Filter circuit

A filter circuit comprising:

• an input terminal to which a signal including noise components that are equal to or higher than a cutoff frequency is input;
• an output terminal configured to output an output value in accordance with an input value of the signal;
• a processor;
• one or more memories configured to store an input value and an output value, and instructions to cause the processor to:
• compare an input value and an output value, and
• correct an output value in accordance with an output of comparing,
• wherein
• the instructions further cause the processor to
• compare a current input value with a last-time output value,
• add a first correction value to the current input value and to the last-time output value if a comparison result between the current input value and the last-time output value is greater than a predetermined value, and add a second correction value smaller than the first correction value to the current input value and to the last-time output value if the comparison result is smaller than or equal to the predetermined value, said comparison result being defined as an absolute value of a difference between the current input value and the last-time output value, said second correction value being smaller than the first correction value when a result of subtracting the second correction value to the first correction value is larger than 0,
• calculate a current output value based on the current input value and the last-time output value to each of which the first correction value or the second correction value has been added, and
• output the current output value, thereby removing the noise components,
• wherein
• the one or more memories are further configured to store a last-time input value, and
• the instructions further cause the processor to calculate the current output value based on the current input value and the last-time output value to each of which the first correction value or the second correction value has been added and based on the last-time input value stored in the memory, and
• wherein the instructions further cause the processor to calculate the current output value using a first buffer for storing the input value, a second buffer for storing the last-time output value, and a third buffer for storing the last-time input value, thereby improving a signal attenuation rate in a predetermined frequency range and reducing a computational load without using multi-stage buffers.