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Frequency Modulated Continuous Wave (FMCW) Radio Detection and Ranging Principle

The FMCW Radio Detection and Ranging principle has been developed over many years to accurately measure targets at relatively short distances. The transmitter section generates a radio signal that is linearly swept over the 8.9 to 10.1 GHz frequency range. This signal is beamed by the aerial/antenna towards the target or material where it is reflected back towards the sensor's receiver.

The receiver mixes a sample of the transmitted signal with the received signal. The receiver output is a low frequency, linearly dependent on the target distance. This 'beat' frequency is generated by the Doppler effect and is stable and predictable.

The Doppler beat frequency is amplified, filtered and then digitised by an Analogue-to-Digital converter (A2D). The following Digital Signal Processor (DSP) performs a frequency analysis of the received signal to determine the target distance and strength.

The output of this Fast-Fourier Transform (FFT) process is then passed to the post-processing algorithms to identify the correct target, which is the contents of the container or process level. The target-finding algorithms have been developed and optimised by Pulsar over many years experience to reliably identify and track process levels for liquids, sludges, powders and solids.

FMCW Radar Technology is used by Pulsar's Nemesis for non-contacting level measurement.