An arc-shaped distributed multilayer capacitive loading structure combined with resistive loading is presented in this paper to enhance the radiation performance of folded bowtie antenna (FBA). The radiation efficiency of the loaded bowtie antenna (BA) is improved, and the low-frequency bandwidth is broadened by the bent loop circuits. Additionally, a novel technique of cavity groove is proposed to design the reflector. The optimized cavity tightly coupling with the radiation part overcomes the shortcomings of conventional cavity-backed BAs. The improved ultra-wideband (UWB) FBA with low profile is then designed and fabricated. The basic geometry of the proposed antenna is combined by a novel acorn-shaped bent bowtie patch and a hollowed stepped back cavity. The simulated -10 dB impedance bandwidth of the proposed antenna is over 100 MHz-1100 MHz while the measured operating bandwidth is 250 MHz-850 MHz. This BA of folded type obtains a high realized gain of 4 dBi at 850 MHz and a narrow pattern over the whole band. Time-domain measurements and field tests for practical ground-penetrating radar (GPR) applications have been carried out and the results demonstrate the advanced performance.

This paper demonstrates an integrated wide-angle scanning planar phased array based on pattern reconfigurable antennas. The pattern reconfigurable antenna unit consists of four rotationally symmetrical elements with a dimension less than 0.41λ×0.41λ. By exciting different elements, the beam of the unit switches between four modes and has a 3dB coverage of ±77°, which helps the antenna array achieve an expanded scanning range. The reconfigurable principle and bandwidth enhancement method of the compact antenna unit are analyzed; the radiation efficiency and the performances of the array are also discussed. The whole system of the phased array is integrated on a multilayer hybrid PCB board, which includes a 4×4 reconfigurable antenna array, TR modules, 4-channel RF chips, a beam control circuit, and a power management circuit. The measured return loss of the antenna unit is less than -10dB in the frequency range of 27GHz to 30GHz, and the scanning range is from -68° to 68° with a maximum gain of 16.4dBi. The gain fluctuation of the array in beam scanning is less than 2dB, and the scanning range of -3dB covers ±80°.

The miniaturized high-gain antenna is required in portable, ultra-wideband radar systems. However, the miniaturization, ultra-wideband and high gain often restrict each other in the antenna design. In this paper, a dual-polarized, double-slot, antipodal tapered slot antenna with a double-layer, dual-loop structure and novel slot edges is presented. The proposed magnetic dual-loop structure has the capacity to reduce the low cut-off frequency of the double-slot tapered slot antenna by weakening the resonance and coupling. In addition, the high gain, low sidelobe level (SLL), and low cross-polarization level are achieved in the boresight direction. A novel gradient slot profile is designed to improve the low-frequency directivity of the tapered slot antenna without affecting the matching. To feed the antenna elements, a kind of wideband, balun-divider structure is designed. The dual-polarized antenna is combined by two orthogonal elements in a cross configuration without galvanic contact or influence to performance. The measured results show that the impedance bandwidth of the proposed antenna is 0.6~4 GHz, and the maximum gain is 11 dBi. The isolation between the two antenna ports is better than 32 dB, and the cross-polarization discrimination (XPD) is better than 20 dB.

This paper presents a novel compact RF MEMS series capacitive switch designed to address the common issues of severe warpage and excessive size in cantilever switches. Using SolidWorks, COMSOL Multiphysics, and HFSS as simulation tools, this paper designs an integrated structure combining the upper electrode with the signal bridge, along with a composite beam featuring an arc-shaped SiO flanged clamped beam and Au cantilever. The switch has overall dimensions of 229 µm in length and 106 µm in width. Fabrication results demonstrate low switch warpage while achieving series capacitive configuration and compact dimensions. Simulations reveal that the annular defect structure on the upper electrode reduces actuation voltage, with switch isolation exceeding 21.5 dB and insertion loss below 0.65 dB in the 25 GHz band. Both simulation and experiments indicate that biaxial residual stress exerts the most significant influence on composite structure actuation voltage compared to structural stress. The simulated actuation voltage without residual stress measures 28.8 V, whereas that of the fabricated prototype is approximately 100 V. This switch is suitable for terahertz intelligent metasurfaces and applications requiring minimized switch deformation.

The vital signal extraction remains an on‐going challenge due to the low signal‐to‐noise ratio (SNR) of vital signals in real tests. In this Letter, the authors propose a novel vital signal enhancement method using spectral gain instead of the traditional singular value decomposition (SVD) method, which shows excellent performance in the elimination of noise that is in the same frequency band as the vital signal and reducing calculation time. The simulation and experiment have been conducted, and the results indicate that the proposed extraction method outperforms the traditional SVD in output SNR and processing time.