The Research Of Broadband Class-E Amplifiers Based On Supply Modulators

With the rapid development of modern wireless communication technology, the bandwidth, and peak to average power ratio(PAPR) of signals are increasing continuously, which makes the traditional transmitter architecture hard to meet the efficiency and bandwidth requirements of communication facilities. New high-efficiency transmitter architectures are widely applied and studied, such as Envelope Tracking(ET), Envelope Elimination and Restoration(EER), Polar and Doherty Transmitters. Based on these backgrounds, this paper mainly focuses on broadband and high-efficiency Class-E power amplifiers and envelope amplifiers which can be applied in ET, EER, and Polar transmitters, improve their bandwidth and efficiency. The contents of this paper can be summarized as follows:1. Through the researches of Class-E power amplifiers and broadband matching theories, a 6-order Chebyshev low-pass filter is considered as the matching network of a ClassE power amplifier to expand the bandwidth. Through experiments, this Class-E power amplifier is measured with the drain efficiency of 72% to 87% and the output power of higher than 40 d Bm in the frequency range from 1.6GHz to 2.7GHz.2. The relation between drain supply voltages and drain direct-current impedances of Class-E power amplifiers affected by transistor’s nonlinear capacitance is analyzed. The broadband envelope impedance of Class-E power amplifier is defined, envelope impedance model applied ET transmitters by using memory. Polynomials. It is concluded that the envelope impedances of a Class-E power amplifier are of memory and nonlinearity through the AM-AM curves of envelope impedance vs. voltage and the final model parameters. At last, It is obtained that the relation between the envelope amplifier’s average efficiency and the probability distribution of envelope impedances, The model of envelope impedances are used to optimize the average efficiency of an envelope amplifier.3. The state of art methods of broadband envelope amplifier are introduced, and an improved envelope amplifier structure of a Class-E inverter and a Class-E rectifier(Class-E~2) is proposed. The switching frequency of the Class-E~2 envelope amplifier with gate pulse modulation can be increased to offer broadband envelope amplification, and the structure is also simplified. At last, the measured results listed as follows: switching frequency is 1.75 GHz, envelope bandwidth is more than 20 MHz, the maximal frequency of △∑ modulation is 200 MHz and the highefficiency back-off voltage range is more than 6dB.