Antenna Back-Lobe Rejection

• US 20090051584A1
• Filed: 11/26/2004
• Published: 02/26/2009
• Est. Priority Date: 11/26/2004
• Status: Active Grant

• Current Assignee: Saab AB
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Hellsten, Hans
• Granted Patent: US 7,876,256 B2
• Time in Patent Office: Days
• US Class Current: 342/25.A
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 13/9054 Stripmap mode
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling

Abstract

A method of for processing signals in a radar system is shown comprising an antenna system having at least two antenna elements, a beam forming arrangement (ABF_RX, ABF_TX) for selectively steering the directivity of the antenna system in a given selected direction, the directivity of the antenna system having a main lobe in the selected direction and a back lobe (BL) in another direction and of a lower magnitude than the main lobe. By utilizing various scale and subtract processing both noise levels and ghost signals can be considerably reduced. A SAR radar apparatus has moreover been shown.

Claims

1. Method of processing signals in a radar system comprising an antenna system having at least two antenna elements, a beam forming arrangement for selectively steering the directivity of the antenna system in a given selected direction, the directivity of the antenna system having a main lobe in the selected direction and a back lobe in a differing direction, and a first scale and subtract unit, the method comprising

transmitting a first transmit signal by selectively steering the antenna in a first direction,

sampling a first response signal by steering the antenna in a second direction,

sampling a second response signal be steering the antenna in the first direction,

subtracting the first response signal from the second response signal, thereby forming a sample value corresponding to properties mainly in the first direction.

2. Method of processing signals in a radar system according to claim 1, the method moreover comprising

transmitting a second transmit signal, by selectively steering the antenna in the second direction,

sampling a third response signal by steering the antenna in a second direction,

sampling a fourth response signal by steering the antenna in the first direction,

subtracting the fourth response signal from the third response signal, thereby forming a sample value corresponding to properties mainly in the second direction.

3. Method according to claim 2, wherein the radar system moreover comprises a memory bank and a synthetic beam forming unit for storing data for a channel corresponding to each selected direction according to predefined Doppler bins and a second scale and subtract unit for each respective channel,

the method comprising

forming a first Doppler value corresponding to the first sampled value,

from the first direction for a given Doppler bin,

forming a first scaled value of the Doppler value with a scaling value,

forming a second Doppler value corresponding to the second sampled value from the second direction and for the same given Doppler bin,

forming a second scaled value of the Doppler value with a second scaling value,

assessing a first response signal for a direction corresponding to the given the given Doppler bin and for the first selected direction by subtracting the second scaled value from the first Doppler value, and

assessing a second response signal for a direction corresponding to the given the given Doppler bin and for the second selected direction by extracting the first scaled value from the second Doppler value.

13. The method according to claim 1, wherein transmitting a first transmit signal includes omnidirectional transmitting in at least a part of a given frequency range from the antenna elements.

14. The method according to claim 2, wherein transmitting a first transmit signal includes omnidirectional transmitting in at least a part of a given frequency range from the antenna elements.

15. The method according to claim 3, wherein transmitting a first transmit signal includes omnidirectional transmitting in at least a part of a given frequency range from the antenna elements.

16. The method according to claim 13, wherein sampling a first response signal includes sampling with bar antennas mounted parallel at a predefined distance.

17. The method according to claim 1, wherein sampling a first response signal includes sampling with bar antennas mounted parallel at a predefined distance.

18. The method according to claim 2, wherein sampling a first response signal includes sampling with bar antennas mounted parallel at a predefined distance.

19. The method according to claim 3, wherein sampling a first response signal includes sampling with bar antennas mounted parallel at a predefined distance.

4. Method of processing signals in a radar system comprising

an antenna system having at least two antenna elements, a beam forming arrangement for selectively steering the directivity of the antenna system in a given selected direction, the directivity of the antenna system having a main lobe in the selected direction and a back lobe (BL) in a differing direction, and a first scale and subtract unit, wherein the radar system moreover comprises a memory bank and a synthetic beam forming unit for storing data for a channel corresponding to each selected direction according to predefined Doppler bins and a scale and subtract unit for each respective channel,

the method comprising

transmitting a first transmit signal, by selectively steering the antenna in a first direction,

sampling a first response signal by steering the antenna in the first direction,

transmitting a second transmit signal, by selectively steering the antenna in a second direction,

sampling a second response signal by steering the antenna in the second direction,

forming a first Doppler value corresponding to the first sampled response signal from the first direction for a given Doppler bin,

forming a first scaled value of the Doppler value with a scaling value,

forming a second Doppler value corresponding to the second sampled response signal from the second direction and for the same given Doppler bin,

forming a second scaled value of the Doppler value with a second scaling value,

assessing a first response signal for a direction corresponding to the given the given Doppler bin and for the first selected direction by subtracting the second scaled value from the first Doppler value, and

assessing a second response signal for a direction corresponding to the given the given Doppler bin and for the second selected direction by extracting the first scaled value from the second Doppler value.

5. Method according to claim 4, wherein the antenna elements are omnidirectional in at least a part of a given frequency range.

6. Method according to claim 5, wherein the radar system is a synthetic aperture radar system.

7. Method according to claim 5, wherein the antennas are bar antennas mounted parallel at a predefined distance.

8. Radar system comprising:

a first and second antenna,

an arbitrary signal generator,

an additive beam forming transmit unit for steering the directional capability of the antenna system to a given side,

an additive beam forming receive unit for steering the directional capability of the antenna system to a given side, and

a first scaling and subtraction unit in which signal contributions stemming from diverse measurement directions of the radar system but the same transmit direction are subtracted from another.

9. Radar apparatus according to claim 8, further comprising a memory bank and a synthetic beam forming unit for storing data for a channel corresponding to each selected direction according to predefined Doppler bins and a second scale and subtract unit for each respective channel.

11. Radar apparatus according to claim 8, comprising a SAR image generation unit.

12. A radar apparatus according to claim 9, comprising a SAR image generation unit.

10. Radar system comprising:

a first and second antenna,

an arbitrary signal generator,

an additive beam forming transmit unit for steering the directional capability of the antenna system to a given side,

an additive beam forming receive unit for steering the directional capability of the antenna system to a given side, and

a memory bank,

a synthetic beam forming unit for storing data for a channel corresponding to each selected direction according to predefined Doppler bins, and

a scale and subtract unit for each respective channel in which signal contributions stemming from diverse directions of the radar system are scaled and subtracted from one another so as to compensate for back lobe signals.