Digital FM radio system

Abstract

The present invention is for a high quality digital FM radio system that utilizes the subcarrier band to generate digital audio signals. The hybrid FM radio system utilizes the subcarrier band to transmit the digital FM signals that are synchronized to the analog FM signals. The receiver processes both the analog and digital signals and a high quality FM signal results. The receiver may switch between the traditional analog signal and the higher quality digital signal automatically to present the best possible audio to the user.

1. A hybrid FM radio system providing an audio output, comprising:
 a transmitter section transmitting an audio transmission as a standard analog FM signal and a digital FM signal, wherein said digital FM signal is packetized and transmitted on a subcarrier band, and said analog FM signal transmitted on a main carrier band; 
 a receiver section for receiving said analog FM signal and said digital FM signal, wherein said digital FM signal is decoded and converted to a digital decoded analog FM output and said analog FM signal is processed to provide a standard analog FM output, and wherein said standard analog FM output and said digital decoded analog FM output are synchronized; and 
 a means for automatically determining said audio output from said digital decoded analog FM output and said standard analog FM output. 
 
     
     
       2. The hybrid FM radio system according to  claim 1 , wherein said digital FM signal is directly derived from a digital source. 
     
     
       3. The hybrid FM radio system according to  claim 1 , wherein said digital FM signal is derived from said analog FM signal. 
     
     
       4. The hybrid FM radio system according to  claim 3 , further comprising an analog delay in said analog FM signal, wherein said analog delay is substantially equivalent to a cumulative time delay of processing said digital FM signal in said transmitter section and processing said digital FM signal in said receiver section. 
     
     
       5. The hybrid FM radio system according to  claim 1 , wherein said means for determining is a multiplexer that switches between said standard analog FM output and said digital decoded analog FM output. 
     
     
       6. The hybrid FM radio system according to  claim 1 , wherein said digital FM signal is packetized in an MP3 format. 
     
     
       7. A hybrid FM radio system producing a quality audio output at a receiver, comprising:
 a transmitter section transmitting an analog FM signal and a digital FM signal, wherein said digital FM signal is packetized and transmitted on a subcarrier band; 
 a receiver section for receiving said analog FM signal and said digital FM signal, wherein said digital FM signal is decoded and converted to an analog output; 
 a multiplexer connected to said analog FM signal and said digital FM signal, wherein said multiplexer switches in response to parameters selected from the group consisting of: a user input, a determination that said digital FM signal is a copy of said analog FM signal, a status determination that said digital FM signals is decoded without errors, and a synchronization determination that said digital FM signal is synchronized with said analog FM signal; and 
 wherein a multiplexer output generates said audio output. 
 
     
     
       8. The hybrid FM radio system according to  claim 7 , wherein said multiplexer automatically switches between said digital FM signal and said analog FM signal. 
     
     
       9. The hybrid FM radio system according to  claim 7 , further comprising an analog delay in said analog FM signal, wherein said analog delay is substantially equivalent to a cumulative time delay of processing said digital FM signal in said transmitter section and processing said digital FM signal in said receiver section. 
     
     
       10. The hybrid FM radio system according to  claim 7 , wherein said digital FM signal is packetized in an MP3 format. 
     
     
       11. A hybrid FM receiver capable of receiving an analog FM signal and a digital FM signal and producing an audio output, comprising:
 an antenna for receiving said analog FM signal and said digital FM signal with a front end processing section and a FM demodulator; 
 an analog FM receiver section connected to said FM demodulator with a means for analog processing; 
 a digital FM receiver section connected to said FM demodulator with a receiver processor and a music processor, wherein said receiver processor performs receiver digital signal processing and wherein said music processor performs music digital signal processing; and 
 a multiplexer connected to said analog FM signal and said digital FM signal, wherein a multiplexer output generates said audio output. 
 
     
     
       12. The hybrid FM receiver according to  claim 11 , wherein said receiver processor includes a memory means for storing a receiver digital signal processing software. 
     
     
       13. The hybrid FM receiver according to  claim 11 , wherein said receiver processor is programmable and has an external interface for downloading a receiver digital signal processing software. 
     
     
       14. The hybrid FM receiver according to  claim 13 , wherein said receiver digital signal processing software is downloaded using a radio data system (RDS) format. 
     
     
       15. The hybrid FM receiver according to  claim 11 , wherein said music processor includes a memory means for storing a music compressor/decompressor (CODEC). 
     
     
       16. The hybrid FM receiver according to  claim 15 , wherein said music processor is programmable and has an external interface for downloading said music CODEC. 
     
     
       17. The hybrid FM receiver according to  claim 11 , further comprising an output switch for switching between said analog FM signal and said digital FM signal. 
     
     
       18. The hybrid FM receiver according to  claim 11 , further comprising a mixer for mixing said analog FM signal and said digital FM signal to produce said audio output. 
     
     
       19. The hybrid FM receiver according to  claim 11 , wherein said digital FM signal is packetized in an MP3 format. 
     
     
       20. A method for receiving an analog FM signal and a digital FM signal and producing an audio output, the method comprising:
 transmitting, using a transmitter, an audio transmission as a standard analog FM signal and a digital FM signal, wherein the digital FM signal is packetized and transmitted on a subcarrier band, and the analog FM signal is transmitted on a main carrier band;   receiving, using a receiver, the analog FM signal and the digital FM signal, wherein the digital FM signal is decoded and converted to a digital decoded analog FM output and the analog FM signal is processed to provide a standard analog FM output, and wherein the standard analog FM output and the digital decoded analog FM output are synchronized; and   automatically determining, using a processor, the audio output from the digital decoded analog FM output and the standard analog FM output.   
     
     
       21. The method of claim 20, wherein the digital decoded analog FM output is generated using compression/decompression (CODEC). 
     
     
       22. The method of claim 21, wherein the CODEC utilizes a MP3 format. 
     
     
       23. The method of claim 21, further comprising decoding waveforms into digital packets and sending decoded data bits to a CODEC module. 
     
     
       24. The method of claim 23, further comprising determining whether the CODEC module for a particular radio station exists in memory and, if not, downloading the CODEC module. 
     
     
       25. The method of claim 20, wherein automatically determining the audio output comprises determining that the digital FM signal is decoded without errors. 
     
     
       26. The method of claim 20, wherein automatically determining the audio output comprises determining that the digital FM signal is a copy of the analog FM signal. 
     
     
       27. The method of claim 20, wherein automatically determining the audio output occurs after receiving a user input selection. 
     
     
       28. The method of claim 20, wherein converting the digital audio output into the converted analog signal comprises processing the digital audio output using two channels. 
     
     
       29. The method of claim 28, further comprising extracting a data stream from the digital subcarrier signals, wherein extracting the data stream comprises locking in on the data stream, decoding trellis codes in the data stream, and performing error correction.