Aspects are directed to systems and methods of determining a value of a characteristic related to timing between sequential events of an input electronic signal using an input capture counter having a maximum counting value, the input electronic signal having an expected variable period between events whose value is between a maximum period value and a minimum period value with a delta period value equal to a difference between the maximum period value and the minimum period value.

A sensor module includes: a count unit configured to generate first to n-th count values of a time event of one of a measurement target signal output from a physical quantity sensor and a reference periodic signal output from a reference periodic signal generation unit in synchronization with the other; a time digital value generation unit configured to generate first to n-th time digital values based on a phase difference between the measurement target signal and the reference periodic signal; and a combined output value generation unit configured to generate an i-th combined output value based on the i-th time digital value and the i-th count value. A quantization error of the j-th combined output value is fed back to generation of the (j+1)-th combined output value, and a period of a change in the physical quantity when a frequency, at which the physical quantity changes, is a maximum frequency is longer than eight times an average period in which first to n-th combined output values are generated.

A sensor module includes: a count unit configured to generate first to n-th count values of a time event of one of a measurement target signal output from a physical quantity sensor and a reference periodic signal output from a reference periodic signal generation unit in synchronization with the other; a time digital value generation unit configured to generate first to n-th time digital values based on a phase difference between the measurement target signal and the reference periodic signal; and a combined output value generation unit configured to generate an i-th combined output value based on the i-th time digital value and the i-th count value. A quantization error of the j-th combined output value is fed back to generation of the (j+1)-th combined output value, and a period of a change in the physical quantity when a frequency, at which the physical quantity changes, is a maximum frequency is longer than eight times an average period in which first to n-th combined output values are generated.

A method of frequency estimation. A clock output from a frequency synthesizer is received at an input of a ring encoder. The ring encoder generates outputs including a ring encoder output clock and an encoded output which represents LSBs of a clock cycle count of the clock output. A binary counter is run using the ring encoder output clock which provides an output count which represents MSBs of the clock cycle count. Using a reference clock, the encoded output is sampled to provide a sampled encoded output and the output count is sampled to provide a sampled output count. Error correcting is applied to the sampled encoded output to provide a corrected sampled encoded output. The corrected sampled encoded output and sampled output count are combined to provide a combined output which is used for estimating an instantaneous or average frequency of the clock output.

A method of frequency estimation. A clock output from a frequency synthesizer is received at an input of a ring encoder. The ring encoder generates outputs including a ring encoder output clock and an encoded output which represents LSBs of a clock cycle count of the clock output. A binary counter is run using the ring encoder output clock which provides an output count which represents MSBs of the clock cycle count. Using a reference clock, the encoded output is sampled to provide a sampled encoded output and the output count is sampled to provide a sampled output count. Error correcting is applied to the sampled encoded output to provide a corrected sampled encoded output. The corrected sampled encoded output and sampled output count are combined to provide a combined output which is used for estimating an instantaneous or average frequency of the clock output.

A phase frequency detector-based high-precision feedback frequency measurement apparatus and method: a Field Programmable Gate Array (FGPA) roughly measures a frequency fx of a measured time-frequency pulse by an equal-precision frequency measurement method; a Direct Digital Synthesizer (DDS) automatically synthesizes a frequency fx according to the fx roughly measured by the FPGA; the fx and the fx are sent to a phase frequency detector for performing phase frequency detection and then sent to the FPGA after passing through a charge pump, a low-pass filter circuit, and an (Analogue-to-Digital) A/D converter; the FPGA processes a frequency difference obtained by the phase frequency detector and then transmits the processed frequency difference to the DDS to form a negative feedback frequency measurement system so that the DDS continuously adjusts the fx according to a frequency difference measurement result until the output of the DDS is stable. Therefore, precise measurement of the time-frequency pulse to be measured is realized.

A phase frequency detector-based high-precision feedback frequency measurement apparatus and method: a Field Programmable Gate Array (FGPA) roughly measures a frequency fx of a measured time-frequency pulse by an equal-precision frequency measurement method; a Direct Digital Synthesizer (DDS) automatically synthesizes a frequency fx according to the fx roughly measured by the FPGA; the fx and the fx are sent to a phase frequency detector for performing phase frequency detection and then sent to the FPGA after passing through a charge pump, a low-pass filter circuit, and an (Analogue-to-Digital) A/D converter; the FPGA processes a frequency difference obtained by the phase frequency detector and then transmits the processed frequency difference to the DDS to form a negative feedback frequency measurement system so that the DDS continuously adjusts the fx according to a frequency difference measurement result until the output of the DDS is stable. Therefore, precise measurement of the time-frequency pulse to be measured is realized.

A digital frequency measuring apparatus includes a frequency divider dividing an input frequency signal and providing a divided frequency signal; a period counter counting clock cycles in a period of the divided frequency signal using a clock signal and providing a period count value for each period; and a digital filter amplifying the period count value using an accumulated gain, converting an amplified period count value into a frequency, and providing a first digital output value. The digital filter determines the accumulated gain using a predetermined stage number and a predetermined decimator factor.

A digital frequency measuring apparatus includes a frequency divider dividing an input frequency signal and providing a divided frequency signal; a period counter counting clock cycles in a period of the divided frequency signal using a clock signal and providing a period count value for each period; and a digital filter amplifying the period count value using an accumulated gain, converting an amplified period count value into a frequency, and providing a first digital output value. The digital filter determines the accumulated gain using a predetermined stage number and a predetermined decimator factor.

A method includes a) counting whole periods of a signal during a first period of a reference signal, b) repeating step a) for each period of the reference signal until a first duration is equal to a first quantity of periods of the reference signal, and c) determining a first average of the whole periods. The method also includes repeating at least one of steps a) to c) and at each repetition shifting a start of the counting of step a) by at least one period of the reference signal, and in steps b) and c) accounting for whole periods of the signal already counted during the at least one preceding group of steps a) and b). The method includes determining a second average of the first averages, and determining the frequency of the signal from the second average and the frequency of the reference signal.