Abstract: A frequency divider is provided which uses common circuitry to switch between different duty cycle outputs. The divider has one or more memory elements with a feedback loop and which are controllable to adjust a duty cycle of an output signal. Each memory element has a first regenerative cell and a second regenerative cell, and where one of the regenerative cells is a controllable regenerative cell which can be controlled to vary the duty cycle of an output of the frequency divider circuit. The controllable regenerative cell can be selectively activated so that in a first configuration where the controllable regenerative cell is activated an output of the frequency divider circuit has a first duty cycle and in a second configuration where the controllable regenerative cell is deactivated an output of the frequency divider circuit has a second duty cycle.

Abstract: A method for constructing a phase locked loop begins with determining spurious frequency component criteria permitted within the PLL. A PLL filter prototype is selected with a desired settling time. A transfer function is generated based on the PLL transfer function that predicts the spurious components. A maximum level of the spurious components produced in the PLL is determined based on the maximum frequency step. If the maximum level of the spurious frequency components produced is too large, the order variable is incremented and the PLL transfer function is determined until the transfer function produces the spurious frequency components that meet the requirements. The components for a loop filter are selected based on the selected PLL transfer function. The adjustable frequency source tuning gain, the phase detector gain, the loop filter gain, and the divide factor are chosen to meet the requirements of the PLL transfer function.

Abstract: A method for constructing a phase locked loop begins with determining spurious frequency component criteria permitted within the PLL. A PLL filter prototype is selected with a desired settling time. A transfer function is generated based on the PLL transfer function that predicts the spurious components. A maximum level of the spurious components produced in the PLL is determined based on the maximum frequency step. If the maximum level of the spurious frequency components produced is too large, the order variable is incremented and the PLL transfer function is determined until the transfer function produces the spurious frequency components that meet the requirements. The components for a loop filter are selected based on the selected PLL transfer function. The adjustable frequency source tuning gain, the phase detector gain, the loop filter gain, and the divide factor are chosen to meet the requirements of the PLL transfer function.