特高頻關鍵元組件技術研究

Abstract

子計畫一: 本計劃係開發二種特高頻(W-頻段)90o 垂交混成器(90o quadrature hybrid)，第一種係矩形金屬 波導E-平面分支波導垂交混成器，此雖已經十分成熟，但因頻率極高，所以E-平面T-接面之等效 電抗必須精準估計才可能成功，本子計畫將利用3-D 電磁軟體將電路作性能之最佳化。第二種為基 板整合波導Riblet 短槽垂交混成器(substrate integrated waveguide Riblet short slot quadrature hybrid)，此為最近幾年十分熱門的電路，本計畫擬將工作頻率上推至W-頻段。以上二 種電路都是以能與平面電路結合做考量，第一種係E-平面電路可與子計畫三之E-平面轉換器結合， 第二種基板整合波導本身便是平面電路，唯所使用之基板將選用與平面電路一致的基板。  子計畫二: 本計畫在於設計一個高階項的特高頻混頻器。我們將電路的輸入射頻選定為W-頻段中的 90-99GHz，而降下來的中頻為9-18GHz。藉由兩個乘以三的乘法器電路，將外界注入的9GHz 本地震 盪器頻率，提高到81GHz，然後提供給核心混頻電路使用。因此，可使用半導體製程達到混頻階數 為九的有效混頻目的。為了確保只有選定的頻率訊號會被降頻及偵測到，我們又設計了一個主動式 的9-18GHz 帶通濾波器電路。  子計畫三: 由於電路微小化的趨勢，同時也因為微波及毫米波積體電路的高度發展，現今絕大多數的元件及 系統是以微帶線(microstrip line)或共平面波導管(coplanar waveguide, CPW)等平面傳輸線的形式來設 計。但是為了因應量測或系統整合上的需要，各種微帶線或共平面波導管至其他傳輸線或波導管的 轉換器便有其必要性。在低頻率的應用上，大多採用微帶線至同軸線SMA 接頭的轉換器設計。但是 一旦到了高頻率的應用上，如毫米波頻段，這種轉換器便無法使用。較常見且實用的作法是微帶線 至波導管的轉換器設計。不管是高頻率或低頻率的應用，這些轉換器的設計都必須滿足低反射係數、 低耗損、寬頻且功能表現穩定等要求。本計畫的目的是設計一個寬頻含蓋毫米波W 頻段(75 至110 GHz)之微帶線至波導管的轉換器，通帶之介入損失必須小於1 dB，其反射損失必須大於15 dB。過 去常採用之Finline Tapers 的設計，其功能表現會受到波導管內壁之溝槽的存在而變得異常敏感且不 穩定。本計畫提出下列四種依序漸進的設計，來滿足計畫規格的要求： 1. Probe + suspended line, 2. Probe + suspended line + transition + shielded microstrip line, 3. Probe + suspended line + transition + shielded microstrip line＋microstrip line, 4. Probe + suspended line + transition + shielded microstrip line＋microstrip line + transition + GCPW line. 以有限元素法(finite element method)為基礎而發展出之商用套裝軟體Ansoft—HFSS 將用來針對 上述之3-D 結構的轉換器設計進行模擬，並且將製作及測試轉換器，來應證上述設計之模擬結果的 真確性。

Two types of extra-high frequency (W-band) 90o quadrature hybrids will be developed in this sub-program 。The first one is the metallic rectangular waveguide E-plane branch-guide quadrature hybrid. Because of the high frequency, the E-plane T-junction equivalent reactance must be precisely involved in the circuit to get proper circuit performances. The circuit will be optimized using 3-D EM simulation tools. The second one is the substrate integrated waveguide (SIW) Riblet short-slot quadrature hybrid. The SIW is a hot research topic in recent years. The SIW short-slot hybrid will be pushed to W-band frequencies in this sub-program.The above two types of circuit should be matched to the planar circuit (microstrip line) to interconnect MMIC chips. The E-plane branch-guide hybrid will be combined with the E-plane transition circuit developed in the third sub-program because both of them are E-plane circuits. The SIW hybrid itself is a planar circuit. The substrate of SIW should be the same as the substrate used in planar circuit. We intend to design in this project a sub-harmonic mixer. The incoming RF is 90-99GHz while the down-converted IF will be 9-18GHz. With two triplers, the injected 9GHz LO driving signal can be up-lifted to 81GHz and be used in the core mixing circuit. Therefore, it is eligible using silicon process to design a sub-harmonic mixer with harmonic number equal to 9 without any performance degradation. To ensure that only the signal within the select frequency range can be down-converted and detected, we also design an active 9-18GHz band-pass filter circuit. In addition to the highly developed microwave and millimeter-wave integrated circuits, the current trend on circuit miniaturization has enabled planar transmission lines, such as microstrip lines and coplanar waveguides, become the principal assembly for components and systems design. However, due to the needs for device measurements or system integration, these planar transmission lines must be converted to other types of transmission lines or waveguides. For applications at low frequencies, transitions between the microstrip lines and the coaxial SMA connectors are commonly employed. For applications at high frequencies such as millimeter-wave frequency ranges, these transitions can not function properly. A common and pragmatic approach is a design for waveguide-to-microstrip transitions. These transitions must meet the requirements of low reflection, low insertion loss, broadband nature, and stable performance. The goal of this project is to design a broadband waveguide-to-microstrip transition covering the entire millimeter-wave W-band (from 75 GHz to 110 GHz). The passband insertion loss must be less than 1 dB and the return loss must be great than 15 dB. The performance of some earlier designs using finline tapers is susceptible to the grooves on the inner walls of the waveguides. In this project, a design following four gradual steps is proposed to meet the requirements: 1. Probe + suspended line, 2. Probe + suspended line + transition + shielded microstrip line, 3. Probe + suspended line + transition + shielded microstrip line＋microstrip line, 4. Probe + suspended line + transition + shielded microstrip line＋microstrip line + transition + GCPW line. A commercial CAD tool, Ansoft—HFSS, based on the finite element method is chosen to conduct the required simulations for the proposed transitions. Prototypes of the proposed transitions will be fabricated and measured to verify the validity of the simulation results