Based on a novel right-angled triangle artificial line, a branch-line coupler is designed in this letter. The measured results indicate that the proposed branch-line operates at 0.975 GHz with a stopband bandwidth more than 15fc. Here, fc is the center frequency of the coupler. Importantly, the suppression levels in the stopband are better than 15 dB. Besides, its occupied size is about 23.18×22.5 mm2, which is only 16.5% of a traditional one at the same operating band. In practice, the proposed branch-line coupler can be used in compact systems which require good high-order harmonic suppression.
2. Coromina, J., J. Selga, P. Velez, J. Bonache, and F. Martın, "Size reduction and harmonic suppression in branch line couplers implemented by means of capacitively loaded slow-wave transmission lines," Microwave & Optical Technology Letters, Vol. 59, No. 11, 2822-2830, 2017.
doi:10.1002/mop.30837
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doi:10.1049/iet-map.2018.5379
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