Design of high-stability transmitters for pulse Doppler radars and measurement of their spectral purity

Pulse Doppler radars are most commonly used in applications where the targets of critical importance are those which, whilst having relative radial velocity, have in general much smaller effective echoing areas than the clutter in the radar resolution cell. A pulse Doppler radar transmitter must have a very high order of output stability. The actual maximum permissible peak level of any discrete spurious intraspectral component will depend upon the radar's final resolution bandwidth and upon the width of the spurious component. A description is presented of a transmitter designed to meet the requirement for a high power pulse Doppler surveillance radar. It has an RF output of 100 kW peak at a mean power of the order of 5 kW; with the ability to operate with a selected sequence of PRFs up to 10 kHz. The specification was that the intraspectral line modulation products should be more than 100 dB below the central carrier line of the output. Attention is given to details of transmitter design, aspects of instrumentation development, and methods of performance checking.