本論文利用砷化鎵積體電路製程來實現單晶片吸收式帶止濾波器，以配合發展ALMA (Atacama Large Millimeter/Submillimeter Array) Band-1無線電波天文望遠鏡接收機。此帶止濾波器可吸收接收機中混波器的LO至RF洩漏訊號，從而降低LO至RF路徑之隔離度不佳所造成之混波器轉換增益變差的問題。 論文的第一部分將著重於新式吸收式帶止濾波器設計方法，並提出一套完整的設計流程及公式。有別於先前文獻利用多重耦合架構造成止帶訊號相消而產生吸收式止帶效果，本研究於帶止濾波器之共振器中引入適當電阻，有效地消耗掉反射訊號，達成吸收式止帶，並以一個三階吸收式帶止濾波器設計，驗證所提之設計流程與設計公式。濾波器之中心頻率為2 GHz、比例頻寬5%，並具有0.01dB等鏈波響應。實測之通帶內反射損耗均大於17.5 dB，止帶內最大穿透損耗大為33.3 dB，止帶最大功率損耗則為99.8%。 論文的第二部分則進行Q-Band吸收式帶止濾波器之研發，以應用於ALMA Band-1接收機系統中。其止帶範圍為31-33 GHz，比例頻寬約為7%，通帶範圍為35-52 GHz，並實現於穩懋半導體之0.15-m pHEMT製程，晶片面積為2.5mm×2 mm。由量測結果，於止帶中濾波器可吸收至少93.4%的LO至RF洩漏訊號，止帶中心頻(32GHz)之抑止度可達35.6 dB；通帶範圍內最大穿透損耗為2.44 dB，最小反射損耗為15.23 dB。又為提昇鏡相頻帶之抑制效果，另將吸收式帶止濾波器與寬頻帶通濾波器整合於單一晶片上，以利實現高度積體化與高整合度的接收機。 相較於既有文獻，本論文所提出之新式吸收式帶止濾波器具有更高的設計彈性，包括止帶頻寬、止帶頻率選擇度及通帶內鏈波均可依所需規格設計，並提出一整套簡潔明瞭的設計流程做為設計工具，可依據系統規格快速求算設計參數，有助於推展吸收式帶止濾波器於收發機系統之應用。 ;In this study, in order to cooperate with the development of ALMA (Atacama Large Milli- meter/Submillimeter Array) Band-1 receiver front-end, novel absorptive bandstop filter (ABSF) implemented using GaAs semiconductor process is proposed. The proposed ABSF can help minimize the impact of LO-to-RF leakage on the conversion loss degradation of mixer in the ALMA Band-1 receiver. First, novel design method of ABSF is proposed and a complete design procedure and formulae are established. The proposed ABSF structure is based on introducing resistor to the bandstop resonator appropriately so as to dissipate the reflected signals in the stopband. The design of a 3rd-order ABSF is presented to demonstrate the achieved performance, and it is used for verifying the proposed design formulas. The ABSF is designed with a fractional bandwidth of 5% and a center frequency of 2 GHz. The measured return loss is better than 17.92 dB in the passband. The measured rejection at stopband center frequency is 34.83 dB, and the maximum stopband power dissipation is 99.8%. Second, the Q-Band ABSF for ALMA Band-1 receiver application is proposed. The stopband frequency is from 31 to 33 GHz, which corresponds to a stopband fractional bandwidth of about 7%. The passband frequency is from 35 to 52 GHz. The ABSF is implemented in GaAs using the WIN 0.15 um pHEMT process, and the chip size is 2.5 mm×2 mm. In the measured results, more than 93.4% of the power within the stopband can be dissipated by the proposed ABSF, and the rejection at the stopband center frequency is 35.6 dB. The insertion loss is better than 2.44 dB and the return loss is better than 15.23 dB in the passband. To facilitate the receiver system integration, the proposed ABSF is then integrated with the bandpass filter on the same chip. Compared with other related previous works, the proposed ABSF features a complete and simple design procedure with better design flexibility. The stopband bandwidth, filter selectivity and passband ripple can all be designed according to the specifications. The proposed ABSF is easy to realize such that it is helpful for applications in front-end receiver designs.
