Millimeter-wave Power Amplifier Linearization Techniques

In modern communication system, the application of various modulation technologies in order to improve the spectrum efficiency requires high linearity of the RF transceiver. The transceiver system must achieve high output power and high linearity simultaneously. And the power amplifier is one of the devices that have seriously nonlinear distortion in the RF transceiver; therefore, the linearization technology of power amplifier has become the key component to resolving this problem.With the frequency resources becoming more and more nervous in recent years, millimeter-wave technology as a high-tech field develops rapidly. Therefore, the research of this paper for the linearization of MMW power amplifier has an important significance for improving the RF transceiver linearity and promoting the development of millimeter-wave technology.In this paper, based on the full study of the characteristics and nonlinear distortion problems of the MMW PA, we propose two schemes: one is the RF pre-distortion linearizer using a diode; the other is the nonlinear negative feedback program.For the RF pre-distortion linearizer, the circuit architecture we presented is used a GaAs Schottky diode with a bias feed resistance and a parallel capacitor. This linearizer has gain expansion and phase shift characteristics, and its characteristics can be controlled; especially for its phase characteristic, it has stronger adjustability. By applying this linearizer to a 30GHz-band power amplifier which has 10 watt output power at 1dB compression point, both of the simulation results and experimental results show that: the novel pre-distortion linearizer can effectively improve the IMD3 of Ka-band PA, thus enhancing the linearity of millimeter-wave transceiver. This linearizer has simple structure, and it's adjustable, low cost and easy to be fabricated. Therefore, it is valuable for engineering application.As for the non-linear negative feedback program, it is mainly composed of the main amplifier and nonlinear feedback loop, and it has adaptive performance. In engineering applications, the actual work situation of the amplifier is complex, the performance of the linearizer need to be altered often. Therefore, the adaptive linearizer is an important research direction. In this paper, we completed an analysis of its working principle, circuit design and simulation. The simulation results show that: this method has adaptive features; in the X-band and following band, the amplifier's linearity can be improved more or litter, but it's difficult to apply to the millimeter wave band. Therefore, the non-linear negative feedback program is of great significance to develop the adaptive linearizer.