What are the trade-offs between coherent and non-coherent integration in radar detection?

2 Non-coherent integration

Non-coherent integration is a technique that discards the phase information of the received signal and adds up only the magnitude or power of the signal. This means that only the amplitude of the signal is considered in the integration process. Non-coherent integration can enhance the SNR by a factor of sqrt(N), where N is the number of pulses or samples integrated. However, non-coherent integration has a lower SNR gain than coherent integration and can lose some target information that is encoded in the phase. Moreover, non-coherent integration can introduce some noise due to the squaring operation, which can affect the detection threshold.

3 Hybrid integration

Hybrid integration is a technique that combines both coherent and non-coherent integration in a sequential or parallel manner. This means that the signal is first coherently integrated over a short time interval, and then the results are non-coherently integrated over a longer time interval, or vice versa. Hybrid integration can achieve a balance between the SNR gain and the phase error tolerance of the two methods. However, hybrid integration also inherits some of the drawbacks of both methods, such as the need for a reference signal, the sensitivity to target motion, and the noise due to squaring.

4 Integration time

Integration time is the duration over which the signal is integrated, either coherently or non-coherently. The choice of integration time depends on several factors, such as the pulse repetition frequency (PRF), the target range, the target velocity, and the clutter environment. Generally, a longer integration time can improve the SNR and the detection probability, but it can also increase the computational complexity and the delay. Moreover, a longer integration time can cause some problems, such as target fading, range ambiguity, Doppler ambiguity, and clutter correlation.

5 Integration gain

Integration gain is the measure of how much the SNR is improved by using integration techniques. The integration gain can be expressed in linear or logarithmic units, such as dB. The integration gain depends on the type of integration, the number of pulses or samples, and the signal characteristics. Typically, the integration gain is higher for coherent integration than for non-coherent integration, and it increases with the number of pulses or samples. However, the integration gain can also be affected by some factors, such as phase errors, noise, clutter, and target fluctuations.

6 Integration trade-offs

When deciding on an integration technique and an integration time for a particular radar scenario and target type, integration trade-offs must be taken into account. These compromises include choosing between coherent and non-coherent methods for higher SNR gain or lower phase error sensitivity, between short and long integration times for lower delay or higher detection probability, between low and high PRF for lower range ambiguity or higher Doppler resolution, and between constant and variable integration time for simpler implementation or adaptive performance.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?