Miniaturized Single-Ended and Balanced Dual-Band Diplexers Using Dielectric Resonators

Compact dual-band diplexers with single-ended and balanced ports based on quad-mode dielectric resonators (DRs) are proposed in this article. Two pairs of orthogonal degenerate modes are employed not only to form four frequency channels but also to achieve high isolation of dual-band diplexer. Quad-mode field distributions and couplings with input and output probes are analyzed in detail to realize dual-band diplexer characteristics. Due to the couplings of straight probes and sharing of common input and output quad-mode DRs, multiport junctions in conventional designs are saved, and the number of resonators is remarkably reduced. Therefore, miniaturized sizes are obtained in both single-ended and balanced designs. For verification, Sub-6-GHz dual-band diplexers with single-ended and balanced ports are fabricated and measured. With only two cuboid DRs and three sets of probes, low losses in all four bands and isolations that better than 34 dB are achieved in both two designs. Moreover, the common-mode (CM) suppression of the balanced diplexer is better than 50 dB. The exhibited high in- and out-of-band performance of the diplexers demonstrates the proposed method.