JPH09238002A - Microstrip filter and its center frequency adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the microstrip filter whose frequency is very easily adjusted and its center frequency adjustment method. SOLUTION: A dielectric tape 6 is sticked to the filter so as to cover a resonator 3 formed on the surface of a dielectric board 1 to adjust the center frequency of the filter. For example, the center frequency is quickly adjusted with a simple operation by sticking an optional number of the dielectric tapes 6 to the filter with respect to the deviation in the center frequency caused by dispersion in the dielectric constant of the dielectric board 1 so as to utilize it that the frequency is slowly shifted decreasingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip filter used in the field of microwave communication and the like, and more particularly to a microstrip filter capable of easily adjusting its filtering characteristic and its center frequency adjustment. Regarding the method.

[0002]

2. Description of the Related Art In microwave communication devices, high-density packaging,
In order to reduce the cost, a microwave circuit using a microstrip as a circuit pattern is constructed on a dielectric substrate, and a bandpass filter or a band stop filter is constructed by this microwave circuit. For example,
As shown in FIG. 3, the ground conductor 1 is formed on the back surface of the dielectric substrate 11.
2 is formed, the main conductor line 13 and the resonance line 14 are formed on the surface by a microstrip line, and these are installed inside the shield case 15.

By the way, in this type of filter, there is a problem that the center frequency of the filter is likely to deviate from the design value due to variations in the dielectric constant of the dielectric substrate 11. In order to adjust such a frequency shift, in the filter shown in FIG. 3, the electrical adjustment metal element 16 having a bolt structure is arranged so as to face a part of the resonance line 14, and the metal element 16 The frequency is adjusted by changing the protrusion amount. Alternatively, it is proposed that a frequency adjusting conductor pattern is provided on a part of the dielectric substrate and the frequency is adjusted by scraping the conductor pattern or connecting a conductor plate. .

[0004]

However, the provision of the above-mentioned electric adjustment metal element for frequency adjustment makes the structure of the filter complicated and tends to increase the cost, and such an adjustment structure has a shield case. This is effective when a filter is constructed in a case like that, and cannot be applied to a filter simply constructed on a dielectric substrate. Further, in the structure in which the conductor pattern is abraded or added, the frequency is likely to be greatly changed due to the minute area change of the conductor pattern, and the ablation or addition of the fine pattern is required to obtain the desired frequency Therefore, there is also a problem that the adjustment work takes a long time.

For this reason, conventionally, a plurality of filters are simultaneously formed using a plurality of dielectric substrates, and the filter having the frequency closest to the design value is selected and used. This is troublesome to manufacture the filter and is not preferable in terms of cost. It is also possible to deal with frequency deviation by designing the bandwidth of the filter wide, but it is often not possible to satisfy the desired characteristics, and the characteristics deteriorate due to increasing the number of filter stages. There is also a problem.

An object of the present invention is to provide a microstrip filter capable of extremely easily adjusting the frequency and a center frequency adjusting method thereof.

[0007]

According to the present invention, in a microstrip filter constituted by a microstrip line formed on the surface of a dielectric substrate, a dielectric tape is attached to the surface of the dielectric substrate. It is characterized by In particular, the present invention is characterized in that the dielectric tape is attached to the surface of the dielectric substrate, so that the center frequency of the dielectric tape is shifted to a lower frequency side than when the dielectric tape is not attached. And Also, in this case,
A plurality of dielectric tapes having the same size or different sizes, or the same film thickness or different film thicknesses may be laminated and attached to the dielectric tape.

Further, according to the present invention, in a microstrip filter composed of a microstrip line formed on the surface of a dielectric substrate, a dielectric tape is attached on the microstrip line to adjust the filter center frequency. It is characterized by performing.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view and a cross-sectional view of an embodiment in which the present invention is applied to a bandpass filter used in a micro communication device. Here, the bandpass filter is a three-stage filter having a parallel coupling line structure with a half-wave resonator. It is configured. A ground conductor 2 is formed on the back surface of the dielectric substrate 1, and a half-wave resonator 3 having a three-stage structure is formed on the surface thereof by a microstrip line. And
An input pattern portion 4 and an output pattern portion 5 are formed on the input side and the output side of the half-wave resonator 3 by microstrip lines connected to the microstrip line, respectively.

On the surface of the dielectric substrate 1, a dielectric tape 6 is attached to the area excluding the input pattern portion 4 and the output pattern portion 5. The dielectric tape 6 is formed of a thin dielectric film, and since the back surface of the dielectric tape 6 is coated with an adhesive, it can be attached to the front surface of the dielectric substrate 1 simply by pressing. Further, in this case, the dielectric tape 6 is formed of a transparent material so that the microstrip line of the half-wavelength resonator 3 hidden under the dielectric tape 6 can be transmitted. Further, a plurality of the dielectric tapes 6 can be laminated and adhered if necessary, and the example of FIG. 1 shows a state where two dielectric tapes 6 are laminated and adhered. In this case, the dielectric tapes 6 are formed to have the same size, but in some cases, different sizes may be laminated and attached.

According to the filter having this structure, the dielectric tape 6 is not attached when it is manufactured. And
When the center frequency of the filter deviates from the design value due to variations in the dielectric constant of the dielectric substrate 1 or the like,
As many dielectric tapes 6 as necessary are attached to the surface of the dielectric substrate 1. By applying this dielectric tape 6, the dielectric constant of the dielectric substrate 1 is changed, and the center frequency of the filter is changed accordingly. Therefore, the filter characteristics can be adjusted by attaching the dielectric tape 6 as needed.

FIG. 2 shows changes in the center frequency of the filter. In the figure, F1 is the case where no dielectric tape is attached, F2 is the case where one dielectric tape is attached, and F3 is the case where two dielectric tapes are attached. As can be seen from the figure, the center frequency of the filter is shifted to the lower side by attaching the dielectric tape. Therefore,
If you design the center frequency of the filter to a frequency higher than the desired frequency and make a filter in advance, you can shift the frequency to the lower side by attaching the dielectric tape,
As a result, it becomes possible to obtain a bandpass filter having a center frequency at a desired frequency.

Since the adjustment of the center frequency by attaching the dielectric tape 6 is a frequency change due to the adjustment of the dielectric constant, when the frequency adjustment is performed while the conductor pattern provided in a part of the microstrip line is deleted or added. The change in frequency becomes slower than that of, and therefore, it becomes easy to set the desired frequency. Further, by preparing dielectric tapes 6 of various standards having different thicknesses and dimensions and selecting these, it becomes possible to adjust the frequency in a state where the frequency changes more slowly, and the adjustment can be performed more easily. It becomes possible.

In the above embodiment, the periphery of the dielectric substrate 1 including the region forming the half-wave resonator 3 on the dielectric substrate 1, that is, the region of the input pattern portion 4 and the output pattern portion 5 of the microstrip line. Although the structure is such that the dielectric tape 6 is attached to a region other than the portion, the present invention is not limited to this, and a dielectric tape having an arbitrary pattern shape can be formed.

In the above embodiment, an example in which the present invention is applied to a bandpass filter is shown. However, the present invention can be applied to any bandstop filter or any other filter as long as the filter is constituted by a microstrip line. The same can be applied. Further, according to the present invention, even if the center frequency is deviated due to a cause other than the variation in the dielectric constant of the dielectric substrate, the frequency can be adjusted.

[0016]

As described above, according to the present invention, a dielectric tape is attached to the surface of a dielectric substrate to adjust the center frequency of the filter. Even if the center frequency is deviated, the frequency can be slowly shifted downward by attaching the dielectric tape.
Moreover, it becomes possible to make a quick adjustment.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of an embodiment in which the present invention is applied to a bandpass filter.

FIG. 2 is a diagram showing a change state of a center frequency in the bandpass filter of the present invention.

FIG. 3 is a plan view and a cross-sectional view of an example of a conventional microstrip filter.

[Explanation of symbols]

 1 Dielectric Substrate 2 Grounding Conductor 3 Half Wave Resonator (Microstrip Line) 4 Input Pattern Section 5 Output Pattern Section 6 Dielectric Tape

Claims (6)

[Claims] 1. A microstrip filter including a microstrip line formed on the surface of a dielectric substrate, wherein a dielectric tape is attached to the surface of the dielectric substrate. . 2. A microstrip filter including a microstrip line formed on the surface of a dielectric substrate, wherein a dielectric tape is attached to the surface of the dielectric substrate, and the center frequency of the dielectric tape is attached to the dielectric tape. A microstrip filter characterized in that it is shifted to a lower frequency side compared to when it is not. 3. The microstrip filter according to claim 1, wherein the dielectric tape is attached to a region covering the microstrip line. 4. The microstrip filter according to claim 1, wherein the dielectric tape is formed by laminating a plurality of dielectric tapes having the same size or different sizes, or the same film thickness or different film thicknesses. 5. The microstrip filter according to claim 1, wherein the bandpass filter is constituted by a microstrip line. 6. A microstrip filter including a microstrip line formed on the surface of a dielectric substrate, wherein a dielectric tape is attached to the microstrip line to adjust the filter center frequency. A method for adjusting the center frequency of a microstrip filter.