應用於鎖相迴路內電流幫浦之不匹配電流校正技術

Charge Pump Mismatch Current Calibration Techniques for Phase-Locked Loop

章泰順(Tai-Shun Chang)

指導教授 ： 林宗賢

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.02054

摘要

爲了準確的定義輸出頻率，以鎖相迴路為基礎的頻率合成器經常被使用於收發器的本地震盪器裡。在整數型的鎖相迴路裡，由電流幫浦的不匹配所引起的突波會降低整個無線收發器的效能。當接收器降轉信號的時候，鄰近的頻帶則會被突波給污染。在非整數型鎖相迴路裡，電流幫浦的不匹配電流所導致的非線性效應會破壞三角積分調變器的雜訊延展的效果，而由三角積分調變器所引入的量化誤差則會回饋至低頻而影響到訊號對雜訊比。
在本設計中，實現了一個運用了三角積分調變的非整數型鎖相迴路並加上了電流幫浦校正機制的電路。所提出的電流幫浦校正技術有兩個模式，在整數型模式，校正技術可以降低電流幫浦的不匹配電流並在模擬中減低參考突波6 dB。而在三角積分非整數鎖相迴路中，電流幫浦的不匹配電流則可以被壓低至兩個百分比之內。量測的能量消耗在1.8V的電壓供應之下，整數型的鎖相迴路不匹配電流校正花了20毫瓦，而非整數的鎖相迴路不匹配電流校正花了23毫瓦。

關鍵字

不匹配電流 ； 鎖相迴路

並列摘要

To accurately define the oscillator frequency, phase locked loop (PLL) based frequency synthesizers are usually used in local oscillator. In an integer-N type frequency synthesizer, the output spurious tones caused by charge pump up/down current mismatch will degrade the performance of a wireless receiver. The adjacent channels may be corrupted when receiver down-convert the RF signal. In a ΔΣ fractional-N type PLL, the non-linearity of charge pump may degrade the quality of noise shaping, and therefore the modulated quantization noise will be folded back to lower frequency; hence the low-frequency in-band signal-to-noise ratio is worse.
In this work, a ΔΣ fractional-N PLL with charge pump current calibration scheme is presented. The proposed charge pump current calibration technique has two modes. In integer mode, the calibration technique can reduce the charge pump up/down mismatch current and lower reference spurs by 6 dB in simulation. The up/down mismatch current is reduced to less than 2% in the fractional-N mode. The measured power consumption with 1.8V power supply in the integer mode is about 20 mW and is 23mW in the fractional-N mode.

並列關鍵字

mismatch current calibration ； phase locked loop

參考文獻

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