Because I can't resist talking about this, one of my hobby topics, a bit more, there's a whole history of radar development occurring in Canada in the early cold war. The DEW line is of major interest because of the huge complexity of building such an ambitious project so far north. Also interesting, though, is the Mid-Canada Line which was built before, and further south than, the DEW line. The MCL pioneered the bistatic radar technology which was used (in a much refined form) in the DEW line.
The principle of bistatic radar is this: instead of the transmitter and receiver being at the same position, and thus receiving reflections (this is known as monostatic radar), in a bistatic system the transmitter and receiver are at different locations and detect changes in the signal propagating between them. In the case of the MCL and DEW line, the change observed for is dopplar shift caused by a moving object in the area in between. The use of bistatic radar means that the MCL and DEW line are very literally "lines" with each station transmitting to the next.
To overcome limitations of bistatic radar, though, the DEW line made use of both. The AN/FPS-19 search radar was a monostatic system. However, monostatic radar often has poor sensitivity to aircraft at low altitude (thus the expression "under the radar"). The AN/FPS-23 bistatic radar was used to "fill in" sensitivity at low altitude, although an aircraft would have to pass between two stations (and thus be further south) to be detected.
An interesting example of bistatic radar that makes for easy learning of the concept because of its small scale is the AN/TPS-39 (one of a number of radars called "tipsies" due to the req number), which was used as a "virtual fence" for surface security at Titan missile silos. In that case the two antennas were only something like 10-20 feet apart and had a distinctive horn shape due to using microwave frequencies. Microwave radar is still used in "virtual fence" intrusion detection applications but enhancements in signal processing technology now allow simpler monostatic applications.
The principle of bistatic radar is this: instead of the transmitter and receiver being at the same position, and thus receiving reflections (this is known as monostatic radar), in a bistatic system the transmitter and receiver are at different locations and detect changes in the signal propagating between them. In the case of the MCL and DEW line, the change observed for is dopplar shift caused by a moving object in the area in between. The use of bistatic radar means that the MCL and DEW line are very literally "lines" with each station transmitting to the next.
To overcome limitations of bistatic radar, though, the DEW line made use of both. The AN/FPS-19 search radar was a monostatic system. However, monostatic radar often has poor sensitivity to aircraft at low altitude (thus the expression "under the radar"). The AN/FPS-23 bistatic radar was used to "fill in" sensitivity at low altitude, although an aircraft would have to pass between two stations (and thus be further south) to be detected.
An interesting example of bistatic radar that makes for easy learning of the concept because of its small scale is the AN/TPS-39 (one of a number of radars called "tipsies" due to the req number), which was used as a "virtual fence" for surface security at Titan missile silos. In that case the two antennas were only something like 10-20 feet apart and had a distinctive horn shape due to using microwave frequencies. Microwave radar is still used in "virtual fence" intrusion detection applications but enhancements in signal processing technology now allow simpler monostatic applications.