Design of a Microstrip Ultrawide Band Bandpass Filter using Short Stub Loaded

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 10 | Oct -2017 www.irjet.net p-ISSN: 2395-0072
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Design of a Microstrip Ultrawide band Bandpass Filter Using Short Stub
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1Sandeep kumar tripathi, 2Anil Kumar chaudhary
1,2 Dept. of Electronics and Communication engineering, Buddha institute of Technology, Gida
Gorakhpur, India
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Abstract— we are proposing a compact micro-stripultra
wideband (3.1 -10.8 GHz) filter in this paper. Here center
frequency is resonated by coupled line section and
transmission zero is created by short stub of quarter wave
length loaded at loading point. It is compact in size andhas
very sharp selectivity at the corner frequencies. The
location of Transmission zero can belocatedatanydesired
frequency by varying the length of additional short stub.
The insertion loss of the proposed filter is lower than
approx .2dB and return loss is smaller than 20dB. We
simulate the proposed filter by using the tool ADS and all
the results were attached and compared and contrasted
with available reported results.
Keywords—UltrawideBand filters; Microstrip,short
stub;
1.Introduction
As we know Ultra wide band including C-band is widely
used in radar communication as well as in military
operation . There are so many other devices whicharealso
used in Ultra wide band application such as cordless and
Wi-Fi, some weather scanning radar equipments. A no. of
band pass filter has been released since last few years.The
frequency bandwidth has assigned for Ultra wide band
application is from 3.1 to 10.6 GHz [1]. So many different
methods and structures are being either used or proposed
to confine the allotted frequency range (3.1 to 10.6 GHz)
for Ultra wide-band application. A lot of new structures
and designs have been used recently for the development
of new Ultra wide-band Band pass filter [1].
Fig.1. Schematic of the compact micro strip-line UWB
band pass filter.
Substrate: " = 10.8; thickness = 1.27 mm.
In the reference paper [1], a MMR is used to create 3
resonant frequencies to form an ultra wide-band.
Structure’s dimensions are given in the above figure and
simulated results of the above structure are shown in the
figure bellow.The problem what we found while creating
ultra wide band with the help of MMR isthatthebulkystub
sizes of the MMR creating problem to make compact size
filter. Coupling length Lc can be vary to adjust the
transmission zeros and create better selectivity of the
band. In this case, the first- and third-order resonant
frequencies basically determinetheloweranduppercutoff
frequencies of a wide pass band.By introducing the two
additional transmission poles in the parallel-coupled lines
as shown in the above figure, an Ultra wide-band can be
made up with good insertion loss and good return loss
.
Sheng Sun et al. has proposed in his paper [5],
improvement in the above micostrip UWB filter can be
done by the coupled line feed with the MMR structure to
provide additional transmission zeros.
Hussein Shaman et al. has suggested that coupled line
asymmetric open stub is added to provide notch on the
pass band to create notch in the UWB filter band.
By varying the length of the uncoupled open stub, place of
the notch can be adjusted and bandwidth of that notch
frequency can also be adjusted Proposed ultra wide band
filter
In Fig 1, the configuration of proposed filter is given which
was showing in the tool ADS. Fig.2 shows the proposed
UWB filter with the dimension .Because of simple and two
via (ground) in the proposed structure, it is slightly

difficult to fabricate but because of that via selectivity of
the band is very sharp. Filter consists of coupled line
sections with coupling length of quarter wavelength of
lower frequency. Higher resonatingfrequencyisgenerated
due to the image of fundamental
Frequency. This frequencymaybetakenasreplica oflower
frequency. Due to via used in the structure there are three
different bands are created and selectivity of these bands
are very high. Selectivity near the cutoff frequencies are
very sharp which make the proposed filter very good for
the created UWB .
Fig 1. Schematic of the ultra wide band based filter.
Substrate: Er=10.6, thickness=1.0 mm.
As shown in the figure there are 2 coupled lines of quarter
wavelength to create two resonating frequencies. Using a
commercially available tool [2], Fig 2. (a) is analyzed for
resonating structure. Here, center part is the resonating
structure for UWB- filter. Center frequency of the band is
6.85 GHz. Two stubs of quarterwavelengtharegroundedto
create better selectivity of the created UWB.
S we know half wave length structure is resonating at its
fundamental frequency .additional transmission zeros
can be obtained by shorting the quarter wavelength.
As shown in the figure3: there are three bands are created
by shorting the quarter wavelength to create two
transmission zeros .
Two stubs of quarter wavelength are coupled tocreatetwo
resonating frequencies in each band.
Two resonating frequencies are available in each band for
two mode operation.
Stubs are grounded to create better selectivity of the
created UWB. by creatingvia,sharpnessofthecreatedUWB
are very good.
(a)
Fig 2. Proposed resonating structures with couple
sections (a) Design of UWB filter
Figure 2 shows the dimensions of the proposed filter as
mentioned bellow.
Table.1
S.N.
Dimentions of filter
Symbol Length Unit
1. L1 5 mm
2. L2 0.9 mm
3. L3 0.2 mm
4. L4 0.8 mm
5. L5 0.8 mm
6. L6 2.7 mm
7. L7 0.5 mm
8. L8 0.1 mm
9. L9 4.6 mm
All dimensions are in mm, and the center frequency is
considered to be 6.85 GHz. Width of the all strip is
0.2mm.Impedance of the strip line is taken 125 Ohm. Input
and output feeding width is set to 50 ohm and the length to
non-resonatinglengthso that its ownresonatingfrequency
does not disturb other required resonating frequencies.
Filter is realized on a low cast roger TMM substrate with a
relative dielectric constant of 10.8 and thickness 1.0mm.
Commercially available full wave simulator tool [6] ADS is
used for verification of all parameter.

Fig 3. S21 and S11 Parameter of proposed UWB-band
filter.
In proposed UWB- filter, Insertion loss is below to -20dB
and return loss is about -2.0 dB.
IV. Performances
Proposed filter is design for UWB- frequency range. Filter
consist of two sections of quarter wavelength to create
bands for their respected frequencies two stubs at the
both side upper and lower end are grounded to to create
two transmission zeros and the selectivity of the filter will
enhance because of thisgroundingstubsfundamental used
in the proposed filter..
Proposed filter Size is Smaller than most of the UWB filter
and selectivity of the UWB filter is very sharp near the cut
off frequencies of all the created bands,alsothereturnloss
is good from most of UWB filterperformance.Presentfilter
is compact in size, having insertion loss less than 2.0 dB
and return loss below 20dB (approx.).
V. conclusion
An UWB filter with three bands are created and two
resonating frequencies are available in each band .two
notches are created by grounding the two quarter
wavelength stubs .the benefits of two notches can be
understand by this example that if in the ultra-wide band
range (3.1 to 10.6 GHz) if certain frequencies are used for
some other application then that frequencies can be
eliminated with the help ofthesecreatednotches.thereare
four quarter wave stubs in symmetrical position are used
to realize the proposed filter and couplinglengthshouldbe
enough to create sufficient wide band .stubs can be
[1] L. Zhu, S. Sun, and W. Menzel, “Ultra-wideband (UWB)
bandpass filters using multiple-mode resonator,”IEEE
Microw. Wireless Compon. Lett., vol. 15, no. 11, pp.
796–798, Nov. 2005
[2] ADS tutorial.
[3] S. Sun and L. Zhu, “Capacitive-ended interdigital
coupled lines for UWBbandpass filters with improved
out-of-band performances,” IEEE Microw. Wireless
Compon. Lett., vol. 16, no. 8, pp. 440–442, Aug. 2006.
R. Li and L. Zhu, “Compact UWB bandpass filter using
stub-loaded multiple-mode resonator,” IEEE Microw.
Wireless Compon. Lett., vol.17, no. 1, pp. 40–42, Jan.
2007.
[4] Hussein Nasser Shaman,“ Design of A CompactC-band
Microstrip Bandpass Filter for Satellite
Communications Applications,” IEEE Trans,Wireless
and Optical Communication Network, 978-1-4673-
1989-8/12, Sep2012.
[5] D. Kornack and P. Rakic, “Cell Proliferation without
Neurogenesis in Adult Primate Neocortex,” Science,
vol. 294, Dec. 2001, pp. 2127-2130,
doi:10.1126/science.1065467.
[6] M. Young, The Technical Writer’s Handbook. Mill
Valley, CA: University Science, 1989.
[7] R. Nicole, “Title of paper with only first word
capitalized,” J. Name Stand. Abbrev., in press.
[8] K. Elissa, “Title of paper if known,” unpublished.
adjusted to change the position of the resonating
frequencies .Additional stub is adjusted to locate
transmission zero at desired frequency. The bandwidth is
controlled by adjusting the couple line with feed section.
Filter is designed and analyzed to demonstrate the UWB
filter and proposed structure. Filter is compact in size, low
insertion loss and low return loss.
VI. References

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