Method of and apparatus for automatic frequency control range extension

An apparatus for AFC range extension, the apparatus comprising:

• a receive section to receive communication signals, the receive section including a plurality of programmable filters;
• a control section coupled to the receive section, the control section to set the receive section to have a first bandwidth prior to receiving a first one of the communication signals and to set the receive section to have a second bandwidth different from the first bandwidth setting when frequency error in the first one of the communication signals is below a first threshold and
• a reference oscillator coupled to the receive section and the control section,
• wherein the plurality of programmable filters are capable of passing the first one of the communication signals when the reference oscillator is in maximum frequency error, the first one of the communication signals being a signal used for AFC, and the plurality of programmable filters are capable of passing a second one of the communication signals without substantial adjacent channel noise when the reference oscillator has frequency error below a second threshold.

A radiotelephone comprising:

• an antenna;
• a transmit section coupled to the antenna;
• a synthesizer section coupled to the transmit section, the synthesizer section including a reference oscillator, the reference oscillator including a crystal with low accuracy, the reference oscillator to generate a reference signal having a frequency based on the crystal, the reference oscillator to adjust the frequency of the reference signal according to a AFC setting signal;
• a receive section coupled to the antenna and the synthesizer section, the receive section including a receive front end to receive communication signals from the antenna and an intermediate frequency (IF) section to demodulate the received communication signals, the IF section including a plurality of low pass filters with a programmable bandwidth and a bandwidth control circuit coupled to each of the plurality of low pass filters and the reference oscillator, the bandwidth control circuit to set the programmable bandwidth of the plurality of low pass filters according to the reference signal and a bandwidth setting signal;
• and
• a control section coupled to the transmit section, the reference oscillator of the synthesizer section and the bandwidth control circuit of the IF section, the control section to generate the bandwidth setting signal so as to set the programmable bandwidth of the plurality of low pass filters to a wide setting to facilitate reception of one of the communication signals used for AFC, and the control section to generate the bandwidth setting signal so as to set the programmable bandwidth of the plurality of low pass filters to a narrow setting so as to facilitate reception of the other ones of the communication signals without substantial adjacent channel noise once frequency error of the one of the communication signals used for AFC is below a threshold.