The use of a sideband filter in continuous wave (CW) radar is to isolate the Doppler shift frequencies which are essential for detecting the speed of moving targets. By filtering out unwanted frequencies and focusing on the frequency shift introduced by target movement, the sideband filter helps accurately measure Doppler shift and, therefore, target velocity.
The Doppler effect is used in CW radar to measure the speed of a moving target. As the target moves, it causes a shift in the frequency of the radar waves reflected back to the receiver. This frequency shift, known as Doppler shift, is proportional to the speed of the target. By analyzing this offset, the CW radar can determine the speed of the target.
The components of the CW radar include a transmitter, which continuously emits a radar signal; a receiver, which captures the reflected signal; an antenna, which is used for transmitting and receiving signals; and a signal processing unit, which analyzes the received signals to extract information about the speed of the target.
Isolation between the transmitter and receiver in CW radar is necessary to prevent interference between the outgoing radar signal and the incoming reflected signal. Without proper isolation, the strong transmitted signal could overwhelm the receiver and mask the weaker reflected signals, making it difficult to detect and measure targets accurately.
The difference between CW Doppler radar and FMCW (frequency modulated continuous wave) radar is their signal modulation. CW Doppler radar uses a constant frequency wave to detect frequency changes due to the Doppler effect, which provides information about the target speed. FMCW radar, on the other hand, modulates the frequency of the continuous wave over time. This modulation allows the FMCW radar to measure both the distance and speed of the target by analyzing the frequency shift and delay of the reflected signal.