Postcanceling Techniques for Simultaneous Broadcasting of Analog FM and Digital Data

A method for broadcasting digital data simultaneously with analog FM radio is presented. In a standard analog FM receiver, the digital data is not noticed due to the low level and the suppression capability of analog FM. The method is vased on postcanceling of the response of the analog FM on the digital signal at the digital receivers. As a result the capture capability of analog FM is used to guarantee an accurate cancellation of analog FM from the received composite signal. The digital transmission can be based on a typical channel coded scheme for wireless transmission. The postcanceling is based on an Extended Kalman filter approach. We consider a number of cases of transmitted analog to digital signal-to-noise rations of 30 dB to 50 dB. The digital signal recovery appears fairly robust providing a digital signal to noise ratio of 8-12 dB for monophonic FM and 4-6 dB for stereo. The corresponding uncoded error probabilities are 1-2% and 10% respectively at 130 kb/sec.