A NOVEL MICROSTRIP LOWPASS FILTER HAVING TWO TRANSMISSION ZEROS TO GET SHARP ATTENUATION AND WIDE STOPBAND

摘要

This paper proposes a novel microstrip four-pole lowpass filter with compact size and excellent frequency property. Two transmission zeros are introduced in its stopband. The first transmission zero is produced nearby the passband and makes a sharp rate of attenuation. The second transmission zero is introduced to increase significantly the stopband width. The positions of the two transmission zeros can be adjusted easily. Although it has a smaller number of circuit elements and a lower insertion loss, the filter shows a frequency response better than that of a five-pole elliptic function filter: The measured filtering characteristics of the filter agree excellently with the simulated results.