A novel W-band two-dimensional (2-D) monopulse sparse array antenna with suppressed sidelobe levels is proposed in this paper. The 2-D monopulse antenna is composed of a radiation sparse array, an irregular interconnected waveguide-based network, a power divider network, and a sum-difference network. The sparse array uses a box-horn as the radiation element and is optimized based on the genetic algorithm, which exhibits low sparsity and low sidelobe levels. The whole aperture of the antenna is divided into four subarrays. To feed all the radiating elements that are randomly distributed in the subarrays with the same amplitude and equal phase, an irregular interconnected waveguide-based network and a power divider network are designed. Finally, a sum-difference network is connected to the end of the four subarrays to obtain the sum and difference radiation performance results for the monopulse antenna. A 2-D monopulse sparse array antenna with 32 radiating elements is fabricated and measured. The measured |S11|≤-10 dB bandwidth of the antenna is over 6 GHz (from 90 GHz to 96 GHz). At the center frequency, the maximal gain of the sum radiation pattern is approximately 24.0 dBi, with low sidelobe levels (both E-plane and H-plane) less than -19.0 dB. Additionally, the null depth of the difference radiation pattern is less than -30.0 dB.

This paper describes the design and realization of a novel Ka/W dual-band shared-aperture horn antenna employing the concept of mutual enhancement. The W-band antenna cells within the Ka-band antenna structure enhance the aperture utilization efficiency. The proposed design enables gain enhancement in the Ka-band horn antenna through incorporation of W-band horn antenna cells, while the W-band array antenna achieves low sidelobe levels by adopting a sparse array configuration. The W-band antenna consists of a radiation sparse array, an irregular interconnected waveguide-based network, and a power divider network. A mutually enhanced Ka/W dual-band shared-aperture horn antenna is fabricated and evaluated. The results reveal a gain improvement of 1.5 dB at 35 GHz compared to the original horn antenna. Moreover, the measured |S11|≤-10 dB bandwidth of the W-band array antenna spans over 16 GHz (ranging from 92 GHz to 108 GHz). At the central frequency, the maximal gain of the radiation pattern is approximately 20.8 dBi, with low sidelobe levels (in both the E-plane and the H-plane) of less than -19.0 dB.

In this letter, a novel wideband comparator for W-band circularly polarized (CP) monopulse antenna is proposed and analyzed. The comparator mainly consists of four 3 dB waveguide couplers and a novel wideband phase shifter (PS). The bandwidth of the comparator is greatly enhanced by combining the sequential rotation feeding technique with the wideband PS technique for the first time. To verify its wideband performance, the CP monopulse antenna consisting of the comparator and a 2×2 CP horn array is fabricated and measured. The experimental results are in good agreement with the simulation. For the measured sum (Σ) channel, the reflection coefficient lower than -10 dB, the realized gain not less than 11.5 dBi, and the axial ratio (AR) better than 0.45 dB are realized in the whole W-band (75-110 GHz). For the measured azimuth (AZ) and elevation (EL) difference (Δ) channels, the null depths of the difference patterns are less than -25.8 dB at 80, 92.5, and 105 GHz, and the difference patterns are symmetrical and stable.

A 16 × 16 substrate integrated cavity (SIC) backed slot antenna array in Y-band (170-260 GHz) with high gain, wide bandwidth, simple feeding network, and easy fabrication is presented in this letter. The antenna array consists of 64 2 × 2 SIC-backed slot antenna subarrays and a 64-way metal feeding network. The SIC-backed slot antenna subarray is designed based on high-order modes TM ₁₄₀ , TM ₃₃₀ , and TM ₃₄₀ to realize high gain and wide bandwidth. The metal feeding network is composed of 16 X-shaped cavities and a 16-way full-corporate-feed waveguide network. The X-shaped cavity is introduced to reduce the complexity of the feeding network. The SIC-backed slot antenna is fabricated by high-precision printed circuit board (PCB) for simple radiating unit structure and easy production. The metal feeding network is manufactured by high-precision computer numerical control (CNC) milling process for low loss. Measured results indicate that the |S ₁₁ | of the proposed antenna array performs well within 210-230 GHz. The antenna array achieves the measured gains larger than 25.0 dBi within the working bandwidth and the peak gain is 28.7 dBi at 221 GHz.

In this study, we propose a novel pixel-level non-local similarity (PNS)-based reconstruction method for millimeter-wave interferometric synthetic aperture radiometer (InSAR) imaging. Unlike traditional compressed sensing (CS) methods, which rely on predefined sparse transforms and often introduce artifacts, our approach leverages structural redundancies in InSAR images through an enhanced sparse representation model with dynamically filtered coefficients. This design simultaneously preserves fine details and suppresses noise interference. Furthermore, an iterative refinement mechanism incorporates raw sampled data fidelity constraints, enhancing reconstruction accuracy. Simulation and physical experiments demonstrate that the proposed InSAR-PNS method significantly outperforms conventional techniques: it achieves a 1.93 dB average peak signal-to-noise ratio (PSNR) improvement over CS-based reconstruction while operating at reduced sampling ratios compared to Nyquist-rate fast fourier transform (FFT) methods. The framework provides a practical and efficient solution for high-fidelity millimeter-wave InSAR imaging under sub-Nyquist sampling conditions.

A truly integrated absorber/reflector/radiator (ARR) utilizing a switchable electric/magnetic conductor (SEMC) antenna is presented in this paper. Two independent direct current (DC) bias circuits are utilized to alternate the function of top layer and bottom SEMC antenna. The operation principle of ARR is analyzed, and its design strategies are outlined. The switchable absorber/reflector is firstly constructed by activating or deactivating the p-i-n diodes within dual square-loops resonator of top layer. Moreover, its physical mechanism is examined using the corresponding equivalent circuit model. Then, the SEMC dipole array antenna, exhibiting perfect electric conductor (PEC)-like reflection in ON state and operating as a low-profile antenna backed by an artificial magnetic conductor (AMC) in OFF state, is employed to replace the grounded metal plate of absorber/reflector for establishing the ARR. Radiation and scattering performances are investigated respectively, revealing that the integrated ARR exhibits multifunction encompassing wideband absorption, frequency selective reflection, and high gain radiation. Finally, a sample of the proposed ARR is fabricated and experimentally tested, demonstrating a good agreement between observed and simulated results.