FSK modulation using switched outputs of two oscillators
AssigneePhillips Petroleum Company
InventorJerry J. Norton
Life of this patent
Estimating the term…
Abstract
Two oscillators are utilized to convert digital data into an FSK modulated signal. One oscillator is at the mark frequency and the other is at the space frequency. FSK modulation is accomplished by switching between the two frequencies based on the state of the digital data. Phase and frequency shifting techniques are also provided to insure that a desired difference between the mark frequency and space frequency is maintained and to also insure that a proper phase relationship is maintained between the output from the two oscillators.
Claims8
Apparatus comprising:
- a reference oscillator, wherein said reference oscillator provides a first signal having a first frequency;
- a voltage controlled oscillator, wherein said voltage controlled oscillator provides a second signal having a second frequency which is different from said first frequency;
- means for switching between said first signal and said second signal to establish a FSK modulated signal;
- means for controlling said means for switching in response to the state of a digital data signal and in response to a data clock;
- means for establishing a difference signal which has a frequency equal to the difference between the frequency of said first signal and the frequency of said second signal;
- and
- means for controlling said voltage controlled oscillator so that said difference signal is in phase with said data clock.
A method for converting a digital data signal into an FSK modulated signal, said method comprising the steps of:
- switching between a first signal having a first frequency and a second signal having a second frequency, which is different from said first frequency, in response to the state of said digital data signal and in response to a data clock to establish said FSK modulated signal, wherein said first signal is established by a reference oscillator and said second signal is established by a voltage controlled oscillator;
- establishing a difference signal which has a frequency equal to the difference between the frequency of said first signal and the frequency of said second signal;
- and
- controlling said voltage controlled oscillator so that said difference signal is in phase with said data clock.
Dependencies are inferred from the claim text.