GaN based L-band high power and high efficiency pulsed transmitter

This paper illustrates the design and development of L-Band GaN based high power, high efficiency pulsed transmitter to deliver peak output power of 50W at centre frequency of 1.25 GHz with 75 MHz bandwidth. This L-Band transmitter has been designed and developed for dual frequency (L&S-Band) airborne SAR mission. Size, weight and power constraints led to the selection of GaN HEMT devices which offer inherently higher efficiency compared to GaAsFET devices. Class-F approach has been used for the design of power amplifier stages to enhance the efficiency of transmitter. Power Added Efficiency (PAE) of more than 50% is achieved from the integrated transmitter. Transmitter was characterized for all 64 phase states using a 6-bit digital phase shifter. Comparison of simulated and test results of various amplifier stages along with summary of specifications and test results of pulsed transmitter is given to validate the design.