Characterization of Satellite Frequency Up-converters

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  • Author: M. Naseef, R. MiniHold
Frequency converters which use one or more mixers are fundamental for any communication- or electronic ranging system to down-convert an RF signal to IF or baseband or to up-convert a baseband or IF signal to RF. They include filters, normally selective band pass filters, to get rid of strong adjacent channel signals, local oscillator feed-through, image responses and other mixing products. For not to degrade transmission quality of a communication system these filters must have well -controlled amplitude, phase and group-delay responses. Especially phase- and group-delay linearity is essential for low bit error rates of communication systems or high target resolution for radar systems. In order to characterize a frequency converter, a key characteristic is the relative and/or absolute group delay. In addition intermodulation products (3rd order), phase noise, 1dB compression point, conversion gain and spurious outputs are also interesting parameters to consider for measurement. Relative phase and group delay can be measured using the so-called reference or golden mixer technique, as long as the local oscillator is accessible. However, due to increasing integration and miniaturization often neither the local oscillator (LO) nor a common reference frequency signal is accessible.