Digital Technique for FM Modulation of Infrared Headphone Interface Signals

• US 20130156215A1
• Filed: 12/15/2011
• Published: 06/20/2013
• Est. Priority Date: 12/15/2011
• Status: Active Grant

• Current Assignee: Panasonic Automotive Systems Company of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Automotive Systems Company of America (Panasonic Holdings Corporation)
• Inventors: Hickerson, Dallas Dwight, Whitaker, Joseph Cecil
• Granted Patent: US 9,094,761 B2
• Time in Patent Office: Days
• US Class Current: 381/74
• CPC Class Codes: H04R 1/10 Earpieces; Attachments therefor ; Earphones; Monophonic headphones H04R1/28 takes precedence; stereophonic headphones H04R5/033
• CPC Class Codes: H04R 1/1008 Earpieces of the supra-aural or circum-aural type
• CPC Class Codes: H04R 1/1091 Details not provided for in groups H04R1/1008 - H04R1/1083
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones

Abstract

A method of modulating an infrared headphone interface signal includes providing a first audio signal having an analog audio value. A memory is provided having a plurality of locations and containing digital phase offset values. A clock signal having a clock frequency is provided. A second audio signal having a center carrier frequency that deviates with the analog audio value of the first audio signal is provided. An instantaneous value of the center carrier frequency is determined. The clock frequency is divided by the instantaneous carrier frequency value to calculate a number of samples per cycle. A number of location addresses in the memory is divided by the number of samples per cycle to calculate a memory access interval. The memory is accessed at addresses separated by the memory access interval. The digital phase offset values at the accessed memory addresses are used to reproduce the first audio signal.

Claims

1. A method for modulating an infrared headphone interface signal, comprising the steps of:

providing a first audio signal having an analog audio value;

providing a memory having a plurality of locations and containing digital phase offset values;

providing a clock signal having a clock frequency;

providing a second audio signal having a center carrier frequency that deviates with the analog audio value of the first audio signal;

determining an instantaneous value of the center carrier frequency;

dividing the clock frequency by the instantaneous carrier frequency value to thereby calculate a number of samples per cycle;

dividing a number of location addresses in the memory by the number of samples per cycle to thereby calculate a memory access interval;

accessing the memory at location addresses separated by the calculated memory access interval; and

using the digital phase offset values at the accessed memory location addresses to reproduce the first audio signal by use of headphones.

2. The method of claim 1 wherein the center carrier frequency has a deviation frequency range between a minimum carrier frequency corresponding to a minimum said analog audio value, and a maximum carrier frequency corresponding to a maximum said analog audio value.

3. The method of claim 1 wherein the memory is disposed within the headphones.

4. The method of claim 1 wherein the accessing step includes transmitting an infrared signal including the addresses separated by the calculated memory access interval.

5. The method of claim 4 wherein the infrared signal is transmitted to the headphones.

6. The method of claim 1 wherein the digital phase offset values sinusoidally oscillate with a progression along the memory locations.

7. The method of claim 1 comprising the further step of establishing the center carrier frequency by entering a corresponding constant value into a phase offset generator.

8. An audio headphone arrangement, comprising:

a source of a first audio signal having an analog audio value;

a pair of audio headphones including a memory device having a plurality of locations containing corresponding digital phase offset values; and

an infrared transmitter apparatus including;

a clock generator configured to produce a clock signal having a clock frequency;

a receiver in communication with the source of the first audio signal;

a phase offset generator in communication with the clock generator and with the receiver, the phase offset generator being configured to;

sample a second audio signal that is dependent on the first audio signal, a frequency of the sampling being dependent upon the clock signal; and

generate a phase offset signal dependent upon the sampling step; and

a phase accumulator in communication with the phase offset generator and configured to;

calculate a net phase value dependent upon the phase offset signal; and

transmit an infrared signal to the headphones, the infrared signal being indicative of location addresses in the memory device to be accessed in order for the headphones to reproduce the first audio signal.

9. The arrangement of claim 8 wherein a constant value is an input to the phase offset generator, the phase offset generator being configured to used the constant value input to establish a center frequency of the second audio signal.

10. The arrangement of claim 8 wherein the memory device has a size approximately between 16 kilobytes and 16 megabytes.

11. The arrangement of claim 8 wherein the second audio signal has a center carrier frequency with a deviation frequency range between a minimum carrier frequency corresponding to a minimum value of the first audio signal, and a maximum carrier frequency corresponding to a maximum value of the first audio signal.

12. The arrangement of claim 8 wherein the digital phase offset values sinusoidally oscillate with a progression along the location addresses of the memory device.

13. The arrangement of claim 8 wherein the infrared signal is dependent upon the net phase value.

14. The arrangement of claim 8 further comprising an audio analog to digital converter configured to use the clock signal to digitize the first audio signal, the second audio signal being dependent upon the first audio signal.

15. A method of operating headphones, comprising the steps of:

providing a memory having a plurality of locations and containing digital phase offset values;

providing a second audio signal having a center carrier frequency that deviates with an analog audio value of a first audio signal;

determining an instantaneous value of the center carrier frequency;

dividing a frequency of a clock signal by the instantaneous carrier frequency value to thereby calculate a number of samples per cycle;

dividing a number of location addresses in the memory by the number of samples per cycle to thereby calculate a memory access interval;

transmitting an infrared signal indicating location addresses in the memory, the location addresses being separated by the calculated memory access interval; and

using the digital phase offset values at the accessed memory location addresses to reproduce the first audio signal by use of the headphones.

16. The method of claim 15 wherein the accessed memory location addresses each correspond to a respective word.

17. The method of claim 15 wherein the center carrier frequency has a deviation frequency range between a minimum carrier frequency corresponding to a minimum said analog audio value, and a maximum carrier frequency corresponding to a maximum said analog audio value.

18. The method of claim 15 wherein the memory is disposed within the headphones.

19. The method of claim 15 wherein the infrared signal is transmitted to the headphones.

20. The method of claim 15 wherein a digital phase offset values sinusoidally oscillate with a progression along the memory location addresses.