# Airborne Radar Staggered PRF Coherent Processing Method for Down-Looking Target Detection
## 4 Simulation Results
### Target Detection Clutter Avoidance and Track Integrity Analysis
(**a**) Velocity of target. (**b**) Distance of target. Figure 20: Target power under different PRFs after processing. Figure 21 reveals that traditional Multi-MPRF exhibits low-target SNR due to limited coherent processing within each group, resulting in the inability to detect targets beyond a distance of 13.2 km. In LPRF mode, stable target detection is achieved when the target is far from the ground. However, during the target's hovering phase above the ground, robust detection is hindered by the overlap between the target and ground clutter Doppler spectrum, where the target power is lower than the clutter power. This leads to missed detections during the time periods of 116-136 s and 166-186 s. In HPRF mode, severe distance ambiguity creates blind zones within the ground clutter Doppler spectrum and in each range bin. Consequently, missed detections occur at any distance when the target Doppler was covered by the clutter Doppler spectrum. The multi-group LPRF cross-transmission designed in this paper, optimized to minimize blind zones and enable ambiguity resolution, exhibits minimal missed detections throughout the target's trajectory. Using solely LPRF or HPRF poses limitations in accurately extracting both distance and velocity parameters of the target simultaneously. Figure 22 displays the experimental measurement results for target distance and velocity. Figure 21: The target detection result of using different operating mode. (**a**) The detection result of LPRF. (**b**) The detection result of HPRF. (**c**) The detection result of Multi-MPRF. (**d**) The detection result of the method of this paper. Figure 22 illustrates that LPRF, Multi-MPRF, and the proposed method accurately extract target distance, whereas HPRF suffers from severe distance ambiguity and cannot accurately reflect the true target distance. In terms of target speed estimation, HPRF, Multi-MPRF, and the proposed method provide accurate results, while LPRF exhibits speed ambiguity within the detectable range. The proposed method employs a range-speed ambiguity resolution technique similar to traditional Multi-MPRF, enabling simultaneous and accurate estimation of target distance and speed. Additionally, by utilizing at least three groups of signals for coherent processing within five groups, the proposed method achieves a three-times increase in SNR gain, expanding the theoretical power range of the radar by 1.48 times compared to traditional Multi-MPRF. In the experiment, Newton interpolation was applied to estimate the target distance and speed based on the detection results. Figure 23 displays the parameter estimation error results. Analysis of the distance error is limited to LPRF, traditional Multi-MPRF, and the proposed method, while speed error analysis covers only HPRF, Multi-MPRF, and the proposed method. Traditional Multi-MPRF exhibits a smaller SNR gain from signal processing, leading to larger measurement error variance within the detectable segment compared to the other three methods. The proposed method, performing coherent processing within three groups of five PRFs, yields a relatively smaller SNR in signal processing compared to LPRF and HPRF. Consequently, distance measurement error variance is slightly larger than that of LPRF, while speed measurement error variance is slightly larger than that of HPRF. These findings demonstrate the effectiveness of the proposed method in detecting airborne targets in the radar's down-looking mode, accurately extracting target distance and speed information, and achieving an extended operating distance (power range) compared to traditional Multi-MPRF methods for resolving two-dimensional ambiguity between range and Doppler. Figure 22: The result of measuring the target distance and velocity in different modes. (**a**) The result of measuring the target distance. (**b**) The result of measuring the target velocity.