A Quad-Band Power Amplifier Based on Impedance Frequency Modulation

This brief presents a novel method to design a multiband power amplifier. A coupler is used as the amplifier output circuit for achieving multiband impedance transformation. In order to support multiband operation, the coupler is modified with inserting a reactance to ground. Thus, the terminal impedance can be made to change with frequency. Further, realization of the desired frequencies of operation for a required PA design are obtained by combining the obtained periodical impedance trajectory and class-EFJ PA’s impedance space. For validation, a quad-band power amplifier is designed and fabricated using the proposed method. Measurements show that the power amplifier can deliver output power of above 40.3 dBm, with drain efficiency of over 63% in the four frequency bands 0.5 GHz, 1.5 GHz, 2.5 GHz, and 3.5 GHz.