Sulaiman, Ahmad Asari
(2012)
Development Of Microwave Bandpass Filter Using Defected Ground Structure In Comparison With Multilayer And Dielectric Resonator Filters.
PhD thesis, Universiti Sains Malaysia.
Abstract
Bandpass filters perform an important filtering task in a radio transceiver. The
narrow stopbands and low gradient in transition bands of conventional parallel-coupled
or electromagnetic band gap (EBG) are two (2) of the challenges in designing a bandpass
filter. This thesis will introduce three (3) structures of bandpass filter. The first is a new
combination of parallel-coupled and defected ground structure (DGS) that operates at
a center frequency of 7.8 GHz for mobile satellite application. In essence, this
combination structure has resulted to high Q-factor and slow wave which contributes
to a high slope and spurious suppression. Cylindrical dielectric resonators were also
applied to the circuit in order to increase the return loss in the passband or to enhance
the bandwidth of the design. The Zirconate Tin Titanate, ZrSnTiO3 (
r = 37.4, tangent
loss = 0.002) dielectric resonator and RO3003 substrate with dielectric constant and
tangent loss of 3.0 and 0.0013 respectively were applied in this project. The overall
dimension of the circuit was 47.2 mm × 19.16 mm, while the size of the rectangular
DGS was 1 mm × 7.36 mm. The second structure is a combination of end-coupled and
split ring resonators in a multilayer configuration that operate at 3.47 - 3.79 GHz for
Worldwide Interoperability for Microwave Access (WiMAX) application. A
modified split ring was introduced to obtain the additional sub-resonators from the
magnetic coupled between vertical layers in order to increase the coupling effect
from the multilayer structure. The Flame Retardant 4 (FR-4) substrate with dielectric
constant, r of 4.6 was used as a core material.
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