Automatic frequency control device for tuning an intermediate frequency signal to a target frequency

An automatic frequency control device comprising:

• signal generating means for generating a signal on the basis of a control signal;
• detecting means for detecting a frequency difference of said signal from a target frequency to which a frequency of said signal should be tuned;
• and
• correcting means for correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said detecting means detects said frequency difference,
• wherein said signal generating means comprises:
• control voltage generating means for outputting said control signal as a control voltage;
• reference oscillating means for outputting a reference oscillation signal on the basis of said control voltage;
• local oscillating means for outputting a local oscillation signal synchronous in phase to said reference oscillation signal;
• and
• frequency mixing means for mixing a received signal and said local oscillation signal to thereby output said signal as an intermediate frequency (IF) signal having a frequency intermediate that of said received signal and said local oscillation signal,
• said device further comprising initial value setting means for outputting, in response to a power-up, an initial value which includes a control voltage causing said reference oscillating means to output an intermediate frequency of a range of frequencies which said reference oscillation signal can have.

An automatic frequency control device comprising:

• signal generating means for generating a signal on the basis of a control signal;
• detecting means for detecting a frequency difference of said signal from a target frequency to which a frequency of said signal should be tuned;
• and
• correcting means for correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said detecting means detects said frequency difference,
• wherein said signal generating means comprises:
• control voltage generating means for outputting said control signal as a control voltage;
• reference oscillating means for outputting a reference oscillation signal on the basis of said control voltage;
• local oscillating means for outputting a local oscillation signal synchronous in phase to said reference oscillation signal;
• and
• frequency mixing means for mixing a received signal and said local oscillation signal to thereby output said signal as an intermediate frequency (IF) signal having a frequency intermediate that of said received signal and said local oscillation signal,
• said device further comprising:
• deciding means for determining whether said IF signal has been tuned to said target frequency;
• and
• holding means for holding a control voltage appearing when said deciding means decides that said IF signal has been tuned to said target frequency.

A method of automatically controlling a frequency, comprising steps of:

• (a) generating a signal on the basis of a control signal;
• (b) detecting a frequency difference of said signal from a target frequency to which a frequency of said signal should be tuned;
• and
• (c) correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said frequency difference is detected,
• wherein step (a) comprises:
• (d) outputting said control signal as a control voltage;
• (e) outputting a reference oscillation signal on the basis of said control voltage;
• (f) outputting a local oscillation signal synchronous in phase to said reference oscillation signal;
• and
• (g) mixing a received signal and said local oscillation signal for thereby outputting said signal as an IF signal, and
• wherein step (c) comprises:
• (j) multiplying the difference of the frequency of said IF signal from said target frequency by a reciprocal of a gradient of said control voltage relative to the frequency of said IF signal in said proportional relation;
• and
• (k) adding a product produced in step (j) to said control voltage.

A method of automatically controlling a frequency, comprising steps of:

• (a) generating a signal on the basis of a control signal;
• (b) detecting a frequency difference of said signal from a target frequency to which a frequency of said signal should be tuned;
• and
• (c) correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said frequency difference is detected,
• wherein step (a) comprises:
• (d) outputting said control signal as a control voltage;
• (e) outputting a reference oscillation signal on the basis of said control voltage;
• (f) outputting a local oscillation signal synchronous in phase to said reference oscillation signal;
• and
• (g) mixing a received signal and said local oscillation signal for thereby outputting said signal as an IF signal,
• said method further comprising:
• (l) outputting, in response to a power-up, an intermediate frequency of a range of frequencies which said reference oscillation signal can have.

A method of automatically controlling a frequency, comprising steps of:

• (a) generating a signal on the basis of a control signal;
• (b) detecting a frequency difference of said signal from a target frequency to which a frequency of said signal should be tuned;
• and
• (c) correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said frequency difference is detected,
• wherein step (a) comprises:
• (d) outputting said control signal as a control voltage;
• (e) outputting a reference oscillation signal on the basis of said control voltage;
• (f) outputting a local oscillation signal synchronous in phase to said reference oscillation signal;
• and
• (g) mixing a received signal and said local oscillation signal for thereby outputting said signal as an IF signal,
• said method further comprising:
• (m) determining whether said IF signal has been tuned to said target frequency;
• and
• (n) holding a control voltage appearing when said IF signal is tuned to said target frequency.

An automatic frequency control device comprising:

• signal generating means for generating a signal on the basis of a control signal;
• detecting means for detecting a frequency difference of said signal from a target frequency to which a frequency of said signal should be tuned;
• and
• correcting means for correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said detecting means detects said frequency difference,
• wherein said correcting means includes:
• multiplying means for multiplying said difference between said signal and said target frequency by a reciprocal of a gradient of said control voltage relative to a predetermined frequency;
• and
• adding means for adding a product, produced by said multiplying means, to said control voltage.

A method of automatically controlling a frequency, comprising steps of:

• (a) generating a signal on the basis of a control signal;
• (b) detecting a frequency difference between said signal and a target frequency to which a frequency of said signal should be tuned;
• and
• (c) correcting said control signal on the basis of a proportional relation between said control signal and said frequency of said signal when said frequency difference is detected,
• wherein step (a) comprises:
• (d) outputting said control signal as a control voltage;
• (e) outputting a reference oscillation signal on the basis of said control voltage;
• (f) outputting a local oscillation signal synchronous in phase to said reference oscillation signal;
• and
• (g) mixing a received signal and said local oscillation signal for thereby outputting said signal as an IF signal,
• wherein step (c) includes:
• multiplying the difference of the frequency of said IF signal from said target frequency by a reciprocal of a gradient of said control voltage relative to the frequency of said IF signal.