Wideband sonar with pulse compression

• US 9,423,494 B2
• Filed: 04/24/2014
• Issued: 08/23/2016
• Est. Priority Date: 10/26/2011
• Status: Active Grant

• Current Assignee: Teledyne FLIR LLC (Teledyne Technologies Incorporated)
• Original Assignee: FLIR Systems, Inc. (Teledyne Technologies Incorporated)
• Inventors: Stokes, Paul, Wellcome, David
• Primary Examiner(s): PIHULIC, DANIEL T
• Application Number:
  US14/261,342
• Publication Number:
  US 20140233355A1
• Time in Patent Office: 852 Days
• US Class Current: 1/1
• CPC Class Codes: B06B 1/0223 for generating signals continuous in time
• CPC Class Codes: G01S 15/02 using reflection of acoustic waves G01S15/66 takes precedence
• CPC Class Codes: G01S 7/521 Constructional features
• CPC Class Codes: G01S 7/524 Transmitters
• CPC Class Codes: H01F 19/06 Broad-band transformers, e.g. suitable for handling frequencies well down into the audio range

Abstract

A sonar transmitter includes digital logic that controls switches coupled to a primary coil of a transformer. The switches are driven to produce at least one voltage pulse across a secondary coil for the transformer to produce a series of voltage pulses approximating the desired signal. The transformer may comprise: a secondary coil having a plurality of windings arranged into a first section, a middle section, and a final section; and a primary coil winding wound only with the secondary coil windings forming the middle section.

Claims

1. A wideband sonar transmitter, comprising:

a power supply;

a pair of switches; and

a wideband transformer having a secondary coil for driving a transducer and a primary coil having a center tap driven by the power supply, wherein a first end of the primary coil couples to ground through a first one of the switches and a second end of the primary coil couples to ground through a second one of the switches, and wherein the wideband transformer includes a secondary coil including a plurality of windings arranged into a first section, a middle section, and a final section, and a primary coil winding wound only with the secondary coil windings forming the middle section.

2. The wideband sonar transmitter of claim 1, wherein the switches comprise MOSFET transistors.

3. The wideband sonar transmitter of claim 1, further comprising digital logic configured to generate on and off times for each of the switches in the pair of switches to approximate a desired waveform across the transducer.

4. The wideband sonar transmitter of claim 3, wherein the digital logic includes an FPGA adapted to store an array of the on and off times.

5. The wideband transmitter of claim 4, further comprising a CPU configured to select for a desired chirp waveform and to calculate the on and off times accordingly.

6. The wideband transformer of claim 1, wherein the primary coil comprises two windings separated by a first center tap, and wherein the middle section of the secondary coil comprises two windings separated by a second center tap.

7. The wideband transformer of claim 1, further comprising:

a first layer of insulation separating the first section from the middle section, and

a second layer of insulation separating the middle section from the final section.

8. The wideband transformer of claim 1, wherein a leakage inductance for the primary coil winding is no greater than 1.0 μ

H over an operating frequency range of 25 KHz to 255 KHz.

9. The wideband transformer of claim 1, wherein a shunt inductance for the primary coil winding is at least 2.2 mH over an operating range of 25 KHz to 255 KHz.

10. A method of generating wideband sonar pulses, comprising;

in digital logic, analyzing a desired wideband sonar signal to identify positive half cycles and negative half cycles of the desired signal; and

with regard to each half cycle, approximating the half cycle by driving switches coupled to a transformer'"'"'s primary coil to produce at least one voltage pulse across a secondary coil for the transformer to produce a series of voltage pulses approximating the desired signal.

11. The method of claim 10, wherein the switches are driven so as to pulse width modulate the voltage pulses so as to approximate a desired peak amplitude for each half cycle.

12. The method of claim 11, wherein each half cycle is approximated by a single voltage pulse.

13. The method of claim 11, wherein each half cycle is approximated by a pair of voltage pulses.

14. The method of claim 13, wherein the switches are driven so as to produce a desired separation between the voltage pulses in each pair.

15. The method of claim 14, wherein the desired separation suppresses a harmonic in an approximated signal formed by the series of voltage pulses.

16. A sonar, comprising

a power supply;

a pair of switches; and

a power amplifier including a wideband transformer having a secondary coil for driving a transducer and a center-tapped primary coil driven by the power supply, the center tap coupling to the pair of switches, wherein the wideband transformer includes;

a secondary coil including a plurality of windings arranged into a first section, a middle section, and a final section; and

a primary coil winding wound only with the secondary coil windings forming the middle section.

17. The sonar of claim 16, further comprising a signal generator for driving the pair of switches so as to drive the secondary coil with an approximately sinusoidal voltage.

18. The sonar of claim 17, wherein the power supply comprises a bank of capacitors controlled by the signal generator.

19. The sonar of claim 16, wherein a leakage inductance for the primary coil winding is no greater than 1.0 μ

H over a sonar operating frequency range of 25 KHz to 255 KHz.