System and method for high speed digital data casting concurrent with amplitude modulated broadcasts

摘要

A system and method for transmitting digital information concurrent with a co-existing monophonic amplitude modulated (AM) signal are disclosed. The system allows any AM transmission, in particular commercial AM Radio Broadcasts, to incorporate an orthogonally modulated data signal without significant interference to the ongoing AM broadcast. A high bandwith efficiency modulated data signal is subcarrier modulated (14) onto one or more subcarrier signals. The composite data carrier (22) is then quadrature phase modulated (32, 36) onto the broadcast carrier signal (42, 44, 46) before amplitude modulation. The rate of data transmission, measured in bits-per-second, can be matched to the intended transmission channel (16) and AM modulation characteristics in order to optimize delivery performance and quality of service. In the preferred embodiment, data is phase modulated onto a set of orthogonal base band carrier tones which are then used to angle modulate (54) the RF Carrier. Transmission and receiver methods are disclosed which utilize existing state-of-the-art Compatible Quadrature Amplitude Modulation (C-QUAM) AM Stereo phase modulation Exciter with small modification.