Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1994-12-21
2001-05-29
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S219000
Reexamination Certificate
active
06239674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency circuit element comprising resonators such as a filter or a branching filter for use in high-frequency signal processing devices used in communication systems.
2. Description of the Related Art
High-frequency circuit elements comprising resonators such as a filter, or a duplexer are essential in the field of high-frequency communication systems. In particular, the field of mobile communication systems requires a filter with a narrow bandwidth to efficiently use a frequency band. Further, in a base station for mobile communications or a communication satellite, a filter having a narrow band range, little loss, compact size and durability against a large electric power is desirable .
Conventional high-frequency circuit resonant filters comprise dielectric resonators, transmission line resonators, or surface acoustic wave elements. Conventional resonant filters comprising transmission line resonators are most widely used since they are compact, applicable to a high frequency as far as microwaves or milliwaves, and easily combined with the other circuits or elements to form a two-dimensional structure on a substrate. An example of a conventional resonant filter comprising a transmission line structure is a half-wavelength resonator which is most widely used. By connecting half-wavelength resonators plurally, high-frequency circuit elements such as filters can be formed (“Shokai Reidai Enshu Microwave Circuit” published by Tokyo Denki Daigaku Shuppankyoku).
Another conventional example is a resonant filter having a planar circuit structure. A typical example of a resonant filter having a planar circuit structure is one comprising a round planar resonator having a partially protruding portion at its circumference to couple dipole modes to display a filter characteristic (Institute of Electronics and Communication Engineers of Japan's article collection 72/8 Vol.55-B No.8 “Analysis of Microwave Planar Circuit” written by Tanroku MIYOSHI and Takanori OKOSHI).
However, resonators with a transmission line structure, such as half-wavelength resonators, have problems since high-frequency current tends to concentrate within the conductor to considerably increase resistance loss therein, which leads to the deterioration of the Q-value when used in a resonator or the increased loss when used in a filter. A half-wavelength resonator commonly used with a microstrip line structure has a disadvantage of radiation loss from the circuit.
Further, a resonator with a planar circuit structure comprising a round planar resonator with a protruding portion has electric current concentration in the protruding portion, and the discontinued structure at the protruding portion causes signal waves radiation to space, which will lead to the deterioration of the Q-value of the resonator, and the increased loss in this type of filter.
Such effects become more conspicuous if the structure is minimized or the operating frequency becomes higher. As a resonator of a comparatively little loss and good power handling capacity, dielectric resonators are used but the solid structure and bulkiness prohibits reducing the size of the high-frequency circuit elements.
Use of a superconductor can reduce the loss of such high-frequency circuit elements. However, in the above-mentioned conventional structures, superconductivity cannot be sustained in the above-mentioned conventional structure of a resonator due to the excessive concentration of the electric current. Therefore, it is difficult to use a signal of a large power. In the virtual measuring, the maximum input power is lower than 100 mW which is below a practical level.
With reference to the above-mentioned problems, obviously it is essential to solve such problems of resonators of a transmission line structure or a plane circuit structure to obtain a high-frequency circuit element including a resonant filter which has a compact and two-dimensional structure, matches other circuits or elements well, and performs excellently when applied to high-frequencies, such as microwaves or milliwaves.
SUMMARY OF THE INVENTION
The present invention provides a resonator with little loss caused by conductor resistance, a high Q-value in a compact structure. The present invention also provides a high-frequency circuit element of an excellent quality comprising the resonator in order to solve the above-mentioned conventional problems.
A first example of the resonator of this invention comprises a conductor formed on a substrate. The conductor has two fundamental dipole modes polarizing orthogonally to each other as the resonant modes and there is no degeneration therein.
It is preferable that the conductor has a smooth outline.
It is preferable that the resonator comprises a conductor formed on a substrate having an elliptical shape.
In the first example of the resonator, it is preferable to have a structure selected from the group consisting of a microstrip line structure, a strip line structure, and a coplaner wave guide structure. It is further preferable to form a grounding electrode on the substrate in the vicinity of the conductor in the structure.
In the first example of the resonator, it is preferable to have a plate-type conductor placed between two grounded planes which are located in parallel.
In the first embodiment of the resonator, it is preferable to have a slit in the conductor. It is further preferable to orient the slit perpendicular to the current direction of a resonant mode.
A first example of the high-frequency circuit element of the present invention has a resonator comprised of a conductor formed on a substrate which has two dipole modes polarizing orthogonally without degeneration as the resonant modes, and at least one input/output terminal bonds to the resonator at a point on the circumference of the conductor comprising the resonator.
Moreover, in the first example of the high-frequency circuit element, it is preferable that two points on the circumference of the conductor comprising the resonator at which only one of the two dipole modes of the resonant modes of the resonator polarizing orthogonally is excited are the input/output bonding points
1
,
2
. The input/output terminals are bonded to the resonator at the input/output bonding points
1
,
2
.
Further, in the first example of the high-frequency circuit element, it is preferable that two points on the circumference of the conductor comprising the resonator at which only one of the two dipole modes of the resonant modes of the resonator polarizing orthogonally is excited are the input/output bonding points
1
,
2
and two other points at which only the other one of the two dipole modes is excited are the input/output bonding points
3
,
4
. The input/output terminals are bonded to the resonator at the input/output bonding points
1
-
4
.
In the first example of the high-frequency circuit element, it is preferable that two points on the circumference of the conductor comprising the resonator at which both of the two dipole modes of the resonant modes of the resonator polarizing orthogonally are equally excited and are located at neighboring positions are the input/output bonding points
1
,
2
. The input/output terminals are bonded to the resonator at the input/output bonding points
1
,
2
.
In the first example of the high-frequency circuit element, it is preferable that two points on the circumference of the conductor comprising the resonator at which both of the dipole modes of the resonant modes of the resonator polarizing orthogonally are equally excited and are located opposite each other are the input/output bonding points
1
,
2
. The input/output terminals are bonded to the resonator at the input/output bonding points
1
,
2
.
In the first example of the high-frequency circuit element, it is preferable that on the circumference of the conductor comprising the resonator, there is a point at which both of the dipole modes of the resonant modes of the resonator are equally excit
Enokihara Akira
Setsune Kentaro
Bettendorf Justin P.
Jones Stephen E.
Matsushita Electric Industrial Co. Ltd
Morrison & Foerster / LLP
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