Passive moving object detection system and method using signals transmitted by a mobile telephone station

1. A passive method of detecting an object, the method comprising receiving at a receiver a first signal transmitted by a mobile phone base station, receiving at the receiver a second signal comprising the first signal transmitted by a mobile phone base station after it has been reflected off an object; and comparing the first and second signals to derive data relating to position or speed of movement of the object; the method further comprising providing a plurality of mobile phone base stations which transmit a signal, such that as the object moves out of range of one base station, it comes into range for another, whereby the distance of the object from a base station being used to determine a position of the object remains substantially constant and distance of the object from the receiver changes, thereby improving the received power and range.

2. A method according to claim 1 , the method further comprising a time delay between receiving the first and second signals, by performing a cross correlation of the signal from the first antenna with the signal from the second antenna; determining the speed of the target using the Doppler effect; storing results from successive cross correlations, and calculating the change in relative phase between the signal from the first antenna and the second antenna at the delay of interest.

3. A method according to claim 2 , wherein the change in relative phase is calculated by means of a Discrete Fourier Transform (DFT) or Fast Fourier Transform (FFT).

4. A passive detection system, the system comprising a receiver having first and second antennas; and processing means; wherein the first antenna is adapted to receive a signal transmitted by a mobile telephone base station; wherein the second antenna is adapted to receive the signal transmitted by the mobile telephone base station after the signal has been reflected off an object and wherein the processing means compares the signal received from the mobile telephone base station with the signal reflected from the object and derives speed or position information relating to the object therefrom; wherein the object is a moving object; and the system further comprises a plurality of mobile phone base stations which transmit a signal, such that as the object moves out of range of one base station, it comes into range for another, whereby the distance of the object from a base station being used to determine a position of the object remains substantially constant and distance of the object from the receiver changes, thereby improving the received power and range.