Digital technique for FM modulation of infrared headphone interface signals

摘要

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.

主权项

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 dock signal having a dock 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 dock 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.