Performance limitations of active cancellers for FMCW radars

Active cancellers have long been proposed to alleviate the problem of strong nearby reflections that can saturate the front-end of the receiver in an FMCW radar. In this paper the general properties and the problem of setting an active canceller to work are discussed and the dynamic range improvement that can be achieved when an active canceller using modern MMIC components is added to an existing radar is determined. It is found that the long range detection performance and dynamic range of a radar is always degraded with the addition of an active canceller and that the attainable improvement in dynamic range for nearby targets is minimal. Taking into account the complexity and subtleties of active cancellers, the addition of an active canceller should be carefully considered. Time and money may well be better spent by increasing the dynamic range of the receiver front end instead.