JP2925428B2 - High frequency circuit board structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency circuit board structure used for microwave equipment and the like, and more particularly to a high-frequency circuit board structure for mounting chip parts such as resistors and capacitors.

[0002]

2. Description of the Related Art A conventional high-frequency circuit board structure will be described with reference to FIG.

A dielectric substrate 31 has microstrip lines 32a and 32b formed on the front surface of the dielectric substrate 31, and a ground conductor 33 formed on the back surface. In the dielectric substrate 31 having the above-described configuration, the ground conductor 33 on the back surface is
4 is disposed on the metal substrate 34 so as to be in contact with the ground plane 34a. Then, chip components 35 such as resistors and capacitors are connected between the microstrip lines 32a and 32b formed on the dielectric substrate 31.

Next, a dielectric substrate 3 having a configuration as shown in FIG.
The structure of a high-frequency circuit board when one circuit is short-circuited at high frequency will be described with reference to FIG. In FIG. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals, and duplicate description will be omitted.

In this case, the microstrip line 32
For example, a capacitor is used as the chip component 35 connected between the a and 32b. Then, a through hole 36 is formed in the dielectric substrate 31, and a circuit on the surface of the dielectric substrate 31 is short-circuited by a series circuit of the inductance of the conductive layer 37 formed around the through hole 36 and the capacitor of the chip component 35. .

[0006]

When the chip component 35 is disposed on the dielectric substrate 31 as described above, the wavelength shortening rate immediately below the chip component 35 is substantially the reciprocal of the square root of the dielectric constant of the dielectric substrate 31. Becomes Therefore, chip component 3
The wavelengths of the five portions are determined by the relative permittivity of the dielectric substrate 31. Therefore, in order to reduce the size of the high-frequency circuit formed on the dielectric substrate 31, for example, if the relative dielectric constant of the dielectric substrate 31 is increased, the wavelength of the chip component 35 becomes shorter. As described above, when the wavelength of the chip component 35 becomes short, the amount of passing phase of the chip component 35 increases, and the VSW
Microwave characteristics such as R deteriorate.

When a high-frequency circuit board structure having deteriorated microwave characteristics is used, for example, as a terminating resistor of a power distributor or a combiner, isolation deteriorates due to deterioration of VSWR characteristics. When the circuit on the dielectric substrate 31 is short-circuited by connecting the inductance of the conductive layer 37 around the through hole 36 and the capacitor of the chip component 35 in series, the increase in the amount of phase passing through the capacitor is absorbed. Therefore, for example, the value of the capacitance is selected to be small. For this reason, the frequency range in which short-circuiting is possible is narrowed.

The present invention solves the above disadvantages,
An object of the present invention is to provide a high-frequency circuit board structure in which the amount of phase passing through a chip component is reduced and microwave characteristics are improved.

[0009]

Means for Solving the Problems The present invention is formed on the microstrip line surface, is grounded conductor on the back surface is formed, and the dielectric substrate through-hole is formed, the sul
Hole formed in front of the microstrip line.
A conductive layer connected to the ground conductor of the dielectric substrate, and a chip component connected to the microstrip line;
A high-frequency circuit board structure comprising a metal substrate forming a ground plane, wherein the dielectric board is mounted so that a ground conductor of the dielectric board is in contact with the ground plane; A hole is provided in the dielectric substrate immediately below the chip component so that the air becomes an air layer.

[0010] Further, a projection is formed on the surface of the metal substrate so that a part of the ground plane enters the hole of the dielectric substrate.

[0011]

According to the above construction, since the hole is formed in the dielectric substrate immediately below the chip component, an air layer is formed between the chip component and the ground plane of the metal substrate. Therefore, the amount of passing phase in the chip component portion is reduced, and deterioration of microwave characteristics such as VSWR can be prevented.

[0012]

EXAMPLES Hereinafter, actual施例of the present invention, FIGS. 1 and
This will be described with reference to FIG .

Reference numeral 1 denotes a dielectric substrate, and microstrip lines 2a and 2b are formed on the surface of the dielectric substrate 1. The ground conductor 3 is formed on the back surface. In the dielectric substrate 1 having the above-described configuration, the ground conductor 3 is connected to the ground plane 4a of the metal substrate 4.
Is disposed on the metal substrate 4 so as to be in contact with. Then, between the microstrip lines 2a and 2b formed on the dielectric substrate 1, a chip component 5 made of, for example, a resistor is arranged. At this time, the width of the chip component 5 and the thickness of the dielectric substrate 1 are selected so as to have a desired impedance. A hole 6 is formed in the dielectric substrate 1 immediately below the chip component 5 so that an air space is formed between the chip component 5 and the ground plane 4a of the metal substrate 4.

According to the above structure, an air space is formed between the chip component 5 and the ground plane 4a of the metal substrate 4.
The relative dielectric constant immediately below the chip component 5 is substantially 1. Therefore, the wavelength of the chip component 5 is not shortened. For this reason, the passing phase amount of the chip component 5 becomes small, and V
Deterioration of SWR can be reduced.

Here, the circuit on the dielectric substrate 1 has a high frequency.
Will be described with reference to FIG. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be omitted.

In FIG. 1, the chip component 5 is a resistor,
In FIG. 2, for example, a capacitor is used as the chip component 5. Then, a through hole 7 is formed in the dielectric substrate 1, and a conductive layer 7 a is formed around the through hole 7. The conductive layer 7a is connected to the microstrip line 2b on the dielectric substrate 1 and the ground conductor 3 on the back surface of the dielectric substrate 1. The dielectric substrate 1 directly below the chip component 5
A projection 4b is formed on the metal substrate 4 so that a part of the ground plane 4a of the metal substrate 4 enters the hole 6 formed in the metal substrate 4.

According to the above configuration, a resonance circuit is formed by connecting the inductance of the conductive layer 7a around the through hole 7 and the capacitor of the chip component 5 in series. Using this resonance circuit, for example, a circuit on the dielectric substrate 1 can be short-circuited at a high frequency.

Since an air space is formed between the chip component 5 and the ground plane 4a of the metal substrate 4, the chip component 5
The relative permittivity of the portion directly below is almost 1, and the wavelength of the capacitor portion of the chip component 5 is not shortened.

A protrusion 4b is formed on the ground plane 4a of the metal substrate 4.
Is provided, the characteristic impedance of the high-frequency circuit can be reduced, and the equivalent inductance of the capacitor portion of the chip component 5 can be reduced. Therefore, when the high-frequency circuit on the dielectric substrate 1 is short-circuited by the series resonance of the sum of the equivalent inductance and the equivalent inductance of the through hole 7 and the capacitor 2 of the chip component 5, the frequency range in which short-circuiting can be performed can be widened. The protrusion 4b
By changing the height of the high-frequency circuit, the value of the characteristic impedance of the high-frequency circuit can be appropriately adjusted.

[0020]

According to the present invention, since the air space is formed between the chip component and the ground plane of the metal substrate, the amount of phase passing through the chip component can be reduced, and the microwave characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a conventional example.

FIG. 4 is a schematic sectional view showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric substrate 2a, 2b ... Microstrip line 3 ... Ground conductor 4 ... Metal substrate 4a ... Ground plane 5 ... Chip component 6 ... Hole

Continuation of the front page (56) References JP-A-56-6502 (JP, A) JP-A-3-99510 (JP, A) JP-A-5-110308 (JP, A) JP-A-62-247603 (JP) JP-A-60-214601 (JP, A) JP-A-50-117744 (JP, U)

Claims (2)

(57) [Claims] 1. A dielectric substrate in which a microstrip line is formed on a front surface, a ground conductor is formed on a rear surface, and a through hole is formed, and a dielectric substrate formed in the through hole, the microstrip line and the dielectric substrate are formed. A conductive layer connected to the ground conductor, a chip component forming a terminating impedance connected to the microstrip line, and the dielectric substrate placed on the dielectric substrate so that the ground conductor is in contact therewith ; In a high-frequency circuit board structure including a metal substrate forming a hole, a hole is provided in the dielectric substrate immediately below the chip component so that an air layer is formed between the chip component and a ground plane of the metal substrate. A high-frequency circuit board structure, characterized in that: 2. The high-frequency circuit board structure according to claim 1, wherein a projection is formed on the surface of the metal substrate so that a part of the ground plane enters a hole of the dielectric substrate.