| Satellite communication system can effectively cover the ground,sea,air and other areas.It is an effective means to provide communication for the areas where the ground communication is not served or the service is insufficient.Up to now,most of the orbiting more than 1300 communication satellites work in the L,S,VHF and other low-frequency band,and the communication capacity is very limited.In order to meet people’s growing communication needs,high throughput satellite（HTS）provides more than 20 times of the total throughput and gets more and more attention,which works in Ku,Ka,Q and uses multi-beam technology to realize frequency resource multiplexing.However,the existing HTS transponders have poor frequency flexibility,which makes it difficult to achieve arbitrary cross-band,cross-beam service data exchange.Therefore,according to the characteristics of more service users,larger signal bandwidth,higher modulation order and nonuniform channel division of HTS,this paper studies the variable rate digital channelization technology suitable for HTS to realize the flexible allocation of channel resources.The main work is as follows:Firstly,summarizing and analyzing the existing algorithms of channelizer,taking the algorithms based on the modulation filter bank as the research emphasis,and proposing a cascade structure of the modulation filter bank.The classical algorithms of perfect reconstruction and nearly perfect reconstruction filter banks are simulated and analyzed,and the results show that reconstruction error of the former is 10-1310-15,but the perfect reconstruction filter bank with a large number of channels is more difficult to design,designing nearly perfect reconstruction filter banks is convenient and fast,but reconstruction error is as high as 10-210-3.In this paper,a algorithm of designing cascade modulated filter bank is proposed,which uses lower order prototype filter to realize the filter bank to separate and reconstruct signals with high frequency precision,the reconstruction error is 10-610-7.Secondly,a channelizer is further designed based on the cascade modulated filter bank,and its effectiveness is verified by simulation.The simulation system of satellite application based on the channelizer is built and its parameters are analyzed.The performance loss of demodulation of signals with different bandwidth and modulation mode is tested to verify the performance of the channelizer.The results show that the system BER performance loss is less than 0.2 d B,the channelizer based on the cascade filter bank can perfect reconstruction QPSK,16 APSK and 256 APSK signals in DVB-S2 X and effectively restrain the power leakage of each subcarrier signal.Hence the channelizer based on the cascade filter bank can satisfy the communication requirements of HTS.Thirdly,FPGA design and implementation Based on traditional modulation filter bank channelizer are completed.Combined with the characteristics of FFT IP core serial input and output,the thesis designs an efficient channelizer implementation structure whose polyphase filtering module works in the high time clock domain and perform the filtering operations of the first M branches and the last M branches of the filter bank in sequence,and uses ping-pong RAM instead of the shift register to cache and reshape the data,reducing the occupation of chip resources.The results show that the 1024-channel channelizer is implemented on the chip xc7k410tfg900-2,which only needs 12% DSP resources and 8% LUT resources of the total resources. |
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