M.V. Skupyako - Leading Engineer, SCD JSC «LEMZ R&P Corp.», Moscow. E-mail: skupyako@gmail.com
A.Yu. Mlinnik - Senior Research Scientist, SCD JSC «LEMZ R&P Corp.», Moscow. E-mail: otdel5.kblira@gmail.com
S.V. Monin - Head of Department, SCD JSC «LEMZ R&P Corp.», Moscow. E-mail: otdel5.kblira@gmail.com

The performance of modern multimode coherent radar transmitters with microwave tube significantly depends on the pulse modulator topology used. So the problems of high efficient modulators developing are very important. Because of advantages of grid-controlled tube amplifiers compared to anode-controlled ones, grid modulator versions are considered only. The MOSFET modulator topology with wide ranges of the pulse width and repetition frequency is offered. Its high-voltage switches consist of a few MOSFETs connected in series to withstand applied voltage. Principle of operation is based on the ability of a MOSFET to hold charge on the gate for some time, depending on the leakage current in its circuit. Charge and discharge of gate-source capacitance are carried out by short pulses of a fixed duration, generated by sub-modulator. Such pulses can be easily transferred by means of compact pulse isolation transformer. The MOSFET gate driving circuit is described. Detailed time diagrams of operation are shown. The examples of the solid-state modulator on the PCB and filament-modulating unit designed in practice are presented. Main parameters of these designs are: pulse width from 1 to 1000 µs; pulse repetition period greater than 20 µs; cut-on voltage from 0 to 15 V; bias voltage from 2500 to 3000 V; amplitude pulse-to-pulse fluctuation less than 0.005%; power loss at the switches of modulator 8 W; insulation voltage 15 kV. Such solid-state modulators have been developed, put into series production and successfully operate as parts of radars for various purposes.