Impedance matching circuit capable of efficiently isolating paths for multi-band power amplifier

Abstract

In accordance with a representative embodiment, an impedance matching circuit for use at an output stage of a power amplifier is disclosed. The impedance matching circuit comprises: an input port for receiving a frequency band signal; and a plurality of paths, each path being allocated with a principal band signal to be transmitted therethrough and including a path on-off network and a fixed-value impedance matching network. Depending on a type of the received frequency band signal, the path on-off network is configured to activate a selected one of the plurality of paths by rendering an input impedance of the selected path to have a lower absolute magnitude so that the signal is transmitted therethrough, and to deactivate the remaining paths of the plurality of paths by rendering the input impedance thereof to have a higher absolute magnitude so that the signal is not transmitted therethrough. The fixed-value impedance matching network matches a load impedance of the output port of each path to the input impedance thereof, thereby rendering the input impedance thereof to have a prescribed reference value with respect to the principal band signal when said path is activated by the path on-off network.