JPH0472803A - Tem mode resonator - Google Patents

Abstract

PURPOSE:To make the resonator small by employing two kinds of dielectric bodies as dielectric bodies forming the TEM mode resonator, using a 1st dielectric material whose temperature coefficient is positive for one of them and using a 2nd dielectric material whose temperature coefficient is negative for the other. CONSTITUTION:Two kinds of dielectric bodies 4, 5 are used for dielectric bodies forming the TEM mode resonator 3 and the one body 4 is made of a 1st dielectric material whose temperature coefficient is positive and the other body 5 is made of a 2nd dielectric material whose temperature coefficient is negative. Thus, even when the respective dielectric constant is increased and the temperature coefficient gets large, the entire temperature coefficient is decreased. Thus, dielectric materials with a high dielectric constant are used and the resonator is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to miniaturization of a resonator using a TEM mode line.

(Prior Art) In recent years, with the development and miniaturization of high frequency devices such as car phones and mobile phones, electronic components used in these devices are also required to be smaller. As an example, a 174-wavelength resonator with one end of the TEM mode line short-circuited, such as a coaxial resonator,
Filters that use a 1/2 wavelength resonator with both ends open are also required to be made smaller.

As an example of a method for miniaturizing a TEM mode resonator, a method of increasing the dielectric constant of the dielectric material is known because the larger the dielectric constant of the dielectric material used in the TEM mode resonator, the shorter the resonator can be.

(Problems to be Solved by the Invention) However, the dielectric materials currently used for filters have the largest dielectric constant of about 90, and there is a limit to their miniaturization. There are materials with a higher dielectric constant than this, but if the dielectric constant exceeds 100, the temperature coefficient of the resonant frequency of the resonator becomes large and exceeds the allowable range of the filter's temperature coefficient, so they cannot be used. There wasn't.

In addition to the above-mentioned coaxial line, there are TEM mode resonators that use strip lines and microstrip lines, but miniaturization is still constrained by the permittivity of the dielectric material. Similarly, there were limits to miniaturization.

An object of the present invention is to solve the above-mentioned problems and provide a structure of a TEM mode resonator that can be downsized.

(Means for Solving the Problems) A TEM mode resonator of the present invention includes a resonant electrode and a ground conductor with a dielectric material interposed therebetween, in which the temperature coefficient of the resonant frequency of the dielectric material is positive. TEM lines each made of a first dielectric material and a second dielectric material whose temperature coefficient of resonant frequency is negative are connected.

(Function) In the above-described configuration, two types of dielectrics are used as dielectrics constituting the TEM mode resonator, one of which is made of the first dielectric material whose temperature coefficient is positive, and the other is made of the first dielectric material whose temperature coefficient is positive. By configuring the dielectric material from a second dielectric material whose temperature coefficient is negative, even if the temperature coefficient of each component is increased by increasing the dielectric constant, the temperature coefficient as a whole can be reduced, achieving miniaturization. I can do it.

In order to reduce the temperature coefficient of the resonator as a whole, the magnitude of the actance when viewed from the junction surface of the first TEM line using the above two types of dielectric materials must be
The characteristic impedance and electrical length of each TEM line are set so that even when the temperature changes, the actance remains 0.5 times or more and 1.5 times or less than the actance when viewed from the junction surface of the second TEM line. Then it is preferable.

(Example) FIG. 1 is a perspective view and a sectional view showing the structure of a coaxial line as an example of a TEM mode resonator of the present invention.

In the embodiment shown in FIG. 1, in a TEM mode resonator 3 consisting of a resonant electrode 1 and a ground conductor 2 with a dielectric interposed therebetween, the dielectric is replaced with a first dielectric 4 whose temperature coefficient of resonance frequency has a positive gradient. and a second dielectric material 5 whose temperature coefficient of resonance frequency has a negative slope,
The temperature coefficient of the entire resonator 3 is reduced.

As mentioned above, the dielectric constant limit occurs because the temperature coefficient becomes too large. If a large temperature coefficient is acceptable, the dielectric constant can be made larger. Even if the temperature coefficient of the dielectric material used is large, the temperature coefficient of the filter of the present invention can be reduced by canceling each other out because dielectrics with different signs are used simultaneously in the same filter structure.

Therefore, the practical temperature coefficient of the filter is smaller, and a dielectric material with a larger dielectric constant can be used.

As mentioned above, in order to make the temperature coefficient around Oppm/'C using two types of dielectric materials with different signs of temperature coefficients, the temperature coefficient of the characteristic impedance of the TEM mode line and the resonant frequency of the dielectric substrate must be adjusted. It is necessary to take this into consideration when designing.

FIG. 2 shows an equinodal circuit in which the present invention is applied to a 174-wavelength resonator with one end short-circuited. In Figure 2, ZOi, τ
fi, θi (i・1, 2) are T using each dielectric material.
These are the characteristic impedance of the EM line, the temperature coefficient of the resonant frequency, and the electrical length. Moreover, X i (i·1, 2) is the actance of each TEM line viewed from the bonding surface. The resonance condition is that the reactances of Xl and X2 cancel each other out. The temperature coefficient of the resonant frequency in the case of a single TEM line is caused only by the change in electrical length due to temperature, but in the case of a structure like the present invention, changes in the actance of each line viewed from the junction surface must be taken into account. Must be.

Taking Figure 2 as an example, if the temperature coefficient of the dielectric material of the TEM line on the short-circuited end side is designed to be positive and the temperature coefficient on the open end side is negative, the absolute value of the actance of each TEM line will change as the temperature rises. is small and has a different sign, so changes due to temperature can be canceled out and the temperature coefficient of the resonator can be reduced. Conversely, if the temperature coefficient on the open end side is made negative and the temperature coefficient on the shorted end side is made positive, the absolute value of each TEM line's reactance will increase as the temperature increases, and the changes in reactance will be different from each other. The temperature coefficient of the resonator is also improved in this case.

Changes in the actance seen from the junction surface of each TEM line due to temperature are caused by thermal expansion of the dielectric material and changes in permittivity due to temperature, but dielectric materials with a large temperature coefficient of resonance frequency are particularly susceptible to temperature change in permittivity. has been greatly influenced by Since the characteristic impedance of a TEM line is inversely proportional to the square root of the permittivity of the dielectric material used, Oppm/'
To obtain C, it is also necessary to consider changes in characteristic impedance due to changes in dielectric constant.

In Figure 2, if the line is lossless, the reactance on the short-circuit side is ZO1tanθl, the reactance on the open end side is -ZO2cotθ2, and ZO at the resonant frequency.
The relationship 1ta'nθ1=ZO2cotθ2 is satisfied. In addition, in order to keep the resonant frequency unchanged even when the temperature changes, the characteristic impedance when the temperature changes is ZO1', the electrical length is θi', and Z01' tan
It is necessary to set θ1′ −ZO2′ cot θ2′.

This condition is for making the temperature characteristic of the resonator Oppm/'C, but in order to effectively improve the temperature coefficient, Z01'tanθ1' - aZO2' cot
The characteristic impedance and electrical length of each line are set for each TEM so that 0.5≦α≦1.5 is satisfied when θ2′
It is preferable to design using the temperature coefficient of the dielectric material used for the line, because it can further improve the temperature coefficient.

Figure 3 (a), (b), Figure 4 and Figure 5 (a),
(b) is a diagram showing the configuration of another example of the resonator of the present invention. FIGS. 3(a) and 3(b) are perspective views showing a structure in which the present invention is applied to a symmetrical strip line, and its A-
It is a sectional view along the A' line. In this embodiment, a first dielectric 4 and a second dielectric 5 are used, similar to the example shown in FIG.
A material with a different sign of the temperature coefficient of the resonant frequency is used. The difference from the embodiment shown in FIG. This point is that the thickness is made thicker than the thickness of the dielectric material 4.

Figure 4 shows a resonant conductor 11 forming a microstrip line.
, is a perspective view showing the structure of an example of a resonator in which an input capacitor 12 and an output capacitor 13 are provided on the surface.

In this embodiment as well, like the example shown in FIG. 1, the first dielectric 4 and the second dielectric 5 are made of materials with different signs of temperature coefficients of the resonance frequency. The difference from the embodiment shown in FIG. This point is made wider than the width of the conductor 11 for use.

FIGS. 5(a) and 5(b) are perspective views showing the configuration of an example in which a microstrip line is formed by the first dielectric 4 and a symmetrical strip line is formed by the second dielectric 5, and its A-A FIG. The present invention can be constructed by combining different line structures as in this embodiment.

An actual example will be explained below.

Example dielectric constant is 250 and temperature coefficient of resonance frequency is 1200pp
The first dielectric material is a material having a composition of SrTiO3 with m10C added with MnO, and PbZr with a dielectric constant of 140 and a temperature coefficient of resonance frequency of 11000 ppm/'C.
A material with a composition of O3 added with a rare earth metal oxide is used as the second dielectric material, and the reactance of the first TEM line at 75°C is equal to the reactance of the second TEM line. /4 wavelength coaxial resonator was fabricated.

In order to set each TEM line to the designed value, the diameter of the resonant electrode 1 in FIG. 1 was kept constant and the diameter of the ground conductor 2 was changed.

The TEM line made of the first dielectric material has a characteristic impedance of 5.9 ohms and an electrical length of 65 degrees on the short-circuit end side, and the TEM line made of the second dielectric material has a characteristic impedance of 5 ohms and an electrical length of 22 degrees. When the temperature coefficient of the resonator was set to 4 ppm/'C, a temperature coefficient of 4 ppm/'C was obtained.

Comparative example The dielectric constant is 250 and the temperature coefficient of resonance frequency is 1200pp.
The first dielectric material is a material with a composition of SrTiO3 with m10C added with MnO, and PbZr0 with a dielectric constant of 140 and a temperature coefficient of resonance frequency of 11000 ppm/°C.
．． A coaxial resonator was fabricated using a material containing a rare earth metal oxide as the second dielectric material so that the actance of the first TEM line was twice that of the first TEM line at 75°C. As a result, the temperature coefficient of the resonator was 410 ppm/°C.

(Effect of the invention) As is clear from the above, according to the present invention, the TE
Two types of dielectrics are used as dielectrics constituting the M-mode resonator, one of which is made of a first dielectric material whose temperature coefficient is positive, and the other which is made of a first dielectric material whose temperature coefficient is negative. By being constructed from a second dielectric material,
Even if the temperature coefficient of each element is increased by increasing the dielectric constant, the temperature coefficient as a whole can be lowered, allowing the use of dielectric materials with high dielectric constants, and making it possible to miniaturize the resonator. .

[Brief explanation of drawings]

Fig. 1 is a perspective view and longitudinal cross-sectional view showing the configuration of a coaxial line as an example of the TEM mode resonator of the present invention, and Fig. 2 is an example of the present invention applied to a quarter wavelength resonator with one end short-circuited. 3(a) and 3(b) are perspective views and sectional views taken along the line A-A', and FIG. 4 is a diagram showing the present invention applied to a symmetric strip line. Figures 5(a) and 5(b) are perspective views showing an example of applying the present invention to a microstrip line. FIG. ■... Resonant electrode 2... Ground conductor 3...
TEM mode resonator 4...First dielectric 5...Second dielectric 11...Resonance conductor 12...Input capacitor 13...Output capacitor Fig. 3(a) b)

Claims (1)

[Claims] 1. In a TEM mode resonator in which a resonant electrode and a ground conductor are provided with a dielectric material in between, the first dielectric material has a positive temperature coefficient of the resonant frequency of the dielectric material, and the first dielectric material has a positive temperature coefficient of the resonant frequency of the dielectric material. A TE characterized in that each TEM line is connected to a negative second dielectric.
M-mode resonator.