Coherent Radar -- How do we justify it?

1. What is coherent in radar?
2. How is coherent integration achieved?
3. What is coherent processing interval in radar?
4. What is coherent processing?

What is coherent in radar?

A coherent radar compares the phase or frequency of a target echo with a stable oscillator or reference signal source. Natural objects, such as trees or islands, tend to be relatively steady in phase or frequency. (An important exception is the Doppler-shifted frequency of echoes from weather phenomena.)

How is coherent integration achieved?

With coherent integration we insert a coherent integrator, or signal processor, between the matched filter and amplitude detector as shown in Figure 1. The signal processor samples the return from each transmit pulse at a spacing equal to the range resolution of the radar set and adds the returns from N pulses.

What is coherent processing interval in radar?

5.6. As seen, the beat signal is sampled at the rate of the low-end ADC (sampling frequency f_s) during a long period of time (say some seconds). For a coherent radar, the total time to be sampled is referred to as the coherent processing interval (CPI).

What is coherent processing?

In signal processing, the coherence is a statistic that can be used to examine the relation between two signals or data sets. It is commonly used to estimate the power transfer between input and output of a linear system.