JPH0682574U - Waveform observation device - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a waveform observing device with improved input signal measurement efficiency by switching input signals at the input section. [Structure] A buffer that attenuates the input analog signal,
A first comparator that compares the output from the buffer with a set voltage value, and outputs a detection signal based on the magnitude relationship between the set voltage value and the voltage value of the input signal; and the output from the buffer Compare with the set voltage value,
A second comparator that outputs a detection signal based on the magnitude relationship between the set voltage value and the voltage value of the input signal, and has a frequency characteristic different from that of the first comparator;
Setting means for selecting and outputting the outputs of the comparator and the second comparator, and the voltage value to be compared between the first comparator and the second comparator, and setting the selection of the signal by the selecting means. A control circuit and a waveform observing device.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a waveform observing device, and more particularly to improvement of a circuit of a signal input portion of the waveform observing device.

[0002]

[Prior art]

 Conventionally, when an input signal to be measured has a high speed in a device for observing an electric signal, it is necessary to take the problem of input impedance or reflection into consideration when inputting the signal. Under such circumstances, it is necessary to limit the amplitude of the input signal, or to input a signal from the outside as a trigger signal as a component of the trigger input. Also, the trigger signal uses a circuit designed with a material that operates uniformly at high speed regardless of the frequency, but a high-speed operation is generally affected by thermal noise and the like. .

[0003]

[Problems to be solved by the device]

 Therefore, there is a problem that jitter is likely to occur when measuring a high frequency. An object of the present invention is to solve this problem and to realize a waveform observing device capable of accurately capturing a signal input and improving operability in observing the waveform of an electric signal.

[0004]

[Means for Solving the Problems]

 The present invention provides an input terminal for inputting an analog signal as a target of waveform observation from the outside, a buffer connected to the input terminal for attenuating the input analog signal, and an output from the buffer and a set voltage value. The first comparator that outputs a detection signal based on the magnitude relation between the set voltage value and the input signal voltage value is compared with the set voltage value by comparing the output from the buffer with the set voltage value. A second comparator that outputs a detection signal based on the magnitude relationship between the voltage value and the voltage value of the input signal and has a frequency characteristic different from that of the first comparator, and outputs of the first comparator and the second comparator And a voltage value to be compared by the first comparator and the second comparator are set, and a signal is selected by the selection means. A control circuit for a waveform observing apparatus, characterized in that a.

[0005]

[Action]

 The quality of the observed waveform can be improved by switching the input characteristics according to the characteristics of the signal.

[0006]

【Example】

 FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, 11 and 12 are comparators having different frequency characteristics, which compare an input signal with a set voltage value and output a detection signal based on the magnitude relationship between the set voltage value and the voltage value of the input signal. Suru At this time, in the comparator 11 and the comparator 12. Reference numerals 13 and 14 denote D flip-flops, the output of the comparator 11 is input to the clock terminal CK of the D flip-flop 13, and the output of the comparator 12 is input to the clock terminal CK of the D flip-flop 14. The outputs of the Q output terminals of the D flip-flops 13 and 14 are output by the selector 15. Further, the control means 6 outputs a signal for controlling the operation of the selector 15. Therefore, the operation of the D flip-flop 13 and the D flip-flop 14 is controlled by inputting a signal to the data terminal D of the D flip-flop 13 and the D flip-flop 14, and the select signal is output to the selector 15. As a result, the signal output in the selector 15 is selected.

The operation in such a configuration will be described. The input signals include those input to the comparator 11 and those input to the comparator 12. At this time, the comparator 11 has a lower frequency band than the comparator 12. At this time, the thermal noise in the comparator is represented by √ (4kTfR). Therefore, the wider the frequency band, the larger the thermal noise. For example, if f has a band twice that of the comparator 11 in the comparator 12, the thermal noise of the comparator 12 is 1.41 times that of the comparator 11.

Therefore, by providing a comparator having two types of frequency characteristics, it is possible to prevent the occurrence of jitter by using the trigger signal from the comparator suitable for the frequency of the input signal and its sampling method. If the frequency of the input signal is unknown, a method may be considered in which the comparator 11 and the comparator 12 are switched to input the input signal, and which of the observation results is used to determine which to use.

FIG. 2 is a block diagram of another embodiment of the present invention. In the figure, reference numeral 21 denotes a divider which is connected to the input terminal 1 and divides the input analog signal. This divider is composed of transmission lines R1 to R3. At this time, the transmission line R1 is connected to the input terminal 1, and the transmission lines R2 and R3 are connected to the comparator 22 and the comparator 23, respectively. Ground resistances R4 and R5 are 100Ω. The comparator 22 detects that one output of the divider 21 has risen with respect to the set voltage value. The comparator 23 detects that the other output of the divider 21 has fallen with respect to the set voltage value. The digital processing circuit 24 performs digital processing such as so-called trigger signal generation or time axis control in waveform observation by digitally processing the outputs of the comparators 22 and 23.

The operation of such a configuration will be described. The input signal is divided by the divider 21 and input to the comparator 22 and the comparator 23. The divider 21 is input to the comparator 22 and the comparator 23 without the amplitude of the input signal being attenuated because of the ratio of the resistance value in the configuration. Further, the rising edge of the same signal is detected by the comparator 22 and the falling edge thereof is detected by the comparator 23. Therefore, the processing can be performed while maintaining the matching and without reducing the amplitude.

FIG. 3 is a block diagram of another embodiment of the present invention. Reference numeral 31 is an input section having a plurality of input terminals, 32 is an attenuator section for attenuating the input from each input terminal, and its common voltage is switched by the control means 6.

Such a configuration will be specifically described. In the attenuator section 32, a switch is provided in each attenuator, and a terminating resistor can be selected. Further, a divider is connected to each input terminal of the selection circuit 33, and the signal is divided into two. The output of this divider is connected to the switches SW1 to SW8. SW1 to SW8 have a configuration in which 2 outputs can be selected with respect to 1 input. The output of each of the switches SW1, SW3, SW5, and SW7 is directly output (so-called through state) or the output via the delay elements d1 to d4 can be connected. . One of the outputs of the switches SW2, SW4, SW6 and SW8, which is connected, is used as a trigger terminal. The output of each of the switches SW2, SW4, SW6, and SW8 can be selected to be connected to either the trigger terminal or the one grounded via the terminating resistor.

SW9 to SW12 are configured so that two inputs can be selected with respect to one output. Therefore, each of the delay elements d1 to d4 or the through state is selected and output.

For this reason, the control means 6 controls ON / OFF of each switch to input to the digital processing circuit 24 via a delay line (delay element) or through. In addition, signals that are not used for measurement are connected to terminating resistors, so that reflection does not occur even if a high-frequency signal is input to an input terminal that is not intended for measurement. Since the trigger terminal can also be placed, it is not necessary to use the external trigger that is usually required in the sampling oscilloscope. In addition, the input signal is input to the digital processing circuit 34 via the delay line, and on the other hand, the trigger signal (trg) can be input to the digital processing circuit 34 without delay, which can be realized with the conventional sampling oscilloscope. It is possible to realize the functions of the pre-trigger that were not there.

[0015]

[Effect of device]

 The present invention improves the efficiency of measuring the input signal in the waveform observation device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a circuit diagram of another embodiment of the present invention.

[Explanation of symbols]

 11 High Frequency Comparator 12 Low Frequency Comparator 13, 14 D Flip Flop 15 Selector 6 Control Circuit

Claims (3)

[Scope of utility model registration request] 1. A first comparator which inputs an analog signal as an object of waveform observation from the outside and outputs a detection signal based on a magnitude relation between a set voltage value and a voltage value of the input signal, and an external waveform observation. Input the analog signal as the target of
The second comparator, which outputs a detection signal based on the magnitude relationship between the set voltage value and the voltage value of the input signal, has a frequency characteristic different from that of the first comparator, and the first comparator and the second comparator. Selection means for selecting and outputting an output; and a control circuit for setting voltage values to be compared by the first comparator and the second comparator and setting signal selection by the selection means. Waveform observation device characterized by. 2. An input terminal for inputting an analog signal as an object of waveform observation from the outside, a cable (R1) having a characteristic impedance of 50Ω connected to the input terminal, one end of which is connected to the cable, and the other end of which is A first transmission line having a characteristic impedance of 100Ω in which a first comparator and a first 100Ω resistor are connected.
A divider comprising (R2) and a second transmission line (R3) having a characteristic impedance of 100Ω, one end of which is connected to the cable and the other end of which is connected a second comparator and a second 100Ω resistor; A first comparator that compares a first output of the divider with a set voltage value, detects that a rising edge has occurred with respect to the set voltage value of the input signal, and outputs a detection signal; and a first comparator of the divider. A second comparator that compares the second output with a set voltage value, detects a fall of the input signal with respect to the set voltage value, and outputs a detection signal; and the first comparator. A waveform observing device, comprising: a digital processing circuit for selecting the output of the comparator and the second comparator. 3. An input terminal for inputting an analog signal as an object of waveform observation from the outside, an attenuator section having means for connecting to the input terminal, attenuating the input analog signal, and switching the level of the ground potential. A selection unit capable of selecting a termination resistance and a signal delay time for the output from the attenuator unit; and a control circuit for setting switching in the attenuator unit and selection of the signal in the selection unit. A waveform observing device, which is provided with.