Design, Implementation and Realization of Navigation Signal Generation Unit for IRNSS payload

摘要

Indian Regional Navigation Satellite System (IRNSS) envisages establishment of regional navigation system for first time in India which necessitate development of Navigation Signal Generation Unit (NSGU) indigenously. This paper describes the novel scheme for design and development of NSGU whose key Junction involves storing, formatting and processing of bulk uplink Navigation (NAV) data to prepare base band signal for modulators. Processing includes Forward Error Correction (FEC) encoding of formatted NAV data to produce symbols which are further interleaved and supplied for spreading with codes. Generation of spread codes target standard positioning service (SPS) and restricted service (RS). RS code has an optional Encryption scheme. Spreading of interleaved NAV data symbols with SPS code and RS code generates Navigation signal. The simulation and hardware results of Design Verification Module (DVM) confirm data coherency and code coherency for NAV data and spread codes which are necessary for satisfactory performance of system. Time setting onboard with accuracy of nanoseconds which is achieved by setting of Zcount is most crucial and innovative part of the design which will help in achieving position accuracy < 20m on ground. Development of NSGU will lead ISRO in to new era of Navigation services and applications.