Versatile FET nonlinear transfer function generator elements

A simple, high-performance method of generating nonlinear transfer functions useful in the production of limiters and linearizers has been discovered. This technique uses GaAs MESFETs in a passive configuration similar to that used for MMIC switches and attenuators. The resulting FET nonlinear generator elements (NLGEs) are readily adjustable over a wide range of both magnitude and phase transfer characteristics and have displayed wide bandwidth performance and excellent thermal stability. FET NLGEs have been applied in both reflective and transmissive networks. A near-perfect hard limiter has been produced using an FET NLGE which introduces less than a 5 degrees phase change. Linearizers using FET NLGEs have been tested at L-, C-, and Ku-bands and have provided a reduction in total intermodulation distortion products greater than 10 dB at the 2- and 3-dB output power backoff points over a bandwidth of up to 15%.<
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