Host rejection filtering in a digital audio broadcasting system

Abstract

A digital receiver for receiving an analog host signal with one or more digital sidebands includes a bandreject filter arranged at least in part in an intermediate frequency (IF) processing stage of the receiver. In an illustrative embodiment, first and second digital sidebands are transmitted on either side of a frequency modulated (FM) analog host signal in a hybrid in-band on-channel (HIBOC) digital audio broadcasting (DAB) system. The received composite signal is filtered in the IF processing stage of the receiver by the bandreject filter in order to substantially attenuate the analog host signal while passing the digital sidebands. The bandreject filter may be arranged in the IF processing stage so as to filter the analog host signal from the composite signal at a point prior to an input of an automatic gain control (AGC) circuit, such that the AGC operating point is determined primarily by the digital sidebands. The bandreject filter may have a group delay characteristic for a portion of a frequency spectrum associated with the digital sidebands that is selected to equalize a corresponding group delay characteristic for a signal path of the receiver.