Thermal Characterisation of the PRETTY Software-Defined Radio's Receiving Channels

The main payload of the PRETTY satellite is for passive reflectometry. For this purpose, a Software-Defined Radio receiver with two receive channels and a custom-built two patch antenna to correlate the direct GPS signals and the reflected signal from Earth are used. A thorough characterisation of the receive channels is of utmost importance to identify the sources of error, especially the temperature influence. In particular, the amplitude of the digital output signal and the phase shift between the two input receive channels are characterised over the operating temperature range. A conversion of the measurement points at discrete steps in temperature, internal LNA gain and sampling rate into dedicated formulas for continuous representation of the measured values is presented in the paper.