Miniaturised bandpass filters for wireless communications

The wireless industry has seen exceptional development over the past few decades due to years of sustained military and commercial enterprise. While the electromagnetic spectrum is becoming increasingly congested, there is a growing tendency to strive for higher bandwidths, faster throughputs, greater versatility, compatibility and interoperability in current and emerging wireless technologies. Consequently, an increasingly stringent specification is imposed upon the frequency utilization of wireless devices. New challenges are constantly being discovered in the development and realization of RF and microwave filters, which have not only sustained but fuelled microwave filter research over the many years. These developments have encouraged new solutions and techniques for the realization of compact, low loss, highly selective RF and microwave bandpass filters. The theme of this dissertation is the realization of planar compact performance microwave and RF bandpass filters for wireless communication systems. The work may be broadly categorised into three sections as follows. The first section presents a novel compact planar dual-mode resonator with several interesting and attractive features. Generally, planar microwave dual-mode resonators are known to half the filter footprint. However, it is found that the proposed resonator is capable of achieving further size reductions. In addition the resonator inherently possesses a relatively wide stopband as the lowest spurious harmonic resonance is observed at thrice the fundamental frequency. Properties of this resonator, such as these and more are explored in depth to arrive at an accurate electrical equivalent circuit, which is used as the basis for high order filter design. The application of these resonators in the design of bandpass filters is the subject of the second section. A general filter design procedure based on the equivalent circuit is presented to assist the design of all-pole filters. Alternatively, it is shown that generalised Chebyshev filters with enhanced selectivity may be developed with cross coupled resonator topologies. 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 explores the possibility of employing these resonators in the development of frequency tunable bandpass filters. Preference is given to varactor diodes as the tuning element due to the numerous qualities of this device in contrast to other schemes. In particular, interest is paid to center frequency tuned filters with constant bandwidth. Tunable filters constructed with the dual-mode resonator are shown to have a relatively wide tuning range as well as significantly higher linearity in comparison to similar published works. In line with the previous section, experimental verification is presented to support and supplement the discussions

Miniaturised microstrip dipexers for WiMAX applications

Miniaturised microstrip diplexer and bandpass filters using single ring resonators with good transmission and reflection characteristics on each channel for WiMAX applications have been presented. The size of the proposed diplexer is reduced. The diplexer is easy to manufacture and the results are easily reproducible. The improvement of the performance of diplexer through introduction of additional transmission zeros is under investigation

Compact dual-mode open loop microstrip resonators and filters

A novel compact microstrip dual-mode resonator and filter are proposed. The characteristics of the dual mode resonator are investigated. It is found that the filter response exhibits a desirable stopband response where the first spurious passband naturally occurs at 3f(o). Finally, methods of miniaturizing such resonators and filters are discussed. The proposed structure was able to achieve 60% size reduction

Highly linear microstrip wideband bandpass filter with switchable notched band for wireless applications

This article presents a highly linear reconfigurable bandpass filter embedded with a switchable notch structure to get a band-notched characteristic at a specified frequency.A single PIN diode (BAP65-02) is used for the purpose of switching the notch. An optical switch, comprised of a silicon dice activated using near infrared light is also investigated as an alternative to the PIN diode. While the PIN diode or the optical switch is in the ON state this reconfigurable filter behaves as a bandpass filter with a notch at 2.4 GHz in order to reject WLAN interference while a full band response is obtained in the OFF state. The proposed filter is able to achieve good linearity using PIN diode with IIP3 of 47 dBm and there is no significant loss. A prototype is fabricated, and measured results are compared to simulations. A good agreement has been achieved between simulated and measured results

Compact UWB bandpass filter with reconfigurable notched band

A compact bandpass filter is presented for ultra-wideband (UWB) applications with a reconfigurable notched band to reject unwanted signals from the WiMAX systems. A single pin diode is used for the purpose of switching the notch. An optical switch, comprised of a silicon dice activated using near infrared light is also investigated as an alternative to the pin diode. While the switch is in the ON state this reconfigurable filter behaves as a bandpass filter with a notch at 3.5 GHz and a full band response is obtained in the OFF state. The filter offers excellent performance for the lower-band frequency of a UWB system, ranging from 3.1 to 5.0 GHz and exhibits very low passband insertion loss. Also, transmission zeros are generated at the passband edges to enhance the signal selectivity. A filter sample has been designed and fabricated to provide experimental verification on the proposed filter. A good agreement has been achieved between simulated and measured results with both the pin diode as well as the optical switch. The proposed reconfigurable filter with notched band was able to achieve 40% size reduction as compared to an embedded open-circuited stub

Optically reconfigurable microstrip UWB bandpass filters

This paper presents an optically reconfigurable microstrip ultra-wideband filter. A single optical switch comprised of a silicon wafer is activated using near infra-red light to select between either a bandpass or bandstop response. With the switch in the ON state, the circuit behaves as a bandpass filter while in the OFF state, the circuit behaves as a bandstop filter in the same frequency band. The proposed filter was designed, fabricated and tested. Its performance was evaluated through simulation and measurements

Performance Evaluation of the User Interfaces in Software Programs using Eye & Gaze Tracking

There are many software programs developed by many software developers in these days. The people who are going to interact with them need some time to learn about how to do their tasks using those software programs. Some of these software programs need more than expected time to learn about using them because of poor design of the User Interfaces. User Interfaces are the main windows which are used by the people to interact with the software programs, because of that they must be designed in better way which attracts the attention of the user. Therefore in Human Computer Interaction principles, there some principles for User Interfaces design effective User Interfaces to attract attention of the user to the program. When designing software programs it is necessary to find hotspots on the User Interfaces where the user gives more attention than others. This paper proposes a method of performance evaluation of the User Interfaces of the software programs by testing the software program with actual users of the software program and tracking gaze point of users with the time. By using that information the software developers can find the hotspots of the User Interfaces and include the most important things to the user in those areas. The software developers will be able to develop the User Interfaces of their programs attractive, efficient & effective manner which get more attention of the users of that software program

Attenuation of Murine Collagen‐Induced Arthritis by Targeting CD6

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156498/2/art41288_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156498/1/art41288.pd