Abstract
The all solid-state terahertz (THz) radar has obvious miniaturized integration and high resolution imaging advantages compared with conventional microwave radar. In this paper, a 0.22 THz active frequency-modulated pulse radar system with one transmission channel and four receiving channels is presented, and interferometric inverse synthetic aperture radar (InISAR) imaging experiments, which can acquire altitude information of objects, are carried out. In order to acquire high-quality InISAR images, a calibration method is presented to solve the nonlinearity of wideband signal frequency and phase inconsistency of different receiving channels together. Furthermore, to deal with the phase wrapping in InISAR imaging of objects with large scale, a novel method based on the dominant scatterers to estimate the objects rotation rate is presented. Finally, to show more information of objects in the InISAR images, the imaging results with a large rotation angle by the convolutional back-projection algorithm are obtained. The imaging results verify the superior performance of the multi-channel THz radar system and the imaging processing method, which can provide support for further research on InISAR imaging in the THz band.
Highlights
Terahertz (THz) waves lie between microwaves and infrared waves in the electromagnetic spectrum, and they have many special characteristics
We present a 0.22 THz all-electronic one-input four-output imaging radar system
The stationary phases of radar echoes received by different receiving channels are inconsistent because they transmit through different antennas and electrical connecters, and the phase modulation characteristics of these devices are different. It will destroy the real phase relation of the inverse synthetic aperture radar (ISAR) images of different receiving channels, and make the interferometric inverse synthetic aperture radar (InISAR) imaging results no longer match the real position of target
Summary
Terahertz (THz) waves lie between microwaves and infrared waves in the electromagnetic spectrum, and they have many special characteristics. The program aims to achieve moving targets tracking and imaging with video frame rate They have carried out the ViSAR experiments with a 0.235 THz one-input four-output system, and obtained the real-time high-resolution SAR image of moving targets [23]. Compared to the other THz radar systems, the SAR/ISAR system has a relative simple system structure and low hardware cost, and has no limitation of target distance. The radar system operates in frequency modulated pulse mode with a bandwidth of 5 GHz, and its pulse width, duty circle, and time delay of local oscillator signal can be set flexibly This design is for the application of connecting traveling-wave tube amplifier to develop long-distance experiments in the future.
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