Dual band absorptive band stop filter design

In this thesis, dual band microstrip absorptive band stop filter designs are presented. Investigations of the filter designs proposed within the scope of the thesis have been carried out extensively with simulation studies. First, in the proposed filter circuit design, a crimped open-circuit stub is placed at the symmetry axis of the transmission line connecting the input and output ports. Then, a filter circuit with a third-order double-band band-stop filter response is designed by loading symmetrical open-circuit crimped stubs on the transmission line connected to the input and output ports. Then, by adding resistance to the studs in the filter circuit designed to absorb the bands, absorptive band-stopping filter designs have been introduced. The designed absorptive band stop filters have a low reflection coefficient at the inlet port. A single stop band absorptive (non-reflective) band stop filter can be realized by adding a resistor to one of the studs located symmetrically in the circuit. Depending on the position of the resistor on this stud, only the first and only the second stop band absorptive band stop filter can be designed. By adding a resistor to one of the symmetric stubs and the open-circuit stub located on the symmetry axis, a dual band band-stop filter response is obtained, with both stop bands absorbing. Three filters, in which the bands can be independently absorbed, were fabricated and their experimental studies were carried out. It has been observed that the measurement results are in good agreement with the simulation results.