Due to the rising occupancy of the radio spectrum, new strategies for covering the ever increasing amount of data are necessary. This work presents a system for integrating data transmission into a frequency-modulated continuous wave (FMCW) radar by modulating the radar signal with frequency shift keying (FSK). The system offers a high chirp bandwidth of 5 GHz and uses the 60 GHz band. The FSK carrier frequency affects the noise level. A higher frequency leads to a lower noise floor due to 1/f-noise but requires a higher sampling rate. Therefore, 15 MHz was chosen as a compromise. A high data rate allows for a fast data transmission but requires a short chirp time, which leads to a noisier frequency chirp. The radar parameters are also affected by this choice. This leads to a baud rate of 20.8 kbit/s. With a higher order FSK, higher data rates are possible. This proves that the data transmission via FMCW radar signals is possible and a first choice if lower data rates are sufficient, because the hardware effort is comparatively low.

In this paper, we present the design, simulation, fabrication, and measurements of an on-chip dielectric resonator (DR)-fed millimeter-wave high-gain antenna system with in-antenna power combining capability. A low-profile resonant cavity antenna is fed by four spherical DR, showcasing the antenna’s multi-feed capabilities. Each DR is fed by two microstrip resonators located diagonally opposite on a planar circuit board and are excited via coaxial connectors. The design incorporates a printed partially reflecting superstrate, reducing the antenna’s overall size and profile while simultaneously enhancing directivity by approximately $10\,\mathrm{dB}$ at the design frequency of $30\,\mathrm{GHz}$. The antenna exhibits wideband matching. Key performance metrics, such as directivity, gain, beamwidth, and bandwidth, predicted by full-wave electromagnetic simulations align well with the results from experimental measurements.

This research explores a circularly polarized (CP) multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) designed specifically for 5G Sub-6 GHz and WiMAX applications. The antenna system utilizes a unique H-shaped feeding strip to excite each DRA element. This specialized feeding mechanism facilitates the activation of higher-order degenerate modes, including TE$_{\delta13}^x$ and TE$_{1 \delta 3}^{y}$, which are essential for achieving circular polarization. The antenna exhibits a reflection coefficient of −37.52 dB at 3.49 GHz, covering the entire CP passband and operating over a broad bandwidth of 1.35 GHz (3.40–4.75 GHz) yielding a return loss of 35.52%, making it suitable for Sub-6 GHz applications. An axial ratio bandwidth of 24.6% (3.4–4.2 GHz) is observed, with inter-port isolation of greater than −25.3 dB throughout the usable frequency band with a maximum efficiency of approximately 98%, indicating near-lossless power radiation. Additionally, the estimated gain is 5.95 dBic. The proposed MIMO design presented effectively reduces the intersecting spatial field components between antenna elements, leading to a lower envelope correlation coefficient and enhanced inter-port isolation. This diversity gain of the proposed antenna is a strong candidate for use in rich multi-path environments, helping to mitigate the effects of channel fading.. Initially, the proposed antenna design was examined using the time-domain solver of CST, followed by the fabrication of a prototype for experimental validation. The antenna exhibits a stable response, making it well-suited for 5G Sub-6 GHz and WiMAX applications.There is a satisfactory alignment between the results obtained from simulations and those observed experimentally.

Several breast microwave sensing (BMS) systems have shown encouraging results as a potential breast cancer detection tool. The existing systems in the literature have diverse designs, equipment, measurement protocols, and analysis methods. However, there is relatively little investigation on the impact and performance of varying system designs. This work compares the impact of system design parameters on three existing BMS systems. The first system, a bed-based system, was designed for use in a permanent clinic. The second system, a bench-top system, was created for laboratory research. The third system, a portable system, was designed for use in low-income and remote communities. The bed-based system had the highest resolving capabilities, achieving a spatial resolution of 12.4 ± 0.5 mm. Additionally, the bed system had the highest signal-to-noise ratio of 26 ± 1 dB. The portable system had the least intensity dependence on polar positions within the imaging chamber. The bed system had the highest contrast between tumor- and adipose-mimicking materials. However, the contrast of tumor- and fibroglandular-mimicking materials was similar for each system. By comparing and evaluating the performance of multiple BMS systems, we improve our understanding of system design, allowing for potential studies into an ideal BMS system.

INCUS (INvestigation of Convective UpdraftS) is a NASA Earth Science mission scheduled to launch in 2026. The goal of the mission is to study in detail how water vapor and droplets move inside tropical storms and thunderstorms and understand their effects on weather and climate models. To carry out this study, the mission will use three almost identical SmallSats, each equipped with a Raincube-heritage Ka-band radar. The deployable mesh reflector antenna is a new 1.6 m design provided by Tendeg, which is fed using a seven-horn feed assembly to generate overlapping secondary beams. This paper discusses the approach used to design and fabricate the feed assembly and presents the measured and calculated RF performance parameters.

This paper presents a vertically folded gap waveguide filter for use as the filter element for each antenna in an array of slotted waveguide antennas, at W-band. Loaded gap-waveguide resonators are used to reduce the footprint of the filter, and the filter is vertically folded to reduce the length. New input and output transitions are proposed, as well as inter-resonator coupling structures that conform to the basic gap-waveguide structure. A 7th order filter with a bandwidth of 10 GHz and a center frequency of 101 GHz is designed to meet geometric constraints of a transmitter system. A sensitivity analysis was performed on the structure to determine the required manufacturing tolerances. The filter was manufactured and measured yielding 10 dB of return loss in the passband and a detuning of the passband by 1 GHz. The return loss at 88 GHz peaked due to deviations in manufactured gap height in the gap waveguide. Deviations from the simulated response were accounted for with a parameter extraction from the measured results.

This paper presents a multibeam dielectric rod antenna for mm-wave wireless power transfer (WPT) applications. The proposed solution utilizes its unique multibeam setup which allows the generation of adjustable beams simultaneously, without the need for an additional beamforming network. To enhance the compactness of the system, each Rexolite rod is fed through an annular slot etched on a Rogers RO4003. The generated beams are steered toward the desired directions by adjustment in the configuration of these rods. The final configuration consists of five rods that were fabricated and measured. In this configuration, a beam coverage between $-30^{\circ}$ and 30∘ can be obtained, while in the frequency of interest, a gain value above $12\,\mathrm{dBi}$ is achieved. With its adjustable configuration, the proposed solution can be adapted to different operating scenarios. Moreover, the low cost and flexibility of the solution make it a promising candidate for Radio Frequency Wireless Power Transfer (RF-WPT) Internet of things applications.

The antenna characterization from planar near-field (NF) measurements is generally realized by using the classical NF to far-field transform technique of plane wave expansion (PWE). This approach imposes strong constraints on NF sampling. To overcome these limitations, an equivalent model of the antenna under test (AUT) is created based on a distribution of infinitesimal dipoles. A reduced-order model (ROM) of the problem is constructed to obtain a decomposition basis defining the radiated field. The powerful ability of the ROM in determining the number of points needed for accurate NF measurements is demonstrated. Also, efficient non-conventional sampling strategies are applied to the case of planar NF measurements and the influence of these distributions on the reduction of the number of samples is studied. The global analysis of our approach on simulated and measured NF data shows that only 20% of the total number of points are needed with respect to the classical PWE technique to achieve an accurate characterization.

We present continuous Class-F (CCF) and continuous Class-F−1 (CCF−1) power amplifiers (PAs) with compact circuit sizes. The output matching network (OMN) of a continuously harmonic-tuned PA must accommodate varying load impedance conditions across a wide frequency range, spanning from the fundamental frequency up to the 2nd and 3rd harmonic frequencies. This requirement typically leads to LPF-type OMNs with a significant circuit area overhead, thereby limiting the applicability of the broadband PAs. In this paper, we propose utilizing a one-port composite right-/left-handed transmission line to control the harmonic loads, while the fundamental loads are managed by a moderately sized LPF. This resulted in a notable reduction in PA size by nearly an order of magnitude. We demonstrate the effectiveness of this design approach through the fabrication of 2-GHz-band GaN HEMT PAs operating in CCF and CCF−1 modes. While both PAs exhibited high-efficiency (>70%) operational bandwidths at a state-of-the-art level, we also elucidate key design considerations specific to each PA operation mode.

This paper presents a comprehensive analysis of interference events in automotive scenarios based on radar systems equipped with communication-assisted chirp sequence (CaCS). First, it examines the impact of interference on radar and communication functionalities in CaCS systems according to the orientation of the investigated nodes. For this purpose, a graph-based approach is employed with MATLAB simulations to illustrate the potential occurrence of interference on the graph for communication functionality compared with their counterparts on radar. Second, the paper delves into the impact of interference on the synchronization between two communicating CaCS nodes. It extends a previous study to match the frequency of current radar sensors, where chirp estimation, an adjusted version of the Schmidl & Cox algorithm, and correlation are adopted to synchronize the transmitter and receiver of two CaCS communicating nodes in the time-frequency plane. The proposed synchronization method is finally verified by measurements at ${79}\,\mathrm{GHz}$ with a system-on-chip, where the resulting correlation metric and mean square error are illustrated as validation factors.

This invited, extended, paper compares and contrasts a number of different near-field (NF) to far-field (FF) transformation algorithms that can be used for the purpose of processing NF data acquired using multi-axis industrial robots. The merits and limitations of these various, commonly encountered algorithms are highlighted with comparison FF data presented across a frequency range spanning 3–15 GHz. Crucially, the paper explores the viability of using mixed mode acquisition geometries when performing antenna gain measurements where, prior to this work, several of the transforms yielded different transform gains, and electrical lengths. Here, we verify that at 8 GHz and above, where truncation effects were minimal, for a circa 30 dBi gain (at 8 GHz) test antenna the FF peaks were in agreement to better than ±0.02 dB, at 3σ irrespective of the acquisition geometry and transform algorithm used. In this invited, extended work, the existing simulation results are augmented with experimental results obtained from planar and spherical NF measurements of a pyramidal horn taken using a dual robotic antenna measurement system and a consistent distributed RF subsystem.

This work describes the design process of a single-pole double-throw (SPDT) microwave switch operating at Ka-band. It is tailored to a tunable reflective termination design that can be used in tunable power amplifier configurations. A high electron mobility transistor and a resonating network are employed in shunt configuration to enhance the performance in the output port’s active and inactive conditions. The small and large signal measurements showcase a 2 GHz bandwidth with an insertion loss and isolation better than −1.8 dB and −25 dB, respectively, and handling power levels of up to 3 W at 30.5 GHz. The load-pull measurements across the entire Smith chart offer comprehensive insights into the behavior of the SPDT when operating with complex and reactive loads, fulfilling the purpose of tunable reactive termination.

In this work, we develop a method for robust single-cycle measurement velocity vector estimation for automotive radar. Building upon our previous work, we introduce a methodology that leverages spatial diversity for accurate estimation of the velocity vector of targets in the medium to close ranges. We extend our initial conceptual framework, addressing limitations from our first approach and proposing necessary enhancements for real-world applicability. Our improved process excels in target separation, identification, and velocity vector estimation, proving effective across various scenarios and minimizing errors. The system, tested on pedestrians and metal targets, presents a promising avenue for exploring its performance with varying target sizes. Simultaneously, our in-depth study on Doppler-multiplex modulation reveals new relevant constraints, prompting a modulation change for improved response separation. Despite the necessity of increasing module numbers for enhanced performance, our structured approach to target itemization and classification positions our methodology as a valuable framework for future systems, offering a comprehensive solution to diverse challenges in target estimation and classification within the automotive landscape.

A broadband ±45° dual-polarized base-station antenna based on crossed-dipoles with parasitic elements has been presented in this study. This antenna consists of printed dipoles fed by integrated baluns, parasitic elements, and a ground plane below them. As a result of using parasitic elements on the dipoles and creating a suitable coupling between them, the antenna’s impedance bandwidth has been improved, and its dimensions have been reduced. The experimental results show that the proposed antenna can cover the frequency band of 1.58–2.73 GHz with |S11| < −15 dB and isolation better than 17 dB. The measured peak gain for the proposed antenna in the frequency band is reported as 7.8 dB. Also, the antenna’s half-power beamwidth equals 62.15° ± 1.45°. The proposed antenna is fabricated with overall dimensions of 0.67λ0 × 0.67λ0 × 0.17λ0 and has been measured in the antenna laboratory.

This research proposes a low-complexity, low-profile square-shaped quad-band dual-sense circularly polarized (CP) perturbed slot antenna with stepped microstrip feed for C-band radar and satellite applications. The proposed antenna is characterized by characteristic mode analysis. The proposed design has a square-shaped slot with diagonally opposite symmetric rectangular corner extensions. Multiband resonance is achieved by exciting the split ring resonator (SRR), cross strips and annular ring structure using the stepped microstrip line-fed slot radiator. The slot antenna and a metallic ring resonate at 1.64 and 8.2 GHz, respectively, showing left-hand circular polarization response, whereas the SRR and cross strips resonate at 3.6 and 6.6 GHz, respectively, exhibiting right-hand circular polarization radiation at these resonance bands. Hence, the proposed design shows quad-band performance with dual-sense CP behavior. Furthermore, the proposed antenna allows for independent tuning of polarization sense at resonance frequencies. The proposed design uses a low-cost FR-4 material as a substrate of dimensions 60 × 60 × 1.6 mm3. The experimentally measured results are in close agreement with the simulated performance parameters of the prototype.

Millimeter wave antenna arrays are essential components of modern communication and radar systems. To produce these devices in large quantities, manufacturers require fast and reliable measurement equipment. The measurement equipment needs to ensure the quality, interoperability, and adherence to regulatory norms of the produced devices. In this work, we present an active probe array structure (PAS), which enables fast, compact, and reliable over-the-air (OTA) measurements of radiation characteristics. No relative movement between the antenna under test (AUT) and the active PAS is required, making the system very suitable for cost-effective large-scale characterization and commercial production test scenarios. We demonstrate and discuss how a near-field (NF) OTA measurement performed by this active PAS system can be used to reconstruct the far-field (FF) antenna radiation behavior of AUTs using an NF to FF correlation approach.

In order to take on arbitrary geometries, shape-changing arrays must introduce gaps between their elements. To enhance performance, this unused area can be filled with meta-material inspired switched passive networks on flexible sheets in order to compensate for the effects of increased spacing. These flexible meta-gaps can easily fold and deploy when the array changes shape. This work investigates the promise of meta-gaps through the measurement of a 5-by-5 λ-spaced array with 40 meta-gap sheets and 960 switches. The optimization and measurement problems associated with such a high-dimensional phased array are discussed. Simulated and in-situ optimization experiments are conducted to examine the differential performance of metaheuristic algorithms and characterize the underlying optimization problem. Measurement results demonstrate that in our implementation meta-gaps increase the average main beam power within the field of view (FoV) by 0.46 dB, suppress the average side lobe level within the FoV by 2 dB, and enhance the field-of-view by 23.5∘ compared to a ground-plane backed array.

Two-dimensional (2D) leaky-wave antennas (LWAs) are commonly designed to radiate pencil beams at broadside and/or scanned conical beams. Recently, the possibility to radiate narrow null patterns at broadside has also been preliminarily explored. In this work, we first review the design rules to obtain a pencil beam from an infinite 2D LWA and then show how they change for having a beam with a narrow null at broadside. The effects of antenna truncation are also accounted for in both cases, and numerical results show how the optimum conditions are in turn affected. Finally, full-wave validations of practical structures excited with either horizontal or vertical dipoles validate the analysis.

This paper presents the bit efficiency of 28 GHz digital beamforming in over-the-air (OTA) measurements and simulations for distributed massive multiple-input–multiple-output (D-MIMO) and collocated massive multiple-input–multiple-output (C-MIMO) systems, as well as simulations for a 3.75 GHz small-cell scenario. Under the condition that users are randomly located in the line of sight coverage indoor area and spatially selected from each other by the normalized zero-forcing method, the OTA measured D-MIMO system exhibits an average of 4–7 dB better signal-to-noise ratio compared to C-MIMO when the number of simultaneously connected users “K” approaches the number of transceivers “M.” This means that the D-MIMO system provides higher bit efficiency than the C-MIMO system when K/M is large. Furthermore, the D-MIMO 3.75 GHz simulation predicts a relatively approximate 30% higher maximum efficiency than C-MIMO due to the shorter average distances between user equipment and access points in the D-MIMO system. To the best of the author’s knowledge, an earlier version of this paper has been presented at the 53rd European Microwave Conference as a first report on the 28 GHz OTA measured bit efficiency between C-MIMO and D-MIMO, highlighting D-MIMO’s advantage.