To improve detection performance of passive location system based on troposcatter, we propose a blind signal detection algorithm. According to our algorithm, complementary ensemble empirical mode decomposition decomposes the received signal into several intrinsic mode functions (IMFs). To reconstruct the signal and background noises, difference between the entropy of adjacent IMFs is utilized as a standard. Different IMFs are utilized to estimate threshold of energy detection algorithm and energy level of received signal. Simulation examples indicate that the proposed algorithm can blindly and effectively detect the signal.

A novel topology of high-gain millimeter-wave antenna compatible with substrate integration is presented. The antenna is composed of a planar discrete lens laid on top of a core dielectric, while the planar focal source is assembled on the bottom side. The antenna can be fabricated as a single, robust and compact module using standard low-cost PCB technologies, and is compatible with IC integration such as a transceiver circuit for fully integrated millimeter-wave front-end modules. The proposed architecture is studied with two compact V-band antennas (32 mm × 32 mm × 13.2 mm). The main design rules are demonstrated for unit cells, focal source, and planar lens at V-band. Promising performances in terms of gain (17.6 and 20.4 dBi), aperture efficiency (14 and 26%), and fractional 3-dB gain bandwidth (17 and 18%) are obtained experimentally for the two considered compact antennas.

Karlsruhe Institute of Technology (KIT) is doing research and development in the field of megawatt-class radio frequency (RF) sources (gyrotrons) for the Electron Cyclotron Resonance Heating (ECRH) systems of the International Thermonuclear Experimental Reactor (ITER) and the DEMOnstration Fusion Power Plant that will follow ITER. In the focus is the development and verification of the European coaxial-cavity gyrotron technology which shall lead to gyrotrons operating at an RF output power significantly larger than 1 MW CW and at an operating frequency above 200 GHz. A major step into that direction is the final verification of the European 170 GHz 2 MW coaxial-cavity pre-prototype at longer pulses up to 1 s. It bases on the upgrade of an already existing highly modular short-pulse (ms-range) pre-prototype. That pre-prototype has shown a world record output power of 2.2 MW already. This paper summarizes briefly the already achieved experimental results using the short-pulse pre-prototype and discusses in detail the design and manufacturing process of the upgrade of the pre-prototype toward longer pulses up to 1 s.

In this paper, a microstrip diplexer is designed based on a novel structure consisting of the meandrous and patch cells. It operates at 0.8 and 0.9 GHz for global system for mobile communications applications. The proposed diplexer is well miniaturized with an overall size of 0.01 λg2. It has the narrowband channels making it appropriate for the modern long-range communication systems, which are widely accepted by the industry. The introduced diplexer has the other advantages of low insertion and return losses and the good isolation between channels better than −30 dB. Moreover, there is a good upper stopband rejection so that the first and second harmonics are suppressed with a maximum level of −30 dB. The designing method is based on finding the effective parameters to control the resonance frequency, miniaturization and harmonic attenuation simultaneously. To validate the designing method and simulation results, the proposed diplexer is fabricated and measured. There is a good agreement between the simulated and measured results.

In this paper, a novel class of balun bandpass filters is presented on slot-line resonator (SLR) toward intrinsic balanced performance in amplitude and phase. The proposed balun filter consists of three inductive-coupled SLRs in the middle, one single-ended unbalanced port, and one balanced port with two terminals. According to the distinct field conversion from the slotline to the microstrip feeding line, good balanced performance in amplitude, and phase performance can be intrinsically realized over a wide frequency range. To validate the proposed technique, a prototype third-order balun filter is designed, fabricated, and measured. Both the simulated and measured results have demonstrated that the proposed balun filter can not only achieve good frequency selectivity but also exhibit intrinsic balanced performance in amplitude and phase.

In this study, a new microstrip patch antenna with wideband radar cross-section (RCS) reduction is presented. The RCS of the proposed antenna was reduced by subtracting the current-direction slots of the patch, with the radiation performance sustained not only for the current-direction subtraction, but also for the no modification in the ground plane. Modified and reference antenna were fabricated and measured. The simulation and measurement results showed that the modified antenna reduced the in-band and out-band RCS simultaneously with no detriment to the radiation performance. In the frequency band from 3.9 to 8.1 GHz, the RCS of the modified antenna was reduced in the whole band compared with the RCS of the reference antenna. The maximum RCS reduction was 7 dB at a frequency of 6.7 GHz.

To utilize the manipulation of wave properties by metamaterials, in this paper, a microstrip-fed patch antenna array, loaded with metamaterial superstrate, has been proposed. Under unloaded conditions, the conventional patch antenna array resonates at IEEE 802.16a 5.8 GHz Wi-MAX band with gain of 4.31 dBi and bandwidth of 425 MHz, whereas when each patch of this array is loaded with a metamaterial superstrate, composed with the pair of circular split ring resonators and wire strips, gain and bandwidth approaches to 11.9 dBi and 685 MHz, respectively, which corresponds to gain improvement by 7.6 dBi and bandwidth enhancement of 260 MHz. The proposed antenna is fabricated and tested to compare simulated and measured results. A good compliance is observed between these two results. Equivalent circuit model of the composite structure has been developed and analyzed.

A novel idea for generating directional electromagnetic beam using a metamaterial absorber for enhancing radiation from a microwave antenna in the S-band is presented herewith. The metamaterial structure constitutes the well-known stacked dogbone doublet working in the absorption mode. The reflection property of the dogbone metamaterial absorber, for the non-propagating reactive near-field, is utilized for achieving highly enhanced and directional radiation characteristics. The metamaterial absorber converts the high-spatial reactive spectrum in the near-field into propagating low-spatial spectrum resulting in enhanced radiation efficiency and gain. The gain of a printed standard half-wave dipole is enhanced to 10 dBi from 2.3 dBi with highly directional radiation characteristics at resonance.

Pulse compression technique allows a radar to achieve the resolution of a short pulse and the energy of a long pulse simultaneously, without the requirement of high-power transmission. Therefore, pulse compression radars have a low probability of intercept capability. The common types of pulse compression signals are frequency modulated waveforms and phase-coded waveforms, which have different properties. The optimum radar signal should have good immunity against deceptive jamming, good Doppler tolerance to detect high-speed targets, and low time-sidelobe level to detect weak targets nearby the strong ones. This paper reviews the current research in the commonly used radar signals, and presents their pros and cons, and compares between them in terms of Doppler tolerance, time-sidelobe level, as well as immunity against jamming in order to provide a reference for the researchers in the field of radar systems and electronic warfare.

This paper reports scanning microwave microscopy of CMOS interconnect aluminum lines both bare and buried under oxide. In both cases, a spatial resolution of 190 ± 70 nm was achieved, which was comparable or better than what had been reported in the literature. With the lines immersed in water to simulate high-k dielectric, the signal-to-noise ratio degraded significantly, but the image remained as sharp as before, especially after averaging across a few adjacent scans. These results imply that scanning microwave microscopy can be a promising technique for non-destructive nano-characterization of both CMOS interconnects buried under oxide and live biological samples immersed in water.

We present a continuously tunable 52-to-67 GHz push–push dual-core voltage-controlled oscillator (VCO) in a 40 nm bulk complementary metal–oxide–semiconductor (CMOS) technology. The circuit is suitable for 60 GHz frequency-modulated-continuous-wave radar applications requiring a continuously tunable ultra-wide modulation bandwidth. The LC-tank inductor is used to couple the two VCO cores. The fundamental frequency of the VCO can be tuned from 26 to 33.5 GHz, which corresponds to a frequency tuning range of 25%. The second harmonic is extracted in a non-invasive way using a transformer. The primary side acts simultaneously as a second harmonic filter. The VCO achieves in measurement a low phase noise of −91.8 dBc/Hz at 1 MHz offset at 62 GHz and an output power of −20 dBm. The VCO including buffers dissipates in the dual-core operation mode 60 mA from a single 1.1 V supply and consumes a chip area of 0.58 mm2.

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 substrate-integrated waveguide (SIW) mixed electric and magnetic coupling structure implemented on a single-layer substrate to create finite transmission zeros (TZs), which can be used to design microwave filters with higher frequency selectivity. Mixed coupling is realized by three slot-lines on the top metal plane combined with an iris-window between two adjacent SIW cavities. The electric and magnetic coupling can be separately controlled by adjusting the dimensions of the slot-lines and the width of the iris-window, and a controllable TZ below or above the passband can be produced. Furthermore, a detailed analysis of the mixed coupling structure is presented. To demonstrate the validity of the proposed structure, third- and fourth-order cross-coupled generalized Chebyshev bandpass filters are designed and fabricated using the standard printed circuit board process. The experimental results are in good agreement with the simulation results. The filters exhibit simple structure and good frequency selectivity.

Based on vector network analyzer Measurements, a model for the specular reflection behavior of printed circuit boards in the Terahertz range has been derived. It has been calibrated to suit the behavior of the measurements using a simulated annealing algorithm. The model has been tailored for integration to ray-tracing-based propagation modeling.

Compact broadband circularly polarized elliptical slot antenna arrays (CPESAAs) are devised based on 2 × 2 and 4 × 4 circularly polarized (CP) elliptical slot antennas and a sequential phase feed network. To realize the circular polarization, eight rectangular stubs are embedded in the feed structure to excite two orthogonal E vectors in 2 × 2 CPESAA configuration. Moreover, by taking four rectangular slots out from each array element, return loss and axial-ratio bandwidths are noticeably increased. The investigated simple array element has a compact size of 20 × 20 × 1 mm3. As well, 2 × 2 CPESAA occupies a compact size of 55 × 60 × 1 mm3, which operates within the frequency band 4.18–9.35 GHz. Thus, 76.4% of S11 < −10 dB and 51.4% of CP bandwidth (4.43–7.5 GHz) are covered. Moreover, proposed 4 × 4 CPESAA is printed on 110 × 110 × 1 mm3 FR4 substrate and covers the frequency band of 1.15–12.98 GHz with CP at 2.95–8.82 GHz. Throughout the study, the design process of the proposed antenna arrays are presented and discussed in detail.

This paper proposes a dual notched band ultra-wideband (UWB) bandpass filter (BPF) based on hybrid transition of microstrip and coplanar waveguide (CPW). The CPW in ground plane houses a stepped impedance resonator shorted at ends, and is designed to place its resonant modes within the UWB passband. The microstrips on the top plane are placed some distance apart in a back-to-back manner. The transition of microstrip on top and shorted CPW in the ground is coupled through the dielectric in a broadside manner. The optimized design of the transition develops the basic UWB spectrum with good return/insertion loss and extended stopband. Later, defected ground structure, embedded in CPW, and split ring resonators, coupled to feeding lines are utilized to develop dual sharp passband notches. The simulated data are verified against the experimentally developed prototype. The proposed dual notched UWB-BPF structure measures only 14.6 × 7.3 mm2, thereby justifying its compactness.

The next generation of wireless networks (5G) employs directional transmission at millimeter wave (mmW) frequencies to provide higher bandwidth and faster data rates. This is achieved by applying antenna arrays with proper beam steering capabilities. Rotman lens has long been used as a lens-based beamformer in electronically scanned arrays and its efficient design is important in the overall performance of the array. Minimizing the phase error on the aperture of the antenna array is an important design criterion in the lens. In this paper, a 7 × 8 wideband Rotman lens is designed. Particle swarm optimization is applied to minimize the path length error and thereby the phase error. The optimized lens operates from 25 to 31 GHz, which covers the frequency bands proposed by the Federal Communications Commission for 5G communications. The proposed optimized lens shows a maximum phase error of <0.1°. The proposed Rotman lens is a good candidate to be integrated with wideband microstrip patch antenna arrays that are suitable for 5G mmW applications.

This work proposes the utilization of a high gain and pencil beam reflectarray (RA) antenna at the reader of the frequency coded (FC) chipless radio-frequency identification (RFID) system to minimize the environmental reflections and increase the reading range. Moreover, the reader antenna should operate over ultra wideband (UWB) range of frequencies to accommodate multiple bits. However, the conventional antenna arrays cannot operate over UWB range of frequencies with high gain and pencil beam characteristics. Therefore, a novel UWB RA antenna dedicated to the chipless RFID reader is developed. The developed RA antenna operates over UWB range of frequencies from 4 to 6 GHz to fulfill the requirements of the FC chipless RFID system. Therefore, the antenna is successfully integrated with the FC chipless RFID tags, and a reading range of 1 m is achieved.

This work presents the design of two compact multi-standard low-noise amplifier (LNA) in a 28 nm low-power bulk CMOS process. The transistor parameters were optimized by the gm/ID method taking into account the parasitics and the behavior of highly scaled transistors. To cover the industrial science medical (ISM)-bands around 2.4 and 5.8 GHz, the WLAN band as well as the Ku band a bandwidth enhancement is required. Two versions of LNAs, one with vertical inductors and one with active inductors, are implemented and verified by measurements. The noise figure (NF) exhibits 4.2 dB for the LNA with active inductors and 3.5 dB for the LNA with vertical inductors. The voltage gain reaches 12.8 and 13.4 dB, respectively, with a 3 dB-bandwidth of 20 GHz. Both input referred 1-dB-compression points are higher than −12 dBm making the chips attractive for communication standards with high linearity requirements. The chips consume 53 mW DC power and the LNA with active inductors occupies a core area of only 0.0018 mm2, whereas the version with vertical inductors requires 0.021 mm2.

In this paper, a triple-wideband bandpass filter (BPF) with controllable bandwidths based on two multi-mode stub-loaded resonators (MMSLRs) and a triple-mode resonator is presented. The MMSLR is loaded with two identical folded open-ended stubs and a T-shaped stub. Each passband of the tri-band BPF is formed by four resonant modes, which provide sufficient bandwidths to meet various application requirement. By adjusting the lengths of open-ended stubs, three passband bandwidths can be controlled individually. The center frequencies of the triple-wideband BPF are allocated at 2.7, 3.67, and 5.44 GHz, with the 3 dB fractional bandwidths (FBWs) of 20.1, 14.7, and 26.3%. Among the three passbands, the highest one covers the 5 G WiFi band (5.15–5.85 GHz). The measured results of the proposed filter exhibit excellent agreement with simulated results.