JP2001148553A - Microwave circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To connect a microwave circuit formed on a small substrate with a circuit of a main substrate by matching the characteristic impedances with each other. SOLUTION: A microwave circuit, such as a BPF is formed by using a small substrate whose permittivity is larger than that of a main substrate 2 and is stacked on the main substrate 2. A signal line 4 of a small substrate 1 is connected with a signal line 6 of the main substrate 2. The edge of a connection part of the small substrate with the main substrate is cut obliquely, and a signal line 5 for characteristic impedance matching is formed on a cut surface 3. The upper end of the signal line 5 is connected with the signal line 4 on the small substrate, and the lower end is connected with the signal line 6 on the main substrate through soldering 7 or bonding, using conductive adhesive agent. The signal line 5 is so formed, that the width is narrowed corresponding to the thickness (distance from the bottom surface) of the small substrate starting from the upper end to the lower end, so that a prescribed characteristic impedance is realized along the whole line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave circuit and, more particularly, to a microwave circuit formed on a small substrate and connected to a circuit on a main substrate with matching characteristic impedance.

[0002]

2. Description of the Related Art When constructing a microwave circuit having a frequency of several GHz or more, a microstrip line which is advantageous in terms of easiness of production, cost, and the like is often used. Microstrip lines can be used as distributed constant elements in transmission lines and matching circuits to create circuit elements such as amplifiers, mixers, oscillators, and filters.When these circuit elements are formed on a single substrate However, the filter is generally not preferable in terms of reducing the size of the entire substrate due to its large size, and when there is a portion requiring manufacturing accuracy, the etching accuracy of the substrate is determined by this portion. It has limitations in terms of cost and accuracy. As a solution to this, there is a method in which a filter is formed on a small substrate having a higher relative dielectric constant than the main substrate and is connected to the main substrate. In this case, as shown in FIG.
Solder the through hole 23 of the main board 22 to the signal line 24 (2
5) or as shown in (b), the side through 26 of the small board 21 is soldered (27) to the signal line 24, or
As shown in (c), wire bonding 28 is used,
The method using through-holes or side-throughs tends to cause deterioration of characteristics due to mismatching of characteristic impedance, and the method using wire bonding provides good characteristics in terms of characteristic impedance matching. Both methods have drawbacks, for example, there is a problem in the aspect.

[0003]

SUMMARY OF THE INVENTION In view of the foregoing, the present invention forms a small substrate on a main substrate by forming a signal line for matching characteristic impedance at a portion of the small substrate connected to the main substrate. It is an object of the present invention to reduce characteristic impedance mismatch at the time of connection, to improve workability, and to reduce cost.

[0004]

In order to achieve the above object, in a microwave circuit according to the present invention, a part of a microwave circuit using a microstrip line is formed on a small substrate and connected to a circuit on a main substrate. In the device, the edge of the connection portion of the small substrate with the main substrate is cut obliquely, a signal line for characteristic impedance matching is provided on the cut surface, and the signal line of the small substrate and the signal line of the main substrate are provided through this signal line. And connect.

The signal line for characteristic impedance matching is
The width of each position from the upper end to the lower end is set so that the characteristic impedance has a predetermined value at each position from the upper end to the lower end.
It is formed to have a width determined by the distance from the bottom surface of the small substrate.

In other words, it is considered that the thickness of the substrate is gradually reduced from the upper end to the lower end due to the inclination of the edge of the small substrate, and an inverted trapezoidal shape in which the width is gradually narrowed from the upper end to the lower end is provided. A predetermined value is set at each position.

The signal line for characteristic impedance matching is
The upper end is connected to the signal line on the upper surface of the small substrate, and the small substrate is overlaid on the main substrate, and the lower end of the signal line for characteristic impedance matching is soldered or bonded with a conductive adhesive to the signal line on the main substrate. I do.

[0008] The small substrate is formed using a material having a higher relative dielectric constant than the main substrate. For example, the small substrate is formed using an alumina-based material, and the main substrate is formed using a cyanate resin-based or glass fluorine-based resin material.

[0009] The microwave circuit provided on the small substrate is, for example, a bandpass filter.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a configuration diagram of a main part of an embodiment of a microwave circuit according to the present invention, and FIG. 2 is a main part of a small substrate. In FIG. 1, 1 is a small substrate, 2 is a main substrate, 3 of the small substrate 1 is an oblique cut surface of an edge, 4 is a signal line constituting a microstrip line, and 5 is a signal line 4 formed on the oblique cut surface 3. , A signal line 6 constituting a microstrip line formed on the main substrate 2, and 7 a signal line connection by soldering or a conductive adhesive. Reference numeral 11 in FIG. 2 denotes a ground conductor of the small substrate 1.

It is known that the characteristic impedance of a microstrip line decreases as the substrate thickness decreases when the line width is constant, and increases as the line width decreases when the substrate thickness is constant. ing. Main board 2 of small board 1
Since the edge of the joining portion is cut obliquely, it can be considered that the thickness of the substrate gradually decreases from the upper end to the lower end of the cut surface 3. Therefore, as shown in FIG. 2, the signal line 5 formed on the cut surface 3 has a width h1 (= all plate thickness) of the small substrate 1 at the upper end.
If W1 is the same as the width of the signal line 4 on the upper surface, the characteristic impedance becomes the same as that of the signal line 4, and the lower end of the signal line 5 has the thickness h2 of the substrate. The width W2 of the signal line 5 is set to be the same as the location of W1. Since the cut surface 3 has a constant inclination, the signal line 5 has the same characteristic impedance at each position if it is formed in an inverted trapezoidal shape in which both upper and lower ends of the signal line 5 are connected by straight lines. The signal line 5 thus formed is formed by connecting the upper end to the signal line 4.
The lower end is connected to the signal line 6 of the main board 2 by soldering or bonding with a conductive adhesive. As a result, the signal line 4 of the small substrate 1 is connected to the signal line 6 of the main substrate 2 with the characteristic impedance matched.

The main substrate 2 is made of a cyanate resin having a relative dielectric constant of about 3.4 or a glass fluorine-based resin material having a relative dielectric constant of about 2.6. The small substrate 1 has a relative dielectric constant as large as about 10. For example, an LNB (low noise frequency converter) band-pass filter is formed using an alumina-based material having excellent high-frequency characteristics. Since the length of the microstrip line is inversely proportional to the square root of the relative permittivity of the substrate used, by using a substrate with a large relative permittivity for the small substrate,
A band-pass filter occupying a relatively large area can be formed in a small size, and by superimposing this small substrate on a main substrate, a microwave circuit can be formed in a small size. Since a portion of the substrate requiring etching accuracy can be manufactured separately from the main substrate, it is possible to reduce the cost and improve the performance of the entire circuit.

[0013]

As described above, according to the microwave circuit of the present invention, the bandpass filter requiring a relatively large area can be miniaturized by manufacturing on a small substrate having a larger relative dielectric constant than the main substrate. The edge of the connection between the small substrate and the main substrate is cut obliquely, a signal line (pattern) for characteristic impedance matching is formed on the cut surface, and the signal line of the small substrate and the signal line of the main substrate are connected. Therefore, the characteristic impedance mismatch caused by dividing and connecting the two substrates can be eliminated, and at the same time, the entire microwave circuit can be reduced in size, and etching of the substrate such as a bandpass filter can be performed. Since a part requiring precision can be manufactured separately from the main substrate, cost reduction and high performance of the entire circuit can be achieved.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of an embodiment of a microwave circuit according to the present invention.

FIGS. 2A and 2B are explanatory diagrams of a characteristic impedance matching signal line, wherein A is a front view and B is a side view.

FIG. 3 is an example of connection of a conventional microwave circuit, wherein A is through-hole connection, B is side-through connection, and C is wire bonding connection.

[Explanation of symbols]

 1, 21 Small board 2, 22 Main board 3 Diagonal cut surface of small board 4, 6, 24 Signal line 5 Signal line for characteristic impedance matching 7, 25, 27 Soldering 11 Ground conductor 23 Through hole 26 Side through 28 Wire bonding

Claims (8)

[Claims] 1. A part of a microwave circuit using a microstrip line is formed on a small substrate and connected to a circuit on a main substrate, wherein an edge of a connection portion of the small substrate with the main substrate is obliquely cut. And a signal line for characteristic impedance matching is provided on the cut surface, and the signal line of the small substrate and the signal line of the main substrate are connected via the signal line. 2. The signal line for characteristic impedance matching, wherein the width of each position from the upper end to the lower end is different from the bottom surface of the small substrate so that the characteristic impedance has a predetermined value at each position from the upper end to the lower end. 2. The microwave circuit according to claim 1, wherein the microwave circuit has a width determined by the distance. 3. An inverted trapezoidal type signal line for characteristic impedance matching in which the thickness of the substrate is gradually reduced from the upper end to the lower end due to the inclination of the edge of the small substrate, and the horizontal width is gradually reduced from the upper end to the lower end. 2. The microwave circuit according to claim 1, wherein the characteristic impedance has a predetermined value at each position from the upper end to the lower end. 4. The microwave circuit according to claim 1, wherein the characteristic impedance matching signal line is formed by connecting an upper end thereof to a signal line on an upper surface of the small substrate. 5. The small substrate according to claim 1, wherein the small substrate is superposed on the main substrate, and a lower end of the characteristic impedance matching signal line is soldered or adhered to the signal line of the main substrate with a conductive adhesive. Microwave circuit. 6. The microwave circuit according to claim 1, wherein the small substrate is formed using a material having a higher relative dielectric constant than the main substrate. 7. The microwave circuit according to claim 1, wherein the small substrate is formed using an alumina-based material, and the main substrate is formed using a cyanate resin-based or glass fluorine-based resin material. 8. The microwave circuit according to claim 1, wherein the microwave circuit provided on the small substrate is a band-pass filter.