Patent ID: 6703966
Filing Date: 2004-03-09
Classification: G01S

Abstract:
A method of measuring the speed v of a moving object (100) traveling in a direction parallel to the ground (33), the measurement being made by means of a Doppler radar with transmitter (21) and receiver (22) antennae fixed to the moving object at a certain height h above the ground and designed to transmit a radar beam towards the ground along a mean axis extending forwards or backwards relative to the direction of movement, said method including the following steps:generating an electrical signal at a certain frequency by means of an oscillator (11), from said signal and possibly after amplification, transmitting an incident wave towards the ground, by means of the transmitter antenna having a wide aperture angle in a vertical plane, receiving a reflected wave, generated by reflection of the incident wave by a reflecting obstacle on the ground, by means of the receiver antenna with a wide aperture angle in the vertical plane, mixing together part of the electrical signal supplied by the oscillator and the received signal, possibly after amplification thereby generating two signals, one signal at a frequency equal to the sum and the other at a frequency equal to the difference of the two signal frequencies entering the mixer, filtering the signal from the mixer (16) to generate a filtered signal proportional to the signal at a frequency equal to the frequency difference, amplifying the filtered signal at a frequency equal to the frequency difference to generate a signal called Doppler signal and looking for the different Doppler frequencies present in the Doppler signal, at close successive instants, said method being characterized in that it further includes the following steps:identifying in each Doppler signal obtained, Doppler frequencies at close successive instants corresponding to reflecting objects on the ground located in the zone scanned by the wave transmitted by the transmitter antenna, called identified Doppler frequencies, calculating the theoretical evolution function representing the evolution as a function of time, of the Doppler frequency corresponding to a reflecting object, for a given speed, height of the transmitter and receiver antennae above the road and position of the reflecting obstacle, and selecting from the identified Doppler frequencies, those which correspond to the same reflecting obstacle at different successive instants using them to determine the speed of the moving body.