This paper presents an experimental overview of linearity metrics using setups based on a PNA-X and a vector signal analyzer to evaluate key performance indicators of a transistor, such as noise power ratio and error vector magnitude, under unequally spaced multi-tone (USMT) and various quadrature amplitude modulation signals. The purpose of this study is to verify the feasibility of characterizing the linearity of transistors and RF power amplifiers on a PNA-X-based measurement bench by exploiting the statistical properties of the previously developed USMT signal, which allows NPR measurement in a single pass. The measurements were performed on an $8 \times 50\,\mu\,\mathrm{m}$ gate GaN transistor from UMS Foundry,operating on-wafer at 29 GHz.

This research introduces a cutting-edge approach to glucose monitoring, which is essential in many applications. The study developed a new non-invasive glucose monitoring system utilizing machine learning techniques. This system examines the reflection coefficient data gathered from glucose solutions using a Vector Network Analyzer. To showcase the system’s accuracy in predicting glucose levels, two distinct datasets were employed. The first dataset comprised glucose solutions with concentrations spanning from 0 to 200 g/L, while the second dataset included solutions ranging from 15 000 to 20 000 mg/L for enhanced precision. The system measured both datasets, and three machine learning algorithms – Decision Tree, Random Forest, and Support Vector Regression – were applied to the collected data. Furthermore, a grid search method was employed to optimize the hyperparameters for each model’s optimal performance. The findings revealed that the Random Forest yielded the best results across both datasets. For gram scale, the R2 value was 0.9995, indicating that 99.95% of the glucose level variance was accounted for, with a low RMSE of 1.1589 mg/dL. Moreover, in milligram scale dataset, the R2 value was 0.9932, and RMSE was 1.1119 mg/dL, confirming the model’s high accuracy. These experimental outcomes demonstrate that the proposed system can effectively predict glucose levels.

This article presents a microstrip phase shifter whose frequency-dependent phase response is designed to present the desired phase variation as a useful device for frequency-controlled antenna array systems. The architecture consists of the parallel connection of open-stubs on a main transmission line. The analytical model of the device is presented, its transfer function is derived and compared with a conventional transmission line. The theoretical results show that the phase and amplitude responses can be designed by selecting the number, the length, and the characteristic impedance of the open-stubs. In order to validate the frequency controlled phase shifter model an architecture is proposed, that consists of a three-port device based on a power divider with a phase shifter on one of the output ports and a conventional transmission line on the other. A prototype of this architecture has been manufactured to operate in a frequency range of 2.8 GHz to 3.4 GHz. The magnitude and phase measurements of the scattering parameters show good agreement with the theoretical predictions.

Based on the stubbed coupled line for matching a load, we design an impedance transformer matched the load of ${{\text{Z}}_{\text{L}}} = 100{\Omega }$, working at four frequencies in this paper. This proposed transformer comprises two sections of coupled line constructed from parallel-coupled transmission lines. Two different types of the proposed transformer are given and analyzed, and we derive carefully about the open-circuit form equations for impedance transformer. We fabricate an impedance transformer to certify the validity of design equations theoretically, and the frequency is measured at 0.7/2.4/3.6/5.3 GHz. The measured results are in good agreement with the simulated results at each frequency.

This article proposes a dielectric waveguide bandpass filter (BPF) with good stopband suppression based on different kinds of dielectric waveguide resonators (DWRs). Three distinct types of DWRs are modified from the traditional rectangular DWR, i.e., one with a metallized blind hole, one with a metallized U-shaped slot and another one with a pair of parallel ridges. These resonators are designed that their fundamental mode frequencies are basically the same and their higher-order modes are staggered. As a result, the higher-order modes can be suppressed to a certain extent when conducting BPF designs. For verification, a sixth-order BPF with an operating frequency band ranging from 3.4 to 3.5 GHz is designed, fabricated and measured. It is composed of the above three distinct types of DWRs, with a deliberate arrangement that prevents the DWRs of the same type from being adjacent to each other, guaranteeing that the harmonics are well suppressed. In measurement, the in-band return loss is better than 12 dB, the minimum in-band insertion loss is about 1.0 dB. Besides, the 20 dB out-of-band suppression reaches 6.9 GHz, which is almost twice the center frequency.

This paper presents a wideband balanced reflectionless filter based on the half-wavelength ring resonator. The proposed structure is simple and easy for manufacture. The design procedures are elaborately introduced. To promote understanding, the analysis of differential-mode (DM) and common-mode (CM) equivalent circuits are given. The corresponding equations are derived. For validation, a design example is fabricated and tested. The measured results verify its ability of transmitting DM signals and eliminating undesired CM signals. Specifically, the 21.6-dB CM suppression bandwidth can reach up to 273%, while the CM absorption bandwidth can reach up to 195%. The proposed balanced reflectionless filter exhibits excellent DM matching level, CM suppression level, and wide reflectionless bandwidth.

The existing intelligent optimization algorithms face challenges related to premature convergence in the synthesis of array antennas, resulting in low solution accuracy and a tendency to get stuck in local optima. In this paper, a logistic chaos and spiral flight dandelion optimizer (LSDO) algorithm is applied to sparse antenna array synthesis with constraints. To optimize the positions of the array elements and reduce sidelobe levels, the logistic chaotic mapping is employed for population initialization, which generates a diverse and uniformly distributed initial population. Additionally, the dandelion optimizer (DO) algorithms utilize a spiral flight strategy to enhance local exploitation capability and escape from the local optimum of the sidelobe level. For algorithm performance, numerical experimental results show the stability and robustness of the LSDO algorithm. For the optimization of planar sparse arrays, the LSDO algorithm significantly outperforms conventional optimization methods, achieving a peak sidelobe level (PSLL) reduction of 15.5% for DO, 9% for PSO, and 14.56% for IWO. These results confirm the effectiveness and superiority of the proposed algorithm.

Within this study, an optimized ultra-wideband (UWB) multi-input multi-output (MIMO) antenna incorporating band-rejection features is introduced for wireless application. The proposed design comprises four circular single-element antenna units that are designed on a Rogers RT/duroid 5880 (tm) support material having an overall size of 80 × 80 × 0.8 mm3 or 0.72λ0 × 0.72λ0 × 0.0072λ0 (λ0 is the free-space wavelength at lowest frequency 2.7 GHz) and positioned perpendicularly. To enhance isolation, cross-shaped extensions are incorporated. Measurement results indicate that this antenna demonstrates an impedance bandwidth of −10 dB, spanning from 2.7 to 11.67 GHz (125%) and penta-notched filters for 3.2–4.0 GHz, 4.49–5.05 GHz, 5.56–6.16 GHz, 8.23–8.56 GHz, and 10.29–11.53 GHz. The presented antenna is capable of filtering signals from WiMAX (3.3–3.7 GHz), N79 band (4.8–4.9 GHz), WLAN downlink (5.725–5.825 GHz), ITU-R (8.275–8.5 GHz) and Ku-band downlink (10.7–11.2 GHz). The antenna exhibits envelope correlation coefficients (ECC) below 0.04 and provides isolation superior to 20 dB. Experimental results indicate that the simulated characteristics closely match the measured ones. The developed MIMO antenna demonstrates strong suitability for ultra-wideband (UWB) wireless communication applications.

In this research work, a low-profile elliptical microstrip antenna has been designed with a recessed ground structure. A portion of the ground below the substrate has been cut out for the implementation of the recessed ground. Due to the recessed ground, the gain and bandwidth of the conventional antenna are increased along with the shifting of the resonant band toward high-frequency range. First-time theoretical analysis of the recessed ground is performed using a 2-D capacitance model to understand the effect of its dimensions on the dielectric constant of the antenna and the amount of shifting of the primary resonant frequency. A comprehensive parametric study of the dimension of the recessed ground was carried out to optimize the performance of the antenna. The conventional antenna without recessed ground generates a resonant frequency of 2.35 GHz with a resonant band of 2.28–2.4 GHz (S11≤−10dB) and a gain of −1.35 dB. After using optimum rectangular recessed ground, the resonant frequency of the conventional antenna is shifted to 2.58 GHz, occupying the 2.49–2.69 GHz frequency band with 0.5 dB gain. Therefore, the proposed antenna with recessed ground covers the 2.5–2.69 GHz WiMAX application band with enhanced gain and bandwidth.

This paper proposes a 38 GHz multi-beam wide bandwidth antenna based on the substrate integrated waveguide (SIW) Butler matrix. The proposed Butler matrix removes the 0° phase shifter and only consists of −90° hybrid coupler, crossover, and −45° phase shifter. A 4 × 4 Butler matrix is combined with a patch antenna to form a multibeam-wide bandwidth antenna that can switch beam angle. The antenna is integrated based on the SIW structure to produce ideal beam directions of −45, 15, −14, and 44°, and has low side lobe characteristics, allowing the antenna to maintain good transmission quality. The antenna can cover 33–42 GHz from the simulation and measurement results, with an effective bandwidth of about 24%. The antenna is easily fabricated on a single-layer planar substrate and is cost-effective. In addition, the antenna complies with human body radiation standards and will be widely competitive in the millimeter-wave in the future.

A highly compact microstrip low-pass filter (LPF) integrated, and meander-line-loaded substrate integrated waveguide (SIW) cavity-backed wideband filtenna with multiple radiation nulls (RN) is presented in this paper. A closed-loop quadrilateral slot is removed from the cavity to generate the first RN in the lower edge of the frequency band. Furthermore, an LPF is integrated with the feedline, which creates another RN at the upper edge of the pass band. The incorporation of the meander-line slot in the radiator and elimination of the C-shaped open loop slot from the bottom of the cavity improves the selectivity of filtenna significantly by generating two more RNs at each side of the pass band. The presented filtenna appears to have low profile and compact structure with wideband response of 17% fractional bandwidth (11–13.1 GHz) and 8.56 dBi peak gain in the pass band. In total, four RNs with more than 15 dB out-of-band rejection level and good lower and upper selectivities of 0.65 and 0.05, respectively, are reported, with close agreement between simulation and measurement. These profound properties make the proposed filtenna suitable for short-range radar and satellite communications, modern Radio Frequency (RF) front-end and wireless communication systems.

This paper presents the design and analysis of the Triple band Circular Quarter Mode Substrate Integrated Waveguide (QMSIW) 1 × 2 MIMO antenna for sub-6 GHz 5 G wireless applications. The antenna operates at three distinct frequencies those are 3.57GHz, 4.41GHz and 5.43 GHz respectively. The 3.57 GHz used to operate for WiMAX, 5 G, and Fixed Wireless Access, the 4.41 GHz, is often used for specific satellite uplink/downlink operations, Radar Systems and the third one 5.43 GHz is used for Wi-Fi, DSRC, and WLAN systems. The proposed architectural design underwent simulation utilizing electromagnetic (EM) tools to the extract results, followed by antenna fabrication and measured results, it was observed that there is a close match between the simulation, measured results and validated results. The measured, simulation gain values are 5.092dBi,4.98dBi at 3.57 GHz, 4.51dBi,4.6dBi at 4.41 GHz and 3.075dBi,3.06dBi at 5.43 GHz frequency, while also demonstrating satisfactory isolation between the ports, quantified as being less than −15 dB. The characteristic parameters of the MIMO antenna, including a diversity-gain (DG) surpassing 9.95 dB (>9.95 dB), alongside an envelope-correlation-coefficient (ECC) of less than 0.0001, Mean effective gain (MEG) lies between − 3 dB to − 4 dB, among any two radiating elements at every operational frequency, indicate that the antenna has been meticulously designed.

A work of compact dual-port transparent multiple-input multiple-output antenna optimized for fifth-generation (5G) N77 (3.3–4.2 GHz) and N78 (3.3–3.8 GHz) bandwidth has been simulated, investigated, and optimized for robust performance in high-speed wireless communication. It features an impedance bandwidth of 3–4.3 GHz with a minimum simulated return loss of −28 dB, with 100% 3-dB axial ratio bandwidth and a simulated gain of 3.5 dB. The conducting plane material is indium tin oxide (ITO), chosen for its high optical transparency and sufficient electrical conductivity to seamlessly integrate into visually demanding applications. The substrate is glass, chosen for its lightweight and durable properties, which enhance both the mechanical durability of the antenna and its electromagnetic performance. To validate the ITO-based simulated design, the prototype with the same geometrical specification has been fabricated with the conducting portion replaced with copper and substrate as glass material due to a lack of facilities for transparent antenna fabrication. The comparative investigation study between the proposed ITO-based transparent antenna and with copper-based prototype (simulated/measured) both on a glass substrate, has been discussed, which supports the findings.

In this paper, a wideband reconfigurable reflectarray antenna (RRA) using 1-bit resolution for beam scanning with two-dimensional (2D) capability is presented at Ku-band. A 1-bit RRA element with a rectangular patch embedded with slots is proposed for broadband operation. Each element is equipped with a single PIN diode, allowing for resonance tuning while ensuring low cost and minimal power consumption. According to the simulation results, the proposed element is capable of 1-bit phase resolution with a phase difference of ${180^\circ \pm 20^\circ}$ stability from 11.27 to 13.74 GHz, which corresponds to an approximate bandwidth of 19.75%. To demonstrate its capabilities, we developed, fabricated, and tested a wideband electronically RRA with ${14 \times 14}$ elements. The experimental results demonstrate that the realized maximum gain in the broadside direction is 21.1 dB with a peak aperture efficiency of 20.9%. 2D beam scanning within ${\pm50^\circ}$ angular range are obtained and the scan gain reduction is 1.88 dB for ${-50^\circ}$ scanned beam in E-plane while 2.21 dB for ${50^\circ}$ scanned beam in H-plane. The 1-dB gain bandwidth of the RRA is 15.1%.

To improve the compactness, broadband, high gain and wide coverage performance of the shortwave antenna (array), this paper introduces the array technology from the LPDA unit antenna, establishes the compact optimization model of the 2×3 elements LPDA fan-shaped array, and proposes an optimization method applied to the broadband decoupling and grating lobe suppression for LPDA fan-shaped phased array, taking the broadband low coupling and non-grating lobe as constraints; By using phased array technology, the wide scanning characteristics of LPDA fan-shaped array are analysed, and the influence of antenna parameters on the mutual coupling is studied when LPDA phased array widely scan. Finally, the feasibility of the truss based 2×3 elements LPDA fan-shaped phased array with a scale of 1:60 is verified through tests. The fan-shaped phased array has a frequency coverage of 13~28 MHz, an average gain of 17.5 dBi in the band, an average beam width of ≥ 30 °, and a scanning range of ≥ 90 °. The proposed array has the characteristics of broadband, low coupling, high gain, wide scanning and compactness. The proposed joint optimization method provides a very promising technical means for the optimization design of complex multi-dimensional phased arrays.