This paper describes the design and characterization of a compact substrate integrated waveguide (SIW) fed antenna for the 122 GHz industrial, scientific, and medical band. The use of a single RO4350B substrate layer and the SIW feeding ensure a low-cost fabrication. Two versions of the antenna are presented differing in antenna gain and size. For measurement purpose, a transition from rectangular waveguide to SIW is introduced. Measurements of the radiation pattern have been performed and show good agreement with the numerical results for both antennas and an antenna gain up to 7.14 dBi.

This paper presents a novel, simple, and efficient pulse generation technique using BJTs in avalanche mode with mixer effect. The presented design is an improved version of the basic single transistor avalanche pulse generator, and it composes of two identical pulse generators that drive a common 50-Ω load resistor at the output. The output signal exhibits wider bandwidth and narrower pulsewidth, compared to the basic single transistor circuit. The presented pulse generator also provides increased power output without using any power amplifier, and can be used in ground-penetrating radar and ultra-wideband communication systems.

This article presents the design of a novel sigma slotted circular monopole antenna for wireless body area network applications. The design is proceeded with a sigma-shaped slot etched on the circular radiator with Rogers 4003C substrate. The size of the proposed antenna is 30 × 30 × 1 mm3. With partial ground plane, the bandwidth characteristics of the antenna have been enhanced. The designed antenna covers 2–10 GHz of the ultra wideband, thereby providing more than 106% bandwidth. The antenna exhibits high gain values of 1.95, 3.23, 3.46, and 5.95 dB at 2.45, 3.45, 5.8, and 9.5 GHz, respectively. The proposed design operates on off-body mode at 2.45 GHz and on-body mode at 5.8 GHz, thus acting as a dual-mode antenna. To ensure the health and safety measure, specific absorption rate analysis was done for both low and high values of input power and also with Cartesian and cylindrical human arm models. Bending analysis was also done. The time domain parameter group delay was also analyzed for the proposed antenna for on- and off-body scenarios. The prototype was fabricated, and validation of simulation results was done for free space and on-body scenarios.

With the aim of performing perimeter surveillance of high-speed railway networks, this paper presents the design of a passive multistatic radar system based on the use of Long-Term Evolution (LTE) downlink signals as the illumination of opportunity. Taking into account the specifications and standard of the LTE system, the ambiguity function of measured downlink signals is analyzed in terms of range and Doppler resolution, ambiguities, and sidelobe level. The deployment of the proposed passive radar is flexible and scalable, and it is based on multichannel software defined radio receivers that obtain the reference and surveillance signals by means of digital beamforming. The signal processing and data fusion are based, respectively, on the delay-Doppler cross-correlation with the reconstructed reference signals and a two-stage tracking at sensor and central level. Finally, the performance of the proposed system is estimated in terms of its maximum detection range and simulation results of the detection of moving targets are presented, demonstrating its technical feasibility for the short-range detection of pedestrians, vehicles, and small drones.

Next-generation automotive radar sensors are increasingly becoming sensitive to cost and size, which will leverage monolithically integrated radar system-on-Chips (SoC). This article discusses the challenges and the opportunities of the integration of the millimeter-wave frontend along with the digital backend. A 76–81 GHz radar SoC is presented as an evaluation vehicle for an automotive, fully depleted silicon-over-insulator 22 nm CMOS technology. It features a digitally controlled oscillator, 2-millimeter-wave transmit channels and receive channels, an analog base-band with analog-to-digital conversion as well as a digital signal processing unit with on-chip memory. The radar SoC evaluation chip is packaged and flip-chip mounted to a high frequency printed circuit board for functional demonstration and performance evaluation.

Bessel, Bessel-Gauss, and Gaussian beams have widely been investigated in optics in the paraxial approximation, under the frame of a scalar wave theory. Such approximations can hardly be applied in the microwave/millimeter-wave range, where the vectorial nature of the electromagnetic fields cannot be neglected, and experimental realizations for some of these beams appeared only recently. In this work, we discuss the generation of Bessel, Bessel-Gauss, and Gaussian beams through a fully vectorial electromagnetic approach. The field derivation of all these beams is first illustrated and numerical evaluations are then reported to compare their different propagation and diffractive behaviors. Finally, an innovative approach for realizing such solutions with planar microwave devices exploiting leaky waves is demonstrated through accurate numerical simulations.

A compact dual-polarized monostatic antenna (single radiator for transmit and receive modes) is presented with differential receive mode operation to achieve excellent interport isolation for 2.4 GHz single frequency full-duplex or in-band full-duplex applications. The presented antenna comprises three ports radiating element (patch) and a simple 3 dB/180o ring hybrid coupler has been utilized for differentially excited receive mode operation. The 3 dB/180o ring hybrid coupler acts as a self-interference cancellation (SIC) circuit for effective suppression of RF leakage from the transmit port to provide very high interport decoupling between transmit and receive ports. A compact antenna structure has been realized by using two-layered printed circuit board through vias interconnections of both receive ports of the antenna with inputs of SIC circuit. The validation model of proposed antenna offers more than 95 dB peak interport isolation. Moreover, the experimentally measured interport isolation is better than 70 dB throughout the antenna's 10 dB return-loss impedance bandwidth (BW) of 50 MHz (2.38–2.43 GHz). Furthermore, the recorded isolation is more than 80 dB in 20 MHz BW. The implemented antenna has good radiation characteristics including nice gain and low cross-polarization levels as endorsed by measurements. Same antenna structure with microstrip-T feeds can provide DC isolated ports with same interport RF isolation performance for active antenna applications. Such antenna with DC interport isolation will avoid the requirements of additional series capacitors on transmit and receive ports of antenna.

For foreign object detection on runways, highly sensitive radar sensors give the opportunity to detect even very small objects, metallic and non-metallic, also under adverse weather conditions. As it is desirable for airport applications to install only small but robust installations along the traffic areas, millimeter-wave radars offer the advantage of small antenna apertures and miniaturized system hardware. A 220-GHz radar was developed, which is capable to serve this application, if several of these are netted to cover the whole traffic area. Although under fortunate conditions the radar allows a classification or even an identification of the debris, the complete system design incorporates 3-D time-of-flight cameras for assistance in the identification process, which are also distributed along the traffic areas. The system approach further relies upon a change detection algorithm on the netted information to discriminate non-stationary alarms and reduce the false alarm ratio.

We propose in this paper a 4-channel time-domain test bench for the characterization and linearity enhancement of microwave power amplifiers (PAs). The proposed time-domain measurement system utilizes four track and hold amplifiers (THAs) for direct subsampling of radiofrequency (RF) signals. The use of wideband THAs to replace samplers or mixers enables reducing analog IF circuit complexity. It permits direct digitization of RF signals like CW, two-tone and pulsed modulated signals, bringing more flexibility in the receiver's performance by enhancing the dynamic range and bandwidth. This test bench is capable of completely extracting the phase, amplitude, and transfer characteristics of non-linear devices excited with CW or modulated RF signals. In this work, two-tone transfer characteristics of a 50 W GaN HEMT Nitronex PA were extracted and processed for applying digital pre-distortion linearization to enhance linearity performance. Time-domain envelope and carrier waveforms (voltage and current) along with third-order inter-modulation distortion (IMD) products with and without digital pre-distortion scheme are also presented.

This study examines K-band rectangular waveguide terminations with three-dimensional (3D)-printed loads, and proposes an Asymmetrical Tapered Wedge topology. This geometry shows a good tradeoff between microwave performance and 3D-printing issues (printing directions and support material requirements), thus improving noticeably the reproducibility of the devices. The effect of the density of the 3D-printed load on the reflection parameter of the termination was investigated. Even for a low density, reflection level remained below −27.5 dB between 18 and 26.5 GHz. Reproducibility was demonstrated by the characterization of six loads that were 3D printed under the same conditions. Measurements demonstrate that a maximum reflection parameter level of −33.5 dB can be ensured over the whole frequency band without any post-machining of the 3D-printed devices.

Wireless connectivity has been realized for multiple environments and different frequency bands. However, little research exists about mmWave communication in industrial environments. This paper presents the 60 GHz double-directional radio channel for mmWave communication in a ship hull for Line-of-Sight (LOS) and non-Line-of-Sight (NLOS) conditions. We performed channel measurements using the Terragraph channel sounder at different locations in the ship hull and fitted LOS path loss to a one-slope path loss model. Path loss and root-mean-square delay spread of the LOS path is compared to the reflected path with lowest path loss. NLOS communication via this first-order reflected path is modeled by calculating the path distance and determining the reflection loss. The reflection losses have a considerable contribution to the signal attenuation of the reflected path. The channel models are implemented in an indoor coverage prediction tool, which was extended with a ray launching algorithm and validated by comparison with an analytical electromagnetic solver. The results show that the mmWave radio channel allows high-throughput communication within a ship hull compartment, even when no LOS path between the transmitter and receiver is present.

In this paper, a miniaturized tri-band bandpass microstrip filter using stub loaded rectangular ring resonator (SLRRR)，shorted stub loaded stepped impedance resonators (SSLSIR), and stepped impedance resonators (SIR) with sharp skirts is presented. Two SSLSIRs are embedded paralleled inside SLRRR to generate a quasi-elliptic response at second and third passband. The odd-even fundamental resonant mode and first high-order resonant mode of the SIRs are exploited to generate tri-band response. Three bandwidths can be controlled independently due to different signal paths. Extra transmission zeros are introduced by the configuration of 0° feed structure. Sharp skirts are achieved at the upper edge of each passband by λg/4 lines which are loaded at the I/O ports. An example of the proposed tri-band filter operating at 2.76 GHz/5.7 GHz/7.63 GHz for TDD-LTE/WLAN/VSAT applications is implemented and fabricated. The simulation and measurement show a good agreement.

A compact ultra-wideband (UWB) bandpass filter (BPF) based on surface-to-surface transition technology with features of extended stopband and integrated interference mitigation characteristics is proposed. The basic structure consists of a modified multiple-mode resonator (MMR)-based co-planar waveguide in the ground surface and coupled in broadside manner with the microstrip lines on the top surface. Later, two open-circuited stubs are embedded in the feeding lines and two complementary split ring resonators are etched in the MMR to implement multiple in-band transmission zeros so as to circumvent interference. A prototype is fabricated and measured to validate the results obtained in simulation. The proposed UWB-BPF is compact in size with overall dimensions of 17.82 by 11.08 mm2.

The mm-wave as well as avalanche noise properties of IMPATT diode at D-band are efficiently estimated, with different poly-types of silicon carbide (SiC) and GaN as base materials, using advanced computer simulation techniques developed by the authors. The breakdown voltage of 4H-SiC (180 V) is more than the same for 6H-SiC, ZB- and Wz-GaN-based diode of 170,158, and 160 V, respectively. Similarly, the efficiency (14.7%) is also high in the case of 4H-SiC as compared with 6H-SiC and GaN-based diode. The study indicates that 4H-SiC IMPATT diode is capable of generating high RF power of about 8.38 W as compared with GaN IMPATT diode due to high breakdown voltage and negative resistance for the same frequency of operation. It is also observed that Wz-GaN exhibits better noise behavior 7.4 × 10−16 V2 s than SiC (5.16 × 10−15 V2 s) for IMPATT operation at 140 GHz. A comparison between the power output and noise from both the device reveals that Wz-GaN would be a suitable base material for high-power application of IMPATT diode with moderate noise.

The substrate-integrated cavity-backed patch antenna embedded in dielectric-coated structure is presented. The aperture of antenna is covered with composite radome. The close proximity of radome to antenna severely degrades input impedance matching. The dielectric coating, a thick dielectric material, significantly deteriorates radiation pattern of antenna due to propagation of surface waves in the surrounding dielectric coating. The proposed planar electromagnetic bandgap structure reduces the propagation of surface waves in the dielectric coating recovering deterioration in the radiation pattern of the antenna. The problem of input impedance mismatching of antenna is resolved by placing a metallic strip on the top of the radome. The simulated results are in good agreement with measured results.

This paper presents a microwave absorber with dual absorption bandwidth response based upon the direction of electromagnetic wave incident on the surface. The design unit cell comprises a staircase shape metallic patch on the top plane and an array of 2×2 meander square ring shape dual layer frequency selective surfaces (FSS) in the middle and bottom planes. The relative absorption bandwidth (RAB) of 39.40% (5 GHz) with more than 90% absorption of incident wave power is achieved when an electromagnetic wave impinges normally on the top plane making it suitable for wideband applications in the X and Ku bands. For the wave incident normally on the bottom plane, the same structure gives narrow band absorption with an RAB of 2.29% (260 MHz) for more than 90% absorption around 11 GHz. Thus, this bi-directional ability of the proposed design is found to be suitable for radar absorbing material, multi-bandwidth, and diverse applications. The absorption performance is also studied for different values of incident angle. The distribution of surface currents on the staircase patch and on the two FSS layers at resonant frequencies of 11 GHz and 14 GHz is analyzed to elaborate the absorption phenomenon physically. The prototype of this design is fabricated and the experimental results are found to be closely following the simulated one.

In this paper, a novel single-cavity triangular substrate-integrated waveguide (TSIW) dual-band filter loading a complementary triangular split ring resonator (CTSRR) is proposed, which has three transmission zeros (TZs) in the stopband in total. The dual-band response is achieved by the CTSRR and the degenerate modes of the TSIW cavity. In order to control the TZs, we propose two adjustment techniques, shift feeding technique and adding via perturbation. In addition, the CTSRR etched on the surface can produce a new TZ in the upper first-passband. Finally, a dual-band filter with three TZs is simulated, fabricated, and measured. There is a good agreement between the simulated results and measured ones.

A miniaturized substrate-integrated coaxial line (SICL) bandpass filter with improved upper stopband using asymmetrical spiral stub-loaded resonators is presented in this paper. Owing to the space-filling feature of the spiral structure, the size of the proposed filter is significantly reduced. A theoretical analysis is carried out to examine the resonance property of the proposed resonator. It is found that the frequency ratios of the second and third harmonics to the fundamental frequency can be extended to 2.86 and 4.4. Benefiting from the circuit structure and SICL technology, the designed filter has a small size, wide stopband, low crosstalk, and high-density integration ability. The measured results show that the proposed filter, with dimensions of 0.051λ0 × 0.044λ0, operates at 1.056 GHz and the 20-dB rejection band is extended to 3.94f0.

The design and characterization of a broadband 20–480 GHz continuously tuneable on-chip spectrometer based on non-linear transmission lines in 65-nm CMOS technology is presented. The design procedure of the sampler that detects the ultra-broadband signal from the transmitter in time and frequency domain is described in detail. It consists of a non-linear transmission line, a passive pulse differentiator and a high-speed sample and hold-circuit. The relevance of the layout of the Schottky diodes in the sampler with a maximum RC-cutoff frequency of 430 GHz is described. Time domain and frequency domain measurements are presented to characterize the 480 GHz sampler bandwidth as well as the 3.1 ps sampler rise time. A signal to noise ratio of 90 dB at 100 GHz, 70 dB at 200 GHz and more than 30 dB at 480 GHz is reached. Two implementation of the spectrometer with antennas are presented, one with an on-chip antenna and one in a hybrid package. The antenna-less on-chip implementation of the transmitter and sampler requires no external lenses and is miniaturized to an area of 3 mm2. Future applications include analysis of fluids in microfluidic packages or droplet analysis in bio-medical or pharmaceutical applications.

This paper presents the theoretical formulation of a lithographical bending control (LBC) method that uses lithographical degrees of freedom to control the bending of a multilayered beam. LBC is applied to a piezoelectric actuator that uses PZT as the piezoelectric material. The theoretical model is compared with measurements using a weakly fixed bridge structure suited for curvature measurement.