JP3507175B2 - Network analyzer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring impedance of a test object with high accuracy.

[0002]

2. Description of the Related Art As an example of the prior art, there is an example of low impedance measurement using a .pi. Circuit jig. about this,
This will be described with reference to FIG. The configuration of this device is shown in FIG.
As shown in FIG. 3, the network analyzer 200, the π circuit jig 220, and the device under test (DUT) 100 are included. The calibration of the network analyzer is performed in advance in each open / short / load connection state to eliminate the error effect of the π circuit jig 220.

The π circuit jig 220 is an adapter for converting the characteristic impedance 50Ω of the input terminal 201 and the output terminal 206 of the network analyzer into a low input / output characteristic impedance fixed to 12.5Ω and connecting it to the DUT 100. It is inserted to measure a low-impedance crystal oscillator etc. with high accuracy. However, the DUT 10 having a lower impedance than the fixed low impedance
In the case of 0, the level difference from the short calibration becomes small, so that problems such as measurement variations, measurement errors, and poor reproducibility occur. This error or fluctuation is 2-5%
It may be an error value. Regarding this problem, an example in which the level difference from the short calibration is reduced will be described. Impedance to be measured Z = 2Z0 ×
It can be expressed as {(Vs-Vm) / Vm}. Here, Z0 is the characteristic impedance of the measurement system, Vs is the measurement value calibrated by the network analyzer when both ends of the DUT are short-circuited, and Vm is the measurement value when the DUT is actually connected. From the above equation, it can be seen that it is necessary to increase (Vs-Vm) in order to measure the impedance Z without variation. Further, it is necessary to measure under the condition that the Vm measurement value does not become small. From these, it can be understood that there is a range with good measurement accuracy.

When measuring a high impedance DUT, the DUT is directly connected to the network analyzer 200 as shown in FIG. 3B. The input / output impedance of the network analyzer at this time is 50Ω
Therefore, in the case of the DUT 100 having a high impedance that greatly deviates from the impedance of the measurement system, the level at the measurement input terminal 206 becomes low, and the same problem of measurement error occurs.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, D
DUT having an impedance in which the input / output impedance of the UT100 and the impedance of the measurement system are largely deviated
In the case of measuring the impedance of 100, there were problems such as measurement variations, measurement errors, poor reproducibility, and the like, and there was a problem that the measurement accuracy deteriorated.

Therefore, an object of the present invention is to provide an impedance measuring instrument which further improves the measurement accuracy by providing an input / output impedance converter close to the input / output impedance of the DUT 100.

[0007]

FIG. 1 shows a first solution according to the present invention. In order to solve the above problems, the network analyzer 200 according to the configuration of the present invention is used.
Switching resistor group 250 inserted in series between the output end on the side of the signal generator 210 and the input end 100in of the DUT100 in order to measure the high impedance with high accuracy, and the switching connected in parallel with the measurement input terminal of the network analyzer. A resistor group 270 is provided, and π is inserted between the signal output terminal of the switching resistor group 250 and the DUT100 input terminal 100in to measure the low impedance with high accuracy.
A circuit resistance group 230 and a π circuit resistance group 240 inserted between the output terminal 100out of the DUT 100 and the measurement input terminal 206.
Is provided. As a result, the network analyzer is used to realize a highly accurate impedance measuring device of the DUT to be measured from high impedance to low impedance.

FIG. 2 shows a second solution according to the present invention. In order to solve the above problems, in the configuration of the present invention, the π circuit resistance group 230 for switching from low impedance to high impedance measurement and the DUT 100 output are inserted between the signal output terminal of the network analyzer 200 and the DUT 100 input terminal 100in. The constituent means is provided with a π circuit resistance group 240 inserted between the end 100out and the measurement input terminal 206. This also realizes a highly accurate impedance measuring device of the DUT to be measured from high impedance to low impedance by using the network analyzer.

When measuring the impedance of the DUT to be measured, which is higher than the impedance at the input / output end on the network analyzer 200 side, the output end on the signal generator 210 side in the network analyzer 200 and the DU
The switching resistor group 250 inserted in series between the T100 input terminals 100in and the switching resistor group 270 connected in parallel with the measurement input terminal of the network analyzer may be provided.

[0010]

The switching resistor group 250 inserted in series at the output end of the signal generator 210 has a role of obtaining a relatively large change amount (Vs-Vm) of the measured value at the time of measuring the high impedance DUT. Further, the switching resistance group 270 connected in parallel to the DUT measurement terminal 206 has a relatively large change amount (Vs-Vm) in the measured value at the time of measuring the high impedance DUT, and thus the measurement accuracy is similarly improved. There is a role. Also, as a low impedance measurement resistance group,
Signal output terminal of network analyzer 200 and DUT
Π circuit resistance group 230 in series between 100 input terminals 100in
By inserting the π circuit resistance group 240 in series between the DUT 100 output terminal 100out and the measurement input terminal 206, there is an effect of making both ends of the DUT a predetermined low impedance condition, and Since a relatively large amount of change (Vs-Vm) in the measured value can be obtained during DUT measurement, there is an effect of improving the measurement accuracy.

[0011]

EXAMPLE The example of the present invention is an example of an impedance measuring device that is compatible with high impedance and low impedance. As in the impedance converter shown in FIG. 1, a switching resistor group 250 inserted in series and a switching resistor connected in parallel with the measurement terminal 206 are provided on the output side of the signal generator 210 of the network analyzer 200 for high impedance measurement. The resistor group 270 is provided inside the network analyzer 200. The resistance R00 is, for example, 10 KΩ, the resistance R01 is 3 KΩ, and the resistance R0n is 50 Ω. The resistance value is provided about every three times, and the relay control unit 28 has relays K01 to K0n for opening and closing the resistance value.
A 0 selects the desired relay that approximates the impedance of the DUT 100. The same applies to the measurement terminal 206 side, and the resistance R80 is, for example, 10 KΩ, and the resistance R
81 is 3 KΩ, and the resistance R8n is 50Ω. A desired relay having the relays K41 to K4n for opening and closing the relay and having the impedance close to the impedance of the DUT 100 is selected by the relay control unit 280. These relays are also used at the time of calibration, and a correction value for correcting the impedance deviation of each resistance group is previously obtained so that they do not become an error factor at the time of measurement as in the conventional case.

Further, as a low impedance measuring resistance group, a signal output terminal of the network analyzer 200 and D
Π circuit resistance group 2 in series between UT100 input terminals 100in
A configuration in which the π circuit resistance group 240 is inserted in series between the DUT 100 output terminal 100out and the measurement input terminal 206 is provided outside the network analyzer 200. For example, π for impedance conversion from 50Ω to 2Ω
As an example of the circuit resistance value, R00 = R81 = 50Ω, R00
21 = R51 = 56Ω, R31 = R71 = 430Ω, R
41 = R61 = 2Ω. Relay K20, K30
Is used when measuring the impedance in the vicinity of 50Ω, and is used for π resistance networks R21, R31, R41 and R51,
R61 and R71 are for impedance measurement in the vicinity of 150Ω, and π resistance networks R2m, R3m, R4m and R5m,
R6m and R7m are for impedance measurement in the vicinity of 10 KΩ. Relays K20-K2m, K for opening and closing these
A desired relay having 60 to K6m, K31 to K3m, and K41 to K4m and close to the impedance of the DUT 100 is selected by the relay control unit 280. These relays are also used during calibration, and a calibration correction value is obtained in advance so as not to cause an error factor during measurement.

By measuring the impedance conversion resistance group having the above configuration by opening and closing a desired relay corresponding to the impedance of the DUT and performing impedance conversion close to the impedance of the DUT, the level difference from the short calibration is sufficient. The measurement can be performed as a large level change or the level at the measurement input terminal 206 can be measured to be high, so that the conventional problems can be improved and impedance measurement with higher measurement accuracy can be realized.

In the above description of the embodiment, the switching resistance group 2
50 and the switching resistance group 270 are built in the network analyzer, and the π circuit resistance group 230 and the π circuit resistance group 240 are provided outside, however, they may be built in the network analyzer if desired.
It may be provided externally.

In the description of the above embodiment, the π circuit resistance group 23
Although the description has been made in the case where the resistance values of 0 and the π circuit resistance group 240 are set to the low impedance, the π circuit resistance that gives the resistance value applied up to the high impedance is added, if desired, with the configuration shown in FIG. It is also possible to have a structure that covers from low impedance to high impedance, and it is possible to carry out in the same manner.

When measuring the impedance of the DUT to be measured, which is higher than the impedance at the input / output end of the network analyzer 200, the π circuit resistance group 230
And the π circuit resistance group 240 are deleted, and the switching resistance group 25
0 and 270 may be provided alone, and the same implementation is possible.

[0017]

Since the present invention is configured as described above, it has the following effects. The switching resistor group 250 inserted in series at the output end of the signal generator 210 has a relatively large change amount (Vs-Vm) in the measured value at the time of high impedance DUT measurement, and thus has the effect of improving the measurement accuracy. is there. Further, the switching resistor group 270 connected in parallel to the DUT measurement terminal 206 has a change amount (V) of the measured value at the time of the high impedance DUT measurement.
Since s-Vm) is obtained relatively large, it has an effect of improving the measurement accuracy. Further, as a low impedance measurement resistance group, a π circuit resistance group 230 is inserted in series between the signal output terminal of the network analyzer 200 and the DUT100 input terminal 100in, and a series circuit is inserted between the DUT100 output terminal 100out and the measurement input terminal 206. By inserting the π circuit resistance group 240 into the DUT, both ends of the DUT can be set to a predetermined low impedance condition, and a relatively large change amount (Vs−Vm) of the measured value can be obtained at the time of measuring the low impedance DUT.
This has the effect of improving the measurement accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first impedance measuring device of the present invention.

FIG. 2 is a configuration diagram of a second impedance measuring device of the present invention.

FIG. 3A is a configuration diagram of a conventional low impedance measuring device. (B) It is a block diagram of the conventional high impedance measuring device.

[Explanation of Codes] K00 to K0m, K20 to K2m, K30 to K3m, K
41 to K4m, K51 to K5h, K61 to K6m Relays R21, R31, R41 π resistance networks R51, R61, R71 Resistance R81 Resistance 100 Test object (DUT) 200 Network analyzer 201 Input terminal 206 Measurement input terminal 210 Signal generator 220 π circuit jig 230, 240 π circuit resistance group 250, 270 switching resistance group 280 relay control section

Claims (3)

(57) [Claims] 1. An impedance measuring device for a device under test (DUT) using a network analyzer, wherein an output end on a signal generator (210) side and an input end (10) of a DUT (100) in a network analyzer (200).
Switching resistor group (250) inserted in series between 0 in)
And a switching resistor group (270) connected in parallel with the measurement input terminal of the network analyzer, the signal output end of the switching resistor group (250) and the DUT.
The π circuit resistance group (230) inserted between the (100) input terminal (100 in) and the DUT (100) output terminal (100 ou)
A network analyzer characterized in that a π circuit resistance group (240) inserted between t) and a measurement input terminal (206) is provided, and the above is provided. 2. An impedance measuring device of a device under test (DUT) using a network analyzer, wherein a signal output terminal of the network analyzer (200) and D
It is inserted between the UT (100) input end (100in) and switches from low impedance to high impedance measurement. Π circuit resistance group (230), DUT (100) output end (100out) and measurement input terminal (206). A network analyzer characterized by comprising a π circuit resistance group (240) to be inserted between them and comprising the above. 3. An impedance measuring device for a device under test (DUT) having a higher impedance than the impedance of an input / output terminal on the side of the network analyzer (200) by using the network analyzer. 210) side output terminal and DUT (100) input terminal (10
Switching resistor group (250) inserted in series between 0 in)
And a switching resistor group (270) connected in parallel with the measurement input terminal of the network analyzer, and the above is provided.