一個一伏特2.4-GHz之改良型兩階式金氧半導體射頻發射器

Abstract

本篇論文主旨在設計一個改良型兩階式2.4GHz金氧半導體射頻發射器，此設計除了具有直接昇頻式射頻發射器小面積的優點外，更具有間接昇頻式沒有LO-pulling困擾的特性。這是一個應用於Bluetooth規格之射頻發射器。這個晶片是使用一標準點25微米1P5M 補式金氧半導體製程，包含了正交相位調變器、四相壓控振盪器及功率放大器。因應低電壓低功率的產品趨勢，此晶片之工作電壓設計為一伏特。此發射器晶片在一伏特工作電壓下，只消耗52.8毫安培的電流，且整體面積只佔1.8 x 1.8 毫米平方。實驗晶片完全整合在標準的0.25微米單層多晶矽五層金屬及低阻值基體之互補式金氧半的製程上。由於使用四相正交調變器及四相正交相位輸出之電壓控制振盪器，量測到的本地振盪漏損量、影像拒斥比、二階及三階的失真分別為-37.5分貝載波、-30.4分貝載波、-41.0分貝載波和-50.3分貝載波。且由於雜訊干擾的抑制設計，其最大雜訊為-38.5分貝毫瓦。針對短距離無線通訊應用，此晶片亦整合了功率放大器，由於四相壓控振盪器之螺旋形電感有著較低的品質因數以及Deep N-well電晶體的寄生電容效應，此功率放大器輸出功率為-11分貝毫瓦。經過模擬和實驗證實，本論文中所研發的電路將可應用於一個高整合度、全互補式金氧半製程的無線通訊統之中。如此將可以實現一個低價格、小體積的行動通訊裝備。在未來將針對其他的射頻元件做進一步整合，而成為一個完整的收發器。

A 2.4-GHz transmitter with improved two-step architecture combines the advantages of the direct-conversion transmitter and the two-step transmitter. No LO-pulling and small size are the main features of this transmitter, and it is designed for Bluetooth applications. This proposed chip is fabricated in a standard 0.25μm single-poly-five-metal CMOS process, and it consists of a quadrature modulator, a quadrature VCO, and a power amplifier. For the product trend of low power & low voltage, the transmitter is designed for 1 Voltage power supply. The transmitter chip drains only 52.8mA from a 1 V power supply voltage, and the chip size only 1.8mm x 1.8mm. With the quadrature modulator and VCO structure, the measured LO leakage, image rejection, second-order distortion and third-order distortion of the modulated signal at the output of transmitter achieve –37.5dBc, -30.4dBc, -41.0dBc, and –50.3dBc, respectively, and the out of band maximum emission is –38.5dBm. The power amplifier is also integrated for short-range wireless communications. The output power is only -11dBm because of the loss coming from the lower quality factor of the VCO’s spiral inductor and the parasitical capacitor of the deep N-well NMOS. It is believed that the proposed high performance RF transmitter front-end circuits can be applied to an all-CMOS wireless communication system. Thus low-cost small-size mobile equipment can be implemented. Further research on the integration of other transceiver components will be conducted in the future.