Unlimited phase tracking delay locked loop

A method of resetting a phase shifter to provide a continuously phase shifted output signal comprising:

• phase shifting, in a phase shifter, said input signal by a phase shift determined by a phase shift reference signal to produce a phase shifted input signal;
• resetting said phase shifter in response to a trigger signal;
• phase shifting, in a fixed phase shifter disposed in parallel with said phase shifter, said input signal by a predetermined fixed phase shift to produce a fixed phase shifted input signal;
• detecting in a threshold detector when said phase shift reference signal reaches a predetermined threshold level, equivalent to the phase shift introduced by said fixed phase shifter and generating in response a switching signal;
• switching at said output, in response to said switching signal, from said phase shifted input signal to said fixed phase shifted input signal for a predetermined period of time, during which time said trigger signal is generated, before switching back to said phase shifted input signal.

A delay locked loop for receiving an input signal, a delay locked loop, having an output for generating an output signal and a second input for receiving a delayed version of output signal, for inserting a delay representative of the delay inserted into the output signal comprising:

• a phase detector, having a first input for receiving said input signal and a second input for receiving said delayed version of the output signal, for generating and outputting at an output a phase shift reference signal representative of the phase difference between said input signal and said delayed version of the output signal;
• a phase shifter, having a first input for receiving said input signal, a second input for receiving said phase shift reference signal and an output for outputting a phase shifted input signal, wherein the phase of the input signal is shifted by a phase shift determined by the phase shift reference signal;
• a resetter, for resetting the phase shift reference signal in response to a trigger signal;
• a fixed phase shifter, for shifting the phase of said input signal by a predetermined phase shift, connected in parallel with said phase shifter, having an input for receiving said input signal and an output for outputting a fixed phase shifted input signal;
• a threshold detector circuit, having an input for receiving said phase shift reference signal and an output for outputting a switching signal when said phase shift reference signal reaches a threshold level, substantially equivalent to the phase shift introduced into said input signal by the fixed phase shifter;
• a bypass circuit, disposed between said phase shifters and said output, having two inputs for receiving, respectively, said phase shifted input signal and said fixed phase shifted signal, a switch for selecting a selected signal from either said phase shifted input signal or said fixed phase shifted signal, an output for outputting said selected signal and means for generating said trigger signal, whereby said switch is responsive to said switching signal to switch from said phase shifted input signal to said fixed phase shifted signal for a predetermined period of time, during which time said trigger signal is generated, before switching back to said phase shifted input signal.

A method of inserting a delay into an input signal to produce an output signal, said delay being representative of a delay inserted into delayed version of the output signal, comprising:

• generating a phase shift reference signal representative of the phase difference between said input signal and said delayed version of said output signal;
• phase shifting in a phase shifter, said input signal by a phase shift determined by the phase shift reference signal to produce a phase shifted input signal;
• resetting said phase shifter in respect to a trigger signal;
• phase shifting, in a fixed phase shifter disposed in parallel with said phase shifter, said input signal by a predetermined fixed phase shift to produce a fixed phase shifted input signal;
• detecting in a threshold detector when said phase shift reference signal reaches a predetermined threshold level, equivalent to the phase shift introduced by said fixed phase shifter and generating in response a switching signal;
• switching at said output, in response to said switching signal, from said phase shifted input signal to said fixed phase shifted input signal for a predetermined period of time, during which time said trigger signal is generated, before switching back to said phase shifted input signal.