JPS6142882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resonator used in a high frequency band.

Planar resonators forming a resonant circuit on a dielectric substrate include microstrip lines, suspended lines, slot lines, and coplanar lines.

FIG. 1 shows an example of the configuration of a resonant circuit in a suspended line structure. FIG. 1 shows a linear resonator with both ends open. 1 is a coupling portion, 2 is a resonant circuit, and the length thereof is designed to be half or a quarter of the resonant wavelength. 3 is a dielectric substrate.

FIG. 2 is a diagram showing a state in which this dielectric substrate is held in a casing. A resonant circuit pattern 24 is formed on the dielectric substrate 21 . This is held and fixed in a metal casing 22 on a support stand 23. That is, it has a suspended line structure.

Now, in order to stabilize the temperature of a resonator in a high frequency band, many methods are used, for example, to use metals with different coefficients of linear expansion in coaxial or waveguide resonators. This method is difficult to apply to resonators such as resonators of suspended lines.

In view of the above-mentioned drawbacks of the prior art, the present invention provides a 1/2 wavelength open-ended resonator having a suspended line structure, with the thickness of the substrate, the distance between the substrate and the grounded casing, and the height of the casing. By creating a specific relationship between the dielectric constant and the temperature coefficient of the dielectric constant, by using a polyethylene fluoride member with a negative temperature coefficient of dielectric constant as the substrate, it is possible to The objective is to provide a resonator with good temperature characteristics without combining dielectric materials with different coefficients.

An embodiment will be described below with reference to the drawings.

First, the basic concept of the present invention will be explained.
In the figure, the support height of the board Δh = ₀ (this corresponds to a shielded microstrip line)
If the height is gradually increased from , as a resonator,
At first, the contribution of the dielectric constant of the dielectric is large, and the contribution gradually becomes smaller. That is, as Δh increases, the equivalent dielectric constant decreases.

If we look at this in terms of temperature change in the resonator, Δ
When h is small, the dependence of the dielectric constant on temperature changes is large, and when Δh is large, the coefficient of linear expansion of the metal conductor becomes more effective. That is, the resonant frequency of the resonator is given by the effective permittivity ε _r and the resonant circuit length l. is given by In order to make this temperature change zero, with K as a constant, df/dT=K(df/dε _r・dε _r /dT+df
/dl・dl/dT)=0...(2) It is necessary to do so.

Now, if the coefficient of linear expansion of the metal conductor is α and the temperature coefficient of the effective dielectric constant is β, temperature compensation is possible by approximating β≒2α from equation (2) (3).

That is, in the case of a dielectric material having a negative temperature coefficient of permittivity, temperature compensation of the resonator is possible without adding any other material in the substrate support method shown in FIG.

Furthermore, in the case of the present invention, a polyfluorinated ethylene member is used as the dielectric substrate. When this polyfluorinated ethylene fiberglass is used, as shown in Figure 2, the thickness of the dielectric substrate: h ₀ , the distance between the substrate and the lower surface of the casing (ground plane): Δh, and the height of the casing. If the distance between h ₀ :Δh:H=0.5 and 1.2:1.7:10 is selected, temperature compensation of the resonator can be performed sufficiently effectively. In this case, the conductor width W of the resonant circuit has almost no effect and can be ignored.

Examples are shown below. Figure 3 shows a circuit with a resonant circuit length of 170 mm and a width of 4 mm using a polyethylene fluoride glass resin substrate with a thickness of 0.8 mm as a dielectric substrate and supported within a 10 mm height inside the housing. The temperature coefficient of the resonance frequency is shown using the substrate height Δh as a variable.

In this example, it can be seen that if Δh=1.7 mm, a highly stable oscillator can be obtained.

When Δh is smaller than this, from equation (1), the change in resonance frequency has a large effect of ε _r and has a positive coefficient.

In reality, we were able to obtain stability of less than +10 ppm/°C at Δh=1.7 mm. Alternatively, a polyethylene fluoride board can be used as the dielectric substrate. Further, the change in the conductor width W of the resonant circuit is very small compared to the change in length, so there are few problems.

In this manner, the present invention provides a method for holding a dielectric substrate on which a circuit is configured in a case in a planar circuit resonator without adding any new temperature-compensating capacitors, dielectrics, or other material components. By using only the method described above and the material of the dielectric substrate, a resonator with an extremely simple structure and good frequency stability can be obtained.

If such a resonator structure is used and an oscillator is constructed by connecting an in-body oscillation element (a Gunn diode or an impact diode) and a transistor, the stability of the resonant circuit system will be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of the configuration of a resonant circuit in a suspended line structure, Fig. 2 is a cross-sectional view of a resonator in an embodiment of the present invention, and Fig. 3 is a temperature change depending on the substrate holding height (Δh). FIG. 3 is a diagram showing changes in coefficients. 21...Dielectric substrate, 22...Metal casing, 23
...Support stand.

Claims (1)

[Claims] 1. In a 1/2 wavelength open-ended resonator with a suspended line structure, the distance between the substrate thickness h ₀ , the distance Δh between the substrate and the grounded casing, and the height H of the casing h ₀ : Δh: 1. A resonator characterized in that the resonator is constructed so that the relationship of H=0.5 to 1.2:1.7:10 holds, and that a polyfluorinated ethylene member having a negative temperature coefficient of dielectric constant is used as the substrate.