JPS63155737A - Signal processor - Google Patents

Abstract

PURPOSE:To efficiently reduce a white noise superposed on an input signal by calculating a correlation to a similar reference signal obtained in advance to an input signal synchronously with a trigger, and inputting the correlation output to an integrator. CONSTITUTION:A secondary electron signal of an input period signal 4 is input synchronously with a trigger 5, and a white noise is superposed. Reference signal generating means 2 generates simultaneously a reference signal 6 synchronously with the trigger 5 at this time. The signal 6 has a similar waveform to an input secondary electron signal 4, and a waveform obtained in advance by inputting a pulse to the same signal path. Then, the signals 4, 6 are calculated at the correlation between both by correlation means 1, and output correlation output signal 7 is a product of the signals 4 and 6, and input to integrating means 3. The means 3 externally receives a start signal 9, integrates the signal 7 for a predetermined time, and outputs the integrated output signal 8 as the signal amount of the input secondary electron signal 4. Accordingly, the white noise superposed on the input period signal can be effectively reduced.

Description

Detailed Description of the Invention [Summary] The present invention provides a signal processing device for detecting the amount of a signal such as a secondary electron signal in a strobe electron beam device, in which a correlation between an input signal and a reference signal similar to the signal is determined. By detecting the signal amount of the input signal using the integrated output signal obtained by calculating and integrating the correlation output signal, shot noise and circuit noise superimposed on the input signal can be effectively reduced. It is a signal processing device.

[Industrial application field]

The present invention relates to a technique for detecting the signal amount for each period of an input periodic signal, and particularly to a signal processing device that can reduce the influence of noise during detection.

[Conventional technology]

A strobe electron beam device emits electron beam pulses in synchronization with the trigger of the IC under test, and detects the amount of secondary electron signals detected for each trigger.
Measurements of the voltage waveform on C can be made.

The secondary electron signal is detected as a pulse synchronized with the trigger, but its pulse width is very short compared to the trigger period, and the frequency response bandwidth of the detection circuit is greater than the pulse band. Because it is narrow compared to the width, the secondary electron signal detected via the detection circuit has a waveform close to a triangular wave as shown in Figure 4(a) in synchronization with the trigger signal as shown in Figure 4(a). Then, the pulse for each period is affected by the shot noise of the electron beam and becomes fb in the same figure.
), the shape is not the same and fluctuations occur.

In order to detect the amount of secondary electron signal from such a waveform, conventionally, the secondary electron signal is integrated between each trigger (t, , ~1, .1) in Fig. 4, and the integrated output is It is detected as a signal amount in a period, thereby eliminating the influence of fluctuations and making it possible to detect a stable secondary electron signal amount.

In this case, a boxcar integrator, a digital signal integrator, or the like is used as the integrating means.

[Problem that the invention seeks to solve]

However, in addition to the above-mentioned effects, there is also white noise, which is the circuit noise of the secondary electron detection system as shown in Figure 5 (al), as noise superimposed on the secondary electron signal. The problem is that the noise is superimposed as shown in Figure 5, and this noise cannot be completely removed by the integrator.

In order to solve the above-mentioned problems, the present invention calculates the correlation between an input signal and a reference signal similar to the input signal obtained in advance, in synchronization with a trigger, and inputs the correlation output to an integrator. It is an object of the present invention to provide a signal processing device that can efficiently reduce white noise superimposed on an input signal such as an electronic signal.

[Failure to solve the problem]

The present invention has the configuration shown in FIG. 1 in order to solve the above problems. That is, a correlation means 1 calculates the correlation between an input periodic signal 4 inputted in synchronization with the trigger signal 5 and a reference signal 6, and generates an input periodic signal waveform obtained in advance as the reference signal 6 in synchronization with the trigger signal 5. Reference signal generation means 2
, and an integrating means 3 which integrates the correlation output signal 7 from the correlation means 1 in synchronization with a start signal 9 from the outside and outputs an integral output signal 8 as the signal amount of the input periodic signal 4.

[For production]

In each of the above means, first, the input periodic signal 4 is correlated with a reference signal 6 similar to it in the correlation means 1, so that the white noise superimposed on the input periodic signal 4 is reduced. Next, by integrating the correlation output signal 7 from the correlation means 1 in the integration means 3, the influence of fluctuations in the input periodic signal 4 is removed, and the integrated output signal 8 becomes stable as the signal amount of the input periodic signal 4. Detected.

〔Example〕

Embodiments of the present invention will be described in detail below. First, the configuration of the embodiment of the signal processing device is the same as the basic configuration shown in FIG. 1, and at this time, the correlation means 1 can be realized by a SAW compolver using a surface acoustic wave element or the like.

In Fig. 1, first, the secondary electronic signal which is the input periodic signal 4 is input in synchronization with the trigger 5 (see Fig. 4 (see 81)), and white noise is superimposed as shown in Fig. 5 (bl). At this time, the reference signal generating means 2 simultaneously generates a reference signal 6 in synchronization with the trigger 5.The reference signal 6 is
It is a waveform similar to the input secondary electronic signal 4, and is a waveform obtained by previously inputting a pulse to the same signal path by means not particularly shown.

Subsequently, the correlation between the secondary electron signal 4 and the reference signal 6 is calculated in the correlation means 1. The correlation output signal 7 output from the correlation means 1 is the product of the secondary electron signal 4 and the reference signal 6, and this signal is input to the integration means 3.

The integrating means 3 receives a start signal 9 from the outside, integrates the correlation output signal 7 for a predetermined period of time, and outputs the integrated output signal 8 as the signal amount of the inputted secondary electron signal 4.

Now, one period of the secondary electron signal which is the input periodic signal 4 in Fig. 1 is approximated by a sawtooth wave as shown in Fig. 2 (the time on the horizontal axis is a normalized value), and the reference signal 6 S/ Let's find N (signal-to-noise ratio).Here, if the same figure (C) is used as a reference signal, it is equivalent to using a conventional boxcar integrator.Figure 3 shows the boxcar integral Relative S/N for the case of window vergence x=1 of the method using a device
The results are shown below. The plot indicated by A in the figure is obtained when the reference signal 6 is made the same as the input signal in FIG. 2(a) as shown in FIG. According to this method, it is possible to maintain a higher S/N than in the method using a boxcar integrator shown in No. 34B, and the input periodic signal 4
It can be seen that the white noise inside is effectively reduced.

〔Effect of the invention〕

According to the present invention, when detecting the signal amount for each period of an input periodic signal such as a secondary electron signal in a strobe electron beam device, the correlation with a reference signal determined in advance is calculated, and the By integrating the correlation output and detecting the signal amount, it is possible to effectively reduce the white noise superimposed on the input periodic signal, remove the influence of fluctuation, and perform stable signal amount measurements.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a signal processing device according to the present invention, FIGS. 2(a), (bl, and c) are explanatory diagrams of a secondary electronic signal and a reference signal, and FIG. Figure 4 (al, (b) is an explanatory diagram of the effect of fluctuation in the secondary electron signal. Figure 5 (al, (b) is an illustration of the effect of white noise on the secondary electron signal. It is an explanatory diagram of influences. 1... Correlation means, 2... Reference signal generation means, 3... Integrating means, 4... Input periodic signal (secondary electronic signal), 5... External trigger , 6... Reference signal, 7... Correlation output signal, 8... Integral output signal.

Claims (1)

[Claims] 1) In a signal processing device that detects the signal amount for each cycle of an input periodic signal (4) input in synchronization with an external trigger signal (5), the trigger signal (5) The input periodic signal (4
) and a predetermined reference signal (6); and an integrating means (3) for integrating a correlation output signal (7) from the correlation means (1). A signal processing device characterized in that a signal amount of the input periodic signal (4) is detected using an integral output signal (8) from an integrating means (3). 2) A reference signal generating means (2) that generates the input periodic signal (4) obtained in advance as the reference signal (6) in synchronization with the trigger signal (5). The signal processing device according to item 1. 3) The signal processing device according to claim 1, wherein the input periodic signal (4) is a secondary electron detection signal in a strobe electron beam device.