To improve the transmission rate and quality of the communication system

a coplanar waveguide(CPW)broadband filter with high selectivity is designed.The filter consists of a double helix defected ground structure(DGS)

U-shaped DGS

and a stepped CPW transmission line slot coupling structure.Using stepped CPW transmission lines can improve matching performance.The source and load coupling structure introduce low-frequency transmission zero points

and etching U-shaped DGS can expand bandwidth and introduce high-frequency transmission zero points.The experimental results show that the operates within a bandwith filter of 2.05~2.94GHz

with insertion loss prior to 0.85dB and return loss prior to 20dB.In addition

there are transmission zero points on both sides of the passband edge

which improves the selectivity and out of band suppression performance of the filter.The filter is physically processed and tested

and the measured and simulated results show a high coincidence

verifying the effectiveness of the design.The effective size of the filter is small

only 18.2mm×16.6mm

suitable for communication systems operating in the WLAN frequency band.