Digital radar or sonar apparatus

• US 9,024,816 B2
• Filed: 12/30/2013
• Issued: 05/05/2015
• 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:
  US14/144,143
• Publication Number:
  US 20140320336A1
• Time in Patent Office: 491 Days
• Field of Search: 342/104, 342/115, 342/118, 342134-144, 342/175, 342/176, 342/179
• US Class Current: 342/195
• 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. An apparatus comprising:

a modulator for generating a sequence of pulse signals;

a transmitter for converting the sequence of pulse signals to ranging signals;

an antenna for emitting the ranging signals and receiving return signals;

an amplifier for amplifying the return signals;

a switching device for switchedly interconnecting the transmitter to the antenna and the antenna to the amplifier; and

a signal processor processing the amplified return signals for display and/or analysis, wherein the apparatus comprises either a radar apparatus that provides the ranging signals as radar signals or a sonar apparatus that provides the ranging signals as sonar signals,

characterised in that;

the apparatus further includes a linear receiver between the amplifier and the signal processor, the linear receiver including a linear demodulator generating a digital output representing the amplified return signals for processing by the signal processor.

2. The apparatus of claim 1, wherein the linear receiver comprises a plurality of linear amplifiers.

3. The apparatus of claim 1, further comprising:

an analog-to-digital converter for converting the amplified return signals to digital signals; and

an anti-aliasing filter connected to the amplifier for filtering the amplified return signals, wherein the analog-to-digital converter is a sub-sampling analog-to-digital converter for converting the filtered signals to the digital signals.

4. The apparatus of claim 3, wherein the anti-aliasing filter is arranged to restrict the bandwidth of the amplified return signals to satisfy the Shanon-Nyquist- Kotelnikov sampling theorem.

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

6. The apparatus of claim 1, further comprising a display arranged to show a pseudo-colour representation of the amplitude of the return signals from the output of the signal processor.

7. The apparatus of claim 1, further comprising:

an analog-to-digital converter for converting the amplified return signals to digital signals; and

an anti-aliasing filter connected to the amplifier for filtering the amplified return signals, wherein the analog-to-digital converter is an analog-to-digital converter for converting the filtered signals to the digital signals, wherein the signal processor is a digital processor comprising a network stack running in the digital processor.

8. The apparatus of claim 1, further comprising:

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

an anti-aliasing filter connected to the amplifier for filtering the amplified return signals, wherein the analog-to-digital converter is an analog-to-digital converter for converting the filtered signals to the digital signals, wherein the signal processor is a digital signal processor; and

a network interface media access controller and a physical layer interface that are connected to a digital signal processing bus.

9. The apparatus of claim 1, wherein the apparatus is a radar apparatus and the radar apparatus further comprises an antenna drive for rotating the antenna with a predetermined revolution duration;

wherein the modulator is arranged to generate the sequence of pulse signals such that the sequence comprises pulses of a first pulse pattern and pulses of a second pulse pattern, the first and second pulse patterns differing in pulse duration and inter-pulse spacing, the first and second pulse patterns being interleaved such that within the predetermined revolution duration there are a plurality of pulses of each pulse type; and

wherein the signal processor is arranged to generate first radar image from the amplified return signals associated with the pulses of the first pulse type and a second radar image from the amplified return signals associated with the pulses of the second pulse type, such that the pulses of the first and second pulse types at any time are within a time not greater than one half of the predetermined revolution duration.

10. The apparatus of claim 1, wherein the apparatus is a radar apparatus and the radar apparatus further comprises an antenna drive for rotating the antenna with a predetermined revolution duration;

wherein the modulator is arranged to generate the sequence of pulse signals such that the sequence comprises pulses of a first pulse pattern and pulses of a second pulse pattern, the first and second pulse patterns differing in pulse duration and inter-pulse spacing, the first and second pulse patterns being interleaved such that within the predetermined revolution duration there are a plurality of pulses of each pulse type; and

wherein the signal processor is arranged to generate a first radar image from the amplified return signals associated with the pulses of the first pulse type and a second radar image from the amplified return signals associated with the pulses of the second pulse type, such that the pulses of the first and second pulse types at any time are within a time not greater than twenty times whichever is larger of the pulse spacing of the first and second pulse patterns.

11. The apparatus of claim 1, wherein the apparatus is a sonar apparatus and the modulator is arranged to generate the sequence of pulses and that the sequence comprises pulses of a first pulse pattern and pulses of a second pulse pattern, the first and second pulse patterns differing in pulse duration, pulse spacing, and being interleaved;

and

wherein the signal processor is arranged to generate a first sonar image from the amplified return signals associated with the pulses of the first pulse type and a second sonar image of from the amplified return signals associated with the pulses of the second pulse type, and that the pulses of the first and second pulse types at any time are within a time not greater than twenty times whichever is longer of the pulse spacing of the first and second pulse patterns.

12. The apparatus of claim 1, further comprising a controller for controlling the gain of the amplifier, the controller comprising at least one look-up table containing data for compensating for any range-dependent variation of the return signals.

13. The apparatus of claim 12, wherein the apparatus is configured to operate at multiple ranges and wherein there are multiple look-up tables, each range having a corresponding look-up table.

14. The apparatus of claim 12, wherein the apparatus is configured to operate at multiple ranges and wherein the at least one look-up table has multiple table regions, each range having a corresponding table region.

15. The apparatus of claim 12, wherein the amplifier has a plurality of gain stages, and wherein there are a plurality of the look-up tables, each table corresponding to one of the gain stages.

16. The apparatus of claim 12, wherein the amplifier has a plurality of gain stages, and wherein the at least one look-up table has a plurality of table regions, each table region corresponding to one of the gain stages.

17. The apparatus of claim 15, further comprising an adder configured to add together outputs from the plurality of look-up tables for the plurality of table regions and saturation logic arranged to be applied to the added-together outputs, wherein an appropriate gain stage of the amplifier is determined on the basis of the saturation logic.

18. The apparatus of claim 1, wherein the apparatus is a radar apparatus and the signal processor is a digital signal processor arranged to generate a digital output which comprises greater than eight levels of radar video.

19. The apparatus of claim 18, further comprising means for subjecting the digital output of the digital signal processor to non-linear dynamic range matching.

20. The apparatus of claim 3, wherein the apparatus is a radar apparatus;

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

the apparatus further comprises a converter for converting the X-band return signals to intermediate frequency return signals;

wherein the amplifier operates on the intermediate frequency return signals;

wherein the filter operates on the amplified intermediate frequency return signals; and

wherein the sub-sampling analog-to-digital converter samples the filtered amplified intermediate frequency return signals at a sample rate less than the intermediate frequency.