The Design Of The High-performance Miniaturized Microstrip Low-pass Filter

With the rapid development and wide application of the wireless communication technology, the design of filter with high performance, compact size, low cost, and design flexibility has drawn more and more attention. Lowpass filter takes a key role in the wireless communication system, and its performance determines the quality of communication system. Miniaturization technologies of resonators were studied in this thesis. The resonance properties of triangular resonator, radial resonator and trapezoid resonator were theoretically analyzed respectively. According to the detailed theory analyzing, general ideas of resonator miniaturization were proposed. With these ideas, several schemes for microstrip lowpass filter design with high performance and compact size are presented. Based on these schemes, three microstrip lowpass filters with high performance and compact size have been designed.Firstly, some research on the performance of stepped-impedance triangular patch resonators and radial patch resonators are done in this dissertation. To achieve compact size and ultra-wide band rejection, both triangular patch resonators and radial patch resonators are introduced in the filter. To further reduce the circuit size of the filter, the meander transmission lines are also adopted in the design. Simulation and measurement indicate that the simulated and measured results are in good agreement. A demonstration filter with3dB cutoff frequency at1GHz has been designed, fabricated and measured. The proposed filter exhibits a small size of0.111λg×0.091λg, where λg is the guided wavelength at1GHz. Furthermore, results indicate that the proposed filter is able to suppress the16th harmonic response referred to a suppression degree of15dB.Secondly, some research on the performance of stepped-impedance triangular patch resonators and trapezoid patch resonators are done in this dissertation. To achieve compact size and ultra-wide band rejection, both triangular patch resonators and trapezoid patch resonators are introduced in the filter. To further reduce the circuit size of the filter, the meander transmission line is also adopted in the design. Simulation and measurement indicate that the simulated and measured results are in good agreement. A demonstration filter with3dB cutoff frequency at0.85GHz has been designed, fabricated and measured. The proposed filter exhibits a small size of0.089λg×0.081λg, where λg is the guided wavelength at0.85GHz. Furthermore, results indicate that the proposed filter is able to suppress the14th harmonic response referred to a suppression degree of15dB. Finally, to achieve compact size and ultra-wide band rejection, five trapezoid patch resonators are introduced in the filter. Simulation and measurement indicate that the simulated and measured results are in good agreement. A demonstration filter with3dB cutoff frequency at0.8GHz has been designed, fabricated and measured. The proposed filter exhibits a small size of0.057λg×0.077λg, where λg is the guided wavelength at0.8GHz. Furthermore, results indicate that the proposed filter is able to suppress the17th harmonic response referred to a suppression degree of15dB.