Abstract: A radio receiver may determine whether a received frequency modulated radio signal includes interference from an adjacent channel. The receiver may compare a frequency deviation above the center frequency of the received signal to a frequency deviation below the center frequency of the received signal. The receiver determines that the radio signal is affected by adjacent channel noise when the frequency deviation below the center frequency is substantially different from the frequency deviation above the center frequency. Alternatively, the presence of noise from an adjacent channel may be detected by comparing a positive amplitude and a negative amplitude of a demodulated version of the frequency modulated radio signal. In this alternative, the receiver determines that the radio signal is affected by adjacent channel noise when the extent of the positive amplitude is substantially different from the extent of the negative amplitude.

Abstract: A system for decoding data, such as travel and traffic information, configured in data blocks embedded in an electromagnetic signal, such as a broadcasted radio signal, has been developed. The system includes a method and receiver for decoding the data with a background tuner in a manner that does not impair the ability of the background tuner to demodulate other signals. While a main tuner is tuned to demodulate a first electromagnetic signal to produce a data stream, the background tuner is switched to decode the data blocks only when the data blocks are expected to be received. In the remaining time, the background tuner is free to demodulate other signals to support a diversity or other function. If a data block is not received, or not received when expected, the background tuner returns to demodulating one or more other frequencies after a predetermined time interval has elapsed.