JPS63227122A - D/a converter evaluating device - Google Patents

Abstract

PURPOSE:To evaluate a dynamic characteristic with high accuracy by a D/A converter evaluating device of a simple constitution, by using a digital pattern by which a D/A converter executes a large amplitude variation, and also, a level of a fundamental wave component does not become high. CONSTITUTION:A digital pattern data DT applied to a D/A converter to be evaluated DUT 2 from a pattern generator 1 of a D/A converter evaluating device becomes a signal by which a composite waveform to which a fundamental waveform (sin waveform) and an inversion waveform (-sin waveform) of the fundamental waveform has been brought to a pulse amplitude modulation PAM. A level of this signal which has been brought to an analog conversion by the DUT 2 is brought to a frequency analysis by a vector analyzer 3, and a sine wave signal Fs is evaluated. Subsequently, by using a digital pattern by which the D/A converter executes a large amplitude variation, and also, a level of a fundamental wave component does not become high, a dynamic characteristic of the D/A converter for executing a high speed conversion is evaluated with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a D/A converter evaluation device,
Specifically, the present invention relates to a device suitable for evaluating the dynamic operation of a high-speed D/A converter.

(Prior Art) FIG. 5 is a block diagram showing an example of a device for evaluating the dynamic characteristics of a conventional high-speed D/A converter.
In the figure, 1 is a pattern generator that generates digital pattern data DT, and is a D/A converter to be evaluated (hereinafter referred to as D
tJT) 2 to generate digital pattern data DT as shown in FIG. 6, for example, which can be expected to convert and output a sine wave. 3 is a spectrum analyzer that measures the frequency components of the analog sine wave signal As converted and output from the DLJT 2.

With this configuration, dynamic characteristics of the DtJT2, such as glitch, jitter, and linearity, can be measured based on the frequency component measurement results (frequency spectrum) obtained from the spectrum analyzer.

(Problems to be Solved by the Invention) However, according to such a conventional configuration, the DUT 2 has only a small amplitude change in a stepwise manner, and it is difficult to find a defect even if the DLIT 2 with poor settling characteristics is measured.

Furthermore, measurement of harmonic components is difficult because the level of the fundamental wave component is high, which increases distortion in the measurement system.

The present invention has been made with attention to these points, and its purpose is to use digital pattern data in which the D/A converter makes large amplitude changes and the level of the fundamental wave component is thick. This allows D/A to perform high-speed conversion.
An object of the present invention is to provide a device that can accurately evaluate the dynamic characteristics of an m converter.

(Means for Solving the Problems) The present invention achieves the above object by applying pulse amplitude modulation to a D/A converter to be evaluated by using a composite waveform in which a fundamental waveform and an inverted waveform of the fundamental wave layer are superimposed. pattern generation means for outputting the digital pattern data added from the pattern generation means; and a selection level measurement for frequency-analyzing the level of the analog signal converted and output from the D/A converter to be evaluated according to the digital pattern data added from the pattern generation means. It is characterized by consisting of means and.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the pattern generator 1 to 0U in the present invention.
3 is a waveform diagram showing a specific example of digital pattern data DT added to T2. FIG. As shown in FIG. 1, the digital pattern data DT applied from the pattern generator 1 to the DU 2 is a composite waveform in which a fundamental waveform (sin waveform) and an inverted waveform (-sin waveform) of the fundamental waveform are superimposed. has been subjected to pulse amplitude variation DI (hereinafter referred to as RAM).

The operation of the present invention using such digital pattern data will be explained.

Note that in the following explanation, an ideal D/A with infinite bits is used.
It is assumed that digital pattern data is converted to an analog signal using a converter, and the level of the converted analog signal is subjected to frequency analysis.

Figure 2 shows the sine wave signal Fs to be reproduced, and the third
The figure shows a sampling pulse waveform Fc used for PAM.

Here, if we calculate the Fourier series expansion of the waveform in Figure 2, we get Fs (t)-...(+) So, when we find the Fourier series expansion of the waveform in Figure 3, we get Fc (j) - (no becomes.

Therefore, the sine wave signal Fs is converted into a sampling pulse waveform Fc
The Fourier series of the RAM waveform modulated by 11111G (
t) is as follows: G (t) = Fs - Fc (3).

FIG. 4(a) shows the waveform of G(t>), and FIG. 4(b) shows its spectrum.

As is clear from FIG. 4, when G(t) is used, the spectrum of Fs no longer exists, and the spectrum of n-FS can be measured with high accuracy.

Furthermore, by using a sine wave signal as in the embodiment as the basic waveform, the envelope of the digital pattern data can be
n x and −sin x, and it is also possible to evaluate the characteristics when the D/A converter makes the maximum amplitude change from zero to full scale and from full scale to zero.

According to such a configuration, D
Since tJT2 is driven, output nonlinearity due to amplitude clearly appears. Then, the characteristics of the output signal such as settling and glitches become clear from the occurrence of harmonic distortion, and the analogical analysis of the failure mode of DtJT2 becomes easy.

In the above embodiment, an example in which a sine wave is used as the basic waveform has been described, but a triangular wave, for example, may also be used.

Further, the offset, phase, amplitude, etc. of the digital pattern data may be changed as necessary.

(Effect of R-light) As explained above, according to the present invention, the D/A converter evaluation (IIIi device) is capable of accurately evaluating the dynamic characteristics of a high-speed D/A converter with a relatively simple configuration. This can be realized and has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a waveform example diagram of digital pattern data used in the present invention, FIGS. 2 to 4 are waveform example diagrams for explaining the present invention in detail, and FIG. 5 is a conventional high-speed D/A converter. FIG. 6 is a block diagram showing an example of a device for evaluating the dynamic characteristics of the D/A converter shown in FIG. 5. FIG. 1... Pattern generator, 2... D/A converter to be evaluated Fig. 1 Fig. 2 Fs(t)

Claims (1)

[Scope of Claims] Pattern generation means for outputting digital pattern data in which a composite waveform in which a fundamental waveform and an inverted waveform of the fundamental waveform are superimposed on a D/A converter to be evaluated is pulse-amplitude modulated; A D/A conversion characterized by comprising: selection level measuring means for frequency-analyzing the level of an analog signal converted and output from a D/A converter to be evaluated according to digital pattern data applied from the means; instrument evaluation device.