Small-Sized Microstrip Lowpass Filter Using Defected Ground Structure

Microstrip lowpass filter plays important role in many RF or microwave applications. They are used to select the microwave signals within assigned spectral limits. In this
project, a conventional stepped-impedance microstrip lowpass filter is designed to have an equal-ripple response with a cutoff frequency of 0.8 GHz. The filter needs to
satisfy more than 20 dB insertion loss at 1.2 GHz with the impedance of 50 Ohm. By using the insertion loss method, filter performance is expected to be improved at the
expense of a higher order filter. Another filter with the defected ground structure (DGS), having the same physical length, is introduced to investigate the performance of the filter.