CIRCUIT CHARACTERISTICS MEASURING SYSTEM AND CIRCUIT CHARACTERISTICS MEASURING METHOD

Abstract

This circuit characteristic measurement system 1 is provided with: a signal voltage generation circuit 2 which sequentially applies, to a circuit to be measured 51 that is a measurement target, a plurality of periodic voltage signals which respectively have a prescribed reference frequency, and frequencies of integral multiples of the reference frequency; a measurement circuit 3 which sequentially measures pieces of the power of signals generated from the circuit to be measured 51 by sequentially applying the period voltage signals to the circuit to be measured 51; a transfer function calculation unit 42 which calculates transfer functions H, H2 of the circuit to be measured 51 on the basis of the plurality of pieces of power measured in the measurement circuit 3 by using an equation set in advance, wherein the periodic voltage signal includes a high-frequency component.

Description

[Technical field]

[0001] The present invention relates to a circuit characteristic measuring system for measuring the characteristics of a circuit, and a circuit characteristic measuring method. [Background technology]

[0002] Conventionally, a method for measuring the power supply impedance of an on-chip power supply node has been known (for example, see Non-Patent Document 1). According to Non-Patent Document 1, a current source is used, a square wave current is caused to flow from the current source to the power supply node by a sink, the effective power at the power supply node is measured, and the power supply impedance of the power supply node can be measured based on this effective power. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] A Technique for Analyzing On-chip Power Supply Impedance, 2015 IEEE 24th Asian Test Symposium, Masahiro Ishida, Toru Nakura, Akira Matsukawa, Rimon Ikeno, and Kunihiro Asada Summary of the Invention

[0004] Incidentally, in Non-Patent Document 1, a current source circuit capable of passing a square wave current is required. However, it is not easy to realize a current source circuit that performs current control to pass a square wave current, and even if it is realized, it is expensive.

[0005] An object of the present invention is to provide a circuit characteristics measuring system and a circuit characteristics measuring method capable of measuring the characteristics of a circuit under test without using a current source circuit that performs current control to pass a square wave current.

[0006] A circuit characteristic measurement system according to one embodiment of the present invention includes a signal voltage generating circuit that sequentially applies a plurality of periodic voltage signals, each having a predetermined reference frequency and a frequency that is an integer multiple of the reference frequency, to a circuit under test that is to be measured; a measurement circuit that sequentially measures the power of a signal generated in the circuit under test as the periodic voltage signals are sequentially applied to the circuit under test; and a transfer function calculation unit that uses a predetermined formula to calculate a transfer function of the circuit under test based on the power measured by the measurement circuit, wherein the periodic voltage signal includes high-order frequency components.

[0007] Moreover, a circuit characteristic measuring method according to one embodiment of the present invention includes a signal voltage applying step of sequentially applying a plurality of periodic voltage signals, each having a predetermined reference frequency and a frequency that is an integer multiple of the reference frequency, to a circuit under test to be measured, a measuring step of measuring the power of a signal generated in the circuit under test by applying the periodic voltage signals to the circuit under test, and a transfer function calculating step of calculating a transfer function of the circuit under test based on the plurality of powers measured by the measuring circuit using a predetermined mathematical formula, wherein the periodic voltage signals include high-order frequency components. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing an example of a configuration of a circuit characteristics measuring system that uses a circuit characteristics measuring method according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart showing an example of the operation of the circuit characteristics measuring system 1. [Diagram 3] FIG. 11 is an explanatory diagram for explaining a method for measuring the characteristics of a circuit portion related to the measurement of a transfer function. [Figure 4] 3 is a waveform diagram showing an example of a periodic voltage signal output from a signal voltage generating circuit 2a. FIG. [Diagram 5] 11 is a flowchart showing an example of a method for measuring the characteristics of a circuit portion involved in the measurement of a transfer function. [Figure 6] 10 is a flowchart showing an example of the operation of a circuit characteristics measuring system 1a that uses a periodic voltage signal other than a square wave. [Figure 7] FIG. 4 is a waveform diagram showing an example of a periodic voltage signal having a symmetric waveform. [Figure 8] 10 is a flowchart showing an example of the operation of a circuit characteristic measuring system 1b using a periodic voltage signal having a symmetric waveform. [Figure 9] FIG. 4 is a waveform diagram showing an example of an ideal trapezoidal waveform. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals are used to denote the same configuration, and the description thereof will be omitted. The circuit characteristic measuring system 1 shown in Fig. 1 includes a signal voltage generating circuit 2, a measuring circuit 3, a control unit 4, a plurality of probes Po for signal output, and a plurality of probes Pi for signal measurement.

[0010] A plurality of circuits under test 51 to be measured are formed on, for example, a single substrate 5. The circuits under test 51 may be, for example, a filter circuit, a circuit substrate, a transmission line, or any other circuit having electrical characteristics. Each circuit under test 51 has terminals T1 and T2.

[0011] The multiple circuits under test 51 may be multiple circuits of the same kind aggregated on one substrate 5 as an aggregate substrate, or different circuits under test 51 may be formed on one substrate 5. In addition, the multiple circuits under test 51 are not limited to being formed on one substrate 5, and may be independent of each other.

[0012] The signal voltage generating circuit 2 sequentially applies a plurality of periodic voltage signals, each having a predetermined reference frequency and a frequency that is m times (m is an integer) the reference frequency, to the circuit under test 51, which is the measurement target, in response to a control signal from the control unit 4. The signal voltage generating circuit 2 includes an oscillator circuit 21 and a clock buffer 22. Each periodic voltage signal is a signal that includes a frequency component of the respective fundamental wave and a higher-order frequency component that is a frequency component that is an integer multiple of two or more of the fundamental wave.

[0013] The oscillator circuit 21 outputs a periodic voltage signal having a frequency corresponding to a control signal from the control unit 4 to the clock buffer 22. For example, a VCO (Voltage Controlled Oscillator) can be used as the oscillator circuit 21. Note that the oscillator circuit 21 may be combined with a frequency divider circuit or the like to expand the frequency variation range.

[0014] The clock buffer 22 is a signal output circuit that shapes the periodic voltage signal output from the oscillation circuit 21 into a square wave and distributes and outputs the signal to the multiple probes Po. As a result, a periodic voltage signal of a square wave is output from the signal voltage generating circuit 2.

[0015] When making a measurement, each probe Po is brought into contact with a terminal T1 of each circuit under test 51, and each probe Pi is brought into contact with a terminal T2 of each circuit under test 51. As a result, the periodic voltage signal distributed and output from the clock buffer 22 is applied to the terminal T1 of each circuit under test 51 via each probe Po, and is output to the terminal T2 after passing through each circuit under test 51.

[0016] The measuring circuit 3 sequentially measures the power of signals generated in the measured circuit 51 as a result of periodic voltage signals being sequentially applied to the measured circuit 51 in response to a control signal from the control unit 4. As the measuring circuit 3, various general-purpose ICs (Integrated Circuits) capable of measuring RMS power, such as the RMS power detector LTC5596 manufactured by Analog Devices, Inc. and the ADL5904 manufactured by Analog Devices, Inc., can be used.

[0017] The number of measuring circuits 3 and probes Pi provided is the same as the number of periodic voltage signals distributed and output from the clock buffer 22, that is, the same as the number of probes Po.

[0018] Each measuring circuit 3 acquires a signal from terminal T2 of each circuit under test 51 via each probe Pi, and measures the effective power of the signal. Each measuring circuit 3 outputs a signal indicating the measured effective power to the control unit 4.

[0019] The circuit characteristics measuring system 1 includes a clock buffer 22 and a plurality of measuring circuits 3, and is thereby able to measure the characteristics of a plurality of circuits under test 51 in parallel. This makes it possible to reduce the measurement time. Note that the circuit characteristics measuring system 1 does not necessarily have to include the clock buffer 22 and the plurality of measuring circuits 3. Instead of the clock buffer 22, a buffer circuit that shapes the waveform into a rectangular wave may be included, and there may be only one measuring circuit 3, with the characteristics of the circuits under test 51 being measured one by one.

[0020] The control unit 4 is configured to include, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a RAM (Random Access Memory) that temporarily stores data, a non-volatile storage unit 43 such as a flash memory or HDD (Hard Disk Drive) that stores predetermined control programs, and peripheral circuits thereof.

[0021] The control unit 4 functions as a measurement control unit 41 and a transfer function calculation unit 42 by executing a control program stored in the storage unit 43, for example.

[0022] The measurement control section 41 outputs a control signal to the signal voltage generating circuit 2, causing the signal voltage generating circuit 2 to output a periodic voltage signal of a predetermined frequency. As a result, a periodic voltage signal of the predetermined frequency is applied to the terminal T1 of each measured circuit 51. In addition, the measurement control section 41 causes each measuring circuit 3 to measure the power of the signal output from the terminal T2 during the period in which the signal voltage generating circuit 2 is outputting the periodic voltage signal of the predetermined frequency.

[0023] The measurement control unit 41 stores the power measured by each measuring circuit 3, for example, in the memory unit 43, in association with the frequency output from the signal voltage generating circuit 2. Thereafter, the measurement control unit 41 repeats the output of a periodic voltage signal by the signal voltage generating circuit 2 and the power measurement by each measuring circuit 3 while changing the frequency, and stores the measured power in the memory unit 43 or the like in association with each frequency.

[0024] The transfer function calculation unit 42 uses a preset formula to calculate the transfer function of each measured circuit 51 based on the multiple powers measured by each measuring circuit 3. As the preset formula, for example, a formula obtained by expanding the periodic voltage signal into a Fourier series can be used. As the formula obtained by expanding the periodic voltage signal into a Fourier series, formula (1), formula (1)', formula (2), formula (2)', formula (3), or formula (3)', which will be described later, can be used.

[0025] Next, a description will be given of the operation of the circuit characteristics measuring system 1 configured as described above. In the following flowcharts, the same processes are given the same step numbers, and descriptions thereof may be omitted.

[0026] 2, the measurement control unit 41 initializes a variable m to 1 (step S1). Next, the measurement control unit 41 outputs a control signal to the signal voltage generating circuit 2, causing the signal voltage generating circuit 2 to output a periodic voltage signal of a reference frequency mf0 and apply it to each circuit under measurement 51 (step S2).

[0027] Then, the power of the signal transmitted through each circuit under test 51 is measured as P(mf0) by each measuring circuit 3, and a signal indicating the measured value is output to the control unit 4 (step S3). The measurement control unit 41 associates the signal power P(mf0) obtained from each circuit under test 51 with the frequency mf0 and stores it in the memory unit 43 or the like (step S4).

[0028] Next, the measurement control unit 41 compares the variable m with, for example, 7 (step S5). If the variable m is less than 7 (NO in step S5), the measurement control unit 41 adds 2 to the variable m to change the frequency of the periodic voltage signal and continue the measurement (step S6), and repeats steps S2 to S5 again.

[0029] Then, a periodic voltage signal of reference frequency 3f0 is applied to each measured circuit 51 (step S2), the signal power P(3f0) is measured in each measuring circuit 3 (step S3), and the signal power P(3f0) of each measured circuit 51 is stored in correspondence with the frequency 3f0 (step S4).

[0030] As described above, steps S2 to S6 are repeated until the variable m becomes, for example, 7 in step S5. As a result, the signal powers P(f0), P(3f0), P(5f0), and P(7f0) of the circuits under test 51 are stored in the storage unit 43 etc. in association with the reference frequencies f0, 3f0, 5f0, and 7f0.

[0031] When the variable m becomes 7 (YES in step S5), the transfer function calculation unit 42 substitutes P(f0), P(3f0), P(5f0), and P(7f0) into the following formula (1)′ for each circuit under test 51 to obtain the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 (7f0) is calculated (step S7).

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[0032] Here, B is the peak voltage of the periodic voltage signal (rectangular wave) output from the signal voltage generating circuit 2, and A is the effective power of the periodic voltage signal.

[0033] Transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 Since (7f0) represents the characteristics of the circuit under test 51, the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 By calculating (7f0), the characteristics of the circuit under test 51 can be measured. 2 (f0), H 2 (3f0), H 2 (5f0), H 2 By taking the square root of (7f0), the transfer functions H(f0), H(3f0), H(5f0), and H(7f0) may be calculated as circuit characteristics, where H is an amplitude transfer function and does not include phase information.

[0034] The signal voltage generating circuit 2 shown in Fig. 1 outputs a square wave voltage signal as a periodic voltage signal. To generate a square wave voltage, a DC voltage can be switched by a switching element, and a periodic voltage signal can be easily generated by using a commercially available semiconductor element such as a clock buffer 22 or a buffer. Therefore, according to the circuit characteristics measuring system 1, a square wave voltage signal can be output as a periodic voltage signal and the characteristics of the circuit under test 51 can be measured without using a current source circuit that performs current control to pass a square wave current.

[0035] In addition, since the periodic voltage signal can be distributed to multiple circuits under test 51 by the clock buffer 22 and the power of the signal transmitted through each circuit under test 51 can be measured simultaneously and in parallel by multiple measuring circuits 3, it is easy to shorten the measurement time compared to measuring the characteristics of the circuits under test 51 one by one in sequence.

[0036] In addition, periodic voltage signals with four different frequencies f0, 3f0, 5f0, and 7f0 were applied, and the signal powers P(f0), P(3f0), P(5f0), and P(7f0) were measured, and the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 The frequency of the applied periodic voltage signal may be set to 5 or more (f0, 3f0, 5f0, 7f0, 9f0, ...), the -1 power matrix in equation (1) may be set to 5 x 5 or more, and the number of parameters of the transfer function may be set to 5 or more (H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 (7f0), H 2 (9f0)···).

[0037] By increasing the number of parameters of the transfer function, it becomes possible to measure the circuit characteristics of the circuit under test 51 with higher accuracy. On the other hand, increasing the number of parameters of the transfer function increases the time required for measurement and the amount of calculation processing. Therefore, the number of parameters of the transfer function to be calculated can be appropriately determined based on the balance between the required measurement accuracy of the circuit characteristics and the measurement time or the amount of calculation processing.

[0038] In addition, the periodic voltage signal does not necessarily have to be a square wave, but may be a periodically changing periodic waveform that contains high-order frequency components. When using a periodic waveform other than a square wave as the periodic voltage signal, it is necessary to measure the characteristics of the circuit portion involved in the measurement of the transfer function in the circuit characteristics measurement system 1 in advance.

[0039] 3, when measuring the characteristics of the circuit portion related to the measurement of the transfer function, a spectrum analyzer 6 is used instead of the measurement circuit 3. The signal voltage generating circuit 2a differs from the signal voltage generating circuit 2 in that the periodic voltage signal output from the signal voltage generating circuit 2a does not necessarily have to be a square wave. The periodic voltage signal output from the signal voltage generating circuit 2a may be any periodic waveform that changes periodically, and the signal waveform is not limited.

[0040] As shown in FIG. 4, the periodic voltage signal output from the signal voltage generating circuit 2a may be, for example, a signal having an asymmetric waveform with different rising and falling slopes.

[0041] The measurement control unit 41a differs from the measurement control unit 41 in that it further executes a process of measuring the characteristics of the circuit portion related to the measurement of the transfer function. The transfer function calculation unit 42a differs from the transfer function calculation unit 42 in that it uses equations (2)' and (2) instead of equations (1)' and (1) to calculate the transfer function of the measurement circuit 3.

[0042] First, characteristics are measured for a pair of probes Po and Pi connected to a first circuit under test 51. Referring to Fig. 5, the probe Pi connected to the first circuit under test 51 is connected to the spectrum analyzer 6, and the probe Po paired with the probe Pi is brought into contact with the probe Pi (step S11).

[0043] Next, the measurement control unit 41a initializes a variable m to 1 (step S12), where m is a natural number (1, 2, 3, ...). Next, the measurement control unit 41a outputs a control signal to the signal voltage generating circuit 2a, causing the signal voltage generating circuit 2a to output a periodic voltage signal of a reference frequency mf0 to the probe Po (step S13). Then, the periodic voltage signal is input to the spectrum analyzer 6 via the probes Po and Pi.

[0044] Next, the power A of the fundamental wave and its harmonics contained in the signal input to the spectrum analyzer 6 via the probes Po and Pi is (mn)m is measured by the spectrum analyzer 6 and stored in the storage unit 43 (step S14). n is the order of the harmonic with respect to the fundamental wave, and when n=1, it indicates the fundamental wave itself. Power A when n=1 (m×1)m represents the effective power of the fundamental wave having a frequency m times the reference frequency f0, and the power A when n is 3 or more (mn)m represents the effective power of the nth harmonic for the fundamental wave having a frequency m times the reference frequency f0. Similarly, the peak value B (m×1)m represents the peak value voltage of the fundamental wave having a frequency m times the reference frequency f0, and the peak value B (mn)m represents the peak voltage of the nth harmonic with respect to the fundamental wave having a frequency m times the reference frequency f0.

[0045] Specifically, when m=1, the power A of the fundamental wave (n=1) (1×1)1 , the power of the second harmonic (n=2) A (1×2)1 , the power of the third harmonic (n=3) A (1×3)1 , the power of the fourth harmonic (n=4) A (1×4)1 , the power of the fifth harmonic (n=5) A (1×5)1, the power of the sixth harmonic (n=6) A (1×6)1 Measure the power A of the fundamental wave (n=1) when m=2. (2×1)2 , the power of the second harmonic (n=2) A (2×2)2 , the power of the third harmonic (n=3) A (2×3)2 Measure the power A of the fundamental wave (n=1) when m=3. (3×1)3 , the power of the second harmonic (n=2) A (3×2)3 The maximum m and the maximum harmonic (maximum n) for which power is measured may be determined appropriately according to the required measurement accuracy of the circuit characteristics.

[0046] The power A measured in this way (mn)m may be stored in the storage unit 43 by transmitting it from the spectrum analyzer 6 to the control unit 4, for example. For example, the power A (mn)m may be stored in a storage medium such as a memory card or USB memory from the spectrum analyzer 6, and then the storage medium may be read by the control unit 4 to store the data in the storage unit 43, or the storage medium may be used as a part of the storage unit 43 as it is.

[0047] Next, the measurement control unit 41 compares the variable m with 7 (step S15). If the variable m is less than 7 (NO in step S15), 1 is added to the variable m to change the frequency of the periodic voltage signal and continue the measurement (step S16), and steps S13 to S15 are repeated again.

[0048] Steps S13 to S16 are repeated until the variable m becomes 7 in step S15, whereby the power A corresponding to m=1 to 7 is obtained. (mn)m That is, data indicating the characteristics of the circuit parts related to the measurement of the transfer function is measured and stored in the memory unit 43 .

[0049] In steps S5, S15, and steps S23 and S33 described later, the upper limit of m may be appropriately determined according to the required measurement accuracy of the circuit characteristics. The upper limit of m, i.e., the number of types of reference frequencies of the periodic voltage signal, is set to be equal to the maximum order of the harmonics measured for the periodic voltage signal with m=1.

[0050] Thereafter, steps S11 to S16 are sequentially performed for the remaining pairs of probes Po and Pi.

[0051] Next, a method for measuring the characteristics of the measurement circuit 3 using a periodic voltage signal other than a square wave will be described. A circuit characteristics measurement system 1a capable of measuring the characteristics of the measurement circuit 3 using a periodic voltage signal other than a square wave is shown in FIG. 1 with reference characters in parentheses.

[0052] The circuit characteristic measuring system 1a differs from the circuit characteristic measuring system 1 in that it includes a signal voltage generating circuit 2a, a control unit 4a, a measurement control unit 41a, and a transfer function calculation unit 42a instead of the signal voltage generating circuit 2, the control unit 4, the measurement control unit 41, and the transfer function calculation unit 42. The memory unit 43 of the control unit 4a stores the above-mentioned power A (mn)m is measured and stored in advance.

[0053] 6, the measurement control unit 41a initializes a variable m to 1 (step S21). Next, the measurement control unit 41a outputs a control signal to the signal voltage generating circuit 2a to cause the signal voltage generating circuit 2a to output a periodic voltage signal having a reference frequency mf0 and apply it to each circuit under measurement 51 (step S22).

[0054] Then, the power of the signal transmitted through each circuit under test 51 is measured as P(mf0) by each measurement circuit 3, and a signal indicating the measured value is output to the control unit 4a (step S3). The measurement control unit 41a associates the signal power P(mf0) obtained from each circuit under test 51 with the frequency mf0 and stores it in the storage unit 43 or the like (step S4).

[0055] Next, the measurement control unit 41a compares the variable m with, for example, 6 (step S23). If the variable m is less than 6 (NO in step S23), 1 is added to the variable m to continue the measurement by changing the frequency of the periodic voltage signal (step S24), and steps S22 to S23 are repeated again. By repeating steps S22 to S24 until the variable m becomes 6 in step S23, the signal powers P(f0) to P(6f0) of the circuits under measurement 51 are stored in the storage unit 43 etc. in association with the reference frequencies f0 to 6f0, similar to steps S1 to S6.

[0056] When the variable m becomes 6 (YES in step S23), the transfer function calculation unit 42a substitutes P(f0) to P(6f0) into the following equation (2)′ for each circuit under test 51, and calculates the power A (mn)m Based on this, the transfer function H 2 (f0)~H 2 (6f0) is calculated (step S25).

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[0057] As described above, according to steps S21 to S25, even if a periodic voltage signal other than a square wave is used, the transfer function H 2 (f0)~H 2 (6f0) can be measured. Note that the transfer function H 2 (f0)~H 2 By finding the square root of (6f0), the transfer functions H(f0) to H(6f0) may be calculated as the circuit characteristics.

[0058] According to the circuit characteristics measuring system 1a and steps S21 to S25, even if it is difficult to apply a rectangular wave periodic voltage signal to the circuit under test 51 due to the performance of the clock buffer 22, the impedance of the probes Po and Pi, the stray capacitance of the circuit, etc., it is possible to measure the characteristics of the circuit under test 51.

[0059] Also, for example, as shown in Fig. 7, when a periodic voltage signal is used that can be made symmetrical with respect to the axis of symmetry C by placing an axis of symmetry C perpendicular to the time axis t at a point on the time axis t of a signal waveform for one period T (hereinafter referred to as a periodic voltage signal with a symmetrical waveform), it is possible to measure the circuit characteristics as follows. The periodic voltage signal shown in Fig. 7 is, for example, a trapezoidal wave with equal rising and falling slopes.

[0060] 1, the configurations of a signal voltage generating circuit 2b and a control unit 4b differ from those of the signal voltage generating circuit 2a and the control unit 4a. The signal voltage generating circuit 2b outputs a periodic voltage signal with a symmetric waveform.

[0061] The measurement control unit 41b differs from the measurement control unit 41a in the following respects. In step S14, the measurement control unit 41b calculates the power A (mn)m In step S16, the measurement control unit 41b adds 2 to m, so that the measurement of the power A (mn)m Furthermore, the measurement control unit 41b uses equation (3)', which will be described later, instead of equation (2)'.

[0062] 8, the measurement control unit 41b initializes a variable m to 1 (step S31). Next, the measurement control unit 41b outputs a control signal to the signal voltage generating circuit 2b, causing the signal voltage generating circuit 2b to output a periodic voltage signal having a reference frequency mf0 and apply it to each circuit under measurement 51 (step S32).

[0063] Then, the power of the signal transmitted through each circuit under test 51 is measured as P(mf0) by each measurement circuit 3, and a signal indicating the measured value is output to the control unit 4b (step S3). The measurement control unit 41b associates the signal power P(mf0) obtained from each circuit under test 51 with the frequency mf0 and stores it in the storage unit 43 or the like (step S4).

[0064] Next, the measurement control unit 41b compares the variable m with, for example, 7 (step S33). If the variable m is less than 7 (NO in step S33), the measurement control unit 41b adds 2 to the variable m to change the frequency of the periodic voltage signal and continue the measurement (step S34), and repeats steps S32 to S33 again.

[0065] According to step S34, the periodic voltage signal having the reference frequency mf0 with the variable m being an even number in step S32 is not output, and the signal power P(mf0) with the variable m being an even number in steps S3 and S4 is not measured or stored.

[0066] As described above, by repeating steps S31 to S34 until variable m becomes 7 in step S33, the signal powers P(f0), P(3f0), P(5f0), and P(7f0) of each measured circuit 51 are stored in memory unit 43, etc. in correspondence with reference frequencies f0, 3f0, 5f0, and 7f0, in the same manner as steps S1 to S6.

[0067] When the variable m becomes 7 (YES in step S33), the transfer function calculation unit 42b substitutes P(f0), P(3f0), P(5f0), and P(7f0) into the following equation (3)' for each circuit under test 51, and calculates the power A (mn)m Based on this, the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 (7f0) is calculated (step S35).

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[0068] In addition, the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 By taking the square root of (7f0), the transfer functions H(f0), H(3f0), H(5f0), and H(7f0) may be calculated as circuit characteristics.

[0069] As described above, according to steps S31 to S35, when a periodic voltage signal having a symmetric waveform is used, the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), H 2 (7f0) can be calculated. Furthermore, since there is no need to measure the signal power P(mf0) where m is an even number in step S3, and the number of even-order terms can be reduced in equation (3)' in step S35, the process can be simplified compared to steps S21 to S25.

[0070] 1, an example has been shown in which the probe Pi is brought into contact with the terminal T2, and the power of the transmitted wave of the periodic voltage signal transmitted through the circuit under test 51 is measured by the measurement circuit 3. However, the probe Pi may be brought into contact with the terminal T1, and the power of the reflected wave of the periodic voltage signal reflected by the circuit under test 51 may be measured by the measurement circuit 3. Even in the case of measuring the reflected wave, the reflection characteristic by the measurement circuit 3, i.e., the transfer function of the reflected wave, can be measured by the same processes as those in steps S1 to S7, S11 to S16, S21 to S25, and S31 to S35.

[0071] Moreover, the transfer function calculation units 42, 42a, 42b are not necessarily limited to the example of using the formulas (1)', (2)', and (3)' themselves in steps S7, S25, and S35. The transfer function calculation units 42, 42a, and 42b may execute the calculations expressed by the formulas (1)', (2)', and (3)' in steps S7, S25, and S35, and may calculate, for example, formulas obtained by expanding the formulas (1)', (2)', and (3)'.

[0072] Next, we will explain that equations (1), (1)', (2), (2)', (3), and (3)' are mathematical expressions obtained by expanding the periodic voltage signal into a Fourier series. Note that equations (1), (2), and (3) are simplified versions of equations (1)', (2)', and (3)'.

[0073] The following equation (A) is a mathematical expression obtained by expanding a periodic voltage signal having a reference frequency f0 into a Fourier series, equation (B) is a mathematical expression obtained by expanding a periodic voltage signal having a reference frequency 2f0 into a Fourier series, and equation (C) is a mathematical expression obtained by expanding a periodic voltage signal having a reference frequency 3f0 into a Fourier series.

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[0074] B (1n)1 indicates the peak value of the nth harmonic component at the reference frequency f0, and B (2n)2 indicates the peak value of the nth harmonic component at the reference frequency 2f0, and B (3n)3 indicates the peak value of the nth harmonic component when the reference frequency is 3f0, and ω=2πf.

[0075] e in formulas (A), (B), and (C) jθ The term has an absolute value of 1, and the periodic voltage signal V T1 (t), V T2 (t), V T3 (t) Power P T1 ,P T2 ,P T3 can be expressed by the following equations (D), (E), and (F).

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[0076] Here, P=VI, P=V 2 Therefore, the power P shown in equations (D), (E), and (F) is T1 ,P T2 ,P T3 is actually a value obtained by dividing by the characteristic impedance R (for example, 50Ω) of the circuit under test 51, but the characteristic impedance R is omitted in equations (D), (E), and (F).

[0077] Next, let the signal attenuation rates of frequencies 1f0, 2f0, 3f0, mf0 be H1, H2, H3, H m Then, the signal V after the periodic voltage signals of frequencies 1f0, 2f0, and 3f0 pass through the circuit under test 51 isF1 (t), V F2 (t), V F3 (t) is represented by the following formulas (G), (H), and (I).

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[0078] signal V F1 (t), V F2 (t), V F3 (t) Power P F1 (=P(f0)),P F2 (=P(2f0)),P F3 (=P(3f0)) is expressed by the following equations (J), (K), and (L).

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[0079] When equations (J), (K), and (L) are expressed using matrices, the following equation (M) is obtained.

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[0080] By transforming equation (M), equations (2) and (2)' are obtained. Therefore, equations (2) and (2)' are nothing but equations obtained by expanding the periodic voltage signal into a Fourier series.

[0081] Next, when a symmetric waveform is used as a periodic voltage signal, specifically, as shown in FIG. 9, the rise time τ r and the signal fall time τ f When a trapezoidal wave having equal amplitudes is used as the periodic voltage signal, the periodic voltage signal is expressed by the following equation (N) when expanded into a Fourier series.

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[0082] In equation (N), if f=1 / T and τ=T / 2, sin(nπf0τ)=0 when n is an even number. Therefore, when a symmetric waveform is used as a periodic voltage signal, the harmonic components of even multiples of the frequency f0 can be removed as shown in equation (O) below. Note that if the waveform is slightly deformed from the ideal trapezoidal waveform shown in FIG. 9, some harmonic components of even multiples of the frequency f0 will remain. However, if the signal waveform can be roughly approximated to an ideal trapezoidal waveform, the harmonic components of even multiples of the frequency f0 are small enough to be ignored.

[0083] Therefore, as shown in the following equation (O), the harmonic components that are even multiples of the frequency f0 can be deleted from equation (M).

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[0084] By transforming equation (O), equations (3) and (3)' are obtained. Therefore, equations (3) and (3)' are nothing but equations obtained by expanding the periodic voltage signal into a Fourier series.

[0085] Next, when a square wave is used as the periodic voltage signal, since the square wave is a symmetric waveform, equations (3) and (3)' can be applied.

[0086] Furthermore, for an ideal square wave, the peak value B of the nth harmonic n If the peak value of the square wave is B, then n =(4 / π)·(B / 2)·{1 / (2n-1)}. Therefore, the power A in equations (3) and (3)' (mn)m The term contains the peak value B of the nth harmonic (mn)m By substituting and transforming the formula, we obtain formula (1) and formula (1)'. Therefore, formula (1) and formula (1)' are nothing but formulas obtained by expanding the periodic voltage signal into a Fourier series.

[0087] That is, a circuit characteristic measuring system according to one embodiment of the present invention includes a signal voltage generating circuit that sequentially applies a plurality of periodic voltage signals, each having a predetermined reference frequency and a frequency that is an integer multiple of the reference frequency, to a circuit under test that is to be measured, a measuring circuit that sequentially measures the power of a signal generated in the circuit under test as the periodic voltage signals are sequentially applied to the circuit under test, and a transfer function calculating unit that calculates a transfer function of the circuit under test based on the power measured by the measuring circuit using a predetermined formula, and the periodic voltage signal includes high-order frequency components.

[0088] Moreover, a circuit characteristic measuring method according to one embodiment of the present invention includes a signal voltage applying step of sequentially applying a plurality of periodic voltage signals, each having a predetermined reference frequency and a frequency that is an integer multiple of the reference frequency, to a circuit under test to be measured, a measuring step of measuring the power of a signal generated in the circuit under test by applying the periodic voltage signals to the circuit under test, and a transfer function calculating step of calculating a transfer function of the circuit under test based on the plurality of powers measured by the measuring circuit using a predetermined mathematical formula, wherein the periodic voltage signals include high-order frequency components.

[0089] According to these configurations, a plurality of periodic voltage signals are sequentially applied to the circuit under test, the resulting powers are sequentially measured, and the transfer function of the circuit under test is calculated based on these powers using a preset formula. In this case, it is possible to calculate the transfer function of the circuit under test, that is, to measure the characteristics of the circuit under test, by generating a periodic voltage signal, which is an easy-to-generate voltage signal, without using a current source circuit that performs current control to pass a square wave current as in Non-Patent Document 1.

[0090] Furthermore, it is preferable that the periodic voltage signal is a square wave, and when the reference frequency is f0, the frequencies of the plurality of periodic voltage signals are odd multiples of the reference frequency f0.

[0091] According to this configuration, a periodic voltage signal of a rectangular wave that is easy to generate is used, and there is no need to generate a periodic voltage signal with a frequency that is multiple times the reference frequency f0, so that it is easy to measure the characteristics of the circuit under test.

[0092] In addition, when the frequency of the periodic voltage signal is f0, 3f0, 5f0, . . . and the power of the periodic voltage signal is A, the transfer function calculation unit calculates the transfer function H of the circuit under test by performing the calculation represented by the following formula (1), which is the mathematical formula: 2 (f0), H 2 (3f0), H 2 It is preferable to calculate (5f0), .

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[0093] According to this configuration, when a rectangular wave is used as the periodic voltage signal, the transfer function H 2 (f0), H 2 (3f0), H 2 (5f0), ...that is, it is easy to calculate the circuit characteristics.

[0094] In addition, the reference frequency is mf0 (m=1), the integral multiple frequency is mf0 (m is an integer of 2 or more), and the power A of the fundamental wave and its harmonic (mn)m (n is the order of the harmonic: n=1, 2, 3, . . . ) in advance, and the transfer function calculation unit calculates the power A (mn)m Based on this, the transfer function H of the circuit under test is calculated by the following formula (2). 2 (mf0) (m=1, 2, 3, . . . ) is calculated, and the power A (mn)m It is preferable that (n=1, 2, 3, ...) is the power contained in each of the periodic voltage signals that are measured by the measurement circuit when the periodic voltage signals of the frequency mf0 (m=1, 2, 3, ...) are applied from the signal voltage generating circuit to the measurement circuit without passing through the measured circuit.

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[0095] According to this configuration, regardless of the waveform of the periodic voltage signal, the transfer function H 2 (mf0) (m=1, 2, 3, . . .), i.e., it is easy to calculate the circuit characteristics.

[0096] In addition, the periodic voltage signal can be made symmetrical with respect to a symmetrical axis by arranging a symmetrical axis perpendicular to the time axis at a point on the time axis of a signal waveform for one period. The reference frequency is mf0 (m=1), the integral multiple frequency is mf0 (m is an odd number of 3 or more), and the power A of the fundamental wave and its harmonic is (mn)m (n is the order of the harmonic: n=1, 3, 5, . . . ) in advance, and the transfer function calculation unit calculates the power A (mn)m Based on this, the transfer function H of the circuit under test is calculated by the following formula (3). 2 (mf0) (m=1, 3, 5, . . . ) is calculated, and the power A (mn)m It is preferable that (n=1, 3, 5, ...) is the power contained in each of the periodic voltage signals that are measured by the measurement circuit when the periodic voltage signals of the frequencies mf0 (m=1, 3, 5, ...) are applied from the signal voltage generating circuit to the measurement circuit without passing through the measured circuit.

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[0097] According to this configuration, when a waveform that can be made symmetrical with respect to a symmetrical axis by arranging a symmetrical axis perpendicular to the time axis at a point on the time axis of a signal waveform for one period is used as the periodic voltage signal, the transfer function H 2(mf0) (m=1, 3, 5, . . .), i.e., it is easy to calculate the circuit characteristics.

[0098] It is also preferable that the measurement circuit measures the power of the reflected wave of the periodic voltage signal reflected by the circuit under test.

[0099] With this configuration, it is easy to calculate the transfer function of the circuit under test, i.e., the circuit characteristics, not only by measuring the power of the transmitted wave of the periodic voltage signal that has passed through the circuit under test, but also by measuring the power of the reflected wave of the periodic voltage signal that has been reflected by the circuit under test.

[0100] The circuit characteristics measuring system and the circuit characteristics measuring method configured as above can measure the characteristics of the circuit under test without using a current source circuit that performs current control to pass a square wave current.

[0101] This application is based on Japanese Patent Application No. 2019-176576 filed on September 27, 2019, the contents of which are incorporated herein by reference. Note that the specific embodiments or examples described in the section on the mode for carrying out the invention are merely intended to clarify the technical content of the present invention, and the present invention should not be interpreted in a narrow sense by being limited only to such specific examples. [Explanation of symbols]

[0102] 1,1a,1b Circuit characteristic measurement system 2, 2a, 2b Signal voltage generating circuit 3 Measurement circuit 4, 4a, 4b Control section 5 Substrate 6. Spectrum Analyzer 21 Oscillator Circuit 22 Clock Buffer 41, 41a, 41b Measurement control section 42, 42a, 42b Transfer function calculation unit 43 Storage section 51 Circuit under test A Power B Wave height value C Axis of symmetry H,H 2 Transfer Function P signal power Po,Pi probe T period T1, T2 terminals f0 reference frequency n degree

Claims

1. a signal voltage generating circuit for sequentially applying a plurality of periodic voltage signals having a predetermined reference frequency and a frequency that is an integer multiple of the reference frequency to a circuit under test; a measurement circuit that sequentially measures the power of a signal generated in the circuit under test as the periodic voltage signal is sequentially applied to the circuit under test; a transfer function calculation unit that calculates a transfer function of the circuit under test based on the power measured by the measurement circuit using a preset formula, the periodic voltage signal includes high-order frequency components and is a rectangular wave or a trapezoidal wave with equal rising and falling slopes; A circuit characteristic measuring system, wherein when the reference frequency is f 0 , the frequencies of the plurality of periodic voltage signals are odd multiples of the reference frequency f 0 .

2. The frequency of the periodic voltage signal is f ０ , 3f ０ , 5f ０ , ..., and the power of the periodic voltage signal is A, the transfer function calculation unit performs the calculation represented by the following formula (1), thereby obtaining the transfer function H ２ (f ０ ), H ２ (3f ０ ), H ２ (5f ０ 2. The circuit characteristics measuring system according to claim 1, wherein the circuit characteristics measuring system calculates: [0010]

3. The reference frequency is expressed as mf ０ (m=1), the integer multiple frequency is mf ０ (m is an integer of 2 or more), Power A of the fundamental wave and its harmonics （ｍｎ）ｍ (n is the order of the harmonic: n=1, 2, 3, ...), The transfer function calculation unit calculates the power A （ｍｎ）ｍ Based on this, the transfer function H of the circuit under test is calculated by the following formula (2): ２ (m.f. ０ ) (m=1, 2, 3, ...) The power A stored in the memory unit （ｍｎ）ｍ (n=1, 2, 3, ...) is the frequency mf ０ 2. The circuit characteristics measuring system according to claim 1, wherein m is the power contained in each of the periodic voltage signals (m=1, 2, 3, ...) that are measured by the measuring circuit when the periodic voltage signals are applied from the signal voltage generating circuit to the measuring circuit without passing through the circuit under test. [0025]

4. the periodic voltage signal can have a waveform symmetrical with respect to a symmetric axis by arranging a symmetric axis perpendicular to a time axis at a point on the time axis of a signal waveform for one period, The reference frequency is expressed as mf ０ (m=1), the integer multiple frequency is mf ０ (m is an odd number equal to or greater than 3) Power A of the fundamental wave and its harmonics （ｍｎ）ｍ (n is the order of the harmonic: n=1, 3, 5, ...) The transfer function calculation unit calculates the power A （ｍｎ）ｍ Based on this, the transfer function H of the circuit under test is calculated by the following formula (3): ２ (m.f. ０ ) (m=1, 3, 5, ...) The power A stored in the memory unit （ｍｎ）ｍ (n=1, 3, 5, ...) is the frequency mf ０ 2. The circuit characteristics measuring system according to claim 1, wherein m is the power contained in each of the periodic voltage signals (m=1, 3, 5, ...) that are measured by the measuring circuit when the periodic voltage signals are applied from the signal voltage generating circuit to the measuring circuit without passing through the circuit under test. [0030]

5. 5. The circuit characteristic measuring system according to claim 1, wherein the measuring circuit measures the power of a reflected wave of the periodic voltage signal reflected by the circuit under test.

6. a signal voltage application step of sequentially applying a plurality of periodic voltage signals having a predetermined reference frequency and a frequency that is an integer multiple of the reference frequency to a circuit under test; a measuring step of measuring the power of a signal generated in the circuit under test by applying the periodic voltage signal to the circuit under test; a transfer function calculation step of calculating a transfer function of the circuit under test based on the power measured in the measurement step by using a predetermined formula; the periodic voltage signal includes high-order frequency components and is a rectangular wave or a trapezoidal wave with equal rising and falling slopes; The circuit characteristic measuring method, wherein, when the reference frequency is f 0 , the frequencies of the plurality of periodic voltage signals are odd multiples of the reference frequency f 0 .

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