Radar altimeter

• US 20060044182A1
• Filed: 08/26/2004
• Published: 03/02/2006
• Est. Priority Date: 08/26/2004
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Vacanti, David C.
• Granted Patent: US 7,239,266 B2
• Time in Patent Office: Days
• US Class Current: 342/120
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: G01S 7/034 Duplexers switching devices for waveguides H01P1/10; transmit-receive switching in transceivers H04B1/44
• CPC Class Codes: G01S 7/038 Feedthrough nulling circuits
• CPC Class Codes: G01S 7/35 Details of non-pulse systems

Abstract

The present invention provides a radar altimeter system with a closed loop modulation for generating more accurate radar altimeter values. The system includes an antenna, a circulator, a receiver, and a transmitter. The circulator receives or sends a radar signal from/to the antenna. The receiver receives the received radar signal via the circulator. The transmitter generates a radar signal and includes a phase-locked loop circuit for generating the radar signal based on a pre-defined phase signal. The transmitter includes a direct digital synthesizer that generates the phase signal based on a pre-defined clock signal and a control signal. The system includes a digital signal processor and a tail strike warning processor that determine position of a tail of the aircraft relative to ground and present an alert if a warning condition exists based on the determined position of the tail of the aircraft and a predefined threshold.

Claims

1. A radar system on an aircraft, the system comprising:

an antenna for outputting and receiving a radar signal;

a circulator in signal communication with the antenna;

a receiver for receiving the radar signal via the circulator; and

a transmitter for generating a radar signal, the transmitter comprising;

a closed loop circuit for generating the radar signal.

2. The system of claim 1, wherein the transmitter further comprises a direct digital synthesizer for generating a reference signal based on a pre-defined clock signal and a control signal, wherein the closed loop circuit generates the radar signal based on the reference signal.

3. The system of claim 2, wherein the transmitter further includes a clock device for generating the clock signal.

4. The system of claim 1, wherein the antenna is a micro-strip antenna.

5. The system claim 4, wherein the circulator, the receiver, and the transmitter are formed on a circuit board, the circuit board being connected to the antenna, wherein the circulator and antenna are connected by printed wiring.

6. The system claim 5, wherein the distance between the circuit board and the antenna is less than one inch.

7. The system of claim 5, further comprising:

a housing for hermitically sealing the circuit board.

8. The system of claim 7, further comprising an analog-to-digital converter for converting the signal received by the receiver into a digital signal, wherein the converter is formed on the circuit board.

9. The system of claim 8, further comprising:

a component for generating the control signal and for processing the digital signal, wherein the component is remotely located from the housing.

10. The system of claim 9, wherein the component is located in an electronics bay of the aircraft.

11. The system of claim 9, further comprising:

a tail strike warning component in signal communication with the component for determining position of a tail of the aircraft relative to ground based on the processed digital signal.

12. The system of claim 11, further comprising:

an output device in signal communication with the tail strike warning processor for presenting an alert if the tail strike warning processor has determined that a warning condition exists based on the determined position of the tail of the aircraft and a predefined threshold.

13. The system of claim 3, wherein the closed-loop circuit is a phased-locked loop circuit.

14. The system of claim 13, wherein the transmitter produces a modulated radar signal having a linearity error less than 0.5%.

15. The system of claim 9, wherein modulation quality of transmitter remains constant over time.

16. The system of claim 9, wherein a signal-to-noise ratio associated with processing of the digital signal remains constant over time.

17. A radar system on an aircraft, the system comprising:

a receive antenna for receiving a radar signal;

a transmit antenna for outputting a radar signal;

a receiver for receiving the received radar signal; and

a transmitter for generating a radar signal, the transmitter comprising;

a closed loop circuit for generating the radar signal based on a pre-defined phase signal.

18. A method performed by a radar altimeter system on an aircraft, the method comprising:

generating a radar signal using a transmitter having a closed loop circuit;

outputting the generated radar signal via an antenna; and

receiving a radar signal at a receiver via the antenna.

19. The method of claim 18, wherein generating the radar signal is further based on a reference signal, wherein the reference signal is generated based on a pre-defined clock signal and a control signal.

20. The method of claim 19, further comprising:

converting the signal received by the receiver into a digital signal;

sending the digital signal to a component; and

determining at the component an altitude value based on the digital signal;

generating the control signal based on the digital signal,

wherein the component is remotely located from the receiver, transmitter, and antenna.

21. The method of claim 20, wherein the component is located in an electronics bay of the aircraft.

22. The method of claim 20, further comprising:

presenting an alert if the altitude value is below a threshold value.

23. The method of claim 18, wherein the closed-loop circuit is a phased-locked loop circuit.

24. The method of claim 18, wherein the generated radar signal has a linearity error less than 0.5%.

25. The method of claim 18, wherein modulation quality of the radar signal remains constant over time.

26. A method of making a radar altimeter system on an aircraft, the method comprising:

providing a printed circuit board;

incorporating a transmitter having a closed loop circuit into the printed circuit board;

incorporating a receiver into the printed circuit board;

incorporating a circulator into the printed circuit board;

connecting the transmitter and receiver to the circulator;

connecting an antenna to the circulator with printed wiring.

27. The method of claim 26, wherein the antenna is a micro-strip antenna.

28. The method claim 27, wherein the distance between the circuit board and the antenna is less than one inch.

29. The method of claim 26, further comprising:

hermitically sealing the circuit board in a housing.

30. The method of claim 26, further comprising:

incorporating an analog-to-digital converter into the printed circuit board;

connecting the analog-to-digital converter to the receiver;

providing a processor for determining altitude values; and

electrically connecting the processor to the analog-to-digital converter,

wherein the processor is remotely located from the housing.