الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The increasing development of wireless applications turns out to new requirements for
transceiver architectures that have to feature excellent microwave performances (linearity,
spurious rejection, noise figure and bandwidth) and enhanced integration density that are
achieved through the miniaturization of the modules as well as the introduction of multi
standard functionalities. All these requirements translate to the need of filter circuits as
miniaturized as possible and featuring the highest performances in term of insertion loss and
rejection. Microwave filters possessing various forms are essential components in radar,
satellite and mobile communication systems. Increased demands for low-loss, miniature filters
that can be mass produced at low cost have provided a significant challenge reinforcing the
need for improving or even replacing the conventional microwave filters.
This thesis introduces the investigation and development of design methodologies for the
creation of multi-functional bandpass filters and lowpass filters at microwave frequencies.
These filters are capable of tuning to different frequency bands as well as varying their
fractional bandwidth.
The work presented here relates to the evolving multifunction philosophy of RF systems.
This thesis presents a comprehensive study of RF reconfigurable planar microwave filters,
which generate reliable and scalable filter topologies with tunable properties. The study includes
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the analysis of single, dual -mode filters together with an investigation of the coupling behavior
of synchronously and asynchronously tuned resonators. This study identified the main
properties responsible for frequency and bandwidth control in a filter, and consequently
systematically created innovative design techniques.
The research also proposes novel planar microstrip filters employing DGS structures in the form
of slots etched on the ground plane. Such filters are not only miniaturized, but also have
improved RF performance in both the passband and the stopband. This proposed concept is
further extended to implement low-loss tunable bandpass filters, by integrating switching
elements directly into the slots. Transmission line circuit models are developed to design the
proposed microstrip filters and switchable filters. To verify the concept and the validity of the
developed circuit models, theoretical and experimental results are presented and carefully
compared. The main goal of this effort is the creation of planar reconfigurable filters with
arbitrary assigned transmission zeros. These advanced realizations require meeting complex
design specifications of advanced systems in both commercial and military applications.
Over the work introduced, tremendous progress has been made to reduce the size, and enhance
the in-band and out-of-band performance of microstrip filters. The experimental measurement
results confirm the validity of the theoretical designs of the new filters, which makes this
concept very attractive for further applications in both wireless and satellite communication.
This work has produced several first time demonstrations of reconfigurable filter techniques,
dual-mode, multi-band filters, and miniaturized low pass filter with advanced responses, and
several design of filters to obtain the recent technologies with lumped element capacitors, and
RF PIN diodes switches. Filters with tunable center frequency, dual-mode resonators were
designed with reconfigurable passband width, and center frequency. Moreover, reconfigurable
with RF PIN diodes techniques were used as powerful tools for the creation of filters capable of
manipulating the location of their transmission zeros. Dual-mode filters that are tunable in
frequency provide advantages in the reduction of size and number of tuning elements when
compared to single-mode tunable filters today.
A triple-band bandpass filter was designed using spiral lines approach for the first time. The
filter topology consists of a meander stub resonant pattern located inside a spiral square loop
resonator. A filter prototype was fabricated and measured producing a fully canonical filtering
function with three resonant frequencies and three transmission zeros. The final prototype
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approaches the performance of good filters in terms of loss, while keeping a compact size
profile comparable to standard planar filters. The final part of this work is that new high
performance filter is miniaturized, reconfigurable and can be easily packaged in microwave
components and antenna arrays. A comparison has been made using a single defected ground
structure and then using two defects. The simulation firmly establishes the fact that when a
single defect is introduced, a reduction of 20 dB in the power level is obtained at 3.5 GHz, the
spurious frequency is eliminated in the stop band up to 14 GHz.
Finally, for future work, the implementation of these structures on silicon substrates using
MEMS switches and ferroelectric materials is proposed to achieve overall better performance
and easy tuning.