Patent ID: 6898249

Claim:
A method of in-band on-channel digital audio broadcasting comprising the steps of: providing an analog modulated carrier signal in a central frequency band of an AM radio channel; providing a first plurality of subcarriers in an upper sideband of the AM radio channel; providing a second plurality of subcarriers in a lower sideband of the AM radio channel; providing a third plurality of subcarriers in the central frequency band of the AM radio channel; modulating the first, second and third plurality of subcarriers with one or more digitally encoded signals; and transmitting the analog modulated signal and the first, second and third plurality of subcarriers; wherein the subcarriers in the third plurality of subcarriers that are positioned closest to the center of the channel are transmitted at higher power spectral densities than the subcarriers in the third plurality of subcarriers that are positioned farther from the center of the channel, and wherein the power spectral densities of a first group of the subcarriers in the third plurality of subcarriers decrease linearly with frequency separation from the center of the channel.