Eliminate The Influence Of Switching Power Supply For CDMA Based On Adaptive Algorithms

With the rapid development of electronic information technology, the important role of powermanagement system is becoming more and more obvious. Power management system is essential tocommunication systems. Switching power supply has the characteristics of small volume, light weight,low consumption, high efficiency. The rapid development of switching power supply technologymakes its’ frequency higher, but the larger noise problems caused by higher frequency restrict theapplication in the field of RF. At present, the adaptive denoising algorithm is relatively mature, hasbeen widely used in the field of image processing, medical monitoring. To eliminate the switchingfrequency impact on RF system becomes an important direction.This paper describes the advantages and disadvantages of switching power supply and linearregulator. It research the principle of adaptive noise cancellation, the structure of adaptive notch filter,and the LMS algorithm. CDMA communication system model is established by simulink. Differentfrequency sine signals instead of switching frequency impact on CDMA receiver baseband signal.Using adaptive algorithm eliminates this noise. BER and EVM entry is an important indicator ofmeasuring algorithm. Single frequency sinusoidal disturbance signal amplitude was changed in thesimulation. We observed BER and EVM entry values. Its’ value have a greater degree of decline aftereliminating noise. This effectively illustrates the validity and rationality of the algorithm.In the aspect of hardware implementation, DC-DC was set up with TL494. CDMA receiver wasset up with RF2903. Switching frequency pin was connected to the receiver baseband. RF VSG sendthe modulated signal to the receiver. Receiver outputs IQ baseband signal. FPGA which was writedwith LMS algorithm processed digital signals outputed by low pass filter and ADC0809. Theprocessed data was exported by signaltap. We get EVM and BER with matlab analysis.Through adaptive filter, BER can be decreased from7×10-4to2.7×10-6. This design caneffectively eliminate the switching frequency impact on CDMA receiver. This method provides thebasis for switching power supply in the field of RF, has a good application prospect.