (TR-FDA-MIMO) approach for target detection. Based on the time reversal theory, the TR-FDA-MIMO signal model is established, the TR transmitting–receiving and signal processing procedure are analyzed, and the resulting range–angle spectra for targets imaging are acquired by utilizing the multiple signal classification algorithm. Numerical simulations are carried out for both single and multiple targets cases. The imaging resolution and robustness to the noise of the proposed approach are investigated and results are compared with conventional FDA-MIMO radar. It turned out that by cooperating with TR, the performance of FDA-MIMO radar for target range–angle estimation is effectively enhanced, consequently improving its applicability in practical target-detecting cases.

This paper presents a high gain, wideband circularly polarized (CP) antenna. High gain of the antenna is achieved by employing a frequency selective surface (FSS) as a reflector. The antenna is a coplanar waveguide-fed structure with a modified L-shaped radiating patch. The unit element of the FSS is formed by connecting two modified dipoles at an angle of 90°. The antenna with reflector has a measured impedance bandwidth of 74.3% (2.2–4.8 GHz) and a 3-dB axial ratio bandwidth (ARBW) of 62% (2.2–4.18 GHz). The maximum boresight gain of the proposed antenna with reflector is 7.1 dB at 3.4 GHz. The radiation patterns of the antenna with the FSS are also measured and compared with simulated patterns. The various aspects of effect of FSS on CP antenna performance are also discussed.

A power MOSFET-based push–pull configuration nanosecond-pulse generator has been designed, constructed, and characterized to permeabilize cells for biological and medical applications. The generator can deliver pulses with durations ranging from 80 ns up to 1 µs and pulse amplitudes up to 1.4 kV. The unit has been tested for in vitro experiments on a medulloblastoma cell line. Following the exposure of cells to 100, 200, and 300 ns electric field pulses, permeabilization tests were carried out, and viability tests were conducted to verify the performance of the generator. The maximum temperature rise of the biological load was also calculated based on Joule heating energy conservation and experimental validation. Our results indicate that the developed device has good capabilities to achieve well-controlled electro-manipulation in vitro.

Proposed is a wideband, low profile, fully flexible, and all-textile-based slotted triangular antenna loaded with a 2 × 2 textile-inspired artificial magnetic conductor to be worn on the wrist. The integrated antenna design is designed to cover the frequency band from 3.1 to 6.5 GHz. The integrated design has two main resonances, where the first one is at 3.5 GHz, which can serve the WiMAX communication standard, while the second is at 5.8 GHz, which can serve the Industrial, Scientific and Medical (ISM)-band. The incorporated textile materials are composed of the conductive and dielectric fabrics that are realized by ShieldIt and Felt, respectively. When simulated against the human model wrist, the integrated antenna design displayed a realized gain of 6.71 dBi and radiation efficiency of 79.1%, at 3.5 GHz. Furthermore, at 5.8 GHz, it displayed a realized gain of 7.82 dBi and total efficiency performances of 66.1%. Moreover, it accomplished very low SAR levels within the antenna frequency band. Averaged over 1 g of tissue, it exhibited maximum SAR levels of 3.28 × 10−6 and 9.37 × 10−7 W/kg at 3.5 and 5.8 GHz, respectively. For the bent scenarios, the integrated antenna design displayed robustness when bent at an angle of 20 and 40°. Finally, measurement results are illustrated and analyzed. Based on the presented results, the suggested all-textile integrated antenna design might be designated for integration with the wristband to monitor the user health conditions through many possible frequency channels.

This work demonstrates a novel, reflective-type, dual-polarized multiband polarization transformer for various C to Ku band applications. The design constitutes a top FSS printed on a thin FR-4 grounded dielectric substrate. A y/x-polarized incident wave experiences linear-circular conversion from 4.61 to 4.71 GHz (right-hand circular polarized (RHCP)/left-hand circular polarized (LHCP)), 5.44 to 7.68 GHz (LHCP/RHCP), 10.13 to 14.98 GHz (RHCP/LHCP), and 16.68 to 17.19 GHz (LHCP/RHCP) with 3.41, 34.15, 38.63, and 3.01% FBW, respectively. In addition, it performs linear-cross conversions with a minimum 90% polarization conversion ratio (PCR) from 4.92 to 5.18 GHz, 8.32 to 9.41 GHz, and 15.56 to 16.25 GHz with 5.15, 12.30, and 4.34% FBW. Multiple surface plasmonic resonances are responsible for these polarization conversions in different bands. The device performance is angular stable for both transverse electric (TE) and transverse magnetic (TM) incidences. The design novelty lies in compacted periodicity 0.112λL, low-profile thickness 0.037λL with a multi-conversion (switching the orthogonal circular rotation in consecutive bands), and stable angular response, which can potentially be used in real-time applications.

In this paper, the design of a new compact uniplanar coplanar waveguide-fed antenna for multiband wireless application is presented and investigated. This antenna has a compact size of 25 × 25 mm2 and consists of a three parallel stub optimized added on rectangular slot to the radiator patch and T-shaped which inverted in the ground plane. The final prototype antenna designing resonantes at frequency bands (2.4–2.9 GHz), (3.7–5.2 GHz), and (5.7–6 GHz) with a return loss less than −10 dB. Details of the antenna configuration, design, simulation, and experimental results are presented, investigated, and discussed. The compactness, simple feeding technique, and conception of the uniplanar design make it easy to be integrated within devices of multiples wireless applications.