This paper presents a new class of quasi-elliptic pass-band filters in substrate-integrated waveguide technology, which exhibits compact size and modular geometry. These filters are based on mushroom-shaped metallic resonators, and they can be easily implemented using a standard dual-layer printed circuit board manufacturing process. The presented filters exploit non-resonating modes to obtain coupling between non-adjacent nodes in the case of in-line geometry. The resulting structure is very compact and capable of transmission zeros. In this work, the singlet configuration is preliminarily investigated, and a parametric study is performed. The design of three-pole, four-pole, and higher-order filters is illustrated with examples and thoroughly discussed. A four-pole filter operating at the frequency of 4 GHz has been manufactured and experimentally verified, to validate the proposed technique.

Vehicle-to-everything communications (V2X), whose main objective is to improve security and efficiency, are provided by ad hoc vehicle networks that allow communication between vehicles. In the current study, a hexagonal microstrip patch antenna has been developed to cover the navigational frequencies, WiMAX at 3.7 GHz and DSRC/IEEE802.11p at 5.9 GHz to meet the demands of various vehicular applications. The antenna design is based on Cantor fractal slot, partial ground plane, and inset feed which is directly fed through the microstrip line. The proposed antenna shields the frequency band from 3.22 to 6.5 GHz with VSWR $\lt$2 within all the frequency bands. The presented antenna can resonate well in the 5.85–5.95 GHz band assigned for DSRC/IEEE802.11p and 3.7 GHz assigned for LTE/V2X. Simulated antenna gain varies from 3.06 to 5.25 dB within the operated frequency range providing an omnidirectional simulated radiation pattern in the most azimuth plane. To prove the validity of the simulation results, the chosen antenna structure has been fabricated and tested using a vector network analyzer MS2630. The measurement shows good results, which make the antenna suitable for wireless applications of interest.

In this paper, a vase-shaped monopole antenna is presented for dual band notch (WiMAX IEEE802.16 3.30–3.80 GHz with C-band 3.80–4.20 GHz and WLAN IEEE802.11a/h/j/n 5.15–5.35 GHz, 5.25–5.35 GHz, 5.47–5.725 GHz, 5.725–5.825 GHz) UWB and other wireless services (close range radar: 8–12 GHz in X-band & satellite communication: 12–18 GHz in Ku-band). Measured VSWR of proposed antenna shows a high band-rejection for WiMAX along with C-band with VSWR = 25.33 at 3.77 GHz and WLAN with VSWR = 6.0 at 5.64 GHz is achieved by cutting two C-shaped slots on the radiating patch. Designed antenna covers a wide usable fractional bandwidth 160% (2.58–20.39 GHz). Furthermore, the measured gain of antenna is relatively stable across the impedance bandwidth except band-notched. In addition, antenna offers omni-directional pattern, reasonably small 20 × 20 × 0.787 mm3 and easy to construct structure.

Asymmetric slits loaded irregular shaped microstrip patch antenna with three different ground structures is proposed. All three antennas show triple band characteristics. First antenna with regular ground plane resonates at 1.95, 2.4, and 4.90 GHz with good radiation characteristics and shows right-hand circular polarization at 1.95 GHz. 18.75% of compactness is achieved with triple band characteristics. Further, same patch is used with different defected ground structures. Second antenna resonates at 1.85, 2.4, and 4.85 GHz with suppressed cross-polarization level and antenna shows right-hand circular polarization at 1.85 and 4.85 GHz. Compactness is further improved to the value of 22.91%. The third antenna resonates at 1.95, 2.4, and 4.85 GHz with better gain and radiation characteristics and antenna shows right-hand circular polarization at 1.95 and 2.4 GHz. The small frequency ratio f2/f1 is achieved and the value of f2/f1 is 1.29 and 1.23 for second and third configuration, respectively. Proposed structures show right-hand circularly polarized with suppressed left-hand circularly polarized radiations and suitable for fixed mobile wireless communication applications. All structures are analyzed using Ansoft HFSS v.14 based on finite element method and measured results satisfy the simulated results.

Two localization algorithms for multilateration systems are derived and analyzed. Instead of the classical time difference of arrival (TDOA), a direct use of the time of arrival (TOA) is made. The algorithms work for arbitrary spatial dimensions and overdetermined systems. These derivations are tested in a real-case implementation with simulated data (in particular, the multilateration (MLAT) system installed on the Malpensa Airport in Milan was considered for the MLAT simulation and its possible extension to wide area multilateration (WAM) system was considered for WAM trials). The results are also compared with the present-day algorithms performance, mostly based on TDOA.

In this paper, a fractal-based complementary split-ring resonator (CSRR) has been introduced as a defected ground structure (DGS) in the ground plane of a dual-mode microstrip bandpass filter to produce a new compact filter with dual-band response. The conventional double square ring resonator structure is modified such that its inner ring is made with a fractal shape instead of a square. Measured and simulation results show that the resulting filter offers a dual passband response; the higher passband is attributed to the dual-mode microstrip ring structure, whereas the lower passband is as a result of the embedded CSRR DGS structure. In addition, the results show that the position of the lower passband could be varied, to a certain extent, without affecting the position of the higher passband by applying higher fractal iteration levels to the inner split ring. These features, together with the compact size the proposed filter offers, make it suitable for use in a wide variety of dual-band communication applications. Measured results, carried out on filter prototypes, have been found in agreement with those theoretically predicted.

This paper introduces a new maritime search and rescue system based on S-band illumination harmonic radar (HR). Passive and active tags have been developed and tested while attached to life jackets and a small boat. In this demonstration test carried out on the Baltic Sea, the system was able to detect and range the active tags up to a distance of 5800 m using an illumination signal transmit-power of 100 W. Special attention is given to the development, performance, and conceptual differences between passive and active tags used in the system. Guidelines for achieving a high HR dynamic range, including a system components description, are given and a comparison with other HR systems is performed. System integration with a commercial maritime X-band navigation radar is shown to demonstrate a solution for rapid search and rescue response and quick localization.

A novel coplanar waveguide-fed Z-monopole antennas are proposed for the first time for a industrial, scientific, and medical (ISM) band (2.4–2.48 GHz) applications. To make the designed antenna suitable for implantation, it is embedded in biocompatible Al2O3 ceramic substrate. The antenna operates at resonance frequency of 2.45 GHz to support wide band communication for high data rate implantable neural monitoring application. The size of the antenna is 38.675 mm3 (8.5 mm × 7 mm × 0.65 mm). The antenna was simulated and measured by immersing it in a phantom liquid, imitate the electrical properties of the human body phantom liquid. The simulated and measured bandwidths are 10.2 and 11.4% at the centre frequency. A study of the sensitivity of the antenna performance as a function of its dielectric parameters of the environment in which it is immersed was performed. The demonstration among the design EM characteristics of the antenna is presented by current distributions.

In this paper, a novel compact microstrip low-pass filter (LPF) with ultra wide stop band and sharp roll off, is proposed. In the proposed structure, a high impedance transmission line is loaded by compact microstrip resonant cells, which results in ultra wide stopband. The −3 dB cut-off frequency of filter is 1.5 GHz and the maximum insertion loss is <0.1 dB in the passband. The proposed LPF presents extremely wide stopband from 1.68 to 44 GHz, with more than the −20 dB attenuation level, which suppresses the 2nd to 29th harmonics with high rejection levels. The size of the proposed LPF is only 0.1 λg × 0.19 λg, which shows excellent size reduction. There is a good agreement between the simulated and measured results.

A large-signal model and a simulation technique based on non-sinusoidal voltage excitation are used to obtain the electric field snapshots from which the series resistance and related high-frequency properties of a 35 GHz Silicon Single-Drift Region (SDR) Impact Avalanche Transit Time (IMPATT) device have been estimated for different bias current densities. A novel method is proposed in this paper to determine the parasitic series resistance of a millimeter-wave IMPATT device from large-signal electric field snapshots at different phase angles of a full cycle of steady-state oscillation. The method is based on the depletion width modulation of the device under a large-signal condition. The series resistance of the device is also obtained from the large-signal admittance characteristics at threshold frequency. The values of series resistance of a 35 GHz SDR IMPATT diode obtained from the proposed method and the large-signal admittance method are compared with experimentally reported values. The results show that the proposed method provides better and closer agreement with the experimental value.

This research investigates the MIMO antenna by using the Theory of Characteristics Mode (TCM) where 10 modes are subjected in designing. Also, 5 modes are the significant mode and 2 modes correspond to non-significant which defines the operating bandwidth and notched bands. The proposed 2 × 2 MIMO antenna configuration is designed for wideband applications with a size of 0.44 × 0.68 mm2. The two isolated 12-sided polygons radiating patches placed adjacent to each other share a common ground which is printed on an FR4 substrate. The measured impedance bandwidth covers bandwidth 3.11–11.98 GHz with two bands rejecting capability: Wireless Local Area Network (WLAN) and Downlink-Uplink Satellite (DUS) system. These two interfering bands are mitigated by etching a C-type slot on the radiating patch and an inverted U-type slot in the microstrip feed. The simulated and measured results are also compared in the far-field region (Normalized Radiation Efficiency (NRE), Peak Gain (PG), and 2-D/3-D radiation pattern). Proposed MIMO antenna also offers good diversity performance with ECC2×2 < 0.00001, DG2×2 > 9.999 dB, TARC2×2 < −15.0 dB, CCL2×2 < 0.001 b/s/Hz and MEG2×2 ≅ −3.0 dB.

This paper presents an efficient approach for the design of a non-uniform single ring circular antenna array (CAA) for the synthesis of the optimal far-field radiation pattern. A recently proposed meta-heuristic-based optimization technique known as ant lion optimization (ALO) is applied in this paper to determine the optimum set of current amplitude excitation weights and the inter-element distance among the array elements to reduce the side lobe level (SLL) and 3-dB beam width considering the mutual coupling effect. The results achieved by employing the ALO algorithm are compared with the uniform radiation pattern and with those of the recently reported literature containing equal sets of elements to prove the superiority of ALO algorithm. Three different design examples of 8, 10, and 12 elements CAA are presented, and their performances are compared to illustrate the capability of the ALO algorithm-based approach over those of the recently reported literature.

Different types of bondwire interconnect for differential chip-to-antenna and single-ended chip-to-chip interfaces are investigated. Two differential compensation structures for various lengths of interconnects are designed and experimentally evaluated using dedicated transmit and receive radar modules operating across a 110–156 GHz band. Measurement results demonstrate that a fractional bandwidth of 7.5% and a minimum insertion loss of 0.2 dB can be achieved for differential interconnects as long as 0.8 mm. Design and measurement results of an extremely wideband low-loss single-ended chip-to-chip bondwire interconnect that features 1.5 dB bandwidth from DC to 170 GHz and insertion loss of less than 1 dB at 140 GHz are presented as well. The results show that the well-established wire-bonding techniques are still an attractive solution even beyond 100 GHz. Reproducibility and scalability of the proposed solutions are assessed as well.

A 245 GHz sensor system for gas spectroscopy is presented, which includes a SiGe receiver (RX), a SiGe transmitter (TX), and a 0.6 m long gas absorption cell between the TX and RX. The integrated local oscillators of the RX and the TX are controlled by two external phase locked loops (PLLs), whose reference frequencies are swept with constant frequency offset for a low IF of the RX. The RX consists of a differential low noise amplifier (LNA), an integrated 122 GHz local oscillator (LO) with 1/64 divider, a 90° differential hybrid, and active subharmonic mixer. The TX consists of an integrated 122 GHz LO with 1/64 divider, and a frequency doubler. The RX and TX are fabricated in 0.13 µm SiGe BiCMOS with ft/fmax of 300/500 GHz. Using external dielectric lenses for the TX and RX, the absorption spectrum of gaseous methanol has been measured. The reference frequency of the TX-PLL is modulated for frequency-modulation spectroscopy. The performance of the sensor system is demonstrated by measuring the 2f absorption spectrum (second harmonic detection) of gaseous methanol.

In this paper, a complete design procedure, together with robust system validation approaches, is presented for implementing a high-performance re-configurable digital predistortion (DPD) test platform for compensating for nonlinear distortion and memory effects induced by radio frequency (RF) power amplifiers (PAs) in the transmitters of modern wireless communication systems. This hardware and software co-operated test system not only enables effective validation for DPD algorithm development, but also provides a high-performance and reliable hardware-based linearization test platform. The experimental test was applied on a medium power Doherty amplifier, which was designed for 3 G/4 G wireless communication base stations. By applying our DPD algorithms on the proposed platform, more than 30 dB improvements in adjacent channel power ratio can be achieved for Universal Mobile Telecommunications System and long-term evolution signal excitations.

This paper introduces a symmetric bar chart-shape (SBCS) microwave sensor for measuring permittivity of fluidic samples. For designing purposes, the introduced sensor was used based on the field changes between the SBCS and rectangular loop microstrip (RLM) structure. When a sample is placed on the sensing location, interaction between SBCS and RLM varies the field intensity. The vinegar samples were combined with water and then they are placed on the sensor. The change in field intensity changes the resonance frequency. However, there is a relationship between the permittivity of samples and the resonance frequencies. The proposed sensor is implemented on the substrate of RO4003C. The relative permittivity of samples changed from 59 to 77 and the resonance frequencies changed from 2.3 to 1.4 GHz. The quality factor is 3544 and the sensitivity is 2.2%.

This paper reports an exhaustive review of recent research progress in the development of millimeter-wave absorbers. With the advancement in technologies, microwave absorbers have shown their evolution in several applications such as defense, security identification, stealth technology, and several more. The importance of these absorbers is increasing due to electromagnetic interference (EMI) effects. Primarily, an abundant amount of absorbers has been developed in lower frequency bands and with the increasing demand for 5G technology, the usage of millimeter-wave bands has gained attention. This in turn requires the development of millimeter-wave absorbers to provide EMI shielding in several applications. Out of several materials, polymers have grabbed attention in the mitigation of EMI. An absorber that combines carbonaceous elements with polymers offers large design flexibility and tunability per the filler concentration. This paper focuses on the classification of these absorbers based on geometry as well as that by using polymers with their design challenges, merits, and demerits with their industrial applications. Comparative studies of geometrically based absorbers and polymeric-based absorbers are also shown.

This paper presents an original characterization method of trapping phenomena in gallium nitride high electron mobility transistors (GaN HEMTs). This method is based on the frequency dispersion of the output-admittance that is characterized by low-frequency S-parameter measurements. As microwave performances of GaN HEMTs are significantly affected by trapping effects, trap characterization is essential for this power technology. The proposed measurement setup and the trap characterization method allow us to determine the activation energy Ea and the capture cross-section σn of the identified traps. Three original characterizations are presented here to investigate the particular effects of bias, ageing, and light, respectively. These measurements are illustrated through different technologies such as AlGaN/GaN and InAlN/GaN HEMTs with non-intentionally doped or carbon doped GaN buffer layers. The extracted trap signatures are intended to provide an efficient feedback to the technology developments

This paper presents a compact microstrip tri-band bandpass filter (BPF) using two multimode stepped-impedance resonators (SIRs) with a 0° feed structure. The fundamental odd-mode and even-mode resonant frequencies and the third resonant frequency are utilized to determine the center frequencies of the tri-band filter. The mode-splitting technique is used by combining two SIRs with electrical coupling. Therefore, two modes generate one passband and the bandwidths can be controlled by the electrical coupling strength. The 0° feed network is applied to create one pair of transmission zeros at each side of all the triple passbands, resulting in high selectivity. Finally, a tri-band BPF with the central frequencies of 1.8, 2.4, and 5.8 GHz, and respective fractional bandwidths of 8.9, 12.5, and 5.3% are designed and fabricated. The simulated and measured results show a good agreement.

The progressions in the field of wireless technology can be highly attributed to the development of antennas, which can access high data rates, provide significant gain and uniform radiation characteristics. One such antenna called the Vivaldi antenna has attracted the utmost attention of the researchers owing to its high gain, wide bandwidth, low cross-polarization, and stable radiation characteristics. Over the years, different procedures have been proposed by several researchers to improve the performance of the Vivaldi antennas. Some of these different approaches are feeding mechanisms, integration of slots, dielectric substrate selection, and radiator shape. Correspondingly, the performance of a Vivaldi antenna can be increased by including dielectric lens, parasitic patch in between two radiators, corrugations, as well as metamaterials. This paper gives a systematic identification, location, and analysis of a large number of performance enhancement methods of Vivaldi antenna design depicting their concepts, advantages, drawbacks, and applications. The principal emphasis of this article is to offer an outline of the developments in the design of Vivaldi antennas over the last few years, where the most important offerings, mostly from IEEE publications, have been emphasized. This review work aims to reveal a promising path to antenna researchers for its advancement using Vivaldi antennas.