A time-to-digital converter obtains a Start signal to indicate the start of an event, and a Stop signal whose assertion indicates the stop of the event. The Stop signal can be asserted multiple times due to false indications of the event stop. The TDC continuously monitors the Stop signal to generate a separate digital value for the duration from the event's starting time to each assertion of the Stop signal. The digital values can be analyzed to select the true duration of the event. Other features and embodiments are also provided.

A time-to-digital converter obtains a Start signal to indicate the start of an event, and a Stop signal whose assertion indicates the stop of the event. The Stop signal can be asserted multiple times due to false indications of the event stop. The TDC continuously monitors the Stop signal to generate a separate digital value for the duration from the event's starting time to each assertion of the Stop signal. The digital values can be analyzed to select the true duration of the event. Other features and embodiments are also provided.

This invention relates to apparatus and methods for measuring the time-of-flight of a signal. The signal may be acoustic energy or electromagnetic energy such as x-ray, radio frequency, microwave, millimeter-wave, radar, and laser. Unlike unambiguous ranging devices that measures the phases of two or more signals to determine the time-of-flight and requires long averaging to achieve some degree of accuracy, this invention phase lock one or more transmitter signals to the corresponding received signals in predetermined phase relationships and measures the frequencies of one or more variable frequency oscillators having frequencies several times higher than the frequency of the transmitter signal to determined the time-of-flight with much higher accuracy.

This invention relates to apparatus and methods for measuring the time-of-flight of a signal. The signal may be acoustic energy or electromagnetic energy such as x-ray, radio frequency, microwave, millimeter-wave, radar, and laser. Unlike unambiguous ranging devices that measures the phases of two or more signals to determine the time-of-flight and requires long averaging to achieve some degree of accuracy, this invention phase lock one or more transmitter signals to the corresponding received signals in predetermined phase relationships and measures the frequencies of one or more variable frequency oscillators having frequencies several times higher than the frequency of the transmitter signal to determined the time-of-flight with much higher accuracy.

A time-to-digital converter (TDC, 110) obtains a Start signal to indicate the start of an event, and a Stop signal whose assertion indicates the stop of the event. The Stop signal can be asserted multiple times due to false indications of the event stop. The TDC continuously monitors the Stop signal to generate a separate digital value (T.j_i) for the duration from the event's starting time to each assertion of the Stop signal. The digital values can be analyzed to select the true duration of the event. Other features and embodiments are also provided.

A time-to-digital converter (TDC, 110) obtains a Start signal to indicate the start of an event, and a Stop signal whose assertion indicates the stop of the event. The Stop signal can be asserted multiple times due to false indications of the event stop. The TDC continuously monitors the Stop signal to generate a separate digital value (T.j_i) for the duration from the event's starting time to each assertion of the Stop signal. The digital values can be analyzed to select the true duration of the event. Other features and embodiments are also provided.

This invention relates to apparatus and methods for measuring the time-of-flight of a signal. The signal may be acoustic energy or electromagnetic energy such as x-ray, radio frequency, microwave, millimeter-wave, radar, and laser. Unlike unambiguous ranging devices that measures the phases of two or more signals to determine the time-of-flight and requires long averaging to achieve some degree of accuracy, this invention phase lock one or more transmitter signals to the corresponding received signals in predetermined phase relationships and measures the frequencies of one or more variable frequency oscillators having frequencies several times higher than the frequency of the transmitter signal to determined the time-of-flight with much higher accuracy. An example of an embodiment of this invention is an apparatus that transmits a signal to a receiver and phase lock the transmitted signal to the received signal in a first selected phase relationship. A first frequency of the phase locked signal is determined and a second phase relationship that differs from the first phase relationship by a predetermined fraction of a cycle is selected. The transmitter signal relocks to the receiver signal in the second phase relationship and a second frequency of the relocked signal is determined. The time-of-flight is measured using the first and second frequencies and the predetermined fraction of a cycle difference in phase relationships.

This invention relates to apparatus and methods for measuring the time-of-flight of a signal. The signal may be acoustic energy or electromagnetic energy such as x-ray, radio frequency, microwave, millimeter-wave, radar, and laser. Unlike unambiguous ranging devices that measures the phases of two or more signals to determine the time-of-flight and requires long averaging to achieve some degree of accuracy, this invention phase lock one or more transmitter signals to the corresponding received signals in predetermined phase relationships and measures the frequencies of one or more variable frequency oscillators having frequencies several times higher than the frequency of the transmitter signal to determined the time-of-flight with much higher accuracy. An example of an embodiment of this invention is an apparatus that transmits a signal to a receiver and phase lock the transmitted signal to the received signal in a first selected phase relationship. A first frequency of the phase locked signal is determined and a second phase relationship that differs from the first phase relationship by a predetermined fraction of a cycle is selected. The transmitter signal relocks to the receiver signal in the second phase relationship and a second frequency of the relocked signal is determined. The time-of-flight is measured using the first and second frequencies and the predetermined fraction of a cycle difference in phase relationships.

A circuit for a divider or counter may include a frequency divider having multiple rings for dividing an input frequency to obtain an output frequency. The first and second rings may include an odd-numbered plurality of elements, such as inverters, wherein each inverter of a ring is coupled to another inverter of the ring in a circular chain. An input frequency may be input to a power supply input of inverters of the first ring. The second ring inverters may be coupled at a power supply input to output nodes of the first ring inverters, which results in the second ring operating at a divisional rate of the first frequency given by (N1), where N is the number of inverters in the ring. The circuits may be used in frequency dividers and counters, such as in phase-locked loops (PLLs) and analog-to-digital converters (ADCs).

A circuit for a divider or counter may include a frequency divider having multiple rings for dividing an input frequency to obtain an output frequency. The first and second rings may include an odd-numbered plurality of elements, such as inverters, wherein each inverter of a ring is coupled to another inverter of the ring in a circular chain. An input frequency may be input to a power supply input of inverters of the first ring. The second ring inverters may be coupled at a power supply input to output nodes of the first ring inverters, which results in the second ring operating at a divisional rate of the first frequency given by (N1), where N is the number of inverters in the ring. The circuits may be used in frequency dividers and counters, such as in phase-locked loops (PLLs) and analog-to-digital converters (ADCs).