volume | PIER Journals

2012-04-23

A High Performance Balun Bandpass Filter with Very Simple Structure

Wei Kang,

Dr. Wei Kang

Ministerial Key Laboratory of JGMT

Nanjing University of Science and Technology

China

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Hui Wang,

Dr. Hui Wang

Nanjing University of Science and Technology

China

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Chen Miao,

Dr. Chen Miao

Ministerial Key Laboratory of JGMT

Nanjing University of Science and Technology

China

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Chen Tan,

Dr. Chen Tan

Ministerial Key Laboratory of JGMT

Nanjing University of Science and Technology

China

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Wen Wu

Dr. Wen Wu

Nanjing University of Science & Technology

China

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Progress In Electromagnetics Research Letters, Vol. 31, 169-176, 2012

doi:10.2528/PIERL12030406

Abstract

A high performance balun bandpass filter (BPF) with very simple structure is proposed in this letter, this structure realizes superior performance in bandpass filtering meanwhile with good differential performance of the balun. The proper balanced outputs and BPF characteristic by the symmetric feeding and skew-symmetric feeding have been obtained, and the theory of this simple structure for unbalanced input to balanced outputs has been studied. The center frequency of the fabricated balun-BPF was operated at 2.4 GHz with 5.8% fractional bandwidth (FBW), and this frequency is used for Bluetooth and some other communication systems. The differences between the two outputs are 180° ± 5° in phase and within 0.39 dB in magnitude. At f₀, the amplitude imbalanced and phase difference are within 0.37 dB and 179.2°, respectively. The measured frequency responses agree well with the simulated ones. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and good performance of both BPF and balun.

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Wei Kang, Hui Wang, Chen Miao, Chen Tan, and Wen Wu, "A High Performance Balun Bandpass Filter with Very Simple Structure," Progress In Electromagnetics Research Letters, Vol. 31, 169-176, 2012.
doi:10.2528/PIERL12030406

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