JP2012013582A - Noise measurement cable and noise measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise measurement cable that is used in a WBFC method and suppresses a mismatch of characteristic impedance so as to prevent degrading in measurement sensitivity even when a distance between a measurement object and a bottom face of a case is changed.SOLUTION: The noise measurement cable 1 includes a line 10 for connecting the measurement object 120 and connectors 60 and 61 which are attached to positions lower than the measurement object 120 in height from the bottom face 111 of the case 110. The cable 10 is formed in a shape having wider line width as it becomes closer to the measurement object 120 from the connectors 60 and 61, that is more apart from the bottom face 111 of the case 110. An end of the line 10 is connected to the connectors 60 and 61 via five chip resistors 40 which are connected in parallel mutually.

Description

  The present invention relates to a noise measurement cable and a noise measurement device, and in particular, for measuring a common mode voltage generated between a casing and a measurement object by arranging the measurement object inside a conductive casing. The present invention relates to a noise measurement connection cable and a noise measurement apparatus using the noise measurement connection cable.

  In IEC (International Electrotechnical Commission), a work bench Faraday cage method (hereinafter referred to as “WBFC method”) that enables easy measurement of common mode noise without using a large-scale measurement field such as an anechoic chamber. (For example, see Patent Document 1). Here, in the WBFC method, a measurement object (EUT: Equipment Under Test) is placed in a conductive housing (WBFC), and the measurement object is operated with respect to the absolute reference potential of the housing. In this method, a common mode voltage (electromagnetic wave noise) generated at a reference potential of an object is measured by a measuring instrument provided outside the casing. The specification is defined in “IEC 62132-5”.

  In the WBFC method, an object to be measured is connected to a noise measurement connection cable that is a 150Ω transmission system, and is connected to a 50Ω measurement device via a 100Ω resistor for impedance conversion. At that time, in order to keep the characteristic impedance at a specified value (150Ω), IEC62132-5 specifies that the measurement object and the noise measurement cable are arranged at a height of 30 mm from the bottom of the housing.

JP 2003-307535 A

  By the way, when the size of the measurement object is increased, the capacitance formed between the measurement object and the bottom surface of the housing may increase, and the characteristic impedance may be lower than a specified value (150Ω). On the other hand, the distance between the measurement object and the bottom surface of the housing is increased so that the characteristic impedance becomes a specified value (150Ω), that is, the height of the measurement object is increased, and the measurement object and the bottom surface of the housing are increased. It is conceivable to reduce the capacitance formed between the two. However, when the height of the measurement object is increased, the end of the noise measurement cable that connects the measurement object and the connector attached to the housing is also lifted. Here, as described above, the noise measurement cable is designed so that the characteristic impedance becomes a specified value (150Ω) when the height from the bottom surface of the housing is 30 mm. For this reason, when one end of the noise measurement cable is lifted, the characteristic impedance of the noise measurement cable increases beyond 150Ω. As a result, characteristic impedance mismatch between the measurement object and the measurement sensitivity may be deteriorated.

  The present invention has been made to solve the above-described problems. A measurement object is arranged inside a conductive casing, and a common mode voltage generated between the casing and the measurement object is measured. This is a noise measurement cable that is used for this purpose, and even if the distance between the object to be measured and the bottom of the housing changes, the mismatch of characteristic impedance is suppressed and the deterioration of measurement sensitivity is suppressed. It is an object of the present invention to provide a noise measurement cable that can be used, and a noise measurement device using the noise measurement cable.

  The noise measurement cable according to the present invention is a noise measurement cable that is used to place a measurement object inside a conductive casing and measure a common mode voltage generated between the casing and the measurement object. A cable is provided with a conductive thin plate-like line that connects an object to be measured and a connector attached to the case, the distances from each other being different from the bottom surface of the case. The line width is formed so as to increase as the distance from the bottom surface increases.

  As described above, when the distance from the bottom surface of the measurement object is changed in order to suppress the change in the capacitance between the measurement object and the bottom surface of the housing, the noise measurement cable One end is lifted. Here, according to the noise measurement cable according to the present invention, the line connecting the measurement object and the connector as the distance from the bottom surface of the housing increases, that is, as the height from the bottom surface of the housing increases. Is formed so as to be wide. Therefore, the mismatch of the characteristic impedance of the noise measurement cable can be eliminated and the characteristic impedance can be adjusted to a specified value. As a result, even when the distance between the measurement object and the bottom surface of the housing changes, it is possible to suppress the deterioration of measurement sensitivity.

  In the noise measurement cable according to the present invention, the line connects the measurement object and a connector attached at a position closer to the bottom surface of the housing than the measurement object, and the measurement is performed from the connector. It is preferable that the line width is gradually increased as the object is approached.

  For example, as described above, when the distance between the bottom surface of the housing and the measurement object is increased in order to adjust the characteristic impedance of the measurement object having a large size to a specified value (150Ω) (that is, the measurement object When the height is increased), the characteristic impedance of the noise measurement cable increases from the specified value. Here, according to the noise measurement cable according to the present invention, the line width is gradually increased as the measurement object disposed at a higher position is approached. Therefore, the characteristic impedance can be adjusted to the specified value (150Ω) at any position of the noise measurement cable. As a result, it is possible to eliminate the degree of mismatch of characteristic impedance even for a measurement object having a large size, and to suppress deterioration in measurement sensitivity.

  In addition, the line has a width at one end that is the same length as one side of the object to be connected, and a width at the other end that is connected to the connector is 30 mm from the bottom surface of the housing. It is preferable that the characteristic impedance is formed to a length having a specified value and that both ends at one end and both ends at the other end are linearly connected.

  If it does in this way, characteristic impedance can be made to correspond to a regulation value in a connection end with a measuring object, and a connection end with a connector. In addition, since the ends of the connection end to the measurement object and the connection end to the connector are linearly connected, the characteristic impedance becomes a specified value (150Ω) at any position of the noise measurement cable. It becomes possible to set easily.

  The other end of the line is preferably connected to the connector via a plurality of chip resistors connected in parallel to each other.

  In this way, the characteristic impedance of the cable body can be specified. Further, since the chip resistor is small and leadless, the influence of the inductance on the characteristic impedance of the noise measurement cable can be reduced as compared with the insertion mounting type resistor having leads.

  In the noise measurement cable according to the present invention, the line may form a microstrip line having a specified characteristic impedance by a bottom surface of the housing and an air layer between the track and the bottom surface of the housing. preferable.

  In this way, it is possible to easily set the line width, that is, the characteristic impedance of the line by applying the microstrip line design method.

  A noise measuring device according to the present invention includes a conductive housing in which a measurement object is disposed, a connector attached to the housing, and any one of the noise measurement cables that connects the measurement object and the connector. It is characterized by providing.

  According to the noise measurement device of the present invention, since any one of the above noise measurement cables is provided, the noise measurement cable can be used even when the distance between the measurement object and the bottom surface of the housing changes. And the characteristic impedance of the measurement object can be adjusted to a specified value (150Ω). Therefore, it is possible to eliminate the degree of mismatch of characteristic impedance, and to suppress deterioration of measurement sensitivity.

  According to the present invention, in a noise measurement cable used for measuring a common mode voltage generated between a casing and a measuring object, the measuring object is placed inside a conductive casing. Even when the distance between the object and the bottom surface of the housing changes, it is possible to suppress mismatch in characteristic impedance and suppress deterioration in measurement sensitivity.

It is a longitudinal cross-sectional view which shows typically the structure of the noise measuring apparatus using the cable for noise measurement which concerns on embodiment. It is a top view which shows the structure of the cable for noise measurement which concerns on embodiment. It is a perspective view which shows typically the evaluation model using the noise measurement cable which concerns on embodiment used for the measurement of reflection amount. It is a perspective view which shows typically the evaluation model which concerns on the comparative example 1 used for the measurement of reflection amount. It is a perspective view which shows typically the evaluation model which concerns on the comparative example 2 used for the measurement of reflection amount. It is a graph which shows the measurement result of the reflection amount of the evaluation model which concerns on embodiment, and the evaluation model which concerns on the comparative example 1 and the comparative example 2. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  First, the configuration of the noise measurement cable 1 according to the embodiment and the configuration of the noise measurement device 100 using the noise measurement cable 1 will be described with reference to FIGS. 1 and 2 together. FIG. 1 is a longitudinal sectional view schematically showing a configuration of a noise measuring device 100 in which a noise measuring cable 1 is used. FIG. 2 is a plan view showing the configuration of the noise measurement cable 1.

  The noise measuring apparatus 100 includes two noise measuring cables 1 and 1 and a housing 110 that houses a measurement object 120 therein. Details of the noise measuring cable 1 will be described later. The housing 110 is a conductive housing formed of a metal material such as iron or copper, and a known WBFC can be used. The housing 110 is grounded, and the bottom surface 111 of the housing 110 is set to the system ground (reference potential).

  A measurement object 120 such as an electronic device or a circuit board is accommodated inside the housing 110 so as to be parallel to the bottom surface 111 of the housing 110. In IEC62132-5, the distance from the bottom surface 111 of the housing 110 to the measurement object 120, that is, the height from the bottom surface 111 on which the measurement object 120 is arranged is used to maintain the characteristic impedance at a specified value (150Ω). 30 mm. However, when the size of the measurement object 120 is large, the capacitance formed between the measurement object 120 and the bottom surface 111 of the housing 110 increases, and the characteristic impedance falls below a specified value (150Ω). As a result, a mismatch occurs between the connected 150Ω noise measurement cable. Therefore, as shown in FIG. 1, in the present embodiment, the height at which the measurement object 120 is arranged is increased (for example, 50 mm) so that the characteristic impedance is 150Ω, and the measurement object 120 and the bottom surface of the casing 110 are increased. The electrostatic capacitance formed between the two is lowered.

  One end of the first noise measurement cable 1 is connected to one reference potential portion (common mode point) 121 of the measurement object 120 by, for example, soldering or copper foil tape. The other end of the first noise measurement cable 1 is connected to a connector 60 attached to the side surface of the housing 110 via five chip resistors 40 connected in parallel to each other. Here, the connector 60 is attached to a position where the height from the bottom surface 111 of the housing 110 is 30 mm. Therefore, the height of the first noise measurement cable 1 that connects the measurement object 120 and the connector 60 from the bottom surface 111 of the housing 110 increases as the measurement object 120 approaches from the connector 60 side. It is arranged. Note that a 50 ohm termination resistor 130 is attached to the connector 60 outside the housing 110.

  One end of the second noise measurement cable 1 is connected to the other reference potential portion (common mode point) 122 of the measurement object 120 by, for example, soldering or copper foil tape. The other end of the second noise measurement cable 1 is connected to a connector 61 attached to the side surface of the housing 110 via five chip resistors 40 connected in parallel to each other. Here, the connector 61 is attached at a position where the height from the bottom surface 111 of the housing 110 is 30 mm. Therefore, the second noise measurement cable 1 that connects the measurement object 120 and the connector 61 is configured such that the height from the bottom surface 111 of the housing 110 increases as the measurement object 120 side approaches from the connector 61 side. It is arranged. Note that a measuring instrument (not shown) such as a network analyzer disposed outside the housing 110 is connected to the coaxial connector 61 through a coaxial cable 140.

  As described above, a loop is formed between the measurement object 120 and the housing 110 via the two noise measurement cables 1 and 1, and common mode noise (common mode voltage) flowing through the loop is measured. To the vessel. Note that a power cable, a signal cable, and the like are connected to the measurement object 120 as necessary so that the measurement object 120 can be operated in the housing 110.

  Next, the configuration of the noise measurement cable 1 will be described in detail. As described above, the noise measurement cable 1 is a noise measurement connection cable used in WBFC. More specifically, in the noise measurement cable 1, the measurement object 120 is disposed inside the conductive casing 110, and the measurement object 120 is operated with the measurement object 120 being operated. This is a connection cable used to connect the reference potential portions 121 and 122 of the measurement object 120 and the external termination resistor 130 or a measuring instrument when measuring a common mode voltage (noise) generated therebetween.

  The noise measuring cable 1 includes a thin plate-like line 10 having a rectangular cross section made of, for example, a metal material mainly composed of copper. One end of the line 10 is electrically connected to the measurement object 120 by, for example, soldering or copper foil tape, and the other end is connected to the casing 110 via five chip resistors 40 connected in parallel to each other. Are connected to connectors 60 and 61 attached to the side surfaces of

  As shown in FIG. 2, the line 10 is formed so that the line width gradually increases as it approaches the measurement object 120 from the connector 60, 61 side when viewed in plan. That is, the line 10 is formed in a trapezoidal shape (tapered shape). As described above, the noise measurement cable 1 is disposed such that the height from the bottom surface 111 of the housing 110 increases as the measurement object 120 side approaches from the connector 60 or 61 side. Therefore, the line 10 constituting the noise measurement cable 1 is formed such that the line width increases as the distance from the bottom surface 111 of the housing 110 increases (that is, the height from the bottom surface 111 increases). ing.

  More specifically, the line 10 has a line width at one end that is the same length as one side of the measurement object 120 to be connected. The line 10 has a characteristic impedance of a specified value (150Ω) when the line width of the other end connected to the connectors 60 and 61 is set to 30 mm, for example, with the distance from the bottom surface 111 of the housing 100. It is formed in length. Then, both end portions at one end of the line 10 and both end portions at the other end are linearly connected to form a trapezoidal line 10.

Here, the method for setting the line width of the line 10 will be described more specifically. The line 10 forms a microstrip line whose characteristic impedance is a specified value (150Ω) by the bottom surface 111 of the housing 110 and the air layer 20 between the line 10 and the bottom surface 111. The characteristic impedance Z ₀ of the microstrip line is obtained by the following equations (1), (2), (3), and (4), where W is the line width and h is the dielectric (air layer 20) thickness. Therefore, the line width W at which the characteristic impedance becomes the specified value (150Ω) can be calculated backward from the following formulas (1), (2), (3), and (4).

ただし、ε_ｒｅは実効比誘電率、ε_ｒは比誘電率である

However, ε _re effective dielectric constant, is ε _r is the relative dielectric constant

  Thus, by setting the line width of the line 10 based on the microstrip line theory, the characteristic impedance is adjusted so as to coincide with the specified value (150Ω) at any position of the line 10.

  Five chip resistors 40 connected in parallel to each other are connected to the other end of the line 10, and the line 10 is attached to the side surface of the housing 110 via these chip resistors 40. Connected to connectors 60 and 61. These chip resistors 40 are for specifying the characteristic impedance of the cable body, and the resistance value of each chip resistor 40 is set to 510Ω (and thus the combined resistance value is about 100Ω). The noise measurement cable 1 (line 10) is preferably supported by, for example, styrene foam. However, when the noise measurement cable 1 (line 10) has sufficient rigidity, a support member such as polystyrene foam may be omitted.

  When used in the WBFC, as described above, one end of the line 10 constituting the noise measurement cable 1 is soldered to the reference potential portions 121 and 122 of the measurement object 120 arranged inside the housing 110. It is connected with adhesive copper foil tape. On the other hand, the other end of the line 10 is connected to the connectors 60 and 61 attached to the side surface of the housing 110 via the chip resistor 40, and the termination resistor 130 outside the housing is connected via the connectors 60 and 61. Alternatively, it is connected to a measuring instrument (not shown) such as a network analyzer.

  In the WBFC method, common mode noise (common mode voltage) generated in the reference potential of the measurement target 120 with respect to the absolute reference potential of the casing 110 in a state where the measurement target 120 is operated in the sealed casing 110. ) Is measured by a measuring instrument provided outside the housing 110.

  Here, in order to evaluate the consistency of the characteristic impedance of the noise measurement cable 1 according to the present embodiment, the characteristic impedance is simulated by simulating the WBFC method and changing the width of the line and the size and height of the measurement object. The amount of reflection (S11) showing the consistency of was measured. Subsequently, referring to FIGS. 3 to 6 together, the characteristic impedance matching (reflection amount) of the noise measurement cable 1 according to the present embodiment and the noise measurement cables according to Comparative Example 1 and Comparative Example 2 are compared. The measurement results will be shown and described.

  An evaluation noise measurement device (evaluation model) used for the measurement of the reflection amount (S11) is shown in FIGS. 3 to 5, the side surface and the upper surface (lid portion) of the housing are omitted in order to make the internal configuration easy to see. FIG. 3 is a perspective view schematically showing an evaluation model in which the noise measurement cable 1 according to the embodiment is used. FIG. 4 is a perspective view schematically showing an evaluation model according to Comparative Example 1, in which a noise measurement cable with a constant line width is connected to a large measurement object. FIG. 5 is a perspective view schematically showing an evaluation model according to Comparative Example 2 in which a noise measurement cable having a constant line width is connected to a measurement object having an appropriate size.

  As shown in FIG. 3, in the evaluation model according to the embodiment, a rectangular measuring object 120 having a relatively large size and having a horizontal width of 31.3 mm and a vertical length of 30 mm was used. The measurement object 120 was placed at a height of 50 mm from the bottom surface 111 so that the theoretical value of the characteristic impedance was 150Ω. On the other hand, the connectors 60 and 61 were attached to a height of 20 mm from the bottom surface 111. Then, one end of the noise measurement cable 1 (line 10) formed of a copper plate is connected to the measurement object 120, and the other end is connected to each other in parallel so that the combined resistance value is about 100Ω. The connectors 60 and 61 were connected via the chip resistor 40. That is, the noise measurement cable 1 (line 10) is disposed so as to be inclined so that the height from the bottom surface 111 is 20 mm (connector end) to 50 mm (measurement object end). The noise measurement cable 1 (line 10) has a line width of 11.6 mm (connector end) to 31.3 mm (measurement object end) and a trapezoidal shape (tapered) with a length of 50 mm, and the theory of characteristic impedance. It formed so that a value might be set to 150Ω. Further, a 50Ω termination resistor 130 was connected to one connector 60, and a network analyzer (not shown) was connected to the other connector 61.

  As shown in FIG. 4, in the evaluation model according to Comparative Example 1, a rectangular measurement object 120 having a relatively large size and having a horizontal width of 31.3 mm and a vertical length of 30 mm was used. The measurement object 120 was placed at a height of 50 mm from the bottom surface 111 so that the theoretical value of the characteristic impedance was 150Ω. On the other hand, the connectors 60 and 61 were attached to a height of 20 mm from the bottom surface 111. Then, one end of a noise measurement cable (line) formed from a copper plate is connected to the measurement object 120, and the other end is connected to each other in parallel so that the combined resistance value is about 100Ω. The connectors 60 and 61 were connected via the container 40. That is, the noise measurement cable (line) is disposed so as to be inclined so that the height from the bottom surface 111 is 20 mm (connector end) to 50 mm (measurement object end). The noise measurement cable (line) was formed in a strip shape (the theoretical value of the characteristic impedance was 150Ω to 209Ω) with a constant line width of 11.6 mm and a length of 50 mm. Further, a 50Ω termination resistor 130 was connected to one connector 60, and a network analyzer (not shown) was connected to the other connector 61.

  As shown in FIG. 5, in the evaluation model according to Comparative Example 2, a rectangular measuring object 120 </ b> D having an appropriate size of 11.6 mm in width and 30 mm in length formed from a copper plate is measured from the bottom surface 111 to 20 mm. Arranged at a height (theoretical value of characteristic impedance is 150Ω). Further, the connectors 60 and 61 were attached to a height of 20 mm from the bottom surface 111. Then, one end of a noise measurement cable (line) formed from a copper plate is connected to the measurement object 120D, and the other end is connected to each other in parallel so that the combined resistance value is about 100Ω. The connectors 60 and 61 were connected via the container 40. The noise measurement cable (line) was formed in a strip shape (the theoretical value of the characteristic impedance was 150Ω) having a constant line width of 11.6 mm and a length of 50 mm. Further, a 50Ω termination resistor 130 was connected to one connector 60, and a network analyzer (not shown) was connected to the other connector 61.

  In the state of being connected as described above, S11 (reflection amount) of the S parameter was measured by a network analyzer, and the consistency of the characteristic impedance and the estimated measurement sensitivity were evaluated. S11 indicates a signal reflected to port 1 when a signal is input from port 1 (connector 61 on the network analyzer side), that is, a reflection coefficient of port 1.

  FIG. 6 shows the measurement results of the reflection amount (S11) of the evaluation model according to the embodiment described above and the evaluation models according to Comparative Example 1 and Comparative Example 2. The horizontal axis of the graph shown in FIG. 6 is the frequency (MHz), and the vertical axis is the reflection amount (S11). In the graph of FIG. 6, the measurement result (S11) of the evaluation model according to the embodiment is a solid line, the measurement result (S11) of the evaluation model according to Comparative Example 1 is a broken line, and the evaluation model measurement according to Comparative Example 2 is measured. The results (S11) are indicated by alternate long and short dash lines.

  As shown by the one-dot chain line in FIG. 6, in the comparative example 2 (see FIG. 5) in the matching state, the reflection amount is about −3.4 dB up to about 500 MHz (in terms of impedance (from the network analyzer side), about 250Ω). ), A substantially flat characteristic was obtained. That is, in Comparative Example 2, it is considered that the characteristic impedance is matched in the region up to about 500 MHz, and the measurement sensitivity is hardly deteriorated.

  On the other hand, as shown by a broken line in FIG. 6, in Comparative Example 1 (see FIG. 4) in which the size and height of the measurement target 120 </ b> D are changed with respect to Comparative Example 2, as a result of the mismatch in characteristic impedance, The amount of reflection started to increase from around 50 MHz, and the amount of reflection increased greatly in the region of 100 to 500 MHz than the result of Comparative Example 2 described above. Therefore, in Comparative Example 1, there is a possibility that the measurement sensitivity deteriorates in the high frequency region.

  As shown by a solid line in FIG. 6, in this embodiment (see FIG. 3), the amount of reflection in the vicinity of 100 to 500 MHz increased in Comparative Example 1 is suppressed, and although some resonance is seen, Comparative Example 2 Near flat characteristics were obtained. This is probably because the characteristic impedance mismatch was eliminated and the amount of reflection could be reduced by forming the line 10 (noise measurement cable 1) in a trapezoidal shape (tapered shape).

  From the above results, the noise measurement cable 1 (line 10) according to the present embodiment is a case where the size and height of the measurement object are changed compared to the noise measurement cable having a constant line width. It was confirmed that the degradation of measurement sensitivity can be suppressed.

  According to the present embodiment, the line 10 that connects the measurement object 120 and the connectors 60 and 61 as the distance from the bottom surface 111 of the housing 110 increases, that is, as the height from the housing bottom surface 111 increases. Is formed so as to be wide. Therefore, the mismatch of the characteristic impedance of the noise measuring cable 1 can be eliminated, and the characteristic impedance can be adjusted to the specified value (150Ω). As a result, even if the distance between the measurement object 120 and the housing bottom surface 111 is changed, it is possible to suppress deterioration in measurement sensitivity.

  As described above, when the distance between the housing bottom surface 111 and the measurement object 120 is increased in order to adjust the characteristic impedance of the large measurement object 120 to the specified value (150Ω) (that is, the measurement object). When the height of 120 is increased), the characteristic impedance of the noise measurement cable 1 increases from a specified value. Here, according to the present embodiment, the line width is gradually increased as the measurement object 120 is approached. Therefore, the characteristic impedance can be adjusted to the specified value (150Ω) at any position of the noise measurement cable 1. As a result, it is possible to eliminate the degree of mismatch of characteristic impedance even for the measurement object 120 having a large size, and to suppress deterioration in measurement sensitivity.

  According to this embodiment, the width | variety of the end of the track | line 10 connected with the measuring object 120 is formed in the same length (31.3 mm in an evaluation model) as the one side of the measuring object 120. Further, when the width of the other end connected to the connectors 60 and 61 is set such that the distance from the bottom surface 111 of the housing 110 is, for example, 30 mm (however, 20 mm in the evaluation model), the characteristic impedance is a specified value. And both ends at one end and both ends at the other end are linearly connected. Therefore, according to the present embodiment, the characteristic impedance can be matched to the specified value (150Ω) at the connection end with the measurement object 120 and the connection ends with the connectors 60 and 61. In addition, since the ends of the connection end with the measurement object 120 and the connection ends with the connectors 60 and 61 are linearly connected, the characteristic impedance is a specified value (any value) at any position of the noise measurement cable 1. 150Ω) can be easily set.

  According to this embodiment, since the five chip resistors 40 connected in parallel are connected to the other end of the line 10, the characteristic impedance of the cable body can be specified. Further, since the chip resistor 40 is small and leadless, it is possible to reduce the influence of the inductance on the characteristic impedance of the noise measurement cable as compared with the insertion-mounted resistor having leads. .

  According to the present embodiment, the line 10 forms a microstrip line whose characteristic impedance is a specified value (150Ω) by the bottom surface 111 of the housing 110 and the air layer 20 between the line 10 and the bottom surface 111. . Therefore, it is possible to easily set the line width, that is, the characteristic impedance of the line 10 by applying the microstrip line design method.

  According to the noise measurement apparatus 100 according to the present embodiment, since the noise measurement cable 1 described above is provided, even if the distance between the measurement target 120 and the housing bottom surface 111 is changed, the noise is measured. The characteristic impedance of the measurement cable 1 and the measurement object 120 can be adjusted to a specified value (150Ω). Therefore, it is possible to eliminate the degree of mismatch of characteristic impedance, and to suppress deterioration of measurement sensitivity.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, the shape, dimensions, material, arrangement, and the like of the track 10 and the measurement target 120 are not limited to the above embodiment. Further, the number of chip resistors 40 is not limited to five.

  In the above embodiment, the arrangement and shape of the track 10 are set based on the measurement object 120 and the distance between the track 10 and the bottom surface 111 of the housing 110, but the distance between the upper surface (lid portion) of the housing 110. May be taken into account. In the above embodiment, the measurement object 120 having a large size has been described as an example, but conversely, the measurement object 120 having a smaller size can also be applied.

DESCRIPTION OF SYMBOLS 1 Noise measuring cable 10 Line 20 Air layer 40 Chip resistor 60, 61 Connector 100 Noise measuring apparatus 110 Case 111 Bottom 120, 120D Measurement object

Claims (6)

A noise measurement cable used to place a measurement object inside a conductive housing and measure a common mode voltage generated between the housing and the measurement object,
A distance between the bottom surface of the housing is different from each other, and includes a thin plate-like line having conductivity to connect the measurement object and a connector attached to the housing,
The noise measurement cable, wherein the line is formed so that the line width increases as the distance from the bottom surface of the housing increases.   The track connects the measurement object and the connector installed at a position closer to the bottom surface of the housing than the measurement object, and approaches the measurement object from the connector. The noise measurement cable according to claim 1, wherein the cable is formed so that the line width gradually increases.   The line is formed such that the width of one end is the same length as one side of the measurement object to be connected, and the width of the other end connected to the connector is the distance from the bottom surface of the housing. When the length is set to 30 mm, the characteristic impedance is formed to a specified length, and both ends of the one end and both ends of the other end are linearly connected. Item 3. A noise measurement cable according to item 1 or 2.   The noise measurement cable according to claim 3, wherein the other end portion of the line is connected to the connector via a plurality of chip resistors connected in parallel to each other.   The said track | line forms the microstrip line | wire by which characteristic impedance becomes a regulation value with the bottom face of the said housing | casing, and the air layer between the said track | line and the bottom face of the said housing | casing, The 1st characteristic is characterized by the above-mentioned. 5. The noise measurement cable according to any one of 4 above. A conductive housing that places the measurement object inside;
A connector attached to the housing;
A noise measurement device comprising: the noise measurement cable according to claim 1, which connects the measurement object and the connector.

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