Compact dual-band filter design using crossly coupled λ/4 SIRs embedded with spur-line for WLAN applications

This article presents a compact dual-band bandpass filter (BPF) design using λ/4 stepped impedance resonators (SIRs) embedded with spur-line for the WLAN applications. The filter covers both the operating frequencies of 2.45 GHz and 5.2-5.8 GHz. The crossly coupled mechanism is used in the filter design to provide attenuation poles by the passband edges for enhancing the signal selectivity and increasing stopband rejection levels. The tapped-line is incorporated in feed structure to save the circuit space. The spur-line is embedded in each I/O SIRs to push the upper stopband limit to a higher frequency. Experiments are conducted to verify the circuit performance. A good agreement is observed between the simulation and the measurement.