Author
homestaychanglun-kedah
View
225
Download
0
Embed Size (px)
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
1/29
1
STUDY AND DESIGN OF A DUAL-MODE MICROSTRIP OPEN-LOOP
RESONATORS AND FILTERS USING SONNET LITE SIMULATION SOFTWARE
SUBMITTED BY:
NIK KHATIJAH BINTI NIK MUSTAFFA
(HE100082)
SUPERVISOR:
DR SAMSUL HAIMI BIN DAHLAN
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
2/29
2
DESIGNING A DUAL MODE MICROSTRIP OPEN LOOP RESONATORS AND
FILTERS AT 5.7 GHZ FOR WLAN APPLICATIONS.
ABSTRACT
Bandpass filters play a significant role in wireless communication systems. Transmitted and
received signals have to be filtered at a certain center frequency with a specific bandwidth. A
dual mode microstrip open loop resonators and filter at 5.7 GHz for wireless local area network
(WLAN) are designed using sonnet lite simulation software. Reflection coefficient and
transmission coefficient of the filter are reported. The simulated and measured filter performance
are presented.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
3/29
3
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND
With the rapid development of wireless and mobile communication systems, there is an
increasingly demands for new technologies to meet the challenge for smaller size, high
performance, multi-frequency and cheaper manufacturing cost. Filters are one of the most
important components must be found in the transmitter or receiver. Filtering application
is most crucial in a system as it will discriminate between wanted and unwanted signal
frequencies. Bandpass filter is a passive component which is able to select signals inside
a specific bandwidth at a certain center frequency and reject signals in another frequency
regions, which have the potential to interfere the information signals. In designing the
bandpass filter, we are faced the question, what is the maximal loss inside the pass
region, and the minimal attenuation in the reject or stop regions, and how the filter
characteristic must look like in transition region. Thus, filter size is one of the concern in
the filter design. The filter is design to ensure that it can fit into the electronic devices.
Besides, the losses of the filter are playing an important role because they will affect the
performance of the filters. Microstrip filters is widely used and apply in many
RF/microwave circuits and systems [1]. In general, microstrip bandpass filters can be
designed using single or dual mode resonators. Band pass filter require precise
transmission characteristics that allow a desired band of signals to pass through the two
port network. Thus, between a transmitter and transmitting antenna, a band pass filter
may be used to attenuate unwanted signals and harmonic components that may cause
interference to other users of the electromagnetic spectrum. Conversely, between an
antenna and a receiver, a band pass filter will reject out of band signals that may cause
interference within the receiver, especially if they are at a high signal level in comparison
with the desired signals. Dual mode resonators are attractive because each dual mode
resonator can be used as a doubly tunable resonant circuit. Therefore the number of
resonators in a filter can be reduced by half, thus resulting in a compact configuration.
Various kinds of dual mode resonators have been investigated, including the circular ring
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
4/29
4
[2], square loop [3], and triangular patch [4]. Meanwhile, several new types of dual mode
resonators [5] have been reported for filter applications recently. Practically, some special
applications require high selectivity on only one side of the pass band, but less or none on
the other side. In such cases, using filters with asymmetric frequency responses would be
desirable [6].
In this project, the type of miniature microstrip dual-mode open loop resonator for filter
applications is introduced. The dual-mode open loop resonator is developed. The open-
loop resonator is well known for its flexibility to design cross-coupled resonator filters, as
well as its compact size. It will be shown that the proposed dual-mode open-loop
resonator has a size that is the same as the single-mode open-loop resonator, which,
however, is much smaller than the conventional dual-mode loop resonator [3]. The size
of the dual-mode open-loop resonator is only approximately one-quarter of the dual-
mode loop resonator, which is a significant size reduction. There have some different of
distinct characteristics between the dual-mode open-loop resonator and the conventional
dual-mode loop resonator. The study of filter parameters and the effect to filter response
was also presented. This information is important especially for circuit optimization
work.
In this project bandpass filters based on dual-mode resonator are design at 5.7 GHz and
verified using SONNET LITEPlus software to optimized and simulate the circuits with
the microstrip calculator software to calculate related formulae for the design.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
5/29
5
1.2 AIMS AND OBJECTIVES
There are several objectives that have been outline to complete this analysis of dual
mode microstrip open loop resonators and filters at 5.7 GHz. This project designs a
dual-mode microstrip open loop resonators and filters at 5.7 GHz by using SONNET
Lite simulation software. This objective helps to gain fundamental knowledge in
microstrip filter. This project also to simulate and analyze the performance of
bandpass filter operating at frequency range of 5 GHz to 6 GHz and to measure the
frequency responses of the dual mode resonator and filter.
The project aims to design a microstrip bandpass filter which is simple and easy to
fabricate. The design filter must be a dual mode bandpass device that resonates in the
frequency range of 5 GHz to 6 GHz.
On the other hand, this project aims to design a dual-mode microstrip open loop
resonators and filters at 5.7 GHz where the filter will be unique, simple, and high-
performing. Through this project, we will have a better understanding of the
microstrip bandpass filter properties.
1.3 PROJECT MOTIVATION
The project motivation is to design the microstrip bandpass filters that are to fulfill
the masters project requirement. After completing the literature review throughout
the journals, knowledge in filter design has widen. The goal of this project is todesign a simple, high performing, and small size microstrip bandpass filter that has
results comparable to those published.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
6/29
6
CHAPTER 2
LITERATURE REVIEW
2.1 Microstrip Filter
In modern wireless and mobile communication systems, Radio Frequency (RF) and microwave
filter are important and essential components. No doubt, filters are playing an important role in
the RF and microwave applications. Filters with smaller size, lighter weight, higher performance,
and lower insertion loss are of high demand. Microstrip filters can fulfil the requirements stated
above. Besides wireless and mobile communication systems, low-temperature co fired ceramics
(LTCC), high temperature superconductor (HTS), monolithic microwave integrated circuits
(MMIC), micro electromechanic system (MEMS) and micromachining technology, have driven
the rapid development of the new microstrip filter than other microwave and RF filters.
Microstrip filters can be designed in various patterns depending on different requirements. Each
microstrip filter consists of its individual properties and characteristics. The common microstrip
designs that available in market are such as rectangular patch filter, circular patch filter,
triangular patch filter and etc.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
7/29
7
2.1.1 Microstrip Lines
Microstrip is a planar transmission line that basically consists of a thin-film strip in intimate
contact with one side of a flat dielectric substrate, with a similar thin-film ground-plane
conductor on the other side of the substrate. It is similar to stripline and coplanar waveguide, and
it is possible to integrate all three on the same substrate. According to Encyclopedia, microstrip
was developed by ITT laboratories by Grieg and Engelmann in December 1952 as a competitor
to stripline. According to Pozar, the early microstrip work used fat substrates, which allowed
non-TEM7 waves to propagate which makes results unpredictable. In the 1960s the thin version
of microstrip started became popular. Microstrip can be fabricated using printed circuit board
(PCB) technology and is used to convey microwave frequency signals. It consist of a conducting
strip separate from a ground plane by a dielectric layer which known as substrate.
Microstrip can be used to design antennas, couplers, filters, power dividers and etc. The material
costs are lower than the traditional waveguides since the entire microstrip is just a patterned
metal and a ground plane only, and it also much lighter and more compact than the waveguides.
Since microstrip is not enclosed as a waveguide, it is susceptible to crosstalk and unintentional
radiation. Unlike stripline, microstrip can mount all the active components on top of the board.
However, the disadvantages are that microstrip generally has lower power handling capacity and
higher losses. External shield may be needed for circuits that require higher isolation such as
switches. In this project, microstrip has been chosen for the filter design because it is a proven
technology and the shielding problem can be solved easily by encapsulating the filter in a
metallic box. Besides, crosstalk and unintentional radiation are not an issue in this project as
well.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
8/29
8
2.1.1.1 Dielectric Constant
Microstrip can be fabricated on different substrates based on the requirement of the design. For a
lower cost, microstrip devices can be built on the ordinary Duroid 6006 substrate. Dielectricconstant is a measure of the extent to which it concentrates electrostatic lines of flux. For
example, FR-4 has a dielectric constant of 4.4 and R6006 duroid has 6.15 at frequency of 10
GHz. And by definition, the dielectric constant of vacuum is equal to 1. Dielectric constant is
frequency dependent.
2.1.1.2 Effective Dielectric Constant
In general, the dielectric constant of the substrate will be different (and greater) than air, so the
wave is travelling in an inhomogeneous medium. In consequence, the propagation velocity is
somewhere between the speed of radio waves in the substrate, and the speed of radio waves in
air. This behaviour is commonly described by stating the effective dielectric constant of the
microstrip. Effective dielectric constant is an equivalent dielectric constant of an equivalent
homogeneous medium. As part of the fields from the microstrip conductor exists in air, the
effective dielectric constant is less than the substrate's dielectric constant.
2.1.1.3 Characteristic Impedance
The characteristic impedance, Zo is important in microstrip lines design, it will affects the
reflection loss, S11. The reflection loss is related to the characteristic impedance and also load
impedance by formula, S11= . In order to minimize the reflection loss at the input port, the
characteristic impedance of microstrip must be equal to the input of the impedance. Most of the
input ports are designed at 50 ohm to prevent any reflections. The characteristic impedance is
also a function of height (H) and width (W) of microstrip lines. Note that effective dielectric
constant value is required for the microstrip characteristic impedance calculation. The
characteristic impedance of microstrip lines can be calculated by using formulas below.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
9/29
9
When
(
)
When
*
+
The very first step in this project is to design the microstrip lines that can achieve 50 ohm of
characteristic impedance, . From the formulas above, there are three variables in thecalculation which are Width (W) and Height (H). Since the and height is constant forthe substrate, the only variable is the width of the microstrip line.
Since the formula is quite complicated, we have to substitute different W value in order to get 50
ohm characteristic impedance. At first, it has to verify the ratio of W/H and determine which
formula to be used. It is time consuming for the calculation on different substrate. Fortunately,
some of the web application and software are able to calculate the width of the microstrip lines
by entering the desire characteristic impedance, height of the substrate and dielectric constant of
the substrate. Then the software will perform the calculation within seconds and shows the value.
It has simplified the microstrip lines design work and most importantly consume less time. For
instance, one of the useful software was used for characteristic impedance calculation in this
project is microstrip calculator. The software is easy to control and able to get the width value
easily by key in height of the substrate, thickness of the strip, and dielectric constant of the
substrate. The microstrip width calculation will be cover in Methodology part.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
10/29
10
2.1.2 Microstrip Resonators
Microstrip resonators can be designed in various patterns. Before designing the microstrip band
pass filter, it has to do some literature studies through IEEE Xplore about the microstrip
resonators. Besides, it is also to ensure that the effort spent in design has not been researched by
others nor published in the IEEE Xplore before. The author has selected the common types of
resonators to be discussed in the following chapters. The types of resonators that covered are
dual mode microstrip open loop resonator.
2.1.2.2 Microstrip Open Loop Resonators
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
11/29
11
CHAPTER 3
METHODOLOGY
There are different method carrying out research in the field of RF/Microwave system, like
experiment and simulation. The building of a design and the testing of it in practical experiment
is an expensive and time-consuming method. To minimize time and cost, this research focus on
simulation experiment based on Sonnet Lite simulation software in order to simulate frequency
response for resonators and filters.
The Sonnet EM analysis is based on a method-of-moments technique. The circuit metal is
first meshed into small subsections. The EM coupling between each possible pair of subsections
is calculated and this fills a big matrix. The matrix is inverted, yielding all currents everywhere
in the circuit metal. This, in turn, determines things like S-parameters, which can be used in other
analysis programs.
The Sonnet analysis has very high accuracy because it calculates all couplings between
subsections using a 2-D Fast Fourier Transform (FFT). In signal processing, application of the
FFT requires uniform time sampling of a signal. In EM analysis, the FFT requires uniform space
sampling across the two dimensions of the substrate surface. Thus the analyzed circuit metal falls
on a uniform underlying FFT mesh. The FFT approach also requires the circuit to exist inside a
conducting, shielding box. Approximations are available to include radiation. A common
alternative technique requires a four dimensional numerical integration to calculate each pair-
wise coupling. This approach has the advantage of eliminating the underlying uniform mesh,
however, it comes at the cost of sometimes extensive numerical integration time and the
additional error involved in the numerical integration process. The FFT used by Sonnet quickly
calculates all couplings to full numerical precision. In contrast to the FFT approach, numerical
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
12/29
12
integration requires an open environment allowing radiation while a shielded environment must
be approximated.
When and if a serious planar numerical integration based EM tool becomes freely
available, the user will find the relative advantages and disadvantages tend to compliment
Sonnet's FFT based tool.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
13/29
13
CHAPTER 4
DATA ANALYSIS AND RESULT
4.1DESIGN OF THE DUAL MODE MICROSTRIP OPEN LOOP RESONATOR
In this project, all the simulation are done by Sonnet Lite software. The design and result of
dual mode microstrip open loop resonator is shown in Figure 4.1 (a) and Figure 4.1(b) below.
Figure 4 (a) shows the layout of a dual mode microstrip open loop resonator on a substrate
with a relative dielectric constant of 10.8 and a thickness of 1.27 mm. All dimensions are inmillimeters. A loading element with a variable parameter W is tapped from inside onto the
open loop. When W varies, the modal resonant characteristic is changed. For the
demonstration, we use a Sonnet Lite simulator to simulate the resonant frequency response of
the proposed dual mode open loop resonator. To excite the resonator, two ports are weakly
coupled to the resonator. The simulated result are plotted in Figure 4.1(b).
Figure 4.1 (a): Layout of a dual-mode microstrip open loop resonator
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
14/29
14
For a loading element, W= 9.3 mm, two modes exhibits the same resonant frequency. The
simulated result are in Figure 4 (b). Two modes will split if W is increased or decreased
from value W = 9.3 mm.
Specify unit for length and frequency where length is in mm and frequency in GHz.
Dielectric layer. Set the thickness 1.27 mm and relative dielectric constant 10.8
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
15/29
15
Box size and cell size setting.
Metal type
Specify Frequency from 1.04 GHz to 1.12 GHz.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
16/29
16
Figure 4.1(b) : Graph S11 and S21.
Figure 4.1 (b) shows the modal resonant characteristic of the proposed dual mode microstrip
open loop resonator for g=0.9 mm, d= 1.1 mm and w=9.3 mm. Figure 3.3 shows the simulated
and measured return losses and insertionlosses. Rrom the figure, the measured center frequency is 1.655 GHz, which is very
close to the simulated value of 1.69 GHz (error 2.07%). The measured and simulated
3-dB bandwidths ( 11S10 dB) are given by 9.09% and 12.79%, respectively. Alsoshown in the figure are the simulated S11 and S21by using the network model. With30
reference to the figure, the measured center frequency is 1.65 GHz, which is very
close to the simulated value of 1.69 GHz (error 2.37%). The measured 3-dB
bandwidth ( 11S10 dB) by using network model is given by 10.40%. Withreference to the figure, the models predict the S11 and S21 reasonably well.
The error might caused by the gap distance. From the simulation design the
capacitive coupling gap is 0.01 mm. However, such narrow gap is difficult tofabricate by the equipment in the laboratory. Few Duroid 6006 substrates have been
fabricated and experiment. At the end of the day this is the best result the author able
to collect.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
17/29
17
Figure 4.2 (a): Layout of a dual-mode microstrip open loop resonator with W = 9.1
mm.
Figure 4: Graph S11 and S21 for w=9.10
The smaller W results in a mode being shifted to a higher frequency.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
18/29
18
Figure 5: Layout of a dual-mode microstrip open loop resonator with W = 9.5 mm.
Figure 6: Graph for S11 and S21
The larger W shifts a mode to a lower frequency.
In all the cases, only one modal resonant frequency is affected, while the other one is
hardly changed. It is shows that the even mode is affect to the resonant frequency but the odd
mode in unaffected to the resonant frequency. The tapping point of the loading element, W is a
virtual ground for the odd mode. Hence, the loading element does not affect the odd mode
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
19/29
19
characteristic and its resonant frequency. The loading element is affected to the even mode
where the change of W makes the resonant frequency of the even mode shifted.
The transmission zero is allocated on the high side of the two modes when the even
mode frequency is higher than the odd mode frequency. The transmission zero is allocated on the
low side when the even mode frequency is lower than the odd mode frequency. The transmission
zero is closely with the even mode.
The unique property of the even mode will proposed the dual mode resonator for
designing the filters.
Another characteristic of the dual mode open-loop resonator is the two modes are not
coupled to each other even after the modes are split. From the theory, if the two split mode
frequencies are equal to the two self resonant frequency, respectively there is no coupling
between the two resonators.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
20/29
20
FILTER APPLICATION
n-pole filter can be constructed using n/2 dual mode open loop resonators. Basic coupling
structures of this filter can be found in [6] where no coupling between the even and odd
modes has been implicated.
To design this filter, needs to allocate the modal resonant frequencies within the desired
passband.
For a given center frequency, the perimeter of the open loop is approximately a half
wavelength, which sets the resonant frequency of the odd mode. Once the loop size is found,
the odd mode resonant frequency can be tuned to the desired one by varying the gap gof the
dual mode open loop resonators.
When g is changed to the higher value, the odd mode resonant frequency is effectively
shifted. The even mode resonant frequency is mainly determined by the size of the loading
element and can easily be tuned by several parameters such as W and d.
The W controls the capacitive loading so as to change the even mode resonant frequency. In
addition, the even mode resonant frequency can be easily controlled by varying the
dimension of d, when d is changed from 0.3 to 1.3 mm, the even mode resonant frequency is
effectively shifted to the higher value, 0.983 to 1.152 GHz.
The smaller d, results in a larger inductive loading and a lower resonant frequency
for the even mode. The easy control of modal resonant frequencies allows one to control
filterbandwidth because the separation of the modal resonant frequencies is proportional to
the bandwidth.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
21/29
21
Bandpass filter
Figure 7 shows the filter where the characteristic of filter is a finite frequency zero
on the low side of the passband. The filter use a single dual mode open loop resonator. The
even mode frequency for filter B has to be lower than the odd mode frequency.
Figure 10 shows the simulated performance of the filter. The measured center
frequency of 0.95 GHz is slightly lower than the simulated 1.01 GHz and a normalized
frequency axis is used for comparison. It can be seen that the measured frequency response
is very similar to the simulated one. The filter exhibits a higher selectivity on the low side of
the passband because of the finite frequency transmission zero. The first spurious does not
occur at 2fo, but at a higher frequency.
Figure 7: Layout of filter B. W=10.9 mm. because the even mode frequency in order to
place a desired transmission zero on the low side of the passband.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
22/29
22
Figure 8: Measured and simulated frequency response of filter B in Figure 7.
Filterhigher order filter based on coupled dual mode open loop resonator.
To prove that when two dual mode open loop resonator are coupled, there are only
couplings between the same mode of resonator (odd mode resonator1=odd mode resonator
2), (even mode resonator 1=even mode resonator 2)
For the purpose, an inter resonator coupling structure is proposed in Figure below.
Where two identical dual mode open loop resonators are approximately placed in opposite
orientations with a spacing s to facilitate the coupling.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
23/29
23
Figure 9: Coupled dual mode open loop resonator.
Figure 10: resonant response of the coupled resonator structures
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
24/29
24
Four pole dual mode filter
The coupling structure proposed in [6] for a multipole dual mode resonator filter is also
applicable for the type of dual-mode resonator .In Figure 13, the filter has a very compact
size and uses a resonator structure with a small offset of the two coupled resonator for a fine
adjustment of the couplings. The simulated and measured performance of the filter are
shown in Figure 14. The simulated performance is fo=?????.The filter shows a finite
frequency zero on the high side of the passband, which is because the dual mode open loop
resonator used have a higher even mode frequency.
The above four pole filter exhibits a second order finite frequency transmission zero on
one side of the passband for applications such as duplexers where asymmetric
frequency selectivity is desired.
Figure 11: Four pole filter (n=4) composed of two identical dual mode open loop resonators
is developed. The filter has a very compact size and uses a coupled resonator structure in
figure 11, with a small offset of the two coupled resonator for a fine adjustment of the
couplings.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
25/29
25
Figure 12: The filter shows a finite frequency zero on the high side of the passband, which is
because the dual mode open loop resonators used have a higher even mode frequency.
A four pole filter design to produce two transmission zeros, each on the one side of the
passband, leading to a symmetric frequency response is required.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
26/29
26
Figure 13: Layout of the for pole dual mode filter
Figure 14: Symmetric passband with the two desired transmission zero.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
27/29
27
As a matter of fact, a four pole filter can also be designed to produce two transmission zeros,
each on the one side of the passband, leading to a symmetric frequency response if required. In
this case, the two dual mode resonators without any direct couplings between them are cascadedthrough the two nonresonating nodes, as indicated. The two dual mode resonator are also not the
same as shown, one will produce a zero on the high side of the passband, while the other will
produce a zero on the low side of the passband. The result is plotted Figure 16, showing a
symmetric passband with the two desired transmission zeros.
CONCLUSION
A miniature dual mode open loop resonator has been proposed for filter applications. The
characteristics of this new type of microstrip dual mode resonator has been investigated. It has
been shown that the loading element inside the open loop resonator does not affect the odd mode
characteristic and the two modes of this type of dual mode resonator do not couple even with a
mode split. It has also shown that a finite frequency transmission zero is inherently associated
with the even mode. This makes it much easier to design bandpass filters with an asymmetric
response, as no cross coupling is required to generate the transmission zero. The two pole filters
of this type with opposite asymmetric responses have been demonstrated. To this end, a compact
four pole filter using filter using two dual mode open loop resonators has been demonstrated
with a promising performance. In addition, by implementing nonresonating nodes, it has been
shown that the four pole filter can actually produce two separated transmission zeros, each on
one side of the passband.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
28/29
28
The expectation outcomes of this project are:
1. Dual Mode Microstrip Open Loop Resonators can be used like a filters2. Varying of length gap between two resonators can be effect of the filter responses.
REFFERENCE
[1] Jia Sheng Hong, Hussein Shaman, Young Hoon Chun (2007), Dual Mode
Microstrip Open Loop Resonators and Filters, IEEE.
[2] J.-S. Hong and M. J. Lancaster, Microstrip Filters for RF/Microwave
Applications. New York: Wiley, 2001.
[3] I. Wolff, Microstrip bandpass filter using degenerate modes of a microstrip ring
resonator, Electron. Lett., vol. 8, no. 12, pp. 302303, Jun. 1972.
[4] J.-S. Hong and M. J. Lancaster, Bandpass characteristics of new dualmode
microstrip square loop resonators, Electron. Lett., vol. 31, no. 11, pp. 91892,
Nov. 1995.
[5] J. A. Curitis and S. J. Fiedziuszko, Miniature dual mode microstrip filters, in
IEEE MTT-S Int. Microw. Symp. Dig., 1991, pp. 43446.
7/28/2019 Laporan Project 2 Nik Khatijah Nik Mustaffa-1
29/29
[6] R. R. Mansour, Design of superconductive multiplexers using singlemode and
dual-mode filters, IEEE Trans. Microw. Theory Tech., vol. 42, no. 7, pp. 411
1418, Jul. 1994.
[7] J. S. Hong and S. Li, Theory and experiment of dual-mode microstrip triangularpatch resonators and filters, IEEE Trans. Microw. Theory Tech., vol. 52, no. 4,
pp. 12371243, Apr. 2004.
[8] C. Lugo and J. Papapolymerou, Bandpass filter design using a microstrip
triangular loop resonator with dual-mode operation, IEEE Microw. Wireless
Compon. Lett., vol. 15, no. 7, pp. 75477, Jul. 2005.
[9] R. Wu and S. Amari, New triangular microstrip loop resonators for bandpass
dual-mode filter applications, in IEEE MTT-S Int. Microw. Symp. Dig., 2005,
pp. 41944.
[10] J.-S. Hong and M. J. Lancaster, Couplings of microstrip square open-loop
resonators for cross-coupled planar microwave filters, IEEE Trans. Microw.
Theory Tech., vol. 44, no. 11, pp. 20992109, Nov. 1996.
[11] EM Users Manual, ver. 10, Sonnet Softw. Inc., Syracuse, NY, 2005