Apparatus and method for attenuating close-range radar signals with balancing for dual-frequency difference in radar signals in an automotive radar sensor
A radar signal transmitter transmits first and second radar signals at different first and second frequencies. A radar receiver receives reflected radar signals and generates receive signals indicative of the reflected radar signals. A first receive signal is indicative of a first reflected radar signal generated by reflection of the first transmitted radar signal, and a second receive signal is indicative of a second reflected radar signal generated by reflection of the second transmitted radar signal. A processor receives the first and second receive signals and computes a difference between the first and second receive signals to generate a difference signal. The processor processes the difference signal to provide radar information for the region, the processor adjusting at least one of amplitude and phase of at least one of the first and second receive signals such that the difference is optimized at a preselected range from the receiver.
1. A radar system, comprising:
a radar signal transmitter for transmitting transmitted radar signals into a region, a first transmitted radar signal having a first frequency and a second transmitted radar signal having a second frequency different from the first frequency;
a receiver for receiving reflected radar signals generated by reflection of the transmitted radar signals and generating receive signals indicative of the reflected radar signals, a first receive signal being indicative of a first reflected radar signal generated by reflection of the first transmitted radar signal, and a second receive signal being indicative of a second reflected radar signal generated by reflection of the second transmitted radar signal; and
a processor configured to: (a) receive the first and second receive signals, (b) compute a difference between the first and second receive signals to generate a difference signal, (c) process the difference signal to provide radar information for the region, and adjust at least one of amplitude and phase of at least one of the first and second receive signals such that the difference is optimized at a preselected range from the receiver.
2. The radar system of claim 1 , wherein the processor adjusts at least one of amplitude and phase of at least one of the first and second receive signals using a minimization process.
3. The radar system of claim 2 , wherein the minimization process is an iterative minimization process.
4. The radar system of claim 2 , wherein the minimization process comprises a functional fit approach.
5. The radar system of claim 2 , wherein the minimization process comprises a steepest descent approach.
6. The radar system of claim 2 , wherein the minimization process comprises a multiple-hypothesis approach.
7. The radar system of claim 1 , wherein a difference between the first frequency and the second frequency is selected such that the information related to close-range objects in the region is attenuated in the difference signal.
8. The radar system of claim 1 , wherein a difference between the first frequency and the second frequency is selected such that a phase difference between the first and second reflected radar signals is such that information related to close-range objects in the region is attenuated in the difference signal.
9. The radar system of claim 1 , wherein the first frequency is approximately 24.2 GHz.
10. The radar system of claim 1 , wherein a difference between the first frequency and the second frequency is approximately 11 MHz.
11. The radar system of claim 1 , wherein the transmitted radar signals are pulse radar signals.
12. The radar system of claim 11 , wherein a pulse of the pulse radar signals has a duration of approximately 120 nsec.
13. The radar system of claim 1 , wherein the radar system is configured to be mounted in and operate in a vehicle.
14. The radar system of claim 13 , wherein a difference between the first frequency and the second frequency is selected such that information related to close-range objects in the region is attenuated in the difference signal.
15. The radar system of claim 14 , wherein the close-range objects in the region include a bumper fascia of an automobile in which the radar system is disposed.
16. The radar system of claim 13 , wherein a difference between the first frequency and the second frequency is selected such that a phase difference between the first and second reflected radar signals is such that information related to close-range objects in the region is attenuated in the difference signal.
17. A radar processing method, comprising:
transmitting radar signals into a region, a first transmitted radar signal having a first frequency and a second transmitted radar signal having a second frequency different from the first frequency;
receiving reflected radar signals generated by reflection of the transmitted radar signals and generating receive signals indicative of the reflected radar signals, a first receive signal being indicative of a first reflected radar signal generated by reflection of the first transmitted radar signal, and a second receive signal being indicative of a second reflected radar signal generated by reflection of the second transmitted radar signal; and
processing the first and second receive signals, said processing comprising: (a) receiving the first and second receive signals, (b) computing a difference between the first and second receive signals to generate a difference signal, (c) processing the difference signal to provide radar information for the region, and adjusting at least one of amplitude and phase of at least one of the first and second receive signals such that the difference is optimized at a preselected range from the receiver.
18. The method of claim 17 , wherein adjusting at least one of amplitude and phase of at least one of the first and second receive signals uses a minimization process.
19. The method of claim 18 , wherein the minimization process is an iterative minimization process.
20. The method of claim 18 , wherein the minimization process comprises a functional fit approach.
21. The method of claim 18 , wherein the minimization process comprises a steepest descent approach.
22. The method of claim 18 , wherein the minimization process comprises a multiple-hypothesis approach.
23. The method of claim 17 , wherein a difference between the first frequency and the second frequency is selected such that the information related to close-range objects in the region is attenuated in the difference signal.
24. The method of claim 17 , wherein a difference between the first frequency and the second frequency is selected such that a phase difference between the first and second reflected radar signals is such that information related to close-range objects in the region is attenuated in the difference signal.
25. The method of claim 17 , wherein the first frequency is approximately 24.2 GHz.
26. The method of claim 17 , wherein a difference between the first frequency and the second frequency is approximately 11 MHz.
27. The method of claim 17 , wherein the transmitted radar signals are pulse radar signals.
28. The method of claim 27 , wherein a pulse of the pulse radar signals has a duration of approximately 120 nsec.
29. The method of claim 17 , wherein the method is carried out in a radar system configured to be mounted in and operate in a vehicle.
30. The method of claim 29 , wherein a difference between the first frequency and the second frequency is selected such that information related to close-range objects in the region is attenuated in the difference signal.
31. The method of claim 30 , wherein the close-range objects in the region include a bumper fascia of the vehicle.
32. The method of claim 29 , wherein a difference between the first frequency and the second frequency is selected such that a phase difference between the first and second reflected radar signals is such that information related to close-range objects in the region is attenuated in the difference signal.