Improving Frequency Response of Microstrip Filters Using Defected Ground and Defected Microstrip Structures

In this work, the introduction of Defected Microstrip Structures and Defected Ground Structures is presented to improve the performance of a traditional stepped-impedance microstrip lowpass filter. The attenuation in the stop-band is enhanced by more than 15 dB and selectivity is increased, without modifying the insertion loss in the pass band. A comparison of characteristics in filters is made when the combination of Defected Ground and Defected Microstrip Structures, as well as when only the first one are used. A model of the Defected Microstrip Structure and the corresponding equations to obtain the equivalent lumped and distributed element values are also given.