Research Of Passive Components Based On LTCC Technology

With the development of wireless communication system, low temperature co-firedceramic (LTCC) technology has been widely used in many microwave/millimeter-wavecircuits with small size, light weight, good performance and high integration by itscharacteristics of low cost, low dielectric loss, multilayer layout, superior electric andthermal conductivity, high frequency and high Q value. Based on the basic theory ofplanar cross-coupled filter and microstrip antenna, this paper presents a series design ofmultilayer filter and antenna with LTCC3D structure. The filters have the features ofcompact size, high suppression, wide-band/dual-band, tunable transmission zeros andresonant frequency. And the antennas have the characteristics of dual-frequency, dualcircularly polarization, compact radiation area and volume. Thus there has anexpansively application prospects.First of all, the paper illustrates the elementary principles of cross coupled filterand reduces the matrix optimization problem to minimum value solution of objectivefunction. Genetic-Solvopt mixed algorithm, which is suitable for any topologicalstructure, is presented and its correctness is verified in filter design based on MATLABsoftware. A series of novel topological structures with source-load coupling is proposed,the transmission zeros and response curves are settled and analyzed in detail. Cascadefilters with N blocks modules are introduced, the transmission zeros of which arecontrolled by each module separately. The modules can be cascaded to form a highorder filter according to different cascade ways, while their transmission zeros are fixed.Thus cascade filter with N blocks modules has the properties of high stop-band rejection,good selectivity and reflection response. Meanwhile, the structure analysis andrealization could be simplified based on each single module, also the effect ofsimulation and fabrication error is reduced.Secondly, the paper presents some resonator filters with novel structure based onLTCC technology. Multilayer cross coupled SIR filter is designed with horizontal andvertical couplings, the size is more compact and the coupling element is easier to control. Meanwhile the introduction of source-load coupling and00feed structureguarantees the high suppression of stop band. Besides, a series of multilayeredwideband bandpass and bandstop filter is designed using semilumped resonators andmultilayer capacitors. The transmission zeros are controlled by each resonator separately,and the bandwidth as well as rejection level are free to adjust. Additionally, dual-bandbandpass filter with this semilumped resonator structure is also demonstrated.Source-load coupling in vertical direction is utilized to add transmission zeros andimprove the selectivity. The resonant frequencies and transmission zeros are flexiblytuned by elements of each resonator respectively.Thirdly, some LTCC microstrip antennas with miniaturized structure are discussed.Perturbed dual-band circularly polarized antenna with wide radiation bandwidth isrealized by tuning the area of radiation and perturbation pattern. Some inserted silts areutilized to meander the excited fundamental-mode patch surface current path, whicheffectively lowers the resonant frequency of the patch, thus the compactness of theproposed CP design is achieved. Besides, a novel compact WLAN antenna usingmeander striplines in three LTCC layers is completed, the volume of which is only3.2×1.6×2mm3. The resonant frequencies can be easily tuned by adjusting the innercoupling between different patterns and the length of the striplines (dipoles). Besides,the connection between different radiation layers is realized by end-coating, thus no viahole was used in this structure, which guarantees the easy fabrication and highproduction. Moreover, it is found that inhomogeneous spaced meander line createswider radiation bandwidth than homogeneous spaced one does.