and quarter-wavelength open-circuited stubs at the feed lines for harmonics suppression. It is fabricated on a
Teflon substrate, which has a relative
dielectric constant of 2.65 and a thickness of 1 mm. The measurements are
carried out on Agilent Vector Network
Analyzer N5230A. The simulated and
measured results are shown together
in Figure 10. The center frequency of
the BPF is 2.44 GHz and its 3 dB bandwidth covers 112 MHz. The filter has a
wide stopband with attenuation of 20
dB up to 10 GHz, using two additional
harmonics suppression resonators. Its
insertion loss is as low as 1.05 dB. It is
obvious that the measured results are
in good agreement with the simulation.
ConClusion
A novel open-loop BPF with a wide
stopband for WLAN is presented in
this article. Its spurious responses are
effectively suppressed by adding two
resonators, which are composed of
asymmetrical spurlines and quarter-
wavelength open-circuited stubs. Em-
ploying the harmonics suppression
resonators, its stopband is controllable
by adjusting the dimension parameters
of two resonators. The BPF has an out
of band attenuation better than 20 dB
from 2.6 to 10 GHz. The measure-
ment results have shown good agree-
ment with the simulated results. It is
believed that this newly proposed BPF
can be used in WLAN systems. n
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