Mic linearizer for satellite communications

This paper describes the trial production results for two linearizers, one being a compact, lightweight MIC linearizer developed to improve the input-output nonlinear characteristics of an earth station HPA and the other being a new soft-limiter linearizer (SL-LRZ) followed by an amplitude limiter. The symmetric construction of the MIC linearizer is easily implemented with MIC techniques, operates over a wide frequency band and its nonlinearities can be controlled electrically. Also, the transfer characteristics of a TWTA with SL-LRZ are such that its amplitude response is linear up to saturation, it maintains constant output level beyond saturation and phase shift is not likely to occur. The TWTA with SL-LRZ can reduce intermodulation products due to nonlinearities of the TWTA in amplification of multiple carriers and can improve transmission performance when a band-limited PSK signal is amplified at close to saturation. The test-fabricated SL-LRZ is sufficiently small and lightweight for on-board application.