JP2752048B2 - Symmetric stripline resonator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a symmetrical stripline resonator constituting a resonance circuit in a microwave band of several hundred MHz to several GHz, and particularly to a bandpass filter, a duplexer, an oscillator and the like. The present invention relates to a small and low-loss symmetrical stripline resonator that can be suitably used.

(Background Art) Generally, as a resonator in a low frequency band, a lumped LC resonator including a coil of a lumped constant element and a capacitor is used, but in a microwave band of several hundred MHz to several GHz, Since it is extremely difficult to obtain a coil or capacitor of a lumped constant element, a resonator in a microwave band generally has a structure in which a resonant circuit is formed by opening or short-circuiting a terminal of a distributed constant circuit. Used.

As a kind of resonator using such a distributed constant circuit, conventionally, a coaxial line having a structure in which a dielectric is filled between a center conductor and an outer conductor 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, since the dielectric in the coaxial line is usually formed by a dry pressing method using ceramic powder, the thickness and the inner diameter of the dielectric are reduced in production. Therefore, there is a problem that the size cannot be reduced very much, and in particular, there is a problem that the protruding height in a state of being attached to the substrate is extremely large as compared with recent chip components.

For this reason, mobile communication devices such as mobile phones have been reduced in size, the mounting density of internal electronic components has been rapidly increasing, and the gap between mounting substrates tends to be narrower. Such a tall coaxial resonator determines the gap between the mounting substrates, and as a result, hinders an improvement in the mounting density of the entire device.

Therefore, in recent years, as a resonator using a distributed constant circuit, instead of such a coaxial resonator, an unbalanced microstrip line in which a strip conductor is arranged on a ground conductor via a dielectric, A so-called stripline resonator using a balanced stripline (symmetrical stripline) in which a strip conductor is arranged between a pair of ground conductors that are opposed to each other with a predetermined distance therebetween with a dielectric interposed therebetween is known. , Is being used.

In particular, especially in the case of using a balanced strip line, the dielectric constant of the dielectric can be set to be larger than that using an unbalanced microstrip line, The size of the resonator can be reduced even in a plane, and the strip conductor is buried inside the substrate, so that the area occupied on the substrate surface can be reduced. Therefore, it is possible to more effectively contribute to improvement of the mounting density of the entire device.

However, in a resonator using such a balanced microstrip line (a symmetrical stripline resonator), since the conductor loss is larger than that of the resonator using the coaxial line, the no-load Q of the circuit is reduced. Therefore, for applications where a very high Q is not required, such as a reactance element of a resonance circuit in a voltage-controlled oscillator for a mobile phone, for example, miniaturization and ease of manufacture and low Currently, cost reduction is the main focus, and it has been difficult to use it for applications requiring low loss, such as microwave filters.

By the way, the no-load Q in such a resonance circuit is
As is well known, the loss mainly due to the dielectric of the substrate (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 the frequency band below microwaves, conductor loss is higher than dielectric loss in circuit Dominant over Q. Therefore, in order to improve the no-load Q, for example, (a) using a material having a low specific resistance as a material for forming the strip conductor, or (b) increasing the width or thickness of the strip conductor, It is conceivable to suppress the conductor loss or (c) increase the thickness of the dielectric.

However, lowering the specific resistance of the strip conductor is naturally limited by material and cost constraints, and increasing the width of the strip conductor increases the occupied area in the substrate and causes unnecessary resonance. In the microwave band where the skin effect is large, even if the wall thickness is larger than the skin depth, it cannot contribute much to the reduction of the conductor loss. In addition, increasing the thickness of the dielectric is contrary to the above-described improvement in mounting density. Therefore, in any of these methods, a sufficient effect cannot be obtained with respect to the improvement of the no-load Q in the resonance circuit.

(Problem to be Solved) Here, the present invention has been made in view of the above circumstances, and the problem to be solved is that the conductor loss can be effectively reduced, and a high no-load Q can be obtained. An object of the present invention is to provide an improved symmetrical stripline resonator that can be obtained.

(Solution) According to the present invention, in order to solve the above-mentioned problem, the present invention is located between a pair of ground conductors formed on opposing surfaces of one dielectric with one dielectric interposed therebetween. As such, in the form embedded in the one dielectric,
In a symmetrical stripline resonator having a resonance circuit formed by a symmetrical stripline in which strip conductors are arranged, a plurality of the strip conductors are provided between the pair of grounding conductors in parallel with the grounding conductor, Embedded in the one dielectric, and in such one dielectric, in a state in which the dielectric is in close contact with the dielectric, the laminated conductors are arranged opposite to each other at a predetermined distance from each other, and at least one of the plurality of strip conductors has the same end. It is characterized in that a side portion is short-circuited to the pair of ground conductors.

Further, in the present invention, it is embedded in the one dielectric so as to be located between a pair of ground conductors respectively formed on opposing surfaces of the dielectric with the one dielectric interposed therebetween. In a form, in a symmetrical stripline resonator having a resonance circuit formed by a symmetrical stripline in which strip conductors are arranged, a plurality of the strip conductors are disposed between the pair of ground conductors and the ground conductor. In parallel, it is buried in the one dielectric, and in the one dielectric, in a state of being in close contact with the dielectric, they are arranged opposite to each other at a predetermined distance from each other in a stacked state, and one of the plurality of strip conductors is made identical. A symmetrical stripler wherein an end portion is short-circuited to the pair of ground conductors, while the other end portion is electrically connected to each other. Also down resonator, it is an its features.

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

First, FIGS. 1 to 3 show an embodiment of a quarter-wave symmetrical stripline resonator constructed according to the present invention. In these figures, reference numeral 10 denotes a double-sided board, and a thin-plate-shaped ground conductor 14 is disposed on each of both sides of one dielectric body 12 having a predetermined thickness. The structure is fixed. In addition,
Dielectric 12 and ground conductor 14 constituting such double-sided substrate 10
As the material, any of conventionally known materials can be used.In particular, in the case of the dielectric 12, in order to suppress the dielectric loss, it is preferable to use a material having a small dielectric loss tangent. desirable.

Further, two strip conductors 16, 16 are disposed between the ground conductors 14, 14 and buried in the dielectric 12. Each of these strip conductors 16 has a width W determined in consideration of the relative permittivity and the thickness of the dielectric 12 so as to give the characteristic impedance of the target line, and has a length of W. : L is set to be approximately 1/4 of the wavelength of the target resonance frequency.

Then, the two strip conductors 16, 16 are opposed to each other at a predetermined distance from each other, and the ground conductors 14,
In the middle part of 14, they are positioned so as to extend parallel to the ground conductors 14,
Between the layers 14, 14, the dielectric 12 is arranged in a laminated state with a predetermined thickness of the dielectric 12 interposed therebetween without any space therebetween.

In addition, as a material of these strip conductors 16 and 16, any of conventionally known materials can be adopted,
In particular, in order to suppress conductor loss, it is desirable to use a material having a small specific resistance. The thickness t of the strip conductor 16 is not particularly limited. However, in order to effectively suppress conductor loss, the strip conductor 16 should be formed with a thickness three times or more than the skin depth. Is desirable.

In addition, in these two strip conductors 16, 16, the strip conductors 16, 16
Are electrically connected to each other by a through hole 18 formed between the opposing surfaces of the two-sided substrate at the other end.
The ground conductors 14 and 14 are electrically connected to each other by a through hole 20 formed between the ground conductors 14 and 14.
Is short-circuited.

Thus, a / 4 wavelength type symmetrical strip line resonator having one end open and the other end short-circuited is formed. Further, in such a resonator, although not shown, one signal is input to, for example, the open ends of the strip conductors 16 and 16 as in the conventional resonator. . And those two strip conductors
16 and 16 are electrically connected to each other by the through holes 18 and 20, so that such signals can be advantageously input in phase.

Further, there, in the symmetrical stripline resonator having the structure as described above, since it has two strip conductors 16 and 16 extending parallel to each other,
The electric field distribution is generated in a form as shown in FIG. In short, in such a resonator, the two strip conductors 16
An electric field is generated not only from the opposing surfaces of the strip conductors 14 and 14 but also from the opposing surfaces of the strip conductors 16 and 16. It is possible to increase the skin portion through which the high-frequency current in the waveband flows, and to advantageously secure the effective cross-sectional area of the strip conductor.

Therefore, according to such a symmetrical stripline resonator, the conductor loss can be extremely effectively reduced, whereby the no-load Q can be advantageously improved. Thus, a low-loss resonator that can be advantageously used for an oscillator or the like can be advantageously realized.

Further, in the symmetrical strip line resonator having such a structure, since the width of the strip conductor is not increased, a small-sized one can be advantageously obtained.
There is no problem such as occurrence of unnecessary resonance.

Furthermore, in the symmetrical stripline resonator according to the present embodiment, the two strip conductors 16 are electrically connected to each other at their both ends by through holes 18 and 20, respectively. Even when the shapes of the two strip conductors 16 and 16 are slightly different due to a formation error or the like, the two strip conductors 16 and 16 have different shapes.
On the other hand, there is also an effect that the signal can be advantageously input in the same phase.

Next, FIGS. 4 and 5 show a symmetrical stripline resonator as another embodiment of the present invention.
That is, as is apparent from these figures, the present embodiment is a specific example in which the present invention is applied to a symmetrical stripline resonator of a type configured as a single unit and mounted on the surface of a substrate. It is.

The symmetrical stripline resonator according to the present embodiment includes a dielectric 22 having a substantially rectangular chip shape as a whole, and each of the dielectrics 22 is opposed to both surfaces of the dielectric 22 opposed in one direction. A pair of ground conductors 24, 24 are arranged and fixed so as to cover their surfaces.

In addition, a dielectric material is provided between the pair of ground conductors 24, 24.
At approximately the center of 22, three strip conductors 26, 2
6, 26 are buried in a state extending at a predetermined interval from each other over the entire length in the longitudinal direction of the dielectric 22, and are disposed in parallel with the ground conductors 24, 24, and between them. Since a layer of a predetermined thickness of the dielectric 22 is interposed, the dielectric 22 is arranged in a laminated structure as a whole.

The width (W) of the strip conductor 26 is determined so as to provide the characteristic impedance of the target line, and the length (l) of the strip conductor 26 is determined by the length (l) as in the above-described embodiment. Is set to be approximately 1/4 of the wavelength of the resonance frequency.

Also, as the material of the dielectric 22 and the strip conductor 26, similarly to the above embodiment, in order to suppress the dielectric loss and the conductor loss, a material having a small dielectric loss tangent and a material having a small specific resistance are preferably used, respectively. Will be done.

Further, in 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 thereof,
The connection conductor 30 conducts each other, and both ground conductors
24, 24 are short-circuited.

As a result, a / 4 wavelength type symmetrical strip line resonator having one end open and the other end short-circuited is formed.

Further, in such a symmetrical stripline resonator, as shown, on the surface of the substrate 32, with respect to a ground pad 34 formed on the substrate 32,
The ground conductor 24 is fixed in a conductive state, and furthermore, the lead 36 is connected to the connecting conductor 28, whereby the mounting is performed.

Then, a signal guided through a wiring (pattern) 38 formed on the substrate 32 is input to each strip conductor 26 from the connection conductor 28 through the lead 36,
There, in each of these strip conductors 26,
Since they are conducted to each other, such signals can be advantageously input in phase.

Therefore, even in the symmetrical strip line resonator having such a structure, the width of the strip conductor is not substantially increased by the opposing surfaces of the strip conductors 26, 26, 26 as in the above-described embodiment. , The effective cross-sectional area of the strip conductor can be advantageously ensured, whereby the conductor loss can be advantageously reduced, so that a small resonator with a high no-load Q can be advantageously realized. It is.

As mentioned above, although the Example of this invention was described in full detail, these are literal illustrations and this invention is not limited only to such a specific example, and is not solved.

For example, in the above embodiment, two strip conductors and three strip conductors are shown, but four or more strip conductors can be provided.

Further, in the symmetrical stripline resonator in the above embodiment, the plurality of strip conductors are electrically connected to each other. However, it is not always necessary to establish conduction to the strip conductors.

Furthermore, in each of the above-described embodiments, a specific example in which the present invention is applied to a / 4-wavelength symmetrical stripline resonator is shown. Of course, the present invention can also be advantageously applied to a two-wavelength symmetric stripline resonator.

Furthermore, in each of the above embodiments, the strip conductor is disposed at a substantially central portion between the ground conductors.
Depending on the application, such a strip conductor may be arranged so as to be biased toward one of the ground conductors.

In addition, although not enumerated one by one, the present invention can be embodied in aspects with various changes, modifications, improvements, etc. based on the knowledge of those skilled in the art. It is needless to say that any of them is included in the scope of the present invention unless departing from the gist of the present invention.

(Effects of the Invention) As is clear from the above description, in the symmetrical stripline resonator configured according to the present invention, a plurality of sheets embedded and arranged in one dielectric located between the ground conductors The strip conductor can advantageously secure an effective cross-sectional area without substantially increasing the width of the strip conductor, thereby effectively reducing the conductor loss. A high resonator can advantageously be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a symmetrical stripline resonator having a structure according to the present invention, and FIG. 2 is a longitudinal section of the symmetrical stripline resonator shown in FIG. FIG. 3 is a sectional view taken along the line III-I in FIG.
It is II sectional drawing. FIG. 4 is a perspective view showing another embodiment of the symmetrical stripline resonator having the structure according to the present invention, and FIG. 5 is a symmetrical stripline resonator shown in FIG. It is a longitudinal cross-sectional view of a container. 10: Double-sided board, 12, 22: Dielectric 14, 24: Ground conductor 16, 26: Strip conductor

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-263702 (JP, A) JP-A-63-156403 (JP, A) JP-A-63-50102 (JP, A) JP-A 62-263702 43901 (JP, A) JP-A-63-128801 (JP, A)

Claims (2)

(57) [Claims] 1. A strip embedded in a single dielectric so as to be located between a pair of ground conductors formed on opposing surfaces of the dielectric with the dielectric interposed therebetween. In a symmetrical stripline resonator having a resonance circuit formed by a symmetrical stripline having conductors disposed therein, a plurality of the strip conductors may be arranged between the pair of grounding conductors in parallel with the grounding conductor. It is buried in one dielectric, and in such one dielectric, in a state of being in close contact with the dielectric, they are arranged in a laminated manner at a predetermined interval from each other, and at least one of the plurality of strip conductors has the same end side. A symmetrical stripline resonator wherein a portion is short-circuited to the pair of ground conductors. 2. A strip embedded in said one dielectric so as to be located between a pair of ground conductors respectively formed on opposing surfaces of said dielectric with one dielectric interposed therebetween. In a symmetrical stripline resonator having a resonance circuit formed by a symmetrical stripline having conductors disposed therein, a plurality of the strip conductors may be arranged between the pair of grounding conductors in parallel with the grounding conductor. It is buried in one dielectric, and in such one dielectric, in a state of being in close contact with the dielectric, they are arranged in a laminated manner at a predetermined interval from each other, and one of the plurality of strip conductors at the same end side. To the pair of ground conductors,
A symmetrical stripline resonator characterized in that the other same-end-side portions are electrically connected to each other.