This communication introduces a graded index (GRIN) Fresnel zone planar lens (FZPL) antenna operating with high gain in the 500–750-GHz frequency range. The main innovation involves achieving a gain of 35.9 dBi by incorporating a GRIN dielectric perforated disk. This perforated disk acts as a distributed spatial delay for beam focusing, ensuring gain improvement and circular polarization simultaneously without needing an extra polarizer. The antenna exhibits high efficiency, with an average radiation efficiency of −1.05 dB, achieved through the optimization of a modified FZPL for silicon-on-insulator (SOI) micromachining technology. The antenna maintains a return loss below −15 dB across the entire 500–750-GHz band, achieving a 40% fractional bandwidth, with circular polarization maintained and an axial ratio consistently below 2.8 dB. The fabricated chip, sized 12.18×12.18 mm with a thickness of 526 μ m, enhances practicality. The feeding arrangement involves a standard open waveguide, and direct mounting into a standard WM-380 waveguide flange is facilitated. This communication discusses the prototype’s design, fabrication, and measurement, emphasizing the excellent agreement between the antenna’s performance and simulated data.

This paper presents the first demonstration of a high-gain planar THz lens antenna with beam-steering capability by frequency-orthogonal spatial spreading, operating in the 610–685 GHz range. The antenna is based on integrating a Fresnel zone planar lens with a graded-index silicon interposer. The concept enables passive beamforming of four simultaneous beams from a single feeding port, covering a field of view from -30° to -14° for 20 GHz bandwidth with a 4° separation of the beam direction. The beams can be swept continuously over that field of view by mapping the signal to different frequencies. Furthermore, when using four feeds, 16 simultaneous beams can be created, of which two frequency-orthogonal beams are separated by 40 GHz in frequency can be mapped into the same spatial direction. Thus, it is demonstrated that high-gain multibeam beam steering can be achieved without the hardware complexity of conventional phased-array antenna systems requiring a large number of RF chains. An antenna prototype is implemented using silicon micromachining, resulting in a compact 15.8 mm × 15.8 mm device with a thickness of 526μm, which is directly mounted on a standard WM-380 waveguide feed. Measurement results include a realized gain of 32.1 dBi, only a 0.8 dB beam steering loss across the field of view, an effective side-lobe suppression better than -22 dB, and a high radiation efficiency of -1.25 dB. The measurements are in excellent agreement with simulations, and the worst-case deviation of the measured beam direction from the simulated one is only 0.1° out of 16 beams.

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.

A new transition from coplanar waveguide probe to micromachined rectangular waveguide for on-wafer device characterization is presented in this article. The transition is fabricated in the same double H-plane split silicon micromachined waveguide technology as the devices under test, requiring no additional post-processing or assembly steps. We outline the design and fabrication process of the transition for the frequency band of 220–330 GHz. A coplanar waveguide structure acts as the probing interface, with an E-field probe protruding in the waveguide cavity exciting the fundamental waveguide mode. Guard structures around the E-field probe increase the aspect ratio during deep reactive ion etching and secure its geometry. A full equivalent circuit model is provided by analyzing its working principle. RF characterization of fabricated devices is performed for both single-ended and back-to-back configurations. Measured S-parameters of the single-ended transition are obtained by applying a two-tiered calibration and are analyzed using the equivalent circuit model. The insertion loss of the single-ended transition lies between 0.3 dB and 1.5 dB over the whole band, with the return loss in excess of 8 dB. In addition to previously reported characterization of a range of devices under test the viability of the transition for on-wafer device calibration is demonstrated by characterizing a straight waveguide line, achieving an insertion loss per unit length of 0.02–0.08 dB/mm in the frequency band of 220–330 GHz.

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 research investigates a unique radar concept based on a frequency-sweeping stepped-frequency continuous-wave (SFCW) radar with a two-element antenna array. The suggested array can switch between a notched and a broad beam shape. Regarding target discrimination and locating accuracy, we compare this radar system to three-element and four-element frequency-sweeping SFCW radars. Compressed sensing methods are used to reconstruct images and evaluate the performance of various antenna arrays. The range resolution for the proposed two-element beam shape switching antenna system with a bandwidth of 10 GHz is noteworthy-10 mm for point targets and 20 mm for extended targets. This range resolution is two times that of the larger aperture three-element array and four times that of the four-element array. Notably, the range resolution beats the theoretical range resolution due to the use of compressed sensing to combine information from the two beam shapes. Furthermore, the suggested system outperforms previous antenna arrays regarding angular resolution, especially when targets are close in range and angle. With a 10 mm range distance and a 2(degrees )angle difference, the system effectively discriminates three targets. In a triple-target scenario, the suggested two-element beam shape switching system outperforms a standard four-element phased array radar with the same bandwidth even with restricted computational resources.

This study investigates the influence of laser parameters on electromagnetic wave attenuation within a silicon waveguide over a wide frequency range of 67–220 GHz using 3-D full-wave simulations. A 10-layer cylindrical model mimicking the energy distribution of a Gaussian laser beam shape is utilized for the analysis. The conductivity of each layer is calculated, and the S-parameters are simulated via CST Studio Suite. Significantly different attenuation levels are observed for different laser wavelengths used in this study. A 980 nm laser resulted in a substantially higher attenuation comparison to a 405 nm laser which had a minimal impact. Furthermore, by increasing the laser intensity, an increase in attenuation is observed. Moreover, the low level of simulated return loss indicates that solid-state plasma absorption dominates the reflections.

This article experimentally demonstrates a frequency-sweeping notch-beam sub-THz radar frontend based on a two-line array antenna featuring computational imaging. Operating within 237.5 GHz and 250 GHz with 12.5 GHz bandwidth, the radar utilizes a 12 λc delay line to achieve frequency-sweeping capabilities. This configuration allows dynamic notch-beam scanning across angular ranges from − 26.5 ∘ to 28 ∘ . The radar frontend is highly compact with a total size of 20 mm× 14.3 mm× 1.2 mm, including the beam-steering network, a magic-tee for creating the 180 ∘ phase shift required for creating the notch-beam, and the antenna array, and is implemented by silicon micromachining. The radar was evaluated with single and dual-target scenarios utilizing and benchmarking different computational imaging algorithms, i.e., matched filter (MF), fast iterative shrinkage-thresholding algorithm (FISTA), and multiple signal classification (MUSIC). It was found that the MUSIC algorithm outperforms MF and FISTA in range and angular resolution in single-target scenes, achieving a range resolution of 7.8 mm and an angular resolution of 15.7 ∘ , with detection errors of less than 6.6 mm and 3.5 ∘ , respectively. Although the MUSIC algorithm maintains reliable range resolution in dual-target scenarios, it performs poorly in providing angular information.

This article experimentally demonstrates a frequency-sweeping notch-beam sub-THz radar frontend based on a two-line array antenna featuring computational imaging. Operating within 237.5 GHz and 250 GHz with 12.5 GHz bandwidth, the radar utilizes a 12 λc delay line to achieve frequency-sweeping capabilities. This configuration allows dynamic notch-beam scanning across angular ranges from − 26.5 ∘ to 28 ∘ . The radar frontend is highly compact with a total size of 20 mm× 14.3 mm× 1.2 mm, including the beam-steering network, a magic-tee for creating the 180 ∘ phase shift required for creating the notch-beam, and the antenna array, and is implemented by silicon micromachining. The radar was evaluated with single and dual-target scenarios utilizing and benchmarking different computational imaging algorithms, i.e., matched filter (MF), fast iterative shrinkage-thresholding algorithm (FISTA), and multiple signal classification (MUSIC). It was found that the MUSIC algorithm outperforms MF and FISTA in range and angular resolution in single-target scenes, achieving a range resolution of 7.8 mm and an angular resolution of 15.7 ∘ , with detection errors of less than 6.6 mm and 3.5 ∘ , respectively. Although the MUSIC algorithm maintains reliable range resolution in dual-target scenarios, it performs poorly in providing angular information.

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.