Ionospheric clutter modelling for VHF passive radars operating at high latitudes

Passive VHF and UHF radars which prosecute FM and television broadcasts above 50 MHz at latitudes greater than 40 degrees will occasionally be subject to large amounts clutter from the ionosphere. Conventional pulsed, active radars can mitigate against auroral clutter by appropriate gating of the transmtter waveforms and receiver samples. However, passive radars, as CW systems cannot. In this report we describe the basic features of meter scale ionospheric clutter, describe how its magnitude can be estimated, and how its effects may be mitigated.