Airport surface vehicle identification system and method

An airport surface vehicle detection and identification system, comprising:

• a ground surveillance radar comprising (i) a transmitter which multiplexes a pulsed electromagnetic waveform having a carrier frequency value f.sub.c and an interrogation waveform having a carrier frequency value f.sub.1 and transmits the resultant multiplexed electromagnetic signal, and (ii) a receiver including a radar receiver and a beacon receiver wherein said radar receiver detects backscattered electromagnetic energy at carrier frequency f.sub.c indicative of the range of the vehicle, and said beacon receiver detects a bandshifted reply signal and processes said bandshifted reply 'signal to determine the identity of the source of said bandshifted reply signal;
• and
• a frequency translator having a first channel which includes an RF receiver for receiving said interrogation waveform and provides a received interrogation signal to a mixer which bandshifts said received interrogation signal to a carrier frequency f.sub.t compatible with the vehicle transponder and provides a bandshifted interrogation signal to an antenna which radiates said bandshifted interrogation signal to the vehicle transponder, and second channel which includes a second RF receiver which receives a reply signal from the vehicle transponder and provides a received reply signal to a mixer which bandshifts the received reply signal to a carrier signal value f.sub.1 compatible with the ground surveillance radar and provides a bandshifted reply signal to an antenna which radiates said bandshifted reply signal to the ground surveillance radar.

A bi-directional frequency translator for interfacing a ground surveillance radar and a vehicle mounted transponder, comprising

• means for receiving-an interrogation signal having a carrier frequency signal value f.sub.1 from the ground surveillance radar;
• means for bandshifting said interrogation signal to a frequency value f.sub.t compatible with the vehicle mounted transponder and for providing a bandshifted interrogation signal;
• means for transmitting said bandshifted interrogation signal;
• means for receiving a reply signal from the vehicle mounted transponder, means for bandshifting the reply signal to a carrier frequency signal value f.sub.1 which is compatible with the ground surveillance radar system and for providing a bandshifted reply signal indicative thereof;
• and
• means for transmitting said bandshifted reply signal to the ground surveillance radar.

A method of determining the position and identity of a vehicle equipped with a transponder operating on the surface of an airport, using a frequency translator to condition interrogation signals from a ground surveillance radar to the transponder and also to condition a reply signal from the vehicle transponder, comprising the steps of:

• transmitting an interrogation signal from the ground surveillance radar system;
• receiving said interrogation signal at the frequency translator;
• bandshifting the received interrogation signal to a carrier signal frequency value f.sub.t compatible with the operational frequency spectrum of the transponder and providing a bandshifted interrogation signal;
• and
• transmitting said bandshifted interrogation signal from the frequency translator to the transponder.