Hybrid phase locked loop

A second order feedback system whose natural frequency scales with its output and whose damping factor remains constant, comprising:

• a filter circuit having a scaling channel for scaling a phase error to obtain a scaled phase error;
• an integrating channel for integrating the phase error to obtain an integrated phase error;
• and a summing circuit for combining the scaled phase error and the integrated phase error;
• an integrator circuit, responsive to said summing circuit to produce an output signal, the gain of said integrator circuit being proportional to the output signal;
• and
• a control circuit including a feedback loop for controlling the gain of said integrating channel proportional to the output signal and for maintaining constant the ratio of and scaling the product of the unity gain frequency and the zero frequency of the feedback system to keep constant the damping factor and to scale the natural frequency of the feedback system with said output signal, respectively.

A phase locked loop (PLL) system whose natural frequency scales with an output clock frequency of a voltage controlled oscillator (VCO) and whose damping factor remains constant, comprising:

• a filter circuit having a scaling channel for scaling a phase error to obtain a scaled phase error, an integrating channel for integrating the phase error to obtain an integrated phase error and a summing circuit for combining the scaled phase error and the integrated phase error;
• the VCO being responsive to said summing circuit to produce the output clock frequency, said VCO having a gain that is proportional to its output clock frequency;
• and
• means for controlling the gain of said integrating channel proportional to the output clock frequency of said VCO and maintaining constant the ratio of and scaling the product of, the unity gain frequency and the zero frequency of the PLL to keep constant the damping factor and to scale the natural frequency of the PLL with the output clock frequency of the VCO, respectively.

A second order feedback system whose natural frequency scales with its output and whose damping factor remains constant, comprising:

• a filter circuit having a scaling channel for scaling a phase error to obtain a scaled phase error, an integrating channel for integrating the phase error to obtain an integrated phase error and a summing circuit for combining the scaled phase error and the integrated phase error;
• an integrator circuit, responsive to said summing circuit, to produce an output signal, the gain of said integrator circuit being proportional to the output signal;
• and
• means for controlling the gain of said integrating channel proportional to the output signal and for maintaining constant the ratio of and scaling the product of the unity gain frequency and the zero frequency of the feedback system to keep constant the damping factor and to scale the natural frequency of the feedback system with said output signal, respectively.