温度共烧陶瓷) technology are briefly introduced, followed by the design of a second-order bandpass filter with added coupling capacitors at input and output ports to provide attenuation poles in both high and low rejection bands. This design, compared to its reference prototype, maintains a similar size while improving the stopband performance. Additionally, a second-order BPF structure is presented that can offer a zero at a specified frequency, resulting in an approximate elliptic response. The combination of SIR resonators and LTCC technology significantly reduces the circuit size compared to microstrip planar circuits.
Throughout the paper, the importance of bandpass filters in wireless communication systems is emphasized due to their role in signal selection and interference suppression. The study begins with a novel design approach for coupled-microstrip bandpass filters, which relies on template transformation techniques. By using a library of available templates and applying suitable transformations, designers can efficiently create customized filter designs tailored to specific wireless communication requirements.
The discussion then shifts to stepped impedance resonators (SIRs), a crucial element in filter design. SIRs are employed to develop a taper-line bandpass filter with improved harmonic suppression capabilities. By incorporating spurlines within the taper, two zeros are introduced in the stopband without significantly increasing the overall dimensions of the filter. Simulation results validate the effectiveness of this approach in enhancing the filter's performance.
The use of low-temperature co-fired ceramic (LTCC) technology is explored as it allows for multi-layer circuit integration and compact design. A second-order bandpass filter is designed using LTCC, demonstrating how adding coupling capacitors at the input and output can create attenuation poles, thereby boosting the filter's rejection characteristics. This design maintains a comparable footprint to its predecessor but improves upon its stopband performance.
Furthermore, another second-order BPF structure is presented that introduces a zero at a predetermined frequency, mimicking an elliptic response. This structure enables more precise control over the filter's frequency response. The combination of SIRs and LTCC technology not only reduces the physical size of the circuit but also simplifies the design process through the utilization of multiple EDA (Electronic Design Automation) software tools, thereby accelerating the design cycle.
Lastly, a practical example is provided for a bandpass filter designed for wireless local area network (WLAN) applications. The paper also proposes an analysis method to detect subtle changes in the substrate's dielectric constant by leveraging the high-stopband zeros offered by SIR resonators. This is particularly relevant for LTCC manufacturing processes where precise control over material properties is critical.
In conclusion, this thesis delves into various aspects of bandpass filter design for wireless communication systems, presenting innovative techniques and structures such as template transformation, SIR resonators, and spurline integration. It also explores the advantages of LTCC technology in achieving compact, high-performance filters. These contributions demonstrate the ongoing advancements in filter design, highlighting the potential for future developments in wireless communication systems.
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