In radar terminology, coherence refers to the phase relationship between transmitted and received signals. A radar system is considered coherent when it maintains a stable phase relationship between transmitted pulses and received echoes. This coherence allows the radar to accurately measure Doppler shifts caused by the movement of targets relative to the radar.
By analyzing the phase of returned signals relative to transmitted pulses, coherent radar systems can distinguish between moving targets and stationary clutter, determine target speed, and improve overall radar performance in terms of sensitivity and accuracy. Coherent radar systems are essential in applications where precise target detection, tracking and speed measurement are critical requirements, such as in military surveillance, weather monitoring and air traffic control.
A coherent pulse refers to a radar pulse that maintains a coherent phase relationship over time.
In radar systems, coherent pulses are generated with a stable phase reference, ensuring that each pulse is transmitted with a known phase relative to previous pulses. This coherence allows the radar receiver to precisely process the returned echoes by comparing their phase with the transmitted pulses. Coherent pulses are essential for Doppler processing techniques, which rely on measuring the phase shift of returned signals to detect the speed of moving targets.
Coherent pulse radar systems use these techniques to enhance target detection capabilities and improve radar performance in complex environments with high levels of background clutter or interference.
The difference between coherent and incoherent gain lies in how each type of gain is obtained and used in radar systems. Coherent gain refers to the improvement in signal strength or detection ability achieved through coherent processing techniques, such as coherent integration and Doppler processing.
In coherent radar systems, signals from multiple radar pulses are coherently integrated over time to increase the signal-to-noise ratio (SNR) and improve detection of faint or distant targets. Coherent gain results from the accumulation of energy from coherent echoes, which improves the radar’s ability to detect and track moving targets with high precision.
On the other hand, incoherent gain refers to the improvement in signal resistance achieved by noncoherent processing methods, such as amplitude averaging or summation.
In incoherent radar systems, signals from multiple pulses are combined without regard to their phase relationship. This averaging process increases the total power of the received signal but does not provide the same level of sensitivity and accuracy in detecting Doppler shifts or distinguishing moving targets from stationary clutter as coherent processing does. Incoherent gain is simpler to implement, but generally provides lower performance compared to coherent gain in terms of radar sensitivity and target detection capabilities
