JPH08327709A - Arbitrary waveform generator for dut test - Google Patents

Abstract

PURPOSE: To obtain the phase characteristics of a filter by using an arbitrary waveform generator as a signal source, and computing the phase characteristics by FFT processing from the measured data, which have passed a filter part and bypassed the filter part. CONSTITUTION: A sweeping sine wave 71sin is generated in synchronization with the start of sampling in an AD converter 14. An arbitrary waveform generator 70, which supplies the signal to a filter part 80 as the signal source for measuring phase characteristics, is provided. The passing characteristic of each filter of the filter part 80 is sampled and quantized into the digital signal in synchronization with the passing sweeping sine wave 71sin. An AD converter 14, which stores the signal into a buffer memory 16, is provided. An FFT processing part 18, which receives the obtained data in the buffer memory 16 and converts the data of the function of a time (t) into complex-function-data lines R(f) and I(f) of a frequency (f), is provided. A phase operating part 20, which receives the complexfunction-data lines R(f) and I(f) from the FFT processing part 18 and computes a phase ϕ(f) at each frequency (f), is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for testing an output signal from an arbitrary waveform generator of a device testing apparatus by filtering it with any one of a plurality of filter groups and then supplying it to a DUT (device under test) for testing. It relates to the measurement of the phase characteristic of this filter group.

[0002]

2. Description of the Related Art A mixed signal IC tester is known as a test device for measuring a DUT in which analog and digital are mixed. It has an arbitrary waveform generator 70 for supplying an arbitrary test waveform to the DUT, and there is a circuit for smoothing the stepped output waveform with a filter (low-pass filter) therein. There are multiple filters (low-pass filters),
It is used by switching according to various test conditions.

The filter group is made up of analog circuits, has various filter characteristics in order to correspond to various DUTs, and has different filter characteristics. Further, these filter circuits are likely to change depending on the ambient temperature.
In the test equipment, when performing various electrical tests of DUT,
The phase and amplitude of the waveform applied to the UT must be known values, and for this reason, calibration is performed to
Obtaining the phase characteristics of the filter circuit.

FIG. 3 shows a waveform signal 94 after the output waveform of the arbitrary waveform generator 70 is filtered under a desired filter condition.
2 is a configuration example of device measurement in the case of applying various values to the DUT 100 to measure various electrical characteristics.
0, the spectrum analyzer 150, and the controller 72. The arbitrary waveform generator 70 includes a pattern memory 74, a DA converter 76, and a filter unit 80.

The DUT 100 is, for example, a communication device that receives a signal that has been Nyquist filtered by the filter section 80, demodulates it, and outputs it.
The arbitrary waveform generator 70 is capable of digitally generating an arbitrary waveform, reads continuous data from the pattern memory 74, converts it into an analog signal by the DA converter 76, and then supplies it to the filter unit 80. To do.

In the filter section 80, the waveform signal 94 obtained by filtering the signal by switching it to a predetermined filter characteristic is D
Supply to UT. There are various filter groups used here, and the filter group includes the first filter 821 to the nth filter 82n.
Is available. Since these filters are composed of analog circuits, the phase identification changes with the passage of time and temperature. Since this apparatus is a device testing apparatus, the output phase of the waveform signal 94 applied to the DUT is tested with a known output phase in order to improve the test accuracy. Therefore,
The phase characteristics at the input and output ends of the filter section 80 must be obtained by performing calibration measurement in advance.

For this calibration measurement, the selector switches 78 and 92 and the spectrum analyzer 1
50 is provided to supply a signal from the TG terminal of the spectrum analyzer 150 to the first to nth filters via the switch 78, and one of the filter output terminals is connected to the measurement input terminal of the spectrum analyzer 150 via the switch 92. Then, the phase characteristic data is measured by sweeping a desired frequency range in the phase mode. The control unit 72 receives this measurement data via GPIB and saves and updates it in the internal phase correction parameter memory 73. From this phase characteristic, by adjusting and controlling the phase timing that the arbitrary waveform generator 70 should output, the phase relationship with other signals can be made into a desired phase relationship, and the DUT can be electrically tested at a predetermined timing.

[0008]

As described above, the spectrum analyzer 150 is provided outside to perform calibration, and the pass characteristics of each filter are measured to obtain phase data. For this purpose, it is necessary to provide the spectrum analyzer 150, and there is a drawback that it becomes expensive. Therefore, the problem to be solved by the present invention is to utilize the arbitrary waveform generator 70 as a signal source for calibration, measure sampling data when passing through the filter section 80 and when bypassing, and perform FFT processing. The purpose is to realize the phase characteristic measuring function of a relatively inexpensive filter by calculating the phase.

[0009]

In order to solve the above problems, in the configuration of the present invention, the pattern generation memory 74 and the DA converter for generating the swept sine wave 71sin in synchronization with the sampling start in the AD converter 14 are provided. An AD converter 14 for sampling the pass characteristic of each filter of the filter section 80, quantizing it into a digital signal, and storing it in the buffer memory 16 in synchronization with the sweep sine wave 71sin.
Is provided and receives the data of the buffer memory 16 obtained above, and converts the data of the function of time (t) into the complex number function data sequence R (f) and I (f) of the frequency (f). 1
8 is provided, and a phase difference calculation unit 20 that receives the complex number function data sequence R (f) and I (f) from the FFT processing unit 18 and calculates the phase φ (f) at each frequency (f) is provided. Make it a constituent means. As a result, the phase characteristic measuring function of the filter unit 80 that filters the stepped waveform output from the DA converter 76 in the arbitrary waveform generator 70 is realized.

[0010]

The measurement data without a filter and with a filter are measured in synchronization by making the sampling start of the AD converter 14, the generation timing of the sweep sine wave 71sin, and the sweep speed of the sweep sine wave 71sin the same. Data is obtained. That is, there is an effect that the correlation with the measurement data of another filter measured at another time is obtained. The arbitrary waveform generator 70 has an effect that it can be used also as a signal source for phase characteristic measurement by generating the swept sine wave 71sin in synchronization with the start of sampling.

The FFT processing unit 18 reads the data of the buffer memory 16 obtained synchronously, and from the data of the function of time (t), the complex function data string R of frequency (f).
The effect of converting into (f) and I (f) is obtained. Phase difference calculation unit 2
0 is the complex number function data string R from the FFT processing unit 18.
By receiving (f) and I (f), the phase φ (f) at each frequency (f) can be calculated, and the phase φ (f) characteristic of the sweep frequency section farea of each filter can be obtained. As a result, the phase characteristic measuring function of each filter can be realized at a relatively low cost. With these, the phase characteristic measuring function of each filter can be realized at a relatively low cost, and the waveform signal 94 applied to the DUT can be obtained.
The output phase of can be tested with a known output phase.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of phase characteristic acquisition of a filter according to the present invention. The configuration is such that an arbitrary waveform generator 70 and A
It includes a D converter 14, a buffer memory 16, an FFT processing unit 18, and a phase difference calculation unit 20. Arbitrary waveform generator 7
0 is the pattern memory 74 and the DA converter 7 as in the conventional case.
6 and a filter section 80.

In the present invention, a sweep sine waveform is generated as an output pattern of the arbitrary waveform generator 70 when the phase characteristic is acquired. As shown in FIG. 2, the swept sine wave (swept sine wave or multi-sine wave) 71sin means that in the case of a swept sine wave, the frequency from the lower limit to the upper limit of the desired frequency section farea is continuously generated. It is a sine waveform whose amplitude is constant with respect to the time axis. In the case of a multi-sine wave, the amplitude is constant and the phase is linear with respect to the frequency axis.

The measuring principle is that the phase characteristic φB data when the filter section 80 is bypassed is measured in synchronization with the generation of the swept sine wave 71sin, and the phase characteristic φA data when passing through the individual filters is also synchronized. And perform FFT processing on both, and phase difference at each frequency point φdif = φ
It is calculated as A-φB.

By the way, the measurement of both cannot be performed at the same time, and the measurement is performed at different times.
It is necessary to start sampling in perfect synchronization with 1sin. Therefore, synchronization is performed by the start signal 74stt for starting the generation of the arbitrary waveform generator 70. In addition, the sampling clock 77clk is applied to the DA converter 76 and the AD converter 14 for accurate synchronization. Of course, swept sine wave 71sin
The same sweep speed conditions are used.

The frequency of the sampling clock 77clk is set to a frequency sufficiently higher than the sweep sine wave 71sin in order to obtain a resolution that does not deteriorate the calculation accuracy during the FFT processing later. If the upper limit of wave 71sin is 200 KHz, 8 MHz
A sine clock is used so that tens of points can be sampled in one sine waveform section.

The measurement procedure is as follows. First, the pass characteristic is measured under the measurement condition when the filter section 80 is bypassed by the switch 12. Sweep sine wave 71s with start signal 74stt
The generation of in is started, and in synchronization with this, the AD converter 14 quantizes into a digital signal every sampling clock 77clk, and the frequency from the lower limit to the upper limit of the sweep frequency section farea is continuously measured and stored in the buffer memory 16. Store.

Secondly, the measurement is performed under the measurement conditions when switching to each filter in the filter section 80. Similarly to the above, the pass characteristics of each filter are sequentially measured in synchronization with the start signal 74stt and stored in the buffer memory 16.

The FFT processing unit 18 reads out the data of the buffer memory 16 acquired in synchronization with the above, and outputs the measurement data without filter and with filter with time (t).
Is a complex number function data string R (f), I (f) of frequency (f)
And is supplied to the phase difference calculator 20. Where R
(f) is a real number component, and I (f) is an imaginary number component.

The phase difference calculating section 20 obtains the phase at each frequency for each filter. Each frequency
The phase at (f) is calculated as φ (f) = tan ⁻¹ (I (f) / R (f)). Considering the phase characteristic value without a filter as the reference phase angle at each frequency = 0 degree, and subtracting this reference phase angle from the phase value of each filter, the phase φ (f ) The characteristics will be obtained. As a result, the phase characteristics of each filter can be obtained relatively inexpensively without preparing an expensive spectrum analyzer outside.

In the above description of the embodiment, the case where the phase characteristic φB when the filter section 80 is bypassed is also measured, but since the phase characteristic φB hardly changes with time, the value initially obtained is It may be stored in the memory and used. As a result, the phase characteristic φB when bypassed need not be measured each time.

[0022]

Since the present invention is configured as described above, it has the following effects. Each measurement data without filter and with filter is AD
Sampling start of converter 14 and sweep sine wave 71sin
The same measurement data can be obtained by setting the same generation timing and the sweep speed condition of the sweep sine wave 71sin. That is, there is an effect that the correlation with the measurement data of another filter measured at another time is obtained. Arbitrary waveform generator 70
Has an effect that it can be used as a signal source for phase characteristic measurement by generating the swept sine wave 71sin in synchronization with the start of sampling. The FFT processing unit 18 reads out the data of the buffer memory 16 acquired synchronously and
The effect of converting the data of the function of (t) into the complex number function data sequence R (f) and I (f) of the frequency (f) can be obtained. The phase difference calculation unit 20 receives the complex number function data sequence R (f) and I (f) from the FFT processing unit 18, and receives the phase φ (f) at each frequency (f).
Can be calculated, and the phase φ (f) characteristic of the sweep frequency section farea of each filter can be obtained. As a result, the phase characteristic measuring function of each filter can be realized at a relatively low cost.

[Brief description of drawings]

FIG. 1 shows a configuration diagram of phase characteristic acquisition of a filter according to the present invention.

FIG. 2 is a spectrum diagram for explaining a swept sine waveform output by an arbitrary waveform generator 70 of the present invention.

FIG. 3 shows a conventional configuration diagram for acquiring a phase characteristic of a filter using a spectrum analyzer 150.

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Claims (2)

[Claims] 1. Sampling by an AD converter (14) in obtaining a phase characteristic of a filter section (80) for filtering a stepwise waveform output from a DA converter (76) in an arbitrary waveform generator (70). A pattern generation memory (74) for generating a swept sine wave (71sin) in synchronization with the start and a DA converter (76) are provided, and each filter of the filter section (80) is synchronized with the swept sine wave (71sin). Is provided with an AD converter (14) for sampling the pass characteristic of quantized into a digital signal and storing it in a buffer memory (16), and receiving the data of the buffer memory (16) acquired above, the time (t) An FFT processing unit (1) that converts function data into complex number function data strings R (f) and I (f) of frequency (f)
8) is provided, receives the complex number function data sequence R (f), I (f) from the FFT processing unit (18), and receives the phase φ (f) at each frequency (f).
An arbitrary waveform generator for a DUT test, which is provided with a phase difference calculator (20) for calculating 2. The arbitrary waveform generator for DUT test according to claim 1, wherein the swept sine wave (71sin) is a swept sine wave or swept sine wave.