JPH06338701A - High frequency circuit board structure - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a high-frequency circuit board structure in which the amount of passing phases of chip parts is reduced and the microwave characteristics are improved. A dielectric substrate 1 having microstrip lines 2a and 2b formed on the front surface and a ground conductor 3 formed on the back surface
The dielectric substrate 1 is placed so that the chip component 5 connected to the microstrip lines 2a and 2b and the ground conductor 3 of the dielectric substrate 1 are in contact with each other, and the metal substrate 4 forming the ground plane 4a. A high-frequency circuit board structure comprising: a chip surface 5; and a ground plane 4 of the metal board 4.
A hole 6 is provided in the dielectric substrate 1 directly below the chip component 5 so that an air layer is formed between the dielectric substrate 1 and a.

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.

Reference numeral 31 is a dielectric substrate. Microstrip lines 32a and 32b are formed on the front surface of the dielectric substrate 31, and a ground conductor 33 is formed on the back surface. In the dielectric substrate 31 having the above configuration, the ground conductor 33 on the back surface is the metal substrate 3
4 is arranged on the metal substrate 34 so as to contact the ground plane 34a. A chip component 35 such as a resistor or a capacitor is connected between the microstrip lines 32a and 32b formed on the dielectric substrate 31.

Next, the dielectric substrate 3 having the structure shown in FIG.
A high-frequency circuit board structure in the case of short-circuiting the circuit on one surface with high frequency will be described with reference to FIG. In FIG. 4, the same parts as those in FIG. 3 are designated by the same reference numerals, and overlapping description will be omitted.

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

[0006]

When the chip component 35 is arranged on the dielectric substrate 31 as described above, the wavelength reduction rate immediately below the chip component 35 is approximately the reciprocal of the square root of the relative dielectric constant of the dielectric substrate 31. Becomes Therefore, the chip component 3
The wavelengths of the five parts are determined by the relative permittivity of the dielectric substrate 31. Therefore, for example, when the relative permittivity of the dielectric substrate 31 is increased in order to downsize the high frequency circuit formed on the dielectric substrate 31, the wavelength of the chip component 35 portion becomes shorter. When the wavelength of the chip component 35 is shortened in this way, the passing phase amount of the chip component 35 is increased and VSW is increased.
The microwave characteristics such as R are deteriorated.

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

The present invention solves the above drawbacks.
An object of the present invention is to provide a high-frequency circuit board structure in which the amount of passing phases of chip parts is reduced and the microwave characteristics are improved.

[0009]

According to the present invention, there is provided a dielectric substrate having a microstrip line formed on the front surface thereof and a ground conductor formed on the back surface thereof, a chip component connected to the microstrip line, and the dielectric material. In a high-frequency circuit board structure comprising a metal substrate on which the dielectric substrate is placed so that the ground conductor of the substrate is in contact with the ground substrate, an air layer is provided between the chip component and the ground surface of the metal substrate. A hole is provided in the dielectric substrate directly below the chip component so that

Further, a protrusion is formed on the surface of the metal substrate so that a part of the ground plane is inserted into the hole of the dielectric substrate.

[0011]

According to the above construction, since the holes are 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 becomes small, and deterioration of microwave characteristics such as VSWR can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below 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. Further, 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 the ground plane 4a of the metal substrate 4.
Is placed on the metal substrate 4 so as to be in contact with. Then, a chip component 5 made of, for example, a resistor is arranged between the microstrip lines 2a and 2b formed on the dielectric substrate 1. 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. Further, a hole 6 is formed in the dielectric substrate 1 directly below the chip component 5 so that an air layer is formed between the chip component 5 and the ground plane 4a of the metal substrate 4.

According to the above structure, since an air layer is formed between the chip component 5 and the ground plane 4a of the metal substrate 4,
The relative permittivity of the portion directly below the chip component 5 is approximately 1. Therefore, the wavelength of the chip component 5 portion is not shortened. Therefore, the passing phase amount of the chip component 5 becomes small, and V
The deterioration of SWR can be reduced.

Another embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and overlapping description will be omitted.

Although the chip component 5 is a resistor in FIG. 1,
In FIG. 2, for example, a capacitor is used as the chip component 5. Then, the through hole 7 is formed in the dielectric substrate 1, and the 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. In addition, the dielectric substrate 1 directly below the chip component 5
A protrusion 4b is formed on the metal substrate 4 so that a part of the ground plane 4a of the metal substrate 4 is inserted into the hole 6 formed in the metal substrate 4.

According to the above structure, the inductance component of the conductive layer 7a around the through hole 7 and the capacitor of the chip component 5 are connected in series to form a resonance circuit. Then, using this resonance circuit, for example, the circuit on the dielectric substrate 1 can be short-circuited at high frequency.

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

Further, the protrusion 4b is formed on the ground plane 4a of the metal substrate 4.
By providing, 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 short-circuitable frequency range can be widened. The protrusion 4b
The value of the characteristic impedance of the high frequency circuit can be adjusted appropriately by changing the height of the.

[0020]

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

[Brief description of drawings]

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

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

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

FIG. 4 is a schematic cross-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

Claims (2)

[Claims] 1. A dielectric substrate on which a microstrip line is formed on a front surface and a ground conductor is formed on a back surface, a chip component connected to the microstrip line, and a ground conductor of the dielectric substrate are in contact with each other. In a high-frequency circuit board structure including a metal substrate on which the dielectric substrate is placed and which forms a ground plane, the chip component such that an air layer is formed between the chip component and the ground plane of the metal substrate. A high-frequency circuit board structure, characterized in that a hole is provided in the dielectric substrate immediately below. 2. The high frequency circuit board structure according to claim 1, wherein a protrusion is formed on the surface of the metal substrate so that a part of the ground plane is inserted into a hole of the dielectric substrate.