Aperture effect influence and analysis of stepped frequency wideband phased array radar

Wideband phased array has high range resolution. It can realize target recognition and radar imaging, which provides key technical support for modern high-performance radar meeting the future war demand. However, the aperture effect will cause the beam-pointing shift, broaden the main lobe of the one-dimension target range profile, lower the resolution, and reduce the signal to noise ratio (SNR). Each pulse in the standard stepped frequency waveform is a narrow band signal. It achieves the large instantaneous wideband by the synthesis of the pulse sequence. Therefore we can use interveinal phase matching to compensate the aperture effect. This paper analyzes the relationship between the wideband antenna beam-pointing with the instantaneous signal frequency, and introduces the principle of stepped frequency synthesis wideband, then simulates the method of interveinal phase matching, the simulation results show that this method can compensate the aperture effect of stepped frequency wideband phased array effectively, lastly get high resolution and high precision one-dimension target range profile.

1. Introduction

Phased array radar is one of the hot spot in the field of radar research now; it can achieve the functions of more than one conventional radars. Wideband has high range resolution; it can be used for radar imaging and target recognition etc. There are tow commonly methods to realize the wideband signal: one is the Linear Frequency Modulation (LFM) and the other is to synthesise instantaneous wideband signal by stepped frequency. However, the antenna of wide ban phased array radar system has thousands of array elements; it controls the antenna beam-pointing through the phase shifters. There exists the influence of aperture effect, which will cause the beam-pointing direction offset, the more broaden of the instantaneous bandwidth, the bigger of the beam-pointing offset. After the processing of signal compression, the one-dimension range profile will shift, the main lobe will broaden, and the Signal to Noise Ratio (SNR) will decline. All of these phenomena influence subsequent signal and data processing seriously, so it needs to take measures to compensate the aperture effect of wideband phased array radar.