JP2001230602A - Variable filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem where it is difficult to change the central frequency of a passband, without disordering responsivity over a wide band even though there is a method for changing only a easily changeable partial element value, since it is necessary to make all element values variable, which comprise a variable filter, when changing the central frequency of the passband of the filter. SOLUTION: The filter is formed on a dielectric substrate, whose dielectric constant is changed by causing physical changes from the outside and by changing the dielectric constant so as to provide desired characteristics, a guide wavelength λg is changed. Since the passband is determined by the guide wavelength λg, and the central frequency of the passband can be changed arbitrarily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter used for a radio device.

[0002]

2. Description of the Related Art Conventionally, IEEE MTT-S Dig
est 1999, pp-1235-1238 are known. FIG. 7 shows a variable bandpass filter using the micro machine technology. The characteristics of the filter are determined by the inductors 82 and 83, the coupling degree M, and the capacitance values of the variable capacitors 85 to 88.

The variable capacitors 85 to 88 are parallel flat plates composed of minute cantilevers formed on a silicon substrate by a micro-machine technology.
9, 90 are applied, the other side is grounded, and an electrostatic force is applied between the two parallel flat plates.

The electrostatic force applied at this time is a DC voltage 89,
Since the distance varies depending on the value of 90, the interval between the parallel plates becomes variable. Since the capacitance value is determined by the interval between the two parallel plates, an arbitrary capacitance value can be obtained by changing the DC potentials 89 and 90. If the capacitance changes, the characteristics of the filter also change. FIG. 8 shows the characteristics of the filter when the DC voltages 89 and 90 are changed from 0V to 65V. Thus, the center frequency of the passband changes from 26.6 GHz to 25.5 GHz.

[0005]

However, since only the capacitance of the elements constituting the filter is changed, there is a limit in changing the center frequency of the pass band of the filter while maintaining the responsiveness of the filter. For this purpose, the inductor value and the coupling degree M must also be changed, but it is extremely difficult to change the inductor value and the coupling degree M using a micromachine technology. For this reason, it is difficult to change the center frequency of the filter while maintaining the frequency response over a wide frequency range. Further, in the above configuration in which only the capacitance value is changed, the pass bandwidth cannot be changed.

In the present invention, a filter is formed on a dielectric material whose permittivity can be changed arbitrarily, and the center frequency of the filter is maintained while changing the permittivity to change the guide wavelength λg while maintaining the frequency response of the filter. It is an object of the present invention to realize a variable filter that varies.

[0007]

A dielectric substrate formed of a dielectric material capable of arbitrarily changing a dielectric constant, a control mechanism for making a physical change to the dielectric substrate based on a control signal, It comprises a filter formed on a substrate and terminals for inputting and outputting signals to and from the filter.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides a method of manufacturing a semiconductor device, comprising: a dielectric substrate formed of a dielectric material whose dielectric constant can be arbitrarily changed; In a filter comprising a control mechanism for applying a change, a filter formed on the dielectric substrate, and a terminal for inputting / outputting a signal to / from the filter, a dielectric constant of the dielectric substrate is controlled by an external control signal. If the value is changed to a desired value based on the above equation, the guide wavelength λg can be changed, so that the center frequency f0 of the pass band can be changed while maintaining the responsiveness of the filter. According to an eighth aspect of the present invention, a plurality of variable filters according to the first aspect are arranged in series to form a filter array composed of filters having different responsiveness, and the frequency characteristic of each filter is independently adjusted. The control has the effect of making the center frequency of the pass band and the pass band width variable.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a configuration diagram of the present invention. FIG. 2 is a sectional view and a top view of the bandpass filter. In FIG. 1, reference numeral 11 denotes a bandpass filter having a triplate structure using a dielectric material.
Reference numerals 6 and 7 denote input / output terminals, 4 a voltage generating mechanism for generating a desired voltage based on a control signal, and 5 an applied voltage for applying an electric field to the dielectric material. Input terminal 6
Are passed through the band-pass filter 11 and output from the output terminal 7.

FIG. 2 shows a sectional view and a top view of eleven bandpass filters formed on the dielectric substrate 2. This is a generally known bandpass filter in which open-ended lines having a guide wavelength of λg / 4 are connected in multiple stages. At this time, the guide wavelength λg that determines the center frequency of the pass band of the filter
Is represented by (Equation 1) and depends on the dielectric constant εr. Therefore, if εr is changed, the center frequency of the pass band of the filter can be changed.

Further, since the constants of the individual elements constituting the filter are not changed as in the conventional example, the response does not change and the center frequency of the pass band changes. FIG. 3 shows the frequency characteristics of the filter when the permittivity is changed.

[0013]

(Equation 1)

Next, the dielectric constant of the dielectric can be arbitrarily changed.
Examples of the dielectric material include a ferroelectric liquid crystal material. This is a material whose dielectric constant changes according to the electric field,
FIG. 4 shows an example of the characteristic.

As described above, the dielectric constant can be changed from about 2 to about 9 according to the electric field. Therefore, in order to obtain a desired dielectric constant, the voltage generating mechanism 4 generates a predetermined electric field 5 based on the control signal 8 and changes the dielectric constant of the dielectric material 2. Therefore, since the guide wavelength λg changes, the center frequency of the pass band of the bandpass filter 11 can be changed. Reference numeral 11 does not need to have a triplate structure or a band-pass filter, but may be a filter formed on a dielectric material whose permittivity can be changed.

The variable filter may be formed on a liquid crystal panel used for a display unit or the like of a wireless communication device. (Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 5 shows a configuration diagram of the present invention. A plurality of variable filters 11 used in the first embodiment are arranged in series to form a filter array 20. The signal input from the input terminal 31 is output from the output terminal 32 via the first variable filter 21, the second variable filter 22, and the third variable filter 23.

Each variable filter has a control signal 24 to 2
6, the dielectric constant is changed to obtain a desired filter frequency characteristic. At this time, for example, if the first variable filter 21 is formed of a filter having a band-pass filter characteristic and the second filter 22 and the third filter 23 are formed of a filter having a notch filter characteristic, an arbitrary pass band width and a center frequency of the pass band can be set. The variable filter which has can be realized.

The pass band of the band-pass filter, which is the first variable filter, is a band-pass filter having the maximum value of the required band in advance, and the second and third variable filters 22, 23 are notch filters. Attenuation poles are provided on both sides of the pass band of the first variable filter to change the pass band. The second and third filters need not be notch filters, but may be low-pass filters or high-pass filters. FIG. 6 shows an example of the filter array characteristics. Also, the number of filters need not be three.

[0019]

As described above, according to the present invention, there is an advantageous effect that the center frequency and the pass bandwidth of the pass band of the filter can be varied over a wide band by changing the dielectric constant of the dielectric. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a variable filter according to an embodiment of the present invention.

FIG. 2 is a diagram showing a pattern example of a band-pass filter.

FIG. 3 is a diagram showing a variable filter characteristic;

FIG. 4 is a diagram showing a dielectric constant change characteristic of a dielectric material.

FIG. 5 is a configuration diagram schematically showing a variable filter according to a second embodiment of the present invention.

FIG. 6 is a view showing characteristics of a variable filter array.

FIG. 7 is a diagram showing a configuration of a conventional variable filter.

FIG. 8 is a diagram showing characteristics of a conventional variable filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Band pass filter pattern 2 Dielectric material 4 Voltage generating mechanism 6, 7 Input / output terminal 21, 22, 23 Variable filter 24, 25, 26 Control signal 31, 32 Input / output terminal

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Yabuki 3-10-1 Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa F-term in Matsushita Giken Co., Ltd. 5J006 HB04 HB12 JA06 LA11 MA00 MB02

Claims (13)

[Claims] 1. A dielectric substrate made of a dielectric material capable of arbitrarily changing a dielectric constant, a control mechanism for giving a physical change to the dielectric substrate based on a control signal, and a control mechanism formed on the dielectric substrate. In a filter composed of a filter pattern and terminals for inputting and outputting signals to and from the filter pattern, the filter is formed by changing a dielectric constant of a dielectric substrate to a desired value based on an external control signal. A variable filter, wherein the characteristic of the variable filter is variable. 2. The variable filter according to claim 1, wherein the dielectric material is a material whose dielectric constant changes by an externally applied electric field. 3. The variable filter according to claim 1, wherein the dielectric material is a ferroelectric liquid crystal material whose permittivity changes by an externally applied electric field. 4. The variable filter according to claim 1, wherein the variable filter uses a part of a liquid crystal panel used for a display unit or the like of a wireless communication device. 5. A wireless module using the variable filter according to claim 1. 6. A wireless device using the variable filter according to claim 1. 7. A wireless system using the variable filter according to claim 1. 8. A variable filter array, wherein a plurality of the variable filters according to claim 1 are arranged in series and controlled independently. 9. A variable filter constituting a variable filter array includes a band-pass filter and a notch filter, and the pass band width and the center frequency are changed by independently controlling each variable filter. The variable filter array according to claim 8. 10. A variable filter constituting a variable filter array is composed of a band-pass filter, a low-pass filter, and a high-pass filter, and the pass band width and the center frequency are changed by independently controlling each variable filter. 9. The variable filter array according to claim 8, wherein: 11. A wireless module using the variable filter according to claim 8. 12. A wireless device using the variable filter according to claim 8. 13. A wireless system using the variable filter according to claim 8.