Patent ID: 8461821

Claim:
A frequency measuring apparatus comprising: a high-order digit calculation section adapted to obtain a high-order digit value of a frequency value of an input signal; a low-order digit calculation section adapted to obtain a low-order digit value of the frequency value of the input signal; and an adding section adapted to add the high-order digit value and the low-order digit value to output the frequency value of the input signal, wherein the high-order digit calculation section includes: a frequency counter section adapted to measure the frequency of the input signal during a unit time period, and an offset calculation section adapted to remove a count value part corresponding to the low-order digit from a count value of the frequency counter to output the remainder as the high-order digit value, and wherein the low-order digit calculation section includes: a short gate time counter section adapted to count the frequency of the input signal during a time period shorter than the unit time period, a low pass filter section adapted to remove high-a high frequency component from output of the short gate time counter section, and a scaling section adapted to convert an output value of the low pass filter section into a value per the unit time period, and output the value per the unit time period as the low-order digit value.