JPH0443703A - Symmetrical strip line resonator - Google Patents

Abstract

PURPOSE:To obtain a high no load Q by arranging plural strip conductors in parallel with ground conductors between a couple of ground conductors as layers at a prescribed interval so as to reduce the conductor loss effectively. CONSTITUTION:Two strip conductors 16, 16 are placed in parallel with ground conductors 14, 14 between the ground conductors 14, 14 at a prescribed interval as layers via a dielectric body 12. Thus, an electric field is produced not only from opposite faces to the ground conductors 14, 14 but only from opposite faces to the strip conductors 16, 16. Thus, a skin part in which a microwave band high frequency current flows is increased without substantially extending the width of the strip conductor 16 and the effective cross sectional area is utilized. Thus, the conductor loss is much effectively reduced and a high no load Q is realized.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a symmetrical stripline resonator that constitutes a resonant circuit in the microwave band of several hundred MHz to several G) (z), and particularly relates to a symmetrical stripline resonator that constitutes a resonant circuit in a microwave band of several hundred MHz to several G) (z), and in particular to a bandpass filter, a duplexer, The present invention relates to a small, low-loss symmetrical stripline resonator that can be suitably used in oscillators and the like.

(Background Art) Generally, a lumped LC resonator consisting of a lumped element coil and a capacitor is used as a resonator in the low frequency band, but in the microwave band of several hundred MHz to several GHz, Because it is extremely difficult to obtain lumped constant element coils and capacitors, resonators in the microwave band usually have a structure in which a resonant circuit is constructed by opening or shorting the ends of a distributed constant circuit. It is used.

As a type of resonator using such a distributed constant circuit, a coaxial line having a structure in which a dielectric material is filled between a center conductor and an outer conductor that are arranged coaxially with each other has been used. A so-called 1/2 wavelength type or 1/4 wavelength type coaxial resonator is known.

However, in such a coaxial resonator, one gX body in the coaxial line is usually formed by a dry press method using ceramic powder.
There are problems in that the wall thickness and inner diameter of the dielectric body are subject to production constraints, and it is not possible to reduce the size very much.In particular, compared to recent chip components, the protrusion height when attached to the board is significantly larger. It had the following.

For this reason, in recent years, as mobile communication devices such as mobile phones have become smaller, the mounting density of internal electronic components has rapidly increased, and the gaps between mounting boards have also become narrower. Such a tall coaxial resonator is
The gap between the mounting boards is determined, and as a result, the improvement in the mounting density of the entire device is hindered.

Therefore, in recent years, as a resonator using a distributed constant circuit, in place of such a coaxial resonator, an unbalanced microstrip line in which a strip conductor is arranged on a ground conductor via a dielectric material, A so-called strip line resonator uses a balanced strip line (symmetrical strip line) in which a strip conductor is arranged between a pair of ground conductors facing each other at a predetermined distance across a dielectric. , is beginning to be used.

In particular, in those using balanced strip lines, the dielectric constant of the a1 body can be set larger than in those using unbalanced microstrip lines. It is possible to reduce the size of the resonator in plan view, and the strip conductor is buried inside the board, reducing the area occupied on the board surface, reducing the gap between the mounting boards. This makes it possible to contribute more effectively to improvements in the packaging density of the entire device.

However, in a resonator using such a balanced microstrip line (symmetrical stripline resonator), the unloaded Q of the circuit is higher than that in the above-mentioned resonator using a coaxial line because the conductor loss is large. Therefore, it is necessary to reduce the size, ease of manufacture, and reduce the Currently, they are being adopted with a focus on cost reduction, and it has been difficult to use them in applications that require low loss, such as microwave filters.

By the way, as is well known, the no-load Q in such a resonant circuit is mainly determined by the loss due to the dielectric of the board (dielectric loss) and the loss due to the strip conductor (conductor loss). In recent years, materials with high dielectric constant and low loss have been developed, so in frequency bands below microwaves, conductor loss is more dominant than dielectric loss in the no-load Q of the circuit. It is. Therefore, in order to improve such no-load Q, for example, (a) use a material with low specific resistance as the material forming the strip conductor,
(b) It is possible to suppress conductor loss by increasing the width and thickness of the strip conductor, or (c) to increase the thickness of the dielectric.

However, there are limits to reducing the resistivity of strip conductors due to material and cost constraints, and increasing the width of strip conductors not only increases the area occupied within the board, but also causes unnecessary resonance. Further, in the microwave band where the skin effect is large, increasing the thickness of the strip conductor is difficult due to the risk of causing the skin depth, and even if the thickness is made thicker than the skin depth, it will not contribute much to reducing conductor loss. In addition, increasing the thickness of the dielectric goes against the aforementioned improvement in packaging density. Therefore, with any of these methods, it was not possible to obtain a sufficient effect in improving the no-load Q in the resonant circuit.

(Problem to be solved) Here, the present invention has been made against the background of the above-mentioned circumstances, and the problem to be solved is:
The object of the present invention is to provide an improved symmetrical stripline resonator in which conductor losses can be effectively reduced and high unloaded Q can be obtained.

(Solution Means) In order to solve this problem, the present invention provides a symmetrical structure in which a strip conductor is arranged between a pair of ground conductors that are placed in the same position at a predetermined distance with a dielectric between them. In a symmetrical strip line resonator in which a resonant circuit is configured by a strip line, a plurality of strip conductors are arranged parallel to the ground conductor between the pair of ground conductors, and are arranged in a predetermined manner with each other through the dielectric. The feature is that they are arranged in a stacked manner at intervals.

(Examples) Hereinafter, in order to clarify the present invention more specifically, examples of the present invention will be described in detail with reference to the drawings.

First, FIGS. 1 to 3 show an embodiment of a 1/4 wavelength symmetric strip line resonator constructed according to the present invention. In these figures, reference numeral 10 denotes a double-sided board, on which a dielectric material 12 of a predetermined thickness is sandwiched, and ground conductors 14 in the form of thin flat plates are disposed on both sides of the board and are integrally fixed. It is said that the structure consists of In addition,
As for the materials of the dielectric 12 and the ground conductor 14 constituting the double-sided board 10, any conventionally known materials can be used. Therefore, it is desirable to use a material with a small dielectric loss tangent.

Furthermore, two strip conductors 16.16 are embedded in the dielectric 12 between these ground conductors 14.14. These strip conductors 16.
16, the width: W is determined in consideration of the dielectric constant, thickness, etc. of the dielectric material 12 so as to give the desired characteristic impedance of the line, and the length: i!
, is set to be approximately 1/4 of the wavelength of the target resonance frequency.

The two strip conductors 16.16 are placed at a predetermined distance from each other and connected to the ground conductor 14.16.
The ground conductors 14 and 14 are arranged in a layered manner with the dielectric 12 interposed between the ground conductors 14 and 14. .

Note that any conventionally known material can be used as the material for these strip conductors 16, 16, but
In particular, in order to suppress conductor loss, it is desirable to use a material with low specific resistance. Further, the thickness t of the strip conductor 16 is not particularly limited, but in order to effectively suppress conductor loss, it should be formed to have a thickness three times the skin depth or greater. is desirable.

Moreover, in these two strip conductors 16.16, at one end side, such strip conductor 16.16.
They are electrically connected to each other by a through hole ]8 formed between the opposing surfaces of the double-sided board 10, while on the other end, a through hole 20 formed passing through the ground conductor ]4 and ]4 of the double-sided board 10 , are electrically connected to each other and short-circuited to both grounding conductors 14.14.

As a result, a quarter-wavelength symmetrical stripline resonator with one end open and the other end short-circuited is constructed. Furthermore, although not shown in the drawings, in such a resonator, one signal is input to the open end of the strip conductor 16, 16, for example, as in a conventional resonator. . Since these two strip conductors 16.16 are electrically connected to each other by the through holes 18.20, such signals can be advantageously input in the same phase.

Furthermore, since the symmetrical strip line resonator having the above-described structure has two strip conductors 16 and 16 extending parallel to each other, the electric field distribution thereof is This occurs in the form shown in the figure. In short, in such a resonator, an electric field is generated in the two strip conductors 16.16 not only from the surfaces facing the ground conductor 14.14 but also from the surfaces facing the strip conductors 16.16. Thereby, the strip conductor 16
It is possible to increase the skin portion through which a high frequency current in the microwave band flows without substantially increasing the width W of the strip conductor, thereby making it possible to advantageously secure the effective cross-sectional area of the strip conductor.

Therefore, with such a symmetrical stripline resonator, conductor loss can be reduced extremely effectively.
Thereby, the no-load Q can be advantageously improved,
Therefore, a low-loss resonator that can be advantageously used in microwave filters, duplexer 1 oscillators, etc. can be advantageously realized.

In addition, in a symmetrical strip line resonator having such a structure, since the width of the strip conductor is not expanded, it is possible to advantageously obtain a small size, and problems such as generation of unnecessary resonance are not caused. There is nothing like that.

Furthermore, in the symmetrical strip line resonator in this embodiment, the two strip conductors 16, 16 have through holes at their respective ends]8.
20, so even if the shapes of the two strip conductors 16.16 are slightly different due to formation errors, the signals will be in the same phase for both strip conductors 16.16. It also has the effect that it can be inputted advantageously.

Next, FIGS. 4 and 5 show a symmetrical stripline resonator as another embodiment of the present invention. That is, as is clear from these figures, this embodiment is a specific example of applying the present invention to a symmetric strip line resonator of the type that is constructed as a single unit and mounted on the surface of a substrate. It is.

The symmetrical stripline resonator in this embodiment includes a dielectric body 22 that has a generally rectangular chip shape as a whole, and has a dielectric body 22 that has a dielectric body 22 having a dielectric body 22 having a shape of a chip. , a pair of ground conductors 24, 24 are arranged and fixed so as to cover their surfaces.

Furthermore, between the pair of ground conductors 24.24, three strip conductors 26., 26.
The ground conductors 24.2 extend along the entire longitudinal length of the dielectric 22 at a predetermined distance from each other.
4, and the dielectric material 22 is interposed between them, so that the overall arrangement has a laminated structure.

As in the above embodiment, the width (W) of the strip conductor 26 is determined so as to provide the characteristic impedance of the intended line, and the length (ff) thereof is determined so as to provide the intended characteristic impedance of the line. Approximately 1/ of the wavelength of the resonant frequency
It is set to be 4.

Further, as in the above embodiment, materials with a small dielectric loss tangent and a material with a small specific resistance are preferably used as materials for the dielectric 22 and the strip conductor 26, respectively, in order to suppress dielectric loss and conductor loss. It will be used.

Furthermore, these three strip conductors 26.26.26
At one end thereof, they are electrically connected to each other by the connecting conductor 28, while at the other end, they are electrically conducting to each other through the connecting conductor 30, and are short-circuited to both grounding conductors 24 and 24. I'm being forced to do it.

As a result, a quarter-wavelength symmetrical stripline resonator with one end open and the other end short-circuited is constructed.

Further, in such a symmetrical stripline resonator, the ground conductor 24 is electrically connected to the ground pad 34 formed on the surface of the substrate 32 on the surface of the substrate 32, as shown in the figure. Then, the lead 36 is connected to the connecting conductor 28 for mounting.

Then, the wiring (pattern) 3 formed on the board 32
8 is routed from the connecting conductor 28 through the lead 36 to each strip conductor 26G, whereupon the signal is applied to each strip conductor 26G.
6, since they are electrically connected to each other, such signals can be advantageously inputted in the same phase.

Therefore, even in a symmetrical stripline resonator having such a structure, the width of the strip conductor 26, 26, 26 can be effectively avoided by the opposing surfaces of the strip conductor 26, 26, 26, as in the above embodiment. , the effective cross-sectional area of the strip conductor can be advantageously secured, and the conductor loss can thereby be advantageously reduced, so that a small resonator with a high no-load Q can be advantageously realized. It is.

Although the embodiments of the present invention have been described in detail above, these are literal illustrations, and the present invention is not to be construed as being limited only to these specific examples.

For example, in the above embodiments, two strip conductors and three strip conductors are shown, but it is also possible to arrange four or more strip conductors.

Further, in the symmetrical strip line resonator in the above embodiment, the plurality of strip conductors are electrically connected to each other, but it is not necessarily necessary to electrically conduct the strip conductors.

Furthermore, in the above embodiments, the present invention is applied to a quarter-wavelength symmetrical strip line resonator, but a structure in which both ends are open or short-circuited is also applicable. Of course, the present invention can also be advantageously applied to a 1/2 wavelength type symmetrical stripline resonator.

Furthermore, in all of the above embodiments, the strip conductor is
Although the strip conductor is disposed approximately in the center between the ground conductors, depending on the application, the strip conductor may be disposed biased toward one of the ground conductors.

In addition, although not listed, the present invention can be implemented with various changes, modifications, improvements, etc. based on the knowledge of those skilled in the art, and such embodiments may be modified from the present invention. It goes without saying that any of these are included within the scope of the present invention as long as they do not depart from the gist of the invention.

(Effects of the Invention) As is clear from the above description, in the symmetrical stripline resonator constructed according to the present invention, the width of the strip conductor can be increased by the plurality of strip conductors arranged between the ground conductors. A resonator that is small and has a high no-load Q is advantageous because the effective cross-sectional area can be advantageously secured without substantially increasing the bulk, and conductor loss can thereby be effectively reduced. This means that it can be realized.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of a symmetrical stripline resonator constructed according to the present invention, and FIG. 2 is a perspective view of the symmetrical stripline resonator shown in FIG. FIG. 3 is a longitudinal sectional view of I[I in FIG.
-I [I is a sectional view. Further, FIG. 4 is a perspective view showing another embodiment of a symmetrical stripline resonator having a structure according to the present invention, and FIG. 5 is a perspective view of the symmetrical stripline resonator shown in FIG. FIG. 3 is a longitudinal cross-sectional view of a resonator. 10: Double-sided substrate 12, 22: Dielectric 14.2
4: Ground conductor 16.26: Strip conductor Fig. 2 m4-. Figure 3 Figure 5 Procedural amendment (voluntary) September 9, 1991 1990 Patent application No. 151154 Name of the invention Relationship with the person who corrects the symmetrical strip line resonator Case Patent applicant

Claims (1)

[Claims] A symmetrical stripline in which a resonant circuit is constructed by a symmetrical stripline in which a strip conductor is arranged between a pair of ground conductors that are placed opposite each other at a predetermined distance with a dielectric interposed therebetween. In the resonator, a plurality of strip conductors are arranged between the pair of ground conductors in parallel with the ground conductors in a stacked manner with a predetermined spacing between them via the dielectric. type stripline resonator.