應用於無線通訊之可自動調整頻寬轉導電容濾波器

A Gm-C Filter with Automatic Frequency Tuning for Wireless Communication Applications

陳威志(Wei-Chi Chen)

指導教授 ： 柏振球

國立清華大學/電機資訊學院/電機工程學系/碩士(2006年)

摘要

在本篇論文中，我們提出了一個低失真的轉導放大器，我們利用了一些技巧：1. 電流再使用 2. 增益推進 3. 線性區域操作金屬氧化物半導體的電晶體; 因此，我們可以得到一個電壓與電流轉換的高線性度關係。我們利用所提出的轉導放大器來組成一個適用於無線通訊應用的六階轉導電容濾波器。此外，可藉由調整轉導放大器的轉導值來調整此轉導電容濾波器的頻寬。利用此特性我們可以克服由於晶片製程變異所產生的頻寬變異。我們亦設計了一個在晶片上的可自動調整濾波器頻寬系統用來自動補償頻寬的變異。因為在可自動調整頻寬系統中大多使用了數位的電路，所以可自動調整頻寬系統的功率損耗以及面積便可大為降低。除此之外，我們利用所設計的轉導放大器組成了一個四階的低雜訊巴特渥斯低通濾波器，此濾波器則是適用於低雜訊的應用。
為了驗證我們的設計，採用了TSMC 0.18 μm CMOS的製程製作了兩個實驗晶片。在電源供應為1.8 V之下，經過量測後，第一個晶片的 -3 dB 截止頻率為 8 MHz，直流增益為 0.056 dB，當輸入訊號頻率是 1 MHz 且大小為1.2 Vppd時，其 THD 小於 -40 dB，而IIP3則為 10 dBV，濾波器以及可自動調整頻寬系統的功率消耗分別為8.1 mW及 3.53 mW。可自動調整頻寬系統的調整誤差則小於 5 %之內。第二個晶片的 -3 dB 截止頻率則約為 11.5 MHz，直流增益為 -0.614 dB，當輸入訊號頻率是 1 MHz 且大小為1.1 Vppd時，其 THD 為 0.96 %，而IIP3則為 8 dBV，濾波器的功率消耗為13.3 mW，雜訊約為 40.7 nV/rt Hz。

關鍵字

轉導電容濾波器

並列摘要

In this thesis, we propose an operational transconductance amplifier (OTA) with low distortion by using some techniques: (a) current reusing (b) gain-boosting (c) MOS triode region operation. Therefore, a high linear relationship between input voltage and output current can be obtained. We use the proposed OTA to implement a sixth-order Gm-C filter for wireless communication applications. Moreover, the bandwidth of the Gm-C filter can be tuned by tuning the transconductance of the OTA. By using this property, we can overcome the bandwidth variation of the filter due to the process variation. An on-chip automatic frequency tuning system is also designed to compensate the bandwidth variation automatically. The power consumption and the active area of the automatic-tuning system are reduced by the lots usage of the digital circuits in the automatic-tuning system. Besides, a low noise fourth-order Butterworth filter implemented with the proposed OTA is also designed for low noise application.
In order to verify this design, two test chips are fabricated with TSMC 0.18 μm CMOS process. The power supply is 1.8 V. The measurement results of the first chip show that the -3dB frequency is about 8 MHz and the DC gain is 0.056 dB. The total harmonic distortion (THD) is smaller than -40 dB when the input signal is a 1 MHz sinusoidal waveform with 1.2 Vppd amplitude. The input third intercept point (IIP3) is 10 dBV, and the power consumption of the filter and the automatic-tuning circuit are 8.1 mW and 3.53 mW, respectively. The tuning error of the automatic frequency tuning system is less than 5 %. The measurement results of the second chip show that the -3dB frequency is about 11.5 MHz and the DC gain is -0.61 dB. The THD is 0.96 % with 1.1 Vppd input signal at 1 MHz. The IIP3 is 8 dBV, and the power consumption is 13.3 mW. The noise level is 40.7 nV/rt Hz.

並列關鍵字

A Gm-C Filter with Automatic Frequency Tuning

參考文獻

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