在無線電系統中，衰減器(Attenuator)為一應用甚廣的組件，衰減器的功能，在於降低信號的振幅，以及增進電路的回饋耗損，且同時仍能正確的保持輸入及輸出阻抗，一般對衰減器之設計都以50-Ω或75-Ω 為參考特性阻抗。衰減器的結構為一阻抗性的twoport-network，且為一無方向性者。在插入電路中應用時，輸入端埠與另一端的Z?，輸出端埠與另一端的Z?，若都為阻抗匹配者，則衰減器將會提供設定的衰減值。本論文將會利用PIN Diode 來設計一寬頻電壓控制衰減器，適用於頻率介於45M Hz 至3G Hz 間的AGC 應用，並分析PIN Diode 在高頻下的阻抗變化，並研究由PIN Diode 設計出的各式RF 開關以及各式衰減器。

In a wireless communication system, Attenuator an application for a wide range of components, the attenuator function is to reduce the signal amplitude and enhance the feedback circuit depletion, and while still maintaining the correct input and output impedance, the general Attenuator on the design to all 50 - Ω or 75 - Ω impedance of the reference. Attenuator structure for the impedance of the two port-network, and for those without direction. Insert the application of the circuit, input and the other side of the port, the output port and the other end, if all the impedance matching, while Attenuator will be set up to provide the attenuation value.
This paper will use PIN Diode to design tunable active broadband attenuator, apply to the frequency between 100MHz to 3GHz and between the AGC pplications, research by the PIN Diode to design all kinds of switches and various types of RF attenuator. PIN Diode and analysis in the high-frequency impedance changes.

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