Phase locked loop with digital vernier control
First Claim
Patent Images
1. A frequency synthesizer, comprising:
- a phase locked loop circuit that includes a first voltage controlled oscillator;
a sample port connected to export a control-voltage measurement obtained at a first control input of said first voltage controlled oscillator;
a second voltage controlled oscillator having a second control input connected to receive said control-voltage measurement from said sample port and providing for an open-loop reference frequency signal that is stabilized by the phase locked loop circuit on an output port; and
a vernier unit for injecting an analog signal into said second control input of said second voltage controlled oscillator;
wherein, a fractional frequency adjustment of said open-loop reference frequency signal made in proportion to said analog signal injected into said second control input, and the second voltage controlled oscillator operates at a stable offset frequency from that of the first voltage controlled oscillator.
2 Assignments
0 Petitions
Accused Products
Abstract
A phase-locked-loop-stabilized voltage controlled oscillator relies on a sampling of the analog-frequency-control voltage of a voltage-controlled oscillator in a phase-locked-loop circuit to act as a reference voltage for a second free-running voltage-controlled oscillator. A vernier-adjustment voltage is injected into the control input of the second voltage-controlled oscillator to produce a finely variable derivative frequency not otherwise producible by a conventional phase-locked-loop circuit.
14 Citations
5 Claims
-
1. A frequency synthesizer, comprising:
-
a phase locked loop circuit that includes a first voltage controlled oscillator; a sample port connected to export a control-voltage measurement obtained at a first control input of said first voltage controlled oscillator; a second voltage controlled oscillator having a second control input connected to receive said control-voltage measurement from said sample port and providing for an open-loop reference frequency signal that is stabilized by the phase locked loop circuit on an output port; and a vernier unit for injecting an analog signal into said second control input of said second voltage controlled oscillator; wherein, a fractional frequency adjustment of said open-loop reference frequency signal made in proportion to said analog signal injected into said second control input, and the second voltage controlled oscillator operates at a stable offset frequency from that of the first voltage controlled oscillator. - View Dependent Claims (2, 3, 4)
-
-
5. A frequency synthesizer, comprising:
-
a phase locked loop circuit that includes a first voltage controlled oscillator; an external reference source connected to provide a reference clock input to the phase locked loop; a sample port connected to export a control-voltage measurement obtained at a first control input of said first voltage controlled oscillator; a second voltage controlled oscillator having a second control input connected to receive said control-voltage measurement from said sample port and providing for an open-loop reference frequency signal that is stabilized by the phase locked loop circuit on an output port; a vernier unit for injecting an analog signal into said second control input of said second voltage controlled oscillator, wherein, a fractional frequency adjustment of said open-loop reference frequency signal is made in proportion to said analog signal injected into said second control input, and the second voltage controlled oscillator operates at a stable offset frequency from that of the first voltage controlled oscillator; a vernier digital-to-analog converter (V-DAC) disposed within the vernier unit and connected to produce said analog signal injected into said second control input from a vernier digital input word; an "M bit" digital-to-analog converter (M-DAC) connected to add an 2M -component analog baseline to said analog signal injected into said second control input from an "M" digital input word; an "N bit" digital-to-analog converter (N-DAC) connected to add an 2N -component analog baseline to said analog signal injected into said second control input from an "N" digital input word; a digital divider connected between the external reference source and a phase detector included in the phase locked loop, and including an input to receive an "N" digital input word; and a digital divider connected between the first voltage controlled oscillator and a phase detector included in the phase locked loop, and including an input to receive an "M" digital input word.
-
Specification