Modulation & demodulation of GPS output digital data

[nauman]

Hi all

I need to add GPS digital output (in form of Lat/Long) in an existing analog audio signal whose bandwidth is 100 Hz-20 KHz. This GPS data should be added in such a way that it should not interfere with audio signal neither total bandwidth of analog signal should exceed 40 KHz. This implies that GPS data should lie within 20 KHz-40 KHz bandwidth.

One way to add GPS digital data in analog signal may be to modulate it (e.g. FSK/PSK) in frequency range of 20 KHz - 40 KHz and then add this modulated signal in existing analog audio signal.

Kindly guide me if there is any COTs solution available which can be used for this purpose? Thanks

Note: A solution is also required on receiving end where audio and GPS data are being separated and modulated GPS data is also converted back into digital Lat/Long data.

 

[berkeman]

How quickly is the GPS data changing? What does the analog TX and RX circuitry look like? What limits the existing circuitry to the 100Hz-20kHz range? It may be non-trivial to try to add in an out-of-band signal, depending on the hardware you have there now.

If you need to update the hardware to accommodate the wider signal bandwidth, have you considered switching to an all-digital solution?

 

[Borek]

I wonder if some variant of https://en.wikipedia.org/wiki/Radio_Data_System won't fit your needs? There are ready single chip solutions, so it can be easy to implement.

 

[Averagesupernova]

What needs to be known is the bandwidth of the baseband signal containing the GPS data. @Borek is on the right track. @berkeman asked a very good question as well concerning how often the data changes which translates to how often do you need to send the data which can translate into how fast does the data need to be sent and ultimately how little bandwidth the signal could get by with.

 

[nauman]

How quickly is the GPS data changing?

GPS data needs to be send after every 3 to 4 seconds

 

[nauman]

What limits the existing circuitry to the 100Hz-20kHz range?

The existing circuitry is designed for audio frequency range only

 

[Baluncore]

Take the NMEA string from a GPS receiver, at 4800 baud. Phase modulate that onto a sub-carrier, that is above the audio pass-band. Use a low-pass filter to remove the sub-carrier and data from the audio output.

Lock a PLL to the sub-carrier and data, then phase detect the NMEA data.

 

[nauman]

Take the NMEA string from a GPS receiver, at 4800 baud. Phase modulate that onto a sub-carrier, that is above the audio pass-band. Use a low-pass filter to remove the sub-carrier and data from the audio output.

Lock a PLL to the sub-carrier and data, then phase detect the NMEA data.

Thanks for help. Is there any micro controller/ICs which can do these tasks?

 

[Baluncore]

Start reading here;
https://docs.arduino.cc/learn/communication/gps-nmea-data-101/

 

[Dullard]

I think you mean "Position Data." "GPS Data" is a term typically reserved (maybe just me?) for the 50 BPS information encoded in the L-Band signals from GPS spacecraft. /Hairsplit

 

[nauman]

I think you mean "Position Data." "GPS Data" is a term typically reserved (maybe just me?) for the 50 BPS information encoded in the L-Band signals from GPS spacecraft. /Hairsplit

Yes, i meant Lat/Long data in digital format