Abstarct: Bandstop filters (BSF) have many applications in telecommunication systems, one of which is the elimination of in-band interferers. This thesis presents a microstrip bandstop filter with the ability to automatically adjust the center frequency and stopband attenuation depending on the RF interferer frequency and power, respectively. The ability of automatic adjustment of the stopband attenuation is obtained by adding a coupler and a power detector at the input of a signal tracking filter and using a feedback circuit which differentially applies the output voltage of detector to the resonators. The proposed filter can be used in situations where the frequency and power of interferer are variable. In order to implement the proposed filter, bridged-T network is used. This network consists of two resonators that has ability of producing of allpass and bandstop responses by adjusting the resonance frequencies of the resonators. Varactor diodes has been used to adjust the resonance frequency of the resonators. The proposed filter has been implemented in the microstrip transmission line using RO4003 substrate and dimensions of 116.37 × 90 mm2 and its simulation has been done in the Momentum of ADS software. According to the simulation results, the filter is capable of tracking interferers with a frequency range of 245 to 295 MHz. Also, by changing the interference power from -10 dBm to 5 dBm, the attenuation of the stopband can be increased from 5 dB to about 20 dB. Broadband simulation of the proposed filter shows that the filter has a acceptable bandstop response in the frequency range of 100 MHz to 450 MHz and it’s passband return loss is less than -12 dB. Two-tone test simulation shows that the IM3 level of proposed filter is less than -55 dBm.