High resolution time-to-digital converter
AssigneeVector 12 Corporation
InventorsSassan Tabatabaei, Andre Ivanov
Life of this patent
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Abstract
A time to digital converter (TDC) has a pair of digital oscillators. The periods of the oscillators differ by TΔ. The oscillators are triggered by START and STOP pulses. A counter counts a number of pulses until reference points on the signals output by the oscillators coincide. Measurements may be made using a dual resolution method. Intrinsic jitter of the TDC can be determined by comparing sets of measurements in which the switch in resolutions is made at different points. A range extender circuit may be provided to extend a valid measurement range of the TDC.
Claims115
A time to digital converter comprising:
- a timing circuit comprising first and second digital oscillators producing first and second clock signals respectively, the first and second oscillators having different periods;
- at least one of the oscillators comprising a plurality of controllable delay elements, the delay elements, when activated, altering the period of the oscillator;
- a coincidence detector connected to generate a coincidence signal when a reference point in the first clock signal has a known time relationship to a corresponding reference point on the second clock signal;
- a first counter connected to count a number, N, of cycles of the first oscillator until the coincidence detector generates the coincidence signal;
- and,
- a resolution adjustment circuit connected to start the first and second oscillators at times separated by a known interval, compare the number N to a threshold and, if N is not at least equal to a threshold value altering the period of at least one of the oscillators by activating or deactivating one or more of the controllable delay elements.
A time to digital converter comprising:
- a timing circuit comprising first and second digital oscillators producing first and second clock signals respectively, the timing circuit switchable between a plurality of states including a first state wherein a difference in periods of the first and second signals is TΔ1 and a second state wherein a difference in periods of the first and second signals is TΔ2 where TΔ2<TΔ1;
- a resolution switching control circuit connected to switch the timing circuit between its states when a reference point of the first clock signal approaches a first predetermined time relationship with a corresponding reference point of the second clock signal;
- a coincidence detector connected to generate a coincidence signal when the reference point in the first clock signal has a second predetermined time relationship to the corresponding reference point on the second clock signal;
- a first counter connected to count a number (NF) of edges of the first clock signal between a time when the timing circuit is switched into its second state and the time when the coincidence signal is generated;
- and, a second counter connected to count a number (NC) of edges of the first signal between a START signal and a time when the timing circuit is switched out of its first state.
A time to digital converter comprising:
- means for generating first and second clock signals respectively having first and second periods;
- means for varying at least one of the first and second periods to reduce a difference between the first and second periods from a first value TΔ1 to a second value TΔ2 where TΔ2<TΔ1;
- means for operating the means for varying the at least one of the first and second periods when a reference point in the first clock signal has a known time relationship to a corresponding reference point on the second clock signal;
- and,
- means for counting features of the first clock signal.
A method for time to digital conversion comprising providing first and second digital oscillators having a first state wherein a difference in periods of the first and second signals is TΔ1 and a second state wherein a difference in periods of the first and second signals is TΔ2 where TΔ2<TΔ1;
- with the first and second digital oscillators in the first state, starting the first oscillator upon the occurrence of a first control signal and starting the second oscillator on the occurrence of a second control signal a time Td later;
- when reference points of the first and second signals occur within a predetermined time delay of one another switching the oscillators to the second state;
- counting a number (NC) of edges of the first clock signal which occur while the oscillators are in the first state;
- counting a number (NF) of edges of the first clock signal which occur while the oscillators are in the second state;
- and,
- stopping counting the number (NF) when the reference points have a specified time relationship.
In apparatus for identifying a coincidence between first and second periodic signals, a range extender circuit comprising a first counter connected to count edges of the first signal, a second counter connected to count edges of the second signal, and a comparator connected to compare outputs of the first and second counters.
Dependencies are inferred from the claim text.