Self-calibrating a radar altimeter based on a simulated return signal

• US 7,705,773 B2
• Filed: 12/19/2005
• Issued: 04/27/2010
• Est. Priority Date: 12/19/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Vacanti, David C.
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US11/306,183
• Publication Number:
  US 20070139261A1
• Time in Patent Office: 1,590 Days
• Field of Search: 342/169
• US Class Current: 342/169
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 7/35 Details of non-pulse systems
• CPC Class Codes: G01S 7/4056 specially adapted to FMCW

Abstract

Systems and methods for performing self calibration of a radar altimeter. An example system includes a first component that generates a simulated return signal based on one or more range values. A transmitter generates a transmission radar signal and a receiver processes the simulated return signal based on the transmission radar signal. A second component determines one or more calibration factors based on the processed simulated return signal and ideal return signal characteristics. The transmission radar signal is a fixed frequency signal and the first component includes a programmable frequency divider that creates at least on sideband of a known signal. A third component determines if the radar system is in at least one of a calibration mode or normal mode of operation. If the radar system is determined to be in a normal mode of operation, a fourth component applies the determined calibration factors to actual radar return signals.

Claims

1. A method for self-calibrating a radar system, the method comprising:

providing a radar system comprising a Frequency Modulated Continuous Wave (FMCW) radar altimeter system that comprises a receiver for processing a simulated return signal based on a transmission radar signal, the receiver comprising;

a mixer configured to receive the simulated return signal and the transmission radar signal;

a low noise amplifier coupled to an output of the mixer;

a high pass filter coupled to an output of the low noise amplifier;

an analog to digital converter coupled to an output of the high pass filter; and

a fast Fourier transform unit coupled to an output of the analog to digital converter; and

generating calibration factors for the radar system by a method comprising;

a) generating the simulated return signal based on one or more range values;

b) generating the transmission radar signal; and

c) determining one or more calibration factors based on the simulated return-signal, the transmission radar signal, and ideal return signal characteristics;

wherein generating the simulated return signal includes programmably frequency dividing a known signal, and modulating the transmission radar signal based on the divided known signal.

2. The method of claim 1, wherein the transmission radar signal is a fixed frequency signal.

3. The method of claim 1, wherein the one or more calibration factors include at least one amplitude calibration factor.

4. The method of claim 1, further comprising:

determining if the radar system is in at least one of a calibration mode or normal mode of operation; and

performing a)-c) if the radar system is determined to be in the calibration mode of operation.

5. The method of claim 4, further comprising applying the determined calibration factors to actual radar return signals, if the radar system is determined to be in a normal mode of operation.

6. A radar system for performing self calibration, the system comprising:

a first component configured to generate a simulated return signal based on one or more range values;

a transmitter configured to generate a transmission radar signal;

a receiver configured to process the simulated return signal based on the transmission radar signal, the receiver comprising;

a mixer configured to receive the simulated return signal and the transmission radar signal;

a low noise amplifier coupled to an output of the mixer;

a high pass filter coupled to an output of the low noise amplifier;

an analog to digital converter coupled to an output of the high pass filter; and

a fast Fourier transform unit coupled to an output of the analog to digital converter; and

a second component configured to determine one or more calibration factors based on the processed simulated return signal and ideal return signal characteristics;

wherein the radar system comprises a Frequency Modulated Continuous Wave (FMCW) radar altimeter system; and

wherein the first component includes a programmable frequency divider configured to create at least one sideband of a known signal, the first component further configured to modulate the transmission radar signal based on the divided known signal.

7. The system of claim 6, wherein the transmission radar signal is a fixed frequency signal.

8. The system of claim 6, wherein the one or more calibration factors include at least one amplitude calibration factor.

9. The system of claim 6, further comprising:

a third component configured to determine if the radar system is in at least one of a calibration mode or normal mode of operation.

10. The system of claim 9, further comprising:

a fourth component configured to apply the determined calibration factors to actual radar return signals, if the radar system is determined to be in a normal mode of operation.

11. A radar altimeter system for an aircraft, the system comprising:

a simulator configured to generate a simulated return signal based on one or more range values;

a transmitter in operative communication with the simulator and configured to generate a transmission radar signal;

a receiver in operative communication with the transmitter and configured to process the simulated return signal based on the transmission radar signal, the receiver comprising;

a mixer configured to receive the simulated return signal and the transmission radar signal;

a low noise amplifier coupled to an output of the mixer;

a high pass filter coupled to an output of the low noise amplifier;

an analog to digital converter coupled to an output of the high pass filter; and

a fast Fourier transform unit coupled to an output of the analog to digital converter; and

a processor in operative communication with the receiver and configured to determine one or more calibration factors based on the processed simulated return signal and ideal return signal characteristics;

wherein the radar altimeter system comprises a Frequency Modulated Continuous Wave (FMCW) radar altimeter system; and

wherein the simulator comprises;

a first frequency divider;

a second frequency divider in operative communication with the first frequency divider

a programmable frequency divider in operative communication with the second frequency divider;

a modulator in operative communication with the programmable frequency divider;

a first attenuator in operative communication with the modulator; and

a second attenuator in operative communication with the modulator.

12. The system of claim 11, wherein the programmable frequency divider is configured to generate one desired frequency at a time that corresponds to one expected frequency in the receiver during operation.

13. The system of claim 11, wherein the transmitter further comprises:

a direct digital synthesizer;

a mixer in operative communication with the direct digital synthesizer;

a digital phase lock loop in operative communication with the mixer; and

a band pass filter in operative communication with the digital phase lock loop.

14. The system of claim 11, wherein the fast Fourier transform unit produces a digital version in the frequency domain of a signal output from the analog to digital converter.