Development Of Microwave Bandpass Filter Using Defected Ground Structure In Comparison With Multilayer And Dielectric Resonator Filters

Bandpass filters perform an important filtering task in a radio transceiver. The narrow stopbands and low gradient in transition bands of conventional parallel-coupled or electromagnetic band gap (EBG) are two (2) of the challenges in designing a bandpass filter. This thesis will introduce three (3) structures of bandpass filter. The first is a new combination of parallel-coupled and defected ground structure (DGS) that operates at a center frequency of 7.8 GHz for mobile satellite application. In essence, this combination structure has resulted to high Q-factor and slow wave which contributes to a high slope and spurious suppression. Cylindrical dielectric resonators were also applied to the circuit in order to increase the return loss in the passband or to enhance the bandwidth of the design. The Zirconate Tin Titanate, ZrSnTiO3 ( r = 37.4, tangent loss = 0.002) dielectric resonator and RO3003 substrate with dielectric constant and tangent loss of 3.0 and 0.0013 respectively were applied in this project. The overall dimension of the circuit was 47.2 mm × 19.16 mm, while the size of the rectangular DGS was 1 mm × 7.36 mm. The second structure is a combination of end-coupled and split ring resonators in a multilayer configuration that operate at 3.47 - 3.79 GHz for Worldwide Interoperability for Microwave Access (WiMAX) application. A modified split ring was introduced to obtain the additional sub-resonators from the magnetic coupled between vertical layers in order to increase the coupling effect from the multilayer structure. The Flame Retardant 4 (FR-4) substrate with dielectric constant, r of 4.6 was used as a core material

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

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

Planar groove gap waveguides

With the increasing demand for wireless services and applications, the integration and coexistence of multi-standard and multi-band operations into a single device has led to intensive research in the design of tunable and reconfigurable planar devices. A planar medium to achieve this integration is the Substrate Integrated Waveguide (SIW). However, due to a lack of DC isolated planes of the structure, bridging wires or concentric etched rings are often used to enable active device biasing. This research presents a novel planar structure referred to as the Planar Groove Gap Waveguide (PGGWG). The new structure has similar modal characteristics to air-filled machined Groove Gap Waveguide (GGWG), but in a low-cost fabrication technology that is readily integrated with surface mount components. The structure provides two DC isolated conducting planes, while still providing a low loss planar transmission medium. Simulation results demonstrate the existence of a TE10 propagating mode within the artificially created bandgap. There is good agreement between de-embedded simulated and measured results over the usable bandwidth of the waveguide (28 to 40 GHz). A passband is measured having an average insertion loss of 1.2 dB and 0.5 dB insertion loss variation implemented on a substrate of relative permittivity r of 3.5, and loss tangent of 0.004. The broadband characterization of the transmission line loss and phase constant for PGGWG at Ka-band shows that PGGWG has comparable attenuation over the band of interest to SIW. The transmission line Q-factor is found to vary from 135 to 140 over the band of interest, which is comparable to SIW in the same medium. PGGWG is also found to have a phase constant of nearly double that of comparable SIW, which is a significant results for system miniaturization. The unloaded Q-factor of a 33.5GHz PGGWG rectangular cavity resonator is measured to be 209. This is found to be comparable to an SIW resonator on the same substrate and frequency band. This work further explores the DC isolation property of the PGGWG by presenting electrically tunable PGGWG resonant cavities. It is found that a simple biasing network can be applied to the cavity using a varactor diode to vary the resonant frequency of the cavity. This is done without bridging wire and concentric etched rings as a direct result of the DC isolation of the PGGWG. A tuning range of 4.5% is achieved in measurement. From the experiments conducted, it is concluded that PGGWG can be used as an alternative planar waveguide media. The PGGWG platform can be used in the design and implementation of RF front-end components at millimeter waves. Its DC isolated conducting planes also provide a simple way of biasing active components in frequency agile applications

Microwave Filters Based on New Design Concepts in Several Technologies with Emphasis on the Printed Ridge Gap Waveguide Technology

Microwave filters have been an interesting research topic for more than half a century. Since any communication system is required to use some microwave filters, considerable effort is being made to optimize the performance and size of these filters. As operating frequency is on the rise, filter design becomes more challenging with the demand for low insertion losses and low cost. As low cost might require the use of printed circuit technology, high performance demands waveguide technology that drives the cost to unacceptable levels. There is a need for a new technology that achieves both requirements of low cost and high performance. The new technology of ridge gap waveguide that was proposed in 2011 shows promising characteristics as a new guiding structure, especially for high-frequency bands. Therefore, it is necessary to design and propose classic or even new filtering devices on this technology. Here, we propose the use of this technology to design practical and efficient microwave filters. The work of this thesis can be divided into three major parts: (1) Developing efficient codes and methods to optimize the computationally expensive structure of ridge gap waveguide or any other large-scale microwave filter device. (2) Characterizing cavity structures on ridge gap waveguide and using them in the design of simple microwave filters. (3) The third part will discuss more advanced and practical filters, especially using printed ridge gap waveguide technology. The ultimate goal of this thesis is to design and propose state of the art designs in the field of microwave filters that can satisfy the requirements of today’s advanced communication systems and to be cost efficient and compete with other rival technologies. We achieved these objectives using efficient optimization, efficient design techniques, and fabrication of the models using advanced technology

Design and analysis of miniaturized substrate integrated waveguide reconfigurable filters for mm-wave applications.

Doctoral Degree. University of KwaZulu-Natal, Durban.Microwave filters are an integral part of communication systems. With the advent of new technologies, microwave devices, such as filters, need to have superior performance in terms of power handling, selectivity, size, insertion loss etc. During the past decade, many applications have been added to the communication networks, resulting in communication systems having to operate at high frequencies in the region of THz to achieve the stringent bandwidth requirements. To achieve the requirements of the modern communication system, tunability and reconfigurability have become fundamental requirements to reduce the footprint of communication devices. However, the communication systems that are more prevalent such as planar circuits have either a large footprint or are not able to handle large amounts of power due to radiation leakage. In this thesis, Substrate Integrated Waveguide (SIW) technology has been employed. The SIW has the same properties as the conventional rectangular waveguide; hence it benefits from the high quality (Q) factor and can handle large powers with small radiation loss. The Half-mode (HMSIW), Quarter-mode (QMSIW), and Eighth-mode (EMSIW) cavity resonators have been designed and used for the miniaturization of the microwave filters. The coupling matrix method was used to implement a filter that uses cross-coupled EMSIW and HMSIW cavity resonators to improve the selectivity of the filter. Balanced circuit techniques have been used to design the circuits that preserve communication systems integrity whereby the Common Mode (CM) signal was suppressed using Deformed Ground Structure (DGS) and a center conductor patch with meandered line. For the designed dual-band filter, the common mode signal was suppressed to -90 dB and - 40 dB for the first and second passband, respectively. The insertion loss observed is 2.8 dB and 1.6 dB for the first and second passband, respectively. For tunability of the filter, a dual-band filter utilizing triangular HMSIW resonators has been designed and reconfigurability is achieved by perturbing the substrate permittivity by dielectric rods. The dielectric rods’ permittivity was changed to achieve tunability in the first instance, and then the rods’ diameter changed in the second instance. For the lowerband, frequency is tunable from 8.1 GHz to 9.15 GHz, while the upper band is tuned from 14.61 GHz to 16.10 GHz. A second order SIW filter with a two layer substrate was then designed to operate in the THz region. For reconfigurability, Graphene was sandwiched between the Silicon Di-Oxide substrate and the top gold plate of the filter, and the chemical potential of Graphene was then varied by applying a dc bias voltage. With a change in dc voltage the chemical potential of Graphene changes accordingly. From the results, a chemical potential change of 0.1 eV to 0.6 eV brings about a frequency change from 1.289 THz to 1.297 THz

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

Design and analysis of wideband passive microwave devices using planar structures

A selected volume of work consisting of 84 published journal papers is presented to demonstrate the contributions made by the author in the last seven years of his work at the University of Queensland in the area of Microwave Engineering. The over-arching theme in the author’s works included in this volume is the engineering of novel passive microwave devices that are key components in the building of any microwave system. The author’s contribution covers innovative designs, design methods and analyses for the following key devices and associated systems: Wideband antennas and associated systems Band-notched and multiband antennas Directional couplers and associated systems Power dividers and associated systems Microwave filters Phase shifters Much of the motivation for the work arose from the desire to contribute to the engineering o

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Design and implementation of band rejected antennas using adaptive surface meshing and genetic algorithms methods. Simulation and measurement of microstrip antennas with the ability of harmonic rejection for wireless and mobile applications including the antenna design optimisation using genetic algorithms.

With the advances in wireless communication systems, antennas with different shapes and design have achieved great demand and are desirable for many uses such as personal communication systems, and other applications involving wireless communication. This has resulted in different shapes and types of antenna design in order to achieve different antenna characteristic. One attractive approach to the design of antennas is to suppress or attenuate harmonic contents due to the non-linear operation of the Radio Frequency (RF) front end. The objectives of this work were to investigate, design and implement antennas for harmonic suppression with the aid of a genetic algorithm (GA). Several microstrip patch antennas were designed to operate at frequencies 1.0, 1.8 and 2.4 GHz respectively. The microstrip patch antenna with stub tuned microstrip lines was also employed at 1.0 and 1.8 GHz to meet the design objectives. A new sensing patch technique is introduced and applied in order to find the accepted power at harmonic frequencies. The evaluation of the measured power accepted at the antenna feed port was done using an electromagnetic (EM) simulator, Ansoft Designer, in terms of current distribution. A two sensors method is presented on one antenna prototype to estimate the accepted power at three frequencies. The computational method is based on an integral equation solver using adaptive surface meshing driven by a genetic algorithm. Several examples are demonstrated, including design of coaxially-fed, air-dielectric patch antennas implanted with shorting and folded walls. The characteristics of the antennas in terms of the impedance responses and far field radiation patterns are discussed. The results in terms of the radiation performance are addressed, and compared to measurements. The presented results of these antennas show a good impedance matching at the fundamental frequency with good suppression achieved at the second and third harmonic frequencies.Home governmen