JPH0539501Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pulse signal probe.

[Prior Art] FIG. 4 shows a pulse signal probe using a conventional coaxial transmission line.

When measuring an object to be measured 5 made of a logic IC such as an ECL, when this probe 6 is brought into contact with the object to be measured 5, the ground terminal 5b on the object to be measured 5 and the grounding conductor 6b of the probe 6 are connected to DC ( It has continuity in terms of direct current (DC).

[Problems to be solved by the invention] However, in such a structure, when the grounding conductor 6b of the probe 6 is connected to the power supply terminal 5c of the device under test 5, the oscilloscope (not shown) etc. connected to the probe 6 The power supply terminal 5c could not be used as a measurement ground terminal because the voltage would build up at the ground terminal and cause a shock, destroying the internal circuitry of the oscilloscope.

Therefore, normally, the signal terminal 5a and the ground terminal 5
If an attempt is made to use B, the distance between them is often large, and especially in the microwave band, the lead inductance increases and the measured waveform is likely to be disturbed.

The present invention was devised to eliminate these drawbacks, and its purpose is to use the power supply terminal near the signal terminal of the device under test as the measurement ground terminal, so that the pulse waveform is not disturbed. It is an object of the present invention to provide a pulse signal probe capable of simultaneously evaluating high-frequency characteristics and low-frequency characteristics of an object to be measured under the same conditions, and also capable of easily performing this evaluation with a single probe.

[Means for Solving the Problems] In order to solve the above problems, a pulse signal probe according to the present invention includes a pulse signal probe 1 having a signal conductor 1a and a grounding conductor 1b. 1b is cut in a DC manner,
This cut section 1bb is connected at high frequency with a capacitor 2 to serve as an AC ground conductor, and one end is electrically connected to the front side of the cut section, and the other end is connected to the terminal voltage terminal 5b of the object to be measured 5. It is characterized by having a DC arm conductor 3 connected in a DC manner.

[Operation] To explain the operation of the above configuration, probe 1
The grounding conductor 1b is cut in a DC manner, connected in a high frequency manner by a capacitor 2, and connected to a signal terminal 5.
The high frequency characteristics can be measured by bringing the signal conductor 1a of the probe 1 into contact with the probe 1a and by contacting the grounding conductor 1b with the power supply terminal 5c. Furthermore, by simultaneously bringing the DC ground conductor 3 of the probe 1 into contact with the termination voltage terminal (earth terminal) 5b, the low frequency characteristics can be measured.

[Example] Hereinafter, an example of the pulse signal probe of the present invention will be described.

FIG. 1 is a diagram showing a pulse signal probe.

In the figure, reference numeral 1 denotes a coaxial transmission line composed of a semi-rigid cable or the like, which functions as a probe. This probe 1 has a signal conductor 1a and a ground conductor 1b.

A portion of the ground conductor 1b is cut off, and a capacitor 2 is connected to this cut portion 1bb.

Therefore, the signal conductor 1a of the probe 1 can contact the signal terminal 5a of the object to be measured 5, and the ground conductor 1b can contact the power supply terminal 5c.

Further, the grounding conductor 1b and the grounding terminal 5b are connected by the DC grounding conductor 3 without using the capacitor 2.

Figure 2a shows the electrical equivalent circuit of only the probe 1, Figure 2b shows the electrical equivalent circuit of the device under test 5 when it is in operation, and Figure 2c shows the electrical equivalent circuit when measuring the device 5 using the probe. This is an electrical equivalent circuit.

As shown in Figure 2b, the ECL5 as the object to be measured has a Vcc (collector voltage) of 0V,
Vee (emitter voltage) is -5.2V, VT (terminal voltage of output Q) is -2V, and output Q is an emitter follower, so it is connected to terminal VT5 through a 50Ω resistor.
b (-2V).

In this case, if VT remains at -2V, the outer casing (ground potential) of the observation system such as the synchroscope must be at the same potential, that is, -2V, which may damage the measurement circuit inside the synchroscope. , and the outer casing has a potential that is dangerous to the human body, so during measurement, VT is raised from -2V to 0V and the outer casing of the observation system is set to GND.

This causes Vee to go from −5.2V to −3.2V and Vcc
are shifted from 0V to +2V, respectively.

As a result, the bias voltage of the entire ECL5 is shifted, and the terminal voltage of output Q is 0V (DC 0V)
This makes it possible to measure with a synchroscope. At this time, even if the bias voltage of the entire ECL 5 is shifted, the function of this ECL 5 does not change.

In other words, as shown in FIG. 2c, the power supply terminal 5c
is a +2V power supply and is used as a high frequency ground, and the power supply terminal 5d is -3.2V (5.2V -
2V=3.2V), the terminal voltage of the signal terminal 5a shifts by +2V and becomes 0V, which becomes a signal that can be observed with a synchroscope, and the power supply VT of the terminal 5b becomes GND (in terms of direct current).

At this time, the GND of the observation system may be taken from the VT of ECL5, or may be taken from another source as long as it serves as the reference (OV).

Therefore, the grounding conductor 1b of the probe 1 is
Since it is cut in a DC manner and connected in a high frequency manner by a capacitor 2, high frequency characteristics can be measured by contacting the signal conductor 1a of the probe 1 to the signal terminal 5a and the grounding conductor 1b to the power supply terminal 5c. .

At the same time, connect probe 1 to ground terminal 5b.
By bringing the DC grounding conductor 3 into contact, low frequency characteristics can be measured. At this time, the GND of the observation system is unified.

Next, FIG. 3 is a diagram showing another embodiment of the present invention.

In this figure, a resistor 7 is inserted into the DC ground conductor 3 described above.

The inductance of the capacitor 2 and the DC ground conductor 3 forms a resonant circuit, and if this resonant frequency falls within the measurement band, it may adversely affect the measurement. To reduce this effect
If a resistor 7 is inserted in series with the DC ground conductor 3,
It is possible to lower the Q of the resonant circuit.

Note that the DC grounding conductor 3 itself may have a resistance component.

In the above embodiment, the shape of the capacitor 2 is not limited, but for example, the shape of the capacitor 2 is
A 1 mm square capacitor 2 with double-sided electrodes (width: 0.4 mm) was soldered to a part of the cut portion 1bb formed with a width of 0.2 mm, and good characteristics were obtained. Furthermore, multiple capacitors are provided around the cutting part 1bb,
It may be a donut-shaped capacitor that covers the periphery of the cut portion 1bb.

Further, in the above embodiment, a coaxial transmission line was used as the probe 1, but any other matching line such as a triplate line may be used.

[Effects of the invention] As explained above, according to the pulse signal probe of the invention, the high-frequency characteristics and low-frequency characteristics of the object to be measured can be measured simultaneously without disturbing the pulse waveform and causing measurement errors. Comprehensive characteristic evaluation is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the pulse signal probe of the present invention, FIG. 2 a, b, and c are electrical equivalent circuit diagrams of the probe, and FIG. Figure 3 shows how to obtain the GND of
The figure shows another embodiment of the present invention, and FIG.
It is a figure showing a conventional probe. 1... Coaxial transmission line, 1a... Signal conductor, 1b
...Grounding conductor, 2...Capacitor, 3...
DC grounding conductor, 5...Object to be measured, 5a...Signal terminal, 5b...Earth terminal, 5c...Power terminal, 5a...Power terminal, 7...Resistor.

Claims (1)

[Scope of utility model registration request] In a pulse signal probe 1 having a signal conductor 1a and a grounding conductor 1b, the grounding conductor 1b is cut in a DC manner, and this cut portion 1bb is connected in a high frequency manner with a capacitor 2 to serve as an AC grounding conductor. At the same time, a DC grounding conductor 3 has one end electrically connected to the front side of the cutting part and the other end DC-connected to the termination voltage terminal 5b of the object to be measured 5.
A pulse signal probe characterized by: