This article presents a novel design of a full-band E -plane waveguide bend for direct flange-to-chip connection. The proposed E -plane bend concept is validated with a reduced-height bend prototype designed for standard WR-3.4 waveguide flange-to-chip connection, fabricated by silicon micromachining, and characterized by de-embedding the S -parameters with a custom-made offset-short calibration kit. The measured insertion and return losses are 0.08–0.3 dB and better than 14.7 dB, respectively, for the whole waveguide band of 220–320 GHz, and better than 0.15 and 20 dB, respectively, for more than 80% of the waveguide band. The measured results are in excellent agreement with the simulation data. Besides, a two-port waveguide structure with WR-3.4 interfaces is fabricated and measured to confirm the functionality of the designed E -plane bend. Furthermore, sensitivity analysis shows the robustness of the proposed geometry against fabrication tolerances.

This paper presents the design, fabrication, andcharacterization of a complex 8-layer magic-tee operating in the220-280 GHz frequency band and optimized to be fabricated bysilicon micromachining in four layers of silicon-on-insulatorchips. The designed magic-tee prototype can be used as aseparate block with axially aligned standard WR-3.4 rectangularwaveguide interfaces with a total footprint of4.5mm×4mm×1.2mm or be integrated into the signal chain with atotal footprint of only 3mm×2mm×1.2mm. The measuredinsertion losses of the sigma and delta ports, including all thewaveguide routings connecting the magic-tee ports to the deviceinterfaces, are between 4.3-5.1 dB and 4.5-5.3 dB, respectively, inthe 220-278 GHz frequency band. Besides, the measured sigmato-delta port isolation is better than 24 dB at the same frequencyspan. In this work, as the fabrication tolerances are predicted bytest fabrication runs and compensated in the design process, themeasured results and the simulated data are in excellentagreement. All these features make the presented magic-tee wellsuitedfor mono-pulse applications to split/combine signals forbeamforming and signal routing.

This article presents an unbalanced-fed silicon micromachined dual-port dual-line antenna array. The radiation pattern of the antenna array can be steered in the E -plane by sweeping the frequency and can be switched between a broad and a notched beam by exciting the ports with in-phase or out-of-phase signals. The antenna is designed for and implemented by silicon micromachining. Each single-line subarray consists of #8 antenna apertures in which the field amplitude is tapered in the H-plane, and the phase imbalance of unbalanced power dividers is minimized by integrated delay sections in the feed network. The measured return loss of the antenna is better than 10 dB from 220 to 295 GHz for both input ports (29.1% fractional bandwidth). The antenna prototype is designed for 40° of beam steering in the E -plane (scanning speed of 4°/GHz) by sweeping the frequency from 238 to 248 GHz. The measured sidelobe level of the broad beam in the H-plane is better than 18.5 dB, and the measured depth of the notched beam is better than 22.5 dB in the entire scanning range. In addition to the dual-port dual-line antenna array, a single-line 1 × 8 antenna array is also implemented for reference measurement purposes. The measured return loss of the single-line antenna array is better than 10 dB from 220 to 314 GHz (35.2% fractional bandwidth), and its measured sidelobe level is between 18 and 21.3 dB in the H-plane from 220 to 280 GHz. Besides, the simulation data and the measurement results are in excellent agreement.

This article presents a highly integrated novel silicon micromachined single-pole-single-throw waveguide switch based on two microelectromechanically reconfigurable switching surfaces (MEMS-RSs), which allows optimizing the switching performance by tuning the interference between the two such MEMS-RSs utilizing integrated electrostatic comb-drive actuators. The switch prototype is implemented with axially aligned standard WR-3.4 waveguide ports with a total footprint of 3 mm×3.5 mm×1.2 mm. The measured blocking ( off ) state insertion loss (isolation) and return loss, measured between two standard WR-3.4 waveguide flanges, are 28.5–32.5 dB and better than 0.7 dB, and the propagating ( on ) state insertion and return losses are 0.7–1.2 dB and better than 17 dB in the 220–290 GHz frequency band, respectively. The measured results were in excellent agreement with the simulation data, implying 27.5% fractional bandwidth, which is very close to a full waveguide band performance. For further investigations, two variants of the switching circuit with only a single MEMS-RS and without any MEMS-RSs have also been fabricated. The single MEMS-RS switch achieved the off -state isolation, on -state insertion loss, and return loss of only 11.5–12.5 dB, 0.8–1.3 dB, and better than 12 dB from 220 to 274 GHz, respectively, which clearly indicates the drastic performance improvement of the interference-based double MEMS-RS switch design. Moreover, measurement of the waveguide-only reference structure showed that the waveguide section alone attributed to 0.2–0.5 dB of the measured on -state insertion loss of the double MEMS-RS switch, and the rest is due to the introduction of the MEMS-RSs inside the waveguides.

This article presents a novel subterahertz (sub-THz) crossover waveguide switch concept operating in the 220–260-GHz frequency band. The crossover switching circuit is implemented by two hybrid couplers and two single-pole-single-throw (SPST) switching mechanisms, utilizing microelectromechanically reconfigurable switching surfaces. The silicon-micromachined crossover switch prototype is very compact, with a total footprint of 5.6 × 5 × 1.2 mm, including four standard WR-3.4 waveguide ports and the waveguide routing to these ports. The measured insertion loss (IL) is 0.9–1.4 dB in the crossover state and 0.8–1.3 dB in the straight state from 220 to 260 GHz, and the isolation (ISO) is better than 29.3 and 29 dB, respectively, for these states. The measured return loss (RL) is better than 14 dB in the crossover state and better than 13.6 dB in the straight state. Besides, the measured input-to-input ISO is better than 13.7 and 34 dB in the crossover and straight states, respectively. The measurement results are in excellent agreement with the simulation data. Moreover, the signal paths are fully symmetric for all input-to-output signal paths, making the crossover switching circuit suitable for redundancy applications.

This paper presents the design, fabrication, and characterization of a compact silicon-micromachined beam steering frontend circuit featuring beam shape switching and frequency beam steering. The designed beam steering frontend includes a switching circuit consisting of a crossover switch and a magic-tee for beam shape switching, as well as a delay line network connected to a corporate-fed dual-line antenna array for frequency beam steering. All components are co-designed and integrated to minimize the insertion loss. The signal chain is implemented on four layers of silicon-on-insulator chips with a total footprint of 20mm×1.4mm×1.2mm. The designed frontend operates properly in the 220-260 GHz frequency band with a measured return loss of better than 15 dB and a beam steering range of 238-248 GHz with a measured return loss of better than 20 dB. The frontend has two standard WR-3.4 waveguide input ports, and each port can create two different radiation patterns, a broad and a notched beam, in which both can be steered from 238 to 248 GHz in the E-plane of the antenna array. The sidelobe level of the broad beam is reduced by amplitude tapering and remains better than 18 dB in the H-plane of the antenna array across the scanning range. Moreover, the depth of the notched beam remains better than 17 dB in the entire scanning range, making the presented beam steering frontend well-suited for tracking, surveillance, imaging, and radar applications.

This paper presents the integration of advancedsignal processing algorithms with a frequency-sweeping minimalisticradar frontend system, focusing on enhanced targetdetection and localization capabilities for single and multipletarget scenarios. The minimalistic radar frontend is able toswitch between two distinct frequency steerable radiation patterns,namely, notch and broad. The performance of four keyalgorithms, Matched Filtering (MF), Fast Iterative Shrinkage-Thresholding Algorithm (FISTA), Multiple Signal Classification(MUSIC), and a newly proposed adaptive Inverse Fast FourierTransform (IFFT) technique, are investigated and evaluatedthrough a series of experiments conducted in an anechoic antennachamber. The advantages and limitations of these algorithms areinvestigated comprehensively in the context of the minimalisticradar frontend, which is designed for short-range applications.The analyzed results revealed that while computation algorithmslike MF and FISTA provide similar range resolutions, MUSIC,and adaptive IFFT outperform them in certain areas. MUSICand adaptive IFFT offer 5.8 mm and 17.8 mm range resolutionand 13◦ and 14.4◦ angular resolution accuracy, respectively. Theexperiments underscore the significance of algorithm selectionbased on the radar system’s operational requirements and thecomplexity of the imaging scenario.