Millimeter-wave Predistortion Technology Research

In order to carry high speed data flow within the limited bandwidth, some efficient modulation technology have be used in the millimeter wave radio communication system such as OFDM and 64 QAM.In the practical application of those efficient modulation technique, the voltage of multicarrier often lead to a high peak-to-average ratio(PAR), it makes the traditional millimeter wave power amplifiers work in saturated workspace. Once the millimeter wave power amplifier work in saturated workspace, it can produce strong nonlinear distortion, which causes the signal distortion and out-of-band interference. It severely restricts the performance of millimeter wave radio communication system. Linearization technology is to improve the power amplifier nonlinear distortion, predistortion technology is one of the main linearization technologies in millimeter wave band. With the development of millimeter-wave wireless communication system,the research of millimeter wave power amplifier linearization technology become more and more important.In this paper, we use the vector superposition principle to proposes a analog predistortion techniques for millimeter wave solid state power amplifiers(SSPAs) and travelling wave tube amplifiers(TWTAs).We use tandem Schottky diode and parallel Schottky diode to design the predistortion linearization. The experimental results show that the predistortion linearization can produce good predistortion signals for SSPAs and TWTAs.Based on the theoretical analysis of the characteristics of the parallel Schottky diode, we propose a multistage tandem predistortion linearization method. Using this method we designed a predistortion linearizer for SSPAs and another predistortion linearizer for TWTAs. The test results show that the performance of the predistortion linearizer is excellent. On this basis, we developed a Ka-band predistortion driver amplifier for SSPAs. The test results show that the predistortion driver amplifier can provide 1.1dB to 4.1dB gain amplitude expansion and 34 ° to 10 ° gain phase compression nonlinear compensation. Dual tone test results show that the predistortion driver amplifier can improved the IMD3 by 19 dB at –7dB IBO in 29.6GHz to 30 GHz frequency band.This article uses the principle of vector superposition design predistortion linearization. It has an important contribution to the research of millimeter wave power amplifier linearization theory. The multistage tandem structure predistortion linearization we developed is easy to be integrated and has good performance and broadband characteristics. The Ka-band predistortion driver amplifier makes the predistortion linearization integrated in the amplifier module, it is of great significance.