Design of Narrowband Band Pass Filter using Open

Design of Narrowband Band Pass Filter using Open
Indian Journal of Science and Technology, Vol 9(47), DOI: 10.17485/ijst/2016/v9i47/102197, December 2016
ISSN (Print) : 0974-6846
ISSN (Online) : 0974-5645
Design of Narrowband Band Pass Filter using
Open-loop Square Resonators with
Loading Element
A. Venkata Varunbabu Mannam1 and B. Yedukondala Rao Veeranki2*
National Instruments, Bannerghatta Road, Bangalore - 560029, Karnataka, India; mannamvarun@gmail.com
2
Manipal Institute of Technology, Manipal – 576104, Karnataka, India; ykraoveeranki@gmail.com
1
Abstract
Objectives: In this paper we propose to design a compact, sharp-rejection narrowband BandPass Filter (BPF).
Methods/Statistical Analysis: The behavior of the microstrip open-loop resonator is observed using full-wave
electromagnetic simulations. By adding a loading element at the center of the open loop square resonator we are achieving
two operating modes (even and odd modes) exist within a single resonator. Variation of parameters of the loading element
leads to asymmetric frequency response used for filter design. The simulated results met all the design specifications
of the given band pass filter. Findings: In the dual-mode open loop resonator the even and odd modes (currents are
mutually exclusive in nature) do not couple each other and leads to a rejection point in the frequency, which is associated
with the even mode. Multiple sections of resonator give the sharp rejection (high dynamic range) after the passband.
Application/Improvements: The proposed band pass filter can be widely used in communication system and space
technology, especially mobile and satellite communication due to its better performance and compactness.
Keywords: BandPass Filter, Dual-mode Resonator, Electromagnetic Coupling, Micro Strip Antennas, Strip Lines
1. Introduction
The electronic components with compact in size draws
a lot of attention in the past few decades due to the very
fast development of the mobile industry. Traditional
high performance filters (like waveguide and dielectric
resonator filters) are generally too heavy and bulky for
applications like mounting on towers in base stations1
.
Similar behavior is observed in satellite applications
where payload costs are increased a lot, and filters with
better performance are typically required. Recently, the
captured global market of mobile devices is pushing
the needs beyond its limits. In recent portable products
there is a limited use for bulk components with great
performance. This is mainly due to the fact that majority
of communication systems designed to wok below 6 GHz
frequency band.
At lower frequencies the resonators used are Bulkwave resonators, SAW (surface acoustic wave) filters and
helical resonators. All these are used when small in size
* Author for correspondence
and low insertion loss are strongly demanded. Among
the entire filter technologies microstrip remains popular
because it is easy to integrate in the system, occupies small
volume as well as its fabrication processes. Moreover,
electronically tunable and reconfigurable filters, like the
notch filters designed in ultra-wideband applications,
uses surface mount varactors that are compatible with
microstrip implementations2.The popular disadvantage of
microstrip resonators is the low quality factors (Q-factor).
However, for applications that need negligible insertion
loss (like front ends of satellite receivers), or very narrow
relative bandwidths, microstrip resonators provides great
amount of quality factor1.
By the way, the compactness in the microstrip
component design leads to reduce the size of the required
cooling system in the applications leads to over-all
transceivers that are smaller than traditional transceivers,
which usesdielectric resonator filters or waveguides1,3.
The more information about band pass filter is referred
from the references4–8.
Design of Narrowband Band Pass Filter using Open-loop Square Resonators with Loading Element
2. Proposed Design
The microstrip open loop resonator is animportant key
structure for bandpass filter applications due to its crosscoupling nature, smallin size, of approximately by , and
versatility9–12. The general structures of the square open
loop resonators are shown in Figure 1.
w
a
The innovation of the wrapping arms (in a folded
manner) square open loop resonator of Figure 1can be
used as miniaturized hairpin resonators 13. In the case of
the wrapping arms resonator the size is further reduced
more than what we thought due to the interesting
phenomena of coupling between the arms upto 45%13.
The wrapping arms structure can be designed with lower
characteristic impedance in order to design the model
with compact size14. The resonator shown in Figure 2
works in a different way; it has two independent operating
modes, and the electro-magnetic coupling between them
can be modified by the parameters of the loading element.
This new design of the resonator providing compact size
model with reduction of 50%. The method we proposed
in this research is the square open loop resonator with a
loading element at the center of the resonator as shown
in Figure 1.
a
(a)
g
1
w
W
2
a
d
a
(b)
w
Figure 2. Dual mode open-loop square resonator.
a
a
(c)
Figure 1. Square Open Loop Resonator (SOLR) and some
miniaturization techniques. (a) Conventional SOLR (b)
Folded arms SOLR (c) Dual mode SOLR.
2
Vol 9 (47) | December 2016 | www.indjst.org
Each single-mode resonator is equal to an LC coupled
circuit, which produces a pole (transmission zero) at
the resonance frequency. But in order to design a filter
with sharp rejection number of single-mode resonators
are to be connected in cascade structures and this leads
to increase in size of the filter. Each Dual-mode open
loop resonator (proposed design) is a doubly tuned LC
resonant circuit. The number of resonators required for
a given degree of filter is reduces by half because of the
dual-mode behavior. The proposed design has the same
size as single mode resonator with the help of loading
element leads to compact in size. A loading element with
a variable parameter ‘W’ is placedat the center of the
resonator.
Indian Journal of Science and Technology
A. Venkata Varunbabu Mannam and B. Yedukondala Rao Veeranki
Change of width of loading element 'W' leads to mode
splitting. Two modes exist odd mode and even mode.
The fixed frequency component of the band-pass filter by
adjusting of width of loading element is called odd-mode.
The variable frequency component by varying of width of
loading element is called even-mode.
Here the effect of the loading element is shown in
Figure 2 with different ’W’ values on the microstrip
open-loop square resonator on TMM10 substrate having
dielectric constant (
of 10.8 with substrate height of
1.27mm.
Odd mode exhibits the same characteristics that
of single mode resonator, since in the odd mode at the
tapping point its short circuit. So the loading element
does not contribute any coupling here. Hence the odd
mode resonance frequency is dependent only on square
open-loop parameters (i.e. length of resonator (a), width
of resonator (w) and gap of open loop (g)). But in the
even mode it causes the resonant frequency with varying
the width of loading element (‘W’), and width of tapping
element (‘d’). Figure 3–5 shows the variation of even
mode resonant frequency with ‘W’and ‘d’.
0
-30
-40
-50
-60
Even mode
Odd mode
-20
-40
-60
g=0.3mm
g=0.7mm
g=0.9mm
g=1.3mm
-80
-100
1.02
1.04
1.06
0
Even mode
1.06
1.08
1.1
1.12
Frequency (GHz)
1.14
1.16
Figure 3. Modal-resonant characteristics of the proposed
dual-mode microstrip open-loop resonator for g=0.9mm
and d=1.1 mm.
To excite the resonator, weakly coupled ports are used.
For a single value of ‘W’ the two modes exhibit same
resonance frequency. As ‘W’ increases/decreases, the two
modes split. Smaller‘W’, shifts resonance frequency of
even mode to right. Larger ‘W’, shifts resonance frequency
of even mode to left. Due to short circuit at tapped point
no charge or current in the odd mode case in the loading
Vol 9 (47) | December 2016 | www.indjst.org
1.14
1.16
Odd mode
Even mode
-10
-20
-30
-40
d=0.5mm
d=0.7mm
d=1.1mm
d=1.3mm
-50
-60
1.04
1.08 1.1 1.12
Frequency (GHz)
Figure 4. g-dependence of modal resonant characteristics
of the proposed dual-mode microstrip open-loop resonator
for W=8.755 mm and d=1.1 mm.
S21 magnitude (dB)
magnitude (dB)
-20
S
21
0
W=9.805mm
W=9.215mm
W=8.755mm
-10
1.02
element, and maximum current in the even mode case
in loading element. There is a finite pole (transmission
zero) in the insertion loss graph as the modes diverges.
The finite pole is on right side if variable frequency
component is more than fixed frequency component and
on left side if fixed frequency component is more than
variable frequency component.
S21 magnitude (dB)
3. Characteristics
-70
1
1.05
1.1
Frequency (GHz)
1.15
1.2
Figure 5. d- dependence of modal resonant characteristics
of the proposed dual-mode microstrip open-loop resonator
for W=8.755mm and g=0.9 mm.
4. Deign Procedure for Openloop Resonator
The key parameters of the resonator:
The main parameters are length of resonator (a),
Indian Journal of Science and Technology
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Design of Narrowband Band Pass Filter using Open-loop Square Resonators with Loading Element
Figure 6. Length calculation of open-loop resonator from line guage.
From the substrate details (dielectric constant, loss
tangent, height of the substrate) and frequency of
operation and the configuration (either microstripline or
stripline) we can find the length of resonator (since it is
a half wave length resonator), and width of resonator by
the characteristic impedance of the resonator. From the
Figure 6 the length of the resonator which is half wave
length resonator (47.40255 mm). So the side of resonator
is (1/4th of the resonator length (11.85 mm)).
4.2 Width of resonator
From Figure 7 it is clear that there is relation of between
the insertion loss (S21) and bandwidth (BW) of the
resonator. The requirements of low insertion loss and
narrow band width of filter to design is a challenge here.
So proper width of the resonator is chosen so that for the
narrowband application along with low insertion loss
characteristics.
4
Vol 9 (47) | December 2016 | www.indjst.org
170
-0.55
Bandwidth (MHz)
4.1 Length
-0.5
Insertion loss (dB)
width of resonator (w), gap of the resonator (g). Since it’s
an open-loop square resonator length and width of the
resonator are almost equal.
160
-0.6
-0.65
150
-0.7
-0.75
0.4
0.6
0.8
1
1.2
1.4
1.6
Width (mm)
1.8
2
2.2
140
Figure 7.
Width of the open-loop resonator vs.
insertion loss and bandwidth.
4.3 Gap
Now the open loop gap is going to choose so that oddmode resonance frequency is going to exactly coincide
with center frequency for the band pass filter design.
Figure 8 shows the microstrip width of the loading element
vs. insertion loss at odd and even-mode frequencies
and Figure 9 shows the microstrip width of the loading
element vs. resonant frequencies variations of dual-mode
open-loop square resonator.
Indian Journal of Science and Technology
A. Venkata Varunbabu Mannam and B. Yedukondala Rao Veeranki
individual section of resonator is shown. Each resonator
is separated by NRN coupling element here. The port
dimensions are given in Figure 12 and the NRN coupling
element is shown in Figure 13 along with dimensions.
At last in Figure 14 shows the frequency response of
the given design in Figure 9 using EM software15and the
response is plotted here.
-0.2
-0.3
Insertion loss (dB)
-0.4
-0.5
-0.6
-0.7
loss at even-mode frequency
loss at odd-mode frequency
0.2
6
Figure 8. Width of the loading element vs. insertion loss at
odd and even-mode frequencies.
Figure 10. Quad-section using NRN coupling element.
0.6
0.9
odd-mode resonance frequency
even-mode resonance frequency
transmission zero frequency
6.7
12.4
2.8
2.6
2.4
1
4.25
3
57.91
4.8
4
4.5
5
5.5
Width of loading element (mm)
3.5
-1
3.5
12.4
-0.9
Frequency (GHz)
2
1
-0.8
2.2
0.4
2
4
4.5
5
Width of loading element (mm)
5.5
12.5
6
Figure 9.
Width of the loading element vs. resonant
frequencies variations.
5. Simulation Results and
Discussions
Figure 11. Single unit dimensions.
7.3
2.4
1.8
3.5
1
5.1 Q
uad-section Mixed Coupling using
NRN Coupling Elements (on 2.5
Substrate)
The quad-section asymmetric response is obtained
using the Teflon substrate having relative dielectric of
2.5, substrate height of 1.5875mm and loss tangent of
0.0009 in strip line technology. The metal strip is shown
in the Figure 10 for the entire quad section. In Figure 11
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0.2
Figure 12. Port dimensions.
Indian Journal of Science and Technology
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Design of Narrowband Band Pass Filter using Open-loop Square Resonators with Loading Element
loss it’s better to go the other form of mixed coupling
here. When the resonators are in opposite orientation
then it is called mixed coupling which are separated by
spacing ‘ s ’ and offset by ‘d’. Here two structures are
proposed. Out of which one is tri-section and the other is
the quad-section. These two are implemented in strip line
technology on Teflon substrate.
0.4
12.4
0.4
2
1
6.4
2.0
Figure 13. NRN (first and third NRN are equal length of 2
mm, second NRN is 1.91mm length).
0.2
S
0.2
21
11
-40
3.32
2.35
-80
1.5
2
Frequency (GHz)
2.5
3
0.37
Figure 14. S-parameters of the Quad-sec using NRN
coupling element.
The metal strip of teflon substrate having relative dielectric
of 9.2 is shown in the Figure 15 for the entire quad section.
In Figure 16 individual section of resonator is shown.
Each resonator is separated by NRN coupling element
here. The port dimensions are given in Figure 17 and the
NRN coupling element is shown in Figure 18 along with
dimensions. At last in Figure 19 shows the frequency
response of the given design using EM software 17and the
response is plotted. After observing these two simulations
it’s clearly understood that the structure itself is showing
greater attenuation which is not used for practical
purpose. So any other method leads to decrease in the
insertion loss, and maintain the remaining properties
same. Since this type of Mixed coupling is leads to more
Vol 9 (47) | December 2016 | www.indjst.org
6.6
Figure 16. Single unit dimensions.
4.3
0.26
5.2 Q
uad-section Mixed Coupling using
NRN Coupling Elements (on 9.2
Substrate)
1
2.67
6.4
-60
2.73
S
-100
1
31.4
0.3
-20
6
0.2
Figure 15. Quad-section using NRN coupling element.
0
S-parameters (dB)
0.2
1
0.2
Figure 17. Port dimensions.
Indian Journal of Science and Technology
A. Venkata Varunbabu Mannam and B. Yedukondala Rao Veeranki
0.9
0.2
1.5
1
1.0
4.45
4.7
3.8
0.2
13.4
6.6
6.8
0.75
Figure 18. NRN element.
13.5
0
S11
S-parameters (dB)
-20
Figure 21. Single unit dimensions.
10.5
2.142
-40
S21
-60
1
-80
-100
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
Frequency (GHz)
Figure 19. S-parameters of the Quad-section using NRN
coupling element.
0.5
5.3 D
irect Mixed Coupling (without NRN
Coupling Element)
Figure 22. Port dimensions.
5.3.1 Tri-section
0
S
11
-20
S-parameters (dB)
Direct Mixed Coupling (without NRN coupling element)
for the entire tri section shown in Figure 20. In Figure 21
individual section of resonator is shown. Each resonator
is separated by NRN coupling element here. The port
dimensions are given in Figure 22 and the S-parameters
of the tri-section direct mixed coupling obtained using
EM software as shown in Figure 23 and the response is
plotted.
-10
-30
S
-40
21
-50
-60
-70
-80
-90
1
1.2
1.4
1.6
1.8
2
2.2
Frequency (GHz)
2.4
2.6
2.8
3
2
1
13.9
Figure 23.
coupling.
0.2
0.5
0.9
43.7
Figure 20. Tri-section direct mixed coupling.
Vol 9 (47) | December 2016 | www.indjst.org
S-parameters of the tri-section direct mixed
The tri-section asymmetric response is obtained
using the Teflon substrate having relative dielectric of 2.5,
substrate height of 1.5875mm and loss tangent of 0.0009
Indian Journal of Science and Technology
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Design of Narrowband Band Pass Filter using Open-loop Square Resonators with Loading Element
in stripline technology. The metal strip is shown in the
Figure 13for the entire tri-section. In Figure 13individual
section of resonator is shown. The port dimensions are
given in Figure 13along with dimensions. At last in Figure
14 shows the frequency response of the given design in
using EM software 17and the response is plotted here. The
center frequency of the structure is at 2.0041GHz, with
insertion loss value of -1.20781dB, the transmission zero
is frequency 2.17213GHz, with value of -63.5681dB. The
return loss maximum over passband is -11.6dB. The flat
region is over 1.9678 GHz to 2.06852 GHz. The bandwidth
of the tri-section filter is 132MHz. The over-all tri-section
size is 0.461λg× 0.1412λg.
2.142
10.5
1
0.5
Figure 26. Port dimensions.
Quad section direct Mixed Coupling for the entire quad
section shown in Figure 24. In Figure 25 individual
section of resonator is shown. Each resonator is separated
by NRN coupling element here. The port dimensions are
given in Figure 26 and the S-parameters of the tri-section
direct mixed coupling obtained using EM software as
shown in Figure 26 and the response is plotted.
0
S
-10
11
-20
S-parameters (dB)
5.3.2 Quad-section
-30
-40
S
21
-50
-60
-70
-80
1
13.9
-90
-100
1
0.2
2
0.5
1.4
1.6
1.8
2
2.2
Frequency (GHz)
2.4
2.6
2.8
3
57.95
0.85
Figure 24. Quad-section direct mixed coupling.
0.9
Figure 27.
S-parameters of the Quad-section
direct mixed coupling.
Figure 25. Single unit dimensions.
The quad-section asymmetric response is obtained
using the Teflon substrate having relative dielectric of 2.5,
substrate height of 1.5875mm and loss tangent of 0.0009
in strip line technology. The metal strip is shown in the
Figure15 for the entire tri-section. In Figure 15 individual
section of resonator is shown. The port dimensions are
given in Figure 15along with dimensions. At last in Figure
16 shows the frequency response of the given design in
Figure 14 using EM software 17and the response is plotted
here.
The center frequency of the structure is at 2.0246GHz,
with insertion loss value of -1.484dB, the transmission
zero is frequency 2.18GHz, with insertion loss value of
-78.51dB. The return loss maximum over pass band is
-9.992dB. The flat region is over 1.9628 GHz to 2.0702
Vol 9 (47) | December 2016 | www.indjst.org
Indian Journal of Science and Technology
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4.7
3.8
13.4
6.7
0.8
13.5
4.6
1.5
8
1.2
A. Venkata Varunbabu Mannam and B. Yedukondala Rao Veeranki
GHz. The bandwidth of the quad-section filter is 132MHz.
The over-all tri-section size is 0.611λg× 0.1412λg.
6. Conclusions
The design of compact microwave filters below 3 GHz
remains an active area of research due to great demand
from the wireless communication industry within this
band and comparatively large physical size of conventional
resonators. Microstrip square open loop resonator suits
with greater ease due to its compact size and versatility.
In this paper a compact design technique was studied
which is based on the open loop resonator with a loading
element. Moreover, the in-band response of the filter was
not compromised by the size reduction design techniques.
The tri-section and quad-section asymmetric response
is obtained using the Teflon substrate having relative
dielectric of 2.5, substrate height of 1.5875mm and loss
tangent of 0.0009 in stripline technology. The center
frequency of the structure is at 2.0246GHz, with insertion
loss value of -1.484dB, the transmission zero is frequency
2.18GHz, with insertion loss value of -78.51dB. The return
loss maximum over passband is -9.992dB. The flat region
is over 1.9628 GHz to 2.0702 GHz. The bandwidth of the
quad-section filter is 132MHz. The over-all tri-section
size is 0.611λg× 0.1412λg.
7. References
1. Mansour RR. Filter technologies for wireless base stations.
IEEE Microwave Magazine. 2004; 5(1):68–74.
2. Hong J. Reconfigurable planar filters. IEEE Microwave
Magazine. 2009;10(6):73–83.
3. Nisenoff M, Pond JM. Superconductors and microwaves.
IEEE Microwave Magazine. 2009; 10(3):84–95.
4. Khanna S, Majumder D, Kumar V, Prasad S, Islam A. Impact
of temperature variation on resonant frequency of active
grounded inductor-based bandpass filter. Indian Journal of
Vol 9 (47) | December 2016 | www.indjst.org
Science and Technology. 2016 Aug; 9(33).DOI:10.17485/
ijst/2016/v9i33/99505.
5. Ansari MS, Ravindranath SVG, Bhatia MS, Patidar RK,
Navathe CP. Application of wavelet transform for analysis
of radiated electromagnetic interference in a high power
terawatt laser setup. Indian Journal of Science and Technology. 2012 Nov; 5(11).DOI:10.17485/ijst/2012/v5i11/30655.
6. Plesca AT. Mechanical analysis of power electromagnetic
contactors. Indian Journal of Science and Technology. 2013
Aug; 6(8).DOI:10.17485/ijst/2013/v6i8/36353.
7. Jegan G, Juliet AV, Silvia MF, Krishna GBVS. Novel design
and performance analysis of rectangular frequency reconfigurable micro strip patch antenna using line feed technique for wireless applications. Indian Journal of Science
and Technology. 2016 Aug; 9(29).DOI:10.17485/ijst/2016/
v9i29/98582.
8. Srikanth S, Jeyalakshmi V. Compact UWB micro strip
band pass filter with open circuited stubs. Indian Journal
of Science and Technology. 2015 Jul; 8(13).DOI:10.17485/
ijst/2015/v8i13/58531.
9. Hong J, Lancaster M. Canonical microstrip filter using
square open-loop resonators. Electronics Letters. 1995;
31(23):2020–2.
10. LancasterMJ. Couplings of microstrip square open-loop
resonators for cross-coupled planar microwave filters. IEEE
Transactions on Microwave Theory and Techniques. 1996;
44(12):2099–109.
11. Kong JS.Microstrip cross-coupled trisection bandpass filters with asymmetric frequency characteristics. IEEE Proceedings on Microwaves, Antennas and Propagation. 1999;
146(1):84–90.
12. Hong JS. Design of highly selective microstrip bandpass
filters with a single pair of attenuation poles at finite frequencies. IEEE Transactions on Microwave Theory and
Techniques. 2000; 48(7):1098–107.
13. Sagawa M, Takahashi K, Makimoto M. Miniaturized hairpin resonator filters and their application to receiver frontend MIC’s. IEEE Transactions on Microwave Theory and
Techniques. 1989; 37(12):1991–97.
14. Lee S, Tsai C. New cross-coupled filter design using improved hairpin resonators. IEEE Transactions on Microwave Theory and Techniques. 2000; 48(12):2482–90.
15. IE3D Version 14.10. Zeland Software Inc., Fremont, CA;
2008.
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