Design of Multilayer Rectangular Waveguide Band-pass Filters
Date Issued
2006
Date
2006
Author(s)
Shen, Tze-Min
DOI
zh-TW
Abstract
This thesis proposes several type of vertically stacked waveguide filters in a multilayer low-temperature co-fired ceramic (LTCC) structure. The vertical metal walls of the waveguide resonators are realized by closely spaced metal filled vias. A λg/4 microstrip line open stub is used as the feeding structure. The microstrip lines are utilized to excite the resonator through coupling slot etched in the top metal layer of the cavity. The excitation using an open stub contributes to fabrication simplicity with no need to drill via-holes, and also avoids the DC power loss
First we design waveguide filters with Chebyshev response. Direct couples between adjacent cavities in different layers are achieved by narrow slots at the common wall. To efficiently couple two adjacent cavities, the narrow slot is placed near via wall of the cavity where it can largely interrupt surface current. Compared with planar waveguide filters, the circuit area of multilayered filters can be reduced to a single cavity size by an appropriate arrangement.
Another type of filter with quasi-elliptical function is designed on multilayer structures also. Conventionally, to realize quasi-elliptical response, electric fields coupling are needed for cross couple. This can be achieved by a square aperture at the center of the common wall between nonadjacent cavities in different layers. And it is not easy to achieve on planar circuits. Besides, a new cross couple structure composed of via holes is used for the other quasi-elliptical filter, and the circuit area can be reduced to a single cavity size also.
Filters are designed at Ka-band with fractional bandwidth about 14% and fabricated by LTCC technology. All the filters exhibit an insertion loss better than 3dB at the center frequency and a rejection larger than 11dB over the pass-band.
Subjects
柴比雪夫
準橢圓函數
濾波器
低溫共燒陶瓷
矩形波導
Chebyshev
quasi elliptic
filter
LTCC
rectangular waveguide
Type
thesis
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