Design And Implementation Of Multilayer Wideband Bandpass Filter

RF/microwave devices are the important part of modern mobile communications, and passivefilter plays a key role in the communication system. With the rapid development of wirelesscommunication system, people have more and more interest to reach the requirement of widebandminiaturized bandpass filte（rBPF）. In this thesis, based on the above points of study, wideband andminiaturization filters were studied as follows:(1) A new kind of multilayer broadband bandpass filter based on LTCC technology is proposed.The equivalent circuit of the filter is transformed from a five-resonator chebyshev circuit model,and two high frequency transmission zeros at high stopband are introduced. The results show thatthe center frequency of the filter is1.5GHz with more than40%relative bandwidth, and therejections at the low stopband0-0.8GHz and high stopband2.5-6GHz are more than30dB. Thesize of the filter is8mm×4mm×1.6mm.(2) A miniature wideband bandpass filter based on the circular patch resonator is designed inthis thesis. The circular resonator is composed of a high impedance microstrip line and a circularpatch microstrip line. A transmission zero is achived by introducing the coupling between the inputand output port. Calculated and optimized by the electromagnetic simulation software, the circuitsize and structure is determined finally. The results show that a wideband filter with a frequencyrange between3.1to6.5GHz has simple structure, small size, and the simulation results have thegood agreement with the measurement results.(3) A multilayer wideband bandpass filter based on microwave PCB process is designed andimplemented, and the filter equivalent circuit is cascaded of a highpass filter and two lowpass filters.The circuit size and structure are calculated and optimized by electromagnetic simulation software.Measured results show that the center frequency of the proposed filter is1.9GHz with more than80%relative bandwidth, greater than15dB suppression outside the band. The size of the filter is0.25l g×0.10l g(for frequency in the waveguide wavelength of1.9GHz).