DIGITAL AUDIO BROADCAST DEVICES

摘要

The present invention provides a number of improvements to Digital Audio Broadcast modules. In particular the invention seeks to provides a lower cost mobile DAB module, which has lower power consumption and is portable. In one aspect of the invention, a DAB receiver circuit comprises signal processing means including a variable radio frequency (RF) filter having a variable pass-band position; and a control circuit; wherein, in use, a controlling means is periodically increased or decreased to move the pass-band position a predetermined amount from an initial position to a new position; the control circuit is adapted to make a signal quality determination at the new position and make a comparison between the signal quality at the new position and a signal quality at the initial position; and the control circuit either increases or decreases the controlling means in dependence on the comparison in order to improve signal quality. This technique helps to overcome the need for expensive parts such as close tolerance varactor diodes in the tracking filters, and helps to improve the reliability of the centririg of the voltage tuned band pass tracking filters, particularly in the presence of variations due to temperature and aging.