A Ka-band analog predistortion linearizer for travelling wave tube amplifiers

In order to compensate the nonlinear distortion of the traveling wave tube amplifiers (TWTAs), a new analog predistortion linearizer based on vector synthesis technique is presented. This linearizer consists of quadrature hybrids, adjustable analog attenuator based on PIN diodes and nonlinear circuit based on Schottky diodes. The analog predistortion linearizer can realize the expansion of amplitude and phase within the operating frequency (29~31 GHz) and rated input power range and achieve the compensation effect of different amplitudes and phases in reasonably adjusting the bias voltages of PIN and Schottky diodes. The Third Order Intermodulation (TOI) of a Ka-band TWTA was improved about 8.1 dB at -6dB output power back off (OBO) thanks to this proposed predistortion linearizer.