What will happen to the transmitted signal and reflected signal if there is relative motion?

When there is relative motion between the radar system and a target, the transmitted signal and the reflected signal will experience a change in frequency due to the Doppler effect. This effect occurs when the source of the waves (the radar) and the observer (the target reflecting the signal) move relative to each other.

As the target moves toward the radar, the frequency of the reflected signal increases, resulting in a higher frequency than the original transmitted signal. Conversely, if the target is moving away, the reflected signal’s frequency decreases. Therefore, when relative motion is present, the frequencies of the transmitted and reflected signals will differ, making it clear that they have different frequencies.

This principle is essential for radar operation, as it enables the detection of motion and the calculation of speed and direction of the moving target based on the frequency shift observed.