Digital sounder module and method for detecting

• US 20040109388A1
• Filed: 11/12/2003
• Published: 06/10/2004
• Est. Priority Date: 12/05/2002
• Status: Active Grant

• Current Assignee: Flir Belgium BVBA (Teledyne Technologies Incorporated)
• Original Assignee: Raymarine Incorporated (Teledyne Technologies Incorporated)
• Inventors: Sogaard, Sten
• Granted Patent: US 6,950,372 B2
• Time in Patent Office: Days
• US Class Current: 367/100
• CPC Class Codes: G01S 15/96 for locating fish
• 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: Y10S 367/90 Sonar time varied gain control systems

Abstract

The invention is a digital sounder module and its method for detection. The digital sounder module includes a sonar carrier wave producing means, a band-pass filter, a pre-amplifier for providing a high sensitivity and extending a wide dynamic range, and an analog-to-digital converter for providing a digital implementation of a superheterodyne detector and producing an intermediate frequency. The digital sounder module also includes a programmable logic device for controlling a gain of the pre-amplifier and for digitally filtering the intermediate frequency and a microprocessor. The method implemented by the controlled per-amplifier gain processes the return echo signal by controlled ramp up of the gain over time to compensate for the change in signal strength in proportion to the length of the return path.

Claims

1. A digital sounder module comprising:

a sonar transducer for transmitting an acoustic sonar wave at a selected frequency and pulse rate and for receiving echos of said transmitted acoustic wave reflected from objects and for converting said received acoustic sonar wave into a first electrical signal;

a band-pass filter for providing a first wide bandpass filtration on said first signal to produce a second signal;

an amplifier for controlled amplification of said second signal to produce a third signal;

an analog to digital converter for receiving said third signal and providing a digital sampling of said signal;

a programmable logic device for providing a variable gain control signal to said amplifier for normalization of the amplitude of reflected echos within said second signal by increasing gain in proportion to the distance of said echo reflection source from said sonar transducer; and

a microprocessor.

2. The digital sounder module of claim 1 wherein the band-pass filter is wide-banded.

3. The digital sounder module of claim 2 wherein the band-pass filter is centered around 50 kHz or 200 kHz.

4. The digital sounder module of claim 2 wherein the band-pass filter is modified to filter any frequency between 10 kHz and 200 kHz.

5. The digital sounder module of claim 1 wherein the pre-amplifier is programmable and provides an optimal performance at any depth/pulse width.

6. The digital sounder module of claim 1 wherein said variable gain control signal normalizes the amplitude of a sonar pulse by increasing gain over time from the initial reception of a pule echo to the conclusion of reception of a pulse echo.

7. The digital sounder module of claim 6 wherein a gain of the amplifiers are set though a digital programmable feed-back resistor.

8. The digital sounder module of claim 7 wherein the pre-amplifier provides a sensitivity time control function that reduces surface clutter and background noise by decreasing the gain in shallow water.

9. The digital sounder module of claim 1 wherein the pre-amplifier is digitally controlled by a gain curve sent from the programmable logic device.

10. The digital sounder module of claim 9 wherein the gain curve increases with depth and allows for a continuous reprogramming of a programmable filter.

11. The digital sounder module of claim 1 wherein the analog-to-digital converter comprises:

a conversion rate for converting the sonar carrier wave to a digitized return signal which acts as a harmonic sub-sampling, wherein the sonar carrier wave is transformed into an intermediate frequency.

12. The digital sounder module of claim 1 wherein the programmable logic device operates as a co-processor for the main processor.

13. The digital sounder module of claim 12 wherein the programmable logic device performs a simplified implementation of a non-coherent windowed in-phase/quadrature detector to filter the intermediate frequency return signal digitally.

14. A method for detecting a sonar carrier wave comprising:

receiving a sonar carrier wave;

limiting the sonar carrier wave with a band-pass filter;

amplifying the filtered sonar carrier wave with a pre-amplifier;

feeding the amplified sonar carrier wave to an analog-to-digital converter to produce an intermediate frequency of the sonar carrier wave;

controlling the pre-amplifier and the analog-to-digital converter a programmable logic device;

filtering digitally the sonar carrier wave; and

detecting digitally the sonar carrier wave.