A compact transistor based analog predistorter using a slow wave coupler

A compact transistor based analog predistorter (APD) using a slow-wave coupler is proposed. Compared with previously published work in [7], 72% size reduction is realized for the proposed slow-wave coupler, while 49.1% size reduction is achieved for the total APD. One prototype is designed and fabricated for verification. The simulated results of the APD show the insertion loss of 0.5 dB at 2.4 GHz with a return loss of −8.4 dB and −14.5 dB at the input and output port, respectively. Under large signal simulation, the proposed APD shows a maximum gain enhancement of 2 dB at the input power of 26 dBm, which perfectly compensates the gain compression of the main PA at this power level. The simulated output 1dB gain compression point (P1dB) of the main PA is increased from 36 dBm to 40 dBm under CW signal with the proposed APD.