JPH11298213A - Semicoaxial resonator and semicoaxial resonator filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semicoaxial resonator and a semicoaxial resonator filter with which a resonance frequency and a central frequency can be stably maintained even when a temperature change occurs, and the temperature characteristics of an entire device can be improved when the device is integrated into a microwave device. SOLUTION: A resonance stick consisting of an inner conductor is composed of two kinds of components 2a and 2b. The respective components 2a and 2b are selected so that linear expansion coefficients can be different. One of two components 2a and 2b is made of brass and the other one is made of invar having a low linear expansion coefficient remarkably away from the linear expansion coefficient of brass. Two kinds of components 2a and 2b are partially screw-shaped so as to easily adjust a length L2 of the inner conductor and its rate (L2a/L2b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semi-coaxial resonator used in a microwave device and a semi-coaxial resonator filter using the semi-coaxial resonator.

[0002]

2. Description of the Related Art A semi-coaxial resonator is a resonator in which a capacitance is formed between an open end of an inner conductor and a tube wall forming an outer conductor, and the resonance wavelength is changed by changing the capacitance. The capacitance is changed by moving the inner conductor or by changing the length of an adjusting member provided on the facing surface on the open side of the inner conductor. Also, a plurality of semi-coaxial resonators can be coupled to form a filter.

FIG. 4 is a sectional view showing a filter formed by using three conventional semi-coaxial resonators. As shown in the figure, the metal housing 1 forms an outer conductor of each semi-coaxial resonator, and has a coupling window 7 for coupling each semi-coaxial resonator. Inside each semi-coaxial resonator, a resonance rod 20 having one end screwed to the metal housing 1 and the other end open is attached. The resonance rod 20 forms an inner conductor of the semi-coaxial resonator.
The metal casing 1 facing the other end of each resonance rod 20 is provided with a frequency adjusting screw 3. A semi-coaxial resonator filter is formed by combining each semi-coaxial resonator,
Such a semi-coaxial resonator filter is disclosed in, for example,
No. 8161.

[0004] In a microwave radio device, a band-pass filter is used to split an input signal into respective channel signals. Therefore, the band-pass filter is required to adjust the center frequency within the frequency range of the used device. FIG.
When the semi-coaxial resonator filter shown in (1) is used, the center frequency is changed by the frequency adjusting screw 3. The frequency adjusting screw 3 adjusts the length of the gap 4 between the resonance rod 20 and the metal housing 1 to change the capacitance between the open end of the inner conductor and the tube wall, thereby controlling the resonance of the semi-coaxial resonator. Changing the frequency, and consequently the center frequency of the filter.

FIG. 5 is a partial sectional view showing a part of the semi-coaxial resonator shown in FIG. FIG. 5 shows that the length of the outer conductor is L1, the length of the inner conductor is L2, and the insertion length of the frequency adjusting screw is L.
3. The gap length is indicated as L4. The resonance rod 20
The length L2 of the inner conductor is fixed so as to be shorter than １ ／ wavelength. The resonance frequency is determined mainly by the length L2 of the inner conductor. However, when the ambient temperature changes, L2 changes due to linear expansion of the resonance rod 20, and as a result, the resonance frequency changes. Therefore, as the resonance rod 20,
A material having a small linear expansion coefficient such as invar is used.

FIG. 6 shows a gap length L4 in a semi-coaxial resonator.
(Mm) and the frequency sensitivity (resonance frequency variation ΔF (MH
z) / change amount ΔL4 (mm) of gap length L4, the length L2 of the inner conductor is 12.5 mm and 13.5 mm
It is explanatory drawing shown about the case of. FIG. 7 shows the relationship between the screw insertion length L3 (mm) and the gap length L4 (mm) and the amount of change ΔF (MHz) of the resonance frequency, when the length L2 of the inner conductor is 12.5 mm and 13.5 mm. It is explanatory drawing shown about a case. Note that the outer conductor diameter of the semi-coaxial resonator at the time of measuring the frequency variation and the frequency sensitivity is 27 mm, the inner conductor diameter is 7 mm, and the outer conductor length L1 is 23 mm.

As can be seen from FIG. 7, the resonance frequency does not change much when the screw insertion length L3 is small, but changes greatly when the screw insertion length L3 increases, that is, when the gap length L4 decreases. In other words, as can be seen from FIG. 6, when the gap length L4 is set small in order to lower the resonance frequency, the small change amount ΔL of the gap length L4 is set.
4, the resonance frequency greatly changes. Then, even in a band-pass filter using a semi-coaxial resonator (semi-coaxial resonator band-pass filter), the center frequency greatly changes according to a minute change in the gap length L4.

[0008]

As described above, in the conventional semi-coaxial resonator and the semi-coaxial resonator band-pass filter, when the gap length L4 of the semi-coaxial resonator is small, the gap length L4
The resonance frequency and the center frequency are greatly changed by only a small change in the resonance frequency. Therefore, even if the linear expansion coefficient of the material of the resonance rod 20 is small, if the gap length L4 of the semi-coaxial resonator is small, the amount of frequency change due to the effect of temperature change cannot be ignored.

Japanese Patent Application Laid-Open No. 57-48803 discloses a coaxial resonator filter, which includes a temperature compensation mechanism made of a metal having a different linear expansion coefficient from that of an inner conductor in order to compensate for expansion and contraction of the inner conductor due to a temperature change. The technology used is disclosed. The temperature compensating mechanism is not applied directly to the inner conductor, but is attached to the outside of the housing forming the outer conductor. In the coaxial resonator filter, for example, when the inner conductor expands in response to a temperature change, the temperature compensating member compresses the outer conductor and keeps the length of the inner conductor in the housing forming the outer conductor constant.
However, in such a configuration, temperature compensation can be performed for a fixed resonance frequency, but it cannot be applied to an application in which a center frequency is largely changed such as a band-pass filter used in a microwave device. .

According to the present invention, a semi-coaxial antenna capable of stably maintaining a resonance frequency and a center frequency even when a temperature change occurs and improving the temperature characteristics of the entire device when incorporated in a microwave device. It is an object to provide a resonator and a semi-coaxial resonator filter.

[0011]

A semi-coaxial resonator and a semi-coaxial resonator filter according to the present invention have an inner conductor made of a plurality of metals having different linear expansion coefficients. In addition, the semi-coaxial resonator and the semi-coaxial resonator filter include an adjustment mechanism that changes the length of each of the plurality of metal outer conductors. The semi-coaxial resonator and the semi-coaxial resonator filter are:
For example, another metal is screwed to a part of the outer periphery of one of a plurality of metals, and the other metal is screwed to an outer conductor.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a semi-coaxial resonator filter formed using the semi-coaxial resonator according to the present invention. As shown in the figure, the metal housing 1 forms an outer conductor of each semi-coaxial resonator, and has a coupling window 7 for coupling each semi-coaxial resonator. A resonance rod 2 having one end screwed to the metal housing 1 and the other end open is mounted inside each semi-coaxial resonator. The resonance rod 2 forms an inner conductor of the semi-coaxial resonator. A frequency adjusting screw 3 is provided on the metal housing 1 facing the other end of each resonance rod 2. A coupling adjusting screw 5 is provided between the semi-coaxial resonators to change the coupling between the resonators to adjust the bandwidth. The semi-coaxial resonator filter and the external transmission line are electric-field-coupled by an input / output coupling probe 6.

FIG. 2 is a partial sectional view showing a detailed configuration of the semi-coaxial resonator shown in FIG. As shown in the figure, the resonance rod 2 is composed of two types of components 2a and 2b. The components 2a and 2b are selected so that the linear expansion coefficients are different.
Brass is often used for the metal casing 1 because of its ease of cutting and silver plating. The frequency adjusting screw 3 is also made of silver-plated brass for the same reason. Therefore, one of the components 2a and 2b is also made of brass. The other material of the components 2a and 2b is preferably, for example, Invar, which has a small coefficient of linear expansion and a coefficient of linear expansion which is largely different from the coefficient of linear expansion of brass. If the two materials are far apart, the linear expansion coefficient of the entire inner conductor can be adjusted in a wide range. The linear expansion coefficient of brass is about 20 ppm / ° C, and the linear expansion coefficient of Invar is about 2 ppm / ° C. Further, the component 2a may be made of brass and the component 2b may be made of invar, or vice versa.

Two types of parts 2a and 2b constituting the resonance rod 2
Is partially threaded so that the length L2 of the inner conductor and its ratio (L2a / L2b) can be easily adjusted. As shown in FIG. 2, L2a is the length of the component 2a, and L2b is the length of the component 2b. In FIG. 2, circles indicate the fitting parts by screws. Then, if the fastener (nut) 2e is loosened and the partially screw-shaped part 2b is turned, the length L2 of the inner conductor can be changed since the part 2a and the part 2b are connected. Further, if the fastener (nut) 2d is loosened and the partially screw-shaped part 2a is turned, the length of L2a can be changed. In FIG. 2, L1 indicates the length of the outer conductor, L3 indicates the insertion length of the frequency adjustment screw, and L4 indicates the gap length.

Hereinafter, a change in the resonance frequency due to a temperature change will be described. The change in the resonance frequency due to the temperature change is caused by the change ΔL2 in the length L2 of the inner conductor,
The change is based on the change ΔL4 in the gap length L4 between the resonance rod 2 and the facing surface.

In the semi-coaxial resonator, the length L2 of the inner conductor is about 1 /
It resonates at four wavelengths, but also changes depending on the capacitance formed between the open end of the inner conductor and the outer conductor. FIG. 3 is an explanatory diagram showing the relationship between the length L2 (mm) of the inner conductor and the resonance frequency F (MHz). FIG. 3 shows that resonance occurs at a length of about 0.75 times the quarter wavelength. The length L of the inner conductor
It can be seen that as 2 increases, the resonance frequency decreases. Note that the outer conductor diameter of the semi-coaxial resonator when measuring the resonance frequency is 27 mm, the inner conductor diameter is 7 mm, and the length L1 of the outer conductor is 2
3 mm. Also, of the three curves in FIG.
The upper curve shows the theoretical value of 0.8 × (1/4 wavelength),
The lower curve shows a theoretical value of 0.7 × (1/4 wavelength).

Since the resonance frequency is substantially inversely proportional to the length L2 of the inner conductor, the frequency change rate (ΔF / F) = − ΔL2
/ (L2 + ΔL2). ΔL2 is the length L2 of the inner conductor
ΔF / F ≒ −ΔL2 / L2 (inner conductor length change rate) (1)

Assuming that the linear expansion coefficient of the component 2a is αa and the linear expansion coefficient of the component 2b is αb, the linear expansion coefficient α of the inner conductor is α = (L2a × αa + L2b × αb) / L2 (2) It is. Therefore, the ratio of the lengths of the components 2a and 2b (L2a
/ L2b), the coefficient of linear expansion α can be freely changed within the range of each coefficient of linear expansion.
Further, by changing the linear expansion coefficient α, the inner conductor length change rate ΔL2 / L2 can be changed accordingly.

On the other hand, as can be seen from FIG. 7, when the frequency adjusting screw 3 is inserted, the frequency change ΔF changes little by little at first, and when the frequency adjusting screw insertion length L3 increases, that is, the gap length L4 Becomes smaller, the frequency change amount ΔF becomes larger. Also, as the gap length L4 increases, the resonance frequency increases.

When the temperature increases, the gap length L4 between the resonance rod 2 and the facing surface increases. This is because the length L2 of the inner conductor <the length of the outer conductor, the linear expansion coefficient α of the inner conductor <the linear expansion coefficient of the metal housing 1. Since the resonance frequency increases as the gap length L4 increases, the effect of ΔL4 acts to increase the resonance frequency as the temperature increases. On the other hand, the influence of ΔL2 acts to lower the resonance frequency because the length L2 of the inner conductor increases as the temperature increases.

From the above description, the frequency sensitivity ΔF / F (see FIG. 6) with respect to the gap length L4 at that time is equal to the frequency sensitivity shown by the equation (1) (the sign is reversed). If the inner conductor length change rate ΔL2 / L2 is set so as to satisfy the above condition, the resonance frequency does not change even if the temperature changes. That is, if the inner conductor length change rate ΔL2 / L2 is appropriately set, the effect of ΔL4 can be canceled by the effect of ΔL2 so that the resonance frequency does not change. As described above, the inner conductor length change rate ΔL2 / L2 is in accordance with the linear expansion coefficient α. Therefore, if the linear expansion coefficient α is appropriately set, the resonance frequency does not change even if the temperature changes.
Since the linear expansion coefficient α can be set according to the length ratio (L2a / L2b) of the components 2a and 2b,
The linear expansion coefficient α can be appropriately set by the adjustment mechanism shown in FIG.

In the embodiment shown in FIG. 2, the part 2b is joined so that a part of the part 2b is exposed on the outer periphery of the part 2a, and as an adjusting mechanism, the parts 2a and 2b are partially screwed to the parts 2a and 2b (FIG. 2). , And the nuts 2d and 2e are loosened to change the lengths of the parts 2a and 2b. Since the screw portion is partially provided, the parts 2a and 2
The change between b and b is small and the assembling is easy, but a configuration in which a thread portion is provided on the entire outer periphery of the component 2a may be used.

As described above, according to the present invention, the resonance rod 2 is constituted by two kinds of metal parts 2a and 2b having different linear expansion coefficients, and the lengths of the parts 2a and 2b inside the metal housing 1 are set. Is provided with an adjusting mechanism for changing the ratio (L2a / L2b), so that the resonance frequency of the semi-coaxial resonator does not change even when the temperature changes. In addition,
Since the above discussion can be applied to a band-pass filter using a plurality of semi-coaxial resonators, the center frequency can be prevented from changing even when the temperature changes. Also, when a band rejection filter or the like is formed,
The stop frequency and the like can be kept unchanged.

Further, in the band-pass filter using the semi-coaxial resonator, when the center frequency is largely changed by adjusting the frequency adjusting screw 3, the center frequency can be easily maintained. Since the gap length L4 changes by adjusting the frequency adjusting screw 3, the effect of ΔL4 differs from that before adjustment. However, by appropriately setting the length ratio (L2a / L2b) of the components 2a and 2b again, the frequency sensitivity Δ due to the gap length L4 after the center frequency is changed.
The frequency sensitivity expressed by the equation (1) can be made equal to F / F. That is, even if the center frequency is largely changed by adjusting the frequency adjusting screw 3, the center frequency after the change can be made not to be affected by the temperature change.

Further, the temperature characteristics can be set in accordance with the temperature characteristics of other elements such as a filter incorporated in the microwave device, so that the temperature characteristics of the entire device can be improved. For example, if another element has a characteristic that the center frequency rises as the temperature rises, a band-pass filter using a semi-coaxial resonator that inputs a signal from that element is added to the center frequency as the temperature rises. Is given, the effect of temperature change can be eliminated as a whole. In order for the center frequency to decrease as the temperature rises, the lengths of the components 2a and 2b are set such that the effect of ΔL2 acting in the direction of frequency decrease becomes greater than the effect of ΔL4 acting in the direction of frequency increase. What is necessary is just to set the ratio (L2a / L2b).

Further, the length ratio of the parts 2a and 2b (L2
If a / L2b) is set such that the effect of ΔL2 is smaller than the effect of ΔL4, the center frequency can also be increased with an increase in temperature. That is, according to the present invention, since the characteristics of the frequency change with respect to the temperature change can be freely set, it is possible to use the method for improving the characteristics of the entire microwave device according to the situation.

In the above embodiment, the resonance rod 2 is 2
It was composed of metals with different linear expansion coefficients.
It is also possible to use components having different types of linear expansion coefficients.

[0028]

As described above, according to the present invention, the semi-coaxial resonator and the semi-coaxial resonator filter have the inner conductor formed of a plurality of metals having different linear expansion coefficients. In addition, there is an effect that a frequency change due to a temperature change can be extremely reduced. Further, when the semi-coaxial resonator filter is used as a band-pass filter, even if the center frequency is largely changed, the frequency change due to the temperature change can be reduced. Further, the temperature characteristics can be freely set, and the temperature characteristics of the entire device can be improved in a device incorporating a semi-coaxial resonator or a semi-coaxial resonator filter.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semi-coaxial resonator filter according to the present invention.

FIG. 2 is a partial sectional view showing a detailed configuration of a semi-coaxial resonator according to the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a length of an inner conductor and a resonance frequency.

FIG. 4 is a cross-sectional view showing a conventional semi-coaxial resonator filter.

FIG. 5 is a sectional view showing a conventional semi-coaxial resonator.

FIG. 6 is an explanatory diagram showing a relationship between a gap length and a frequency sensitivity in a semi-coaxial resonator.

FIG. 7 is an explanatory diagram showing the relationship between the insertion length and gap length of the frequency adjustment screw and the amount of change in the resonance frequency.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal housing 2 resonance rod 3 frequency adjustment screw 4 gap 5 coupling adjustment screw 6 input / output coupling probe 7 coupling window

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[Procedure amendment]

[Submission date] April 2, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (6)

[Claims] 1. A semi-coaxial resonator in which a gap is formed between one end of an inner conductor and an outer conductor and a resonance frequency is changed by changing a length of the gap, wherein the inner conductor has a plurality of linear expansion coefficients different from each other. A semi-coaxial resonator formed of a metal. 2. The semi-coaxial resonator according to claim 1, further comprising an adjusting mechanism for changing a length inside each of the plurality of metal outer conductors. 3. The method according to claim 2, wherein another metal is screwed to a part of an outer periphery of one of the plurality of metals, and the other metal is screwed to an outer conductor.
The described semi-coaxial resonator. 4. A semi-coaxial resonator in which a gap is formed between one end of the inner conductor and the outer conductor, and a plurality of semi-coaxial resonators that change the resonance frequency by changing the length of the gap are coupled via coupling means. In the filter, the inner conductor is formed of a plurality of metals having different linear expansion coefficients. 5. The semi-coaxial resonator filter according to claim 4, further comprising an adjusting mechanism for changing a length inside each of the plurality of metal outer conductors. 6. The other metal is screwed to a part of the outer periphery of one of the plurality of metals, and the other metal is screwed to an outer conductor.
A semi-coaxial resonator filter as described.