A high performance solid state modulator for radar applications

The author describes a multi-module solid state modulator for cathode pulsing a traveling wave tube (TWT) which is used in a military/ATC E/F-band ground-based surveillance radar application. When a relatively simple system waveform is specified together with modest RF power requirements, a low voltage modular PSU/modulator, utilizing FETs in conjunction with a high ratio step-up transformer with a cathode modulated TWT, can be designed that will given an entirely satisfactory performance. The TWT will not require a complex control electrode, and the use of FET switches will allow rapid turn-off under fault conditions, avoiding the need for a high-voltage crowbar protection system. The pulse transformer also acts as a protection mechanism since, under conditions of gross malfunction, the maximum pulse duration obtainable will be limited by the volt-time integral of the pulse transformer