Firdell Radar Reflectors Ltd — Technical Description

Blipper Range of Radar Detection Reflectors
All Blippers are based on the Optimised Phase Modulating Helical Array. The optimisation successfully deals with the technical problems associated with detection by radar reflection. To be detected the reflector and the illuminating radar must behave as a system. The first problem to overcome is the in built signal discriminating circuitry of the radar set. All radar sets have hardwired and software filters that are designed to reduce nuisance target displays. Real targets (things that you need to know about) have a particular radar response characteristic; they tend to be very spiky. The spiky nature of a real target is the result of it possessing many reflecting centres. Radar sets are tuned to recognise this type of response. This has of course not gone unnoticed by the military, stealth ships have there reflecting centres reduced to a minimum. The Firdell Blipper’s Optimised Helical Array is designed to have many reflecting centres of varying magnitude thereby replicating a real target response. The next killer of Radar Detection Reflector performance is multi path illumination. The radar energy that falls on a radar reflector is in the form of a wave. These waves will arrive at the reflector by direct and indirect paths some will have been reflected off the sea surface. Because the waves will have travelled different distances waves may not be in phase. The resultant combination of direct and indirect waves will result in complete cancellation of any return, if the waves are out of phase, and a doubling of the return signal if they are in phase. Doubling the return has no practical value as once the signal is over the threshold of detection there is no gain in detectability. However, no return is bad news. Reflectors with few reflecting centres presented to the illuminating radar can be invisible. The radar set will disregard the signal as it will look like clutter due to its return characteristic. The Firdell Blipper has many reflecting centres distributed around 360degrees of azimuth. This effectively makes the Blipper immune to Multi Path signal cancellation as when one reflecting centre is out of phase others are in phase.

Blipper Range of Radar Detection Reflectors

All Blippers are based on the Optimised Phase Modulating Helical Array. The optimisation successfully deals with the technical problems associated with detection by radar reflection.

To be detected the reflector and the illuminating radar must behave as a system. The first problem to overcome is the in built signal discriminating circuitry of the radar set. All radar sets have hardwired and software filters that are designed to reduce nuisance target displays. Real targets (things that you need to know about) have a particular radar response characteristic; they tend to be very spiky. The spiky nature of a real target is the result of it possessing many reflecting centres. Radar sets are tuned to recognise this type of response. This has of course not gone unnoticed by the military, stealth ships have there reflecting centres reduced to a minimum.

The Firdell Blipper’s Optimised Helical Array is designed to have many reflecting centres of varying magnitude thereby replicating a real target response.

The next killer of Radar Detection Reflector performance is multi path illumination. The radar energy that falls on a radar reflector is in the form of a wave. These waves will arrive at the reflector by direct and indirect paths some will have been reflected off the sea surface. Because the waves will have travelled different distances waves may not be in phase. The resultant combination of direct and indirect waves will result in complete cancellation of any return, if the waves are out of phase, and a doubling of the return signal if they are in phase.

Doubling the return has no practical value as once the signal is over the threshold of detection there is no gain in detectability. However, no return is bad news. Reflectors with few reflecting centres presented to the illuminating radar can be invisible. The radar set will disregard the signal as it will look like clutter due to its return characteristic.

The Firdell Blipper has many reflecting centres distributed around 360degrees of azimuth. This effectively makes the Blipper immune to Multi Path signal cancellation as when one reflecting centre is out of phase others are in phase.