537 research outputs found
Reconfigurable RF Front End Components for Multi-Radio Platform Applications
The multi-service requirements of the 3G and 4G communication systems, and their backward compatibility requirements, create challenges for the antenna and RF front-end designs with multi-band and wide-band techniques. These challenges include: multiple filters, which are lossy, bulky, and expensive, are needed in the system; device board size limitation and the associated isolation problems caused by the limited space and crowd circuits; and the insertion loss issues created by the single-pole-multi-through antenna switch.
As will be shown, reconfigurable antennas can perform portions of the filter functions, which can help solve the multiple filters problem. Additionally, reconfigurable RF circuits can decrease the circuit size and output ports, which can help solve board size limitation, and isolation and antenna switch insertion loss issues.
To validate the idea that reconfigurable antennas and reconfigurable RF circuits are a viable option for multi-service communication system, a reconfigurable patch antenna, a reconfigurable monopole antenna, and a reconfigurable power amplifier (PA) have been developed. All designs adapt state-of-the-art techniques.
For the reconfigurable antenna designs, an experiment demonstrating its advantages, such as jamming signal resistance, has been performed. Reconfigurable antennas provide a better out-ofoperating- band noise performance than the multi-band antennas design, decreasing the need for filters in the system. A full investigation of reconfigurable antennas, including the single service reconfigurable antenna, the mixed signal service reconfigurable antenna, and the multi-band reconfigurable antenna, has been completed. The design challenges, which include switches investigation, switches integration, and service grouping techniques, have been discussed.
In the reconfigurable PA portion, a reconfigurable PA structure has first been demonstrated, and includes a reconfigurable output matching network (MN) and a reconfigurable die design. To validate the proposed reconfigurable PA structure, a reconfigurable PA for a 3G cell phone system has been designed with a multi-chip module technique. The reconfigurable PA structure can significantly decrease the real-estate, cost, and complexity of the PA design. Further, by decreasing the number of output ports, the number of poles for the antenna switch will be decreased as well, leading to an insertion loss decrease
RECONFIGURABLE POWER AMPLIFIER WITH TUNABLE INTERSTAGE MATCHING NETWORK USING GaAs MMIC AND SURFACE-MOUNT TECHNOLOGY
As the demand of reconfigurable devices increases, the possibility of
exploiting the interstage matching network in a two-stage amplifier to provide center
frequency tuning capability is explored. While placement of tuning elements at the
input and/or output matching network has some disadvantages, placement of tuning
elements in the interstage absorbs the lossy components characteristics into useful
attributes. The circuit design methodology includes graphical method to determine
the bandpass topology that achieves high Q-contour on the Smith chart thus result in
narrow bandwidth. T-section and π-section topologies are used to match reactive
terminations provided by the first and second amplifier stages. The design
methodology also includes utilization of interstage mismatch loss that decreases as
increasing frequency to compensate for amplifier gain roll-off and equalize the gain
at different tuning states.
In prototype realization, three design configurations are discussed in this
thesis: 1) a discrete design for operation between 0.1 – 0.9 GHz with the total layout
area of 7.5 mm x 12.5 mm, 2) a partial monolithic design (Quasi-MMIC) for
operation between 0.9 – 2.4 GHz that is 25 times smaller layout area compared to the
discrete design, and 3) a conceptual design of integrated monolithic reconfigurable
PA for operation between 0.9 – 2.4 GHz that is 130 times smaller layout area
compared to the discrete design. One variant of the fabricated reconfigurable PA
offers advantage of 4-states center frequency tuning from 1.37 GHz to 1.95 GHz
with gain of 21.5 dB (+ 0.7 dB).
The feasibility of interstage matching network as tuning elements in
reconfigurable power amplifier has been explored. The input and output matching
networks are fixed while the interstage impedances are varied using electronic
switching (discrete SP4T and GaAs FET switches). The discrete design is suited for
the operation at low frequency (fo < 1GHz), while monolithic implementation of the
tunable interstage matching network is required for higher frequency operation due
to size limitation and parasitic effects. The reconfigurable PA using MMIC tuner was
designed at higher frequency to possibly cover GSM, CDMA, Bluetooth, and
WiMAX frequency (0.9 – 2.4 GHz)
Impedance Matching Networks for Wireless Applications
Impedance matching implies maximum power transfer from source to load as well as
minimum signal reflection from the load, in an RF system. This explains the importance
of impedance matching networks and their continuously increasing use in many electronic applications, as for example RF power amplifi ers, source-pull and load-pull power transistor characterization or impedance matching devices such as Antenna Tuning Units.
The focus of this thesis is on the design, fabrication and test of impedance matching
networks. Many diff erent types of practical Impedance Matching Networks are available
which is why detailed investigation and analysis are to be done in order to fi nd the most
suitable topology for the network. RF MicroElectroMechanical Systems (MEMS) switches are used to design a switched-capacitor bank for the proposed impedance matching network. Several RF switches are analyzed and simulated so that their behavior is known when applied to the capacitor bank.
Multiple capacitor banks were designed and fabricated for the purpose of this thesis.
The MEMS-based approach provides better performance and wider capacitance ranges
as compared to the conventional varactors. It allows the design of impedance matching
circuits with di fferent bandwidths and specifi cations, that can be used as part of a dynamically reconfi gurable automatic match control circuit for a wide variety of wireless devices and intelligent RF front ends. For comparison purposes, an impedance matching network using commercial varactors is also simulated and its Smith Chart coverage is presented.
The designed circuits are fabricated and measured. The results indicate satisfactory
performance and good agreement with circuit simulations
Performance enhancement of G-band micromachined printed antennas for MMIC integration
The objective of the work of this thesis is to design, fabricate, and characterise high performance micromachined antennas with fixed and reconfigurable bandwidth. The developed integrated antennas are suitable for MMICs integration at millimetre wave frequencies (G-band) on MMICs technology substrates (i.e GaAs, Si, InP). This work is done through a review of the scientific literature on the subject, and the design, simulation, fabrication and experimental verification, of various suitable designs of antenna.
The novel design of the antennas in this work is based on elevated antenna structures in which the radiator is physically micromachined above the substrate. The antenna design schemes offer a suitable method to integrate an antenna with other MMICs. Further, this method eliminates undesired substrate effects, which degrades the antenna performance drastically. Also in this work we have for the first time realized different micromachined antenna topologies with different novel feeding mechanisms - offering more degrees of freedom for antenna design and enhancing the antenna performance. Experimental and simulation results are provided to demonstrate the effectiveness of the proposed antenna designs and topologies in this work.
A new approach for fabricating printed antennas is introduced in this work to fulfil the fabrication process requirements. It provides a new method for the fabrication of 3-D multilevel structures with variable heights, without etching the substrate. Further, the height of the elevated structures can be specified in the process and can vary by several microns, regardless of the substrate used. This can be used to further enhance the bandwidth and gain of the antenna - avoiding substrate thinning and via holes, and increasing the fabrication yield. Thus, the elevated antenna can meet different application requirements and can be utilized as a substrate independent solution.
In this work we have introduced the concept of reconfigurable antennas at millimetre wave band. Also, we have investigated various aspects associated with lowering the pull-down voltage and overcoming the stiction problem of MEMS switches required for the proposed reconfigurable antennas. This was achieved by developing MEMS technology which can be integrated with MMICs fabrication process. Two novel reconfigurable elevated patch antenna topologies were designed to demonstrate the developed technology and their performances were discussed. The result we obtained from this work demonstrates the feasibility of MEMS reconfigurable printed antennas at G-band frequencies. This will open a new field in MMICs technology and increasing system integration capabilities and functionality.
The devolved technology in this thesis could be utilized in many unique applications including short range high data rate communication systems and high-resolution passive and active millimetre-wave imaging
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
iii
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
Doctor of Philosophy
dissertationMicroelectromechanical systems (MEMS) resonators on Si have the potential to replace the discrete passive components in a power converter. The main intention of this dissertation is to present a ring-shaped aluminum nitride (AlN) piezoelectric microreson
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
Electronically reconfigurable wideband microwave filters
Many systems require multi function capability in the filter aspects of systems; the method currently used is filter banks which take up a lot of board space. It is thought that reconfigurable filters hold the key to replacing filter banks in order to save board space and thus potentially increasing functionality of the systems. The aim of this research is to develop electronically reconfigurable microwave filters for future communication systems. The project investigates some key design issues of reconfigurable filters. Circuits were modelled and full-wave electromagnetic simulations were performed for the investigation. Experimental work was carried out to demonstrate advanced reconfigurable microwave devices. The components used in each concept investigated were pin diodes due to their superior performance in wideband and high frequency applications. Firstly a single coupled line concept was looked at for bandwidth reconfigurability. This concept was then further developed for industrial applications by simply cascading these sections to obtain a high selective filter. A design method was developed for any number of cascades both with and without an impedance transformer; the use of LCP was used to increase flexibility due to its desirable characteristics. The most desirable outcome would be filter to simultaneously control bandwidth and frequency. In order to tackle this issue the coupled line concept was adapted to incorporate frequency tunability, along with a design method being presented. Furthermore, a cascaded highpass/ lowpass filter was also explored for this concept for added flexibility in the design of a filter capable of control of both bandwidth and center frequency
- …