JP3023599B2 - 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 network analyzer for inputting a measurement signal to a circuit under test, receiving a signal output from the circuit under test, and measuring characteristics of the circuit under test. The present invention relates to a technique for increasing the number of branch outputs without increasing the number and eliminating the need for connector replacement work.

[0002]

2. Description of the Related Art A network analyzer inputs a measurement signal to an external circuit to be measured via an output connector, receives a signal output from the circuit to be measured via an input connector, and receives a signal from the circuit to be measured. Measure frequency vs. amplitude characteristics and frequency vs. phase characteristics.

[0003] For measurement with a network analyzer,
In addition to a single measurement in which a measurement result is obtained only from a signal output from a circuit under test, there is a comparison measurement in which a measurement result is obtained by comparing a signal output from the circuit under measurement with a signal input to the circuit under measurement.

As shown in FIG. 6, a conventional network analyzer 1 transfers a measurement signal output from a measurement signal generation circuit 2 to one of two signal paths by a changeover switch 3 so that the comparison measurement can be performed. One of the signal paths is connected to the output connector 4 for independent measurement, and the other signal path is connected to the resistors R1 and R2.
, And output connectors 6 and 7 are connected to each branch output. A plurality of input connectors 8 and 9 are provided for comparison measurement, and receiving circuits 10 and 11 are connected to the input connectors 8 and 9 respectively.

When a single measurement such as a level measurement is performed, as shown in FIG.
The circuit under test 15 is connected between the input connector 8 and the input connector 8, the changeover switch 3 is connected to the output connector 4, and the circuit under test 15 is measured based on the output of the receiving circuit 10. When performing a comparative measurement such as a phase measurement, a circuit under test 15 is connected between one output connector 6 for branch output and one input connector 8 as shown in FIG. , The other output connector 7 and the other input connector 9
And the changeover switch 3 is connected to the signal branch circuit 5 side, and the output of the two receiving circuits 10 and 11 is compared to measure the circuit under test 15.

[0006]

However, in a network analyzer in which the output connector for independent measurement and the output connector for comparative measurement are independent from each other as described above, it is necessary to perform independent measurement for one circuit to be measured. When comparison measurement is required, a connector replacement operation is required.

[0007] For example, as shown in FIG.
When the characteristic F of the filter having the high loss band B and the low loss band A is measured, it is necessary to accurately measure the attenuation, the phase, the group delay, and the like. Perform a comparative measurement in the setting. In addition, for the high-loss band B, only the measurement of the attenuation amount is generally targeted,
If the measurement of the amount of attenuation in the high loss band B is to be performed in the setting for comparison measurement in the same manner as the measurement in the low loss band A, the level of the signal input from the circuit under test 15 to the input connector 8 is The level of the signal directly input from the output connector 7 to the input connector 9 becomes very large,
The level difference exceeds the isolation between the receiving circuits 10 and 11, and the amount of attenuation in the high-loss band B is F ′ in FIG.
, The measurement becomes apparently small, and an accurate measurement cannot be performed. For example, when the isolation between the receiving circuits 10 and 11 is 90 dB, the level of the leak signal from the receiving circuit 11 to the receiving circuit 10 is input from the input connector 8 even if the attenuation of the circuit under test 15 is 90 dB or more. 90d
It is not possible to measure attenuations above B.

Therefore, when measuring the amount of attenuation in the high-loss band B, the connection between the output connector 7 and the input connector 9 must be disconnected or the setting shown in FIG. However, there is a problem that the replacement efficiency of the connector is required, so that the measurement efficiency is reduced, and the automatic measurement cannot be supported.

Further, if the number of branch outputs is increased from two to three, for example, a new output connector for branch must be provided, and panel processing is required.

SUMMARY OF THE INVENTION The present invention solves this problem, and enables independent measurement and comparison measurement to be performed without replacing connectors, and to increase the number of branch outputs without actually increasing the number of output connectors. The purpose is to provide a network analyzer that can do this.

[0011]

In order to achieve the above object, a network analyzer according to the present invention inputs a measurement signal output from a measurement signal generating circuit (21) to an external circuit to be measured and outputs the signal from the circuit to be measured. In a network analyzer for receiving a signal to be output and measuring characteristics of a circuit under test, a first signal for selectively outputting a measurement signal output by the measurement signal generation circuit to one of a first signal path and a second signal path.
A switch (23), a signal branch circuit (24) for branching a measurement signal output from the first switch to the first signal path into a plurality of signal paths, and outputting the measurement signal to the outside. A first output connector (26) for
A second selector switch (2) for selectively connecting the first output connector to one of the second signal path and a specific signal path branched by the signal branch circuit;
5) and a second signal path for outputting a measurement signal to the outside, which is respectively connected to a signal path other than the specific signal path among the plurality of signal paths branched by the signal branch circuit.
And when the measurement signal is output to the first signal path, the first output connector is connected to the specific signal path, and the measurement signal is output to the second signal path. Is output, the first switch and the second switch are linked so that the one output connector is connected to the second signal path.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a network analyzer 20 according to an embodiment.

In FIG. 1, a network analyzer 2
0 measurement signal generation circuit 21 is connected to a measurement control unit 35 described later.
Varies the frequency and output level of the measurement signal to be output.

The measurement signal output from the measurement signal generation circuit 21 is input to the common terminal 23a of the first switch 23. The first changeover switch 23 is configured by, for example, a high-frequency relay, and connects the common terminal 23a to either the terminal 23b or the terminal 23c by a signal from the measurement control unit 35. One terminal 23b has resistors R1 and R
2 is connected to the other terminal 23
The terminal 25c of the second changeover switch 25 is connected to the c side.

The resistance values of the resistors R1 and R2 of the signal branch circuit 24 are equal to the output impedance (for example, 50Ω) of the measurement signal generation circuit 21, and the input signal is distributed into equal powers and output.

The second changeover switch 25 is constituted by a high-frequency relay similarly to the first changeover switch 23, and one terminal 25b is connected to the branch output side of one resistor R1 of the signal branch circuit 24. Second changeover switch 25
Is connected to a first output connector 26, and the branch output side of the other resistor R 2 of the signal branch circuit 24 is connected to a second output connector 27.

The second changeover switch 25 is connected to the measurement controller 3
5 is switched in conjunction with the first changeover switch 23. That is, when the first switch 23 is connected to the terminal 23b, the second switch 25 is connected to the terminal 25b.
When the first changeover switch 23 is connected to the terminal 23c, the second changeover switch 25 is connected to the terminal 2c.
5c side.

Note that between the measurement signal generating circuit 21 and the common terminal 23a of the first changeover switch 23, between the terminal 23b of the first changeover switch 23 and the signal branching circuit 24, and between the terminals 23c of the first changeover switch 23. And the second changeover switch 2
5, between the common terminal 25a of the second changeover switch 25 and the first output connector 26, between the signal branch circuit 24 and the terminal 25b of the second changeover switch 25,
Each signal path between the signal branch circuit 24 and the second output connector 27 is set such that its transmission impedance is equal to the output impedance of the measurement signal generation circuit 21. The length of a signal path from the terminal 23b of the first changeover switch 23 to the first output connector 26 via the signal branch circuit 24 and the second changeover switch 25, and the terminal 23b of the first changeover switch 23 The signal path is formed so as to be approximately equal to the length of a signal path from the signal path through the signal branch circuit 24 to the second output connector 27.

On the other hand, the network analyzer 20 is provided with first and second input connectors 28 and 29, and the first receiving circuit 30 receives a signal input through the first input connector 28. And the second input connector 29
Is received by the second receiving circuit 31.

The first and second receiving circuits 30 and 31 receive a signal component of the same frequency as the measurement signal output from the measurement signal generation circuit 21 among the signals input to the input connectors 28 and 29, The frequency is converted to a constant intermediate frequency and output to the data processing unit 32.

The data processing unit 32 includes the receiving circuits 30, 3
1 is converted to a digital signal, and the level,
Detect the phase and the like.

The display controller 33 displays a screen corresponding to the measurement item on the display 34, displays the measurement data obtained by the data processor 32 on the screen, and displays the characteristics of the circuit under test in a graph. indicate.

The measurement control unit 35 is constituted by a microcomputer, and according to the measurement items and measurement conditions set by operating the operation unit 36, the measurement signal generation circuit 21, the first and second changeover switches 23, 25, It controls the receiving circuits 30 and 31 and outputs information such as measurement items and measurement conditions to the data processing unit 32 and the display control unit 33 to perform data processing and display processing corresponding to the information.

The measurement control unit 35 includes a manual measurement control mode for controlling each unit in accordance with the operation of the operation unit 36, and an automatic control for controlling each unit in accordance with a measurement program preset by operation of the operation unit 36. It has a measurement control mode.

FIG. 2 is a flowchart showing a control procedure performed by the measurement control unit 35 in accordance with the measurement program of the circuit under test 15 having the bandpass characteristic F as shown in FIG.

The operation of the network analyzer 20 according to one embodiment will be described below with reference to FIG. In advance, as shown in FIG.
It is assumed that the circuit under test 15 is connected to the first input connector 28 by a cable, and the second output connector 27 and the second input connector 29 are connected by a cable. The measurement program includes a measurement lower limit frequency f
It is assumed that 0, frequencies f1 and f2 between the high loss band and the low loss band of the bandpass characteristic F, the measurement upper limit frequency f3, and the frequency variable step Δf are specified.

Prior to the measurement, various correction data obtained by directly connecting a cable between the first output connector 26 and the first input connector 28 are stored in the data processing unit 32, and the data processing unit 32 The data obtained at the time of measurement of the circuit under test is corrected with the correction data, and level detection and phase difference detection are performed.

At the start of the measurement, the first switch 2
3 is a terminal 23c side, and the second changeover switch 25 is a terminal 25c.
The measurement frequency fm, that is, the frequency of the measurement signal output from the measurement signal generation circuit 21 and the reception frequency of the reception circuit 30 are set to f0, and the output level of the measurement signal is set to the reference level L (for example, 0 dBm). Is set to (S
1 to S3).

Then, the level of the received output of the first receiving circuit 30 at this time is detected by the data processing section 32, and the difference between the detected level and the reference level L is calculated as the amount of attenuation at this frequency. Is stored in a memory (not shown) (S4).

Thereafter, the measurement frequency fm is swept up to the frequency f1 in Δf steps, and the amount of attenuation for each frequency is detected (S5, S6).

During the level measurement, the signal branch circuit 24 is disconnected from the path of the measurement signal by the first and second changeover switches 23 and 25. Therefore, the second receiving circuit 3
1, a signal of a small level determined by the isolation between the terminals of the first and second changeover switches 23 and 25 is input, and the level of the signal input to the first receiving circuit 30 is Since the attenuation is small due to the high loss, the difference is smaller than the isolation between the receiving circuits 30 and 31. Therefore, the leakage signal from the second receiving circuit 31 included in the output of the first receiving circuit 30 can be ignored, and the data processor 32 accurately detects the attenuation of the circuit under test 15.

For example, the first and second changeover switches 23,
The isolation between the 25 terminals is 80 dB, the isolation between the receiving circuits 30 and 31 is 90 dB, and the attenuation of the circuit under test 15 at frequencies f0 to f1 is 100 dB.
If the level is in the range of dB to 40 dB, the level of the signal input to the second input connector 29 is -80 dBm (= 0-80), so that the second receiving circuit 31 to the first receiving circuit 30
The level of the leakage signal to -170 dBm (= -80-9)
0). On the other hand, the level of the signal input to the first input connector 28 ranges from -100 dBm (= 0-100).
−40 dBm (= 0−40), which is a level negligible to the level −170 dBm of the leakage signal. Therefore, the attenuation of the circuit under test 15 can be measured sufficiently accurately by the output of the first receiving circuit 30. it can.

When the measurement frequency fm reaches f1, the first switch 23 is connected to the terminal 23b, and the second switch 25 is connected to the terminal 25b (S7).

As a result of this switch switching, the measurement signal output from the measurement signal generation circuit 21 is equally branched by the signal branch circuit 24, one of which is input to the circuit under test 15 via the first output connector 26, and The signal is attenuated by the measuring circuit 15 and is input to the first receiving circuit 30 via the first input connector 28, and the other is input to the second receiving circuit 31 via the second output connector 27 and the second input connector 29. Is input to

Then, the data processing unit 32 includes the first and second
The level difference between the reception outputs of the receiving circuits 30 and 31 is determined as the amount of attenuation of the circuit under test 15, and the first and second receiving circuits 3
The phase difference φ between the received outputs 0 and 31 is detected and stored (S8).

Thereafter, the measurement frequency fm is swept to the frequency f2 in steps of Δf, and the attenuation and the phase difference for each frequency are detected by the comparison measurement (S9, S10). During the comparison measurement, the level difference between the signal input to the first receiving circuit 30 and the signal input to the second receiving circuit 31 is sufficiently smaller than the isolation between the receiving circuits.
Second receiving circuit 3 included in the output of first receiving circuit 30
Leakage signals from 1 are negligible.

When the measurement frequency fm reaches the frequency f2, the first changeover switch 23 is connected to the terminal 23a,
The switch 25 is connected to the terminal 25a, and the same level measurement as in the above-described processes S4 to S6 is performed until the measurement frequency fm reaches f3 (S11 to S14).

When the measurement up to the frequency f3 is completed, the attenuation characteristic F and the phase characteristic P of the circuit under test 15 are displayed on the display 34 based on the measurement results up to that point, for example, as shown in FIG. (S15).

As described above, in the network analyzer 20 of this embodiment, the first output connector 26 is used so that the first output connector 26 can be used for both the output connector for independent measurement and the output connector for comparison measurement. Since the changeover switch 23 and the second changeover switch 25 are linked,
It is possible to switch between a single measurement such as a level measurement and a comparison measurement without replacing a connector, thereby improving measurement efficiency and easily supporting automatic measurement.

As in the prior art, the number of branch outputs of a network analyzer in which the output connector for independent measurement and the output connector for comparison measurement are independent is, for example, two to three.
When it is desired to add one to another, it is not necessary to newly provide a branch output connector, and panel processing becomes unnecessary.

Although the automatic measurement has been described here, the measurement control unit 35 operates the first changeover switch 23 by operating the operation unit 36 even when the measurement is performed manually.
And the second changeover switch 25 in the same manner as described above.

In the above embodiment, the number of branch outputs is 2
However, as shown in FIG. 5, the present invention can be similarly applied to a network analyzer having three branch outputs. In this case, the signal branch circuit 2
4 ′ is a three-branch type including four resistors R0 to R3,
The two branch outputs are respectively connected to two output connectors 27a and 27b provided as second output connectors,
Correspondingly, the input connector 38 and the third receiving circuit 39
Is provided.

In the above embodiment, the measurement control unit 35
The first and second changeover switches 23 and 25 are switched by the control of the above, but the first and second changeover switches 23 and 25 are operated by one key operation.
The second changeover switches 23 and 25 may be directly switched.

In the above embodiment, the receiving circuits 30 and 31 are provided for the input connectors 28 and 29, respectively. However, for example, only one receiving circuit is provided for two input connectors, The present invention can also be applied to a network analyzer configured to connect one of the two input connectors to the receiving circuit. Even in this case, by configuring the signal output unit in the same manner as in the above-described embodiment, the influence of the isolation of the changeover switch on the receiving circuit side can be reduced.
Single measurement and comparative measurement can be performed without replacing the connector.

[0045]

As described above, in the network analyzer according to the present invention, the first changeover switch for selectively outputting the measurement signal output from the measurement signal generation circuit to one of the first and second signal paths. A signal branch circuit for branching a measurement signal output from the first changeover switch to the first signal path to a plurality of signal paths, a first output connector for outputting the measurement signal to the outside, A second changeover switch for selectively connecting one output connector to one of the second signal path and a specific signal path branched by the signal branch circuit; And a second output connector for outputting a measurement signal to the outside, the measurement signal being provided in the first signal path. Is output, the first output connector is connected to the specific signal path, and when the measurement signal is output to the second signal path, the first output connector is connected to the second signal path. As described above, the first changeover switch and the second changeover switch are linked.

For this reason, the first output connector can be used as either an output connector for independent measurement or an output connector for comparison measurement. No need for replacement work,
Measurement efficiency is improved, and automatic measurement becomes possible. Also,
When the number of branch outputs is increased, it is not necessary to newly add a connector, and panel processing becomes unnecessary.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a processing procedure of a main part of the embodiment.

FIG. 3 is a characteristic diagram of a measurement object.

FIG. 4 is a diagram showing measurement results.

FIG. 5 is a block diagram showing another embodiment.

FIG. 6 is a block diagram showing a schematic configuration of a conventional device.

FIG. 7 is a characteristic diagram of a measurement object.

[Explanation of symbols]

 15 Circuit Under Test 20 Network Analyzer 21 Measurement Signal Generating Circuit 23 First Changeover Switch 24 Signal Branching Circuit 25 Second Changeover Switch 26 First Output Connector 27 Second Output Connector 28 First Input Connector 29 Second Input connector 30 First receiving circuit 31 Second receiving circuit 32 Data processing unit 33 Display control unit 34 Display 35 Measurement control unit 36 Operation unit

Claims (1)

(57) [Claims] 1. A network analyzer for inputting a measurement signal output from a measurement signal generating circuit (21) to an external circuit under test, receiving a signal output from the circuit under test, and measuring characteristics of the circuit under test. A first changeover switch (23) for selectively outputting a measurement signal output from the measurement signal generation circuit to either a first or second signal path; and A signal branch circuit (24) for branching a measurement signal output to a signal path into a plurality of signal paths, a first output connector (26) for outputting the measurement signal to the outside, and the first output connector , A second switch (2) selectively connected to one of the second signal path and a specific signal path branched by the signal branch circuit.
5) a second output connector (27) connected to a signal path other than the specific signal path among the plurality of signal paths branched by the signal branch circuit, and for outputting a measurement signal to the outside; When a measurement signal is output to the first signal path,
When the first output connector is connected to the specific signal path and a measurement signal is output to the second signal path, the first output connector is connected to the second signal path, A network analyzer wherein the first switch and the second switch are linked.