A Compact Uniplanar Rat-Race Coupler With Arbitrary Power Division Ratio and Harmonics Suppression

He, Qiang; Wen, Yinghong; Chen, Song; Wang, and Kai

doi:10.2528/pierl15011604

Cited by 4 publications

(1 citation statement)

References 18 publications

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“…Thus, the 3λ/4 UTLS requires two or more equivalent circuits. Among the previous methods [22][23][24][25][26][27][28], the Π-and T-type equivalent circuits can be easily used to suppress harmonics [29].…”

Section: Introductionmentioning

confidence: 99%

A Miniaturized 3-Db Microstrip TRD Coupled-Line Rat-Race Coupler With Harmonics Suppression

Cao¹,

Wang²,

Fang³

et al. 2016

PIER C

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A miniaturized microstrip rat-race coupler with harmonics suppression is proposed by using shorted trans-directional (TRD) coupled lines. The shorted TRD coupled lines consist of a set of capacitor-loaded λ/4 coupled microstrip lines with two shorts, which are used to replace the 3λ/4 uniform transmission-line section (UTLS) in the traditional 3λ/2 ring coupler for miniaturization. To attain perfect matching for any coupling factor of the TRD coupled lines, shorted TRD coupled lines are synthesized and the design equations are derived. To further reduce the ring size, T-type transmissionline equivalent circuits are also adopted to replace the λ/4 UTLS and associated with a transmission zero for harmonic attenuation. Using the proposed method, a microstrip ring coupler with 26.7% circuit size of a traditional one is fabricated and tested. The measured results show that the bandwidth for the return loss of better than 10 dB is 43.9% and that for isolation of better than 20 dB is 18.7% with a maximum isolation of 40.6 dB. There is no spurious passband up to the sixth harmonic of the design center frequency with more than 20 dB suppression from the third to fifth harmonics.

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