A systematic methodology to design analog predistortion linearizer for dual inflection power amplifiers

This paper presents a systematic methodology to design a diode-based RF predistortion linearizer that can be used to linearize power amplifiers with dual inflection points in their distortion characteristics. The proposed structure contains anti parallel configuration of Schottky diodes, complemented with a PIN diode in parallel, connected to through and coupled ports of a 90° hybrid coupler using λ/4 transmission lines. The use of a PIN diode in the linearizer provides it with an extra level of freedom in achieving the desired level of amplitude and inflection depth in the AM/AM characteristic. A systematic design procedure using this configuration is proposed and applied to linearize a commercial power amplifier. Two tone test experimental results show that the IM3 cancellation of 10 dB in 1 MHz separation between tones at 2.14 GHz can be achieved.