Notch filter and apparatus for receiving and transmitting radio-frequency signals which comprises said filter

摘要

The present invention describes a notch filter suitable for attenuating certain frequencies of a radio-frequency signal (TX). The filter comprises an input (A) for receiving the radio-frequency signal and an output (B) for the output of a portion of the radio-frequency signal, first (C1(n1)) and second (C2(n2)) capacitive means, at least one inductor (L) and a negative resistance circuit (5) compensating the resistive losses of said at Least one inductor (L). The inductor and the first and second capacitive means are placed so as to produce a resonator and the filter (1) comprises a control device (4) controlling the negative resistance circuit (5). The input impedance (Zf) of the filter comprises a pole (É p ) and a zero (É z ) and the pole depends on the value of the second capacitive means (C2(n2)) and the zero depends on both the value of the first and second capacitive means; said first and second capacitive means are variable and said control device (4) controls the first and second capacitive means.