Phase Velocity Compensation in Compact Coupled-Line Bandpass Filter with Square Corrugations
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Present paper highlights the design of a compact coupled-line bandpass filter with extended stopband and improved second harmonic suppression. The proposed filter is designed at a center frequency of 2.5 GHz with 20% fractional bandwidth applicable in WLAN. The size of the ladder-type parallel-coupled line bandpass filter has been reduced to 44% and 62% by modifying it to folded and in-line structure. Accordingly, periodic square shaped corrugations are inserted to the coupled edges of the parallel lines. The second harmonic suppression of 60 dB with stopband rejection level of 62 dB and a size reduction of 52% have been achieved for folded filter with 6 periodic square corrugations. The in-line filter with four square corrugations gives the second harmonic suppression of 55 dB with a stopband rejection level of 58 dB and a size reduction of 70%.
KeywordsBandpass filter Coupled-line Folded filter Harmonic suppression In-line filter Square corrugations
Authors are grateful to Mr. Arijit Majumder and Mrs. Souma Chatterjee for giving permission to use the facility of SAMEER Kolkata, India. One of the author Dr. Sayan Chatterjee is thankful to AICTE for the carrier award vide file no: 11-35/RIFD/CAYT/POL-1/2014-15.
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