微波工程期中報告 論文研討 :

Quarter-wavelength Resonator Bandpass Filter with Wide Stopband using Discriminating Coupling

作者： Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3 出處： Proceedings of the Asia-Pacific Microwave Conference 2011

報告人 : 碩研通訊一甲 MA130224 李堅誌

Southern Taiwan UniversitySouthern Taiwan University Department of Electronic Engineering

摘要 A simple quarter-wavelength bandpass filter

(BPF) with wide stopband is proposed. The harmonic suppression is achieved by

discriminating coupling. Using an appropriate coupling region, coupling coefficient at the third harmonic is almost zero whereas that in the passband can be tuned to the desired value.

An example filter is designed, manufactured and tested. The measurements show 20-dB rejection level from 1.16f0 to 6f0.

It confirms the feasibility of the method. Index Terms —Bandpass filter (BPF), discriminating coupling, harmonic suppression.

2Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3

分析 BPF Fig. 1 illustrates the

proposed wide stopband BPF. It consists of three/4

resonators. Appropriate coupling region

is used to guarantee zero coupling coefficient at the unwanted passband

The input and output are tapped at the resonators of both sides with characteristic impedance of 50

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Electric coupling coefficient is a function of two coupling resonators’ electric field strengths as shown in (1) [14].

Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3

電壓分佈

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■ Thus, the coupling coefficient between two resonators can be expressed in terms of voltage distribution because electric field is proportional to the voltage for quasi-TEM mode.Then, the coupling coefficient can be expressed as (2).

Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3

耦合係數 Fig. 3, the coupling coefficient of

the fundamental mode will decrease as the gap width S1 increases; hence, the desired coupling coefficient in the passband can be attained by choosing an appropriate gap.

The coupling coefficient of the third harmonic, is close to zero with little variation. It is concluded that the discriminating coupling can lead to the proper coupling coefficient in the designed passband while it can suppress the third harmonic effectively.

5Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3

Fig. 5, the centre frequency of the proposed filter is 1.643 GHz and the fraction bandwidth (FBW) is 12.5%. The insertion loss is 1.5-dB and return loss is greater than 15-dBwithin the passband.

The spurious response is below 20-dB from 1.88 GHz to 10 GHz (1.16f0-6f0). That is, the thirdb harmonic is successfully suppressed in the design.

It demonstrates that the proposed design procedure is effective for the third harmonic suppression.

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測量模擬結果

Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3

結論

Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3

心得讀完這篇 pdf檔後讓我了解到反射係數與阻抗匹配，正好我剛碰上反射係數太高，但卻不太了解這是怎麼樣的一個情況，不知道怎麼解決。但是剛好藉由這篇有提到阻抗匹配後我在去取得其他資料後我已經把問題解決了。

Proceedings of the Asia-Pacific Microwave Conference 2011Yuan Chun Li *1, Xiu Yin Zhang *2, Quan Xue *3