2022•The Journal of Korean Institute of Electromagnetic Engineering and ScienceOpen access
Design of a Compact-Sized Broadband Lumped-Distributed Balun Including Impedance Matching
Kyutaek Oh, Sangjin Yoo, Ockgoo Lee
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Abstract
In this paper, the design of a compact broadband lumped-distributed balun, including impedance matching, is suggested. For the broadband impedance characteristic of the suggested balun design, the even-mode impedances of the balun were analyzed using the differential port impedance (Zin). The proposed balun enables broadband impedance matching without an additional impedance-matching network, thereby reducing the circuit size and passive loss. The suggested balun was fabricated using FR4-based PCB and its performance was verified. The balun was designed to match a single-ended port impedance of 50 Ω and a Zin of 25 Ω. The fabricated balun has a −10-dB return loss from 550 to 950 MHz. Zin was measured to confirm impedance transformation and matching of the fabricated balun. The measured real value of impedance was 25±5 Ω and the imaginary value was 0±5 Ω from 640 to 870 MHz. The electrical length of the balun was reduced to 18°
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