[12] “Balanced Rat -Race Couplers with Wide-band Common-Mode Suppression,” IEEE Transactions on Microwave Theory and Techniques, vol. 67, no.12, pp. 4724-4732, Dec. 2019.

作者：Wenjie Feng, Wenquan Che*, Yongrong Shi, Roberto Gómez-García, Chenxu Wang, Quan Xue, Xiu Yin Zhang, Xin Yu Zhou

摘要：In this article, various types of six-port balanced rat-race couplers with wideband common-mode suppression characteristics are presented. In these couplers, the input and output ports can functionalize either as single-ended or differential terminals to realize different operational modes. The power-splitting ratio for these balanced couplers can be flexibly adjusted by means of the values of the characteristic-impedance parameters of their constituent transmission-line segments. Furthermore, the employment of double-sided-parallel-strip-line(DSPSL)-based 180◦ phase inverters instead of half-wavelength transmission-line-based ones allows for the considerable enlargement of their operation bandwidth in more-compact circuits with lower in-band insertion-loss levels. For experimental-validation purposes, two microstrip prototypes at f0 =0.9 GHz with equal and unequal power division are fabricated and characterized. They exhibit common-mode rejection levels higher than 15 dB from 0 to 1.8 GHz (i.e., 0–2 f0) and differential-to-commonmode-conversion suppression levels above 15 dB within the spectral range 0–1.49 GHz (i.e., 0–1.65 f0).