Harmonic Suppressed Reconfigurable Dual-band, Multi-mode Ultra-wideband, and Compact High Selective Microstrip Bandpass Filters

As an indispensable component, microwave bandpass filters play a very important role in many modern wireless systems. They are used to carry out the selection of only the wanted frequencies from RF signals with various spurious frequencies. The reconfigurable filter with multi-band has attracted much attention for both research and industry because of the increasing importance in making RF components that have multi-function with compact size. Wide or Ultra-wideband (UWB) bandpass filters are becoming more and more in demand in many wireless applications due to the high data transmission rate. This dissertation focuses on the study of microwave filters with many applications in various wireless systems. Firstly, bandpass filters using stepped impedance stubs are presented. The resonant frequencies and transmission zeros are analyzed, and harmonic suppression by novel S-shaped coupled feed lines is presented. A resonator with a dual-band characteristic is introduced, and it is analytically shown that each passband can be independently controlled by the parameters of the resonator. PIN diodes are used to introduce an electrically controlled dual-band bandpass filter. Secondly, symmetric stepped impedance resonators with asymmetric stepped impedance stubs are also presented to develop Ultra-wide band (UWB) bandpass filters with and without a notched band. The resonant frequencies and transmission zeros of the resonator are effectively located to achieve a very wide passband and a high attenuation rate in rejection bands. The interdigital coupled feed lines with rectangular slots are designed for a better passband characteristic. A notched characteristic is introduced by using modified feed lines to avoid the interferences with other existing signals. UWB bandpass filter performances in time-domain and frequency-domain are analyzed and discussed. Thirdly, UWB bandpass filters with a different configuration are developed. Similarly, the analyzed resonant frequencies are used to achieve a passband for UWB applications. A different technique is used to introduce a very narrow notched band within the passband. Time-domain analysis is made to verify the frequency-domain performance. Lastly, a very high selective wideband bandpass filter is presented using an inverted T-shaped resonator. The characteristic of the resonator is analyzed to design a bandpass filter with specified bandwidth. The short stubs are introduced to achieve a very high attenuation rate at both sides of the passband and a wide stopband characteristic. In summary, various microwave filters to meet the requirements of specific applications are studied and designed. Analysis and design methodology of the proposed microwave filters in this dissertation can be applied in many applications in wireless systems

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

Analysis and Design of a Highly Compact Ellipse-Shaped Ultra-Wideband Bandpass Filter (Uwb-Bpf) with a Notched Band

Since the Federal Communications Commission’s endorsement of the frequency band of 3.1 – 10.6 GHz in 2002 to be unlicensed for wireless communication applications, various ultra-wideband bandpass filters (UWB-BPFs) have been proposed and designed. Different UWB-BPF configurations were presented in the past years to meet the very strict UWB-BPF specifications in terms of ultra-band requirement, low return loss, high rejection in notched bands. However, most of the previous works are limited by large dimension size, complex geometry, and high production cost. The major objective of this work is to design a highly compact, simple geometry, and low-cost UWB-BPF, which passes signals in nearly all frequencies in the passband with minimum loss but rejects unwanted WLAN interference signals in the frequency neighborhood of 5.8 GHz. First, an ellipse-shaped UWB-BPF was designed by using a simplified composite right/left handed (SCRLH) resonator to achieve a 3dB bandwidth ranging from 2.94 GHz to 12.83 GHz. Then, two open, curved stepped-impedance stubs were integrated into the UWB-BPF to achieve a notched band in the range of 5.8 GHz, such that the frequency response in the frequency band was sharply notched up to about 35dB attenuation. The finalized UWB-BPF, is simply built up with a commonly used PCB with FR4 substrate and has a dimension of 14mm × 6.2mm. The extracted current density images in the passbands, stop bands, and notch band clearly demonstrate the mechanism of the signal response characteristics of the proposed UWB-BPF

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

Slot-Line UWB Bandpass Filters and Band-Notched UWB Filters

Slot-line ultra-wideband (UWB) bandpass filters and band-notched UWB filters are presented for UWB systems. Three types of slot-line multimode resonators are proposed and studied. Microstrip feed lines are used to realize the desired strong external coupling in a simple manner. By properly allocating the resonant modes of resonator and external coupling, UWB bandpass filters have been realized. Next, microstrip resonators, i.e., open-loop resonator, stub-loaded dual-mode resonator, and triangular dual-mode ring resonator, are loaded to the slot-line; notched bands are realized in the UWB passbands. The design methodology has been verified by the measured results

Enhanced Design Of Electronically Reconfigurable Integrated Microwave Filter And Antenna For Wireless Communication Systems

The reconfigurable integrated filter and antenna is one of the major interest for researchers due to the potential significant advantages compare to the typical standard integrated structure. The growth in reconfigurable integrating technology is not limited to a single tunable parameter such as operating frequency, bandwidth and attenuation but it can be combination parameters depending on the applications. There are many techniques have been developed to achieve adaptable reconfigurable integrated filter and antenna but majorities of the reconfigurable designs are focused on a single element either on an antenna or the filter. Thus, it limits the tunable range and flexibility response of the reconfigurable design will be a challenging task. On the other hand, developing a Ultra-Wideband (UWB) antenna is one of the crucial components for UWB communications systems and has been widely studied for many years. Moreover, the reconfigurable UWB designs can be developed the desired filtering antenna which can reject unwanted signal interferences. However, most of these techniques produce excessive band rejection, which leads to reject desired frequencies, thus producing a narrowband notch characteristics is a challenging issue. Therefore, the aim of this research is to design novel structure of reconfigurable integrated technique of planar structure which promises a new potential functionality of the microwave devices. Two designs approach were introduced which is reconfigurable SIW filter and antenna and reconfigurable dual band-notched UWB antenna using FR-4 substrate and Roger Duroid RO4350B with dielectric constant of 4.6 and 3.48 respectively. To realize the concept, reconfigurable SIW filter and reconfigurable patch antenna have been combined using the multilayer technique into a single structure while UWB antenna and reconfigurable notch filter were combined on the same planar. To validate the design technique, the equivalent circuit model of the tunable varactor diode network is presented to study the tunability mechanism. Two commercial software programs that have been used in the design and development of two main designs namely Advanced Design System (ADS) software and CST Studio Suite software. All designs were simulated, manufactured and measured. Reconfigurable integrated SIW filter and antenna provide a good attenuation tuning range about 15.5 dB with improvement up to 55 % and only shifts 1 MHz from the origin centre frequency while reconfigurable UWB antenna with band-notched provide a good range up to 210 MHz. This design has smaller compact size of 37.6 mm x 28.0 mm with bandwidth for peak notch of 224.76 MHz and 89.90 MHz for both notches. The experimental results show a good agreement with the simulated results. The benefits of the reconfigurable integrated design are potentially miniaturizing overall structure, good tuning capability, easy to fabricate and cost effective. The outcomes of the proposed reconfigurable integrated design may facilitate improvements in an integrated technique with a good tuning capability for wireless communication systems

Ultra-wideband bandpass filter with notch band based on quadratic Koch Island structure

An ultra-wideband bandpass filter with a notch band centered at 7.2 GHz is proposed to remove the interference caused by satellite communication signal coexciting within the ultra wide band. The filter comprises of two seperated quadratic koch island structures connected to the main transmission line to generate the notch band at the desired frequency. The designed ultra wide bandpass filter passes frequencies from 3.09 GHz to 10.61 GHz with a notch band from 7.12 to 7.46 GHz centered at 7.2 GHz and with a rejection level of 21.3 dB.The resonant frequency and bandwidth of the notch can be varied by the variation in the physical parameter of the filter. The proposed filter is fabricated, tested and compared with simulated results

Passive Components for Ultra-Wide Band (UWB) Applications

UWB technology brings the convenience and mobility of wireless communications to very high-speed interconnects in the home and office due to the precision capabilities combined with the low power. This makes it ideal for certain radio frequency sensitive environments such as hospitals and healthcare as well as radars. UWB intrusion-detection radar is used for detecting through the wall and also used for security with fuse avoidance radar, precision locating and tracking (using distance measurements between radios), and precision time-of-arrival-based localization approaches. The FCC issued a ruling in 2002 that allowed intentional UWB emissions in the frequency range between 3.1 and 10.6 GHz, subject to certain restrictions for the emission power spectrum. Other definitions for ultra-wideband range of frequency are also used such as any device that has 500 MHz bandwidth or fractional bandwidth greater than 25% is considered an UWB enable high data rate to be transferred with a very low power that does not exceed −41.3 dBm

Implementation and Investigation of a Compact Circular Wide Slot UWB Antenna with Dual Notched Band Characteristics using Stepped Impedance Resonators

A coplanar waveguide (CPW) fed ultra-wideband (UWB) antenna with dual notched band characteristics is presented in this paper. The circular wide slot and circular radiation patch are utilized to broaden the impedance bandwidth of the UWB antenna. The dual notched band functions are achieved by employing two stepped impedance resonators (SIRs) which etched on the circular radiation patch and CPW excitation line, respectively. The two notched bands can be controlled by adjusting the dimensions of the two stepped impedance resonators which give tunable notched band functions. The proposed dual notched band UWB antenna has been designed in details and optimized by means of HFSS. Experimental and numerical results show that the proposed antenna with compact size of 32 × 24 mm2, has an impedance bandwidth range from 2.8 GHz to 13.5 Hz for voltage standing-wave ratio (VSWR) less than 2, except the notch bands 5.0 GHz - 6.2 GHz for HIPERLAN/2 and IEEE 802.11a (5.1 GHz - 5.9 GHz) and 8.0 GHz - 9.3 GHz for satellite and military applications