Notch filter and multi-frequency notch filter

A notch filter, comprising at least one notch filtering unit, wherein each of the at least one notch filtering unit comprises an input port, an output port, at least three resonators and at least one inductive element, and the at least three resonators comprise at least two first resonators and at least one second resonator;

• wherein the at least two first resonators are connected in series to each other, the at least two first resonators in series are connected in series between the input port and the output port, a first end of each of the at least one second resonator is connected to a connection point between two adjacent ones of the at least two first resonators, a second end of the each of the at least one second resonator is connected to a fixed potential end, and each of the at least one inductive element is connected in parallel to one of the at least one second resonator.