JPH08222985A - Distributed capacitor forming structure in base plate mounting and serial resonance circuit - Google Patents

Abstract

PURPOSE: To facilitate and adjustment of the capacitance by adopting a distributed capacitor comprising a distributed constant for a capacitor of an electronic circuit such as a series resonance circuit and making a hole in a base plate in the vicinity of the distributed constant capacitor so as to avoid dispersion in the capacitance of the distributed capacitor. CONSTITUTION: A hole surrounding one terminal of a coil L is made in a base plate in the vicinity of the one terminal of the coil L. Since the base plate has a larger dielectric constant than that of air, the hole is made to remove the base plate in existence between the coil L and a copper foil provided to the lower side of the base plate and connecting to ground. Thus, the capacitance of a distributed capacitor in existence between the coil L and the copper foil forming a ground plane and connecting to ground is reduced. Furthermore, a conductor 1 is provided and its both ends are connected to the copper foil on the rear side of the base plate and to ground. The distance between the conductor 1 and the coil L is changed by tilting the conductor 1 with respect to the base plate. The capacitance of the distributed constant capacitor C3 comprising the distributed circuit constant is the sum of the distributed capacitance between the coil L and the conductor 1 and the distributed capacitance between the coil L and the copper foil on the base plate. The distance between the coil L and the conductor 1 is changed by tilting the conductor 1 with respect to the base plate to change the capacitance of the capacitor C3 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit such as a series resonance circuit in which a distributed capacitor formed by a distributed constant is used as a capacitor, and is particularly applied to a filter in an ultrahigh frequency region of 1 GHz or more. Is suitable.

[0002]

2. Description of the Related Art Conventionally, when constructing an electronic circuit such as a series resonance circuit composed of a coil and a capacitor, it is constructed by using a coil L and a capacitor C which are lumped constant components, as shown in FIG. It was normal. In FIG.
(A) is a circuit diagram of a high-pass filter, and the coil L and the capacitor C constitute a series resonance circuit.
(B) is a figure showing a mounting state of the series resonance circuit on a substrate. By the way, when manufacturing a filter having a sharp attenuation characteristic using a series resonance circuit, it is necessary to increase the Q of the series resonance circuit. Generally, the Q of the series resonance circuit is determined by Q = ωL / r = 1 / ωCr, the inductance of the coil L is large, and the capacitor C
The Q of the circuit can be increased by reducing the capacitance of. When the resonance frequency of the resonance circuit is in the super high frequency band of 1 GHz or higher, the capacitor C
In order to reduce the capacitance of, the capacitor C is replaced by a discrete component in which it is difficult to make a minute capacitance, and a distributed constant is used in which copper foil on both sides of the printed circuit board on which the resonant circuit is mounted is used as a ground plane. It has been proposed to use distributed capacitors.
In this way, the capacitance can be made smaller by using the distributed capacitor than in the case of using the lumped constant component, so that it is possible to obtain a series resonance circuit having a higher Q.

A series resonance circuit in which a capacitor C is formed by such a distributed capacitor will be described with reference to FIG. In FIG. 7, (a) is the coil L as in (a) of FIG.
FIG. 4 is a circuit diagram of a high-pass filter having a series resonance circuit composed of a capacitor C1 and a capacitor C1. The capacitor C1 is a distributed capacitor formed by a distributed constant and is represented by a broken line. (B) shows the mounting state of the series resonant circuit on the substrate, wherein the capacitor C1 is a coil L
It is not mounted as a lumped constant component because the distributed capacitance between the copper foil and the copper foil provided on the upper or lower surface of the substrate is used. The configuration shown in FIG. 7 allows the capacitor C to be formed more than when the lumped constant component is used.
Since the capacitance of No. 1 can be made small, the inductance of the coil L can be made large and the Q of the resonance circuit can be made larger than in the case of the structure shown in FIG. You can

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since the capacitor based on the lumped constant is replaced with the distributed capacitor formed based on the distributed constant, the capacitance can be made minute and the inductance of the coil can be made large, so that the Q can be increased. Is. However, since the distributed capacitor formed by the distributed constant is formed by using the copper foil on one side or both sides of the printed circuit board, it is coated to prevent the material of the printed circuit board and solder from getting on. Since the dielectric constant of the substrate varies depending on the material of the resist material and its thickness, there is a problem in that the capacitance varies and the reproducibility is poor. Further, in such a series resonance circuit, it is generally necessary to adjust the resonance frequency, and in the above-mentioned related art, the required performance was obtained by adjusting the density of the coils L. Became very critical, and there was a problem that the adjustment work required a lot of time and effort.

Therefore, an object of the present invention is to solve such a problem and to reduce the variation in the capacitance of a distributed capacitor formed by a distributed constant to improve the reproducibility. Further, another object is to make it possible to easily perform the adjustment work in the series resonance circuit.

[0006]

In order to achieve the above object, a structure for forming a distributed capacitor of the present invention is
A hole is provided near the side where the distributed capacitor of the electronic component is formed. Further, in the structure for forming the distributed capacitor of the present invention, the conductor connected to the ground plane is provided on the substrate near the side where the distributed capacitor of the electronic component is formed so as to face the electronic component. In addition, the conductor is configured to be movable so that the distance between the conductor and the electronic component can be changed. Furthermore, in the series resonant circuit of the present invention, the capacitor is a distributed capacitor formed between one end of the coil and the ground plane formed on the substrate, and the capacitor in the vicinity of one end of the coil in which the distributed capacitor is formed is disposed. The substrate is provided with holes. Still further, a conductor connected to the ground plane so as to face through the hole is provided near one end of the coil in which the distributed capacitor is formed. Furthermore, the conductor is configured to be movable so that the distance between the conductor and the coil can be changed.

[0007]

According to the present invention, by providing a hole in the substrate in the vicinity of the side where the distributed capacitor of an electronic component such as a coil is formed, the resist material in the hole is removed together with the substrate. It is possible to reduce variations in capacity and improve reproducibility. At the same time, the equivalent dielectric constant of the substrate can be reduced, and the capacitance formed by the distributed constant can be reduced.
Further, a conductor grounded through the hole is provided in the vicinity of the electronic component so as to project from the substrate, and the distance between the conductor and the electronic component or the facing area can be changed, whereby the capacitance of the distributed capacitor can be easily increased. Since it can be made variable, adjustment work becomes easy.

[0008]

FIG. 1 shows a first embodiment in which the present invention is applied to a series resonance circuit. In FIG. 1, (a) is a circuit diagram of a high-pass filter having a series resonance circuit, and a distributed capacitor C2 formed by a distributed constant is indicated by a broken line. (B) is a sectional view showing a mounted state of the series resonant circuit, and (c) is a top view showing the mounted state of the same. FIG.
As described in (b) and (c), in the present invention, a hole is formed in the substrate near one end of the coil L so as to surround one end of the coil L. Since the substrate has a dielectric constant higher than that of air, a hole is formed to remove the substrate existing between the coil L and the grounded copper foil provided on the lower surface of the substrate, and thus the coil L is removed. The capacitance of the distributed capacitor existing between the grounded copper foil forming the ground plane and the ground plane can be reduced. Furthermore, since the substrate and the resist material that have caused the variation in the capacitance of the distributed capacitor are removed, the variation in the capacitance of the distributed capacitor can be reduced and the reproducibility can be improved. In FIG. 1, the hole is formed in a substantially U shape, but the shape is not limited to this, and may be a substantially C shape or a U shape. Furthermore, when a hole is formed under the coil L, the influence of the substrate can be further reduced.

FIG. 2 shows a second embodiment in which the present invention is applied to a series resonance circuit. In FIG. 2, (a)
FIG. 4 is a circuit diagram of a high-pass filter having a series resonance circuit, and a variable capacitance type distributed capacitor C3 formed by a distributed constant is shown by a broken line. (B) is a cross-sectional view showing a mounted state of the series resonant circuit, (c) is a top view of the same,
(D) is a perspective view of the same. 2 is the one shown in FIG. 1 further provided with a conductor 1, and both ends of this conductor 1 are connected to the copper foil on the lower surface of the substrate and grounded. . Then, the conductor can be inclined with respect to the substrate as shown by the arrows in FIGS. 2B to 2C to change the distance from the coil L. In this case, the capacitance of the variable capacitance type distributed capacitor C3 formed by the distribution constant is
It is the sum of the distributed capacitances between the coil L and the conductor 1 and between the coil L and the copper foil forming the ground plane on the substrate,
By inclining the conductor 1 with respect to the substrate, the distance between the coil L and the conductor 1 can be changed, and the capacitance of the variable capacitance type distributed capacitor C3 can be changed.
Therefore, the resonance frequency can be adjusted by C3 instead of the critical L. In this embodiment, one linear conductor formed in a substantially U shape is adopted as the conductor 1, but the number of conductors is not limited to one, and a plurality of conductors may be provided. . Further, the shape of the conductor is not limited to this, and various modifications such as one or a plurality of rod-shaped conductors or using a conductor plate can be made.

Next, an embodiment in which the series resonance circuit of the present invention is applied to a mixer and a duplexer will be described with reference to FIGS. Like a mixer or demultiplexer used in a joint reception system that enables transmission of BS and CS broadcasts with an intermediate frequency in the ultra-high frequency range of 1 GHz or more using a single coaxial cable, a very close and wide frequency range can be achieved. In a mixer that mixes the signals that they have and a demultiplexer that demultiplexes into signals that have a very close wide frequency band,
The filter is required to have a sharp cutoff characteristic, and it is necessary to use a resonance circuit having a high Q. The present invention is most effective when applied to such an application.

FIG. 3 is a circuit diagram of such a mixer and a demultiplexer, which is proposed by the present applicant (Japanese Patent Application No. 6-263292). In FIG. 3, 10 is the first terminal, which is the lower frequency band (the intermediate frequency of BS broadcasting and 1 of UHF and VHF channels).
The first signal of 0 to 1332 MHz) is input. Reference numeral 2 is a low-pass filter (LPF), which includes four coils L1 to L4 connected in series and one coil L5 to L7 connected between a connecting portion between these coils and the ground.
And a series resonance circuit of one capacitor C1 to C3. Reference numeral 20 denotes a second terminal, which is a higher frequency band (intermediate frequency of CS broadcasting: 1355 to 1880 MH).
The second signal of z) is input. A high-pass filter (HPF) 6 includes four capacitors C4 to C7 connected in series, and one coil L8 to L10 and one capacitor C8 respectively connected between a connecting portion between these capacitors and the ground. .About.C10 series resonance circuit.

Reference numeral 7 is a bandpass filter (BPF), in which a capacitor C11, a coil L11, a coil L12 and a capacitor C12 are connected in series, and a connecting portion between the coil L11 and the coil L12 is grounded via a capacitor C13. ing. Reference numeral 8 denotes an impedance compensation circuit, in which two capacitors C14 and C15 are connected in series, and a connection portion between the capacitor C14 and the capacitor C12 of the BPF 7 is grounded via a coil L13,
The connection between the capacitors C14 and C15 is grounded via the coil L14. Reference numeral 30 is a third terminal for outputting a signal in which the first signal and the second signal are mixed, and is connected to the wire connection portion 9 to which the LPF 2 and the impedance compensation circuit 8 are connected. Although the above is described as a mixer, this circuit has reversibility, and the third terminal 3
When a signal that is demultiplexed from 0 to the first signal and the second signal is input, the first terminal 10 of the lower frequency band is input from the first terminal 10.
And the second terminal 20 outputs the second signal in the higher frequency band, and operates also as a duplexer.

In the mixer (demultiplexer) having such a configuration, the first signal in the lower frequency band input from the first terminal 10 is transmitted to the connection section 9 via the LPF 2. Further, the second signal in the higher frequency band input from the second terminal 20 is transmitted to the connection portion 9 via the HPF 6, BPF 7 and the impedance compensation circuit 8, and the first signal and the second signal are transmitted. It is mixed and output from the third terminal 30. BPF7 and impedance compensation circuit 8 connected in series between LPF2 and HPF6
Is to prevent mutual impedance interference between the LPF 2 and the HPF 6 by the impedance compensating circuit 8 to obtain a good filter characteristic. Further, due to the broad characteristic BPF functioning as a kind of buffer, the influence between the filters is increased. It is inserted to prevent and facilitate adjustment work. It should be noted that the series circuit of the BPF 7 and the impedance compensation circuit 8 has an HPF when the bandwidth of the first signal is wider than the bandwidth of the second signal as described above.
6 is inserted between the connection portion 9 and the LPF 2 and the connection portion 9 when the bandwidth of the second signal is narrower than the bandwidth of the first signal. With such a configuration, a very narrow stop band of about 23 MHz can be realized, and even if the low frequency band and the high frequency band are close to each other, both frequencies are close to each other. It is possible to mix or demultiplex signals in bands without affecting each other.

In the mixer (branching filter) thus constructed, the capacitors C1 and C2 in the LPF2 and the capacitor C9 in the HPF6, which are indicated by broken lines in FIG. 3, are formed by utilizing distributed capacitance. Has been done. FIG. 4 shows frequency characteristics when these capacitors are formed by the conventional distributed capacitance, and FIG. 5 shows frequency characteristics when these capacitors are formed by the method of the second embodiment of the present invention. 4 and 5, (a) is LP
The pass band loss characteristic of F2 is shown, and (b) shows the pass band loss characteristic of HPF6. In both cases of FIG. 4 and FIG. 5, since a capacitor is formed by distributed capacitance and a high Q is obtained, good characteristics having a very narrow stop bandwidth are obtained. And 1300MHz-1500M
In the band of Hz, the case of FIG. 5 in which the capacitor is formed according to the present invention is better than the case of FIG.

[0015]

According to the present invention, a capacitor in an electronic circuit such as a series resonance circuit is formed by a distributed constant, and a hole is formed in a substrate near a side where a distributed capacitor of an electronic component such as a coil is formed. Since it is provided, it is possible to reduce variations in the capacitance of the distributed capacitor formed by the distributed capacitance, and to improve reproducibility. At the same time, the capacitance of the distributed capacitor formed by the distributed capacitance can be made even smaller, and Q can be increased in the series resonance circuit. In addition, a grounded conductor is provided in the vicinity of an electronic component such as a coil so as to project from the substrate, and the capacitance of the distributed capacitor can be adjusted by adjusting the distance between the conductor and the electronic component such as the coil. Because
Adjustment work in the manufacturing process such as adjustment of the resonance frequency can be easily performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a series resonance circuit using a distributed capacitor of the present invention.

FIG. 2 is a diagram showing another embodiment of a series resonance circuit using the distributed capacitor of the present invention.

FIG. 3 is a circuit diagram of a mixer (branching filter) to which the present invention is applied.

FIG. 4 shows a case where a conventional distributed capacitor is used,
FIG. 4 is a pass band loss characteristic diagram of the mixer (branching filter) of FIG. 3.

5 is a pass band loss characteristic diagram of the mixer (branching filter) of FIG. 3 when the distributed capacitor according to the present invention is used.

FIG. 6 is a diagram showing a series resonance circuit using a conventional lumped constant component capacitor.

FIG. 7 is a diagram showing a series resonance circuit using a conventional distributed capacitor.

[Explanation of symbols]

 1 conductor 2 low-pass filter 6 high-pass filter 7 band-pass filter 8 impedance compensation circuit 9 connection part 10 first terminal 20 second terminal 30 third terminal

Claims (9)

[Claims] 1. A distributed capacitor used when a distributed capacitor formed between an electronic component and a ground plane formed on the substrate when the electronic component is mounted on the substrate is used as a capacitor in the electronic circuit. A structure for forming the distributed capacitor, wherein a hole is provided in the substrate near a side of the electronic component on which the distributed capacitor is formed. 2. A distributed capacitor used when a distributed capacitor formed between an electronic component and a ground plane formed on the substrate when the electronic component is mounted on the substrate is used as a capacitor in the electronic circuit. A structure for forming, in the substrate in the vicinity of the side where the distributed capacitor of the electronic component is formed, a conductor connected to the ground plane is projected from the substrate so as to face the electronic component. A structure for forming the distributed capacitor, wherein the structure is provided. 3. The structure for forming the distributed capacitor according to claim 2, wherein the conductor is provided so as to face the electronic component through the hole. 4. The hole according to claim 1, wherein the hole has a substantially U-shape, a substantially C-shape, or a substantially U-shape. Structure for forming a distributed capacitor. 5. The distributed capacitor according to claim 2, wherein the conductor is configured to be movable so that a distance between the conductor and the electronic component can be changed. Structure. 6. A series resonance circuit comprising a coil and a capacitor connected in series, the series resonance circuit being mounted on a substrate, the capacitor being formed on one end of the coil and on the substrate. And a ground plane, which is a distributed capacitor, wherein a hole is provided in the substrate in the vicinity of one end of the coil in which the distributed capacitor is formed. 7. A conductor connected to the ground plane so as to face the coil through the hole is provided near one end of the coil in which the distributed capacitor is formed. Item 7. A series resonant circuit according to Item 6. 8. The series resonant circuit according to claim 7, wherein the conductor is configured to be movable so that a distance between the conductor and the coil can be changed. 9. The hole according to claim 6, wherein the hole has any one of a substantially U-shape, a substantially C-shape, and a substantially U-shape. Series resonant circuit.