This paper deals with the multiple targets localization problem via multi-channel ultra-wideband (UWB) imaging radar non-line-of-sight (NLOS) signal processing. A novel matching-based radar imaging algorithm is proposed to obtain the positions of multiple targets in the L-shaped corner scenario with complex multipath ghost signals. Firstly, a multipath propagation model for the multiple targets scenario is established. Then the positions of the actual multipath ghosts are extracted from the radar image, and the candidate targets corresponding to these multipath ghosts are derived. Secondly, the ellipse-cross-localization method is proposed to obtain the positions of the candidate multipath ghosts, followed by two defined matching factors to measure the similarity between actual and candidate multipath ghosts. According to the similarity, decision rules are designed to determine the actual targets. Compared with the localization algorithm based on one-dimensional range profile, the proposed algorithm can effectively cope with the cases of multiple targets, even in the cases of rough walls and noise. Finally, simulations and experimental data are used to validate the effectiveness of the proposed algorithm.

A method based on reweighted l ₁ norm regularization for synthesizing a near-field (NF) sparse array with accurate control of 3 dB beamwidth(BW), focal distance, and peaksidelobelevel (PSL) is proposed in this communication. We first formulate the problem of synthesizing NF sparse array as a reweighted l ₁ norm optimization problem. The constraints for NF focusing array are proposed to accurately control the 3 dB BW, focal distance, and PSL at the same time. An effective definition of the solution space for the NF synthesis problem is proposed to have the NF pattern well constrained and ensure the practicability and convergence of the proposed method. Finally, simulation examples are presented and compared with full-wave simulation results to validate the effectiveness and advantages of the proposed method.

The low-orbit satellite has a large communication angle, resulting in a large difference in path loss at different angles. The existing multibeam coverage area division method cannot meet the coverage requirement of the effective isotropic radiated power (EIRP) in these large-angle areas. Therefore, this letter proposes a method for dividing the beam coverage area from the outside to the inside. Combined with the subarray multibeam forming method, it achieves the optimal coverage of isoflux multiple beams to the ground with unchanged output power of the transmitter, which greatly improves the overall efficiency of existing beamforming methods. At the meantime, a frequency reuse color separation algorithm based on the depth first search is proposed to reduce the mutual interference among nonuniform multiple beams. As an example, 52 beams with 12-color frequency reuse are designed to cover ±55°. The edge EIRP of a single beam is no less than 25.5 dBW and the carrier-to-interference ratio is no less than 16 dB.

The transverse linearly polarized beam can maintain its polarization when reflected, which is important for a detection system. Most of the existing planar Bessel beam generators are implemented in a central feeding radial topology and hard to generate the Bessel beam with the transverse linear polarization. In this communication, a substrate integrated waveguide (SIW) slot array antenna is proposed to generate the transverse linearly polarized Bessel beam. The desired phase and amplitude distribution of the Bessel beam can be easily realized by such an array. With the inherent 0°/180° output phase of the comb-like divider considered, the desired 0°/180° phase distribution is implemented by placing adjacent slots on the opposite (0°) or the same side (180°) within a linear array and by employing adjacent linear arrays with the inverse (180°) or the same (0°) slot offset direction accordingly. The offset of the slot, as well as the tuning metalized vias within the comb-like divider, is modulated to generate the desired amplitude distribution. After reducing the influence of the rectangularly truncated aperture by adding a Gauss-tapered amplitude distribution, a transverse linearly polarized Bessel beam SIW slot array antenna is designed with more than 100 mm depth-of-field (DoF) and less than −25 dB cross polarization. To the best of our knowledge, it is the first design to generate the transverse linearly polarized Bessel beam by a planar array antenna.

A THz 2-D frequency scanning planar integrated array antenna is developed in this letter. Eight THz leaky-wave antennas are combined with a true-time-delay (TTD) phase-shifting feeding network to steer the beam in two directions by sweeping the frequency. Several H-plane 90° bends with linearly increased length are adopted to achieve the scalable TTD phase shift. The feeding lines are closely spaced to reduce the phase-shifting network occupied area in this progressive phase-shifting scheme. Besides, the E-plane 180° bend is used to construct the double-layer phase-shifting network, maintain the number of multiple scanning sweeps and improve the aperture efficiency. Moreover, in the used microelectromechanical systems (MEMS) fabrication technique, the minimum height of the radiation slot is 0.2 mm, which is too thick and deteriorates the radiating performance. When the double-layer step-profiled radiating slot is used instead of the thick slot, a THz leaky-wave antenna with higher radiation efficiency and better gain flatness can be achieved. Finally, a prototype antenna is fabricated and experimentally validated. The operating frequency range is 325-400 GHz and the beam scanning range is 22.7° × 60° with a maximum radiation gain of 25.28 dBi.

The maximum radiation efficiency can be obtained when the feed array excitation of a reflector antenna is synthesized by the conjugate field matching (CFM) method. However, the CFM method can only get the strongly tapered feeding power distribution. This will lead to most of power amplifiers (PAs) working in low efficiency states and reduce the equivalent isotropic radiated power (EIRP) with the limited power consumption. In this work, combining the radiation efficiency and the PA efficiency, the radiated power efficiency (RPE) is defined as the new design goal and is to be raised to achieve higher EIRP. For this reason, a method based on the near-field pattern synthesis is proposed. In this method, all the ON-state PAs are required to work in the highest efficiency state. Then, with well-trained support vector machine (SVM), the ON–OFF states of the PAs are adjusted so that the reflected focal field can be better synthesized by the near-field pattern of the feed array. Thus, the loss of the radiation efficiency is minimized. As a result, the RPE is about 22% higher than that of the CFM method and about 10% higher than that of the optimum CFM truncation case.