Miniaturized Filter Design Based On LTCC

With the rapid development of wireless communication, miniaturized terminalequipments with light weight are required. Therefore, the circuits need to be designed withhigh integration. LTCC（Low Temperature Co-fire Ceramic）provides a good way to designcompact and high-integrated circuit. Because of the multilayer structure, it is easy to wiringthe conductor. Moreover, LTCC substrate has high permittivity while the loss is low. LTCChas good performance at high frequency. It is suitable for microwave or even millimeter wavecircuit design.This paper present some miniaturized filters design based on LTCC. The main work canbe summarized as follows in three parts:Filter with wide stopband is designed using discriminating coupling. The proposedcircuit consists of two coupled λg/4SIR (Stepped Impedance Resonator). A special couplingregion is selected to realize a novel discriminating coupling scheme for generating atransmission zero (TZ) at the third harmonic frequency. The mechanism is analyzed and thedesign guideline is described. The source-load coupling is introduced to generate two TZsnear the passband and one in the stopband. Thus, wide stopband can be obtained without extracircuits. Due to the LTCC multi-layer structures, the filter size is2.63×2.61×0.5mm3. Thesimulated and measured results of the demonstrated LTCC bandpass filter are presented tovalidate the proposed design. This work has been published in IEEE Transactions onComponents, Packaging and Manufacturing Technology.A new method of using electric and magnetic coupling cancellation to extend thestopband of bandpass filters is presented. The mechanism is theoretically analysed based onthe lumped-element equivalent circuit. Due to the cancellation of electric and magneticcoupling between two resonators, three transmission zeros (TZs) can be generated andcontrolled by manipulating the coupling strength. Using the proposed method together withsource-load coupling, a LTCC bandpass filter is designed with four TZs, resulting in high skirtselectivity and harmonic suppression. The filter size is2.48×2.02×0.6mm3. The theoretical,simulated and measured results of the LTCC bandpass filter are presented to validate theproposed design. This work has been accepted for publication in IEEE Transactions onComponents, Packaging and Manufacturing Technology.Stepped impedance resonators (SIRs) are used to achieved dual-band bandpass filters,the designed filters own compact size and high selectivity. The resonant characteristics of the SIRs are studied by analyzing the impedance. Then, two filters are implemented in LTCC.One is designed using microstrip lines and the other is designed using strip-lines. The circuitsize is2.8×2.5×0.8mm3and2.8×2.8×2.0mm3, respectively. This work has been publishedin IEEE,2013Cross Strait Quad-Regional Radio Science and Wireless Technology.