A coherent processing interval (CPI) in radar refers to a specific duration during which the radar system collects and processes coherent radar returns. Coherence in this context refers to maintaining a stable phase relationship between the radar pulses transmitted and received echoes over the duration of the IPC. The length of the IPC is determined by factors such as the radar’s pulse repetition frequency (PRF), the desired range resolution, and the Doppler resolution required to detect moving targets.
During a coherent processing interval, the radar transmitter sends a series of coherent pulses, with each pulse generated with precise timing and phase relationship to previous pulses. The radar receiver collects returned echoes from targets and background clutter, maintaining phase coherence with the transmitted pulses. Coherent processing allows the radar system to combine or integrate multiple received echoes into the IPC to improve the signal-to-noise ratio (SNR) and improve detection of faint or distant targets. The length of the coherent processing interval is critical in determining the radar’s ability to resolve targets within range, accurately measure Doppler, and reduce the effects of noise and interference in radar operations.
In radar terminology, coherence refers to the stable phase relationship between transmitted and received radar signals. A radar system would be coherent when it maintains this phase relationship consistently over time and across multiple radar pulses. Coherence is essential in radar because it allows precise measurement and analysis of Doppler shifts produced by moving targets. By comparing the phase of received signals with the phase of transmitted pulses, coherent radar systems can detect frequency changes caused by the movement of targets relative to the radar. This capability allows radar systems to distinguish between moving targets and stationary clutter, track the speed of moving objects, and improve overall radar performance in terms of sensitivity and accuracy. Coherent radar systems are widely used in applications such as air traffic control, weather monitoring, military surveillance and scientific research where precise target detection and tracking are critical requirements.