The system was designed for sales to the Royal Air Force and a NATO contract for mobile radars on the southern flank of Europe.
The AR-320s were to be held in off-site locations and quickly moved to pre-surveyed areas in case the main radars in the network were attacked.
This effect became known as "squint" and was generally considered annoying, especially on the AMES Type 80 where servicing the magnetron required a lengthy recalibration process to bring the beam back in line with the antenna.
[1] This effect also opened the possibility of steering the beam electronically by deliberately changing the frequency during the period of a long pulse.
To make practical use of this effect, a much wider bandwidth would be needed, which became possible with the introduction of high-power klystrons and travelling wave tubes in the later 1950s.
[2] In 1964, Decca Radar won a contract to study the use of this effect in combination with another emerging technique, pulse compression.
In follow-on work they built an experimental system known as SQUIRT which was operational in 1967, the same year Decca's Heavy Radar division was purchased by Plessey.
SQUIRT, with modifications made in 1968, demonstrated itself able to scan vertically while providing accurate range measurements, but at the cost of losing accuracy in height finding.
This allowed the transmitter to send its pulses at varying base frequencies and then delay the signal so the phase differences re-aligned the output with the antenna boresight.
The digital signals were also used for constant false alarm rate (CFAR) bucketing, Doppler analysis, and jamming detection.
Likewise, ITT-Gilfillan gained access to Plessey's proven raster-scan display systems, which at that time were still relatively new technology.
It did not become operational until 1993, by which time the Warsaw Pact had broken up and the need for the mobile backup systems was no longer pressing.
Given the now almost non-existent threat, the Type 93's were removed from their backup role and sent to bases that formerly used older equipment, notably the AN/TPS-77's, which had also proven difficult to maintain.
[8] In the late 1980s, Plessey began considering upgrades to the array antenna to replace the ITT model, producing a system known as the AR-3DP.
A series of phase delays in the serpentine handled the shifting needed to properly align the signals with the output slots depending on the base frequency.
The output from these receivers had pulse compression applied using surface acoustic wave delays to improve range resolution and was then digitized using analog-to-digital converters.
The resulting digital data was then "de-squinted", adjusting its apparent location to remove any frequency-related shift, and then fed into the target detection system.
Additionally, the MTI system was aided by further adjusting the phase delay of the lowest angle of the antenna to cancel out any net movement in the clutter, like rain.
Jammers also confuse the radar image by sending out signals that are strong enough to be picked up in the antenna side lobes, producing false returns that appear in other directions.
Planar arrays naturally have low sidelobes, typically on the order of 25 dB down from the main signal, which helps reduce this problem.