The Research And Design Of Analog Predistortion

With the modern wireless communication systems developing, most of the wireless communication systems require highly linear and efficient signal transmission. However, the design of high-power amplifiers is inherently nonlinear and inefficient. Thus, they should be applied with proper linearization techniques. For example, Predistortion technique, this paper focused on the technology of Analog Predistortion.Papers at domestic and abroad had designed abundant of Analog Predistortion’s construction. Looked from the overall, the circuit configuration consists of power divider, combiner, the inter-modulation signal generator, phase shifter, attenuator, etc. Obviously, the inter-modulation signal generator is the most important module. This paper designed a Analog Predistortion which could generated 3th-orderinter-modulation(IM3) and 5th-order-intermodulation(IM5) simultaneously, Based on the principle of a pair of anti-parallel diodes produced only odd-order-inter-modulation predistortion. After tuning phase shifter and attenuator changed the input signal amplitude and phase, two signals with fundamental wave combined to be input to power amplifier.In order to design this Analog Predistrotion, This paper had compared many literatures Reported in either domestic or abroad. The proposed of improved Analog Predistortion are listed as below, in general, The Analog Predistortion only eliminates the IMD3 of power amplifier which could increased the IMD5 and influenced the linearity of power amplifier simultaneously. In addition, Memory effects may be remarkable inevitably, which could influence the Performance of power amplifier. This paper has presented a method to solve this problem partly, which adds an additional branch. This way can improve the IM5 of the Analog Predistortion’s output spectrum, and can weaken the memory effect. But this case may cause the increase of costs and the size of circuit configuration inevitably. Under this circumstance, it is important that we should guarantee the original circuit topology and simplify the topology of the circuit configuration and the number of components.This paper introduces the detail methodology of designing the Analog Predistortion, including the design and simulation of the three-way-power divider, the inter-modulation signal generator and phase shifter. Finally, the proposed circuit has been measured and obtains the final result after debugging. Measured with 2MHz two tone testing shows that the linearity of power amplifier has been improved, IMD3’s performance is improved about 8dB and IMD5 is not deteriorated.