在本論文中，描述了一個3.5GHz頻段降頻器和2.5GHz LC交叉耦合振盪器設計。IC製作是使用台灣積體電路公司的0.35μm 2P4M製程。降頻器使用switching-Gm的方法來獲得比標準Gilbert Cell降頻器還高的轉換增益及較低的所需LO功率，同時分別在RF和LO輸入端內建變壓器型式BALUN來減少因使用外部BALUN產生之損耗。中頻端也使用一個簡單PMOS current mirror來產生單端輸出，避免使用外部中頻BALUN。為驗證線性度，使用OFDM QAM信號之量測結果也一并呈現作為參考。

至於LC交叉耦合振盪器，它是標準型PMOS交叉耦合對，使用了inversion模式之變容器，並使用PMOS電流源和2p旁路電容來減少電源雜訊和干擾，以期降低phase noise。

另一方面，如1.2節所敘述之OFDM系統射頻前端電路設計要點，可以對此降頻器和振盪器之性能有一個較好的了解及參考。

In this thesis, both 3.5GHz band down-conversion mixer and 2.5GHz LC-tank voltage-controlled oscillator (VCO) are described. The two chips are fabricated by using the TSMC 0.35μm 2P4M process. The mixer uses switching-Gm means to achieve the higher conversion gain and lower LO power needed than standard Gilbert Cell mixer, at the same time, with built-in RF and LO BALUN of transformer type to reduce the off-chip BALUN loss of using. The output IF is also transformed to single end port by a simple PMOS current mirror load for avoiding using IF BALUN, the results of measurement by OFDM QAM signal testing are also presented for verifying the linearity as reference.

As to the LC-tank VCO, it is standard type with cross-coupled PMOS pair, inversion-mode PMOS varactors and the using of the PMOS current source and 2pF bypass capacitor to reduce the power noise and interference so as to reach to lower phase noise.

On the other hand, with the design issues of RF front end in OFDM system as described in section 1.2, this can contribute to a better understanding and reference for the performance of both mixer and VCO.

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