Compact Filtering Rat-Race Hybrid With Wide Stopband

Abstract

This paper presents a novel method to design filtering rat-race hybrids with wide-stopband bandpass responses. Four -inverters with bandpass functions are utilized to replace the one or three quarter-wavelength transmission lines in the conventional rat-race hybrid. The -inverters consist of transmission lines and capacitors, which can reduce the area occupied and suppress the high-order harmonics. Furthermore, the isolation performance is enhanced by embedding the -inverters. Theoretical analysis is carried out and design equations are derived. For demonstration, a filtering rat-race hybrid with bandpass responses is implemented. The center frequency is located at 470 MHz with the insertion loss of 1.2 dB. Good in-phase and out-of-phase characteristics are observed. Comparisons between the measured and simulated results are also presented to verify the theoretical analysis. The overall size is only 4.6% of the conventional hybrid and stopband is extended to .Index Terms-Bandpass response, dual function, rat-race hybrid, size reduction, wide stopband. Manuscript

Compact substrate integrated waveguide rat‐race filtering couplers with arbitrary angular interval between ports

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A Miniaturized Filtering 3-Db Branch-Line Hybrid Coupler With Wide Suppression Band

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“…With the aid of the transmission line theory, we can see that a quarter-wavelength transmission line has an impedance inverse transform function, so it can be used as a K-inverter. In [11], the analysis is carried out to indicate that the structure represented in Fig. 2(a) can be functioned as a K-inverter.…”

“…2(b), two equivalent resonators coupled with each other by using two capacitors C E . The fundamental resonant frequency and the second harmonic of the resonator can be calculated from [11]. Fig.…”

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