项目来源

香港研究资助局基金(RGC)

项目主持人

Prof Ki, Wing Hung

项目受资助机构

The Hong Kong University of Science and Technology

立项年度

2012

立项时间

未公开

项目编号

613512

项目级别

省级

研究期限

未知 / 未知

受资助金额

700000.00港币

学科

Electrical&Electronic Engineering

学科代码

未公开

基金类别

General Research Fund

关键词

未公开

参与者

未公开

参与机构

未公开

项目标书摘要：在无线通信中，射频(RF)功率放大器通常工作在A类或AB类模式，以保证调制精度。对於A类的RF功率放大器，偏置电流和电源电压保持恒定，其效率与输出功率成正比。对於B类的RF功率放大器，电源电压保持恒定，而偏置电流则与输出的RF电流成正比。因此，对於A类RF放大器而言，其效率随着输出功率/输出功率(最大值)(Pout/Pout(max))的降低而降低，而对於B类RF放大器而言，其效率随着(Pout/Pout(max))^½ 的降低而降低。AB类RF放大器的效率在这两者之间。然而如果电源电压可以随着输出功率动态变化，则功率放大器的效率可以大大提高。
        现有设计表明，动态电源电压控制可以将功率放大器的损耗降低两倍以上。但是爲了同时满足RF功率放大器的高效率和高线性度要求，我们通常需要一个高效率宽频带的电源调制器。线性稳压器和开关转换器都可用於电源调制。当输出电压较低时，线性稳压器的效率非常差。而效率较高的开关变换器则很难实现三倍于信号带宽的环路带宽。许多现有的动态电源供电设计只适用于窄带应用，比如信号带宽在100kHz到几MHz的EDGE,CDMA和WCDMA的信号。新兴的4G高数据速率，如LTE或WiMAX,采用先进的OFDM调制方案，此调制方案的基带信号的带宽可高达20 MHz,其PAR(峰值和平均值比)则在10至12dB之间。
        我们建议研究和设计具有动态电压控制功能的高效率宽频带电源调制器。电源调制器的带宽应该高达20MHz,与此同时工作效率接近或超过90%。为了同时实现高效率和宽频带，线性辅助开关转换器将是一个很好的选项。在此架构中，高效率的开关转换器可以提供低频和中频范围内的大部分功率，而线性稳压器(可以是一个低压差稳压器)则提供高频范围内的功率。现有的设计采用滞环控制模式或电压模式控制。在这项研究中，我们提出探索新的控制方法，例如，线性辅助开关转换器的电流模式控制。

Application Abstract: In wireless communications,RF power amplifiers are usually operated in the Class-A or Class-AB mode in order to preserve modulation accuracy.For a Class-A RF power amplifier,the DC current and voltage are kept constant,and its efficiency is proportional to the output power.For a Class-B RF power amplifier,the supply voltage is kept constant while the DC current is proportional to the output RF current.Thus,for a Class-A RF amplifier,the efficiency decreases in proportion to P_out/P_out(max),while for a Class-B RF amplifier,the efficiency decreases in proportion to(P_out/P_out(max))^1/2.The efficiency of a Class-AB RF amplifier lies in between these values,and can be improved greatly if the supply voltage changes dynamically in accordance with the output power.
        Some existing designs showed that the loss of power amplifiers can be reduced by two times or more by dynamic supply voltage control.However,a high-efficiency wideband supply modulator is needed to achieve both high efficiency and high linearity for the RF power amplifier.Both linear regulators and switching converters could be used for supply modulation.The efficiency of a linear regulator is very poor when the output voltage is low,while a switching converter is very difficult to achieve a loop bandwidth three times of the signal bandwidth.Many of the existing dynamic supply biasing designs are restricted to narrowband applications such as EDGE,CDMA,and WCDMA whose signal bandwidth is of the order of 100 kHz or a few MHz.For emerging 4G high data rate applications such as LTE or WiMAX,the baseband signal bandwidth is as high as 20 MHz and the PAR(peak-to-average ratio)is about 10 to 12dB for the advanced OFDM modulation scheme.
        We propose to study and design high-efficiency wideband supply modulators with dynamic supply voltage control.The bandwidth of the supply modulator should be as high as 20MHz with efficiency near or over 90%.To achieve both high efficiency and wide bandwidth,a linear-assisted switching converter would be a good candidate.In this architecture,the switching converter is used to supply most of the power confined within the low to medium frequency range,while the linear regulator(may be a low dropout regulator)supplies power for the high frequency range.Existing designs either employ hysteretic-mode control or voltage-mode control.In this research,we propose to explore new control methods,for example,linear-assisted switching converters with current-mode control.