Method for creating a least one virtual reception channel using a radar antenna and radar system
A method for creating a virtual reception channel in a radar system includes an antenna possessing two physical reception channels ( 1 r , 2 r ) spaced apart by a distance d in a direction x, two emission channels ( 1 e , 2 e ) spaced apart by the same distance d in the same direction x and processing means, the method comprising: dynamically selecting two different waveforms, the waveforms being orthogonal to each other; generating a radar pulse of given central wavelength in each emission channel, each of the emission channels emitting one of the two different waveforms; acquiring with the reception channels echoes due to pulses emitted by the emission channels and reflected by at least one target; compressing the pulses by matched filtering of the echoes acquired by each physical reception channel, this involving correlating them with each of the waveforms generated in the emission channel; and repeating steps a) to c) while randomly changing one of the values of each of the phase codes associated with the generated waveforms until the level of the sidelobes of all the compressed pulses has stabilized; and radar system for implementing such a method.
1. A method for creating a virtual reception channel in a radar system comprising an antenna possessing two physical reception channels ( 1 r , 2 r ) spaced apart by a distance d in a direction x, two emission channels ( 1 e , 2 e ) spaced apart by the same distance d in the same direction x and processing means, the method comprising:
a. selecting two different waveforms containing random noise taking the form of a random succession or code of phase values, said waveforms being orthogonal to each other;
b. generating a radar pulse of given central wavelength in each emission channel, each of the emission channels emitting one of said two different waveforms;
c. acquiring with the reception channels echoes due to pulses emitted by the emission channels and reflected by at least one target;
d. compressing the pulses by matched filtering of the echoes acquired by each physical reception channel, this involving correlating them with each of the waveforms generated in the emission channels; and
e. repeating steps a) to c) while randomly changing one of the values of each of the phase codes associated with the generated waveforms until the level of the sidelobes of all the compressed pulses has stabilized.
2. The method for creating a virtual reception channel according to claim 1 , wherein the random code of the phase of the waveforms is binary.
3. The method for creating a virtual reception channel according to claim 1 , wherein the random code of the phase of the waveforms may take at least 3 values.
4. The method for creating a virtual reception channel according to claim 1 , wherein Doppler or post-integration processing is carried out along the axis of recurrences while changing the phase codes so as to decrease the level of their sidelobes.
5. The method for creating a virtual reception channel according to claim 1 , wherein the level of the sidelobes of the compressed pulses is optimized by Wiener filtering.
6. A radar system for implementing a method for creating a virtual reception channel comprising an antenna possessing two physical reception channels ( 1 r , 2 r ) spaced apart by a distance d in a direction x, two emission channels ( 1 e , 2 e ) spaced apart by the same distance d in the same direction x and processing means, wherein said radar system is configured so that, in each emission channel, radio pulses of given central wavelength are generated, each of the emission channels emitting different waveforms containing random noise taking the form of a random succession or code of phase values, said waveforms being orthogonal to the waveforms of the pulses emitted by the other emission channel, the processing means being suitable for compressing by matched filtering the pulses of echoes acquired by each physical reception channel, this involving correlating them with each of the waveforms generated in the emission channels, each of the emission channels furthermore being configured to randomly change one of the values of each of the phase codes associated with the generated waveforms until the level of the sidelobes of all the compressed pulses has stabilized.
7. The radar system according to claim 6 , wherein the emission and reception channels are co-localized.
8. The radar system according to claim 6 , wherein each of the emission channels comprises a waveform generator (GFO- 1 , GFO- 2 ) that generates the orthogonal waveforms, a mixer that mixes a signal delivered by a local oscillator and a signal delivered by the waveform generator, and an amplifier that amplifies the signal delivered by the mixer, the amplified signal allowing radar pulses to be emitted by the antenna via a circulator allowing the antenna to operate in emission and reception, and each of the n reception channels comprises an amplifier that amplifies the signal received by the reception channel, a mixer that mixes a signal delivered by a local oscillator and the signal delivered by the amplifier of the reception channel, and an amplitude-phase demodulator/analogue-digital converter (DAP/CAN) that allows the processing means to digitally compress the pulses by matched filtering.