Advanced High Speed Parallel Frame Synchronizer for High Data Rate Indian Remote Sensing Satellite Series

摘要

The Video data from remote sensing satellite is transmitted serially frame after frame. To mark the beginning of video data a known unique code is embedded at the beginning of the video data frame. This is known as Frame Synchronizer code. Pseudo-Noise sequences are chosen as frame synchronizer codes as they are easy to generate, detect and have auto correlation property. Generally, for all Indian Remote sensing satellite series 127 bits Pseudo-Noise sequence is chosen as frame synchronizer code. On-board the satellite, the video data buffering is in serial fashion and for appropriate processing it is required to be formatted in data packets. Hence, data formatting is done onboard the satellite and then the Pulse Coded Modulated data is transmitted to ground station. The previous Indian Remote Sensing Satellites series has data rate of 105 Mbps. The Present data rate of Radar imaging satellite-1 (RISAT-1) is 640MBps. In order to accommodate such high data rates in the limited bandwidths, the video data is transmitted in Right hand Circular Polarization (RHCP) and Left Hand Circular Polarization (LHCP). The QPSK modulation is used for video data transmission. Hence at such high data rates an advanced high speed frame synchronizer is required to cater to such high data rates. The advanced parallel processing technique of frame synchronism, detection and monitoring is unique as it doubles the operating frequency of the Frame synchronizer. Also with the same hardware, the frequency response of the hardware circuit can be doubled. If the maximum operating frequency is 'f' Hz then using Advanced Parallel Frame synchronizer technique, the operating frequency response is doubled to '2f' Hz using the same hardware chip. In this paper Advanced frame synchronizer circuit is been implemented and is put to use to archive video data from Indian Radar Imaging Satellite-1.