JPH07288441A - Laminated lc low-pass filter and characteristic adjusting method for the same - Google Patents

Abstract

PURPOSE:To provide the laminated LC filter, utilizable as an element for small power in a high frequency band, extremely miniaturized and adjustable in characteristic by providing both ends of a capacitor with inductors in series. CONSTITUTION:An LC parallel circuit is composed of an inductance L2 of a conductor pattern for inductor and a capacitor C2 provided between conductor patterns for capacitor connected to an input terminal, and the low-pass filter is constituted by grounding two conductor patterns for capacitor connected to the input terminal with capacitors C1 and C3 between the conductor patterns connected to a ground electrode. Inductors L12 and L22 are added at both the terminals of the capacitor C2 of this laminated LC low-pass filter, and inductors Ls1 and Ls3 are respectively added serially with the capacitors C1 and C3. Then, an attenuation amount out of a passing band is adjusted by adjusting the inductance of the inductors serially added to the capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated LC low-pass filter suitable for a low-pass filter in an antenna input stage of a GHz band communication device or the like, and a characteristic adjusting method thereof.

[0002]

2. Description of the Related Art The frequency band put to practical use in communication devices and the like is shifting to the high frequency region, and there is an increasing demand for circuits and circuit elements suitable for the GHz band. In the field of LC filters used as filters, traps, etc., there is an increasing demand for elements that are compatible with higher frequencies and smaller sizes.

To meet such demands, various LC filters have been proposed, and those usable in the GHz band have been commercialized. However, so far, 4.5mm ×
It has been realized only up to a size of 3.2 mm. In this field, there is an increasing demand for a size of 3.2 mm × 1.6 mm or smaller.

[0004]

SUMMARY OF THE INVENTION The present invention provides a laminated LC filter which can be used as an element for low power in a high frequency band such as mobile communication and which is extremely small and whose characteristics can be adjusted.

Further, the circuit configuration of the lumped constant circuit provides a laminated LC low-pass filter in which circuit constants can be easily set and designed easily.

[0006]

According to the present invention, a single-layer inductor conductor pattern is formed in a laminated body, a capacitor conductor pattern is formed integrally with the inductor conductor pattern, and an inductor is added to these conductor patterns. The above-mentioned problem is solved by adjusting.

That is, the inductor formed between the insulating layers, the first capacitor facing in parallel with the insulating layer and connected in parallel with the inductor, and one end connected to both ends of the parallel circuit and the other connected to the other end. A laminated LC low-pass filter comprising two grounded second capacitors, comprising an inductor in series across the first capacitor,
The feature is that an inductor is provided in series with the second capacitor, or both are provided.

Further, it is characterized in that the amount of attenuation outside the pass band is adjusted by adjusting the inductance of the added inductor.

[0009]

A capacitance is formed between the input / output terminal of the LC parallel circuit and the ground potential, and a low pass filter structure is formed. The characteristics can be arbitrarily selected by setting the inductance and capacitance values of the element, and the attenuation amount can be arbitrarily selected by the added inductance value.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, the basic structure of the laminated LC low-pass filter to which the present invention is applied will be described.

FIG. 1 is an exploded perspective view showing an embodiment of the present invention. Although a non-magnetic insulating material having a dielectric constant of about 5 is shown as being laminated by sheet lamination, conductor patterns and insulators may be alternately laminated by a printing method. The insulator 11a serves as a protective layer for the inductor,
The conductor pattern 12 for inductor is formed on b. This inductor conductor pattern 12 does not have to be a zigzag pattern as in this example, and may be a linear conductor pattern when the inductance value is small.

The insulator 11c and the insulator 11d are provided with a conductor pattern 13 for a capacitor which forms a capacitance in parallel with the inductor.
a and 13b are formed respectively. The capacitance is determined by the distance, the facing area, and the dielectric constant of the insulator. Also,
Insulator 11e includes conductor patterns 14a, 14 for capacitors.
b are formed respectively, and each face the conductor pattern 15 of the insulator 11f to form a capacitor. The conductor pattern 15 is drawn to the end face in a direction different from that of the other conductor patterns.

The laminated LC low pass filter shown in FIG. 2 is formed by laminating the insulators shown in FIG. 1 to form the terminal electrodes. The stack 16 includes a pair of input / output terminals 17 and a ground terminal.
18 are formed. The inductor conductor pattern 12, the capacitor conductor patterns 13a and 13b, and the capacitor conductor patterns 14a and 14b shown in FIG.
And the conductor pattern 15 is connected to the ground terminal 18. If a conductor pattern to be grounded is also formed on the inductor conductor pattern 12, a shield structure is formed and it is less likely to be affected by the surrounding electromagnetic field.

FIG. 3 is an equivalent circuit diagram of the laminated LC low pass filter having the above structure. L is the inductance L ₂ of the inductor conductor pattern and the capacitance C ₂ obtained between the capacitor conductor patterns connected to the input / output terminals.
A C parallel circuit is formed, and the capacitors C ₁ and C ₃ between the two capacitor conductor patterns connected to the input / output terminals and the conductor pattern connected to the ground electrode are grounded to form a low pass filter.

FIG. 4 is an equivalent circuit diagram of a laminated LC low-pass filter according to the present invention, in which inductors L ₁₂ and L ₂₂ are added to both ends of C ₂ shown in FIG. 3 and inductors are connected in series with C ₁ and C ₃ , respectively. L _S1 and L _S3 are added. These inductors can be formed by a conductor pattern that connects a terminal and a conductor pattern of a capacitance forming portion of a capacitor that faces each other.

By adjusting the inductance of the inductor added in series with the capacitor as described above, the amount of attenuation outside the pass band can be adjusted. Passband is 1.
It is shown in FIG. 5 whether the characteristics change like the above when the values of the inductors L ₁₂ and L ₂₂ are adjusted when the values of C _{1 to} C ₃ and L ₂ are set to be 9 GHz.

In FIG. 5, when the values of the inductors L ₁₂ and L ₂₂ are changed from 0.1 nH to 1.0 nH, the attenuation characteristic outside the pass band changes as shown by the curves 51 to 54. Curve 51 is inductor L
_When the values of ₁₂ and L ₂₂ are 0.1nH, the curve is the same.
52 is 0.25 nH, curve 53 is 0.5 nH, and curve 54 is 1.0 nH.

In the above example, it was confirmed that the guaranteed attenuation amount outside the pass band can be sufficiently secured by adjusting the values of the inductors L ₁₂ and L ₂₂ to 0.25 nH or less. It was also confirmed that when the inductance increases, a sufficient amount of attenuation cannot be obtained and the filter characteristics deteriorate.

FIG. 6 shows the results when the inductance values of the inductors L _S1 and L _S3 are changed.
It is the value when set in increments of 0.1nH up to 0.5nH.
The curve 61 is 0.1 nH and the curve 65 is 0.5 nH.

From the results shown in FIG. 6, the inductor L _S1 ,
It was confirmed that the attenuation characteristics were good when the value of L _S3 was in the range of 0.2 to 0.3 nH. If it deviates from that range, sufficient damping characteristics cannot be obtained.

[0021]

According to the present invention, an LC low pass filter useful for an antenna input stage for mobile communication and the like can be realized in a small size. Since it is a laminated integral structure, stable characteristics can be obtained.

Further, by selecting the characteristics of the constituent circuit elements, it becomes easy to obtain an LC low-pass filter having a desired attenuation characteristic.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a laminated LC low-pass filter to which the present invention is applied.

FIG. 2 is a perspective view of a laminated LC low-pass filter to which the present invention is applied.

FIG. 3 is an equivalent circuit diagram of a laminated LC low-pass filter to which the present invention is applied.

FIG. 4 is an equivalent circuit diagram of a laminated LC low-pass filter according to the present invention.

FIG. 5 is an explanatory diagram of characteristics of a laminated LC low-pass filter according to the present invention.

FIG. 6 is an explanatory diagram of characteristics of a laminated LC low-pass filter according to the present invention.

[Explanation of symbols]

 11: Insulator 12: Conductor pattern for inductor 13: Conductor pattern for capacitor 14: Conductor pattern for capacitor 15: Conductor pattern for ground

Claims (6)

[Claims] 1. An inductor formed between insulator layers,
Laminated LC comprising a first capacitor facing in parallel with an inductor via an insulating layer and connected in parallel, and two second capacitors having one end connected to both ends of the parallel circuit and the other grounded. A laminated LC low-pass filter, characterized in that, in the low-pass filter, inductors are provided in series at both ends of the first capacitor. 2. An inductor formed between insulator layers,
Laminated LC comprising a first capacitor facing in parallel with an inductor via an insulating layer and connected in parallel, and two second capacitors having one end connected to both ends of the parallel circuit and the other grounded. A laminated LC low-pass filter characterized by comprising an inductor in series with a second capacitor in the low-pass filter. 3. An inductor formed between insulator layers,
Laminated LC comprising a first capacitor facing in parallel with an inductor via an insulating layer and connected in parallel, and two second capacitors having one end connected to both ends of the parallel circuit and the other grounded. A laminated LC low-pass filter, characterized in that, in a low-pass filter, an inductor is provided in series at both ends of a first capacitor, and an inductor is provided in series with a second capacitor. 4. An inductor formed between insulator layers,
Laminated LC comprising a first capacitor facing in parallel with an inductor via an insulating layer and connected in parallel, and two second capacitors having one end connected to both ends of the parallel circuit and the other grounded. A method for adjusting characteristics of a low-pass filter, comprising: providing an inductor in series at both ends of a first capacitor and adjusting the inductance of the inductor. 5. An inductor formed between insulating layers,
Laminated LC comprising a first capacitor facing in parallel with an inductor via an insulating layer and connected in parallel, and two second capacitors having one end connected to both ends of the parallel circuit and the other grounded. A method for adjusting the characteristics of a low-pass filter, comprising: providing an inductor in series with a second capacitor, and adjusting the inductor of the inductor. 6. An inductor formed between insulator layers,
Laminated LC comprising a first capacitor facing in parallel with an inductor via an insulating layer and connected in parallel, and two second capacitors having one end connected to both ends of the parallel circuit and the other grounded. A method of adjusting the characteristics of a low-pass filter, characterized in that an inductor is provided in series at both ends of a first capacitor, an inductor is provided in series with a second capacitor, and the inductance of these inductors is adjusted. How to adjust filter characteristics.