JP2007242683A - High-frequency circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency circuit board which is superior in a high frequency characteristic, and in which a high frequency module can be miniaturized. <P>SOLUTION: The high frequency circuit board 10 is provided with a board body 11 of a multilayer structure, connection pads 12a and 12b for mounting a high frequency transistor 18 formed on a surface of the board body 11, via hole conductors 13a and 13b extending from an end on an inner side of the connection pads 12a and 12b to an inner part of the board body 11, and matching circuits 14a and 14b which are formed in an inner layer of the board body 11 and whose one end is connected to the via hole conductors 13a and 13b. Lengths L<SB>1</SB>of the connection pads 12a and 12b are set to λ/2 with respect to a wavelength λ of an operation frequency of a high frequency transistor 18. Tips P<SB>1</SB>of the connection pads 12a and 12b become open ends. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high frequency circuit board, and more particularly to a structure of a high frequency circuit board on which a high frequency transistor is mounted.

An example of a high-frequency circuit board on which a high-frequency transistor is mounted is disclosed in Patent Document 1. As shown in FIG. 5, in the high-frequency circuit board 1, a plate capacitor 3 is mounted on the surface, and the high-frequency transistor 2 is mounted on the plate capacitor 3. Both the source-side leads 2 c and 2 d of the high-frequency transistor 2 are soldered onto the plate capacitor 3. Also, connection pads 1a and 1b are formed on the surface of the high-frequency circuit board 1, and the drain-side and gate-side leads 2a and 2b of the high-frequency transistor are connected to the connection pads 1a and 1b by soldering or the like. A matching circuit for adjusting the impedance to a predetermined value is connected to the tips of the connection pads 1a and 1b for connecting these leads, and the drain and gate of the high-frequency transistor 2 are connected via this matching circuit. Connected to other circuits.
Japanese Patent No. 2875302

In recent years, downsizing of electronic devices has been demanded, and further downsizing of the high-frequency circuit board 1 is also desired. However, in the conventional high-frequency circuit board 1 described above, as shown in FIG. 6 (a) and (b), the length L of the matching circuit 1a, 1b a length _{L 4,} including equivalent to the connection pads 1a, 1b _Since it is much longer than ₃ , there is a problem that the substrate surface is widely occupied by the matching circuits 1a and 1b. For this reason, it is difficult to secure a mounting area for other components, which has been a factor that hinders downsizing of the high frequency module.

  Accordingly, an object of the present invention is to provide a high-frequency circuit board that is excellent in high-frequency characteristics and capable of downsizing a high-frequency module.

  The object of the present invention is to provide a substrate body, a connection pad for mounting a high-frequency transistor formed on the surface of the substrate body, and a via-hole conductor extending from the inner end of the connection pad to the inside of the substrate body. And a matching circuit having one end connected to the via-hole conductor, and the connection pad has a line length set to λ / 2 with respect to a wavelength λ of an operating frequency of the high-frequency transistor, and a tip thereof is an open end This is achieved by a high-frequency circuit board characterized in that

  The above object of the present invention is also achieved by a substrate body, a connection pad formed on the surface of the substrate body for mounting a high-frequency transistor, and a via-hole conductor extending from the inner end of the connection pad to the inside of the substrate body. And a matching circuit having one end connected to the via-hole conductor, and the connection pad has a line length set to λ / 4 with respect to the wavelength λ of the operating frequency of the high-frequency transistor, and its tip is short-circuited It is also achieved by a high frequency circuit board characterized by being at the edge.

  In the present invention, the substrate body preferably has a multilayer structure, the matching circuit is preferably formed in an inner layer of the substrate body, and the matching circuit is more preferably sandwiched between upper and lower ground layers. . According to this, it is possible to reliably function as a matching circuit without being affected by the surrounding electromagnetic field.

  ADVANTAGE OF THE INVENTION According to this invention, the high frequency circuit board which is excellent in a high frequency characteristic and can reduce the size of a high frequency module can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view showing the structure of a high-frequency circuit board 10 according to the first embodiment of the present invention.

  As shown in FIG. 1, the high-frequency circuit board 10 includes a multilayer substrate body 11, connection pads 12 a and 12 b for mounting the high-frequency transistor 18 formed on the surface of the substrate body 11, and the inside of the connection pads 12 a and 12 b. Via-hole conductors 13a and 13b extending from the end (near the high-frequency transistor body) to the inside of the substrate body 11, and matching circuits 14a and 14b formed in the inner layer of the substrate body 11 and connected at one end to the via-hole conductors 13a and 13b; It has.

  The substrate body 11 is a multilayer ceramic substrate, for example, and the surface of the substrate body 11 is used as a mounting region for components such as capacitors and resistors as well as the high-frequency transistor 18. A ground layer 15 a is formed on the bottom surface of the substrate body 11. The ground layer is also formed on the inner layer of the substrate body 11, and the matching circuits 14a and 14b are sandwiched between the upper and lower ground layers 15b and 15a. Thereby, the matching circuits 14a and 14b can function reliably without being influenced by the surrounding electromagnetic field.

A plate capacitor 19 is provided directly below the high frequency transistor 18, and a source side lead 18 c of the high frequency transistor 18 is connected to the plate capacitor 19 by soldering or the like. The drain side lead 18a and the gate side lead 18b of the high frequency transistor 18 are connected to the connection pads 12a and 12b by soldering or the like, respectively. Connection pads 12a, and 12b length _{L 1} is set to lambda / 2 with respect to the wavelength lambda of the operating frequency of the high-frequency transistor 18, the connection pads 12a, the tip _{P 1} and 12b is an open end. Accordingly, the connection pads 12a and 12b can be electrically ignored when viewed from the high frequency transistor 18. That is, the matching circuits 14a and 14b can be configured from the base of the high-frequency transistor 18, and the high-frequency module can be greatly downsized.

  As described above, according to the first embodiment, since the matching circuits 14a and 14b are formed in the inner layer of the substrate 11, the area occupied by the conductor pattern on the substrate surface can be reduced, and the high-frequency module can be downsized. Can contribute. In addition, since the length of the connection pad for connecting the lead of the high-frequency transistor is set to λ / 2 and the tip of the connection pad is an open end, the matching circuit can be configured ignoring the impedance of the connection pad. The matching circuit can be easily designed.

  FIG. 2 is a schematic cross-sectional view showing the structure of the high-frequency circuit board 20 according to the second embodiment of the present invention. FIG. 3 is a schematic top view of the high-frequency circuit board 20.

As shown in FIG. 2, characterized in the high-frequency circuit board 20, the connection pads 12a, the length of 12b _{L 2} is set to lambda / 4 relative to the wavelength lambda of the operating frequency of the high-frequency transistor 18, the connection pads 12a, 12b It lies in the front end P ₂ is in the short-circuited end. To connect the pads 12a, 12b of the tip P ₂ and the short-circuited end, in the present embodiment, as shown in FIG. 3, to form a substantially fan-shaped capacitance patterns 21 on both sides of the front end portion of the connection pads 12a, 12b. The capacitance pattern 21 forms a capacitor with the inner ground layer 15b and is short-circuited at the operating frequency. Thus, as in the first embodiment, the connection pads 12a and 12b can be electrically ignored as viewed from the high-frequency transistor 18. That is, the matching circuits 14a and 14b can be configured from the base of the high-frequency transistor 18, and the high-frequency module can be greatly downsized. Further, in the high-frequency circuit board 20, since the tips of the connection pads 12a and 12b are short-circuited via the capacitors, the DC voltage is short-circuited even when a DC voltage bias is applied to the drain and gate of the transistor. This can be prevented.

  As described above, according to the second embodiment, since the matching circuits 14a and 14b are formed in the inner layer of the substrate 11, the area occupied by the conductor pattern on the substrate surface can be reduced, and the high-frequency module can be downsized. Can contribute. In addition, since the length of the connection pad for connecting the lead of the high frequency transistor is set to λ / 4 and its tip is a short-circuited end, the matching circuit can be configured ignoring the impedance of the connection pad. The matching circuit can be easily designed.

  In each of the embodiments described above, the length of the connection pad is λ / 2 or λ / 4. However, these lengths do not have to be exact, and some variation is allowed.

  FIG. 4 is a graph showing the relationship between the variation in the length of the connection pad and the gain of the high-frequency transistor in the high-frequency circuit board 20 in which the length of the connection pad is λ / 4. In FIG. 4, the horizontal axis indicates the length of the connection pad normalized with respect to λ / 4, and the vertical axis indicates the gain (dB).

  As shown in FIG. 4, when the length of the connection pad is 1, that is, λ / 4, the gain of the high-frequency transistor is about 12.3 dB, and when the length is 0.95 (0.95 × λ / 4) The gain is about 10.8 dB, and the gain at 1.05 (1.05 × λ / 4) is about 11.1 dB. That is, even if the length of the connection pad deviates by 5% from λ / 4, the decrease in gain is only about 2%. Since the variation in gain of about 2% is within the allowable range as the manufacturing variation of the high frequency circuit, it can be said that the variation in the length of the connection pad is allowed to be at least about 5%. Similarly, when the length of the connection pad is λ / 2, it can be said that the variation in the length of the connection pad is allowed to be at least about 5%.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention, and these should also be included in the scope of the present invention. Needless to say.

  For example, in the second embodiment, the substantially fan-shaped capacitance pattern 21 is provided on both sides of the connection pad. However, any shape can be used as long as the connection pad can be short-circuited at the operating frequency. There may be.

FIG. 1 is a schematic cross-sectional view showing the structure of a high-frequency circuit board 10 according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the structure of the high-frequency circuit board 20 according to the second embodiment of the present invention. FIG. 3 is a schematic top view of the high-frequency circuit board 20. FIG. 4 is a graph showing the relationship between the variation in the length of the connection pad and the gain of the high-frequency transistor in the high-frequency circuit board 20 in which the length of the connection pad is λ / 4. FIG. 5 is a schematic perspective view showing a configuration of a conventional high-frequency circuit board 1. FIG. 6A is a schematic top view of a conventional high-frequency circuit board 1, and FIG. 6B is a side view thereof.

Explanation of symbols

1 High-frequency circuit board 1a Connection pad (matching circuit)
1b Connection pad (matching circuit)
2 High frequency transistors 2a to 2d High frequency transistor lead 3 Flat capacitor 10 High frequency circuit board 11 Substrate body 12a, 12b Connection pads 13a, 13b Via hole conductors 14a, 14b Matching circuit 15a, 15b Ground layer 18a Drain side lead 18b Gate side lead 18c, 18d Source side lead 18 High frequency transistor 19 Flat capacitor 20 High frequency circuit board 21 Capacitance pattern

Claims (4)

A substrate body;
A connection pad for mounting a high-frequency transistor formed on the surface of the substrate body;
A via-hole conductor extending from the inner end of the connection pad into the substrate body;
A matching circuit having one end connected to the via-hole conductor;
The connection pad has a line length set to λ / 2 with respect to a wavelength λ of an operating frequency of the high-frequency transistor, and a tip of the connection pad is an open end. A substrate body;
A connection pad for mounting a high-frequency transistor formed on the surface of the substrate body;
A via-hole conductor extending from the inner end of the connection pad into the substrate body;
A matching circuit having one end connected to the via-hole conductor;
The high-frequency circuit board according to claim 1, wherein a line length of the connection pad is set to λ / 4 with respect to a wavelength λ of an operating frequency of the high-frequency transistor, and a tip thereof is a short-circuited end. The substrate body has a multilayer structure;
The high-frequency circuit board according to claim 1, wherein the matching circuit is formed in an inner layer of the substrate body. 4. The high frequency circuit board according to claim 3, wherein the matching circuit is sandwiched between upper and lower ground layers.

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