Digital Up And Down Converter Module Design In Multi-mode Access Device

With the rapid development of the network integration,terminal equipment,access equipment and core switching equipment gradually converging.Fusion in access equipment plays an important role in the network integration.Multi-mode access equipment is the key of integration for Heterogeneous Wireless Development.As an important part of multi-mode access device,frequency conversion system designing determines the efficiency of data processing system.This thesis takes this aspect as the research object.In view of the existing LTE base station digital up and down conversion function implementation,there are problems such as high resource consumption,poor filtering spectrum performance and so on,a FDD-LTE digital zero-IF frequency conversion system based on multirate filter banks is designed,which using the optimized CIC filter,HB filter and FIR filter composed of hybrid rate conversion unit.CIC filter and HB filter is used to complete rate conversion task with low resource consumption.At the same time,the FIR filter with good filtering performance is working under the low sampling rate.By this method,the balance between performance of the output signal and system resource consumption is achieved.According to the simulation results,compared with the existing multiple frequency conversion schemes,this system achieve a compromise between system resource consumption and signal spectral characteristics.In view of the existing analog direct frequency conversion method of WLAN converter system,there are objection such as high requirements of signal characteristic and inconvenience of integration with existing digital platform,a digital frequency conversion system which based on digital zero-IF conversion technology is designed in 5G WLAN system.By virtue of its low resource consumption characteristics,HB interpolation and decimation filter is used as the rate conversion unit.With the advantages of CIC Compensation filter's pass-band edge Compensation features,CIC compensation filter is introduced to optimize the flatness on the edge of the passband.According to the simulation results,compared with traditional analog frequency conversion system,the system can achieve better spectral characteristics,noise factor,transform gain performance at a lower system requirements.