Multiband and Multimode Concurrent PA With Novel Intermodulation Tuning Network for Linearity Improvement

For multiband power amplifiers (PAs), high impedance at the second-order intermodulation frequencies at the drain can result in severe nonlinear distortion in concurrent mode. To solve this problem, a novel intermodulation tuning network (IMTN) is proposed in this letter. The IMTN is in parallel to the output matching network and has multiple impedance zeros at low frequencies. Therefore, the improvement in linearity is evident even if the frequency difference of two operating bands of PA is relatively large. Experimental measurement is carried out with three sets of dual-band 10-MHz LTE modulated signals, and the carrier frequencies are 1.8/2.1, 2.1/2.6, and 1.8/2.6 GHz, respectively. In mode 2 with 500-MHz frequency difference, the adjacent channel power ratio is improved by 6 dB compared with the conventional PA without IMTN, and in mode 3 with 800-MHz frequency difference, 3 dB is improved compared with low-pass IMTN. The measured average efficiencies of three modes are 40.3%, 36.4% and 37.6%, respectively, at 35-dBm total output power.