Design of a Microstrip Dual-Band Bandpass Filter Using Novel Loaded Asymmetric Two Coupled Lines for WLAN Applications

Background and Objectives: Due to the rapid development in wireless communications, bandpass filters have become key components in modern communication systems. Among the microwave filter technologies, planar structures of microstrip line are chosen, due to low profile, weight, ease of fabrication, and manufacturing cost. Methods: This paper designs and simulates a new microstrip dual-band bandpass filter. In the proposed structure, three coupled lines and a loaded asymmetric two coupled line are used. The design method is based on introducing and generating the transmission zeros in the frequency response of a wideband single-band filter. A wideband frequency response is obtained using the three coupled lines, and the transmission zeros are achieved using the novel loaded asymmetric two coupled lines. Results: The proposed dual-band filter is designed and simulated on a Rogers RO3210 substrate for WLAN applications. Dimension of the proposed filter is 11.22 mm × 13.04 mm. The electromagnetic (EM) simulation is carried out by Momentum EM (ADS) software. Simulation results show that the proposed dual-band bandpass filter has two pass-bands at 2.4 GHz and 5.15 GHz with a loss of less than 1 dB for two pass-bands. Conclusion: Among the advantages of this filter, low loss, small size, and high attenuation between the two pass-bands can be mentioned.