RDS Encoder For FM Transmitter

1 . A system comprising:

a processor;

a computer readable storage medium coupled to the processor, wherein the computer readable storage medium comprises:

(i) code for differentially encoding a radio data message from a radio data message source; and

(ii) code for generating a bi-phase coded radio data signal from the differentially encoded radio data message; and

a wireless transmitter, wherein the wireless transmitter is adapted to transmit a wireless signal including the radio data message, wherein the wireless signal is derived from the bi-phase coded radio-data signal.

2 . The system of claim 1 , wherein the radio data message is generated using a pilot tone having a frequency of about 19 kHz.

3 . The system of claim 1 , wherein the code for generating the bi-phase coded radio data signal comprises code for generating bi-phase impulse pairs.

4 . The system of claim 1 , further comprising code to filter the bi-phase coded radio data signal to remove signals above 2,375 Hz.

5 . The system of claim 1 , further comprising code for multiplying a filtered version of the bi-phase coded radio data signal with a 57 kHz signal to generate a mixed signal which is added to an audio stereo multiplex signal to form a modulation signal, wherein the modulation signal is used to modulate the wireless transmitter.

6 . The system of claim 1 , further comprising code for generating a subcarrier with the bi-phase coded radio data signal.

7 . The system of claim 6 , wherein code for generating a subcarrier comprises code for forming a finite impulse response filter configured to generate the subcarrier in response to a predetermined input sampling frequency.

8 . The system of claim 7 , wherein the input sampling frequency comprises 19 kHz.

9 . A wireless transmission system comprising:

a first logic circuit configured to digitally process a digital data signal received from a data source and a clock signal to generate a modulation signal, wherein the data signal comprises digital data pertaining to the content of a baseband signal; and

a radio frequency transmitter circuit configured to transmit a wireless signal carrying the radio signal and digital data in response the modulation signal and the baseband signal.

10 . The system of claim 9 , wherein the logic circuit comprises a microcontroller configured as a digital signal processor configured to generate the modulation signal in response to the digital data signal.

11 . The system of claim 9 , wherein the wireless signal is formed from the sum of a multiplex signal and the modulation signal.

12 . The system of claim 11 , wherein the multiplex signal comprises an audio signal.

13 . The system of claim 9 , wherein the first logic circuit comprises a second logic circuit configured to generate a bi-phase coded radio data signal portion of the modulation signal.

14 . The system of claim 11 , wherein the first logic circuit comprises a third logic circuit configured to process the bi-phase coded radio data signal to generate a sub-carrier portion of the modulation signal used to carry the digital data.

15 . The system of claim 12 , wherein the third logic circuit is configured as a finite impulse response filter used to select the sub-carrier portion of the modulation signal.

16 . A method of wirelessly transmitting within a radio data system a baseband signal and digital data pertaining to the baseband signal, the method comprising:

processing digital data pertaining to the content of a baseband signal to form a first modulation signal;

generating from the first modulation signal a plurality of harmonic signals;

selecting one harmonic signal from the plurality of harmonic signals to generate a second modulation signal;

summing the baseband signal with the second modulation signal to generate a third modulation signal; and

modulating an output frequency of a wireless transmitter with the third modulation signal to generate a wireless signal transmitting the baseband signal and the digital data across a transmission medium.

17 . The method of claim 16 , wherein processing comprises digital signal processing performed by a processor configured to generate the first modulation signal from the digital data.

18 . The method of claim 16 , wherein the third modulation signal is formed without mixing signals together.

19 . The method of claim 16 , wherein the first modulation signal comprises bi-phase symbols.

20 . The method of claim 16 , wherein selecting comprises filtering the harmonic signals to generate the selected one harmonic signal.

21 . The method of claim 19 , wherein filtering comprises processing the first modulation signal using a finite impulse response filter.

22 . A device configured to receive content comprising at least radio data system (RDS) data and wirelessly transmit the RDS data to a receiver, the portable device, comprising:

an input configured to receive the content from a portable source;

circuitry configured to convert the content into a wireless signal in response to a pilot tone signal having a frequency less than about 50 kHz; and

a wireless transmitter configured to transmit the wireless signal over a short range.

23 . The device of claim 22 , wherein the pilot tone signal comprises a signal having a frequency of approximately 19 kHz.