JP2009177257A - Impedance variable element and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impedance variable element that prevents reflection of signal components generated by impedance mismatching. <P>SOLUTION: The impedance variable element includes a signal transmission line 11, a dielectric material 12 disposed in contact with the signal transmission line 11 varying in electric characteristics by voltage application, and a conductor 21 applying voltage to the dielectric material 12. The impedance can be varied by applying the voltage V<SB>B</SB>to the dielectric material 12 by the conductor 21 and the conductor 21 is electrically independent of the signal transmission line 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an impedance variable element that changes impedance with respect to a transmission line, and an electronic device including the impedance variable element.

  In recent years, a large number of digital signal standards exceeding 1 Gbps have been presented and installed in various devices.

However, in consumer devices, impedance discontinuities often exist on high-speed signal transmission lines in order to reduce the cost and size of components.
If such impedance discontinuity exists on the signal transmission path, the frequency component contained in the digital signal causes reflection and transmission loss.

In addition, it is often necessary to use an electrostatic protection element, various noise filters, a connector, or a flexible substrate, and depending on conditions, the signal rise time and impedance may change during operation.
For this reason, various problems related to signal waveform quality, such as a reduction in the eye opening ratio of the transmission waveform and an increase in deterministic jitter, have appeared.

In order to improve the transmission characteristics, a technique that incorporates a variable impedance circuit composed of a variable capacitor, PIN diode, etc. on the transmission line, and adjusts the impedance and improves the transmission characteristics is used to improve the transmission characteristics. Has been.
In this method, the element and the transmission line are electrically coupled to each other. In addition to the limitation due to the component characteristics and the inclusion of parasitic components, the influence of pad and via wiring and manufacturing variations cannot be avoided. A similar problem occurs in passive equalizer technology.

In addition, there is a method of suppressing reflection by connecting a plurality of impedances in advance with a microstrip line or the like (for example, see Patent Document 1).
However, this method does not deal with cases where the impedance distribution is unknown or includes variations among individuals.

Furthermore, there is a method using a distribution constant.
This technique is very effective for narrowband signal transmission.
However, since a digital signal includes frequency components in a wide band, multistage connection is often required for widening the band. Therefore, it is difficult to reduce the size.

Furthermore, a technique has been proposed in which the dielectric constant of the substrate is used as a ferroelectric to form a transmission line, and a voltage is applied to a signal conductor used for signal transmission to change the relative dielectric constant (for example, Patent Document 2). reference).
However, in this case, the purpose is microwave transmission, the magnitude of the change in relative permittivity is limited by the center frequency, and the effect is limited to a narrow band.
Further, in order to apply a voltage to a signal conductor, in general digital signal transmission, it is necessary to separate a part of the line in a DC manner and to perform C coupling (capacitive coupling).

JP-A-2005-150644 JP 7-11407 A

As described above, several methods for improving the transmission characteristics have been proposed, but it is difficult to cope with cases where the impedance distribution is unknown or individual variations are included. .
Also, the frequency band that can be handled is narrow, and it has been difficult to cope with a wide frequency band.

  In view of the above problems, the present invention can suppress reflection of a signal component caused by impedance discontinuity, and can realize jitter suppression and eye pattern opening of a transmission waveform transmitted to a receiving end. An impedance variable element and an electronic device including the impedance variable element are provided.

  The variable impedance element according to the present invention includes a signal transmission line, a dielectric material provided in contact with the signal transmission line, the electrical characteristics of which are changed by application of a voltage, and a voltage for applying a voltage to the dielectric material. The conductor can be applied with a voltage to the dielectric material to change the impedance, and the conductor is electrically independent from the signal transmission line.

  The electronic device of the present invention includes a signal transmission line and an electronic component connected to the signal transmission line, and includes the impedance variable element of the present invention.

According to the above-described configuration of the variable impedance element of the present invention, the dielectric material whose electrical characteristics are changed by application of voltage is provided in contact with the signal transmission line, and voltage is applied to the dielectric material by the conductor. Since the impedance can be changed, the impedance of the element can be changed by applying a voltage to the dielectric material through the conductor.
In addition, since the conductor is electrically independent from the signal transmission line, it is possible to greatly change the electrical characteristics of the dielectric material by applying a voltage from the conductor, greatly increasing the impedance adjustment range. And the electrical properties of the dielectric material can be optimized. Thereby, the reflection coefficient with respect to the frequency component contained in the signal transmitted through the signal transmission line can be reduced.

  According to the configuration of the electronic device of the present invention described above, having the signal transmission line and the electronic component connected to the signal transmission line, and including the impedance variable element of the present invention, greatly improves the impedance of the impedance variable element. The electrical characteristics of the dielectric material can be optimized. Thereby, the reflection coefficient with respect to the frequency component contained in the signal transmitted through the signal transmission line can be reduced.

According to the above-described present invention, it is possible to reduce a reflection coefficient with respect to a frequency component included in a signal transmitted through the signal transmission line.
Thereby, propagation of the reflected wave to the receiving end side can be reduced / suppressed.

In addition, since the impedance of the impedance variable element can be greatly changed, an effect can be obtained over a wide frequency band.
Furthermore, it is possible to cope with cases where the impedance distribution is unknown or includes variations among individuals.

Therefore, according to the present invention, it is possible to improve transmission characteristics in a signal transmission line in which impedance discontinuity exists.
In particular, in consumer devices, it can be expected to reduce deterministic jitter generated during digital signal transmission and to improve the eye opening ratio.

  First, prior to description of specific embodiments of the present invention, an outline of the present invention will be described.

  The present invention relates to a dielectric material such as a ferroelectric whose electrical characteristics such as relative permittivity change by application of a voltage, and a conductor (electrode) for applying a voltage to the dielectric material. The impedance variable element is configured around the (signal line). Then, by adjusting the voltage applied to the electrodes, the electrical characteristics of the dielectric material are changed to change the impedance.

  By changing the impedance of the impedance variable element, the waveform of the digital signal transmitted through the signal transmission line can be changed.

The dielectric material used in the present invention may be a material that changes in electrical characteristics such as relative permittivity by application of an electric field or magnetic field.
Examples of such materials include ordinary liquid crystal materials, gelled liquid crystal materials, dielectric materials having dielectric anisotropy (dielectric materials exhibiting anisotropy when voltage is applied), polymer materials, and PZT (titanium). Piezoelectric materials such as lead zirconate acid) and barium titanate, and ferroelectric materials.

The present invention includes a configuration in which a ferroelectric and an electrode are arranged around a signal transmission line (signal conductor) of a substrate including a flexible substrate, and a device in which a dielectric, a signal conductor, and an electrode are packaged. .
Further, the present invention can be applied to a differential transmission line.

As described above, when there is an impedance discontinuity that cannot be avoided due to the structure, the frequency component included in the digital signal causes reflection and transmission loss.
Therefore, in an electronic device having a signal transmission line and an electronic component connected to the signal transmission line, an impedance variable composed of a dielectric material and an electrode, particularly in the vicinity of a location where impedance discontinuity occurs. By arranging the elements, specific electrical characteristics can be optimized by controlling the voltage applied to the electrodes.
Thereby, the reflection coefficient with respect to the frequency component contained in the high-speed signal to transmit can be reduced.
Accordingly, since propagation of the reflected wave to the receiving end side can be reduced / suppressed, it is possible to realize eye pattern aperture ratio retention and jitter suppression.

In the configuration described in Patent Document 2, the dielectric constant of the dielectric material is changed by applying a voltage to the signal transmission line (signal conductor).
On the other hand, in the present invention, a conductor for applying a voltage is provided electrically independently from a signal conductor, and a voltage is applied to the separately provided conductor, thereby providing a dielectric material. Varying the dielectric constant. Thereby, compared with the structure described in the said patent document 2 which applies a voltage to a signal transmission line (signal conductor), a dielectric constant can be changed a lot and an effect is acquired with respect to a wide frequency band.
Further, it is possible to cope with cases where the impedance distribution is unknown or includes variations among individuals.

The impedance variable element of the present invention utilizes changes in electrical characteristics due to voltage application, and can change the dielectric constant relatively large, but there is a limit to the variable range of impedance accompanying the change in dielectric constant. .
Therefore, it is desirable to determine the center impedance of the variable impedance element.
Here, taking a microstrip line as an example, an approximate expression of characteristic impedance Z ₀ and effective relative permittivity ε _reff is shown below. In this approximate expression, the relative dielectric constant is ε _r , the conductor width is w, the conductor thickness is t, and the dielectric thickness is h.

When w / h <1

When w / h> 1

The values of w and h that satisfy the center impedance are determined by the median value of the variable range of the relative permittivity.
If the originally existing impedance discontinuous four-terminal parameters (S parameter, etc.) are known, the F matrix Fx is derived, and the F matrix F of the impedance variable element in the frequency band included in the digital signal. The impedance is such that the reflection coefficient S11 is minimized, which is derived from the cascade connection Fs = Fx · F.

  The above is a method of canceling the impedance discontinuity with one impedance variable element. Similarly, when canceling with two or more impedance variable elements, the reflection coefficient at the time of cascade connection is minimized. design.

  The median value of impedance and the variable range of impedance of the variable impedance element of the present invention are determined from the variable range of the relative dielectric constant according to the applied voltage of the dielectric used by using the above-described method. Can be determined by selecting the width w.

And, if there are 2n impedance variable elements, one each on the input side and output side of n impedance discontinuities, on the target transmission line, all reflections generated by impedance discontinuity The wave can be canceled.
With such an arrangement, it is possible to improve the waveform at both ends of the transmission line, and this configuration is used when performing bidirectional transmission.

  The present invention is particularly applicable when the signal transmitted through the signal transmission line is a digital signal, which is likely to cause reflection and transmission loss when impedance is discontinuous.

  The variable impedance element of the present invention can be applied to various electronic devices as an application.

In particular, the impedance variable element of the present invention is effective when a modularized circuit block is diverted to various types of electronic device products (diversion design).
For example, it is effective when applied to circuit blocks and high-speed signal I / F circuits common to a plurality of products such as tuner blocks and various motherboards.
Further, for example, it is also effective when the characteristics of the circuit to be connected are different from those of the circuit on which the impedance variable element of the present invention is mounted.

The impedance variable element of the present invention is also effective when applied to individual products.
For example, manufacturing variations can be suppressed by performing a sampling inspection and determining a center value of impedance at the time of shipment.
In addition, by applying a circuit that monitors the transmission characteristics, waveform, and impedance, and feeding back to the impedance adjustment circuit, waveform degradation due to changes in operating conditions and environment, such as changes in dielectric temperature and humidity, and changes in semiconductor characteristics due to temperature, etc. It can be avoided.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

As an embodiment of the present invention, FIG. 1A shows a schematic configuration diagram of a variable impedance element (a plan view through the inside).
In this embodiment, a microstrip-shaped variable impedance element is arranged in a substrate.

As shown in FIG. 1A, a signal line 11 extending in the left-right direction in the drawing is formed as a signal transmission line. An electrode 21 and a reference GND conductor 22 (GND) are disposed below the signal line 11.
The electrode 21 is insulated from the reference GND conductor 22 (GND) by an insulator (dielectric) 23.
Then, the electrode 21 has a structure in which the voltage V _B is applied from the outside.

A cross-sectional view taken along the signal line 11 in FIG. 1A is shown in FIG. 1B.
As shown in FIG. 1B, the signal line 11 is disposed in contact with the surface layer of the ferroelectric layer 12, and the reference GND conductor 22 (GND) and the electrode 21 are disposed in the lower layer.
With the structure shown in FIGS. 1A and 1B, an electric field can be applied to the ferroelectric layer 12 using the potential difference between the signal line 11 and the electrode 21.

  The ferroelectric layer 12 can be made of the ferroelectric material such as PZT (lead zirconate titanate) or barium titanate described above.

According to the configuration of the variable impedance element of the present embodiment described above, the ferroelectric layer 12 is provided in contact with the signal line 11, and the electrode 21 for applying a voltage to the ferroelectric layer 12 is disposed. Therefore, the impedance can be changed by applying a voltage (electric field) to the ferroelectric layer 12 by the voltage V _B supplied to the electrode 21.

Further, the electrode 21 to which the voltage V _B is applied is electrically independent from the signal line 11 by the ferroelectric layer 12. Thereby, the relative dielectric constant of the ferroelectric layer 12 is greatly changed by applying a voltage from the electrode 21 as compared with the configuration in which the signal line described in Patent Document 2 also serves as a voltage application conductor. Thus, the impedance adjustment range can be greatly widened.

Thereby, since the reflection coefficient with respect to the frequency component contained in the signal transmitted through the signal line 11 can be reduced, propagation of the reflected wave to the receiving end side can be reduced / suppressed.
Therefore, according to the impedance variable element of the present embodiment, it is possible to improve the transmission characteristics in the signal line 11 where the impedance discontinuity exists.

In the above-described embodiment, one electrode 21 for applying a voltage is provided. However, for example, a strip line or a coplanar waveguide configuration may be provided with a plurality of electrodes.
Further, for example, the electrode and the reference GND may be capacitively coupled with a capacitor or the like.

  2A and 2B show a form in which the variable impedance element of the embodiment shown in FIG. 1 is arranged in an actual circuit (of an electronic device). FIG. 2A shows a circuit configuration diagram, and FIG. 2B shows a plan view.

As shown in Figure 2B, as an electronic component to produce impedance discontinuities, impedance uses a varistor 100 is _{Z a,} to both ends of the varistor 100, the variable impedance element 1 impedance is _Z 1, _{Z 2,} 2 is arranged.
The detailed configuration of the two impedance variable elements 1 and 2 is the same as the impedance variable element shown in FIGS. 1A to 1B.
As shown in FIGS. 2A and 2B, the first variable impedance element 1 on the left, the impedance is Z _1, the second variable impedance element 2 on the right, the impedance is Z _2. The impedance of the signal line 11 of the portion varistor 100 is connected is Z _a, the impedance of the signal line 11 of the outer part is Z _0.

A first voltage V ₁ is supplied to the electrode 21 of the first variable impedance element 1 from the outside.
The second variable impedance element 2 of electrode 21, the second voltage V ₂ is supplied from the outside.

With such a configuration, the left and right impedances of the varistor 100 can be changed by the first impedance variable element 1 and the second impedance variable element 2, and the electrical characteristics of the signal line 11 can be changed. .
As a result, the electrical characteristics of the signal line 11 can be optimized, the reflection coefficient can be reduced, and propagation of the reflected wave to the receiving end caused by impedance discontinuity by the varistor 100 can be reduced / suppressed. .

As other embodiment of this invention, the schematic block diagram of an impedance variable element is shown to FIG. 3A-FIG. 3D. 3A is a cross-sectional view, FIGS. 3B and 3C are plan views of layers below the middle, and FIG. 3D is a schematic diagram in which an impedance variable element is componentized.
In the present embodiment, the device is further packaged as a stripline structure in which a ferroelectric is disposed around the signal conductor.

  As shown in the cross-sectional view of FIG. 3A, the ferroelectric layer 12 is provided in contact with the lower layer and the upper layer of the signal line 11, and electrodes 25 and 26 to which a voltage is applied are provided via the ferroelectric layer 12. It has been. Further, an insulating layer (dielectric layer) 27 is formed so as to cover the electrodes 25 and 26, and a reference GND conductor 24 (GND) is formed in the lowermost layer and the uppermost layer, thereby configuring the impedance variable element 30. is doing.

That is, a structure is adopted in which different voltages are applied to the two lower and upper ferroelectric layers 12 by the two electrodes 25 and 26 so that an electric field is applied to each ferroelectric layer 12.
Then, the electrodes 25 and 26 are sandwiched between reference GND conductors 24 (GND) via an insulating layer (dielectric layer) 27 and capacitively coupled.

  Further, the voltage applied to the lower layer electrode 25 and the voltage applied to the upper layer electrode 26 are configured to have opposite signs (+ voltage and − voltage). For example, a negative voltage is applied to the lower electrode 25 and a positive voltage is applied to the upper electrode 26.

The signal line 11 has input / output terminals T1 and T2 at both ends.
The lower layer electrode 25 is provided with a terminal T3. The upper electrode 26 is provided with a terminal T4. These terminals T1, T2, T3, and T4 are configured to be electrically connected to the outside of the variable impedance element 30, respectively.
A GND terminal T5 (see FIG. 3D) is provided for the reference GND conductor 24 (GND).

That is, as shown in the schematic diagram of FIG. 3D, signal input / output terminals (T1, T2), a positive electrode terminal and a negative electrode terminal (T3, T4), a GND terminal T5 for the reference GND electrode 24 (GND), etc. A component of the variable impedance element 30 having a total of five terminals is configured.
As described above, the signal line 11, the ferroelectric layer 12, and the electrodes 25 and 26 are packaged, and the impedance variable element 30 is formed as a component, so that it can be easily installed at various locations of the electronic apparatus.

  According to the configuration of the impedance variable element 30 of the present embodiment described above, the ferroelectric layer 12 is provided in contact with the signal line 11, and the electrodes 25 and 26 for applying a voltage to the ferroelectric layer 12 are provided. Since they are arranged, the impedance can be changed by applying a voltage (electric field) to the ferroelectric layer 12 by the voltage supplied to the electrodes 25 and 26.

  The electrodes 25 and 26 to which a voltage is applied are electrically independent of the signal line 11 by the ferroelectric layer 12 and the insulating layer (dielectric layer) 27. As a result, the relative dielectric constant of the ferroelectric layer 12 is greatly changed by applying a voltage from the electrodes 25 and 26 as compared with the configuration in which the signal line described in Patent Document 2 also serves as a voltage applying conductor. Therefore, the adjustment range of impedance can be greatly widened.

Thereby, since the reflection coefficient with respect to the frequency component contained in the signal transmitted through the signal line 11 can be reduced, propagation of the reflected wave to the receiving end side can be reduced / suppressed.
Therefore, according to the impedance variable element 30 of the present embodiment, it is possible to improve the transmission characteristics in the signal line 11 where the impedance discontinuity exists.

  In the impedance variable element 30 according to the embodiment shown in FIG. 3, the ferroelectric material 12, the GND conductor 24 (GND), and the conductors (electrodes) 25 and 26 for applying a voltage are respectively provided below and above the transmission line. However, the present invention includes a configuration in which a ferroelectric, a GND conductor, and a conductor (electrode) for applying a voltage are disposed only on either the upper side or the lower side of the transmission line.

  In the embodiment shown in FIG. 3, an insulating layer (dielectric layer) 27 is disposed outside the electrodes 25 and 26 and sandwiched between the reference GND conductors 24 (GND) to be capacitively coupled. And reference GND may be C-coupled externally, or a structure not using reference GND may be employed.

  FIGS. 4A and 4B show a configuration in which the impedance variable element having a stripline structure as a component shown in FIG. 3 is arranged in an actual circuit (of an electronic device). 4A shows a circuit configuration diagram, and FIG. 4B shows a plan view. Note that the circuit configuration diagram of FIG. 4A has the same configuration as the circuit configuration diagram of FIG. 2A.

As shown in FIG. 4B, in the middle of the signal line 11, two variable impedance elements 31 and 32 having a stripline structure are arranged so as to sandwich the signal line 11 of the portion to which the varistor 100 is connected. Yes.
The detailed configuration of the two impedance variable elements 31 and 32 is the same as that of the impedance variable element 30 shown in FIGS. 3A to 3D.
As shown in FIGS. 4A and 4B, the first variable impedance element 31 to the left, the impedance is Z _1, the second variable impedance element 32 to the right, the impedance is Z _2. The impedance of the signal line 11 of the portion varistor 100 is connected is Z _a, the impedance of the signal line 11 of the outer part is Z _0.

A voltage V _1H and a voltage V _1L are supplied to the first impedance variable element 31 from the outside to the respective electrodes (corresponding to the electrodes 25 and 26 in FIG. 3).
The second variable impedance element 32 is supplied with a voltage V _2H and a voltage V _2L from the outside to the respective electrodes (corresponding to the electrodes 25 and 26 in FIG. 3).

With such a configuration, the left and right impedances of the varistor 100 can be changed by the first impedance variable element 31 and the second impedance variable element 32, and the electrical characteristics of the signal line 11 can be changed. .
As a result, the electrical characteristics of the signal line 11 can be optimized, the reflection coefficient can be reduced, and propagation of the reflected wave to the receiving end caused by impedance discontinuity by the varistor 100 can be reduced / suppressed. .

In each of the variable impedance elements according to each of the embodiments described above, the dielectric layer is sandwiched between the signal conductor (signal line) and the voltage application conductor. A configuration in which the applying conductor is provided on the same main surface side of the dielectric layer is also included.
However, the signal conductor and the voltage application conductor are separate electrically independent conductors.
Even when the signal conductor and the voltage applying conductor are provided on the same main surface side of the dielectric layer as described above, an electromagnetic field accompanying signal transmission exists in the dielectric layer. Since it is affected by the change in effective relative permittivity, it is possible to change the impedance by applying a voltage.
If the signal conductor is also used as a voltage application conductor and a voltage is applied to the signal conductor, it is necessary to separate the signal conductor by coupling with a capacitor or the like. This is not preferable because there is a possibility that impedance discontinuity may occur in the capacitor itself.

(Example)
Here, a configuration in which the impedance variable element of the present invention was applied to both ends of an inductor having an inductance of 3 [nH] was manufactured, and the characteristics were examined.
And in the case after the application which applied this invention, and the case of the inductor before application, each reflection characteristic S11 is shown to FIG. 5A, and each transmission characteristic S21 is shown to FIG. 5B.
As shown in FIG. 5A, it can be seen that when the present invention is applied, the reflection characteristic S11 can be reduced. And it turns out that it can reduce significantly especially in a frequency below 3 GHz.
As shown in FIG. 5B, when the present invention is applied, it is possible to reduce the dispersion of the transmission characteristic S11 depending on the frequency, and to obtain the stable transmission characteristic S11 in a wide frequency range.

Moreover, the transmission line which modeled the impedance mismatch which comprised the circuit block diagram in FIG. 6 was comprised. FIG. 6 shows impedances Z ₀ (= 50Ω) and Z _X (= 150Ω) of each part of the transmission line and the line length of each part.
FIG. 7A shows a transmission waveform when a 3.0 Gbps pseudo-random signal is supplied to this transmission line.
FIG. 7B shows a transmission waveform when the same pseudo-random signal is supplied to the configuration in which the present invention is applied to this transmission line.
As can be seen by comparing FIG. 7A and FIG. 7B, by applying the present invention, a good eye pattern aperture ratio can be realized.

  From the above results, by applying the configuration of the impedance variable element of the present invention, it is possible to suppress reflection on the high-speed digital signal transmission line where impedance discontinuity exists, and to reduce jitter and improve transmission waveform. Recognize.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

1A and 1B are schematic configuration diagrams of an impedance variable element according to an embodiment of the present invention. A, B It is the figure which showed the form which has arrange | positioned the impedance variable element of FIG. 1 in the actual circuit. AD is a schematic block diagram of the impedance variable element of other embodiment of this invention. A, B It is the figure which showed the form which has arrange | positioned the impedance variable element of FIG. 3 in the actual circuit. It is the figure which compared the reflection characteristic and the permeation | transmission characteristic with the case where this invention is applied to the both ends of A and B inductors, and the case before applying. It is a circuit block diagram of the transmission line which modeled impedance mismatching. A, B It is a figure which shows the transmission waveform at the time of supplying a pseudo random signal to the transmission line of FIG. 6, and the structure which applied this invention to the transmission line of FIG. 6, respectively.

Explanation of symbols

  1, 2, 30, 31, 32 Impedance variable element, 11 signal line, 12 ferroelectric layer, 21, 25, 26 electrode, 22, 24 reference GND conductor, 23 insulator (dielectric), 27 insulation layer (dielectric) Body layer), 100 Varistor

Claims (5)

A signal transmission line;
Provided in contact with the signal transmission line, a dielectric material whose electrical characteristics change by application of voltage,
A conductor for applying a voltage to the dielectric material;
It is possible to change the impedance by applying a voltage to the dielectric material through the conductor,
The impedance variable element, wherein the conductor is electrically independent from the signal transmission line.   The variable impedance element according to claim 1, wherein the dielectric material is a ferroelectric.   The variable impedance element according to claim 1, wherein the signal transmission line, the dielectric material, and the conductor are packaged. A signal transmission line;
An electronic device having an electronic component connected to the signal transmission line,
The signal transmission line, a dielectric material which is provided in contact with the signal transmission line and whose electrical characteristics change by application of voltage, and a conductor for applying a voltage to the dielectric material, the conductor It is possible to change the impedance by applying a voltage to the dielectric material, and the conductor includes an impedance variable element configured to be electrically independent of the signal transmission line. Electronic equipment.   The electronic device according to claim 4, wherein the impedance variable element is provided in the vicinity of a location where the signal transmission line has impedance discontinuity.

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