Design of a predistorter controlling individual orders of intermodulation using a new harmonic generator

초록

A new type of predistortion linearizer is presented which uses individual orders of intermodulation to linearize a power amplifier. This new predistortion linearizer has two harmonic generators, each consisting of four diodes biased independently. Since the four diodes can operate at different operating points, the harmonic generator easily generates the third-order intermodulation (IM3) or the fifth-order intermodulation (IM5) components individually. The suggested predistortion linearizer was designed to operate in the Korea PCS band (1840 to 1870 MHz). Two-tone test results show that the improvement in IM3 cancellation is more than 20 dB and 10 dB for IM5. The adjacent channel power ratio (ACPR) is improved by more than 10 dB in the CDMA (IS-95) signal test; this improvement is maintained over a broad range of output power level.