Balanced-to-Single-Ended Filtering Power Divider Using Multilayer Mixed-Mode Magic-T

A type of balanced-to-single-ended (BTSE) filtering power divider (FPD) using multilayer mixed-mode magic-T is reported. Based on grounded coplanar waveguide (GCPW) to slotline transitions, a mixed-mode magic-T is firstly discussed. It attains out-of-phase and in-phase wideband distributed responses by means of the balanced port E and the single-ended port H, respectively. Then, by coupling the designed mixed-mode magic-T with a stub-loaded resonator (SLR), a BTSE FPD with its port H terminated by a 50-ohm load is proposed. Due to the employed microstrip SLR along with the coupled pair of L-shaped slotline sections, the designed FPD can feature a second-order high- selectivity differential-mode (DM) filtering response with two close-to-passband transmission zeros (TZs) and high broadband common-mode (CM) rejection. Moreover, for experimental- demonstration purposes, two proof-of-concept prototypes corresponding to a mixed-mode magic-T and a BTSE FPD are developed and tested. The mixed-mode magic-T is measured with a BTSE 10-dB return-loss bandwidth from 2.05 to 3.78 GHz and a single-ended-to-single-ended (SETSE) 10-dB return-loss bandwidth from 1.5 to 4.5 GHz, respectively. The measured BTSE FPD features a 10-dB return-loss DM bandwidth of 8.36% along with power isolation levels above 17.7 dB at the output ports and two TZs located 2.74 and 3.55 GHz, respectively.