Design Of Multilayer Ltcc Microwave Bandpass Filter And Performance Research

Along with the high development of wireless communication in business, The miniaturization of electron equipment becomes a very important problem. The filter, on the basis of low temperature cofired ceramic (LTCC), has the advantages of smaller size, lower cost and ever-greater functionality. So it plays an important role in the communication industry.This paper presents the theory of microwave filter briefly, and designs a type of multilayer LTCC bandpass filter by circuit simulation and filed simulation in order to satisfy the requirement of miniaturization and high-performance. The main works are as follows:Firstly, the paper systematically describes the theories that form the foundation for design of microwave filter. It introduces the basic structure and characteristic of the uniformity transmission-line, the Uniformity Impedance Resonator (UIR) and the Step Impedance Resonator (SIR), and analyses how to lead transmission-zero into the stop-band.Secondly, according to the special requirement, it obtains the lump-circuit prototype of band-pass filter and its parameter values, and on the basis of this it calculates the dimension of filter model with the UIR. It is shown in the simulation that the insertion loss of filter with the UIR is less than 1.64dB, but the suppression of stop-band can not satisfy the requirement of35dB.Thirdly, in order to suppress the stop-band signal, it uses the SIR and cross-coupling tolead two transmission-zeros into the low stop-band, and presents coupling-factor K and external Q-factor to obtain the resonators' spacing and tap's location that they are 0.35mm and 0.49mm severally.Finally, considering the practical condition, the model of filter with SIR is put on the PCB to optimize, and is analysed the effect of resonator's length on the center frequency, tap's location on insertion loss and ripple in BW, resonators' spacing on bandwidth and insertion loss and PCB's parasitic through-hole inductance on the high-frequency's transmission zero, then the paper summarize the law of change. Finally, a LTCC filter is designed successfully that issmall size 2.5mm×2.0mm×0.9mm, with the performance of center frequency f₀ =2.45GHz,bandwidth =100MHz, insertion loss < 1.8dB, VSWR in BW < 1.2dB, and the attenuation of stop-band also accord with the requirement.