Researches Of Perfect Reconstruction Based Digital Channelization With Sub-band Regeneration

As an important payload in satellite communication systems,a digital channelizer can realize the spaceborne exchange processing of multiband composite signals, and it isalso paid a lot of attention in the field of mobile satellite communication. On the spaceborne transponder, it is required not only to deal with the data of different users from the uplink channel diversely, exchanging them to the designated downlink frequencies, but also to regenerate some of sub-band signals withouttheeffect on other signals at the same time. Because of its good characteristics of spectrum segmentation and signal reconstruction, the complex modulated filter banks technology is utilized in the digital channelization and reconstruction techniques. In the digital channelization technique, the above requirements can be satisfied by integrating the advantages of regenerative and non-regenerative transponders, with the improvement of the exchange performance, the reduction of the implement complexity, the enhancement of processing efficiency, and the decrease of sub-band aliasing distortion.In view of the complicated design of available prototype filter and the poor performance of sub-band regeneration, the digital channelization and reconstruction technique for spaceborne signal processing is investigated primarily in this thesis. Meanwhile, a design scheme of the digital channelize system is proposed. The main contents and achievement of this thesis are summarized as follow:1. The complex modulated filter-banks structure used for accurate reconstruction is studied and analyzed. As the most simple filter bank,two-channel filter bank takes advantage of lattice structure to achieve perfect reconstruction.Then, the structure of multi-channel filter banks can be obtained through theextension of this structure. And that the power complement characteristics of polyphase components in twice oversampling complex modulated filter banks on the basis of the non-destructive characteristics of lattice structure.2. Based on the lossless lattice structure of two-channels, aorder-by-order and channel-by-channel designed method is proposed for prototype filter. According to the design ideas of decomposition, a prototype filter is decomposed into a plurality of two-channel filter polyphase components. The power complementary lattice polyphase components can ensure the perfect reconstruction characteristics of the whole filter banks. And at the same time, the design process is transformed into solving an unconstrained quadratic optimization question, which reduces the number of coefficients in each optimization and the complexity.3. A digital channelization system is established, based on the complex modulated filter banks for perfect reconstruction and the polyphase decomposition technology. The processing of many sub-band signals is realized, including the extraction, exchange, separation of sub-band signals and broadcast, multicast. And that it is also suitable for non-uniform bandwidth switching cases. In addition, the perfect reconstruction effect of system signals and the decrease degree of frequency-band overlapping are analyzed in detail.4. A digital channelize structure for regenerating parted sub-band signals is designed. According to the system practicalrequirements, the digital channelization technology is used to separate an incoming wideband mixed signal into many narrowband signals, and to extract and regeneratesomedesired sub-band signals. Due to differentbandwidths of the regenerated signals, those signals are demodulated to recover the initial data bits from two cases of single and multiple channels, which don’t damage other sub-band signals withthe perfect reconstruction.