26 research outputs found
Development of turnable and miniature microwave filters for modern wireless communication
Due to the increasing demand for new wireless services and applications, the high level of integration and the coexistence of multi-standard (MS) or multi-band operations into a single device are becoming defining trends in designing microwave filters. This has driven considerable technological advances in reconfigurable/tunable and miniaturized filters. More specifically, reconfigurable/tunable filters that tune to different frequency bands instead of classical filter banks have great potential to significantly reduce the system size and complexity; while reducing the filter size becomes essential to achieve the highest degree of integration density in compact and portable wireless devices.
In the light of this scenario, the objective of this dissertation is to develop the new design technologies, concepts and filtering configurations for tunable microstrip filters and compact passive microwave filters. To this aim, this dissertation is divided into two main parts.
The first part (Part I) focuses on the designs of novel varactor-tuned microstrip filters with advanced performances. In this aspect, new topologies for realizing tunable lowpass and highpass filters are firstly developed. State-of-the-art performances, including wide tuning range, high selectivity with multiple transmission zeros, low insertion loss and compact size for all the tuning states are obtained in both of these filters. Secondly, two novel classes of tunable bandpass filters are presented. One of them is designed based on varactor-loaded parallel-coupled microstrip lines (PCML) and short-circuited stubs, which allows the lower passband edge together with two transmission zeros located around the lower passband skirt to be reconfigured separately. While the other tunable bandpass filter is
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constructed by the combination of tunable bandpass and lowpass filters, featuring both centre frequency and bandwidth tunabilities, as well as high selectivity with abundant transmission zeros. Furthermore, a new concept of tunable lossy filter is demonstrated, which attempts to achieve an equivalent high-Q tunable performance by using low-Q resonators. This concept makes the presented tunable combline filter interesting for some frequency-agile applications in which the low in-band loss variation and high selectivity are much desired while the absolute insertion loss can be a tradeoff.
The second part (Part II) is devoted to the design of miniaturized passive microwave filters with improved characteristics. For this, the concept of artificial right-handed and left-handed transmission lines are applied to the signal interference filtering topology, which results in a compact circuit size and good out-of-band performance. In particular, for a further size reduction, such filter is implemented in the forms of multilayered structure by using liquid crystal polymer (LCP) technology. Additionally, another two types of miniaturized bandpass filters using stepped impedance resonators are demonstrated, which are implemented based on different fabrication processes (i.e. LCP bonded multilayer PCB technology and a standard planar PCB technology). Among their main features, the compact size, wide passband, broad stopband with multiple transmission zeros and circuit simplicity are highlighted.
For all the proposed design techniques and filtering structures, exhaustive theoretical analyses are done, and design equations and guide rules are provided. Furthermore, all the proposed schemes and/or ideas have been experimentally validated through the design, implementation and measurement of different filters. The fabrication processes of multilayer technology utilized: liquid crystal polymer (LCP) technology and liquid crystal polymer (LCP) bonded multilayer printed circuit board (PCB) technology, are also demonstrated for reference. All of the results achieved in this dissertation make the proposed filters very attractive for their use in modern wireless communication systems.MultiWaves Project (PIRSES-GA-2010-247532) of the Seventh Framework Programme (FP7), European Commission
Development of tunable and miniature microwave filters for modern wireless communications
Due to the increasing demand for new wireless services and applications, the high level of integration and the coexistence of multi-standard (MS) or multi-band operations into a single device are becoming defining trends in designing microwave filters. This has driven considerable technological advances in reconfigurable/tunable and miniaturized filters. More specifically, reconfigurable/tunable filters that tune to different frequency bands instead of classical filter banks have great potential to significantly reduce the system size and complexity; while reducing the filter size becomes essential to achieve the highest degree of integration density in compact and portable wireless devices.
In the light of this scenario, the objective of this dissertation is to develop the new design technologies, concepts and filtering configurations for tunable microstrip filters and compact passive microwave filters. To this aim, this dissertation is divided into two main parts.
The first part (Part I) focuses on the designs of novel varactor-tuned microstrip filters with advanced performances. In this aspect, new topologies for realizing tunable lowpass and highpass filters are firstly developed. State-of-the-art performances, including wide tuning range, high selectivity with multiple transmission zeros, low insertion loss and compact size for all the tuning states are obtained in both of these filters. Secondly, two novel classes of tunable bandpass filters are presented. One of them is designed based on varactor-loaded parallel-coupled microstrip lines (PCML) and short-circuited stubs, which allows the lower passband edge together with two transmission zeros located around the lower passband skirt to be reconfigured separately. While the other tunable bandpass filter is constructed by the combination of tunable bandpass and lowpass filters, featuring both centre frequency and bandwidth tunabilities, as well as high selectivity with abundant transmission zeros. Furthermore, a new concept of tunable lossy filter is demonstrated, which attempts to achieve an equivalent high-Q tunable performance by using low-Q resonators. This concept makes the presented tunable combline filter interesting for some frequency-agile applications in which the low in-band loss variation and high selectivity are much desired while the absolute insertion loss can be a tradeoff.
The second part (Part II) is devoted to the design of miniaturized passive microwave filters with improved characteristics. For this, the concept of artificial right-handed and left-handed transmission lines are applied to the signal interference filtering topology, which results in a compact circuit size and good out-of-band performance. In particular, for a further size reduction, such filter is implemented in the forms of multilayered structure by using liquid crystal polymer (LCP) technology. Additionally, another two types of miniaturized bandpass filters using stepped impedance resonators are demonstrated, which are implemented based on different fabrication processes (i.e. LCP bonded multilayer PCB technology and a standard planar PCB technology). Among their main features, the compact size, wide passband, broad stopband with multiple transmission zeros and circuit simplicity are highlighted.
For all the proposed design techniques and filtering structures, exhaustive theoretical analyses are done, and design equations and guide rules are provided. Furthermore, all the proposed schemes and/or ideas have been experimentally validated through the design, implementation and measurement of different filters. The fabrication processes of multilayer technology utilized: liquid crystal polymer (LCP) technology and liquid crystal polymer (LCP) bonded multilayer printed circuit board (PCB) technology, are also demonstrated for reference. All of the results achieved in this dissertation make the proposed filters very attractive for their use in modern wireless communication systems
The design and fabrication of miniature microwave bandpass filters using multilayer liquid crystal polymer technology
This thesis presents the design and fabrication techniques for miniature microwave
bandpass filters using multilayer liquid crystal polymer (LCP) technology.
As a multilayer technology for microwave devices, LCP is of low cost and light weight. It
also has excellent electrical properties across a wide frequency range. These characteristics
make it promising for the development of next generation microwave devices for
applications across commercial, defence and civil sectors. However, very limited work has
been found in the open literature to apply this technology to the design of miniature
bandpass filters, especially at low microwave frequencies. In addition, the reported work
shows lack of fabrication techniques, which limits the size reduction of multilayer LCP
devices.
To address these problems, this thesis develops advanced fabrication techniques for
sophisticated LCP structures, such as multilayer capacitors, via connections and cavities.
These techniques are then used to support the design of novel miniature bandpass filters for
wideband and narrowband applications. For the design of miniature wideband bandpass
filters, a cascaded approach, which combines highpass and lowpass filters, is presented first
to provide a flexible design solution. This is followed by another novel ultra-wideband
bandpass filter which produces extra transmission zeroes with minimum number of
elements. It does not only have high performance but also a compact structure for high
yield fabrication. For narrowband applications, two types of advanced coupled-resonator
filters are developed. One type produces a very good selectivity at the upper passband edge,
and its spurious-free stopband is extremely wide and of high interference attenuation. The
other type, based on novel mixed-couplings approaches developed in this thesis, provides a
solution to produce almost the same response as the coupling matrix prototype. This type is
used to generate arbitrarily-located transmission zeroes.
All designs presented in this thesis are simulated using CAD design tools and then
validated by measurements of fabricated samples. Good agreements between simulations
and measurements are shown in the thesis
Miniaturised and reconfigurable planar filters for ultra-wideband applications
An increasing demand for electromagnetic spectrum has resulted from the emergence of feature-rich and faster throughputs wireless applications. This necessitates the developments of dynamic reconfigurable or multifunctional systems to better exploit the existing spectrum.
Future wireless devices will be expected to communicate over several bands with various other devices in order to fine tune the services they provide to the user. Each band may require a separate RF transceiver and such modern wireless multi-band multi-mode communication systems call for high performance, highly integrated compact modules. Since the Federal Communications Commission (FCC) released the unlicensed frequency band 3.1-10.6 GHz for ultra-wideband (UWB) commercial communications, the
development race for commercialising UWB technology has seen a dramatic increase around the world.
The aim of this research is to develop reconfigurable planar microwave filters for ultrawideband applications. The project investigates some key design issues of reconfigurable
filters, which are being observed constantly in the latest development and realisation of microwave filters. Both analytical and numerical methods are performed to construct a realistic and functional design. Two different types of frequency reconfigurability are investigated in this thesis: discrete (e.g. PIN diode, Optical switch) and continuous (e.g. varactor diode). Using the equivalent circuits and considering the direct coupled filter structure in most cases, several topologies with attractive features are developed for future communication systems. The proposed works may be broadly categorised into three
sections as follows.
The first section explores a square ring shape close loop resonator along with an opencircuited stub in the symmetry plane. To realise a reconfigurable frequency states within the same spectrum, an innovative approach is developed for this case. An optical or
photoconductive switch, comprised of a silicon die activated using near infrared light is investigated as a substitute of PIN diode and performances are evaluated to compare the feasibilities. In addition, a in-band interference rejection technique via externally coupled Tshape resonator is shown. However, it is observed that both structures achieve significant size reductions by utilising the inner part of the resonators.
To improve the filter selectivity, a convenient design approach generating a pair of transmission zeros between both passband edges and a single zero in the stop band for harmonic suppression is discussed in the second section. Moreover, the development of notched rejection bands are studied and several novel methods to create a single and multiple notched bands employing the square ring shape structure are proposed. On inspection, it is found that the notch structure can be implemented without deteriorating the filter performances. The discussions are supplemented with detailed design examples which are accompanied by theoretical, simulated and experimental results in order to illustrate the filter development process and showcase practical filter performance. The third section reveals a novel highly compact planar dual-mode resonator with sharp rejections characteristics for UWB applications. A bandwidth reconfiguring technique is demonstrated by splitting its even-mode resonance. Filter structure with the dual-mode resonator is shown to have a relatively wide tuning range, significantly low insertion loss and a constant selectivity along with frequency variations in comparison to similar published works. Finally, the earlier dual-mode structure are modified to realise a dual wideband behaviour. A detail analysis with comprehensive design procedures is outlined and a solution for controlling the frequency bandwidths independently according to the application interest is provided. In line with the previous section, experimental verification is presented to support and supplement the discussions
High aspect ratio transmission lines and filters
There are a significant number of microwave applications, where improvement of such qualities as manufacturing costs, size, weight, power consumption, etc. have attracted much research interest. In order to meet these requirements, new technologies can be actively involved in fabrication of microwave components with improved
characteristics. One such fabrication technology is called LIGA (a German acronym with an English translation of lithography, electroforming, and moulding) that allows fabrication of high aspect
ratio (tall) structures, and only recently is receiving growing attention in microwave component fabrication.
The characteristics of high aspect ratio microstrip and coplanar waveguide (CPW) transmission lines are investigated in this thesis. Very low impedance high aspect ratio CPW transmission lines can be realized. A high aspect ratio microstrip folded half wavelength open
loop resonator is introduced. Effective configurations for external and bypass gap coupling with open loop resonators are given. Filters with transmission zeros in the stopband, consisting of high aspect ratio single mode open loop resonators are presented to demonstrate
the advantages of high aspect ratio structures in realizing lower external quality factors or tight coupling. The transmission zeros are created by novel coupling routings. Some of the filters are
fabricated and the filter responses are measured to validate high aspect ratio coupling structures. High aspect ratio diplexers with
increased channel isolation are also designed by appropriately combining filters with transmission zeros.
A wideband bandpass filter design method, based on the electromagnetic bandgap (EBG) concept is introduced in this thesis. The wideband filters are miniaturized as a result of using the EBG
concept in design. An EBG based wideband filter consisting of unit cells that are realized by using high aspect ratio CPW stepped impedance resonators is also presented. The main advantage of this approach is that the high aspect ratio CPW structures make short unit cells practically realizable, resulting in compact filter
structure
Advanced microwave miniature and lossy tunable filters for wireless communication applications
Microwave filters play very important roles in many RF/microwave applications,
which are employed to separate or combine different frequencies. Emerging applications,
such as wireless communications, challenge the design of microwave filters with more
functionalities and higher performance, such as reconfigurable or tunable, compact size,
light weight and lower cost.
In order to meet the increasing challenge requirements, the objective of this
dissertation is to develop new multilayer miniaturized filters, compact lossy microstrip
filters, and reconfigurable lossy filters. To achieve this, this dissertation is divided into
three main parts.
The first part focuses on the design of novel miniature bandpass filter with improved
performance. In this aspect, a novel microstrip bandpass filter using slow-wave open-loop
resonators is presented, which concentrates on the stopband rejection performance to
suppress the harmonic standing wave rather than the passband performance by using
multilayer LCP technology. The multilayer open-loop slow-wave resonator has not only
very compact size, but also exhibits an excellent wider upper stopband resulting from the
dispersion property. Based on this type of resonator, a five-pole bandpass filter has been
proposed, which has good stopband rejection and high selectivity as well as compact size
and light weight.
The second part is devoted to the design of compact lossy filters with improved
performance characteristics. To achieve this, lossy synthesis and extracted-pole
technology are combined together to design microstrip filters with flat passband and high
selectivity. Two six-pole filters has been analysed from the theoretical circuit model to
EM simulations, fabricated to demonstrate the response performance in narrowband and
wideband respectively.
The third part concentrates on the designs of novel varactor-tuned microstrip lossy
bandpass filters. Firstly, state-of-the-art literature review is given to have a general view
of reconfigurable bandpass filter with different tuning centre frequency and bandwidth characteristics. Then, three types of tunable microstrip bandpass filters with resistor
loading under symmetric tuning method are presented to introduce additional loss into
the passband to make it flat over the entire tuning range. The first filter is designed to
control the bandwidth and selectivity. The second one is designed to control the
bandwidth at fixed centre frequency, while the third filter is extended from the first one
to combine resistor loading and cross coupling. Finally, microstrip tunable bandpass lossy
filters with extracted-pole technology are proposed. Three six-pole filters of this type have
been analysed and fabricated. Due to the asymmetric tuning method, the number of tuning
components and dc bias schemes are increased, which is a kind of tradeoff with
performance.
For all the presented filters, theoretical analyses, implementations and
measurements have been given. All of the results achieved in this thesis make the
proposed filters attractive for their applications in modern wireless communication
systems
Self-packaged miniature microwave filters based on multilayer liquid crystal polymer technology
The following thesis is concerned with the development of fabrication techniques
and novel designs for self-packaged, multilayer circuits using liquid crystal polymer
(LCP) materials exclusively, given the favourable characteristics this material has
for microwave circuits.
Fabrication techniques are aimed at the production of miniature, low-profile filters.
Advanced techniques for production of interlayer via connections are investigated
and new methods proposed, with special attention at the lamination process and
production of vertical, inter-layer transitions. Results obtained demonstrate the
fabrication process is reliable for producing multilayer filters, with up to four metal
layers, and via transitions in the region of 0.2 mm diameter.
The fabrication process has been developed during this work is applied to novel filter
designs, covering dual-band filters and lowpass filters. A new structure for dual-
band filter is proposed, using folded multimode resonators (FMSIR). This structure
is validated through the fabrication of two different filters with passbands 1.2/2.4
GHz, and 2.4/5 GHz, showing deep off-band rejection.
Low pass structure covered in this thesis is based on the principle of destructive
interference and aims at low insertion loss and out-of-band rejection higher than
40 dB. Fabricated samples validate the design showing a rejection in the region of
42 dB, with a cuto frequency of 3 GHz. Its small footprint and low insertion loss
allows this type of lters to be used as cleanup filters. All the designs covered in
this work are simulated using CAD tools and then validated by measurements on
fabricated samples
Development of Tunable RF Integrated Passive Devices
Radio frequency (RF) lumped elements are crucial building blocks for designing any type of passives
circuits for RF front-end applications in mobile devices. In particular, high-quality (Q) factor lumped
elements are desirable for improving both insertion loss and noise performance. Integrated passive
devices (IPD) technology is a platform that can provide miniature inductors, and capacitors with high-
Q values that are unattainable with traditional CMOS technologies. Over the past several years, IPD
technology has been used to implement devices such as filters, couplers and impedance-matching
networks for a wide range of system-in-package applications. However, most of the IPD circuits do
not yet have any tunable/reconfigurable functions for use in frequency agile applications.
The objective of this research is to develop tunable integrated passive devices (IPDs) using barium
strontium titanate (BST) and micro-electrical-mechanical-systems (MEMS) technologies. Another
objective is to develop a fabrication process for monolithic integration of MEMS switches and IPD
devices. A 4-mask IPD glass/alumina-based fabrication process is developed at the University of
Waterloo for the first time. Details of the modeling and characterization of high-Q lumped elements,
L and C, are investigated. The RF performance of these elements is compared with that of similar
designs fabricated in a commercial IPD foundry. To highlight the benefits of the IPD process, lumped
element bandpass filters are designed, fabricated, and tested.
BST varactors are integrated with IPD circuits to demonstrate a highly miniaturized tunable
impedance matching network featuring a wide impedance coverage from 2-3 GHz and an insertion
loss of approximately 1 dB. The network promises to be useful in a broad range of wireless
applications. A high performance tunable IPD/BST bandstop filter with a wideband balun as a multichip
module is also proposed. Reconfigurable IPD/BST bandpass filters with tunable transmission
zeros are presented and investigated experimentally for operation under high power levels.
Intermodulation test results are presented for the integrated IPD/BST devices.
Making use of the fact that the IPD fabrication process is amenable to the realization of MEMS
devices, the IPD process originally developed for realizing passive circuits is further expanded to
accommodate monolithic integration of MEMS switches with IPD circuits. Contact-type MEMS
switches are developed, fabricated and tested. Also, a monolithically integrated IPD/MEMS 3-bit
high resolution true-time delay network and high-Q switched-capacitor bank are fabricated and tested
to demonstrate the benefits of integrating MEMS technology with the IPD technology
Advanced RF/microwave filtering circuits for wireless communications and radar applications.
The recent rapid development in modern communication systems has presented some
constraints caused by the introduced noises, as well as further requirements of low costs
and miniature designs. Such noises are overcome using efficient designs of filtering devices
which are essential components in many satellite, radar and mobile communication
systems. As a result, balanced or differential filtering components have recently received
increasing attention. A wideband microstrip balanced bandpass filter based on modified
stub line approach is presented in here. The proposed idea of extended transmission lines
(TLs) at the input and output (I/O) ports enables for very good stopband rejection and
common-mode suppression.
On the other hand, the recently introduced multilayer liquid crystal polymer (LCP) material
and fabrication technique are exclusively applied in this work for adapting the potential
solutions offered within. Therefore, a comprehensive in-house fabrication process has been
developed and extensively illustrated in this thesis starting from mask preparation covering
the entire procedure up to producing the final piece of output. As a demonstrator of the
potential capability of multilayer LCP technology, a novel miniaturized ultra-wideband
(UWB) balun with self-packaging is introduced in this study. The broadside coupled
stripline structure is adopted in this work to realize UWB performance and TEM mode
which results in excellent amplitude and phase balances.
In turn, a novel compact UWB multilayer balanced bandpass filter using LCP technology is
also presented in this thesis. The design utilizes the transversal signal-interference concept
for realizing an outstanding common-mode suppression while constructed in a stripline
configuration. All of the designs covered in this thesis are initially simulated using CAD
tools to be then validated by measurements of fabricated prototypes
Novel substrate integrated waveguide filters and circuits
The main work in this thesis is to explore novel microwave filters with more compact size and improved performance by taking advantage of new substrate integrated waveguide (SIW) structures, such as the ridge substrate integrated waveguide, half mode substrate integrated waveguide (HMSIW) and SIW with complementary split ring resonators (CSRRs). This thesis therefore presents the following topics:
1. Development of a design strategy to convert from a conventional ridge waveguide configuration with solid walls to the SIW counterpart, and the design of a bandpass filter based on the ridge SIW with the proposed design method.
2. Development of a ridged HMSIW to reduce the physical size of the HMSIW by loading the HMSIW with a ridge, and application of the ridged HMSIW to the design of compact bandpass filters.
3. Development of a broadside-coupled complementary split ring resonator and a capacitively-loaded complementary single split ring resonator to reduce the size of SIW with conventional CSRRs, and application of the proposed modified structures in the design of SIW and HMSIW filters with improved compactness and performance.
4. Investigation of the application of the complementary electric-LC (CELC) resonator in SIW filters with improved stopband performance, and development of a cascaded CELC resonator to further enhance the out-of-band performance