Increasing measuring precision for FMCW radar - uses auxiliary signal to mix again with differential mixing signal from transmit and reception signals

摘要

The measuring precision of an FMCW radar for location of reflection in optical fibres (LWL) is increased by forming differential frequency of a mixing signal (fM) from transmit and reception signal. The mixed signal is mixed again with a triggered auxiliary signal (fH) with tunable frequency. One of the side bands, generated by the mixing, is spectrally analysed. In addition the instantaneous value of the auxiliary signal frequency is used also for signal evaluation. The evaluation interval in the spectral analysis is linked with a rigid phase to the ramp signal (fR), used for the control of the transmit signal frequency. ADVANTAGE - Facility for forming integral ratio of mixing signal frequency to ramp frequency for each reflection.