When will the patent of high-pass filter expire?

The patent of high-pass filter 203 1 expired on May 2002 at 65438+. According to relevant public information, the patent of high-pass filter was applied by Li Xun Electronic Technology (Kunshan) Co., Ltd. on May 2, 20021year, and was authorized on February 4, 20021year. It was invented by Wang with the patent number 10. High-pass filter, also known as low-cut filter and low-resistance filter, allows frequencies above a certain cut-off frequency to pass, but greatly attenuates lower frequencies. Remove unnecessary low-frequency components or low-frequency interference from the signal.