Microprocessor controlled tuning system
AssigneeArvin Industries, Inc.
InventorNathan E. Manlove
Life of this patent
Estimating the term…
Abstract
A tuning system receives signals from a radio frequency source and supplies an intermediate frequency signal to a signal detector under the control of a microprocessor. The microprocessor reads a channel selector and produces a control voltage which is used to tune the system to the selected channel. The intermediate frequency signal is connected to the microprocessor and a direct measure of the actual IF signal frequency is used by the processor to continuously adjust the tuner to compensate for drifting of the RF signal. In a preferred embodiment, the IF signal increments a counter in the microprocessor for a predetermined period of time to provide a direct measure of the actual IF signal frequency.
Claims19
A microprocessor controlled phase locked loop tuning system, comprising:
- a phase locked loop controlled by a microprocessor,
- means responsive to a user input channel selection to produce an output and to supply said output to a programmable frequency divider in the phase locked loop which determines a nominal operating frequency of a local oscillator in tuner, said tuner including a mixer for combining a radio frequency input signal with a signal form the local oscillator to produce an intermediate frequency signal which is supplied to a signal detector;
- means for connecting the intermediate frequency signal to a counting register to provide a direct measure of the actual frequency of the intermediate frequency signal, and means for supplying said direct measure of frequency to the microprocessor;
- and
- means for adjusting the output supplied to the programmable frequency divider when the measured frequency of the intermediate frequency signal is outside a predetemined frequency range.
A microprocessor controlled phase locked loop tuning system, comprising:
- a phase locked loop controlled by a microprocessor,
- means responsive to a user input channel selection to produce an output and to supply said output to a programmable frequency divider in the phase locked loop which determines a nominal operating frequency of a local oscillator in a tuner, said tuner including a mixer for combining a radio frequency input signal with a signal from the local oscillator to produce an intermediate frequency signal which is supplied to a signal detector;
- means for connecting the intermediate frequency signal to a counting register in the microprocessor;
- means for periodically resetting said register and for reading the contents thereof after a predetermined time period to provide a direct measure of the actual frequency of the intermediate frequency signal;
- and
- means for adjusting the output supplied to the programmable frequency divider when the measured frequency of the intermediate frequency signal is above or below a predetermined frequency range.
A method for tuning a microprocessor controlled phase locked loop tuning system having a microprocessor which is responsive to a user input channel selection to produce an output associated with said selection and to supply said output to a programmable frequency divider in the phase locked loop which determines a nominal frequency of a local oscillator in a tuner, said tuner including a mixer for combining a radio frequency input signal with a signal from the local oscillator to produce an intermediate frequency signal which is supplied to a signal detector, comprising the steps of:
- (a) reading the user input channel selection;
- (b) setting the output to the programmable frequency divider to a value associated with the selected channel;
- (c) taking a direct measure of the actual frequency of the intermediate frequency signal;
- (d) comparing the actual frequency measured in step (c) with a predetermined range of frequencies for the intermediate frequency signal;
- and
- (e) adjusting the output to the programmable frequency divider if the actual frequency determined in step (c) is above or below the predetermined frequency range.
A microprocessor controlled tuning system, comprising:
- a tuner for receiving information bearing radio frequency signals and for producing an intermeidate frequency signal to serve as a carrier for said information bearing signals;
- means for connecting the intermediate frequency signal to a microprocessor and for directly measuring the actual frequency of the intermediate freqeuncy signal;
- and
- means for adjusting the tuner to compensate for variations in the actual frequency of the intermediate frequency signal caused by drifting of the information bearing radio frequency signal.
A digitally controlled tuning system, comprising:
- a superheterodyne tuner having an input coupled to a source of RF signals, an output at which an IF signal is produced, and a variable frequency local oscillator for selecting the RF signal to which the tuning system is tuned;
- digital control means for controlling the frequency of the local oscillator to tune the tuning system to one of the RF signals;
- means for coupling the digital control means to the local oscillator;
- the digital control means including means for generating a digital value directly representative of the frequency of the IF signal;
- means for coupling the digital control means to the output of the tuner;
- and
- the digital control means including means for storing upper and lower limits, means for comparing the digital value representative of the frequency of the IF signal to the upper and lower limits and causing the local oscillator control means to adjust the frequency of the local oscillator when the digital value representative of the frequency of the IF signal does not fall within the upper and lower limits.
Dependencies are inferred from the claim text.