JPH0720164A - Reflectionless termination ac-dc converter - Google Patents

Abstract

PURPOSE:To obtain a highly accurate AC-DC converter by a method wherein, even when a high-frequency alternating current at about 1 MHz to 10 GHz is measured, reflection is eliminated at a termination part inside a coaxial wire. CONSTITUTION:In an AC-DC converter, a reflectionless termination resistor whose diameter is the same as that of an inner conductor 2 and which is composed of a tube body 4 constituted of an insulating film is installed on the extension line of a coaxial wire 1 which is composed of the inner conductor 2 and of an outer conductor 3 installed at its outer circumference, a resistance film 6 is formed on the surface of the tube body 4, the characteristic impedance on the side of the coaxial wire 1 is made equal to the characteristic impedance on the side of the termination resistor, and a thermocouple 7 is installed between the resistance film 6 and the tube body 4 or on the back side of the tube body 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC converter for precisely measuring AC in a high frequency band of 1 MHz to 10 GHz.

[0002]

2. Description of the Related Art In order to accurately measure an AC voltage (current), it is necessary to compare the AC voltage (current) with the DC voltage (current).

Conventionally, as a converter used for this comparison, there is a converter in which a current is passed through a resistance wire (heater) and the temperature rise is detected by a thermocouple.

That is, by applying an AC voltage (current) to the converter, adjusting the output DC voltage (current) at which the thermoelectromotive force is the same, and comparing it with the DC voltage (current) This is to obtain the effective value of voltage (current).

At the time of this comparison, there is a slight difference between the AC voltage and the DC voltage. This is called the AC / DC difference of the converter, and a converter with a small AC / DC difference is desirable.

Conventionally, as an audio single junction thermoelectric type AC / DC converter, as shown in FIG. 4, a resistance wire (heater) 11 in which a resistance R for voltage division is incorporated is inserted in a coaxial wire 1. There is known a structure in which a high temperature contact of a thermocouple 7 is fixed to a resistance wire (heater) 11 via beads 12.

[0007]

On the other hand, as shown in FIG. 5, a high-frequency current passing through the resistance wire 11 in the coaxial wire 1 radially generates an electric field E and a magnetic field line H around the resistance wire 11. ,
Since the thermocouple 7 is a good conductor, the line of electric force E is disturbed by this, and the high frequency alternating current is reflected at the end of the coaxial line 1.

Therefore, in the AC / DC converter having this structure,
AC measurements at frequencies from 1KHz to 1MHz are accurate,
This results in a measurement error when measuring high-frequency AC of 1 MHz or higher.

In addition to thermocouples, there are AC / DC converters provided with heat sensors, such as CCDs and infrared sensors, but these are extremely expensive, the apparatus is complicated, and sufficient sensitivity can be obtained. It has the drawback of not having it.

Therefore, an object of the present invention is to provide an AC / DC converter using a thermocouple for highly accurate AC / DC conversion even when measuring a high frequency AC of about 1 MHz to 10 GHz.

[0011]

In order to solve the above problems, the present invention has the same diameter as the inner conductor on the extension of the coaxial line composed of the inner conductor and the outer conductor provided on the outer periphery of the inner conductor. A non-reflective terminating resistor composed of a cylindrical body made of an insulating film is provided, and a resistance film is provided on the surface of the cylindrical body to equalize the characteristic impedance on the coaxial line side with the characteristic impedance on the terminating resistor side. We propose an AC / DC converter in which a thermocouple is interposed between the membrane and the cylinder.

That is, according to the present invention, a reflection-free terminating resistor made of a cylindrical body made of an insulating film having the same diameter as the inner conductor is provided on the extension of the coaxial wire, and the resistive film is provided on the surface of the cylindrical body. Since the characteristic impedance on the coaxial line side and the characteristic impedance on the terminating resistor side are made equal and a thermocouple is provided between the resistive film and the cylinder or on the back side of the cylinder, 1MHz
There is no reflection at the end of the coaxial line even when measuring high-frequency AC of about 10 GHz, so a highly accurate AC / DC converter can be made.

The non-reflective terminating resistor used in the present invention is, for example, an exponential-shaped or tractorial-shaped compensating tube around the outer periphery of the terminating resistor made of a cylindrical body made of an insulating film having the same diameter as the inner conductor. Can be used, or a stripline with a non-reflective end of a stripline having a rectangular cross section can be used.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment using a non-reflective terminating resistor having an exponential function-shaped compensating tube provided on the outer periphery thereof.

In this embodiment, 1 is a coaxial wire consisting of an inner conductor 2 made of a conductive metal such as copper and an outer conductor 3 made of a metal tube provided on the outer circumference of the inner conductor 2, and 4 is an inner conductor 2. Cylindrical bodies 5 made of an insulating film such as polyimide having the same diameter as the inner conductor 2 provided on the extension are exponential function-shaped resistance compensation tubes provided on the outer circumference of the tubular body 4.

The surface of the cylinder 4 is made of, for example, Ni, Cr, M.
A resistance film 6 made of an n, Fe alloy film is provided so that the characteristic impedance on the coaxial line side and the characteristic impedance on the terminating resistor side at the terminal end of the inner conductor 2 are equalized.

Further, a thermocouple 7 is provided between the resistance film 6 and the cylindrical body 4 or on the back side of the cylindrical body 4 with the end portion of the inner conductor 2 as a cold junction.

[0018] That is, the length of the resistor covered with resistive compensating tube 5 exponential shape with the outer periphery of the cylindrical body 4 is the resistance R, the cylindrical body 4 L, inner diameter D _x of the distance from the input end of the x, cylinder The following relationship is established between the body diameters d.

[0019]

[Formula 1]

With such a structure, theoretically, the input impedance becomes the pure resistance R regardless of the frequency, and matching can be achieved in all parts in the resistor.

Moreover, in the present invention, the thermocouple 7 is the resistance film 6
Since it is provided between the cylinder 4 and the cylinder 4 or on the back side of the cylinder 4, precise AC / DC conversion can be performed without being affected by the frequency.

Incidentally, the resistance compensation tube 5 having the exponential function shape described above.
Is designed on the assumption that it is a cylindrical coaxial line for a minute length, but the tractorial resistance compensation tube is designed on the assumption that it is a conical coaxial line for a minute length. However, the structure is almost the same as that of the exponential shape.

Further, since a very complicated work is required to produce a resistance compensation tube having an exponential curvature or a tractorial shape, a so-called linear taper tube which is approximately linearly drawn may be used. In this case, it can be used up to about several tens GHz.

FIG. 2 shows an example in which the reflectionless termination resistor of the strip line having a rectangular cross section is used as the reflectionless termination resistor used in the present invention, and the coaxial line 1 is shown in FIG.
As shown in FIG. 3, the inner conductor 2 has a square cross section with a diameter W and the outer conductor 3 has a square cross section with a diameter D.

On the extension of the coaxial line 1, a cylindrical body 4 made of polyimide having a square cross section with a diameter W of a predetermined length and an outer tube 8 having a square cross section with a diameter D are provided on the outer periphery of the cylindrical body 4 to provide a non-reflective terminating resistor. And a resistor film 6 of a predetermined length is formed on the surface of the cylindrical body 4 to equalize the characteristic impedance on the coaxial line side and the characteristic impedance on the terminating resistor side.

As shown in FIG. 3, the thermocouple 7 is provided between the square cylindrical body 4 and the resistance film 6 or on the back side of the cylindrical body 4,
Furthermore, in order to prevent electromagnetic waves from escaping through the space inside the cylindrical body 4, a plurality of cheek metal tubes 10 connected by a coupler 9 are connected.
Insert.

As a result, it is possible to perform precise AC / DC conversion without being affected by the frequency, as in the above embodiment.

[0028]

In summary, according to the present invention, the non-reflective terminating resistor formed of a cylindrical body made of an insulating film having the same diameter as the inner conductor is provided on the extension of the coaxial wire, and the surface of the cylindrical body is provided. Since a resistance film is provided on the coaxial line, the characteristic impedance on the coaxial line side and the characteristic impedance on the terminating resistor side are made equal, and a thermocouple is interposed between the resistance film and the cylindrical body,
Even when measuring high-frequency AC of about 1MHz to 10GHz, there is no reflection at the end of the coaxial cable, so high-accuracy AC-DC conversion is possible.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing an embodiment using a non-reflection terminating resistor provided with an exponential function-shaped compensation tube.

FIG. 2 is a vertical cross-sectional side view showing an embodiment using a non-reflection end of a strip line having a rectangular cross section.

3A and 3B are views showing the same cylindrical body, FIG. 3A is a cross-sectional front view, and FIG. 3B is a vertical cross-sectional side view.

FIG. 4 is a diagram showing an example of a conventional audio single junction thermoelectric type AC / DC converter.

FIG. 5 is a diagram showing a relationship between magnetic force lines H and electric force lines E within a square coaxial line.

[Explanation of symbols]

 1 is a coaxial tube 2 is an inner conductor 3 is an outer conductor 4 is a cylindrical body 5 is a resistance compensation tube 6 is a resistance film 7 is a thermocouple 8 is an outer tube 9 is a coupler 10 is a plurality of cheek metal tubes 11 is a resistance wire (heater) ) 12 is beads

Claims (4)

[Claims] 1. A non-reflective terminating resistor made of a cylindrical body made of an insulating film having the same diameter as the inner conductor is provided on an extension of a coaxial line made of an inner conductor and an outer conductor provided on the outer periphery of the inner conductor.
A resistive film is provided on the surface of the tubular body, the characteristic impedance on the coaxial line side and the characteristic impedance on the terminating resistor side are made equal, and a thermocouple is provided between the resistive film and the tubular body or on the back side of the tubular body. A characteristic non-reflective termination AC / DC converter. 2. The non-reflective termination AC / DC converter according to claim 1, wherein a non-reflective termination resistor provided with a compensating tube having an exponential function shape on the outer periphery of a cylindrical body is used. 3. The non-reflective termination AC / DC converter according to claim 1, wherein a non-reflective termination resistor provided with a tractorically shaped compensating tube on the outer circumference of the cylindrical body is used. 4. A reflectionless termination AC / DC converter according to claim 1, wherein a stripline having a rectangular cross section is used as the reflectionless termination resistor.