A compact bandpass filter design using symmetrically triangular open loop resonator

To obtain a good performance of bandpass filter, a more compact microstrip structure is proposed in this paper. Using embedded symmetrically triangular open loops into the resonator, three transmission zeros are found in its' stopband. Therefore, characteristic of sharp rejection is formed, and much smaller size has been obtained for this filter. Compared to the conventional structure using one triangular open loop outside the resonator, the newly designed filter has a size reduction of 46%. To verify this design, a fabricated sample has been tested. Very good results are shown in agreement with simulation.