System and method for coarse/fine PLL adjustment

A method of tuning a receiver that maintains a signal output from the receiver during the tuning process comprising:

• selecting a channel to be tuned;
• tuning the channel to approximately a desired first intermediate frequency by a frequency source that is adjustable in coarse steps;
• bandpass filtering the channel at the desired first intermediate frequency so as to pass the channel and a portion of another channel;
• tuning the channel at the first intermediate frequency to a second intermediate frequency by a frequency source that is adjustable in fine steps;
• and
• tuning the channel at the second intermediate frequency to a third intermediate frequency by a direct synthesis frequency source having a divider circuit to produce an output frequency that is in a fixed relationship to the frequency source adjustable in fine steps.

A method of tuning a receiver, comprising:

• selecting a desired channel to be tuned;
• tuning the desired channel to approximately a desired first intermediate frequency by using a first phase lock loop that is adjustable in coarse frequency steps and having a wide bandwidth;
• filtering the desired channel at the desired first intermediate frequency in a bandpass filter having passband, the passband being wide enough to accommodate any frequency error of the desired channel relative to the desired first intermediate frequency that is caused by the coarse frequency steps;
• and
• tuning the desired channel at the first intermediate frequency to a second intermediate frequency by a second phase lock loop that is adjustable in fine frequency steps and having a narrow bandwidth relative to the wide bandwidth of the first phase lock loop;
• wherein the tuning steps are performed in accordance with the following equation:
• FLO1−FSIG−(5/4*FLO2)=Fif,
• where
• FLO1 is the frequency of the first phase lock loop,
• FLO2 is the frequency of the second phase lock loop,
• Fif is the second intermediate frequency, and
• FSIG is the frequency of the desired channel to be tuned.