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System, method and emulation circuitry useful for adjusting a characteristic of a periodic signal

  • US 8,664,986 B2
  • Filed: 07/09/2012
  • Issued: 03/04/2014
  • Est. Priority Date: 07/28/2011
  • Status: Active Grant
First Claim
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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:

  • 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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