Dual-Channel Dielectric Resonator Filter and Its Application to Doherty Power Amplifier for 5G Massive MIMO System

In this paper, a dual-channel dielectric resonator (DR) filter is presented for the first time. Two bandpass filters (BPFs) are integrated as one dual-channel filter with two input ports and two output ports. By using a common quad-mode DR shared by two second-order BPFs, only one metallic cavity is needed, which greatly reduces the circuit size. Frequency control of the DR is investigated and electromagnetic field properties at HEH11 and HEE11 resonant pairs are studied for guiding the dual-channel filter realization. By properly arranging the input and output feeding probes, two of the resonant modes are excited for one channel and other two for the other channel. Since the feeding probes of one channel filter do not excite the resonant modes of the other one, isolation between two filters is achieved. Three transmission zeros are generated near the passband, resulting in high selectivity. For verification, the dualchannel filter is implemented, which features good bandpass responses and offers a significant size reduction in comparison with conventional two DR filters. What is more, the dualchannel filter with the impedance transformation function is integrated with a 2 × 2 Doherty power amplifier for 5G massive multiple-input multiple-output system application, featuring high efficiency, good filtering responses, and high integration.