JP2531570Y2 - Error detector - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention takes the difference between the signal under test and the threshold value using a differential amplifier-type waveform shaping circuit, retiming the output with the input clock signal, The present invention relates to an error detector for comparing the retimed output with a reference pattern signal to detect an error in a signal under measurement.

[Prior Art] FIG. 2 shows a conventional error detector. Measured signal from the input terminal 11 is input to the non-inverting input terminal of a differential amplifier type of the waveform shaping circuit 12, is compared with a threshold value V _T which is applied to its inverting input, and the difference is amplified Waveform shaping circuit 12
Output from The output of the waveform shaping circuit 12 is supplied to the data terminal D of the D-type flip-flop 13, and the clock terminal
Retimed by the clock signal from 14. The retimed signal output from the D-type flip-flop 13 is compared with the reference pattern from the reference pattern generation circuit 15 by the exclusive OR circuit 16, and the output of the exclusive OR circuit 16 is retimed by the gate 17. The output of the gate 17 is counted by an error counter 18, for example.

Across the voltage -V and + V of the variable resistor 19 is provided respectively, a voltage obtained mover of the variable resistor 19 is supplied to the waveform shaping circuit 12 as a threshold V _T. This threshold
V _T is normally set to an intermediate value between the high level and the low level of the input signal under measurement. At this time, a correct waveform shaped output is obtained at the output terminal 21 of the waveform shaping circuit 12. In order to correctly retime this waveform shaping output, the clock signal at clock terminal 14 has the same frequency as the signal under test, but the phase is adjusted by variable delay unit 22 so that the midpoint between the rise and fall of the signal under test is obtained. The waveform shaping output is taken into the D-type flip-flop 13. The output clock signal of the variable delay unit 22 is also input to the reference pattern generation circuit 15, and the reference pattern generation circuit 15 generates the same reference pattern as the pattern when there is no error in the signal under measurement. The reference pattern is synchronized with the signal under measurement in the reference pattern generation circuit 15. Therefore, if there is no error in the signal under measurement,
The output of 17 remains at a low level. If there is an error in the signal under test, one pulse is output from the gate 17 for each error.

Amplitude of the measured signal which is input to the input terminal 11 'invention is to provide a "case where the offset level, the frequency (bit rate) is definite, the setting range of measurable threshold V _T, and variable Delay unit
The relationship with the set range of the delay amount τ of 22 is a hatched circular area in FIG.

Amplitude, offset level, if the frequency is input unknown signal to be measured, while changing both the the threshold V _T delay tau, it must Locate the proper hatched area of Figure 3. This is very time consuming and very inefficient. Thus the measured signal amplitude, measured in advance the offset level, first set the V _T, then looking for a range of τ to set the τ in the center, requires the oscilloscope for measurement Not economic.

According to the invention, the output of the reference pattern generation circuit is the first.
The output of the waveform shaping circuit is also averaged by being supplied to the average value circuit, and is also averaged by being supplied to the second average value circuit.
The difference between the output of the first average value circuit and the output of the second average value circuit is obtained by a feedback differential amplifier, and the output of the feedback differential amplifier is supplied to a waveform shaping circuit as a threshold value. Feedback control is performed so that the threshold value is always at an appropriate level.

"Embodiment" FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. In the present invention, the output reference pattern of the reference pattern generation circuit 15 is branched and supplied to the first average value circuit 24 to be averaged. Waveform shaping circuit
The twelve outputs are branched and supplied to a second average value circuit 25 for averaging. The time constants of the first and second average value circuits 24 and 25 are made longer than the period of the reference pattern of the reference pattern generation circuit 15. The output of the first average value circuit 24 is supplied to the inverting input side of the feedback differential amplifier 26, and the output of the second average value circuit 25 is supplied to the non-inverting input side of the feedback differential amplifier 26. the output of the dynamic amplifier 26 is supplied to the inverting input terminal of the waveform shaping circuit 12 as a threshold V _T.

Now, the output of the waveform shaping circuit 12 and the reference pattern generating circuit
Assuming that the high level of the 15 outputs is −0.8 V and the low level is −16 V, the output voltage of the first average circuit 24 is −1.6 V + 0.8 V ×
(The mark ratio of the reference pattern). That is, it becomes as follows.

If the error of the signal under test is slight, the mark rate of the reference pattern is substantially equal to the mark rate of the signal under test. First
Since the feedback differential amplifier 26 performs feedback control so that the difference between the output of the average value circuit 24 and the output of the second average value circuit 25 becomes zero, the output waveform of the waveform shaping circuit 12 is It works so as to approach the output waveform. To example reference pattern, or small amplitude of the output waveform of the waveform shaping circuit 12, the offset of negative large, the output waveform of the threshold V _T is the downlink waveform shaping circuit 12 the amplitude increases, the negative The offset becomes smaller, the amplitude becomes equal to the reference pattern, and the offset becomes equal. In this way, the measured signal Even if the amplitude and offset level are unknown, an appropriate threshold value _VT is always automatically set.

"Effects of the invention" As described above, according to the invention, the threshold value of the waveform shaping circuit is automatically set, so that the operator only needs to adjust the variable delay unit 22 and the measurement efficiency is remarkably large. It doesn't need another expensive measuring instrument such as an oscilloscope.

[Brief description of the drawings]

Figure 1 is a circuit diagram showing an embodiment of the invention, FIG. 2 is a block diagram showing a conventional error detector, Figure 3 shows the relationship between the measurable range of the delay amount τ threshold V _T FIG.

Claims (1)

(57) [Scope of request for utility model registration] 1. A signal to be measured is differentiated from a threshold value by a waveform shaping circuit of a differential amplifier type, and its output is retimed by an input clock signal. An error detector for detecting an error of the signal under measurement by comparing the output of the first average value circuit supplied with the output of the reference pattern generation circuit and the second average value circuit supplied with the output of the waveform shaping circuit. An error detector comprising: a two-average circuit; and a feedback differential amplifier that takes the difference between the outputs of the first and second average circuits and outputs the difference as the threshold value.