應用於封包追蹤功率放大器之CMOS電壓供應調變器

Abstract

近年來行動通訊裝置相當地普及，例如:智慧型手機、平板電腦，這些行動通訊裝置皆是以電池為供電來源，所以電池的使用時間是使用者相當在意的特性。行動通訊裝置中的射頻發射機，功率放大器消耗了大部分射頻發射機的功率，如果功率放大器無法有效率地使用功率，那整體射頻放大機的效率將會大打折扣。 為了有效提升功率放大器的效率，運用動態供給電壓技巧的封包追蹤技術是方法之一。不同於一般使用固定供給電壓的方式，封包追蹤技術利用電壓供應調變器可根據封包的變化情形動態地改變供給到功率放大器的電壓。 本論文設計的電壓供應調變器主要包含兩個部分，第一個部分是提供低頻訊號的切換式直流對直流轉換器，第二個部分是提供高頻訊號的線性放大器。應用於封包追蹤技術的電壓供應調變器除了需要有高頻寬外，高迴轉率也是要求之一，若線性放大器頻寬既要寬，迴轉率也要高的話，消耗的功率可能會較大，故本論文額外使用了提高迴轉率的電路，在需要高迴轉率之時，此電路能額外提供充電或放電的路徑，藉此以降低線性放大器的功率消耗。 本論文使用有橫向擴散金屬氧化物半導體的0.13 微米互補式金屬氧化物半導體製程實現，晶片面積為1.72*1.28 mm2。追蹤的訊號為1/5/10/15/20 MHz 之弦波及20 MHz LTE 之封包訊號，可操作的輸出電壓範圍為0.5 ~3.6 V，可達到的效率為77.3 %。

Nowadays, handheld devices are very popular, such as smartphone and Tablet.Because the handset devices use battery as the power source, customers are concerned about the battery life. Power amplifiers consume a significant portion of the total power of the RF Transmitters of the handheld devices. If power amplifiers can’t use power efficiently, the overall efficiency of RF Transmitters will become very poor. Envelope tracking is one of the techniques to improve the efficiency of the power amplifiers. Unlike a fixed-supply-voltage power amplifier, envelope tracking is a technique which the supply voltage of the power amplifier is dynamically adjusted by the supply modulator to track the envelope of the RF signal. In this thesis, the supply modulator includes two parts. One is the switching DC-DC converter which provides low frequency content of the envelope waveform, and the other is the linear amplifier which provides high frequency content of the envelope waveform. The supply modulator applied to envelope tracking not only has high bandwidth, but also has high slew rate. If we request the linear amplifier has both high bandwidth and high slew rate, it will consume a lot of power. This thesis proposes the circuits which can improve the slew rate of the linear amplifier. When needing high slew rate, the circuits can provide another charging or discharging path. With the method, the linear amplifier can reduce the power consumption. The chip is fabricated in a 0.13 μm CMOS with LDMOS process, and its size is 1.72*1.28 mm^2. The tracking signals are 1/5/10/15/20 MHz sine wave and 20 MHz LTE envelope. The output voltage range and the efficiency are 0.5~3.6 V and 77.3 %, respectively.