# Airborne Radar Staggered PRF Coherent Processing Method for Down-Looking Target Detection
## 1 Introduction
By analyzing the ambiguity function, they determined the expected value and variance of the ambiguity function of signals in multiple ambiguity ranges under arbitrary agile probability density function (PDF) conditions. [PERSON] et al. [18] proposed a coherent integration method for random pulse repetition interval and staggered pulse width, which has strong anti-jamming capability. They used the radon-non-uniform fast Fourier transform (Radon-NUFFT) method to solve the problems of non-uniform sampling and irregular range-Doppler coupling caused by random pulse repetition interval (PRI) and staggered pulse width (PW). [PERSON] et al. [19] proposed an improved sinc interpolation theory-based approach for dynamic target imaging with random pulse interval signals. They reconstructed non-uniformly sampled signals into a uniform grid in the distance-frequency domain, then constructed a matching filtering function related to the target's linear frequency modulation parameters to eliminate residual coupling between distance and azimuth, and obtained good imaging results after target motion compensation. [PERSON] et al. designed the transmission and reception of non-uniform pulse interval airborne radar. By designing the PRI of transmission and the phase-coefficient of the received pulses, the clutter in the target's environment can be suppressed, significantly improving the detection performance of targets that are submerged in clutter. [PERSON] et al. [20] addressed the issue of ambiguous clutter in airborne radar by designing random pulse intervals. Through non-uniform phase-coherent processing, they can eliminate the ambiguous clutter spectrum and analyze the maximum unambiguous range and maximum unambiguous Doppler. In addition to random PRF, PRF jitter [21; 22], adaptive PRF selection [23; 24], and other designs can also be employed to enhance the radar's de-ambiguity capability and target detection performance. For the detection of targets under radar down-looking conditions, the general approach is to suppress clutter and then use constant false-alarm rate (CFAR) detection to detect the targets after filtering out the ground clutter. Typical methods for detecting moving targets with single-channel radar include moving target indication (MTI) and moving target detection (MTD). However, due to the Doppler spectrum broadening of airborne radar, the MTI filter spectrum also needs to be large, which may result in a loss of target detection performance in the clutter spectrum vicinity. Under airborne radar conditions, due to the complex clutter environment, the MTI filter parameters must be adaptively adjusted according to the actual clutter changes to effectively attenuate the clutter. In addition, to detect low-speed targets on the ground, such as trucks and tanks, the MTI filter must have a wide enough passband and steep transition band. [PERSON] et al. (2019) proposed a flexible filter design method that can not only adaptively adjust the filter parameters according to the actual clutter conditions, but also prevent the attenuation of slow-moving targets. A new method based on \"filter-then-adapt\" was proposed in ([PERSON] et al., 2019) for single-channel airborne radar. The new method can weaken non-uniformity and adaptively suppress clutter. [PERSON] et al. (2019) proposed an adaptive clutter suppression method based on echo power. The center frequency and bandwidth of the clutter spectrum were effectively estimated using prior information and polar coordinate centroid method. The echo power in each range bin was used to design an adaptive notch filter with dual threshold control. The detection capability of slow-moving ground targets is a necessary condition for the effective engagement of ground targets by combat aircraft ([PERSON] et al., 2019; [PERSON] et al., 2020; [PERSON] et al., 2020).