| 摘要 |
An active filter adapted to filter a line containing an electrical waveform, comprising: an amplifier (5), a control system (4), a waveform measuring device (CT) and a coupling circuit (6); the waveform measuring device (CT), in use, providing an input signal to the control system (4), the control system controlling the amplifier (5) in response to the input signal and the coupling circuit (6) connecting the amplifier to the system to be filtered; wherein the coupling circuit (6) comprises a passive circuit arranged in a four terminal network of restricted form having no poles in its frequency response within its useful bandwidth. Generally, the four terminal network (6) is provided as a ladder circuit, and a primary use of the filter is to filter ac or dc supplies in electrical power systems. |
