A triple-power-mode power amplifier using an Rx band noise reduction circuit for W-CDMA/LTE handsets

A triple-power-mode power amplifier (PA) using a receive (Rx) band noise reduction circuit for W-CDMA/LTE handsets is described. The Rx band noise reduction circuit uses an LC trap circuit resonating at the difference frequency between transmit (Tx) and Rx signals, and suppresses the Rx band noise caused by mixing with the Tx signal and the difference frequency noise which comes from an input matching network and a bias circuit in the PA. The PA accommodates switchable signal paths corresponding to triple (high, middle and low) power modes for saving battery current in practical handset use. Simulations show an Rx band noise improvement of 3.5 dB due to the LC trap circuit, and measurements show both a low Rx band noise of -136 dBm/Hz and a high gain of 30 dB at 29dBm of Pout. Measurements also show that the PA achieves PAE as high as 41% at Pout of 29dBm while keeping ACLR less than -38dBc in the high power mode under a condition of 3.4V Vcc and 1450MHz W-CDMA (3GPP Rel.99) modulated signals. In the middle and low power modes, PAE of 22 % at Pout of 18dBm and 16 % at 7dBm are obtained with the same condition, respectively.