JPH10197577A - Standard gauge for calibration of high frequency measurement, method of calibration, and transmission loss measuring method for high frequency transmitting line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a measuring method for the transmission loss in a high frequency transmission line which can accurately extract the transmission constant by the TRL (trough reflect line) calibration method even for high frequency wave, for example in the milli-wave band, and can extract the transmission loss. SOLUTION: A calibration standard gauge is for high frequency measurement for use with the TRL calibration method where line conductors 15, 17, 21 are formed on dielectric base boards 14, 16, 18 and includes a delay line whose delay part has an electric length larger than half one vacuum wavelength of the frequency to be measured, and the calibration of the high frequency measurement is made using this standard gauge, and thereupon the transmission loss of a high frequency transmission line is measured. Accurate delay can be determined even for a high frequency wave, for example in the milli-band, with small drop of the accuracy, and it is possible to make calibration with high precision and high certainty. Also the transmission constant can be extracted accurately, and the transmission loss be extracted accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-accuracy and high-accuracy calibration standard and method for performing high-accuracy high-frequency measurement of transmission loss of a high-frequency transmission line, and a method of measuring transmission loss of a high-frequency transmission line. About.

[0002]

2. Description of the Related Art Hitherto, transmission loss of a transmission line has been measured to evaluate whether or not the length of a high-frequency transmission line used in a high-frequency circuit is appropriate. A calibration method for such a high-frequency measurement is a TRL (Trough-Reflect-Line) calibration method.

The principle of this TRL calibration method is described in, for example, David
Rubin, "De-Embedding mm-Wave MICs with TRL" (MICR
OWAVE JOURNAL, June 1990, pp. 141-150), the measured value with the measurement reference plane directly connected and the measurement value with the measurement reference plane shorted or open. And a measurement value in a state where the measurement reference planes are connected via a delay line. Specifically, FIG. 3 shows a connection between two terminals corresponding to a predetermined measurement reference plane.
(A) to (d) have four structures as shown in plan views, that is, (a) a basic direct connection in which a terminal 1 and a terminal 2 are directly connected by a transmission line 3 having the same electrical length as a high-frequency transmission line to be measured. Structure, (b) reflection measurement structure in which transmission lines 6.6 ′ having open ends are connected to terminals 4 and 5, respectively;
(C) an electrical length measurement structure in which the terminals 7 and 8 are directly connected by a transmission line (for example, a delay line) 9 longer than the transmission line 3 of (a), and (d) the terminals 10 and 11 are connected to the transmission line 3 of (a).
Are connected by a transmission line 12 having the same length as that of the device, and a scattering parameter (S
Is a calibration method for removing errors in high-frequency measurement by a predetermined calculation from a set of four types of measurement data of
Further, for example, the transmission loss of the high-frequency transmission line can be obtained by extracting the attenuation constant α and the phase coefficient β of the high-frequency transmission line to be measured from the measurement data in the structures (a) and (c). It is possible.

The measurement frequency band used in the actual measurement by the TRL calibration method is a state in which the measurement reference planes (terminals 1 and 2) are directly connected by the high-frequency transmission line 3 (FIG. 3).
(A) and the state where the measurement reference planes (terminals 7 and 8) are connected via the delay line 9 (the structure in FIG. From the necessary conditions such as the ratio with respect to the reflection tracking error and the selection of the sign of the solution of the propagation constant of the delay section of the delay line, the electrical length of the delay section of the delay line is 1/1 of the lowest frequency vacuum wavelength to be measured.
18 or more and 4/9 or less of the vacuum wavelength of the highest frequency to be measured, that is, the phase rotating during propagation through the delay part of the delay line is in the range of 20 ° to 160 ° (the phase margin is
(A 20 ° margin) is used.
For example, in a TRL calibration method for a microstrip line formed on a substrate having a relative dielectric constant of 9.5, when a delay portion having a physical length of 3 mm is provided in the line as the structure of FIG. Since the rate is about 6.5, the frequency band in which the phase rotation during propagation through the delay section is in the range of 20 ° to 160 ° is 2.2 to 17.4 GHz.

[0005]

However, in this case, the propagation constant extracted by the TRL calibration method is shown in FIG. 4 as a graph showing the frequency characteristic of the propagation constant. Therefore, the fluctuation of the propagation constant increases, and the accuracy decreases. In FIG. 4, the horizontal axis represents the frequency f (GHz), the vertical axis represents the attenuation constant α (dB / m) of the propagation constant, and the curve A is extracted by the TRL calibration method under the above conditions. 6 shows a frequency characteristic curve of the attenuation constant α per unit length of the transmission line.

Therefore, for example, in order to perform measurement in a frequency range higher than the above-mentioned frequency band, it is necessary to use a delay line having a delay section having a shorter physical length than the above. In this case, the physical quantity of the delay section must be reduced. If the length is extremely short, there is a problem that the accuracy of the propagation constant obtained is further reduced because the propagation loss becomes a level that is buried in the measurement error.

In the conventional TRL calibration method, as described above, the electric length of the delay section of the delay line is 20 ° as a frequency band.
Since a frequency band that serves as a margin is used, in order to perform measurement over a wide band of frequencies, for each of a plurality of delay lines, the frequency band covered by the electrical length of the delay section is determined, and the plurality of delay lines are determined. It is necessary to use a line, and for high frequencies such as the millimeter wave band, the physical length corresponding to the delay section of the plurality of delay lines becomes extremely short, so that the accuracy is greatly reduced and an accurate delay is obtained. There is also a problem that it is difficult to perform calibration.

Further, the propagation constant extracted using the delay line of the delay unit having a short physical length is at a level such that the transmission loss is buried in the measurement error due to the short delay unit, and thus the transmission loss is reduced. There is also a problem that accurate extraction becomes difficult and the result becomes inaccurate.

The present invention has been completed in view of the above-mentioned problems in the prior art as a result of the inventor's intensive research, and an object of the present invention is to provide a TRL calibration method used as a calibration method in high-frequency measurement, that is, a measurement method. Calibration method using measured values when the reference planes are directly connected, measured values in the short-circuited or open state on the measured reference planes, and measured values when the measurement reference planes are connected via the delay line With respect to high frequency such as millimeter wave band, there is little decrease in accuracy, accurate delay can be obtained, high-precision and high-accuracy calibration can be performed. It is to provide a calibration method.

[0010] It is another object of the present invention to provide a TRL calibration method for accurately extracting a propagation constant with high accuracy even for a high frequency such as a millimeter wave band, and for accurately extracting a transmission loss. To provide a method for measuring the transmission loss of a transmission line.

[0011]

According to the present invention, there is provided a calibration standard for high frequency measurement, comprising: a scattering parameter measurement value in a state where the measurement reference planes are directly connected by a high frequency transmission line; and a delay line between the measurement reference planes. A calibration standard for high-frequency measurement for calibrating high-frequency measurement related to transmission characteristics of a high-frequency transmission line, which is used in a TRL calibration method using a scattering parameter measurement value in a state where the delay line is connected via the delay line. Is characterized in that a line conductor is formed on a dielectric substrate, and the electrical length of the delay section is longer than half the vacuum wavelength of the frequency to be measured.

Further, the calibration method for high-frequency measurement according to the present invention provides a method for measuring scattering parameters in a state in which measurement reference planes are directly connected by a high-frequency transmission line, and a method in which measurement reference planes are connected via a delay line. In a calibration method for high-frequency measurement on transmission characteristics of a high-frequency transmission line by a TRL calibration method using a measured value of a scattering parameter and a delay line, a delay line is formed by forming a line conductor on a dielectric substrate as the delay line. It is characterized in that a delay line having an electrical length longer than half the vacuum wavelength of the frequency to be measured is used.

Further, according to the method for measuring transmission loss of a high-frequency transmission line of the present invention, the transmission loss of the high-frequency transmission line is measured by measuring a scattering parameter in a state where the measurement reference planes are directly connected by the high-frequency transmission line. And a scattering parameter measurement value in a state where the measurement reference planes are connected via a delay line. The measurement method is a TRL calibration method, wherein a line conductor is formed on a dielectric substrate as the delay line. In this case, a delay line whose electrical length is longer than half the vacuum wavelength of the frequency to be measured is used.

According to the calibration standard for high-frequency measurement of the present invention, a delay line connecting between measurement reference planes, which is a calibration standard used in the TRL calibration method, is formed by forming a line conductor on a dielectric substrate, In addition, since the electrical length of the delay section is longer than the vacuum wavelength of the measured frequency, that is, half of the wavelength in vacuum, the physical length of the delay section of the delay line is high even for high frequencies such as the millimeter wave band. Becomes sufficiently long with respect to the accuracy of the measurement, so that an accurate delay can be obtained with high accuracy, and more accurate and accurate calibration can be performed. Further, the propagation constant extracted from the delay section of the delay line becomes accurate and accurate, and therefore, an accurate transmission loss can be extracted and obtained.

As a calibration standard used in the conventional TRL calibration method, if the measurement frequency band is wide and a single delay line cannot cover the entire band, it is necessary to maintain a predetermined accuracy. Although it is common practice to divide the measurement frequency band into a plurality of parts and use a plurality of delay lines having an electrical length corresponding to each band, a plurality of delay lines are similarly used for the calibration standard of the present invention. It goes without saying that tracks can be used.

Further, according to the calibration method for high-frequency measurement of the present invention, as a delay line for connecting between measurement reference planes used in the TRL calibration method, the electric potential of the delay section is formed by forming a line conductor on a dielectric substrate. Since a delay line whose length is longer than half the vacuum wavelength of the frequency to be measured is used, the physical length of the delay section of the delay line is sufficient for the measurement accuracy even at high frequencies such as the millimeter wave band. As the length becomes longer, accurate delay can be obtained with high accuracy, and more accurate and accurate calibration can be performed. Also, according to this calibration method, the propagation constant extracted from the delay section of the delay line becomes accurate and accurate, and therefore, an accurate transmission loss can be extracted and obtained.

In the conventional TRL calibration method, when the measurement frequency band is wide and one delay line cannot cover the entire band, the measurement frequency band is divided into a plurality of parts in order to maintain a predetermined accuracy. Although it is common practice to use a plurality of delay lines having an electrical length corresponding to each band, the calibration method of the present invention may also use a plurality of delay lines. Needless to say.

Further, according to the method for measuring transmission loss of a high-frequency transmission line of the present invention, the scattering parameter in a state where the measurement reference planes are directly connected by a transmission line having the same electrical length as the high-frequency transmission line to be measured. When the transmission loss of the high-frequency transmission line is determined by the TRL calibration method using the measured values and the measured values of the scattering parameters in a state where the measurement reference planes are connected via the delay line, a dielectric substrate is used as the delay line. Since a delay line having a line conductor formed thereon and having an electrical length longer than half the vacuum wavelength of the frequency to be measured is used, the delay portion of the delay line can be used for high frequencies such as the millimeter wave band. Physical length is sufficiently long for the accuracy of the measurement, so that accurate delay can be obtained with high accuracy and accurate propagation constant can be obtained, and more accurate and accurate Transmission loss Measurement becomes the thing done.

In the method of measuring the transmission loss of the high-frequency transmission line according to the present invention, it is needless to say that a plurality of delay lines having different electric lengths may be used as in the above-described TRL calibration method. No.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a calibration standard and a calibration method for high-frequency measurement and a method for measuring transmission loss of a high-frequency transmission line according to the present invention will be described with reference to the drawings. Scattering parameter measurement value when directly connected (Thru connection: direct connection) with a transmission line having the same electrical length as the high-frequency transmission line to be measured, and scattering parameter measurement value when the measurement reference plane is connected via a delay line A description will be given of an example in which the TRL calibration method is used to calculate and extract the propagation constant of a high-frequency signal wave propagating in the delay section of the delay line as a loss amount per unit length.

Conventionally, the electrical length of the delay section of the delay line is at least 1/18 of the lowest frequency to be measured, ie, the vacuum wavelength of the lowest frequency to be measured, and 4/9 of the highest frequency to be measured, ie, the vacuum wavelength of the highest frequency to be measured. In order to have the following length,
That is, for example, 5 GHz to 40 GHz in order to use as a measurement frequency band a frequency at which the phase rotating during the propagation of the high-frequency signal to be measured in the delay section of the delay line is in the range of 20 ° to 160 °. When the measurement is performed in the frequency range described above, a microstrip line formed on a substrate having a relative permittivity of 9.5 uses a delay line having a physical length of about 1.3 mm as a delay line.

However, since the transmission loss is small in such a short delay section, the accuracy of a measuring instrument (such as a vector network analyzer) becomes insufficient, and it becomes difficult to extract the transmission loss. In other words, the accuracy of the measuring instrument in the transmission direction is usually ±
The transmission loss of a microstrip line having a physical length of about 1.3 mm is about 0.02 dB, while the general transmission loss is about 40 mm.
Since it becomes 0.05 dB near GHz, the measurement error due to the accuracy of the measuring device increases, and the amount of loss extraction is greatly affected by the error.

On the other hand, in the calibration standard for high frequency measurement according to the present invention, as shown in a plan view of FIG. 1, the delay line is formed by forming a line conductor on a dielectric substrate, and The electrical length of the portion is longer than half the vacuum wavelength of the frequency to be measured, that is, the frequency to be measured. In the calibration method for high-frequency measurement of the present invention, this delay line is used as a delay line connecting between measurement reference planes. It is.

In FIG. 1, (a) shows a dielectric substrate 14
A basic direct connection structure in which a transmission line (line conductor) 15 having the same electrical length as the high-frequency transmission line to be measured is formed on the dielectric substrate 16, and (b) is a line (Delay Line) connection transmission on the dielectric substrate 16. (C) is a reflection measurement structure in which the transmission lines 19 and 19 ′ in a Reflect (Open) state are formed on a dielectric substrate 18, and (d) is a dielectric measurement structure in which the transmission lines 19 and 19 ′ are formed on a dielectric substrate 18. FIG. 3 shows a device structure in a state where a DUT 22 (portion defined by a dashed line) is connected to the center (calibration plane) of a transmission line 21 of a Thru connection formed on a body substrate 20. FIG. 1D shows an example in which a band-pass filter is used as the DUT 22.

Further, (c) and (d) are not particularly required for the present invention, but are required when other parameter measurement is performed based on the TRL calibration method according to the present invention.

The dielectric substrates 14, 16, 18, 20 include:
Various insulating ceramics such as alumina-based materials and aluminum nitride-based materials, Teflon (PTFE), glass epoxy,
A substrate made of a dielectric material such as an insulating resin material such as polyimide is used.

The transmission lines 15, 17, 18, 19, 19 '
-The line conductor deposited as 21 is for high-frequency signal transmission composed of a material such as tungsten, chromium, molybdenum, copper, silver, gold, or an alloy thereof deposited on the dielectric substrate in a line shape. And a conductive material that can be formed thereon according to the material of the dielectric substrate. For high-frequency signals in the microwave band or millimeter wave band, for example, a dielectric substrate made of an alumina-based material and chromium-copper-
A combination with a line conductor made of nickel-gold may be used.

According to the calibration standard and the calibration method for high frequency measurement of the present invention, in the measurement system using a microstrip line formed on a substrate having a relative dielectric constant of 9.5, for example, a delay of 8.0 mm in physical length. Using a delay line with
Further, a delay line having a delay part of 6.4 mm and 5.1 mm in physical length is used. At this time, the effective relative permittivity of the microstrip line having a relative permittivity of 9.5 is about 6.5, and the electrical lengths of the delay portions are 20.4 mm, 16.3 mm and 13.0 mm, respectively.
mm.

Here, the frequency range in which the accuracy is reduced in the extraction of the propagation constant due to the requirement of the TRL calibration method is as follows, where the effective relative permittivity is ε _reff and the physical length of the delay section of the delay line is l. Become.

{(180n-20) / 360} × {1 / (l ×})
ε _reff )｝ × 300 ～ ｛(180n + 20) / 360｝ ×｝ 1 /
(L × {ε _reff )} × 300 where n is an integer and the unit is GHz.

That is, in a measurement in a frequency band of 40 GHz or less, when a delay line having an electric length of 20.4 mm is used, a delay line of 0 to 0.82 GHz 6.5 to 8.2 GHz.
13.8-15.5GHz ・ 21.2〜22.9GHz ・ 28.6〜30.2GH
The accuracy of extraction of the propagation constant is reduced in each frequency range of z · 36.0 to 37.6 GHz. The electrical length of the delay section is 16.3
mm delay line, 0 to 1.0 GHz 8.2
~ 10.2GHz ・ 17.4〜19.4GHz ・ 26.6〜28.6GHz ・
In a case where a delay line having an electric length of 13.0 mm is used in each frequency range of 35.8 to 37.8 GHz and the delay section is 13.0 mm, 0 is used.
1.3GHz ・ 10.3〜12.8GHz ・ 21.8〜24.3GHz ・
In each frequency range of 33.32 to 35.9 GHz, the accuracy of extracting the propagation constant is reduced.

Therefore, when the propagation constant is extracted using these three types of delay lines, the electric length of the delay unit is 20.4 m.
The frequency range where the extraction accuracy of the propagation constant in the m delay line is reduced is switched to the extraction in the delay line with the electrical length of the delay unit of 16.3 mm, and the electrical length of the delay unit is 20.4 mm with the delay line of 16.3 mm. By switching the frequency range in which the extraction accuracy of the propagation constant in the delay line decreases to the extraction in the delay line in which the electrical length of the delay unit is 13.0 mm, a frequency range of 0.82 to 40.0 GHz as a frequency range in which high-frequency measurement can be performed with high accuracy. A measurement frequency band can be obtained.

FIG. 2 shows the result obtained by extracting the propagation constant α as the transmission loss per unit length of the high-frequency transmission line (the microstrip line) using the combination of the delay line and the measurement frequency band. FIG. 4 shows a frequency characteristic diagram similar to that of FIG. Also in FIG. 2, the horizontal axis represents the frequency f (GHz), and the vertical axis represents the attenuation constant α of the propagation constant.
(DB / m), and a curve B indicates a frequency characteristic curve of the attenuation constant α per unit length of the high-frequency transmission line extracted by the TRL calibration method under the above conditions.

As can be seen from FIG. 2, using the calibration standard for high frequency measurement of the present invention, calibration is performed by the calibration method of the present invention, a measurement frequency band is obtained, and the transmission loss of the high frequency transmission line of the present invention is measured. By obtaining the transmission loss, for example, the propagation constant by the method, even if the frequency becomes higher in the obtained frequency band, the fluctuation of the obtained propagation constant does not become large and the accuracy does not decrease as in the past, and the high accuracy can be obtained. In addition, the propagation constant α can be accurately extracted, so that an accurate transmission loss can be obtained.

It should be noted that the present invention is not limited to the above example, and that various changes and improvements can be made without departing from the spirit of the present invention. For example, according to the present invention, the phase constant β among the propagation constants can be extracted with high precision and accuracy, and the effective relative permittivity ε _reff can be obtained based on the result.

[0036]

According to the calibration standard for high-frequency measurement of the present invention, a delay line connecting between measurement reference planes, which is a calibration standard used in the TRL calibration method, is formed by forming a line conductor on a dielectric substrate. Since the electrical length of the delay section is longer than the vacuum wavelength of the frequency to be measured, that is, half of the wavelength in vacuum, the physical length of the delay section of the delay line is not affected by high frequencies such as the millimeter wave band. The length is sufficiently long with respect to the accuracy of the measurement, so that an accurate delay can be obtained with high accuracy, and a more accurate and accurate calibration can be performed. Further, the propagation constants extracted from the delay sections of these delay lines are accurate and accurate, and therefore, accurate transmission losses can be extracted and obtained.

Further, according to the calibration method for high-frequency measurement of the present invention, as a delay line connecting between the measurement reference planes used in the TRL calibration method, the electric power of the delay section is formed by forming a line conductor on a dielectric substrate. Since a delay line whose length is longer than half the vacuum wavelength of the frequency to be measured is used, the physical length of the delay section of the delay line is sufficient for the measurement accuracy even at high frequencies such as the millimeter wave band. As the length becomes longer, accurate delay can be obtained with high accuracy, and more accurate and accurate calibration can be performed. Also according to this calibration method, the propagation constants extracted from the delay sections of these delay lines become accurate and accurate, and therefore, accurate transmission loss can be extracted and obtained.

According to the method for measuring the transmission loss of a high-frequency transmission line of the present invention, the scattering parameter when the measurement reference planes are directly connected by a transmission line having the same electrical length as the high-frequency transmission line to be measured. When the transmission loss of the high-frequency transmission line is determined by the TRL calibration method using the measured values and the measured values of the scattering parameters in a state where the measurement reference planes are connected via the delay line, a dielectric substrate is used as the delay line. Since a delay line having a line conductor formed thereon and having an electrical length longer than half the vacuum wavelength of the frequency to be measured is used, the delay portion of the delay line can be used for high frequencies such as the millimeter wave band. Physical length is sufficiently long for the accuracy of the measurement, so that accurate delay can be obtained with high accuracy and accurate propagation constant can be obtained, and more accurate and accurate Transmission loss Measurement becomes the thing done.

As described above, according to the present invention, the TRL calibration method used as a calibration method in high-frequency measurement, that is, in a state where the measurement reference planes are directly connected by a transmission line having the same electrical length as the high-frequency transmission line to be measured. With respect to the calibration method using the measured value of the above and the measured value in a state where the measurement reference plane is connected via a delay line, even for a high frequency such as a millimeter wave band, a decrease in accuracy is small and an accurate delay is obtained. Thus, a calibration standard for high-frequency measurement and a calibration method for high-frequency measurement capable of performing high-accuracy and high-accuracy calibration can be provided.

Further, according to the present invention, the propagation constant can be accurately and accurately extracted by the TRL calibration method even for a high frequency such as a millimeter wave band, and the transmission loss can be accurately extracted. And a method for measuring the transmission loss of the transmission line.

[Brief description of the drawings]

1 (a) to 1 (d) are plan views each showing an example of a calibration standard for high frequency measurement according to the present invention.

FIG. 2 is a diagram showing an example of a frequency characteristic curve of an attenuation constant α extracted by a calibration method and a measurement method of the present invention.

FIGS. 3A to 3D are TRs according to the present invention, respectively.
FIG. 9 is a plan view showing an example of a structure for connecting two terminals (between measurement reference planes) in the L calibration method.

FIG. 4 is a diagram showing an example of a frequency characteristic curve of an attenuation constant α extracted by a conventional TRL calibration method.

[Explanation of symbols]

1, 2, 4, 5, 7, 8, 10, 11 ... terminal (measurement reference plane) 3, 9, 12, 15, 17, 21, ... transmission line (line conductor) 14, 16, 18, 20: Dielectric substrate

Claims (3)

[Claims] 1. A TRL that uses a measured value of a scattering parameter in a state where measurement reference planes are directly connected by a high-frequency transmission line and a measured value of a scattering parameter in a state where measurement reference planes are connected via a delay line. A calibration standard for high-frequency measurement for calibration of high-frequency measurement on transmission characteristics of a high-frequency transmission line used for the calibration method, wherein the delay line is formed by forming a line conductor on a dielectric substrate, and A calibration standard for high-frequency measurement, wherein the electrical length of the delay section is longer than half the vacuum wavelength of the frequency to be measured. 2. A TRL that uses a measured value of a scattering parameter when the measurement reference planes are directly connected by a high-frequency transmission line and a measured value of the scattering parameter when the measurement reference planes are connected via a delay line. In the calibration method of the high-frequency measurement related to the transmission characteristics of the high-frequency transmission line by the calibration method, the electrical length of the delay unit is formed by forming a line conductor on a dielectric substrate as the delay line. A calibration method for high frequency measurement, characterized in that a delay line longer than half is used. 3. A transmission loss of a high-frequency transmission line, a measured value of a scattering parameter in a state where the measurement reference planes are directly connected by the high-frequency transmission line, and a state in which the measurement reference planes are connected via a delay line. A TRL calibration method using the measured values of the scattering parameters at step (a), wherein the delay line is formed by forming a line conductor on a dielectric substrate, and the electrical length of the delay unit is a vacuum of the frequency to be measured. A method for measuring a transmission loss of a high-frequency transmission line, wherein a delay line longer than half the wavelength is used.