Common intermediate frequency broadcast radio front end

A method to receive and process AM and FM radio signals, comprising the steps of:

• selectively receiving one of an AM and an FM signal in response to the selection of an AM receiver mode and an FM receiver mode;
• mixing and bandpass filtering the AM and FM signals, the resultant signals having a first center frequency for FM signals and a second center frequency for AM signals that differs from the first center frequency, but which is passed through the same IF filter and in which the second center frequency is offset from the first center frequency by a fixed amount;
• and
• mixing the FM first center frequency and the AM second center frequency with a common signal resulting in a third center frequency for FM operation and a fourth center frequency for AM operation which are passed through the same path and which operate at a fixed offset.

A front end of an FM/AM radio receiver, comprising:

• a first mixer that mixes a received AM signal with a first signal when the receiver is selected to be in an AM receive mode;
• a second mixer that mixes a received FM signal with a second signal when the receiver is selected to be in an FM receive mode;
• a bandpass filter coupled to each of the first mixer and the second mixer that respectively bandpass filters outputs of the first mixer and the second mixer, the bandpass filter provides a filtered intermediate signal;
• a third mixer coupled to the bandpass filter, the same third mixer being used to process the filtered intermediate signal when the filtered intermediate signal has a frequency in either an AM frequency range or an FM frequency range;
• and
• a synthesizer circuit that provides a signal to produce a center frequency for the third mixer, the center frequency being substantially 450 kHz in the AM mode and substantially 460 kHz in the FM mode.