DESIGN OF COMPACT BAND PASS FILTER FOR UWB APPLICATION WITH MULTIPLE NOTCHES

Abstract

Radio frequency (RF) filters are essential components of the present wireless communication systems as it enables and enhances their functionality. RF filter’s primary objective is to govern and control electromagnetic signals ensuring that they operate within a particular frequency spectrum. However, the upper stopband of conventional Ultra-Wideband (UWB) filters was limited, and they were sensitive to interference from other wireless services. To satisfy the need of integrated services and overcome the shortcomings of its forerunner, UWB filters have greatly improved. They are compact and have several notches which are strategically positioned to improve transmission efficiency. With the help of this development, UWB filters may be seamlessly integrated into several devices and applications, making more efficient use of limited space and spectrum allocations. UWB filters play an important role in minimizing interference and maintaining the smooth functioning of wireless services by targeting and suppressing undesirable frequencies. In today's technology-driven society, their advanced designs let numerous systems exist harmoniously, promoting an integrated and efficient wireless ecosystem. Revolutionary developments, such as high-speed data transfer, Internet of Things (IoT) applications, and the establishment of smart city infrastructure, have been made attainable by advancements in UWB filter technology. The capability of these filters to precisely filter specific radio frequencies provides reliable data transmission, allowing for smooth communication across a wide range of scenarios and environments. The design of UWB filters poses a distinctive challenge of strategically incorporating notches at specific frequencies to effectively mitigate interferences. the design must achieve a wide bandwidth while maintaining acceptable performance characteristics across the entire frequency spectrum. This thesis explains the design and analysis of band pass filters for UWB applications. In the present endeavour, six filters for UWB applications are fabricated and measured, namely: MMR-based filter, flexible and transparent filter using silver nanowire, stepped impedance resonator (SIR) based filter, broadside coupled filter based on microstrip to CPW transition filter, multiple notches filter based on CSRR, and Hybrid SIR and Modified CSRR based multiple notches filter. Extensive simulations are used to analyse and then experimentally validate the aforementioned structural designs. These all suggested filters are suitable for UWB applications. viii The first chapter offers a concise and comprehensive introduction to UWB (Ultra-Wideband) technology, providing a foundational understanding of its concepts and applications. It explores the anticipated spectrums that UWB technology is expected to utilize, highlighting its potential to exploit a broad range of frequencies for diverse wireless communication purposes. The second chapter explores the complexity of UWB filter design and provides significant insights into the underlying concepts and modelling methodologies. The next section of the chapter explores numerous techniques used to enhance selectivity, passband flatness, stopband extension, and other frequency characteristics of UWB filters. In addition, the chapter investigates the implementation of single and multiple-notch functions within the filters, intending to eliminate any potential in-band interference. The in-depth examination offers a thorough grasp of the complicated design issues and modern techniques utilized to enhance the functionality of UWB filters, ensuring the effective suppression of undesirable signals while maintaining the integrity and quality of the desired UWB signals. The third chapter describes the construction of planar structures that generate a passband utilising multimode resonators (MMRs) and interdigital capacitors (IDCs). The upper transmission zero (TZ) is regulated by the arm dimension of the IDCs, while insertion loss is reduced by tight coupling among the IDCs' arms. By integrating inverted L-type resonators in the design, the lower TZ is tuned. The result makes it possible to manage the TZ. In the fourth chapter, silver nanowires are utilized for creating the circuit on a transparent and flexible PET substrate. The TZ is controlled by the length of the three pairs of arms that collectively make up the passband. The TZ of this structure is determined by the arm length of the IDCs, and it demonstrates an extended stop band of up to 50 GHz. In the fifth chapter, a dual-notched band UWB-BPF was built using broadside linked techniques. This structure incorporates complementary split ring resonators (CSRRs) in the bottom plane to introduce two notches in the passband. These notches are positioned at 5.4 GHz and 8.2 GHz, and they can be independently controlled. By changing the dimension of the CSRRs, both notches can be positioned to desired frequencies. The incorporation of CSRRs in the design allows for precise control over the notches, enabling selective suppression of unwanted frequencies. This dual-notched band UWB filter offers improved interference rejection capabilities and enhances the overall performance of UWB systems. The design ix methodology here involves optimizing the dimensions and placement of the CSRRs to achieve the desired notch frequencies. In the sixth chapter, the planar structure has been designed for the application of triple-notched bands. In this the structure utilize a broadside coupled technique, employing a basic architecture of a BPF with microstrip-to- CPW transitions arranged on either side of the dielectric. This UWB-BPF exhibited favourable frequency characteristics, featuring two TZs located at the edges of the passband. To eliminate in-band interferences, DGS in the form of CSRRs and complementary folded split ring resonators (CFSRR) were incorporated, resulting in the placement of three TZs within the passband. The triple notches were centered at frequencies of 5.6, 6.42, and 8.03 GHz, attenuating over 19 dB. The measured 3-dB BW of the suggested filter spanned from 3.25 to 10.73 GHz and stopband attenuation was achieved up to 17 GHz. The basic geometry of the BPF was built in the seventh chapter employing microstrip lines on the upper layer linked to an altered CPW on the bottom layer. Because of the presence of two TZs at the lower and upper edges of the passband, this design with a broadside alignment produced a highly desirable Ultra-Wideband (UWB) response. This concept was improved further by incorporating numerous circular resonator CRs and a CFSRR into the basic architecture. These additional components were added to the ground plane to efficiently mitigate interference from in-band RF sources. By effectively arranging the CRs and CFSRR, the filter was able to establish TZs at frequencies of 5.2, 6.5, and 8 GHz, effectively filtering undesirable signals from WLAN, C band, and X band, respectively. In the eighth chapter, a compact quad-band notched filter was developed for UWB applications. This suggested filter was constructed using a single-layered Roger 6010 dielectric with a height of 0.635 mm and a dielectric constant of 10.8. In this design, Quad notches were introduced within the passband at frequencies of 3.6 GHz, 5.4 GHz, 7.5 GHz, and 8.7 GHz. These notches effectively eliminate interference caused by WiMAX, WLAN, C band, and the super-X band for satellite TV networks (ranging from 7.2 GHz to 8.4 GHz) within the UWB passband. The quad notches were implemented using SRR and CSRR. The suggested UWB BPF was developed and simulated using IE3D EM simulation software. Chapter 9 concludes this thesis by, summarizing the findings and contributions presented throughout the work. It also offers valuable insights and suggestions for potential future x enhancements and extensions of the research, particularly concerning diverse UWB filter design applications.