Power combining scheme for 50 kW pulsed solid state RF power amplifier unit at 325 MHz

Development of 50 kW pulsed Solid State RF Power amplifier (SSPA) unit at 325 MHz is under progress at RRCAT for our Spallation Neutron Source (SNS) program. RF Power combining is mandatory requirement for SSPA, as output of solid state RF devices is moderate. As a part of this system, 16-Way radial power combiner, 16-Way radial power divider and 100 kW (pulsed RF : pulse width-2 ms, repetition rate-50 Hz) 2-Way power combiner have been successfully designed, developed and characterized at 325 MHz. 16-Way power combiner have output at 3 1/8' inch rigid coaxial line and 16 inputs at N-type connector while 16-Way Power divider has input and 16 outputs at N- type connector. 100 kW 2-Way power combiner have two inputs and output at 3 1/8 inch rigid coaxial line. It is proposed to achieve 50 kW RF output by combining 32 nos. of previously developed pulsed 1.8 kW solid state RF amplifier modules with the help of two nos. of 16-Way radial power combiners, power dividers and one no. of 100 kW 2-Way RF power combiner. Measured return loss at 325 MHz using Rohde and Schwarz make vector network analyzer for 16-Way power combiners and 16-Way power dividers were found to be better than 23 dB and 20 dB respectively. Amplitude and phase variation of 16 nos. of coupling coefficients between input and output were limited to ± 0.1 dB and ±l1° respectively for both the structures. Return loss for 100 kW pulsed RF 2-Way power combiner at 325 MHz has been measured better than 20 dB and amplitude and phase symmetry of both inputs were better than to ± 0.03 dB and ± 0.50° respectively. (author)