A Compact Wideband Bandpass Filter Using Transversal Resonator and Asymmetrical Interdigital Coupled

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A UWB FILTER USING MIXED OPEN STUBS TO SUPPRESS
HARMONIC RESPONSE
Adviser Hon Kuan Reporter Wen-Lang Chen
Date 12/01/2008
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OUTLINE

• INTRODUCTION
• FILTER DESIGN
• EXPERIMENTAL RESULTS AND DISCUSSION
• CONCLUSION

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INTRODUCTION
Fig. 1. Schematic diagram of the proposed
ultra-wide-stopband microstrip bandpass filter.
IEEE TRANSACTIONS ON MICROWAVE THEORY AND
TECHNIQUES, VOL. 56, NO. 6, JUNE 2008
Fig. 2. Theoretical responses of the simplified
bandpass filter. (a) Narrowband frequency. (b)
Wideband frequency.
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INTRODUCTION
Fig. 2. Simulated and measured insertion loss of
BSFs. M represents measurements, and S represents
simulation.
Fig. 1. Configurations of BSFs using (a) open
stubs, (b) spurline, and (c) combination of open
stubs and spurline.
IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS,
VOL. 15, NO. 4, APRIL 2005
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FILTER design

• The proposed filter is formed on the RT/Duroid
  5880 with er 2.2 and h 0.508mm.

• Simulation results
• low band 3.3G5.28GHz
• High band 6.37G9.63GHz

spurious response
Figure 1. The simulated frequency resopnse
without bandstop.
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FILTER design
Proposed structure (mixed open stubs)
Method 1
Method 2
(d)
Figure 3. The simulated frequency response by
using different widths of open-stubs.
Figure 2. Configurations of (a) embedded of
open-stub (b) conventional open-stub (c) the
proposed structure (d) Comparison of the
simulated frequency response for the three
structures.
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FILTER design

• With a bandstop filter, the simulated frequency
  response can well suppress spurious response from
  10 to 20 GHz and provide a rejection level 20 dB
  below.

(a)
Figure 4. (a)Layouts of the UWB filter with
bandstop filter. (b) The comparison of the
simulated frequency resopnse with bandstop and
without bandstop.
(b)
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EXPERIMENTAL RESULTS AND DISCUSSION
The UWB filter at lower passband has good
measured results, including a center frequency f0
of 4.35 GHz, low insertion loss of -1.9 0.4 dB,
wide bandwidth of 3.55.2 GHz (FBW 39). The UWB
filter at higher passband also shows good
measured results, including a center frequency f0
of 8.1 GHz, low insertion loss of -2 0.5 dB,
wide bandwidth of 6.59.7 GHz (FBW 40). The
measured upper stopband is significantly widened
up to 20GHz with an attenuation level higher than
23 dB. The measured locations of transmission
zeros appear at 2.6, 5.9 and 12.7 GHz .
Figure 5. (a) Picture, (b) simulated and
measured frequency response of the UWB filter.
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CONCLUSION

• In order to improve the stopband performance, a
  wide bandstop filter using mixed open stubs
  cascaded with UWB bandpass filter for the
  harmonic suppression has been proposed.

• The proposed BSF shows a deeper rejection and
  wider stopband than the conventional open-stub
  BSF without increasing the circuit size.

• By increasing the widths of shunt open stubs,
  the more widen stopband range will be achieved.

• The proposed bandpass filter shows 23 dB
  rejection during the frequency range from 10GHz
  to 20GHz.

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Thanks for your attention!