Characterization of high speed data transmission interface for future IRS payloads

Camera Electronics for remote sensing payloads having multi-sensors with different resolutions in terms of spatial, spectral and radiometric calls for large amount of data to be sent to data handling system of spacecraft in real-time. Sensors have multiple video ports to be processed with ≥12-bit digitization generating data at >12Mbps simultaneously. Conventional Parallel transmission followed in earlier missions will require large number of interface devices and cables, resulting large weight and volume. Parallel transmission will also have signal integrity issues like EMI/EMC, crosstalk data skew etc. Hence to have better signal integrity, data needs to be serialized and transmitted with minimum interfaces. This calls for high-speed transmission medium (>1Gbps) within spacecraft subsystems. It also requires to address jitter and timing margins related issues. Serdes devices are used in various serial transmission standards like PCI express, Ethernet, fiber channel, etc. They have a set of dedicated serializer and deserializer units either in a single chip for duplex data transmission or a pair of devices. Main function of Serdes is to perform parallel-to-serial conversion of data with internally generated serial clock at the transmitter end, transmission of serial stream with or without clock over a differential interface and conversion of the serial data back to parallel at the receiver end with clock. Serdes devices use CMOS technology and LVDS digital interface, which means low power consumption and high noise immunity. One such Serdes device has been identified and evaluated under application conditions of camera electronics. This device transforms 21-bit parallel data into a three LVDS differential streams with total throughput of 1.575GBPs. Evaluation of these devices is challenging w.r.t. development of high bandwidth test set up and serial data analysis. This paper discusses test setup and characterization of Serdes.