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Video Synthetic Aperture Radar (SAR) provides dynamic information about an observation scene in a video to the human eye, which can be very useful for the real-time detection of the ground maneuvering targets. The focusing of video SAR data is demanding because of its high data rate. In this study, we discuss suitable focusing algorithms and presents the obtained simulation results. Further, the shadow formation mechanism is analyzed with respect to target detection. Finally, the machine learning algorithm used for detecting the shadows of the moving targets is compared with the classical image processing methods that use real datasets.

Numerous studies have been made to design broadband frequency selective rasorber (FSR). However, it is still a challenge to realize optically transparent FSR, due to the difficulty in realizing high transparency, high-quality factor(Q) parallel resonance, and low-Q series resonance simultaneously. Here, we propose a new method to design transparent FSR for the first time. To break through the technical barrier, a thin copper wire with a different configuration method is utilized to design lossy layer, which can realize high transparency, in-band transmission, and out-of-band absorption concurrently. The proposed FSR is configured by cascading a transparent lossy layer above a transparent frequency selective layer with an air space to separate them. We adopt the equivalent circuit model, electric field distribution, and loss distribution to reveal the physical mechanism of the FSR. The simulation results show that the transmission loss is 1 dB at 8.3 GHz, and the reflection amplitude is less than −10 dB in 2.7–8.9 GHz. The FSR can achieve 96.3% optical transparency theoretically. A prototype is fabricated and measured to validate the proposed design. The measured results achieve good agreement with the simulated results. The proposed FSR can act as a stealth radome for transparent components of ships and aircrafts. The application scenarios can be extended to communication and imaging systems. [ABSTRACT FROM AUTHOR]

This article presents a high-gain slotted ridge waveguide antenna array (SRWAA) with inductive diaphragms, which can realize a wide-sector beam with a low sidelobe simultaneously. The proposed antenna can cover a wide detection range and avoid interference from other directions. The expected excitation distribution for the antenna array is extracted through a beamforming method. To reduce the influence of the dispersion phenomenon on signal quality, inductive diaphragms are inserted into the sidewall of the ridge waveguide, which is fully analyzed from the point of the equivalent circuit. A cut-off-mode power divider is utilized, which can control the power ratio flexibly. An SRWAA working at 24.125 GHz, including a six-way feeding network, and a $6\times24$ slot array with the size of 330 mm $\times66.8$ mm is designed and fabricated. The measured sidelobe level (SLL) and half-power beamwidth (HPBW) in the elevation plane are −19.6 dB and 54.41°, with the counterparts in the azimuth plane −29.8 dB and 3.15°, respectively. The measured peak gain is 22.3 dBi at 24.125 GHz. The measured results are in good agreement with the simulated ones. This work has the potential to be applied in air detection, anti-unmanned aerial vehicles (UAVs), meteorological radar, and imaging radar. [ABSTRACT FROM AUTHOR]

In recent years, bistatic synthetic aperture radar (BiSAR) has attracted the attention of many radar researchers. It is well known that the slant range history of BiSAR is the sum of two square-rooted terms, which correspond to the transmitting and receiving slant ranges, respectively. For a point target in the SAR scene, it is quite difficult, if not impossible, to obtain an analytic formula to describe the target echo data in the 2-D frequency domain without any approximation by using the conventional stationary phase method, which makes it very difficult to develop fast-focusing algorithms for BiSAR. In this paper, based on the concept of an instantaneous Doppler wavenumber and by defining a new variable called half quasi-bistatic angle, an analytic formula of the point target response in the spectral domain is developed for BiSAR with parallel trajectory (referred to as parallel BiSAR for simplicity). Relying on a first-order Taylor expansion of the above formula with respect to the parameter called the sum of closest distances on the swath center, a bistatic range migration algorithm is proposed for any azimuth-shift-invariant BiSAR data processing. Simulation results have confirmed the effectiveness of the proposed novel approach. Index Terms--Bistatic range migration algorithm (BiRMA), bistatic synthetic aperture radar (BiSAR), instantaneous Doppler wavenumber (IDW), synthetic aperture radar (SAR).