Method of operating a digital radar or sonar apparatus

• US 9,372,257 B2
• Filed: 05/01/2015
• Issued: 06/21/2016
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Flir Belgium BVBA (Teledyne Technologies Incorporated)
• Original Assignee: Raymarine UK Limited (Teledyne Technologies Incorporated)
• Inventors: Jales, Richard, Lawrence, Andrew, Maindrou, Matthieu
• Primary Examiner(s): BYTHROW, PETER M
• Application Number:
  US14/702,498
• Publication Number:
  US 20150316645A1
• Time in Patent Office: 417 Days
• Field of Search: 342/118
• US Class Current: 1/1
• CPC Class Codes: G01S 13/10 using transmission of interrupted, pulse modulated waves determination of distance by phase measurement G01S13/32
• CPC Class Codes: G01S 13/106 using transmission of pulses having some particular characteristics G01S13/12, G01S13/22, G01S13/24, G01S13/26, G01S13/28 and G01S13/30 take precedence
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 15/102 using transmission of pulses having some particular characteristics
• CPC Class Codes: G01S 15/89 for mapping or imaging
• CPC Class Codes: G01S 7/062 in which different colours are used
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: G01S 7/285 Receivers
• CPC Class Codes: G01S 7/292 Extracting wanted echo-signals
• CPC Class Codes: G01S 7/34 Gain of receiver varied automatically during pulse-recurrence period, e.g. anti-clutter gain control
• CPC Class Codes: G01S 7/526 Receivers
• CPC Class Codes: G01S 7/5273 using digital techniques
• CPC Class Codes: G01S 7/529 Gain of receiver varied automatically during pulse-recurrence period for seismic signals G01V1/245
• CPC Class Codes: G01S 7/62 Cathode-ray tube displays
• CPC Class Codes: G01S 7/6263 in which different colours are used

Abstract

A radar or sonar system amplifies the signal received by an antenna of the radar system or a transducer of the sonar system is amplified and then subject to linear demodulation by a linear receiver. There may be an anti-aliasing filter and an analog-to-digital converter between the amplifier and the linear receiver. The system may also have a digital signal processor with a network stack running in the processor. That processor may also have a network interface media access controller, where the system operates at different ranges, the modulator may produce pulses of two pulse patterns differing in pulse duration and inter-pulse spacing, those pulse patterns are introduced and used to form two radar images with the two images being derived from data acquired in a duration not more than twenty times larger than the larger inter-pulse spacing, or for a radar system, larger than one half of the antenna resolution time. One or more look-up tables may be used to control the amplifier. The radar system may generate digital output which comprises greater than eight levels of radar video.

Claims

1. A method comprising:

generating a sequence of pulse signals;

converting the sequence of pulse signals to ranging signals, wherein the ranging signals are radar signals of a radar apparatus or sonar signals of a sonar apparatus;

emitting the ranging signals;

receiving passively reflected return signals in response to the ranging signals;

amplifying the return signals, wherein the amplified return signals are analog signals;

converting, by an analog-to-digital converter, the amplified return signals to digital signals;

generating, by a linear demodulator, a digital output from the digital signals representing the amplified return signals; and

processing the digital output for display and/or analysis.

2. The method of claim 1, wherein the linear demodulator is implemented by a linear receiver comprising a plurality of linear amplifiers.

3. The method of claim 1, further comprising filtering the amplified return signals by an anti-aliasing filter, wherein the analog-to-digital converter is a sub-sampling analog-to-digital converter.

4. The method of claim 3, wherein the filtering comprises restricting a bandwidth of the amplified return signals to satisfy the Shannon-Nyquist-Kotelnikov sampling theorem.

5. The method of claim 3, further comprising filtering the digital signals from the sub-sampling analog-to-digital converter.

6. The method of claim 1, further comprising displaying a pseudo-colour representation of an amplitude of the return signals from the digital output.

7. The method of claim 1, further comprising filtering the amplified return signals by an anti-aliasing filter, wherein the converting comprises converting the filtered amplified return signals to the digital signals.

8. The method of claim 1, wherein the processing is performed by a digital processor, the method further comprising running a network stack on the digital processor.

9. The method of claim 1, further comprising providing the digital output to a network unit comprising a media access controller and a physical layer interface.

10. The method of claim 1, wherein:

the sequence of pulse signals comprises pulses of a first pulse pattern interleaved with pulses of a second pulse pattern;

the first and second pulse patterns differ in pulse duration and inter-pulse spacing; and

the processing comprises generating a first image associated with the pulses of the first pulse type and a second image associated with the pulses of the second pulse type.

11. The method of claim 10, wherein the sequence of pulse signals comprises a plurality of the pulses of the second type interleaved between successive pulses of the first type.

12. The method of claim 1, further comprising controlling a gain of an amplifier performing the amplifying, wherein the controlling comprises using at least one look-up table containing data for compensating for range-dependent variation of the return signals.

13. The method of claim 12, wherein the at least one look-up table comprises multiple table regions each associated with a corresponding range.

14. The method of claim 12, wherein the controlling comprises using a plurality of look-up tables each associated with a corresponding range.

15. The method of claim 1, further comprising controlling a gain of an amplifier performing the amplifying, wherein the amplifier comprises a plurality of gain stages, wherein the controlling comprises using at least one look-up table containing data for at least one of the gain stages.

16. The method of claim 15, wherein the at least one look-up table comprises multiple table regions each associated with a corresponding one of the gain stages.

17. The method of claim 15, wherein the controlling comprises using a plurality of look-up tables each associated with a corresponding one of the gain stages.

18. The method of claim 17, further comprising:

adding together outputs from the plurality of look-up tables; and

applying saturation logic to the added-together outputs to control the amplifier within a gain control range.

19. The method of claim 1, further comprising applying non-linear dynamic range matching to the digital output.

20. The method of claim 1, wherein:

the ranging signals are radar signals;

the ranging signals and the received return signals are X-band signals;

the method further comprises converting the X-band return signals to intermediate frequency return signals;

the amplifying comprises amplifying the intermediate frequency return signals;

the filtering comprises filtering the amplified intermediate frequency return signals;

the analog-to-digital converter is a sub-sampling analog-to-digital converter; and

the converting comprises sampling the filtered amplified intermediate frequency return signals at a sample rate less than the intermediate frequency.