JPH01144802A - Dielectric band elimination filter - Google Patents

Abstract

PURPOSE:To facilitate the adjustment of a band elimination characteristic by constituting the lower part of a box being a ground electric conductor directly under a strip line connected to an dielectric oscillator with the connection adjusting screw of l/2 diameter. CONSTITUTION:In case that the connection adjusting screw 5 is screwed so as to be stuck to a dielectric substrate 3, it is made to be the constitution of a microstrip line that the ground electric conductor is provided on the whole reverse side of the substrate 3. Then, when the screw 5 is gradually pulled out, the action of the ground electric conductor is gradually made to be low, the characteristic impedance of the strip line 2 is gradually made to be high and band width is gradually made to be narrow. Besides, according as the ground electric conductor for the strip line 2 is eliminated by the screw 5, the length of the screw 5 is made to be lambda/2. Thus, in the state of holding input/ output impedance matching the characteristic of the band elimination filter can be adjusted.

Description

[Detailed Description of the Invention] [Summary] Regarding a dielectric band-rejection filter that combines a dielectric resonator and a strip line, the present invention relates to a dielectric band-rejection filter that combines a dielectric resonator and a strip line. In a dielectric band-rejection filter in which a strip line is formed on a dielectric substrate and the dielectric substrate is fixed to a housing, the above-mentioned strip line becomes a ground conductor directly below the strip line coupled to the dielectric resonator. The bottom of the casing was configured with a coupling adjustment screw having a diameter of λ/2.

[Industrial application field]

The present invention relates to a dielectric band-rejection filter that combines a dielectric resonator and a strip line.

Dielectric band rejection filter for microwave band is ”
It combines a dielectric resonator and a strip line to attenuate a desired band, and has the advantage of being miniaturized. In such a dielectric band rejection filter, several tens of
It is desired that desired characteristics can be easily obtained even for use in the GHz band.

[Conventional technology]

FIG. 10 is a partially cutaway perspective view of a conventional example, in which T2O1δ
A mode dielectric resonator 51 is supported at the bottom of the casing 55 by a low-loss support 52, a dielectric substrate 53 with a strip line 54 provided on the surface is provided at the bottom of the casing 55, and a dielectric substrate 53 is provided on both sides of the casing 55. The center conductor of the provided coaxial connector 56 is connected to the strip line 54, a frequency adjustment screw 58 is provided on the top cover 57, and the dielectric resonator 51 and the strip line 5 are connected to each other.
By magnetically coupling with 4, a dielectric band-rejection filter is constructed.

In such a conventional dielectric band rejection filter,
When the frequency adjustment screw 58 is screwed in to shorten the distance from the dielectric resonator 51, the resonant frequency becomes higher. However, resonance of the frequency adjustment screw 58 itself appeared, making it difficult to adjust the frequency over a wide band.

Therefore, a dielectric band rejection filter as shown in FIG. 11 was proposed. In the figure, 61 is a dielectric resonator;
2 is a support body, 63 is a dielectric substrate, 64 is a strip line, 65 is a housing bottom plate, 66 is a housing, 67 is a screw hole, 68
is the frequency adjustment screw. Note that the coaxial connector is not shown.

A dielectric substrate 6 is connected to a dielectric resonator 61 in TE, δ mode.
The configuration in which the strip lines 64 on 3 are combined and the band corresponding to the resonant frequency of the dielectric resonator 61 is removed is the same as the conventional example shown in FIG.
8 is made larger in diameter to prevent resonance of the frequency adjustment screw 68 in a band near the resonant frequency of the dielectric resonator 61.

[Problem that the invention seeks to solve]

In the conventional example shown in FIG. 10 described above, the problem of resonance of the frequency adjustment screw 58 occurred, making it difficult to widen the frequency adjustment range. Furthermore, by changing the coupling between the dielectric resonator 51 and the strip line 54, the bandwidth of the band-rejection filter can be changed. In that case, the distance between the dielectric resonator 51 and the strip line 54 must It needs to change. However, in a frequency band of 10 GHz or more, even a slight difference in the distance between the dielectric resonator 51 and the strip line 54 results in a large difference in the bandwidth, and ultimately fine adjustment of the distance is required. This has the disadvantage of complicating the configuration.

In addition, in the conventional example shown in FIG. 11 mentioned above, the problem of resonance caused by the frequency adjustment screw 68 is solved and the frequency adjustment range can be widened, but when the resonance frequency is adjusted to be high, , the no-load Q will decrease,
A drawback arises in that it is difficult to obtain a desired amount of attenuation. Furthermore, if the frequency is greatly changed, the degree of coupling between the dielectric resonator 61 and the strip line 64 also changes, and the bandwidth changes. It became necessary to adjust the distance, and 10G
In a frequency band of Hz or higher, a means for finely adjusting the distance is required, which has the disadvantage of complicating the configuration.

An object of the present invention is to facilitate adjustment of band rejection characteristics.

[Means for solving problems]

The dielectric band-rejection filter of the present invention adjusts the degree of coupling by adjusting the ground conductor side of the strip line coupled to the dielectric resonator, and will be described with reference to FIG.

In a dielectric band-rejection filter in which a strip line 2 coupled with a dielectric resonator 1 is formed on a dielectric substrate 3, and this dielectric substrate 3 is fixed to a housing 4, the dielectric resonator 1
A coupling adjustment screw 5 with a diameter of λ/2 (λ = wavelength) is attached to the bottom of the housing 4, which serves as a ground conductor directly below the strip line 2 to be coupled to the coaxial A case is shown in which the connectors 6, 7 are provided on both sides of the housing 4, and the frequency adjustment screw 8 is provided on the upper part of the housing 4.

[Effect]

When the coupling adjustment screws 5 are screwed in tightly to the dielectric substrate 3, a microstrip line is formed with a ground conductor provided on the entire back surface of the dielectric substrate 3, and the coupling adjustment screws 5 are gradually pulled out. As time goes on, the effect of the ground conductor gradually decreases, the characteristic impedance of the strip line 2 gradually increases, and the bandwidth gradually becomes narrower.

Also, this corresponds to removing the ground conductor for the strip line 2 using the coupling adjustment screw 5, but its length is set to λ/2.
By doing so, the characteristics of the band-rejection filter can be adjusted while maintaining input/output impedance matching.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is an exploded perspective view of an embodiment of the present invention, in which a strip line 14 is formed on a dielectric substrate 13, and a strip line 14 is formed on the dielectric substrate 13.
- A dielectric resonator 11 made of a BaO-based dielectric is supported by a low-loss support 12 such as quartz. The dielectric substrate 13 is also made of a low-loss dielectric, and is made of, for example, a material whose main base materials are glass cloth and tetrafluoroethylene resin.

In the bottom part 15 of the casing on which this dielectric substrate 13 is placed and fixed, recesses are formed to support the protrusions on the four sides of the dielectric substrate 13, screw holes 17 are formed in the four corners, and λ Screw hole 16 with a diameter of /2 (λ = wavelength, more precisely, the value obtained by multiplying the wavelength of the resonant frequency by the wavelength shortening rate in the strip line)
form.

Through this screw hole 16, the ground conductor for the strip line 14 is removed over a length of λ/2, and if a dielectric substrate 13 having a ground conductor is used, the size corresponding to the screw hole 16 is The ground conductor at the bottom is removed in advance.

The coupling adjustment screw 21 is screwed into a threaded hole 16 having a diameter of λ/2 in the bottom portion 15 of the casing, and is used to adjust the degree of coupling in accordance with the distance from the dielectric substrate 13.

In addition, a screw hole 19 is formed in the center of the upper part 18 of the case to be fixed on the bottom part 15 of the case, and holes 2 through which screws 23 pass are formed in the four corners.
form 0. Then, the upper casing 18 and the bottom 15 of the casing are fixed with the screws 23 with the dielectric substrate 13 interposed therebetween.

In addition, the bottom part 15 of the case, the top part 18 of the case, and the coupling adjustment screw 21
The frequency adjustment screw 22 is made of brass or the like, and the inside is plated with silver to reduce loss.

Similarly to the coupling adjustment screw 21, the frequency adjustment screw 22 has a relatively large diameter, and is screwed into the screw hole 19 in the upper part 15 of the casing to adjust the distance between it and the dielectric resonator 11 to adjust the resonant frequency. It is something.

Note that a coaxial connector for connecting the center conductor to the strip line 14 is not shown.

As the frequency adjustment screw 22 is screwed in so that the distance from the dielectric resonator 11 becomes shorter, the resonant frequency becomes higher. This frequency adjustment screw 22 is selected to have a diameter that does not cause resonance in the vicinity of the adjustment range of the resonant frequency of the dielectric resonator 11 even when it is protruded into the housing. Further, as the coupling adjustment screw 21 is screwed in closer to the dielectric substrate 13, the characteristic impedance of the strip line 14 becomes lower, and the bandwidth of the removal band can be widened.

As shown in Figure 3, thickness d = 0.8 mm, dielectric constant 2
．． A strip line 32 with a width W = 2 mm is formed on the dielectric substrate 31 of No. 6 and placed inside the casing 33, and the distance between the top of the casing 33 and the dielectric substrate 31 is 5 mm, and the bottom of the casing and the dielectric When the distance t from the body substrate 31 was changed, the characteristic impedance of the strip line 32 changed as shown in FIG. Note that the characteristic impedance when 1=0 is 50Ω.

In this way, when the distance t between the bottom of the housing 33 and the dielectric substrate 31 is 1 mm, the characteristic impedance is twice as high as 10
It became 0Ω, and when it was set to 4mm, it became about 132Ω. That is, when the coupling adjustment screw 21 is screwed in closely to the back surface of the dielectric substrate vi13, this corresponds to the case where t=Q, and as it is pulled out, the above-mentioned unevenness increases. The characteristic impedance of line 14 increases.

Figure 5 is a passing characteristic curve diagram, in which the center frequency is 11 G
Hz and a high-frequency rejection filter with a 3dB bandwidth of 50MHz, the characteristic impedance of the stripline is 4.
Passage characteristics in the case of 0Ω, 50Ω, and 60Ω are shown by a solid line curve a, a chain line curve b, and a dotted line curve C, respectively. That is, the smaller the characteristic impedance, the larger the amount of passing attenuation at the center frequency, and the wider the bandwidth.

As described above, when the coupling adjustment screw 21 that serves as a ground conductor for the strip line 14 is extracted, the characteristic impedance of the strip line 14 increases. In this case, in order to realize a characteristic impedance of 50Ω used in a typical microwave circuit, it is necessary to make the width of the strip line 14 wider than when a ground conductor is present. For example, as shown in FIG. 6, if only a portion 37 of the ground conductor 36 for the strip line 34 formed on the dielectric substrate 35 is removed, the characteristic impedance of the strip line 34 corresponding to the removed portion 37 becomes high. However, by widening the width as shown in the figure, the characteristic impedance can be made similar to that of the microstrip line portion where the ground conductor 36 is present. That is, by increasing the width of the suspended strip 7-pline, it is possible to achieve the same characteristic impedance as the microstrip line.

However, if the removed portion 37 of the ground conductor 36 is formed in advance, the characteristic impedance can be set to 50Ω by selecting the width of the strip line 34. Sometimes,
Since the characteristic impedance changes, selection of the width of the strip line 34 cannot cope with this change. Therefore,
If the ground conductor 36 is removed over the λ/2 length of the strip line 34, the input/output impedance of the strip line 34 should be approximately 50Ω near the center frequency, regardless of whether the ground conductor 36 is removed. Can be done.

For this reason, the diameter of the coupling adjustment screw 21 is set to λ/
2, and the ground conductor for the strip line 14 is λ/
The spacing is adjusted over the length of the strip line 14, so that even if the characteristic impedance of the strip line 14 changes, input/output impedance matching can be maintained.

Figure 7 is a return loss characteristic curve diagram, with the center frequency set to 1
iCyHz, and the length facing the coupling adjustment screw 21 is λ/
The impedance of the strip line 14 of No. 2 is taken as a parameter, and the impedance is 60.70,
Curves a and b for the case of 80, 90, and 100Ω
, c, d, and e to adjust the return loss from 10 GHz to 12 G.
It is shown over Hz.

That is, as the impedance of the length λ/2 of the strip line 14 is increased, the return loss at the center frequency becomes smaller and the bandwidth becomes narrower.

FIG. 8 shows that in the embodiment of the present invention, the characteristic impedance of the strip line 14 is set to 75Ω, and the center frequency is 11 GHz and the 3 dB bandwidth is 50 MHz.
The characteristic impedance of the strip line 14 is set to 65Ω and 85Ω using the coupling adjustment screw 21.
The amount of passing attenuation when adjusted to 10975
It was obtained from MHz to 11025 MHz. In the figure, curve a shows the case where the characteristic impedance of the strip line 14 is set to 75Ω, curve A shows the case where the characteristic impedance of the strip line 14 is set to 65Ω, which is lower than that, and curve C shows the case where the characteristic impedance is set to 85Ω, which is higher than that.

Also, Figure 9 shows the frequency range of 10GHz to 12GHz under the above conditions.
It shows the return loss characteristics in the frequency range of z, and the curve a''-c corresponds to the aforementioned curve a x c. That is, when the coupling adjustment screw 21 is adjusted 8 times so as to be close to the strip line 14, , the characteristic impedance of the stripline 14 becomes smaller and the bandwidth becomes wider. Conversely, when the coupling adjustment screw 21 is adjusted away from the stripline 14, the characteristic impedance of the stripline 14 becomes larger and the bandwidth becomes wider. It gets narrower.

Although the width of the strip line 14 is shown in FIG. 2 or 6 as being wide over the length of λ/2, it may also be the same width as the strip line of the input/output section. Of course it is possible.

〔Effect of the invention〕

As explained above, the present invention provides a housing 4 that serves as a ground conductor directly below the strip line 2 coupled to the dielectric resonator 1.
A coupling adjustment screw 5 with a diameter of λ/2 is provided at the bottom of the dielectric resonator 1, and the bandwidth can be adjusted by adjusting the degree of coupling between the dielectric resonator 1 and the strip line 2. , there is an advantage that the deviation in the degree of coupling due to the distance between the dielectric resonator 1 and the strip line 2 can be easily adjusted. Furthermore, when combined with frequency adjustment, there is an advantage that adjustment can be made to absorb changes in the degree of coupling due to frequency adjustment over a wide band.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an exploded perspective view of an embodiment of the invention, Fig. 3 is a sectional view of a strip line, Fig. 4 is a curve diagram of the characteristic impedance of the strip line, and Fig. 5 is a diagram illustrating the characteristic impedance of the strip line. Figure 6 is an explanatory diagram of a strip line, Figure 7 is a diagram of the return loss characteristic curve, Figure 8 is a diagram of the transmission characteristic curve, Figure 9 is a diagram of the return loss characteristic curve, and Figure 10 is a diagram of the return loss characteristic curve.
The figure is a partially cutaway perspective view of a conventional example, and FIG. 11 is an exploded perspective view of the conventional example. 1 is a dielectric resonator, 2 is a strip line, 3 is a dielectric substrate, 4 is a housing, 5 is a coupling adjustment unit, 6.7 is a coaxial connector, 8 is a frequency adjustment unit, 11 is a dielectric resonator , 12
13 is a support body, 13 is a dielectric substrate, 14 is a strip line, 15 is a housing bottom, 16.17 is a punching hole, 18 is a housing top, 19 is a screw hole, 20 is a hole, and 21 is a coupling adjustment screw. ,2
2 is a frequency adjustment screw, and 23 is a screw.

Claims (1)

[Claims] A strip line (1) coupled with a dielectric resonator (1).
2) is formed on a dielectric substrate (3), and
) in a dielectric band-rejection filter fixed to a casing (4), the casing (4) serves as a ground conductor directly below the strip line (2) coupled to the dielectric resonator (1). A dielectric band-rejection filter characterized in that a coupling adjustment screw (5) with a diameter λ/2 (λ=wavelength) is provided at the bottom.