Low cost solution to enhance performance of CDMA repeater amplifier

In this paper, a simple predistorter with circuit parameters controlled according to input power is presented to expand linearization power range in application of repeater system. The nonlinearity characteristic of the predistorter and power amplifier (PA) are investigated. A 16 watt CDMA PA is built for testing the linearization performance. An adjacent channel power ratio (ACPR) improvement from 4 to 6 dB has been achieved over 16-dB output power range. The ACPR improvement is 4 dB over traditional predistortion at the output power of 30dBm and 46 dBm. When combined with dynamic PA bias current control, both linearity and efficiency can be improved. A power-added efficiency (PAE) improvement of 1.5% is achieved at 30 dBm output power while the ACPR improvement is 6 dB at 42dBm output power, respectively.