Design of wideband microwave bandpass filter with notch characteristic using defected structure

• Main Author: Mutalib, Mohamad Ariffin
• Format: Thesis
• Language: English; English
• Published: 2015
• Subjects: T Technology (General); TK Electrical engineering. Electronics Nuclear engineering
• Online Access: http://eprints.utem.edu.my/id/eprint/16840/1/Design%20Of%20Wideband%20Microwave%20Bandpass%20Filter%20With%20Notch%20Characteristic%20Using%20Defected%20Structure.pdf; http://eprints.utem.edu.my/id/eprint/16840/2/Design%20of%20wideband%20microwave%20bandpass%20filter%20with%20notch%20characteristic%20using%20defected%20structure.pdf; http://eprints.utem.edu.my/id/eprint/16840/; http://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=96176

Bandpass filter is an essential component, in microwave wireless communication systems, which is typically used in both receivers and transmitters. Bandpass filter with wideband passband has been attracting a lot of interests of researcher to employing different methods and techniques. However, some existing radio systems that use narrow band signals, such as IEEE 802.11a WLAN in the band 5.2 GHz, can cause an interference with the wideband systems (3-6 GHz). Therefore, this thesis presents new techniques for the design of microwave bandpass filter at 3-6 GHz which cover wideband with fractional bandwidth of about 66.67%. The return loss is better than 16 dB and insertion loss is less than 0.9 dB. This filter was constructed by using short circuit stubs bandpass filter for microstrip structure and generalized Chebyshev bandpass filter for suspended stripline structure. The suspended stripline structure bandpass filter used the method of cascading generalized Chebyshev low-pass and high-pass filters. This technique provides various advantages such as reducing the number of elements and transmission zeros can be placed in arbitrary frequency response. In order to avoid the interference from existing system that operates in the frequency band, a defected structure was introduced to generate a narrow notch band. Then the defected structure with inverse T-shape will be integrated with the band-pass filter in order to provide high attenuation is 21 dB with narrow bandwidth of 5.83% and Q factor of about 34.33. The second design is defected stripline structure with J-shape that integrated with a generalized Chebyshev bandpass filter. The notch response of measured value is 5.2 GHz at 25 dB resonant frequencies with fractional bandwidth of 6.79% and Q factor is about 34.78. By integrating this defected structure, the overall size can be reduced about 15% and it provides easy technique to produce band reject response. This structure is very useful for wireless systems as it can be easily integrated with other planar devices. Advanced Design System (ADS) software was used to simulate the design from circuit element to physical momentum realization. The experimental results showed good agreement with the simulated results. The benefits of the integrated band-pass filter and defected structure are the reduction of the overall size, easier to fabricate and high Q-factor. This new design of microwave filter is considered suitable and an alternative solution for wireless and radar application without any addition of external components in the cascaded structure.