Millimeter-Wave Power Amplifier Linearization Techniques Research

With the development of wireless communication technology,spectrum resources become increasingly precious. Some linear modulation technique such as complex multi-carrier digital modulation mode is widely used. So linearity of wireless communication system is becoming more and more important. power amplifier is an important part of a wireless communication system, nonlinear characteristics of PA is the primary factors influencing the system linearity. However, to output a larger power, power amplifier are often need to work in close to the saturated state, which lead to a obvious distortion of PA. In order to guarantee the power amplifier can have high output power and linearity at the same time, a series of linearization techniques are put forward, such as Predistortion, Feedback, and Feedforward. Amongst all, Predistortion technique has simple structure, low cost, applicable to wide bandwidth, high stability, easy to load the front-end amplifier system, so we choose it as the main research object.At first, this paper carries out theoretical analysis of the nonlinear characteristics of power amplifier, analyze and compare the mainstream linearization technology. Than We emphatically introduced and analyzed several common analog predistortion circuit. Finally, based on the traditional parallel diode predistortion circuit, we developed a new type of analog predistortion circuit. The new type of nalog predistortion circuit could work for solid state power amplifier at different frequency bands of millimeter wave and microwave with the stability of the small signal gain and the predistortion also could adjust the compression range of phase without influence of The expansion of the gain range.We made a predistortion of the structure working in Ku band. The test results show that the it can provide 3dB magnitude expansion and 14~42° adjustable phase expansion at 13.75 GHz to 14.5 GHz.On the basis of the predistortion circuit, selecting the appropriate driver amplifier and adjustable attenuator, we have developed the Ku band predistortion linearization driver module for a solid-state power amplifier working in the 13.75 GHz to 14.5 GH. Two-tone test results signify that the linearization power driver module can improved the IMD3 by 5dB in 13.75~14.5 GHz.