Research And Design Of Band - Pass Filter Based On LTCC Process

Based on the LTCC technology, this paper briefly introduces the advantage and current situation of it. Then these theses introduces the basic design theory of coupling resonance band-pass filter, brings in the concept of resonator, and specifically makes a summary of traditional formula of characteristic impedance, especially the influence of the central frequency to the calculated result of characteristic impedance. In the process of filter’s input and output design, the tap structures of microstrip line impedance’s calculated result have an effect on the property of circuit. By bringing in formula of characteristic impedance’s influence on frequency factors makes the characteristic impedance much more accurate and reduce the error of it, when to design the tap structure size. What’s more, the designing of the tap structure size will be more convenient and faster, to a degree which saves time. Regarding that most characteristic impedance calculation software is only existed in the computer, the paper summaries a new formula. Then, the paper uses JAVA language to implement the programming of Eclipse software and then generates the apk which can install on the Android client.Then the thesis provides the designing process of coupling resonance filter. Basing on the LTCC technology, the author works out two types of SIR interdigital bandpass filters. The central frequency of those two types are SIR six order interdigital bandpass filter in 3.25GHz and the other one is the SIR four order bandpass filter in 1561MHz. Those two are both made of quarter-wave’s SIR, which minimizes the design of the devices. Meanwhile, to enhance characteristics of restraint outside the band, improve passband rectangle degree, the author adds capacitance feedback on the periphery between cavities, brings in two transmission zeros which improve the filter’s transmission performance. The first one satisfies the requirement of less than 2.65dB between 3100MHZ and 3400MHZ, and in-band jitter is less than 0.57dB, and its standing wave is less than 1.3dB. Its out-of-band rejection is more than 38dB between 1 to 2.66GHz, the out-of-band rejection is more than 30dB between 2.7 to 2.86GHz, the out-of-band rejection is more than 36dB between 3.64 to 3.84GHz and the out-of-band rejection is more than 36dB between 4.08 to 4.38GHz. At last the size is 6.8mm×4.2mm×1.5mm. For the second one, the bandwidth is 250MHz; the insertion loss is 2.5dB; and the in-band jitter is less than 2.0dB. Out-of-band rejection is more than 50dB below 1.0GHz; out-of-band rejection is more than 30dB between 1.9GHz and 3.0GHz. At last the size is 4.5mmx3.2mm×1.6mm.Finally, the sample testing of the two both can satisfy the index requirements. Those two band-pass filter samples, the author made have compact structure and the sizes are smaller than the same type of filters.