Which of the following is NOT one of the types of transmissions used in radar systems?

In radar systems, various types of transmissions are used to detect and analyze reflected signals. Frequency modulation, continuous wave, and pulsed Doppler are all well-established transmission methods utilized in different radar applications.

Frequency modulation involves varying the frequency of the transmitted signal to improve measurement accuracy and resilience against interference. Continuous wave radar systems transmit signals continuously, allowing them to detect the speed of a target via the Doppler effect without needing the signal to pulse. Pulsed Doppler radar combines the principles of pulsed transmission and the Doppler effect, allowing for both range and velocity measurements of a target.

On the other hand, analog modulation, as a method of varying the amplitude or phase of a carrier signal to transmit information, isn't a standard type of transmission specifically recognized for radar systems. While it can be employed in various communication contexts, radar systems primarily use the transmission types mentioned earlier for their specific operational requirements and capabilities. Hence, analog modulation does not fit into the conventional radar transmission methods, making it the correct answer for this question.