Array‐based target localisation in ATSC DTV passive radar

This work investigates the use of passive radar array‐based localisation, with a focus on experimental demonstration and practical array calibration aspects. Passive radar target localisation often employs multilateration, where a set of hyperbolic equations from range differences or elliptic equations from bistatic ranges are solved to determine the three‐dimensional (3D) target position. An alternative uses array‐based direction finding to provide an accurate measurement of target bearing, and intersects the bearing vector with a bistatic range ellipsoid to obtain a 3D target position. Continuous‐wave digitally modulated signals like digital television (DTV) provides stable power spectra and long integration times, and these support fine range and Doppler resolutions to isolate multiple targets without the association difficulties of multilateration. The Bartlett method can then be used on individual targets, giving bearing estimates of much higher accuracy than the array beamwidth. This was shown experimentally with an electrically small array yielding small angular errors in both azimuth and elevation. Using a DTV‐based passive radar, a target at 20 km receiver range was located with an accuracy of ∼250 m in a 3D position. Furthermore, a procedure for in‐situ array calibration using opportunistic air targets is reported.