QPSK X-Band Transmitter

The aim of the X-Band transmitter is to provide a QPSK modulated downlink signal operating in the EESS band (8025 to 8400 MHz) for LEO satellite application. The X-band Transmitter consists of two fully cross-redundant units each including: An X-Band oscillator, a QPSK modulator, and a final power amplifier of 4 W nominal RF output power.

The two oscillator modules are operating at center frequencies that are separated by 130 MHz to reduce ACI (Adjacent Channel Interference). The operating frequencies of the two oscillator modules are respectively 8120 MHz and 8250 MHz. The QPSK modulator accepts a digital video signal consisting of two I, Q data streams differentially coded with a nominal data-rate of 75 Mbps each for a total of 150 Mbps per channel.

Each unit consists of one oscillator, a QPSK modulator and a final power amplifier that can be switched on-off independently from the other. When both units are turned on, the equipment can handle an overall data stream of up to 300 Mbps.