System, method and emulation circuitry useful for adjusting a characteristic of a periodic signal
First Claim
1. A method of changing the phase or frequency of a first periodic signal output from a first nonlinear device having a nonlinear impedance characteristic with respect to a second periodic signal, the first nonlinear device having a voltage operating range, the method comprising:
- providing discrete control signal types of variable time width in proportion to a phase difference between the first and second signals, a first type of the discrete control signal types indicative of a negative difference in phase or frequency of the first periodic signal relative to the phase or frequency of the second periodic signal, and a second type of the discrete control signal types indicative of a positive difference in phase or frequency of the first periodic signal relative to the phase or frequency of the second periodic signal;
periodically applying control signals of the first type to a first switching device to control current flow along a first circuit path from a voltage source through the first switching device, through the first nonlinear device and to a reference voltage terminal to adjust a phase or frequency characteristic of the first periodic signal output from the first nonlinear device; and
periodically applying signals of the second type to a second switching circuitry to control current flow along a second circuit path in parallel with the first circuit path from the voltage source through the second switching device, through a second impedance device having a nonlinear impedance characteristic and to the reference voltage terminal,wherein the first and second switching devices are operated in to response to variations in the signals of the first and second types to switch current flow between the first and second circuit paths so that at times current flows only through the first circuit path and then only through the second circuit path, wherein;
the first nonlinear device does not incorporate a charge pump circuitry to store charge in a capacitor for input to the voltage controlled oscillator (VCO);
impedance characteristics of the first nonlinear device and the second nonlinear impedance device are so matched that current-voltage characteristics of the first nonlinear device and the second impedance device are within five percent of one another throughout the voltage operating range of the VCO;
the first circuit path includes a first load device comprising three stage inverter ring oscillator; and
the second circuit path includes a second load device which is a sub circuit having characteristics which track the impedance characteristics of the VCO.
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Abstract
Systems, methods and circuitry useful for adjusting a periodic signal such as with a voltage controlled oscillator or a delay line. In one series of embodiments, circuits and methods are provided for controlling current flow through first and second parallel paths where an impedance device in one path emulates the impedance characteristics of a different device in the other path. A phase or frequency characteristic of the periodic signal may be adjusted by alternate switching of current through the two paths.
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Citations
17 Claims
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1. A method of changing the phase or frequency of a first periodic signal output from a first nonlinear device having a nonlinear impedance characteristic with respect to a second periodic signal, the first nonlinear device having a voltage operating range, the method comprising:
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providing discrete control signal types of variable time width in proportion to a phase difference between the first and second signals, a first type of the discrete control signal types indicative of a negative difference in phase or frequency of the first periodic signal relative to the phase or frequency of the second periodic signal, and a second type of the discrete control signal types indicative of a positive difference in phase or frequency of the first periodic signal relative to the phase or frequency of the second periodic signal; periodically applying control signals of the first type to a first switching device to control current flow along a first circuit path from a voltage source through the first switching device, through the first nonlinear device and to a reference voltage terminal to adjust a phase or frequency characteristic of the first periodic signal output from the first nonlinear device; and periodically applying signals of the second type to a second switching circuitry to control current flow along a second circuit path in parallel with the first circuit path from the voltage source through the second switching device, through a second impedance device having a nonlinear impedance characteristic and to the reference voltage terminal, wherein the first and second switching devices are operated in to response to variations in the signals of the first and second types to switch current flow between the first and second circuit paths so that at times current flows only through the first circuit path and then only through the second circuit path, wherein; the first nonlinear device does not incorporate a charge pump circuitry to store charge in a capacitor for input to the voltage controlled oscillator (VCO); impedance characteristics of the first nonlinear device and the second nonlinear impedance device are so matched that current-voltage characteristics of the first nonlinear device and the second impedance device are within five percent of one another throughout the voltage operating range of the VCO; the first circuit path includes a first load device comprising three stage inverter ring oscillator; and the second circuit path includes a second load device which is a sub circuit having characteristics which track the impedance characteristics of the VCO. - View Dependent Claims (2, 3)
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4. A system comprising proportional path circuitry for use in changing the phase or frequency of a first periodic signal with respect to a second periodic signal based on an output from a comparator, the system comprising:
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a detector for determining a phase or frequency difference between the first and second periodic signals, which provides discrete periodic signal types of variable time width in proportion to a phase difference between the first and second periodic signals, a first type of the discrete periodic signal types indicative of a negative difference in phase or frequency of the first periodic signal relative to the phase or frequency of the second periodic signal, and a second type of the discrete periodic signal types indicative of a positive difference in phase or frequency of the first periodic signal relative to the phase or frequency of the second periodic signal; switching circuitry including first and second parallel branches, each parallel branch coupled between a supply voltage connection, VDD, and a reference voltage connection, VSS, each parallel branch including a first switching device and a load device, the first switching device of the first parallel branch and the first switching device of the second parallel branch each coupled to receive a different one of the discrete periodic signal types as an input signal to place the first switching device in a mode to conduct current between the supply voltage connection and the reference voltage connection or in a non-conducting mode wherein, during circuit operation, to change the phase or frequency of the first periodic signal, with application of the signal types to the switching devices;
during a portion Δ
t of a period of the first or second periodic signal, one of the switching devices is in a conduction mode while the other switching device is not in a conduction mode, thereby providing current flow only through the load device of the first parallel branch or providing current flow only through the load device of the second parallel branch or providing no current flow through either load device,wherein the first load device comprises a three stage inverter ring oscillator and the second load device comprises a sub circuit having characteristics which track the impedance characteristics of the oscillator. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A circuit suitable for tracking impedance characteristics of an oscillator comprising a first PMOS FET, a second PMOS FET, a first NMOS FET and a second NMOS FET wherein:
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the first PMOS FET has a gate region connected to receive a reference voltage; the second NMOS FET has a gate region connected to receive a supply voltage level; the second PMOS FET has a gate region connected to a node between the first and second NMOS FETs; and the first NMOS FET has a gate region connected to a node between the first and second PMOS FETs, wherein the oscillator is a three stage inverter ring oscillator and the first PMOS FET and the second NMOS FET operate in a triode mode, which corresponds to the impedances of FET transistors in the oscillator that are fully switched when associated gate bias voltage is at the supply voltage level or the reference level (ground) while the second PMOS FET and the first NMOS FET operate in the saturation mode which corresponds to the impedances of FET transistors in the oscillator that are partially switched on when associated gates are biased at a voltage between the supply voltage level and the reference level.
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Specification