JP2010019865A - Frequency characteristic evaluating device, tdr waveform measuring instrument, and program for frequency characteristic evaluating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency characteristic evaluating device capable of calculating the frequency characteristic of a signal wire without the need for a special sample or a special signal generator. <P>SOLUTION: The device includes: input means (1) for setting waveform data on a time domain concerning an incident wave of staircase waveform to a signal wire that is to be measured and a reflected wave with respect to the incident wave; a storage section (2) in which the waveform data is stored; impulse response extracting means (6) for extracting an impulse response by time-differentiating waveform data on the incident and reflected waves in accordance with the waveform data; Fourier transform means (7) for calculating an amplitude distribution for each frequency of the waveforms of the incident and reflected waves by Fourier transform of the impulse response; reflection coefficient calculating means (8) for calculating a reflection coefficient by calculating an amplitude ratio for each frequency from the amplitude distribution of the waveforms of the incident and reflected waves; and frequency characteristic calculating means (4) for calculating the frequency characteristic of the characteristic impedance of the signal wire in accordance with the reflection coefficient. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a frequency characteristic evaluation apparatus for a signal wiring and a program for the frequency characteristic evaluation apparatus. The present invention relates to frequency dependence of printed wiring board characteristics, in particular, effective relative dielectric constant of the substrate material viewed from the wiring, and wiring characteristics. The present invention relates to a frequency characteristic evaluation apparatus for evaluating the frequency dependence of impedance and a program for the frequency characteristic evaluation apparatus.

  First, the basic dielectric constant measurement method and the principle of TDR measurement will be described. FIG. 16 is an image diagram of a strip line structure of a printed wiring board which is an example of a signal wiring that is a measurement target. This printed wiring board includes a ground conductor 11, a glass fiber 12 a, a resin 12 b, and a wiring conductor 13. A composite material of the glass fiber 12 a and the resin 12 b corresponds to the substrate dielectric material 12.

  FIG. 17 is a schematic diagram of a cavity resonator perturbation method which is one of the conventional methods for measuring relative permittivity. The container of the cavity resonator 21 is provided with a sample insertion hole 22 that is hollow inside. The dielectric constant is measured by inserting a sample piece 23 whose dielectric constant is to be measured into the sample insertion hole 22.

  Next, an outline of a dielectric constant measurement method using this apparatus will be described. First, the resonance frequency is measured in a complete cavity state where the sample piece 23 is not contained. Next, the resonance frequency is measured with the sample piece 23 placed in the sample insertion hole 22. In a state where the sample is put, the resonance frequency is slightly shifted because the dielectric constant is different from that of the surrounding cavity only by the portion of the sample piece 23. Since the dimension of the sample piece 23 is known, the dielectric constant of the sample piece 23 can be calculated from the deviation of the resonance frequency.

  FIG. 18 is an image diagram of TDR (Time Domain Reflection) measurement generally used for measuring the characteristic impedance of the wiring. The TDR waveform measuring instrument 31 as a measuring device includes an internal signal source 32 that generates a voltage waveform, a waveform observation position 33, and a waveform display screen 34 that displays the waveform at the waveform observation position. A signal from the internal signal source 32 is sent to the transmission line 37 to be measured via the waveform observation position 33, the cable 35, and the probe 36.

  FIG. 19 is an image diagram of a waveform observed at the waveform observation position 33 when the transmission line 37 is measured by the TDR waveform measuring device 31. This waveform is roughly divided into three regions (a) to (c) with time. A region (a) shows a voltage waveform generated by reflection from the cable 35 after the voltage step output from the TDR waveform measuring device 31. In the region (b), a voltage waveform generated by reflection from the transmission line 37 to be measured after a step caused by mismatch between the characteristic impedance of the cable 35 and the impedance of the transmission line 37 to be measured at the position of the probe 36 is shown. Show.

  Further, the region (c) was generated due to a mismatch between the impedance of the transmission line 37 to be measured and the open end impedance (insulation), which occurred at the open end of the transmission line 37 to be measured that was not probed. The voltage waveform which arises by the total reflection from the transmission line open end after a level | step difference is shown.

  Next, the operations of FIGS. 18 and 19 will be described. The TDR waveform measuring instrument 31 generates a staircase waveform whose voltage changes sharply from 0 V to 2 V, for example, by the internal signal source 32. Since this staircase waveform is output to the 50Ω cable 35 ahead through the output impedance 50Ω, the voltage of the staircase waveform at the waveform measurement position 33 is divided by 1: 1 to 1V. After the time for reciprocating the cable 35 (corresponding to the time indicated by the area (a) in FIG. 19) has elapsed, reflection from the transmission line 37 to be measured continues for the time corresponding to the reciprocation of the transmission line 37 ( (Corresponding to the time indicated by the area (b) in FIG. 19).

  At this time, if the characteristic impedance of the cable is different from the impedance to be measured, a step is generated in the voltage value (corresponding to the step between the regions (a) and (b) in FIG. 19). Further, when a time corresponding to the round trip of the measurement target (corresponding to the time shown in the region (b) in FIG. 19) has elapsed, total reflection from the open end on the non-probe side of the measurement target appears thereafter (FIG. 19 (corresponding to the time indicated by the area (c) in FIG. 19). The step of the voltage value at this time (corresponding to the step between the regions (b) and (c) in FIG. 19) is approximately twice the voltage of the reflection from the cable or measurement target when the measurement target is 50Ω. It becomes close to 2V of the internal signal source of TDR.

  In FIG. 18, the cable 35 and the transmission line 37 to be measured are connected via the probe 36, but may be connected via a connector. In this case, if the impedance inside the probe 36 or the connector is different from the characteristic impedance of the cable 35, a finer voltage value at the level difference between the regions (a) and (b) in FIG. However, it is omitted in FIG.

  Next, the principle of obtaining the effective relative dielectric constant based on the measurement result of such a voltage waveform will be described. If the time for the signal to reciprocate inside the measurement target is 2 × Td, the relationship between the velocity C of the electromagnetic wave and the wiring length L is expressed by the following equation (1).

Here, there is a relationship of the following equation (2) between the velocity C of the electromagnetic wave traveling in the effective relative permittivity ε _ref and the velocity Co of the light in the vacuum.

  By substituting the velocity C according to the equation (2) into the equation (1), the following equation (3) is obtained.

Therefore, by solving the above equation (3) for the effective relative permittivity ε _ref , the effective relative permittivity ε _ref becomes the following equation (4).

Next, the principle of obtaining the impedance using this waveform will be described. When the cable impedance is Z _Cable and the measurement target impedance is Z _DUT , the reflection coefficient Γ at the connection position of the wave from the cable to the measurement target is expressed by the following equation (5).

A reflected wave of V _Cable × Γ is generated with respect to the voltage V _Cable at the cable. For this reason, the observed voltage V _DUT is expressed by the following equation (6).

When the above equation (6) is calculated backward, the impedance Z _{DUT to be} measured becomes the following equation (7), and the impedance Z _DUT of the transmission line 37 to be measured can be obtained based on the measurement result.

  As described above, the effective relative permittivity can be obtained from the relationship between the transit time by the TDR waveform measuring instrument and the wiring length, but this method has the following problems. A first problem is that the voltage change portion of the TDR waveform has a slope, so that the round-trip time at the measurement target cannot be determined accurately. A second problem is that a change due to frequency cannot be obtained, and there is a problem that it is unclear at which frequency the calculated value is originally.

  Further, the characteristic impedance measurement of the wiring by the TDR waveform measuring device has the following problems. The third problem is that the change in the staircase waveform is a gradual change from the middle, it is unclear which part is the end point of reflection, the voltage value differs depending on the time used for the calculation, and the calculation result also differs. It is done. A fourth problem is that the frequency dependence of the characteristic impedance cannot be obtained because the reflected waveform amplitude on the time axis is used for the calculation.

  In particular, with respect to the fourth problem, there is a method of obtaining the frequency dependence of the characteristic impedance by using a pulse wave or a sine wave as a signal source (for example, see Non-Patent Documents 1 and 2). As a result, the frequency-dependent characteristic impedance of the wiring can be obtained.

Fumihiro Tanji, Takemi Sakube, Takehiro Takahashi, Noboru Shibuya, “Development of characteristic impedance measurement method by TDR method using sine wave,” Proceedings of 17th Electronics Packaging Conference, pp.89-90, Tokyo, March 2003 J-H. Kim and D-H. Han, “Hybrid Method for Frequency-Dependent Lossy Coupled Transmission Line Characterization and Modeling,” IEEE 12th Topical Meeting on Electrical Performance of Electronic Packaging, pp. 239-242, Princeton, New Jersey, October 27-29, 2003

  However, the prior art has the following problems. There are the following problems in applying the conventional relative dielectric constant measurement method to a printed wiring board. First, as a first problem, a general substrate dielectric material is a composite material of glass fiber and resin, and the composite ratio and the temperature and pressure in the substrate manufacturing process vary depending on the manufacturer of the substrate and are the same. Even if the material is used, there is a difference in the characteristics of the finished substrate. For this reason, grasping the substrate characteristics requires not a material evaluation but a sample evaluation as a substrate in the same state as that actually used after the substrate manufacturing process. As a result, this sample evaluation is a major limitation in applying the relative dielectric constant measurement method to a printed wiring board.

  A second problem is that the glass fiber has a non-uniform thickness because of the braided structure. Therefore, the effective relative permittivity for the wiring changes depending on the positional relationship between the glass fiber and the wiring (H. Deck, S. Hall, B. Horine, K. Mallory, and T. Wig, “Impact of FR4 Dielectric Non Uniformity on the Performance of Multi-Gb / s Differential Signals, "IEEE 12th Topical Meeting on Electrical Performance of Electronic Packaging, pp. 243-246, Princeton, New Jersey, October 27-29, 2003.). However, the conventional measurement method has a problem that such local bias cannot be seen.

  The third problem is that the results differ depending on other measurement methods such as the capacitance method, bridge method, triplate resonance method, etc. "" Electronic Packaging Society Society Build-up Wiring Version Study Group Public Study Group "In-vehicle Wiring Version Technology Issues and Prospects", pp. 3-5, January 2004).

  Further, the conventional method for obtaining the frequency-dependent characteristic impedance of the wiring using a pulse wave or a sine wave as a signal source has a problem that the applicable frequency is low or a special signal generator is required for measurement.

  The present invention has been made to solve the above-described problems, using a wiring material manufactured by the same process as the final product without requiring a special sample, and requiring a special signal generator. Instead, the object is to provide a frequency characteristic evaluation apparatus and a program for the frequency characteristic evaluation apparatus that can calculate the frequency characteristic of the signal wiring over a wide frequency range.

  The frequency characteristic evaluation apparatus according to the present invention is a frequency characteristic evaluation apparatus for signal wiring, and is an input means for setting time domain waveform data relating to an incident wave of a staircase waveform and a reflected wave with respect to the incident wave with respect to the signal wiring to be measured. And a storage unit for storing the waveform data set by the input means, and an impulse response extraction for extracting the impulse response by time-differentiating the waveform data of the incident wave and the reflected wave based on the waveform data stored in the storage unit Means, Fourier transform means for Fourier transform of the impulse response to obtain the amplitude distribution for each frequency of the waveform of the incident wave and reflected wave, and calculating the amplitude ratio for each frequency from the amplitude distribution for the waveform of the incident wave and reflected wave Reflection coefficient calculation means for obtaining the reflection coefficient, and a frequency for calculating the frequency characteristic of the characteristic impedance of the signal wiring based on the reflection coefficient It is obtained by a characteristic calculation means.

  According to the present invention, by using the wiring material manufactured by the same process as the final product without requiring a special sample by calculating the frequency characteristics of the signal wiring based on the comparison result of a plurality of input data. Also, it is possible to provide a frequency characteristic evaluation apparatus and a program for the frequency characteristic evaluation apparatus that can easily calculate the frequency characteristic of a measurement object over a wide frequency range without requiring a special signal generator. Can do.

It is a block diagram of the frequency characteristic evaluation apparatus in Embodiment 1 of this invention. It is the flowchart which showed a series of processes which calculate an effective dielectric constant from the data of the S parameter measured value of the signal transmission line in Embodiment 1 of this invention. It is a figure which shows the passage phase obtained after TRL calibration in Embodiment 1 of this invention. It is a figure which shows the continuous description passage phase in Embodiment 1 of this invention. It is a graph of the frequency vs. effective relative dielectric constant real part in Embodiment 1 of the present invention. It is the flowchart which showed a series of processes which calculate an effective relative dielectric constant from the data of the S parameter measured value of the signal transmission line in Embodiment 2 of this invention. It is the flowchart which showed a series of processes which calculate an effective relative dielectric constant from the data of the S parameter measured value of the signal transmission line in Embodiment 3 of this invention. It is the flowchart which showed a series of processes which calculate an effective relative dielectric constant from the data of the S parameter measured value of the signal transmission line in Embodiment 4 of this invention. It is a block diagram of the frequency characteristic evaluation apparatus in Embodiment 5 of this invention. It is a flowchart of the process which calculates the frequency dependence characteristic impedance in Embodiment 5 of this invention. It is an image figure of the incident staircase wave and reflected staircase wave which are the waveform data in Embodiment 5 of this invention. It is an image figure of the impulse response of the incident staircase wave in Embodiment 5 of this invention, and the impulse response of a reflected staircase wave. It is a flowchart of the process which calculates the frequency dependence impedance in Embodiment 6 of this invention. It is waveform data in Embodiment 6 of this invention, and is an image figure of the TDR waveform when not connecting the probe tip for performing TDR measurement to a measuring object, and the TDR waveform when connecting to a measuring object. FIG. 10 is an impulse response according to the sixth embodiment of the present invention, and is an image diagram of an impulse response of a TDR waveform when a probe tip for performing TDR measurement is not connected to a measurement target and an impulse response of a TDR waveform when connected to the measurement target. is there. It is an image figure of the stripline structure of the printed wiring board which is an example of the signal wiring which is a measuring object. It is the schematic of the cavity resonator perturbation method which is one of the conventional dielectric constant measuring methods. It is an image figure of TDR (Time Domain Reflection) measurement generally used to measure the characteristic impedance of wiring. It is an image figure of the waveform observed at a waveform observation position when measuring a transmission line with a TDR waveform measuring instrument.

  Hereinafter, preferred embodiments of the frequency characteristic evaluation apparatus and the frequency characteristic evaluation apparatus program of the present invention will be described with reference to the drawings. In the embodiment of the present application, a printed wiring board as shown in FIG. 16 will be described as an example of the signal wiring to be measured. However, the signal wiring is not limited to the printed wiring board, and other signals are used. The same applies to wiring.

  The frequency characteristic evaluation device and the program for the frequency characteristic evaluation device of the present invention are passed based on input data including each wiring length for a wiring having a different length of the signal wiring to be measured, and S parameter measurement values of each wiring. By calculating the phase, the frequency-dependent effective relative permittivity of the dielectric surrounding the signal wiring to be measured can be calculated, and the input waveform of the incident staircase wave and the reflected staircase wave of the signal wiring to be measured By calculating the reflection coefficient based on the data, a frequency characteristic evaluation apparatus and a program for the frequency characteristic evaluation apparatus that can calculate the frequency dependent characteristic impedance of the measurement object are obtained.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a frequency characteristic evaluation apparatus according to Embodiment 1 of the present invention. The frequency characteristic evaluation apparatus of FIG. 1 includes an input unit 1, a storage unit 2, a passing phase difference calculation unit 3, a frequency characteristic calculation unit 4, and a result output display unit 5.

  The input means 1 is means for setting input data necessary for calculating the frequency characteristics of the printed wiring board to be measured. The storage unit 2 is a storage unit that stores input data, and the input unit 1 stores the set input data in the storage unit 2. The passing phase difference calculating means 3 is a means for calculating a passing phase difference between wirings having different lengths in the printed wiring board to be measured based on the input data stored in the storage unit 2.

  The frequency characteristic calculating unit 4 obtains a phase constant by dividing the passing phase difference calculated by the passing phase difference calculating unit 3 by the difference between the wiring lengths stored in the storage unit 2, and based on the obtained phase constant. This is means for calculating the frequency characteristic of the effective relative permittivity of the printed wiring board. Furthermore, the result output display means 5 is a means for outputting and displaying the frequency characteristic calculated by the frequency characteristic calculation means 4 to the outside.

  The frequency characteristic calculation processing by the input unit 1, the passing phase difference calculation unit 3, the frequency characteristic calculation unit 4, and the result output display unit 5 shown in FIG. 1 is realized by program processing by a computer having the storage unit 2. Is possible.

  Next, details of calculating the frequency characteristic of the effective relative permittivity of the printed wiring board to be measured by the frequency characteristic evaluation apparatus configured as described above will be described using a flowchart. FIG. 2 is a flowchart showing a series of processes for calculating the effective relative permittivity from the data of the S parameter measurement values of the signal transmission line according to the first embodiment of the present invention.

First, the input unit 1 accepts selection of which of the five types of data to be input (step S201). In the example of FIG. 2, the user, have a form for inputting a number i, i = 1 to 5, respectively, the input of the wiring length L _A of the wiring A, the input of the wiring length L _B of the wiring B , TRL (Through-Reflection-Line) calibration data input, wiring A S-parameter measurement value input, and wiring B S-parameter measurement value input. The input unit 1 accepts data input corresponding to each data type according to this number (steps S202 and S203), and stores the set input data in the storage unit 2.

  When the data input corresponding to the selected type is completed, the input unit 1 then checks whether all five types of data have been input (step S204). If there is data that has not been input, the input unit 1 returns to the process of step S201 and repeats a series of data input processes for the uninput data. On the other hand, when all the data has been input, the input unit 1 confirms whether to change the already input data (step S205).

  When changing the data, the input unit 1 returns to the process of step S201 and repeats a series of data input processes for the number desired to be changed, thereby accepting the correction of the data that needs to be changed, and the corrected input data Is stored in the storage unit 2. On the other hand, when all the data are available and it is not necessary to change these data, five types of input data are determined and the process proceeds to the next calculation phase.

When the five types of data are determined, the passing phase difference calculating means 3 next takes out the S parameter measurement values of the wiring A and the wiring B from the storage unit 2 and calculates the S parameter measurement values of the wiring A and the wiring B. TRL calibration is performed to determine the passing phases θ _A and θ _B (step S206). FIGS. 3A and 3B are diagrams showing the passing phase obtained after TRL calibration in the first embodiment of the present invention. FIG. 3A shows the passing phase θ _A of the wiring _A , and FIG. 3B shows the passing phase of the wiring B. θ _B is shown respectively.

The passing phases θ _A and θ _B in FIGS. 3A and 3B are both sawtooth graphs expressed in the range of −180 degrees to +180 degrees. Therefore, the passing phase difference calculating means 3 converts these passing phases θ _A and θ _B into continuous notation passing phases θ _CA and θ _CB having values continuous from 0 degree (step S207). FIG. 4 is a diagram showing a continuous notation passing phase in the first embodiment of the present invention.

Further, the passing phase difference calculating means 3 calculates the difference θ _diff between these two consecutively described passing phases θ _CA and θ _CB , and the wiring length L _A of the wiring _A and the wiring length L _{B of the} wiring B from the storage unit 2. _Are extracted, and a wiring length difference L _diff is calculated (step S208).

Next, the frequency characteristic calculation unit 4 calculates a phase constant β that is a phase per unit length by dividing the passing phase difference θ _diff by the wiring length difference L _diff (step S209). Furthermore, the frequency characteristic calculation means 4 calculates the effective relative dielectric constant ε _ref for each frequency f at the electromagnetic wave velocity C using the phase constant β (step S210). Then, the result output display means 5 displays / outputs the effective relative dielectric constant ε _ref for each frequency of the printed wiring board obtained by the frequency characteristic calculation means 4 (step S211).

Here, the formula for determining the effective dielectric constant epsilon _reff described in step S210. The velocity C of the electromagnetic wave passing through the effective relative dielectric constant ε _ref is expressed by the following equation (8).

  The wavelength λ [m] at this time is expressed by the following equation (9) with respect to the frequency f [Hz].

Further, since the wiring length L is (L / λ) periods of the wavelength λ, the passing phase θ _C is expressed by the following equation (10).

By substituting equation (9) into λ of equation (10), the passing phase θ _C becomes the following equation (11).

To _summarize this, the effective relative dielectric constant ε _ref is _expressed by the following equation (12).

  As described above, in the first embodiment, by using the data of the S parameter measurement value of the signal transmission line and using the above equation (12), it is possible to calculate the frequency versus effective relative dielectric constant for the transmission line. It becomes. FIG. 5 is a graph of the real part of the effective relative dielectric constant versus frequency in the first embodiment of the present invention, and shows an example of the effective relative dielectric constant calculated corresponding to the change in frequency.

In Expression (12), by setting the passing phase θ _C as the passing phase difference θ _diff and L as the wiring length difference L _diff , the effective relative dielectric constant ε _ref can be obtained in step S210 described above. In FIG. 2, the phase constant β is calculated in step S209. However, the effective relative permittivity ε _ref may be directly calculated by the following equation (13) without calculating the phase constant β. Absent.

  In the first embodiment, [degree] is used as the phase unit, but it may be in radians. In the case of radians, 360 in the formula is 2π.

  According to the first embodiment, the frequency of the substrate dielectric is determined based on the input data of each wiring length, TRL calibration data, and S parameter measurement value of each wiring for the wirings of different lengths of the printed wiring board to be measured. The dependent effective relative permittivity can be calculated.

Embodiment 2. FIG.
In the second embodiment, another processing procedure for calculating an effective relative permittivity from data of S parameter measurement values of a signal transmission line will be described. FIG. 6 is a flowchart showing a series of processes for calculating the effective relative permittivity from the data of the S parameter measurement values of the signal transmission line according to the second embodiment of the present invention.

  Compared with FIG. 2 which is the flowchart of the first embodiment, in the flowchart of FIG. 6, the number of types of input data is changed from five to four (corresponding to step S601), and Gating instead of TRL calibration processing. The difference is that processing is performed (corresponding to steps S602 and S603). Other processes are common to the first and second embodiments, and steps S201, S202, S204, S205, and S207 to S211 in FIG. 6 correspond to this common process. The configuration of the frequency characteristic evaluation apparatus according to the second embodiment is the same as that of FIG. 1 that is the configuration of the first embodiment.

Next, according to the flowchart of FIG. 6, a flow of a series of processes will be described focusing on differences from the flowchart of FIG. In the second embodiment, since TRL calibration processing is not performed, it is not necessary to input TRL calibration data in the data input phase. Therefore, the input means 1 corresponds to the numbers i = 1 to 4, respectively, the wiring length L _{A of} the wiring _A , the wiring length L _{B of} the wiring _B , the S parameter measured value of the wiring A, and the S parameter of the wiring B, respectively. Four types of data input of measurement values are received (step S601), and the set input data is stored in the storage unit 2.

  The set S parameter measurement values of the wiring A and the wiring B include multiple reflections. Therefore, the passing phase difference calculation means 3 once converts the S parameter measurement value, which is data in the frequency domain, into a time axis so that the first passing wave can be distinguished from other reflections. Only the passing wave is extracted by Gating, and the extracted first passing wave is converted again into the frequency domain (steps S602 and S603). Thereby, the passing phase in each wiring from which multiple reflection is removed can be obtained. After the respective passing phases are obtained, the processing in steps S207 to S211 is performed as in the first embodiment, and the description thereof is omitted.

As in the first embodiment, the effective relative permittivity ε _ref may be calculated directly by the above equation (13) without calculating the phase constant β. In the second embodiment, [degree] is used as the phase unit, but it may be in radians. In the case of radians, 360 in the formula is 2π.

  According to the second embodiment, the first passing wave is extracted and multiplexed based on the input data of the wiring lengths of the different lengths of the printed wiring board to be measured and the S parameter measurement values of the wirings. By calculating the passing phase with the reflection removed, the frequency-dependent effective relative permittivity of the substrate dielectric can be calculated without requiring TRL calibration data.

Embodiment 3 FIG.
In the third embodiment, another processing procedure for calculating the effective relative permittivity from the data of the S parameter measurement value of the signal transmission line will be described. FIG. 7 is a flowchart showing a series of processes for calculating the effective relative permittivity from the data of the S parameter measurement values of the signal transmission line according to the third embodiment of the present invention. In the third embodiment, a method capable of calculating the effective relative permittivity with high accuracy even when the phase data includes a certain deviation will be described.

  Compared with FIG. 2 which is the flowchart of the first embodiment, the calculation of the effective relative permittivity (corresponding to step S701) is different in the flowchart of FIG. Other processes are common to the first and third embodiments, and steps S201 to S209 and S211 in FIG. 7 correspond to this common process. The configuration of the frequency characteristic evaluation apparatus according to the third embodiment is the same as that of FIG. 1 that is the configuration of the first embodiment.

Next, formulas for _{obtaining the} effective relative dielectric constant ε _ref in step S701 in FIG. 7 will be described. In general, in the equation (12) shown above, if the phase data includes a certain deviation (constant term Δθ), this deviation is directly reflected in the calculation result. In this case, the relationship of the following equation (14) is established from the equation (11) shown above.

  When these two sides are differentiated by the frequency f, the following equation (15) is obtained, and the constant shift (constant term Δθ) of the phase data disappears.

On the right side of the above equation (15), the first term is df / df = 1, whereas the second term is d√ (ε _ref ) / df << 1, and the above equation (15) 16).

Thereby, the effective relative dielectric constant ε _ref is obtained by the following equation (17).

  When the right side of the equation (17) is expressed using the phase constant β, the following equation (18) is obtained.

Therefore, the frequency characteristic calculation means 4 uses the above equation (18) including the phase constant differential value (dβ / df), so that even when the phase data includes a certain deviation, the influence of the deviation is affected. Without this, it is possible to calculate the effective dielectric constant versus frequency for the transmission line. In FIG. 7, the phase constant β is calculated in step S209. However, the effective relative dielectric constant ε _ref is calculated directly by the equation (17) shown above without calculating the phase constant β. It doesn't matter. In Embodiment 3, [degree] is used as the unit of phase, but it may be in radians. In the case of radians, 360 in the formula is 2π.

  According to the third embodiment, the phase data is constant based on the input data of each wiring length, TRL calibration data, and S parameter measurement value of each wiring with respect to the wiring of different length of the printed wiring board to be measured. Even when a deviation is included, the frequency-dependent effective relative dielectric constant of the substrate dielectric can be calculated without being affected by the deviation.

Embodiment 4 FIG.
In the fourth embodiment, another processing procedure for calculating the effective relative permittivity from the data of the S parameter measurement values of the signal transmission line will be described. FIG. 8 is a flowchart showing a series of processes for calculating the effective relative permittivity from the data of the S parameter measurement values of the signal transmission line according to the fourth embodiment of the present invention. In the fourth embodiment, a method for accurately calculating an effective relative dielectric constant without requiring TRL calibration data when phase data includes a certain deviation will be described.

  Compared to FIG. 6 which is the flowchart of the second embodiment, the calculation of the effective relative permittivity (corresponding to step S701) is different in the flowchart of FIG. Other processes are common to the second and fourth embodiments, and steps other than step S701 in FIG. 8 correspond to this common process. The method for calculating the effective relative permittivity in step S701 is the same as that described in the third embodiment.

  The configuration of the frequency characteristic evaluation apparatus in the fourth embodiment is the same as that of FIG. 1 which is the configuration of the first embodiment, and the frequency characteristic calculation means 4 uses the equation (18) described in the third embodiment. By using it, it is possible to calculate the frequency versus effective relative permittivity for the transmission line even when the phase data includes a certain deviation.

In FIG. 7, the phase constant β is calculated in step S209. However, the effective relative permittivity ε _ref is calculated directly by the equation (17) shown above without calculating the phase constant β. It doesn't matter. In this embodiment, [degree] is used as the unit of phase, but it may be in radians. In the case of radians, 360 in the formula is 2π.

  According to the fourth embodiment, the first passing wave is extracted and multiplexed based on the input data of the wiring lengths of the different lengths of the printed wiring board to be measured and the S parameter measurement values of the wirings. By calculating the passing phase without reflection, the frequency dependent effective relative dielectric constant of the substrate dielectric can be calculated even when the TRL calibration data is not required and the phase data includes a certain deviation. Can be calculated.

Embodiment 5 FIG.
In the first to fourth embodiments, the case where the frequency-dependent effective relative dielectric constant is obtained as one of the frequency characteristics of the printed wiring board to be measured has been described. In the fifth embodiment, a case will be described in which frequency-dependent characteristic impedance is calculated as one of frequency characteristics of a printed wiring board to be measured.

  FIG. 9 is a configuration diagram of a frequency characteristic evaluation apparatus according to Embodiment 5 of the present invention. The frequency characteristic evaluation apparatus shown in FIG. 9 includes an input unit 1, a storage unit 2, an impulse response extraction unit 6, a Fourier transform unit 7, a reflection coefficient calculation unit 8, a frequency characteristic calculation unit 4, and a result output display unit 5. Compared with FIG. 1 showing the configuration of the frequency characteristic evaluation apparatus for obtaining the effective relative permittivity, the frequency characteristic evaluation apparatus of FIG. 9 is means for performing intermediate processing between the input means 1 and the frequency characteristic calculation means 4. The difference is that, instead of the passing phase difference calculating means 3, an impulse response extracting means 6, a Fourier transform means 7, and a reflection coefficient calculating means 8 are newly used.

  The input means 1 is means for setting waveform data of incident waves and reflected waves necessary for calculating the frequency characteristics of the printed wiring board to be measured. The storage unit 2 is a storage unit that stores waveform data, and the input unit 1 stores the set waveform data in the storage unit 2.

  The impulse response extracting means 6 is means for extracting an impulse response by differentiating each waveform data with respect to time based on the waveform data stored in the storage unit 2. The Fourier transform means 7 is a means for obtaining an amplitude distribution for each frequency of each waveform by Fourier transforming the extracted impulse response. Further, the reflection coefficient calculating means 8 is a means for calculating the reflection coefficient by calculating the amplitude ratio for each frequency from the amplitude distribution obtained for each waveform.

  The frequency characteristic calculation unit 4 is a unit that calculates the frequency characteristic of the characteristic impedance of the printed circuit board based on the reflection coefficient calculated by the reflection coefficient calculation unit 8. Furthermore, the result output display means 5 is a means for outputting and displaying the frequency characteristic calculated by the frequency characteristic calculation means 4 to the outside.

  The frequency characteristic calculation processing by the input means 1, impulse response extraction means 6, Fourier transform means 7, reflection coefficient calculation means 8, frequency characteristic calculation means 4, and result output display means 5 shown in FIG. 2 can be realized by a program process by a computer having 2.

  Next, details of calculating the frequency characteristic of the characteristic impedance of the printed wiring board to be measured by the frequency characteristic evaluation apparatus configured as described above will be described using a flowchart. FIG. 10 is a flowchart of processing for calculating frequency-dependent characteristic impedance according to the fifth embodiment of the present invention.

  First, the input unit 1 accepts selection of which of two types of data to be input is input (step S1001). In the example of FIG. 10, the user has a format for inputting the number i, and i = 1 and 2 are respectively used for inputting incident staircase waveform data and reflecting staircase waveform data. Correspond. The input unit 1 accepts waveform data input corresponding to each data type according to this number (steps S1002 and S1003), and stores the set waveform data in the storage unit 2.

  FIG. 11 is an image diagram of incident staircase waves and reflected staircase waves, which are waveform data according to the fifth embodiment of the present invention. FIG. 11A shows the voltage value of the incident staircase wave, and FIG. 11B shows the voltage value of the reflected staircase wave, which are shown as functions in the time domain.

  When the input of the waveform data corresponding to the selected type is completed, the input unit 1 next checks whether or not all the two types of data have been input (step S1004). If there is data that has not been input, the input unit 1 returns to the process of step S1001 and repeats a series of data input processes for uninput waveform data. On the other hand, if all the waveform data has been input, the input means 1 confirms whether or not to change the already input waveform data (step S1005).

  When changing the waveform data, the input unit 1 returns to the process of step S1001 and repeats a series of waveform data input processes for the number desired to be changed, thereby accepting and correcting the waveform data that needs to be changed. The waveform data is stored in the storage unit 2. On the other hand, when all the waveform data are available and there is no need to change these waveform data, two types of input data are determined and the process proceeds to the next calculation phase.

  When the two types of data are determined, next, the impulse response extraction means 6 takes out the two types of waveform data from the storage unit 2, and calculates the impulse response by differentiating the two types of waveform data with respect to time (step S1006). . FIG. 12 is an image diagram of an impulse response of an incident staircase wave and an impulse response of a reflected staircase wave according to Embodiment 5 of the present invention. FIG. 12 (a) shows the voltage change rate of the incident staircase wave, and FIG. 12 (b) shows the voltage change rate of the reflected staircase wave as a function in the time domain. FIG. 11 (a) and FIG. Is equivalent to the time-differentiated waveform.

  Further, the impulse response extraction means 6 performs gating on the time axis for these impulse responses, and extracts only data in a narrow time axis range including the impulse (step S1007). This extraction can be performed by extracting the vicinity of time = 0 in FIGS. 12 (a) and 12 (b). This eliminates the effects of multiple reflections. Next, the Fourier transform means 7 transforms the extracted impulse response on the time axis into a frequency distribution by Fourier transform (step S1008).

  Next, the reflection coefficient calculation unit 8 calculates the ratio of the two frequency distributions converted by the Fourier transform unit 7 (step S1009). This ratio is equal to the reflection coefficient Γ for each frequency. Next, the frequency characteristic calculation unit 4 calculates the impedance for each frequency using the obtained reflection coefficient Γ (step S1010). Then, the result output display unit 5 displays / outputs the characteristic impedance for each frequency of the printed wiring board obtained by the frequency characteristic calculation unit 4 (step S1011).

Note that the reflection coefficient Γ obtained in step S1009 is originally a complex number, but when there is no influence of parasitic components on the waveform, only the real part is obtained, and in the impedance calculation in step S1010, _Γreal = Γ.

Here, the formula will be described for obtaining the characteristic impedance _{Z LOAD} for each frequency (f) in step S1010. When the measurement target is a printed wiring board, _assuming that the cable impedance Z _Cable is Z _I and the measurement target impedance Z _DUT is the characteristic impedance Z _{LOAD of the} wiring, the equation (5) shown above is expressed as the characteristic impedance Z _LOAD. Is obtained, the following equation (19) is obtained.

  Here, the reflection coefficient Γ is a complex number and can be represented by the following expression (20).

By substituting this equation (20) into equation (19), the characteristic impedance Z _LOAD becomes the following equation (21).

  Here, when Γ is small, the square term can be ignored, so the above equation (21) can be approximately expressed by the following equation (22).

Further, in the above equation (22), when there is no influence of the parasitic component on the waveform, only the real part becomes Γ _real = Γ, and finally the characteristic impedance Z _LOAD (f) for each frequency is expressed by the following equation (23 ).

  According to the fifth embodiment, by setting the incident staircase wave data and the reflected staircase wave data as the waveform data of the printed wiring board to be measured, and calculating the reflection coefficient based on these waveform data, Frequency vs. wiring impedance can be calculated.

Embodiment 6 FIG.
In the fifth embodiment, the case where the frequency-dependent characteristic impedance is obtained based on the input of the waveform data of the incident staircase wave and the reflected staircase wave has been described. In the sixth embodiment, a case will be described in which a frequency-dependent characteristic impedance is obtained based on a waveform measured by a TDR waveform measuring instrument. The configuration of the frequency characteristic evaluation apparatus in the sixth embodiment is the same as that in FIG. 9 which is the configuration of the fifth embodiment.

  FIG. 13 is a flowchart of processing for calculating frequency-dependent characteristic impedance according to the sixth embodiment of the present invention. First, the input unit 1 accepts selection of which of two types of data to be input is input (step S1001). In the example of FIG. 13, the user has a format to input the number i, and i = 1 and 2 are input to the TDR waveform data when not connected to the measurement target and connected to the measurement target, respectively. Corresponds to the input of TDR waveform data. The input unit 1 accepts waveform data input corresponding to each data type according to this number (steps S1002 and S1301), and stores the set waveform data in the storage unit 2.

  FIG. 14 is waveform data in Embodiment 6 of the present invention, and is an image diagram of a TDR waveform when the probe tip for performing TDR measurement is not connected to the measurement target and a TDR waveform when connected to the measurement target. FIG. 14A shows the voltage value when the probe tip for performing TDR measurement is not connected to the measurement target, and FIG. 14B shows the voltage value when the probe tip for performing TDR measurement is connected to the measurement target. Each is shown as a function in the time domain.

  When the input of the waveform data corresponding to the selected type is completed, the input unit 1 next checks whether or not all the two types of data have been input (step S1004). If there is data that has not been input, the input unit 1 returns to the process of step S1001 and repeats a series of data input processes for uninput waveform data. On the other hand, if all the waveform data has been input, the input means 1 confirms whether or not to change the already input waveform data (step S1005).

  When changing the waveform data, the input unit 1 returns to the process of step S1001 and repeats a series of waveform data input processes for the number desired to be changed, thereby accepting and correcting the waveform data that needs to be changed. The waveform data is stored in the storage unit 2. On the other hand, when all the waveform data are available and there is no need to change these waveform data, two types of input data are determined and the process proceeds to the next calculation phase.

  When the two types of data are determined, the impulse response extraction unit 6 then extracts the two types of waveform data from the storage unit 2 and calculates the impulse response by time-differentiating the two types of waveform data (step S1302). . FIG. 15 shows an impulse response according to the sixth embodiment of the present invention. The impulse response of the TDR waveform when the probe tip for performing TDR measurement is not connected to the measurement target and the impulse of the TDR waveform when connected to the measurement target. It is an image figure of a response. FIG. 15A shows the voltage change rate when the probe tip for performing TDR measurement is not connected to the measurement target, and FIG. 15B shows the voltage change when the probe tip for performing TDR measurement is connected to the measurement target. The rate is shown as a function in the time domain, and corresponds to a time derivative of each waveform in FIGS. 14 (a) and 14 (b).

  Further, the impulse response extraction means 6 performs gating on the time axis for these impulse responses, and extracts only data in a narrow time axis range including the impulse (step S1303). This extraction can be performed by extracting the vicinity of time = 0 in FIGS. 15 (a) and 15 (b). This eliminates the effects of multiple reflections. Next, the Fourier transform means 7 transforms the extracted impulse response on the time axis into a frequency distribution by Fourier transform (step S1304).

  Next, the reflection coefficient calculation unit 8 calculates the ratio of the two frequency distributions converted by the Fourier transform unit 7 (step S1305). This ratio is equal to the reflection coefficient Γ for each frequency. Next, the frequency characteristic calculation unit 4 calculates the impedance for each frequency using the obtained reflection coefficient Γ (step S1010). Then, the result output display unit 5 displays / outputs the characteristic impedance for each frequency of the printed wiring board obtained by the frequency characteristic calculation unit 4 (step S1011).

The reflection coefficient Γ obtained in step S1305 is originally a complex number, but when the parasitic component at the connection position with the measurement target is sufficiently small, the imaginary part is close to zero, and in the impedance calculation in step S1010, Γ _real ≈Γ, and the characteristic impedance for each frequency can be calculated by using the equation (23) shown above.

  According to the sixth embodiment, as the waveform data of the printed wiring board that is the measurement target, the data of the TDR waveform when the probe tip for performing the TDR measurement is not connected to the measurement target and the measurement target when connected to the measurement target By setting TDR waveform data and calculating the reflection coefficient based on these waveform data, the frequency versus wiring impedance can be calculated.

  In addition, although the frequency characteristic evaluation apparatus in above-mentioned Embodiment 1-4 demonstrated the case where the S parameter measured value of the printed wiring board which is a measuring object was set with an input means, embodiment of this invention is described to this It is not limited. The frequency characteristic of the effective relative dielectric constant can be obtained by providing the S parameter measuring instrument itself with the function of the frequency characteristic evaluation apparatus in Embodiments 1 to 4 and using the S parameter measurement result by the S parameter measuring instrument itself as input data. An S-parameter measuring device that can be calculated can be obtained.

  Moreover, although the frequency characteristic evaluation apparatus in the above-mentioned Embodiment 6 explained the case where the TDR waveform data of the printed wiring board to be measured is set by the input means, the embodiment of the present invention is limited to this. It is not a thing. The frequency characteristics of the characteristic impedance can be calculated by providing the TDR waveform measuring instrument itself with the function of the frequency characteristic evaluation apparatus in Embodiment 6 and using the measurement result of the waveform data by the TDR waveform measuring instrument itself as input data. A possible TDR waveform measuring instrument can be obtained.

  DESCRIPTION OF SYMBOLS 1 Input means, 2 Memory | storage part, 3 Passing phase difference calculation means, 4 Frequency characteristic calculation means, 5 Result output display means, 6 Impulse response extraction means, 7 Fourier-transform means, 8 Reflection coefficient calculation means.

Claims (4)

An apparatus for evaluating frequency characteristics of signal wiring,
Input means for setting time domain waveform data relating to an incident wave of a staircase waveform with respect to the signal wiring to be measured and a reflected wave with respect to the incident wave;
A storage unit for storing the waveform data set by the input means;
Based on the waveform data stored in the storage unit, impulse response extraction means for extracting an impulse response by time-differentiating the waveform data of the incident wave and the reflected wave;
Fourier transform means for Fourier transforming the impulse response to obtain an amplitude distribution for each frequency of the waveform of the incident wave and the reflected wave;
Reflection coefficient calculating means for calculating a reflection coefficient by calculating an amplitude ratio for each frequency from the amplitude distribution with respect to the waveform of the incident wave and the reflected wave;
A frequency characteristic evaluation device comprising: frequency characteristic calculation means for calculating a frequency characteristic of the characteristic impedance of the signal wiring based on the reflection coefficient. In the frequency characteristic evaluation apparatus according to claim 1,
The input means sets, as the incident wave, a TDR waveform measured without connecting a probe tip for performing TDR measurement to the signal wiring to be measured, and sets the probe tip to the signal wiring to be measured. A frequency characteristic evaluation apparatus, wherein a TDR waveform measured in a connected state is set as the reflected wave. The frequency characteristic evaluation apparatus according to claim 2,
Measuring a TDR waveform in a state in which a probe tip for performing TDR measurement is not connected to the signal wiring to be measured, and a TDR waveform in a state in which the probe tip is connected to the signal wiring to be measured; The measurement result of the TDR waveform in a disconnected state is set in the input means as the incident wave, the measurement result of the TDR waveform in the connected state is set in the input means as the reflected wave, and the frequency characteristic calculating means The TDR waveform measuring instrument characterized in that the frequency characteristic of the characteristic impedance of the signal wiring is calculated by A program for an apparatus for evaluating frequency characteristics of signal wiring,
Computer
Input means for setting time domain waveform data relating to an incident wave of a staircase waveform with respect to the signal wiring to be measured and a reflected wave with respect to the incident wave;
Impulse response extraction means for taking out the waveform data from the storage unit that stores the waveform data set by the input means, and extracting the impulse response by time-differentiating the waveform data of the incident wave and the reflected wave;
Fourier transform means for Fourier transforming the impulse response to obtain an amplitude distribution for each frequency of the waveform of the incident wave and the reflected wave;
Reflection coefficient calculating means for calculating a reflection coefficient by calculating an amplitude ratio for each frequency from the amplitude distribution with respect to the waveform of the incident wave and the reflected wave;
A program for a frequency characteristic evaluation apparatus for functioning as a frequency characteristic calculation means for calculating a frequency characteristic of a characteristic impedance of the signal wiring based on the reflection coefficient.

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