Design of switchable mathed bandstop filter

Zahari, Mohd Khairy (2013) Design of switchable mathed bandstop filter. Masters thesis, Universiti Teknikal Malaysia Melaka.

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New developments in the design of band reject filters are essential to meet the ever increasing demands on suppression of unwanted signals and miniaturization of microwave communications systems. A compact design can be achieved through the implementation of planar microstrip technology. Conventional electronically tunable bandstop filters suffer performance degradation due to the finite unloaded Q of the resonators and also the loss associated with the switching elements. Recently a new filter topology using lossy resonators has been introduced where the topology can be used to partially compensate for the loss. A frequency agile bandstop filter based on this topology has been developed, but such filters as well as conventional switchable bandstop filters encounter performance degradation in terms of tuning bandwidth and stopband bandwidth due to the frequency dependant losses and couplings. Through this thesis the filter is designed and developed an L-shape matched bandstop filter and dual mode ring resonator which can be switchable based on a lossy allpass network. The filters are integrated with switching elements that suitable for the perfectly matched bandstop concept. The lossy allpass network demonstrates the concept and design of perfectly matched bandstop response with a perfectly matched at all frequencies. The filter is based on the half-wavelength λ/2 resonator with gap coupling, parallel with an allpass nominally-90°-phase-shift element, which can be optimized to achieve high Q-factor. The switchable L-shape matched bandstop filter and switchable dual mode ring resonator can be realized by using PIN diodes as a switching elements. The dual-mode ring resonator structure is composed by two degenerate modes or splitting resonant frequencies. Two degenerate modes can be excited by perturbing stubs, notches or symmetrical feed lines. The dual-mode ring resonator stub’s is located at 135°. Both filters provide two state of operation under two conditions. The first condition is that the filter will produce allpass response when the PIN diodes are turned ‘ON’. The second condition is that the filter will produce perfectly matched bandstop response when the PIN diodes are turned ‘OFF’. The perfectly matched bandstop filter operates 1 GHz where S11 and S21 having the same attenuation at 1 GHz. For S11 must be less than 15 dB and S21 the attenuation level less than 15 dB. The allpass response having S21 ≈0.2 dB.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Microwave filters, Microwave transmission lines
Subjects: T Technology > T Technology (General)
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Library > Tesis > FKEKK
Depositing User: Norziyana Hanipah
Date Deposited: 04 Sep 2015 07:42
Last Modified: 20 Sep 2022 12:11
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