High Data Rate X-Band Transmitter for Low Earth Orbit Satellites

Abstract

Main purpose of this study is to design a transmitter with data rates up to 100 Mbps, having QPSK/OQPSK modulation and 7 W (38.5 dBm) output power at 8.2 GHz. This output power satisfies the link budget for a low earth orbit (LEO) satellite at 700 km, utilizing required source-channel coding schemes in baseband for a BER performance of 10^-6. The modulation scheme of the transmitter can be selected as BPSK, QPSK or OQPSK. In addition to QPSK/OQPSK modulation scheme choice, the transmitter will have three different data rates, 50 Mbps and 100 Mbps which will be chosen according to the needs and facilities of the ground station. As error correction coding (ECC) scheme, a nested structure that is recommended by CCSDS is chosen which combines powerful parts of the subcodes. As the outer code, Reed Solomon with (255,223,33)₂₅₆ is used for error correction for burst errors due to multipath fading. As inner code, a convolutional code with rate (1/2) is utilized, which provides correction for random errors in the channel with a moderate bandwidth expansion. Between inner and outer codes, convolutional interleaver with depth 5 is used.