Coherence in radar refers to the property where the transmitted radar signal and the received radar echo maintain a constant phase relationship. In radar systems, coherence is crucial because it allows precise measurement of target range, speed and direction. When the received signal remains consistent with the transmitted signal, radar systems can accurately detect and analyze Doppler shift caused by the movement of the target relative to the radar. This consistency allows radar systems to distinguish between moving and stationary targets, calculate target speeds, and improve overall detection accuracy.
Coherent integration in radar involves combining multiple radar returns or returns received over a period of time to improve the signal-to-noise ratio (SNR) and improve target detection capabilities. By integrating coherent echoes received from the same target against successive radar pulses or scans, radar systems can effectively suppress noise and extract weak signals that may be masked by background noise or clutter. Coherent integration helps detect targets with low radar cross sections (RC) or in environments with high noise levels, thereby extending the radar detection range and improving overall performance in harsh conditions.
Coherent radar offers several advantages over non-coherent radar systems. First, coherent radar provides improved resolution and range accuracy due to its ability to measure phase differences between transmitted and received signals accurately. This allows coherent radar to distinguish between closely spaced targets and detect smaller objects with greater accuracy. Second, coherent radar systems can accurately measure target speeds by analyzing the Doppler shift of coherent signals, enabling reliable tracking and identification of moving targets. Finally, coherent radar systems are most effective in cluttered environments where non-coherent radars may have difficulty differentiating between targets and background noise. Overall, consistency in radar systems improves their sensitivity, accuracy, and reliability in detecting and tracking targets in various operational scenarios.