Wave transmission lines and networks – Coupling networks – Frequency domain filters utilizing only lumped parameters
Reexamination Certificate
2002-09-03
2003-11-04
Wamsley, Patrick (Department: 2817)
Wave transmission lines and networks
Coupling networks
Frequency domain filters utilizing only lumped parameters
C333S175000
Reexamination Certificate
active
06642812
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high frequency circuit components, and more particularly, the present invention relates to a high frequency circuit component having an inductor and a capacitor in a laminate member which is formed by laminating a plurality of insulating layers.
2. Description of the Related Art
A known high frequency circuit component is a high frequency filter having a laminate member which is formed by laminating at least one insulating sheet having an inductor electrode pattern provided on the surface thereof, for forming an inductor, at least one pair of insulating sheets having capacitor electrode patterns provided on the surface thereof, for forming a capacitor, at least one insulating sheet having another conductive pattern on the surface thereof, and so forth. In the laminate member, a predetermined high frequency filter circuit is configured by electrically connecting the inductor including the inductor electrode pattern and the capacitor including the capacitor electrode patterns.
In the known high frequency filter, while the insulating sheets are laminated, the inductor electrode pattern defining the inductor is sometimes displaced relative to the capacitor electrode pattern defining the capacitor in a direction which is perpendicular to the lamination direction. In this case, variations in stray capacitance generated between the inductor electrode pattern and the capacitor electrode pattern occur, thereby causing the variations in the impedance of the inductor to take place.
When the inductor electrode pattern is used as an element of an inductor for an LC resonator or a &lgr;/4 resonator, the variations in impedance which occur due to the relative displacement of the insulating sheets as mentioned above cause its resonance frequency to vary. As a result, the desired characteristics of the high frequency filter are not obtained, and thus, product yield is reduced.
To solve these problems, it is necessary to make the distance between the inductor electrode pattern and the capacitor electrode pattern longer, or to arrange the inductor electrode pattern and the capacitor electrode pattern so as not to be overlaid with each other. However, these countermeasures increase the size of the laminate member, and accordingly, cause an increase in the size of the high frequency filter.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a very small high frequency circuit component in which the variations in stray capacitance which occur between an inductor electrode pattern and a capacitor electrode pattern are minimized and accordingly, the variations in the characteristics of the high frequency circuit component are minimized.
A high frequency circuit component according to a preferred embodiment of the present invention includes a laminate member including at least one pair of capacitor electrode patterns for defining a capacitor, at least one inductor electrode pattern for defining an inductor, and at least one pair of insulating layers disposed between the capacitor electrode patterns and the inductor electrode pattern. The laminate member is constructed by laminating at least the capacitor electrode patterns, the inductor electrode pattern, and the insulating layers. Also, when viewed from the lamination direction of the laminate member, the projections of the inductor electrode pattern onto the capacitor electrode patterns are included within the capacitor electrode patterns. In other words, when viewed from the lamination direction of the laminate member, the outer periphery of the inductor electrode pattern is within the outer periphery of the capacitor electrode patterns. Furthermore, the distances between the capacitor electrode patterns and the inductor electrode pattern preferably range from about 0.025 mm to about 1 mm. Moreover, an outer length A of the capacitor electrode patterns and a corresponding outer length B of the inductor electrode pattern preferably satisfy the following condition I:
A=B+&Dgr;,
where 0.1 mm≦&Dgr;≦1.0 mm (I).
With the above-described construction, even when the inductor electrode pattern and the corresponding capacitor electrode patterns are relatively displaced in a direction that is substantially perpendicular to the lamination direction during the process of laminating the insulating sheets, the opposing areas between the inductor electrode pattern and the capacitor electrode patterns do not vary, and thus, stray capacitances present in the space between the inductor electrode pattern and the capacitor electrode patterns always remain constant as long as the projections of the inductor electrode pattern onto the capacitor electrode patterns are included within the capacitor electrode patterns. Consequently, the variances in impedance of the inductor are reliably minimized and greatly reduced, and thus, the variations in the circuit characteristics due to the variations in displacement occurring during laminating the insulating sheets are minimized and greatly reduced, whereby a high-yield, high-frequency low-pass filter is provided.
In addition, according to a preferred embodiment of the present invention, the distances between the inductor electrode pattern and the corresponding capacitor electrode patterns are very short, and also the inductor electrode pattern and the capacitor electrode patterns are limitless in forming layout patterns including a spiral shape, a serpentine shape, and a combination of these shapes. As a result, the size of the high frequency low-pass filter is greatly reduced.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.
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Kariya Toshiaki
Kato Mitsuhide
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Wamsley Patrick
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