應用於無線醫療遙測之互補式金氧半射頻傳送機前端電路研製

Abstract

近年醫療電子的快速發展改善了醫療看護的品質。在生理監控的應用上，已經漸漸趨向透過無線方式來傳輸以帶來較佳的舒適性與自由性。一個小面積、高效能並操作在醫用頻段的射頻傳送機需求與日俱增。西元兩千零二年美國聯邦通信委員會(FCC)為了解決無線醫療儀器干擾問題而訂出了一個無線醫療遙測服務 (Wireless Medical Telemetry Service)頻段，然而至今一直未有操作在此頻段的傳輸機前端電路被發表。 本篇論文提出一個應用於無線醫療遙測頻段1.4-GHz的傳送機前端電路，此傳送機整合了功率放大器(Power Amplifier)、正交調變器(IQ Modulator)、四相位壓控振盪器(Quadrature Voltage-Controlled Oscillator)並且使用0.18-μm CMOS技術來設計與製造。論文中提出一個功率放大器採用多赫蒂放大器(Doherty Amplifier)架構，模擬顯示放大器的功率附加效益(Power Added Efficiency)在1-dB壓縮點時有29%，而回退(Back-off) 6 dB操作仍然有15%。而正交調變器與四相位壓控振盪器分別以2.45 mW、2.26 mW之低功耗達到直接升頻的目的。量測結果顯示傳輸機可輸出功率5 dBm，整體轉換增益為20 dB，此時整體消耗功率為35 mW，整體效能可達9.04%。在1-dB壓縮點的鏡像抑制及震盪源抑制皆為20 dBc。晶片的操作電壓為1.5 V，晶片面積為2.06 mm2。 最後本論文會探討此傳送機振盪源抑制及鏡像抑制不佳的原因，並將前一個設計改成差動式架構以解決問題。新版的差動式多赫蒂放大器的功率附加效益在1-dB壓縮點時有25%，而回退(Back-off) 6 dB操作仍然有13%。重新設計後的傳送機可輸出功率8 dBm，並且有20 dB的轉換增益，此時整體消耗功率為62 mW，整體效能為10.1%。在1-dB壓縮點的鏡像抑制與震盪源抑制分別為52 dBc及51 dBc。晶片的操作電壓為1.5 V，晶片面積為2.59 mm2。第二版電路已委託國家晶片中心於台灣積體電路股份有限公司以0.18-μm CMOS技術製造。

In recent year, the rapid development of medical electronics improves the quality of medical care. For long-term bio-medical monitoring applications, using implantable or wearable wireless product makes patient more comfortable and mobile. For these applications, a low power, small area wireless transmitters are required. In June 2002, in order to solving interference problem, FCC allocated 14-MHz of radio spectrum to Wireless Medical Telemetry Services. However, no transmitter front-ends circuits using WMTS band has been published. In this thesis, the design methodology and implementation of a 1.4-GHz RF transmitter front-end for WMTS band are presented. The proposed transmitter which consists of a power amplifier, an IQ modulator and a quadrature voltage-controlled oscillator is designed in 0.18-μm CMOS technology. The proposed power amplifier uses Doherty amplifier architecture. In simulation results, the power amplifier achieves power added efficiency (PAE) of 29% at P1dB and 15% at 6 dB back-off power level. IQ modulator and QVCO with low power consumption of 2.45 mW and 2.26 mW achieve function of up-conversion. In experimental results, it consumes 35 mW under 1.5-V power supply for 5 dBm output power. The efficiency is 9.04%. The conversion gain of whole TX is 20 dB. The image rejection is 20 dBc, and LO rejection is also 20 dBc. The die area is 2.06 mm2. Finally, discussions about the reasons of degradations of LO rejection and image rejection are made. A modified differential transmitter is proposed. The modified differential Doherty PA achieves PAE of 25% at P1dB and 13% at 6 dB back-off power level. The re-designed TX achieves P1dB of 8 dBm. The conversion gain is 20 dB. The power dissipation is 62 mW under 1.5V power supply, and the efficiency is 10.1%. The image rejection and LO rejection are 52 dBc and 51 dBc, respectively. The die area is 2.59 mm2. The re-designed TX will be implemented in TSMC 0.18-μm CMOS technology.