Coherent radar systems provide information on a target which cannot be detected with basic pulse radar. Magnetrons are not suitable for such systems. The alternative is to use travelling wave tubes or solid-state amplifiers, but these have a limited peak output power. This problem can be overcome by using longer pulses to increase the pulse energy and subsequently compressing the pulse in a surface acoustic wave (SAW) matched filter. The paper reviews the need for pulse compression radar and describes basic SAW technology.