The Hybrid Power Modulation Applied To The RF Power Amplifier In3G Mobile Phone

RF power amplifier (Radio Frequency Power Amplifier, RF PA) is the maximum powerconsumption of the devices in the mobile phones today. With the coming of3G and4G era, morecomplex functions of mobile phones and portable devices also need longer standby time, thereforeincreasingly high performance requirements for RF PA is an inevitable trend. The polar transmittercan be obtian high efficiency by using efficient nonlinear RF PA, and it’s one of the methods that aregaining popularity in modern wireless transceiver systems.This paper researches a method to optimize a combined class-AB line amplifier and switchingamplifier for polar transmitter. The switching amplifier is to present an architecture of the digitalDC-DC control, and the digital DC-DC can be used alone as a working condition for a low-frequencyinput signal in order to improve efficiency. In the analog circuit portion, a wideband, low outputimpedance class-AB is designed; and on-chip feed-forward bandpass filter is used to extend thebandwidth, without the need to increase switching frequency; Ring oscillator constituted byprogrammable delay cells can adjuste the oscillation frequency according to the digital control.An digital controller for dc–dc switch mode power supplies (SMPS) used in portable applicationsis introduced. When working alone， the controller has very low power consumption, fast dynamicresponse, and can operate at programmable constant switching frequencies exceeding10MHz. Toachieve these characteristics, a digital pulse-width modulator based on second-order sigma–deltaconcept (Σ-Δ DPWM), mulit-clocking mode compensator are combined. To minimize powerconsumption, the controller is clocked at a different frequency in different mode. When it works withclass-AB，the system of polar transmitter has good performance.At the transistor level, feed-forward bandpass filter, oscillator and class-AB are implemented; allthe modules of digital DC-DC are done with RTL level. System design with100MHz GBW,successful tracking of a10MHz sine wave signal is demonstrated; switching frequency of digitalDC-DC can be adjusted to meet the regulation of the different modes of the system, in order to savepower consumption.