Ka-Band Regenerative Transponder for GSAT-4 Satellite
- Paper number
IAC-07-B2.3.01
- Author
Dr. K.S. Dasgupta, Space Applications Centre (SAC), ISRO, India
- Coauthor
S.B. Sharma, Indian Space Research Organisation (ISRO), India
- Coauthor
- Coauthor
Dr. S B Sharma, India
- Coauthor
Dr. K.S. Dasgupta, Space Applications Centre (SAC), ISRO, India
- Year
2007
- Abstract
This paper describes in brief the Ka-band Regenerative transponder for the forth coming GSAT-4 satellite which is being designed and developed at Space Applications Centre, Indian Space Research Organisation – ISRO. Design issues, technological challenges for shaped multi beam antenna, high speed digital base band systems – Multicarrier, Wideband Demodulator, base band processor, receivers and transmitters are also discussed in this paper. GSAT-4 satellite is being designed to cater for high bandwidth requirement using Ka-band multiple spot beams with frequency reuse and onboard signal regeneration cum switching. There is a rapid rise of business communications using VSATs (Very Small Aperture Terminals), with inherent small link margins. The other areas of rapidly growing interest are mobile communications and navigation applications. For these specialized business services or mobile communication with large number of individual users, the earth stations must be small in size and weight and cost less. This transponder is being designed to address above mentioned needs. GSAT-4 satellites with 8 spot beams will have high transponder G/T and EIRP and double the frequency band utilization by incorporating frequency reuse. The satellite will also have on-board signal processing and signal and beam switching facility, which shall enable the use of small size terminals to operate in mesh network. Thus, it will be possible to configure network for various applications with both bent-pipe and regenerative transponders with small size terminals in mesh connectivity. The design and development of a shaped multiple beam antenna has been carried out at Ka-band. This generates eight contiguous beams, all of different shapes to cover the Indian landmass. The typical coverage requirement for each beam, as visible from geostationary orbital slot of 820 E is 0.426 m-sterad. A subset of four frequency bands from the available spectrum is optimally allocated amongst the beams with a two-fold frequency reuse. The Multicarrier demodulators and wideband demodulators use extensive digital Signal processing techniques for carrier acquisition, data demodulation, mapping of FDMA signal to TDM signal. These subsystems are implemented on Xilinx FPGA, Space qualified ASICs. The burst demodulator is realized using space qualified Digital Signal Processor. The experiments planned under GSAT-4 should be relevant in the current information technology era where we need to develop an information infrastructure which is the fusion of satellite based communication services and ground based wired and wireless network. These applications need wide bandwidth and simple VSAT terminals for point-to-point or point-to-multipoint connectivity. The proposed Ka-band transponder will provide both narrow and wide bandwidth VSAT to VSAT connectivity. The applications envisaged for this payload are i) Communication support for Disaster Management System, ii) Grid computing, iii) Tele health care services, iv) Village information system, v) Mobile Natural Resource Information System (NRIS), vi) National Natural Resource Management System (NNRMS) and National Spatial Data Infrastructure (NSDI) applications. This paper proposes to discuss some of the innovative design techniques which are used in realisation of this payload.
- Abstract document
- Manuscript document
IAC-07-B2.3.01.pdf (🔒 authorized access only).
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