A finite-ground coplanar waveguide (FGCPW)-fed compact ultra-wideband flag-shaped monopole antenna is presented. The antenna consists of a FGCPW-fed monopole asymmetrically loaded with a rectangle strip. The antenna has a compact size of 21.85 × 28 × 1.6 mm3. Parametric analysis is conducted to understand the effect of various parameters on the antenna performance. Simple design equations are presented to provide reliable initial design of the antenna if a different substrate is to be used. Constant gain and monopole-like radiation patterns are observed along the entire operating range from 3.1 to 12 GHz. Investigation of the time domain characteristics reveals that the proposed antenna exhibits excellent pulse handling capabilities.

Null steering has been a challenge in radar communications for the past few decades. In this paper, a novel cognitive null steering technique in frequency diverse array radars using frequency offset selection is presented. The proposed system is a complete implementable framework that provides precise and deep null placement in the range and angle locations of the interference source. The proposed system is cognitive such that the transmitter and receiver are connected via a feedback loop. System extracts interference source location parameters from the radar scene using Multiple Signal Classification, a super resolution direction of arrival estimation technique. Neural networks known for minimum computation time, and good non-linear and non-parametric approximation have been utilized for prediction of next location of the interference source. Simulation results validate the proposed frequency offset selection by demonstrating precise and deep nulls at the desired locations.

Emerging intrinsically tunable film bulk acoustic wave(BAW) resonators allow the development of new generation reconfigurable and agile microwave circuits. In this paper, we demonstrate the enhancement of tunable performance of the high Q-factor BaxSr1−xTiO3 BAW – solidly mounted resonators (BAW–SMR) by varying Ba concentration. The Ba0.5Sr0.5TiO3 BAW–SMR reveal tunability of series resonance frequency up to 2.4%, electromechanical coupling coefficient up to 7.5% and rather high Q-factor, up to 250 at 5.3 GHz. Correlations between the measured electroacoustic parameters are analyzed using the theory of dc field-induced piezoelectric effect in paraelectric phase ferroelectrics. Higher coupling coefficient and tunability of resonance frequency of the Ba0.5Sr0.5TiO3 BAW–SMR are associated with higher tunability of permittivity. Strong anisotropy in field-induced piezoelectric effect is predicted with highest coupling coefficient in (001) direction of the BaxSr1−xTiO3 films. It is also shown that the tunability of series resonance frequency of Ba0.5Sr0.5TiO3 BAW–SMR is limited by relatively high and negative nonlinear electrostriction coefficient which is found to be m ≈ −4·1010 m/F. The BAW–SMR Q-factor is limited significantly by extrinsic acoustic loss associated with wave scattering at reflection from relatively rough top interface. The results of analysis show possible ways of further improvement of the performance of tunable BAW–SMR.

A fast, yet unconditionally stable, solution of time-domain electric field integral equations (TD EFIE) pertinent to the scattering analysis of uniformly meshed and/or periodic conducting structures is introduced. A one-dimensional discrete fast Fourier transform (FFT)-based algorithm is proffered to expedite the calculation of the recursive spatial convolution products of the Toeplitz–block–Toeplitz retarded interaction matrices in a new marching-without-time-variable scheme. Additional saving owing to the system periodicity is concatenated with the Toeplitz properties due to the uniform discretization in multi-level sense. The total computational cost and storage requirements of the proposed method scale as O(Nt2Nslog Ns) and O(Nt Ns), respectively, as opposed to O(Nt2Ns2) and O(NtNs2) for classical marching-on-in-order methods, where Nt and Ns are the number of temporal and spatial unknowns, respectively. Simulation results for arrays of plate-like and cylindrical scatterers demonstrate the accuracy and efficiency of the technique.

We review the AlGaN/GaN high electron mobility transistor (HEMT) activities in the Millimeter-Wave Electronics Group at ETH-Zürich. Our group's main thrust in the AlGaN/GaN arena is the extension of device bandwidth to higher frequency bands. We demonstrated surprising performances for AlGaN/GaN HEMTs grown on high-resistivity (HR) silicon (111) substrates, and extended cutoff frequencies of 100 nm gate devices well into the millimeter (mm)-wave domain. Our results narrow the performance gap between GaN-on-SiC (or sapphire) and GaN-on-silicon and establish GaN-on-Si as a viable technology for low-cost mm-wave electronics. We here contrast the difference in behaviors observed in our laboratory between nominally identical devices built on high-resistivity silicon (HR-Si) and on sapphire substrates; we show high-speed devices with high-cutoff frequencies and breakdown voltages which combine fT,MAX × BV products as high as 5–10 THz V, and show AlGaN/GaN HEMTs with fT values exceeding 100 GHz on HR-Si. Although the bulk of our activities have so far focused on AlGaN/GaN HEMTs on HR-Si, our process produces excellent device performances when applied to GaN HEMTs on SiC as well: 100 nm gate transistors with fT > 125 GHz have been realized at ETH-Zürich.

This paper presents slow-wave transmission lines based on non-periodic reactive loading. Specifically, the loading elements are stepped impedance shunt stubs (SISS). By sacrificing periodicity using SISS tuned to different frequencies, multiple transmission zeros above the pass band arise, and the rejection level and bandwidth of the stop band is improved as compared with those of periodic structures. Through a proper design, it is possible to achieve compact lines, simultaneously providing the required electrical length and characteristic impedance at the design frequency (dictated by specifications), and efficiently filtering the response at higher frequencies. These lines are applied to the design of a compact power splitter with filtering capability in this work. The length of the splitter, based on a 35.35 Ω impedance inverter, is reduced by a factor of roughly two. Moreover, harmonic suppression better than 20 dB up to the fourth harmonic is achieved.

Wide-band circularly polarized multi-input multi-output (MIMO) antenna array with a 2 × 4 feed network was proposed for C-band application. Different unique techniques were utilized in the proposed array to enhance the antenna characteristics, such as gain, 3 dB axial ratio bandwidth (ARBW), impedance tuning, and ruinous mutual coupling effects. A miniaturized dual-feed Tai chi-shaped antenna element with a pair of feeding points and a pair of eyebrow-shaped strips was presented for enhancing circular polarization (CP) purity and impedance matching. For a better improvement of CP features, a 2*4 MIMO sequentially rotated (MIMO-SR) feed network was used to achieve broader 3 dB ARBW. Besides, the MIMO feature of the feed network could control the left- and right-handed CP, respectively. Ultimately, specific forms of slot and slit structures were applied onto the top layer of MIMO feed network that provided a high isolation between the radiating elements and array network. Furthermore, the diversity gain (DG) was studied. The extracted measured results illustrated an impedance bandwidth of 3.5–8.2 GHz at port 1 and 3.5–8.3 GHz at port 2 for VWSR < 2 and 3 dB ARBW of 4.6–7.6 GHz at port 1 and 4.6–7.5 GHz at port 2. The peak gain of 9.9 dBi was at 6 GHz.

An analytical and a numerical study on coupling in microstrip transmission line (MTL) are reported for different split-gap orientations of a single gap square-shaped split-ring resonator (SRR). Taking both magnetic and electric couplings and adopting Lagrangian formulation for this coupled system, mathematical relations are found for each orientation of SRR to determine the connection between coupling co-efficient and resonant mode frequency. It is shown that coupling results in higher resonance frequency when the SRR, with parallel split-gap, has the gap far from the MTL. But, a lower resonance frequency is obtained when the SRR is placed at shorter distances with parallel split-gap near to the MTL. Again, for perpendicular split-gap orientation of SRR, the resonant frequency is found in terms of an effective coupling co-efficient; at shorter distances it is found to be lower than the fundamental resonance frequency of uncoupled SRR and an opposite effect is obtained at longer distances. Using CST Microwave Studio, the resonance frequency for each split-gap orientation of SRR is also studied as a function of separation between MTL and SRR. It is observed that this phenomenon strongly depends on SRR side-length, substrate height, and separation between MTL and SRR.

This paper presents compact rectenna arrays for ambient RF energy harvesting on the 2.45 GHz ISM band. The arrays are based on four and nine series-connected rectenna cells. Each cell is composed of a stacked fractal antenna and an RF-to-dc conversion circuit. The antenna is a compact third Koch fractal shape, fed by a coaxial probe for more compactness. The conversion circuit is a full-wave rectifier with a differential output, each DC polarity is provided by a two-stage Dickson voltage multiplier. Measurement results show a significant increase of the output DC voltage for the one, four, and nine cells rectenna arrays. They provide, for power density of 1.7 μW/cm2, an output DC voltage of 0.9, 2.2, and 4.1 Volts, respectively. The 9 cells rectenna array is used in a remote supply experiment of a temperature and acceleration wireless sensor, where the data are transmitted via a Bluetooth low energy link to a distant smartphone every 1 min.

This paper presents a wideband, low-cost, high-performance, and continuous phase shifter for millimeter-wave (mm-wave) phased array systems. Its operational principle is based on modifying the propagation mode of a grounded coplanar waveguide (GCPW) line by placing a high dielectric constant slab over the GCPW line. The propagation constant and hence the phase shift is varied by changing the air gap height between the GCPW line and the dielectric slab. As a proof of concept, a piezoelectric transducer is used to precisely control this air gap height. A printed circuit board-based phase shifter prototype has been designed, fabricated, and tested at two different frequency bands (19–21 and 28.5–30.5 GHz), which are the downlink and uplink bands, respectively, of the Ka-band two-way satellite communication system. A continuous and almost linear phase–voltage characteristic has been achieved experimentally with average phase shift variations 170° and 260° over the two bands, respectively. The footprint of the proposed phase shifter is 2.1 mm×3 mm, which is quite small and suitable for low-profile mm-wave applications. The average insertion losses over the two bands are <0.53 and 2.35 dB with very low variations±0.22 and ±0.35 dB, respectively.

In this paper, a low-power CMOS LC voltage-controlled oscillator (VCO) with body-biasing and low-phase noise with Q-enhancement techniques is presented. A self-body biased circuit is introduced that can reduce power consumption. Some derivations of the Q-enhancement and how to improve the phase noise of the circuit are also discussed. This chip is implemented by the Taiwan Semiconductor Manufacture Company 0.18 µm 1P6M process. The measurement results exhibit a tuning range of 14.7% from 4.92 to 5.7 GHz at a supply voltage of 1.4 V. The power consumption of the core circuit and figure of merit are 2.5 mW and −188.6 dBc/Hz. The phase noise is −118 dBc/Hz@1 MHz at an operation frequency of 4.94 GHz.

Electroporation has become a powerful technological platform for the electromanipulation of cells and tissues for various medical and biotechnological applications. Recently, nanoporation based on nanosecond pulsed electric fields (nsPEFs) has gained great attention due to its potential to permeabilize the membrane of small vesicles. Here, the authors propose and characterize, both experimentally and through multiphysics modeling, a grounded coplanar waveguide compliant with the wideband requirements for nanosecond pulses to be used for experiments of drug delivery with liposomes activated by nsPEFs.

In this paper, a novel two-stage fish spear-shaped multimode resonator (MMR)-based ultra wideband (UWB) bandpass filter (BPF) is presented. The fish spear-shaped MMR is loaded with stepped impedance resonator in order to improve the out-of-band performance of the proposed filter. The proposed UWB BPF filter has fractional bandwidth better than 110%. In order to validate the present design approach, the filter is fabricated on RT/Duroid 5880 having dielectric constant 2.2, thickness 0.787 mm and loss tangent of 0.0009. The measured passband bandwidth of the filter is from 3.3 to 11.85 GHz, with insertion loss of 1.5 dB and return loss better than 12 dB in the passband. The proposed filter has sharp selectivity and upper stopband with 20 dB attenuation from 12 to 24 GHz.

This paper considers the ability of polarization measurements for microwave remote sensing of clouds and precipitation. The simulation of reflections from liquid hydrometeors with a multi-polarization radar system is presented. The mathematical expression of energy received by a radar antenna with arbitrary polarization is obtained. The simulation of the energy redistribution of the signal reflected from liquid hydrometeors assembled over the antennas of multi-polarimetric radar for different wind conditions and different drop-size distributions is obtained and analyzed. The simulation results demonstrate the possibility to register wind and wind-related phenomena by polarimetric radar. The results of the paper can also be used to exclude an impact of drop vibration or oscillation into the radar signal to eliminate errors and underestimation during parameter measurements. The approach to segregate the reflected signal magnitude variations due to the wind-related phenomena from other factors is discussed.

In this paper, a solid co-planar waveguide-fed fractal metamaterial antenna is offered. The proposed design consists of Sierpinski gasket iterations and a complementary triangular split ring resonator (CTSRR) loaded underneath the substrate, which is accountable for pull off multiband uniqueness and resolve good impedance identical. In sketch to hassle multiresonant frequency band facet, these CTSRR are entrenched reverse side of the substrate. The anticipated antenna with a dense dimension of 12 × 14 × 1.6 mm3 is fabricated and tested. The testing result designates that the projected design has −10 dB of 5.72, 14.3, and 16.06 GHz, respectively, and covers 5.72 GHz wireless local area network, 14.3 GHz fixed satellite, and 16.06 GHz International Telecommunication Union (ITU) band. It has fine emission uniqueness for jointly E-plane and H-plane in all the preferred occurrence bands and produce superior performance compared with the offered antenna intend in the prose. The loaded CTSRR construction recital is validated all the way during negative permeability pulling out and assorted parametric study.

In designing a Foreign Object Debris (FOD) detection system on airport runways, this paper deals with the performance of a 77 GHz reflectarray antenna (RA). Debris may be very small and have low radar cross section (RCS), leading to design a high gain primary-fed offset RA. To minimize the aperture blockage, the main radiation lobe is in the specular direction. The antenna has a maximum gain of 40 dBi and aperture efficiency of 50% over the frequency band 76–77 GHz. First measurements using a 77 GHz radar module were carried out on pavement.

A 77-GHz–directional folded dipole antenna integrated in an embedded wafer level ball grid array package is presented. For the characterization of the antenna, a frequency multiplier is embedded, which scales the 4.25-GHz input signal up to 76.5 GHz and allows the use of a commercial signal source. The antenna structure is manufactured at the metallic layer, in the fan-out area of the package, and is directly connected to the monolithically integrated transceiver. The gain of the antenna is about 7 dBi, measured over a large bandwidth of about 8 GHz. The combination of the frequency multiplier with a 77-GHz transceiver and the on-package antenna is a promising approach for a system-in-package to future radar modules for automotive radar applications. Such a module avoids 77-GHz transitions to the printed circuit board and hence simplifies the design and manufacturing of the radar sensor significantly.

In this paper, authors report on an enhanced approach for the design of monolithic microwave integrated circuit (MMIC) power combining amplifiers. Commonly used techniques for the stabilization of such circuits are empirical and too conservative. This leads very often to a non-desired degradation of the radio frequency (RF) performances that are inherent to the physical properties of such stabilization networks at the fundamental frequency of operation. The methodology proposed here is based on the use of large-signal optimization processes that combine RF and stability analyses from the early stages of the design. This approach results in an improvement of the RF performances while sufficient stability margins are preserved. The optimization procedure is explained on a Ku-band MMIC power amplifier for space-borne communications.

A robust and tuneless micromachined waveguide diplexer operating in the frequency range 71–86 GHz is here presented. The diplexer is based on multiple coupled cavities and it is manufactured using micromachining technology on two staked silicon layers. The diplexer consists of two filters combined to a common waveguide port via an E-plane T-junction. The two eight-order band-pass filters are centered at 73.5 and 83.5 GHz. The fractional bandwidths for two bands are 8.8 and 7.8% at higher- and lower-band, respectively. The measured insertion loss is below 0.7 dB for both the filters and the diplexer isolation is better than 55 dB, as required. The proposed technology allows for a very compact device (<20 × 20 × 1.5 mm) and the first prototypes were proved to be very robust to manufacturing tolerances and environmental tests, thus leading to an excellent tuneless manufacturing yield in future production. The diplexer will be employed in next generation terrestrial radio-link communications front-ends.

In this paper, an orthogonal crossover artificial bee colony (OCABC) algorithm based on orthogonal experimental design is presented and applied to infer the marine atmospheric duct using the refractivity from clutter technique, and the radar sea clutter power is simulated by the commonly used parabolic equation method. In order to test the accuracy of the OCABC algorithm, the measured data and the simulated clutter power with different noise levels are, respectively, utilized to estimate the evaporation duct and surface duct. The estimation results obtained by the proposed algorithm are also compared with those of the comprehensive learning particle swarm optimizer and the artificial bee colony algorithm combined with opposition-based learning and global best search equation. The comparison results demonstrate that the performance of proposed algorithm is better than those of the compared algorithms for the marine atmospheric duct estimation.