Integrated Self-Diplexing Filtering Antenna Module for n78/n79 5G Front Ends

This article presents a self-diplexing filter-antenna module developed for the fifth-generation (5G) n78/n79 bands. Two half-mode substrate integrated circular cavity resonators (HMSICCRs), operating at 3.5 and 4.7 GHz, serve as dual-frequency feeds, while a pair of shorted parasitic patches forms the radiating elements, together realizing third-order bandpass filtering and dual-band radiation in a single layer. Upper side radiation nulls arise from cavity-patch coupling, whereas complementary lower side nulls are generated by λ g/2 slots etched in the HMSICCRs, producing dual pairs of nulls that sharpen out-of-band rejection. The whole prototype occupies only 0.79λ 0 × 0.428λ 0 and delivers fractional bandwidths (FBWs) of 14% and 13.5%, peak realized gains of 4.1 and 5.0 dB, and return losses better than 12 dB. Measured port isolation exceeds 30 dB across both passbands and closely matches simulation findings.