A wideband orthogonally slot cut annular ring microstrip antenna fed by L-shaped probe is investigated using modal expansion cavity model and circuit theory approach. Simulation of the proposed antenna is performed using Ansoft HFSS and simulated results are compared with the measured and theoretical results. The impedance bandwidth of about 37.46% is observed at resonant frequency 3.15 GHz. The proposed antenna realizes an improvement in bandwidth of 13.46% and miniaturization in physical dimension about 10% from earlier reported structures. An improvement in bandwidth and miniaturization is due to thick substrate, L-probe feed, and orthogonally loaded slots. The measured results of fabricated antennas are in good agreement with simulated and theoretical results.

In this paper, we propose a frequency-reconfigurable antenna structure consisting of a dielectric resonator (DR) topped by a superstrate material. Two metasurfaces (MSs) are placed upon the DR and the superstrate, where these two MSs are utilized to synthesize a localized reduction of the dielectric constant of the DR. By placing switches into one of the MSs, the distribution of dielectric constant of the DR can be switched to one of two predefined distributions, which is equivalent to switching the DR length to two different lengths. Consequently, the frequency response of the proposed structure can be tuned to one of two operating bands. The excited modes inside the proposed antenna were obtained analytically and through simulations. Also, the dielectric constant value of substrates topped by MSs was analyzed. The antenna was fabricated and measured, and good agreement between simulation and measurement was attained. The antenna bandwidths are 7–8.1 GHz (14.7%) and 8.5–9.2 GHz (8%) and the gains are 5.1 and 7.8 dB, in the cases of having switches off and on, respectively.

High-order sub-harmonically injection-locked oscillators have recently been proposed for low phase-noise frequency generation, with carrier-selection capabilities. Though excellent experimental behavior has been demonstrated, the analysis/simulation of these circuits is demanding, due to the high ratio between the oscillation frequency and the frequency of the input source. This work provides an analysis methodology that covers the main aspects of the circuit behavior, including the detection of the locking bands and the prediction of the phase-noise spectral density. Initially, the oscillator in the presence of a multi-harmonic input source is described with a reduced-order envelope-domain formulation, at the oscillation frequency, based on an oscillator-admittance function extracted from harmonic-balance simulations. This allows deriving an expression for the oscillation phase shift with respect to the input source, and the average of this phase shift is shown to evolve continuously in the distinct synchronization bands obtained when varying a tuning voltage. This property can be used to detect the locking bands in circuit-level envelope-domain simulations, which, as shown here, can be done through different Fourier decompositions and sampling rates. The phase noise of the high-order sub-harmonic injection-locked oscillator under an arbitrary periodic input waveform is investigated in detail. The frequency response to the noise sources is described with a semi-analytical formulation, relying on the oscillator-admittance function in injection-locked conditions. The input noise is derived from the timing jitter of the injection source and the phase-noise response is shown to exhibit a low-pass characteristic, which initially follows the up-converted input noise and then the oscillator own noise sources. A method is proposed to identify the key parameters of the derived phase-noise spectrum from envelope-domain simulations. The various analysis methodologies have been applied to a prototype at 2.7 GHz at the sub-harmonic order N = 30 which has been manufactured and measured.

In this work, a new structure for the implementation of inline pseudoelliptic waveguide filters using non-resonating modes, based on asymmetric iris coupled transverse rectangular ridge resonators has been proposed. The basic structure is comprised of a ridge that is always centered and transverse to the waveguide center axis and has the ability to create a transmission zero (TZ) above or below the passband without involving any rotation of the ridge, thus enabling quicker design of the resulting filters by allowing the use of more efficient analysis tools like FEST3D, in addition to the more general purpose methods like HFSS. A centered ridge enables the ease of manufacturing through machining. The proposed structure makes use of rectangular waveguide's dominant TE10 mode as a non-resonating mode to create an alternate energy path from source to load, thus realizing a TZ, while the asymmetric irises excite the ridge resonator, enabling the overall structure to act as a singlet capable of producing both a pole and a TZ. A third-order filter with one TZ and a fifth-order filter with two TZs have been designed and manufactured. Measured results show good consistency with the simulated data, validating the viability of the proposed structure.

This work introduces a novel compact ultra-wideband (UWB) antenna designed for wearable applications, employing a bioinspired structure and machine learning (ML) techniques to achieve exceptional performance in the 3.10–10.42 GHz range. The antenna is fabricated by positioning conductive fabric on a polydimethylsiloxane polymer of 1 mm thickness to augment high flexibility and durability. Additionally, it pioneers integrating a complete ground plane to mitigate back radiation toward the human body, presenting a compact (35.5 × 30.5 × 1 mm3) UWB antenna design compliant with IEEE 802.15.6 standards. The design methodology includes using bandwidth enhancement techniques such as chamfering edges, slots, and adding stubs in the feed, along with applying ML to optimize the antenna’s dimensions for desired return loss characteristics. The proposed antenna demonstrates exceptional resilience to human body loading and physical deformation. The simulation and measurement results have good agreement. The K-nearest neighbour method beat the other ML algorithms maximum accuracy of 99.62% to predict the S11. According to the author’s best knowledge, this is the first compact UWB antenna with full ground specified by IEEE.802.15.6 with ML reported.

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.

The great interest of optical fiber links in communicating systems especially in ultra-wide band (UWB) communications has grown up in the last decade and requires co-simulation for mixed circuits design exploiting both optical and microwave domains. In this paper, we report an original modeling method of an electro-absorption modulator associated with a distributed-feedback laser to simulate an optical transmitter of an UWB over fiber system. Large signal optoelectronic device models can be developed and implemented in a high-frequency simulator, such as advanced design system-Ptolemy to analyze the performances of fiber radio links and study the impact of the transmitter characteristics. This specific simulation way, taking into account precisely electrical characteristics of both electrical and optical circuits, links two different frequency domains by coupling electrical and optical modules in the same system simulator. Therefore, a complete simulation of an UWB multi-band orthogonal frequency division multiplexing signal transmission over fiber with an external modulator is investigated.

The novel acoustic transversal topology has demonstrated to be a potential candidate for the development of the next generation of communication filters. The major asset of this topology is its capacity to achieve any filter response without the detriment of limited electro-acoustic coupling. Additionally, this topology prompts for an easy connection of different filters to create multiband and multiplexing responses. This study recalls and further details on the design of multiplexers based on transversal topology using bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators. An important practical aspect of this topology is the need of a BALUN stage at one port of the filter.

The use of the transversal topology is then applied to another type of acoustic resonator configuration, coupled resonator filter (CRF). Such a resonator configuration offers control over the phase of each transversal path, allowing us to eliminate the BALUN stage. CRF resonators are modeled by means of a different circuit model than BAW or SAW, which calls for a new synthesis procedure. This paper describes the synthesis approach and circuit transformation for the development of multiplexers based on the transversal arrangement of the CRF resonators. An example of a fully simulated 9-plexer is provided to verify this procedure.

This paper presents a low-power and low-noise amplifier (LNA) with resistive-feedback configuration. The design consists of two resistive-feedback amplifiers. In order to reduce the chip area, a resistive-feedback inverter is adopted for input matching. The output stage adopts basic topology of an RC feedback for output matching, and adds two inductors for inductive peaking at the high band. The implemented LNA has a peak gain of 10.5 dB, the input reflection coefficient S11 is lower than −8 dB and the output reflection S22 is lower than −10.8 dB, and noise figure of 4.2–5.2 dB is between 1 and 10 GHz while consuming 12.65 mW from a 1.5 V supply. The chip area is only 0.69 mm2 and the figure of merit is 6.64 including the area estimation. The circuit was fabricated in a TSMC 0.18 um CMOS process.

In this paper, the influence of the cutting plane as well as the orientation of the cavities in cross-coupled W-band waveguide filters are investigated. When waveguide filters are manufactured with the commonly known CNC (computer numerical control) milling technique, at least one cutting plane is required. The position of this cutting plane has an impact on the composition of the cavities, the manufacturing accuracy, and on the maximal number of transmission zeros (TZs) introduced by a direct source to load (SL) cross-coupling. Similar filter set-ups therefore may show different performances depending on the position of this cutting plane. To examine all these effects, three similar fourth-order W-band filter set-ups are realized with distinct cutting planes and different oriented cavities. The filters are compared in terms of the sensitivity to manufacturing tolerances, the maximal number of TZs introduced by a direct SL cross-coupling as well as their spurious mode performance.

A metasurface reflector-backed wideband planar antenna is designed for millimeter-wave (mmWave) applications. A simple meandering structure is used for radiation element design, while the back side consists of a partial ground plane and parasitic elements. The utilization of meander-shaped element led to small antenna dimensions. The partial ground plane is used to achieve wide bandwidth, while the parasitic elements are used to improve the impedance matching toward higher frequency bands. To achieve high gain and directional radiation characteristics, an array of metasurfaces is placed behind the radiating element. It is observed from the simulated results that the proposed antenna system offers 17.72 GHz of impedance bandwidth in the operating range of 22.28–40 GHz, while the measured impedance bandwidth is noted to be 15.8 GHz, ranging from 23 to 38.8 GHz. Furthermore, it is observed that a metasurface-based planar antenna tends to achieve a peak gain of ≈9 dBi in the band of interest.

We present a method for detecting parking spaces in radar images based on convolutional neural networks (CNN). A multiple-input multiple-output radar is used to render a slant-range image of the parking scenario and a background estimation technique is applied to reduce the impact of dynamic interference from the surroundings by separating the static background from moving objects in the scene. A CNN architecture, that also incorporates mechanisms to generalize the model to new scenarios, is proposed to determine the occupancy of the parking spaces in the static radar images. The experimental results show very high accuracy even in scenarios where little or no training data is available, proving the viability of the proposed approach for its implementation at large scale with reduced deployment efforts.

Two novel memory polynomial models are derived based on physical knowledge of a general power amplifier (PA). The derivations are given in detail to facilitate derivations of other model structures. The model error in terms of normalized mean square error (NMSE) and adjacent channel error power ratio (ACEPR) of the novel model structures are compared to that of established models based on the number of parameters using data measured on two different amplifiers, one high-power base-station PA and one low-power general purpose amplifier. The novel models show both lower NMSE and ACEPR for any chosen number of parameters compared to the established models. The low model errors make the novel models suitable candidates for both modeling and digital predistortion.

In this paper, we have analyzed the performance of correlated Nakagami-m fading channel by using the maximal-ratio-combing diversity at the receiver. A closed-form mathematical expression is derived for the average bit error rate (BER) for binary phase-shift keying (BPSK) and average symbol-error-rate (SER) for M-Quardrature amplitude modulation (M-QAM) scheme in terms of the higher transcendental function such as Appell hypergeometric function by using the well-known moment generating function (MGF)-based approach with arbitrary fading index for the orthogonal frequency division multiplexing (OFDM) communication systems. Moreover, we also derived an expression for the outage probability and the proposed numerical results are compared with the reported literature.

A compact circularly polarized antenna with wide axial ratio bandwidth (ARBW) using quasi-self-complementary (QSC) structure is presented. A 3-dB ARBW is achieved by shortening the ground plane of the QSC structure. Furthermore, the wide ARBW is obtained by the introduction of a stepped stub in the extended ground plane of the QSC structure. The antenna is fabricated on a FR4 substrate with the overall dimensions of 25 mm × 22 mm × 0.8 mm. The proposed antenna has an impedance bandwidth of 5.9 GHz (2.4–8.3 GHz, 110%) and 3 dB ARBW of 1.6 GHz (2.4–4 GHz, 50%). A peak gain of 1–3 dBi is observed within the 3 dB ARBW.

The scattering by the perfectly electric conducting (PEC) half-plane and PEC zero thickness disk placed on parallel planes is considered. The fields are represented in the spectral domain, i.e. in the domain of Fourier transform. The operator equations with respect to the Fourier amplitudes of the scattered field are obtained. The kernel functions of these equations contain poles. After regularization procedure, which is connected with the elimination of the poles, operator equations are converted to the system of singular integral equations. The convergence of the solution is based on the corresponding theorems. The scattered field consists of the plane wave, reflected by the infinite part of the half-plane, cylindrical waves, which appear as a result of scattering by the edge of the half-plane, and spherical waves, which appear as a result of scattering by the disk and multiple re-scattering by the disk-half-plane. The total near-field distribution and far-field patterns of cylindrical waves are presented.

This paper presents a design method of internally-matched packaged GaN high electron mobility transistors (HEMTs) for achieving not only high-efficiency and high-power performances but also a wide bandwidth and insensitivity to harmonic terminations in the S-band. The package and its internal matching networks are synthesized to confine the second harmonic impedances seen by the GaN die to high-efficiency regions whatever the harmonic impedances presented outside the package. This paper reports the design of a packaged GaN HEMT achieving 78% of power-added-efficiency (PAE) and 25 W of output power at 2.5 GHz. A packaged GaN power bar is also reported with the addition of fundamental matching networks inside the package. In 50 Ω environment, the packaged GaN power bar provided more than 56% of PAE from 2.5 to 3.1 GHz and was desensitized to harmonic load variations with less than two points of PAE variation when a load-pull is performed at second harmonic frequencies outside the package.

A coplanar waveguide (CPW)-fed circular-shaped fractal antenna with third iterative orthogonal elliptical slot for ultra-wideband applications is presented. The bandwidth is enhanced by using successive iterations of radiating patch, CPW feedline, and tapered ground plane. An impedance bandwidth of 2.9–20.6 GHz is achieved. The designed antenna has omnidirectional radiation patterns along with average peak realized gain of 3.5 dB over the entire frequency range of operation. A good agreement is observed between the simulated and experimental results. This antenna structure has the advantages of miniaturized size and wide bandwidth in comparison to previously reported fractal structures.

This paper presents a new planar particle that shows negative effective permittivity under irradiation by an electromagnetic wave. The mutual coupling between the couples of these particles is studied in particular. The response of this particle sensitive to an electric field is strongly anisotropic. The particle is aimed to be used to compose an isotropic epsilon-negative metamaterial in two forms. First, a unit cell of the metamaterial consists of a cube bearing six particles on its faces, located with specific orientations. The experiments showed that this unit cell is suitable for manufacturing an isotropic epsilon-negative metamaterial obtained by arranging these cells in a 3D cubic periodic system. The second form of an epsilon-negative metamaterial with an isotropic response consists of the planar particles themselves, distributed quasi-randomly, composing a 2D system and/or of particles placed in spherical shells and distributed fully randomly in a hosting material forming a 3D system. The isotropy of these systems was verified by measurements in a rectangular waveguide.

This paper presents a radio frequency (RF) continuous-time band-pass delta sigma modulator (CT BP DSM) receiver realized in a 180 nm SiGe BiCMOS technology. It also provides an introduction to active antenna systems (AAS) for cellular infrastructure base stations, which is the target application for this RF integrated circuit (IC). The internal quantizer and feedback digital to analog converter (DAC) resolution of the CT BP DSM is 2 bit. Without applying DAC linearization techniques such as trimming or dynamic element matching being utilized, measured performance parameters include an SNR and SNDR in 35 MHz bandwidth of 56.7 and 53.7 dB, respectively. IIP3 and noise figure are −6.6 dBm and 10 dB, respectively. No image reception is noticeable within a measurement dynamic range of 83 dB. When driven by single-carrier and three-carrier W-CDMA signals, adjacent channel leakage ratio (ACLR) is −62.6 and −52.1 dB, respectively, making the design also suitable as a modulator for a class-S power amplifier.