The Germans used a passive bistatic system during World War II. For example, the British deployed the CHAIN HOME system the French used a bistatic Continuous Wave (CW) radar in a 'fence' (or 'barrier') system the Soviet Union deployed a bistatic CW system called the RUS-1, and the Japanese developed a bistatic CW radar called 'Type A'. Thus many countries were using bistatic systems in air defence networks during the early 1930s. The first radar experiments in the United Kingdom in 1935 by Robert Watson-Watt demonstrated the principle of radar by detecting a Handley Page Heyford bomber at a distance of 12 km using the BBC shortwave transmitter at Daventry.Įarly radars were all bistatic because the technology to enable an antenna to be switched from transmit to receive mode had not been developed. The concept of passive radar detection using reflected ambient radio signals emanating from a distant transmitter is not new. Well known examples include the Czech TAMARA and VERA systems and the Ukrainian Kolchuga system. However, these systems do not exploit reflected energy and hence are more accurately described as Electronic Support Measure systems. The term 'passive radar' is sometimes used incorrectly to describe those passive sensors that detect and track aircraft by their RF emissions (such as radar, communications, or transponder emissions). In some cases, multiple transmitters and/or receivers can be employed to make several independent measurements of bistatic range, Doppler and bearing and hence significantly improve the final track accuracy. These allow the location, heading and speed of the object to be calculated. In addition to the bistatic range, a passive radar will typically also measure the bistatic Doppler shift of the echo and also its direction of arrival. This allows the bistatic range of the object to be determined. Instead, the receiver uses third-party transmitters in the environment and measures the time difference of arrival between the signal arriving directly from the transmitter and the signal arriving via reflection from the object. In a passive radar system, there is no dedicated transmitter. A pulsed signal is transmitted and the time taken for the pulse to travel to the object and back allows the range of the object to be determined. 8.3 Space Debris Detection and TrackingĬonventional radar systems comprise a colocated transmitter and receiver, which usually share a common antenna to transmit and receive.4.9 Narrow band and CW illumination sources.4.8 Track association and state estimation.

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