JPH051136Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The invention relates to the structure of an LC filter.
In particular, it relates to the structure of an LC filter using a serpentine conductor pattern that can be used in high frequency bands exceeding 100MHz.

[Prior art and its problems]

An LC filter that uses inductance with a spiral conductor pattern has been announced as a thin filter for high frequency bands.

However, this inductance element using a spiral conductor pattern has the following problems.
First, in order to draw out the leads from both ends of the conductor pattern, crossover wiring is required, which requires a double-sided printed circuit board using through holes. Therefore, there is a problem in that the cost increases.

Furthermore, there is distributed capacitance between adjacent conductor patterns of the concentric coils, which tends to cause high-frequency resonance, and the characteristics (Q) deteriorate at extremely high frequencies.

Furthermore, when a metal plate is brought close to a spiral conductor pattern, its inductance and Q deteriorate. Therefore, it is not possible to form a shield layer close to the coil. Therefore, jumps from adjacent circuits are likely to occur due to electromagnetic induction or electrostatic coupling.

Moreover, trimming the spiral conductor pattern is very difficult.

〔the purpose〕

The purpose of the present invention is to solve the above-mentioned problems and obtain a small and thin LC filter with good cutoff characteristics and less jump between input and output.

In particular, it is compatible with ultra-high frequency bands from 100MHz to 2GHz.
The purpose is to obtain an LC filter.

A further object of the present invention is to provide an LC filter that is small in size and can block mutual coupling even when conductor patterns are close to each other.

[Means for solving problems]

The present invention achieves the above object by arranging zigzag conductor patterns back to back with a conductor shield layer in between.

That is, in an LC filter in which an inductance is formed by a zigzag conductor pattern on an insulating substrate and a chip capacitor is arranged, the insulating substrate is arranged so that the back side of the surface provided with the zigzag conductor pattern faces each other. , is characterized in that it consists of two parts with a conductor layer between them.

The two parts may be composed of two separate substrates, or may be composed of a single bent flexible substrate.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing a low-pass filter according to an embodiment of the present invention. The substrates 10 and 20 are single-sided printed circuit boards. Meander conductor patterns 11 and 2 on each surface
1 is formed at a constant length from one side of the substrate.
The inductance is determined by this length, but in the ultra-high frequency band, the necessary inductance value can be obtained with only a few folding patterns.

Together with the zigzag conductor patterns 11 and 12,
Grounding conductor patterns 12 and 22 are formed on the surface of the substrate. This grounding conductor pattern 12, 2
2 is formed separately from the zigzag conductor patterns 11 and 21 and adjacent to the zigzag conductor patterns.

A chip capacitor is placed across the end of the zigzag conductor pattern and the grounding conductor pattern. In this example, two capacitors are placed on the substrate 10 and one capacitor is placed on the substrate 20.

The substrate 20 is turned over and bonded to the substrate 10 with the conductor plate 15 in between. In other words, there is a conductor plate 1 in the center.
5. The substrates 10 and 20 are placed back to back on the outside thereof.

Twisted conductor patterns 11 and 2 on two boards
1 ends are connected to each other, and two inductances are connected in series. Further, the grounding conductor patterns are also electrically connected to each other and are further connected to the conductor plate. A low-pass filter with input/output terminals and a ground terminal (not shown) is completed.

With the above structure, a three-terminal corpus filter consisting of two inductors connected in series and three capacitors connected in parallel can be obtained as shown in the equivalent circuit in Figure 2. .

The above example shows a low-pass filter consisting of two inductors and three capacitors, but the number and arrangement of these can be set arbitrarily.
In addition, LCs with other functions such as high-pass filters are also available.
Filters can be similarly configured. Furthermore,
Instead of using a metal plate, a conductor layer formed on the back surface of a printed board can also be used as a shield layer.
In order to adjust the characteristics, a part of the zigzag conductor pattern is connected, and this is cut out after assembly.
You can also trim.

FIG. 3 is a perspective view showing another embodiment of the present invention. The board 30 is made of a single flexible printed circuit board, and has a bent conductor pattern 3 on one surface.
1 and a grounding conductor pattern 32 are formed. This board has a structure in which the central portion is bent to the back side, and a conductive plate 35 is placed between them. Chip capacitors are not shown.

In the present invention, the coil with the zigzag conductor pattern utilizes inductance as a lumped constant, without considering the characteristic impedance of the transmission line.

〔effect〕

According to the present invention, an LC filter with excellent characteristics in an ultra-high frequency band of 100 MHz or more can be obtained.

Since it is thin and uses both sides, a small-sized LC filter can be obtained.

Moreover, since mutual coupling between the front and back inductances is blocked by the shield layer, an LC filter with good characteristics can be obtained.

Furthermore, this invention can be applied to various LC filters.
It is also possible to form two types of filters on the front and back sides.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram thereof, and FIG. 3 is a perspective view showing another embodiment of the present invention. 10, 20, 30...Substrate, 11, 21, 31
...Tangled conductor pattern, 12, 22, 32
...Grounding conductor pattern, 15, 35...Metal plate (shield layer).

Claims (1)

[Claims for Utility Model Registration] (1) In an LC filter comprising an inductance formed by a zigzag conductor pattern on an insulating substrate and a chip capacitor arranged thereon, the insulating substrate has a surface provided with the zigzag conductor pattern. An LC filter characterized in that it consists of two parts arranged so that their back surfaces face each other and a conductor layer provided between them. (2) The LC filter according to claim 1 of the utility model registration, characterized in that two insulating substrates are arranged with their back surfaces facing each other with a conductor layer in between. (3) The LC filter according to claim 1, wherein the insulating substrate is made of a flexible printed circuit board and is bent with the zigzag conductor pattern on the outside.