JP5320207B2 - Semi-coaxial resonator and filter device - Google Patents

Abstract

PURPOSE: A semi-coaxial resonator and a wave filter apparatus are provided to prevent the Q-value of the resonator from being reduced and minimize the size of the semi-coaxial resonator. CONSTITUTION: A metal case(1) arranges a sealing space. A round shaped resonator is installed in the case. The resonator is in a tapered shape from the base part to the top part. The diameter of the top part is smaller than the diameter of the bottom part. Electric wave is applied to the resonator from an input connector(4) through a combining plate(5). The electric wave is outputted from the resonator to an output connector(6) through the combining plate.

Description

The present invention relates to a semi-coaxial resonator and filter apparatus used in the mobile telephone filter device such as a base station apparatus.

  In recent years, in mobile phone systems, it has been essential to ensure high-sensitivity transmission / reception performance and high-quality call performance. For this reason, in filter devices used in base station devices and terminal devices of the system, signal components It is required to ensure a high Q value (quality factor) characteristic that hardly degrades the air quality and a stable passage characteristic even under severe temperature conditions. In addition, the demand for lower prices is extremely strict.

  Dielectric resonators are often used as resonators used in the filter device of the base station apparatus. The resonator element (resonator) of this resonator is made of ceramics, and ceramic resonators are difficult to manufacture, such as procuring suitable materials, creating elaborate molds, and controlling the temperature during firing. As it passed, it was expensive. For this reason, it is in a situation where use is hesitant in recent years when price competition is intense.

Accordingly, the inner conductor a metallic resonator in place of the resonator to the dielectric and the resonance body, semi-coaxial resonators metal housing for mounting it with the outer conductor being reviewed .

Semi coaxial resonator is placed in a housing (outer conductor) made of a metal such as aluminum, and are made of metallic tips is a flat cylindrical resonator such as brass (the inner conductor), the resonant This is a resonator in which a capacitance (leading capacitance) is formed between the top (open end) of the body and the body wall of the housing, and resonance is caused by the reactance component and the leading capacitance due to the inner conductor. Although it is made of metal and has the advantage of being inexpensive and easy to process, it has the disadvantage that the resonance frequency is likely to fluctuate due to the expansion and contraction of the inner conductor due to temperature changes.

  Conventionally, as a resonator of this type, a resonator constituting an inner conductor is constituted by two types of parts having different linear expansion coefficients, and the ratio of the lengths of these two types of parts is changed, whereby an apparent inner conductor There is known a semi-coaxial resonator (hereinafter, referred to as Prior Art 1) that cancels out a change in length due to a linear expansion coefficient and compensates for a change in resonance frequency based on a change in temperature (refer to Patent Document 1).

According to the prior art 1, it is possible to compensate for fluctuations in the resonance frequency due to changes in the linear expansion coefficient of the resonator based on temperature changes. For this purpose, two types of parts having different linear expansion coefficients are combined by a precise mechanical adjustment mechanism. You must be able to change their length ratio. Therefore, there is a problem that the structure is complicated and the manufacturing cost is increased.
In addition, since the resonator is attached to the housing wall at a right angle, there is a problem that the skin current of the resonator concentrates on the corner where the resonator rises from the housing wall and the Q value decreases. Further, if the gap length between the resonator and the housing wall is narrowed to reduce the size of the resonator, the head capacity increases, so the length of the resonator must be shortened in order to maintain a predetermined resonance frequency, Therefore, there is also a problem that the Q value as a resonator is lowered.

Japanese Patent Laid-Open No. 11-298213

  The present invention has been made in view of such circumstances, and a first object of the present invention is to be able to suppress fluctuations in resonance frequency due to temperature changes with a simple structure and low manufacturing cost. The second purpose is not to lower the Q value of the resonator at this time. A third object is to enable miniaturization.

(1) The present invention is a metal housing that constitutes a closed space, and the diameter is gradually reduced so that the cross section forms a taper shape from the base portion to the vicinity of the head portion, and the head portion starts from the vicinity of the head portion. it is a semi-coaxial resonator, characterized in that cross-section with a a metallic cylindrical resonator with varying diameter so as to constitute a curve toward parts.
(2) In a semi-coaxial resonator of the (1), wherein the housing half, characterized in that it includes a mounting pedestal resonator which rises in a curve in the housing and integrally from the housing surface a coaxial resonator.
(3) The present invention (1) or (2) in a semi-coaxial resonator, semi-coaxial resonators, characterized in that the linear expansion coefficient of the housing and greater than the linear expansion coefficient of the resonator It is.
(4) In the present invention, the metal housing constituting the closed space, each resonance chamber in which the casing is partitioned into a plurality of resonance chambers by partition walls, and the above (1) to (3) installed in each resonance chamber The resonator according to any one of the above, a frequency adjusting trimmer at a position facing the top of each resonator, and a coupling adjusting trimmer at a position facing the top of each wall. This is a characteristic filter device.
(5) The filter device according to (4), wherein the frequency adjustment trimmer and the coupling adjustment trimmer can be freely inserted into and removed from the housing.

  According to the present invention, it is possible to suppress fluctuations in the resonance frequency due to temperature changes with a simple structure and low manufacturing cost. At this time, the Q value of the resonator does not decrease and the size can be reduced.

It is a side cross-sectional view of the central portion of the semi-coaxial resonator according to the embodiment of the present invention. 4 is an explanatory diagram of a detailed configuration of a resonator 3. FIG. It is a side cross-sectional view of the central portion of the semi-coaxial resonator according to another embodiment of the present invention. It is explanatory drawing of the base 9a for installing the resonator 3. FIG. It is a block diagram of the 5-stage type | mold band pass filter which concerns on embodiment of this invention.

Will be described with reference to the drawings Embodiment 1 according to the embodiment of the present invention a semi-coaxial resonator. Figure 1 is a side sectional view of the central portion of the semi-coaxial resonator according to the embodiment of the present invention. In Figure 1, a semi-coaxial resonator 10, the resonance cross-section housing 1 composed of aluminum, a metal such as copper in a U-shape, which is also established by the screw 2 to the bottom surface of the housing 1 is made of metal Body 3, input connector 4 installed on the side of housing 1, coupling plate 5 for coupling input radio waves installed between the core portion of input connector 4 and the bottom surface of housing 1 to resonator 3, housing The output connector 6 installed on the side opposite to the side on which the first input connector 4 is installed, the core of the output connector 6 and the bottom surface of the housing 1 are combined, and the radio wave excited by the resonator 3 is combined. A coupling plate 7 for outputting and a lid body 8 for closing the opening of the housing 1 are provided.

FIG. 2 is an explanatory diagram of a detailed configuration of the resonator 3. In FIG. 2, d is the gap length between the lid 8 and the resonator 3, h is a dimension (length) in the height direction of the resonator 3, and c is a capacitance formed by the lid 8 and the resonator 3 ( Head capacity). The resonator 3 has a cylindrical shape with a taper-shaped cross section whose diameter gradually decreases from the base that contacts the bottom surface of the housing 1 toward the head facing the lid 8, and the head is a corner of the corner. The diameter is reduced so that the cross section has a circular shape with a predetermined radius R. Further, when the resonator 3 is considered as a semi- coaxial line, the height h is set to be the same as or slightly shorter than a quarter of the wavelength λ of the standing wave generated in the semi-coaxial line. With this dimension, a resonator that resonates at a predetermined center frequency can be configured by the reactance component based on this dimension and the capacity (head capacity) c formed at the head.

In FIG. 1 and FIG. 2, when a high frequency signal is input from the input connector 4 in a state where the housing 1 is closed by the lid 8, the high frequency signal is coupled to the resonator 3 by the coupling plate 5. By this coupling, the resonator 3 excites a high-frequency signal having a predetermined resonance frequency, and the excited high-frequency signal is output from the coupling plate 7 via the output connector 6.
Explaining the principle of excitation of the high-frequency signal in terms of a coaxial line, when a high-frequency signal is coupled to a coaxial line of length λ / 4 with one side grounded and the other side open via a coupling loop or the like, this signal is opened. In-phase reflection occurs at the end side, and anti-phase reflection occurs at the ground end side, and both ends reciprocate while being attenuated slightly by the transmission loss of the coaxial line to form a standing wave. Since the voltage on the ground side is fixed to zero while the phase of the current and the voltage is shifted by 90 degrees, the current is maximum on the ground side and the voltage is maximum on the open side. Once the signal energy is excited, it reciprocates at both ends without being attenuated, so high-frequency signal excitation occurs, that is, it functions as a resonator.
Since the resonator 3 based on the same principle has a cylindrical shape with a taper-shaped cross section in which the diameter gradually decreases from the base that contacts the bottom surface of the housing 1 toward the top that faces the lid 8, The cross-sectional area of the current path flowing through the surrounding skin becomes smaller as it goes to the head. For this reason, the skin current around the resonator 3 is uniformly distributed from the base portion to the head portion, thereby obtaining a resonance having a good Q value. The right side of FIG. 2 shows the state of current distributed over the height direction of the resonator 3.

  Further, due to suppression of fluctuations in the resonance frequency based on the temperature change of the filter device and a request for downsizing, the vertical, horizontal and height dimensions of the resonator, particularly the height, that is, the gap length d may be reduced as much as possible. . At this time, in the case of a completely cylindrical resonator shown in the prior art 1 and having a flat top portion, the head capacitance c increases as the gap length d decreases. Therefore, when the same resonance frequency is maintained, the resonator itself It will be necessary to shorten the length of. For this reason, the resonator is inevitably reduced in Q value. According to the resonator 3 according to the present embodiment, the diameter of the head portion is reduced so that the corner cross-section has a circular shape with a predetermined radius R. Therefore, even if the gap length d is shortened, the head capacitance c is conventional. It does not increase like the resonator shown in Technology 1. Therefore, it is not necessary to shorten the length of the resonator 3, and the Q value of the resonator does not decrease. Further, since there is no corner at the head, there is no possibility that a discharge phenomenon will occur even when a high-power high-frequency signal is input when used in a transmitter of a satellite communication device or the like, even if the gap length d is narrow.

(Embodiment 2) Next, a description will be given semi coaxial resonator according to another embodiment of the present invention. Figure 3 is a side cross-sectional view of the central portion of the semi-coaxial resonator according to another embodiment of the present invention. In FIG. 3, a resonator 20 includes a casing 9 having a U-shaped cross section and made of a metal such as aluminum or copper, and a casing 9 for installing the resonator 3 described in FIG. A pedestal 9a formed integrally is provided. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  FIG. 4 is an explanatory diagram of a pedestal 9a for installing the resonator 3. In the figure, the pedestal 9a has a curved shape that rises with a moderate radius r when viewed in cross-section from the bottom surface of the casing 9. The body 9 is integrally formed. And the resonator 3 is installed with the screw 2 on the base 9a. The resonator 3 is cut so that the bottom surface joined to the pedestal 9a forms a mounting rib portion 3a around the circumference.

As described in the description of the first embodiment, the resonator 3 is formed in a cylindrical shape having a tapered cross section in which the diameter gradually decreases from the base that contacts the bottom surface of the housing toward the top facing the lid. Since the corner portion has a circular shape with a predetermined radius R, a resonator having a good Q value can be obtained. However, since the rising portion of the resonator 3 from the bottom surface of the casing 1 becomes steep, the tendency of the skin current to concentrate on this portion is unavoidable, and this current has been a factor for lowering the Q value. Therefore, by installing the resonator 3 on the pedestal 9a that rises from the bottom surface of the casing 9 integrally with the casing 9 and has a moderate radius r, the skin current does not concentrate in the installation portion, so that the Q value The cause of the decline is eliminated.
Further, even when the mounting surface of the pedestal 9a is not processed into a complete horizontal plane due to the contact with the pedestal 9a by the mounting rib portion 3a, no gap is generated in the joint portion, so that the skin current distribution is not disturbed. The right side of FIG. 4 shows that the current distribution in the height direction of the resonator 3 is uniform from the top to the base of the resonator 3.

(Embodiment 3) Next, a description will suppress the deviation of the resonance frequency due to temperature changes of the semi-coaxial resonator according to the first and second embodiments. Semi coaxial resonator according to this embodiment, in the semi-coaxial resonator according to the first and second embodiments, the housing 1,9 and material coefficient of linear expansion greater than line resonator 3 constituting the lid 8 The one having an expansion coefficient is used.

The relationship between the size of the resonator 3 and the resonance frequency is
ω ・ ・ ・ Angular frequency
c ... top capacity
Z ₀・ ・ Characteristic impedance of resonator
θ ・ ・ ・ Resonator length (electrical length / phase angle θ <90 °)
d: Gap length
S: Area of the flat surface of the top of the resonator
If ε is the dielectric constant,
ω = d / (εSZ ₀ Tanθ)
= 1 / (cZ ₀ Tanθ)
It is. Accordingly, the resonance frequency increases as the head capacitance c decreases and the length θ of the resonator decreases.

  For example, when aluminum is used for the casing 1 and the lid 8, the linear expansion coefficient of aluminum is about 23 ppm / ° C., and if the resonator resonates at a resonance frequency of 1000 MHz at room temperature, the internal temperature of the resonator is 50 ° C. When it rises, the resonance frequency drops by 1.15 MHz and becomes 998.5 MHz. As described above, generally, the resonance frequency tends to decrease as the temperature rises.

Therefore, in this embodiment, in the semi-coaxial resonator according to the first and second embodiments, as the material constituting the housing 1, 9 and the lid 8, the material of the linear expansion coefficient larger linear expansion coefficient of the resonator 3 use. In the resonators 10 and 20 that can reduce the gap length d between the resonator 3 and the lid 8 by using such a material, the gap length d is increased due to the temperature rise, and consequently Since the head capacitance c becomes small, it is possible to suppress a shift in resonance frequency due to temperature change.

(Embodiment 4) further followed, multi-stage band-pass filter will be described using the semi-coaxial resonator according to the third embodiments.
FIG. 5 is a diagram illustrating a configuration of a five-stage bandpass filter according to the embodiment of the present invention. In the drawing, the casing 90 includes partition walls 90b (four locations) integrally formed with the casing 90 so as to constitute a plurality of, for example, five resonance chambers 21, 22, 23, 24, and 25. The height of the partition wall 90b is lower than the height of the housing 90, for example, about half thereof. The basic configuration of the lid 80 is the same as that of the lid 8, but in this embodiment, the frequency adjusting trimmer 11 (five locations) that can be inserted and removed at a location facing the top of the resonator 3 in each of the resonance chambers 21 to 25. The coupling adjustment trimmers 12 (four locations) that can be freely inserted and removed are provided at locations facing the top of each partition wall 90b. The same components as those in FIGS. 1 and 4 are denoted by the same reference numerals, and description thereof is omitted.

  When the housing 90 is closed by the lid 80 and a high frequency signal is input from the input connector 4 to the resonance chamber 21, the high frequency signal is coupled to the resonator 3 by the coupling plate 5 and excited at the resonance frequency. At this time, the frequency adjusting trimmer 11 is used to adjust the resonance frequency. The excited high frequency signal is sent to the resonance chamber 22 and coupled to the resonator 3 in the resonance chamber 22 to be excited at a frequency near the resonance frequency. At this time, the resonance frequency is adjusted by the frequency adjusting trimmer 11 again. Further, the coupling position relationship of the high frequency signals in the resonance chambers 21 and 22 is adjusted by the coupling adjustment trimmer 12, and as a result of this adjustment, the excited high frequency signal becomes a frequency response having two resonance frequency peaks.

By performing the same frequency adjustment and coupling adjustment in the resonance chambers 23, 24, and 25, a frequency response having five peaks is obtained and output through the coupling plate 7 and the output connector 6, so that a broadband pass filter is configured. be able to. Since the Q value of the resonator 3 in each resonance chamber is high, a high-quality broadband pass filter can be obtained. According to the actual machine test, the bandwidth was 20 MHz when the center frequency was 2 GHz.

DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Screw, 3 ... Resonator, 4 ... Input connector, 5 ... Coupling plate, 6 ... Output connector, 7 ... Coupling plate, 8 ... lid, 10 ... and a half coaxial resonator.

Claims (5)

A metal housing that forms a closed space, and a diameter that gradually decreases so that the cross section forms a taper shape from the base to the vicinity of the head, and the cross section forms a curve from the vicinity of the head to the head semi coaxial resonator a metal cylindrical resonator with varying diameters to, comprising the to. In the semi-coaxial resonator according to claim 1,
The housing is semi-coaxial resonator, characterized in that it includes a mounting pedestal resonator which rises in a curve in the housing and integrally from the housing surface. According to claim 1 or 2 half-coaxial resonator according,
Semi coaxial resonator, characterized in that the linear expansion coefficient of the housing and greater than the linear expansion coefficient of the resonator.   4. The metal housing constituting the closed space, each resonance chamber in which a casing is partitioned into a plurality of resonance chambers by partition walls, and the resonator according to claim 1 installed in each resonance chamber. And a frequency adjusting trimmer at a position facing the top of each resonator, and a coupling adjusting trimmer at a position facing the top of each wall. The filter device according to claim 4, wherein
Both of the frequency adjustment trimmer and the coupling adjustment trimmer can be inserted into and removed from the housing.

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