JP3075322B2 - High frequency unbalanced characteristic evaluation tester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a common mode test signal containing a high frequency component to a line such as a communication line or a power line connected to a device under test such as a telephone so as to determine whether noise is heard from a receiver. The present invention relates to a high-frequency unbalance characteristic evaluation tester for measuring and evaluating noise audible immunity characteristics due to high-frequency unbalance-balance conversion, which is the limit of proof stress.

[0002]

When AM modulated sine wave, such as V ₀ shown in FIG. 8 (a) BACKGROUND OF THE INVENTION is used in radio broadcasting and CB radio or the like is induced in communication lines and power lines, common mode (longitudinal) current Intrudes into a device such as a telephone connected to the communication line or the power line. Then, noise often occurs from the receiver due to the unbalanced impedance of the equipment circuit, the detection characteristics of the entire equipment circuit due to the use of a large number of semiconductor circuit elements, and the like. At this time, a waveform such as V _R shown in FIG. 8B is generated between the receiver terminals, which drives the receiver diaphragm to generate noise sound pressure.

When V ₀ is an AM-modulated sine wave as shown in FIG. 8A, V _R is, for example, as described in the Transactions of the Institute of Electronics, Information and Communication Engineers, Spring Meeting, SB-3-2, 1992.
_A VH waveform (hereinafter, also referred to as a carrier wave) composed of a carrier component obtained by reducing the ₀ waveform as it is, and a voice modulation wave waveform (hereinafter, VL is referred to as a VL waveform such as a VL waveform obtained by detecting an AM modulated wave in the entire telephone circuit. (Also referred to as a modulated wave).

FIG. 9 is a block diagram showing a conventional configuration of a noise audible immunity test system for evaluating the presence or absence of noise audibility from a receiver by applying such an AM modulated sine wave to a device under test. is there. As shown in the figure, a device under test (EUT) 51 such as a telephone is supported at a constant height h from above the pseudo ground by an insulating support base 52. EUT
The receiver of the transmitter / receiver 53 of 51 is fitted into the microphone 54 via the acoustic coupler 55. The noise from the earpiece converted by the microphone 54 into an electric signal is a level meter 5 that indicates the electric signal output of the microphone 54.
6 is displayed. That is, the audible noise sound pressure P from the receiver
Can be recognized by the level meter 56.

The handset 53 has a pseudo hand circuit 57 equivalent to the ground impedance when a handset is held by a hand.
Is connected. Handset 53 and microphone 54
Is housed in a sound-insulating box that prevents ambient noise other than audible noise from the receiver from entering the microphone 54.

[0006] A communication line between the EUT 51 and an opposing communication device 61 such as a pseudo-switch is connected to a test signal applier 60 for applying a test AM modulated sine wave (test signal) to the EUT 51 in a common mode. . Test signal applicator 60
Is a test signal generator (SG) 59 for generating a test signal.
And a common mode choke coil 60 for allowing the applied test signal to be applied only to the EUT side without being applied to the opposing communication device 61 side. Note that E
A line opening switch 63 is provided between the UT 51 and the test signal applicator 60.

In such a test system, when an AM modulated sine wave such as V ₀ shown in FIG. 8A is applied to a communication line in a common mode as a test signal, a common mode current iv flows through the communication line. To enter the EUT 51. Then, the common mode current is converted and detected by an unbalanced impedance in the circuit of the EUT 51, a semiconductor circuit, or the like, and generates an audible noise in the receiver. Audible noise from the handset enters microphone 54 where it is converted to an electrical signal. Since the level meter 56 fluctuates according to the electric signal, the measurer can know the noise sound pressure P from the vibration. Thus, the noise sound pressure from the receiver is extracted by acoustic coupling.

The audible immunity of the EUT 51 is obtained as an open-end common mode voltage when the applied voltage when the sound pressure P (= P ₀ ) occurs at the limit where noise starts to be heard and the line opening switch 63 is opened. . Therefore, if the open-end common mode voltage is measured while changing the carrier frequency f of the test signal from the SG 59 and the measured value is plotted, the noise audible immunity characteristic of the EUT 51 can be obtained.

FIG. 10 shows one example of a system including a plurality of EUTs.
This shows a case where two test signal applicators 60 are connected. In a system such as a key telephone device or a business phone, slave phones S ₁ , S ₂ ,..., _SM are connected to the main device (M) 70 via an extension such as a home bus line. On the opposite communication line side, the opposite telephone S _N 71
Is connected. Then, using the test signal from the test signal applicator 60, the audible immunity of such a system is evaluated.

[0010]

To evaluate the noise audible immunity characteristics of various telephones using the characteristic evaluation tester shown in FIG. 9, it is necessary to swing the level meter 56 properly corresponding to the noise sound pressure. become. However, the shape of the earpiece varies depending on the receiver. When the earpieces having different shapes are attached to the acoustic coupler 55, the fitting condition between the receiver and the acoustic coupler 55 changes, and the acoustic coupler 55 may not be properly coupled to the microphone 54 in some cases. In such a case, there is a problem that the swing of the level meter 56 is unstable especially near the audible sound pressure limit, and it is difficult to detect an appropriate sound pressure level.

In order to evaluate the audible immunity of the whole system by the configuration shown in FIG. 10, the receiver of the main unit 70 and the sub-telephone sets S ₁ , S ₂ ,.
Noise sound pressure from handset corresponding to S _M and the opposite telephone _{S N (P 1, P 2} , ···, P N) were each measured,
It is necessary to know which corresponds to the smallest audible immunity. However, if the test system shown in FIG. 9 is used for such a plurality of EUTs, an acoustic coupler 55 and a sound insulation box 58 corresponding to each EUT are required. Therefore, there is a problem that the equipment becomes enormous, and a considerable time is required for the test system arrangement work such as coupling.

According to the present invention, instead of the noise sound pressure measurement by such an acoustic coupling method, a noise signal generated between receiver terminals is measured to evaluate a noise audible immunity characteristic by a high frequency unbalance / balance conversion. An object of the present invention is to provide a balance characteristic evaluation tester.

[0013]

According to a first aspect of the present invention, there is provided a high-frequency unbalance characteristic evaluation tester for applying a test signal to an EUT in a common mode, wherein the output level of the test signal rises and stops. And an application level setting means for performing a reset to zero, a high frequency detection means for detecting a non-audible high frequency signal having a high frequency common mode high impedance characteristic and the same as an applied frequency generated between receiver terminals of the EUT, and the high frequency detection means. And an applied signal detecting means for measuring an applied signal level when the level of the high frequency signal exceeds a predetermined limit level of the high frequency signal corresponding to the noise audible sound pressure from the receiver.

According to a second aspect of the present invention, there is provided a high-frequency unbalance characteristic evaluation tester for applying a test signal to an EUT in a common mode, wherein the output level of the test signal is raised, stopped, and reset to zero. Means for setting an applied level, and a high frequency common mode high impedance characteristic,
High frequency detecting means for detecting the same inaudible high frequency signal as the applied frequency generated between the receiver terminals of T, applied signal detecting means for measuring the applied signal level of the EUT, and the level of the high frequency signal detected by the high frequency detecting means and the EUT And a characteristic evaluation means for obtaining a ratio with respect to the applied signal level.

[0015]

According to the first aspect of the present invention, the application level setting means applies a continuous sine wave having a constant amplitude to the EUT line in a common mode instead of the AM modulated sine wave. The applied signal detecting means measures the applied signal level when the level of the high frequency signal detected between the receiver terminals exceeds a predetermined limit level of the high frequency signal corresponding to the noise audible sound pressure, and performs acoustic coupling. Enables testing of high-frequency unbalance characteristics without using

According to the second aspect of the present invention, the characteristic evaluation means obtains a high-frequency unbalance characteristic based on a ratio between a level of the high-frequency signal detected between the receiver terminals and a signal level applied to the EUT.

[0017]

FIG. 1 is a block diagram showing a configuration of a high-frequency unbalance characteristic evaluation tester according to one embodiment of the present invention. Here, a case is shown in which noise audible immunity characteristics (hereinafter, these characteristics are called high-frequency unbalance characteristics) by high-frequency balance-unbalance conversion of two EUTs (EUTA, EUTB) 1A and 1B are measured. As shown in the figure, the EU
TA and EUTB are installed via a pseudo switch 61 between them.

A test signal applicator 60 is inserted between EUTA and EUTB. Between the receiver terminals R1 and R2 of both EUTs, high-frequency signal detection means (hereinafter, referred to as high-frequency signal detection means) 4A and 4B between receiver terminals such as a differential probe are in contact. High frequency signal detection means 4
A and 4B detect inaudible high-frequency signals V _Ra and V _Rb with a constant amplitude generated between terminals. The high-frequency signals V _Ra and V _Rb have a V _R waveform as shown in FIG. The high-frequency signal detecting means 4A, 4B is provided between each contact terminal and the frame ground so that the high-frequency common mode signal generated at the receiver terminals R1, R2 does not flow to the frame ground side even if they contact the receiver terminals R1, R2. Have a high impedance.

Each signal detected by the high frequency signal detecting means 4A, 4B is switched and selected by the channel selection switch 5.
Note that the channel selection switch 5 has a switching number n.
Therefore, measurement can be performed for n EUTs.
The output of the channel selection switch 5 and the output of the applied signal detection means 7 are input to a high-frequency signal measuring device 6 such as a high-frequency level meter or a transmission characteristic measuring device having a function of comparing two input channels. The applied signal detecting means 7 is composed of a high impedance probe or the like, and detects the open-end common mode voltage level V ₀ after the line opening switch 63 is opened.

A high frequency applied signal generator (SG) 8 such as a tracking generator having a sweep function generates a test signal. The output level of the test signal is variably set by a programmable attenuator (ATT) 9. The output of the ATT 9 is amplified by the amplifier 10 and applied to the test signal applicator 60.

The channel selection switch 5 and the line release switch 63 are switched by the switch switching unit 11. That is, in the switch switching section 11, the channel selection switch 5 and the line opening switch 63 are operated by driving the magnets M1 and M2. Transfer of measurement data of the high-frequency signal measuring device 6, SG
8, the ATT 9, and the switch switching unit 11 are controlled by the measurement controller 12. The measurement controller 12 has a storage unit 13 that stores measurement data of the high-frequency signal measurement device 6 according to the command, a display unit 14 that displays the measurement data,
And a setting unit 15 for inputting an initial setting signal for the number of steps of frequency and applied level. High frequency signal measuring device 6, SG8, ATT9, switch switching section 11
Are connected to the measurement controller 12 via a GPIB bus.

Therefore, in this embodiment, the application level setting means comprises the SG 8, the ATT 9, and the measurement controller 12. The high frequency detecting means includes a high frequency signal detecting means 4
A, 4B. The applied signal detecting means includes an applied signal detecting means 7 and a high frequency signal measuring device 6. The characteristic evaluation means is constituted by the high-frequency signal measuring device 6 or the measurement controller 12.

FIG. 3 is a graph showing an A _value such as V ₀ shown in FIG.
When an M-modulated sine wave is applied to the EUT, the receiver terminal R1
, R2 between the modulated wave VL and the carrier wave VH. As described in the above-mentioned literature, when the test signal V ₀ of the AM modulated sine wave is converted due to the imbalance of the EUT circuit, the carrier wave V H is generated. It is also known that the carrier wave VH is detected by a semiconductor circuit to generate a modulated wave VL, and this modulated wave VL drives the diaphragm of the handset to become audible noise. The carrier wave VH, which is the source of the modulated wave VL that causes such audible noise, is generated by converting the high frequency applied signal due to the imbalance of the circuit.
Conversion from V ₀ to VH is not related to the presence or absence of modulation. Therefore, if the relationship as shown in FIG. 3 is grasped in advance, a non-modulated high-frequency signal having a constant amplitude is applied as a test signal, and a signal generated between the receiver terminals, that is, a constant-amplitude high-frequency signal having the same frequency as the applied signal is applied. By measuring the signal and comparing the level with the applied signal level, high-frequency unbalance characteristics can be evaluated.

In the configuration shown in FIG.
When an unmodulated (constant amplitude) high frequency sine wave as shown in FIG. 3A is applied to the EUT, the operation procedure for obtaining the high frequency unbalance characteristics of EUTA and EUTB using the relationship shown in FIG. This will be described below.

First, the measurement controller 12 gives an instruction to the switch switching section 11 to set the line opening switch 63 to the short-circuit state, and also sets the channel (for example, CH1) of the high-frequency signal detecting means connected to any EUT. ) Is instructed to connect the channel selection switch 5. When the step-up width of the applied frequency or the applied signal level is set by the setting unit 15, the measurement controller 12 gives an instruction corresponding to the setting to the SG 8. Then, a high-frequency signal having a constant amplitude is output from SG8, and the high-frequency signal is output from ATT9.
To the test signal applicator 60. The test signal applicator 60 uses the high-frequency signal as a test signal as EUTA
Is applied.

In this state, the measurement controller 12 controls the ATT 9
Is instructed to increase the output level at a predetermined step width or continuously. On the other hand, the high-frequency signal detection means 4A detects a high-frequency signal V _Ra (= V _H ) generated between the receiver terminals of EUTA. Then, the detected high-frequency signal is sent to one input channel of the high-frequency signal measuring device 6 via the channel selection switch 5. The high-frequency signal measuring device 6 measures the level of the input signal.

The high-frequency signal measuring device 6 transfers the measurement data (measured level) to the measurement controller 12 when the measured level becomes higher than a predetermined threshold level VH ₀ . Here, VH ₀ is a level corresponding to the audible limit value. That is, a high-frequency signal level VH which is predetermined with respect to VL (i.e. VL ₀₎ corresponding to the limit audible pressure P _0, the relationship is used as shown in FIG. 3, for example. The measurement controller 12 causes the storage unit 13 to store the measurement data.

The measurement controller 12 controls the ATT 9 to
The level of the signal applied to the UTA is held at that value. Also,
The magnet M1 of the switch switching unit 11 is driven to open the line release switch 63.

The applied signal detecting means 7 outputs the common mode applied voltage at this time, that is, the open-end common mode level V
₀ is detected, and the detection level is input to another input channel of the high-frequency signal measuring device 6. The high-frequency signal measuring device 6 sends the detection level to the measurement controller 12. The measurement controller 12 plots the detection level on the frequency axis displayed on the display unit 14. Here, the measurement controller 12
Are plotted as V ₀ by the applied signal detecting means 7 and V _Ra (= V _H ) by the high frequency signal detecting means 4A.
May be adopted. Further, the ratio may be calculated by the high-frequency signal measuring device 6.

Next, the measurement controller 12 controls the ATT 9 to once reduce the level of the signal applied to EUTA to zero. Further, the magnet M1 of the switch switching unit 11 is driven again to restore the line opening switch 63. At the same time, SG8
Is instructed to proceed to the next step in which the applied frequency is determined in advance. Then, the above operation is repeated.

After the above operation has been performed for all predetermined frequencies, the measurement controller 12 drives the magnet M2 of the switch switching section 11 to switch the channel selection switch 5 to CH2. Then, the high-frequency signal V _Rb between the receiver terminals of the EUTB is measured by the same processing as the above processing.

As described above, the threshold level V _RO (= VH ₀ ) in the high-frequency signal measuring instrument 6, the step width or continuously variable width of the applied signal level by the ATT9, and the frequency step width or continuous variable width in SG8. If the above processing is performed after setting the width in advance, the high-frequency unbalance characteristics of a plurality of EUTs are automatically obtained. FIG. 4 shows EUTA, E obtained as described above.
9 shows an example of a high-frequency unbalance characteristic of a UTB. The vertical axis represents the applied signal level V ₀ or the applied signal level V ₀ when the level of the high frequency signal V _Ra or V _Rb (= VH) exceeds a threshold level V _R0 (= VH ₀ ) which is an audible limit value. Conversion attenuation (α _H = 20 log (V ₀ / V H), α _L = 20 log) expressed as a ratio to the signal VH
(V ₀ / VH ^' ), and any of them may be used. In the figure, Vh or α _H0 is an evaluation level value of noise audible immunity (a recommended value by a standardizing organization such as IEC).

In the case of this example, the evaluation level value Vh (or the conversion attenuation amount evaluation value α for noise audible immunity evaluation)
_H0, EUTA satisfying the alpha _H0 ^'), EUT from EUTB is and that the frequency range of EUTB is below f1 and f2 less, respectively, for the same applied signal level V ₀
It can be easily determined that the immunity level of A is small.

That is, the audible noise immunity of the EUT can be easily and quickly evaluated from the obtained high-frequency unbalance characteristics and the evaluation level value Vh. In addition, according to the present invention, an electric signal between the receiver terminals is extracted and evaluated without using the conventional acoustic coupling method, so that an acoustic coupler, a sound insulation box, and the like are not required. Therefore, even when a large number of EUTs are connected to the home bus line as in the configuration shown in FIG. 10, noise audible immunity evaluation and the like can be easily performed. In addition, it is possible to easily evaluate the audible noise immunity of the main device and the opposing communication device due to an increase in the imbalance of the extension circuit generated when the number of connected EUTs is sequentially increased.

It is to be noted that, even when a waveform analyzer such as a spectrum analyzer or a memory scope is used as the high-frequency signal measuring device 6 and V ₀ and V _R are respectively taken as the spectrum level or the waveform level, the same as in the above embodiment is obtained. High frequency unbalance characteristics can be measured.

FIG. 5 is a configuration diagram showing a configuration of a test system in which EUTA is terminated by an equivalent impedance of a transmitter / receiver circuit. Its equivalent impedance is EUTA in FIG.
This corresponds to the transmitter / receiver load system. In FIG. 5 (a), Z _T is transmitter terminals T1, T2 viewed from transmitter equivalent impedance of EUT, Z _R is receiver terminals R1, R2 viewed from handset equivalent impedance, Zhg the handset terminal T
It is the equivalent impedance between 1, T2, R1, R2, and pseudo earth. FIG. 5B shows a configuration in which the EUT is terminated with these equivalent impedances instead of the handset in the handset load system arrangement. Thereby, the arrangement of the EUT can be simplified.

FIG. 6 is a configuration diagram showing a configuration example of the high-frequency signal detection means 4A, 4B using a differential probe. In the figure, reference numeral 21 denotes a contact for contacting the receiver terminals R1 and R2 to capture the signal level between the receiver terminals. Reference numeral 22 denotes a common mode having a large common mode attenuation over a wide band and a small or constant differential mode attenuation. A choke coil, 23 is an attenuating element, 26 is a metal differential probe housing including a differential signal detecting element 24 such as an FET, an amplifier 25 and the like, and 27 is a differential probe housing 2
Reference numeral 6 denotes an outer conductor of the connected coaxial cable.

The contact 21 is an EUT to which a test signal having a high frequency component such as a common mode high frequency sine wave is applied.
By touching the receiver terminals R1 and R2, a signal between the receiver terminals is detected. In that case, assuming that there is no common mode choke 22 or attenuation element 23, the receiver terminals R1,
The high frequency component of the common mode signal generated in R2 flows to the outer conductor 27 of the coaxial cable via the stray capacitance Cg between the differential signal detecting element 24 and the differential probe member 26. Therefore, the signal between receiver terminals fluctuates greatly before and after contact with the differential probe. However, if the common mode choke 22 and the attenuating element 23 are inserted, they prevent high frequency components of the common mode signal. Therefore, according to the configuration shown in FIG. 6, even if the differential probe is brought into contact with the receiver terminals R1 and R2, the signal between the receiver terminals does not change, and proper measurement can be performed.

FIG. 7 is a configuration diagram showing another example of the configuration of the high-frequency signal detection means 4A, 4B. As shown in the figure, a photoelectric conversion probe 34 serving as a high-frequency signal detection unit includes an optical modulator 31, a light source 32 such as a laser, and an OE converter 33 that converts an optical signal into an electric signal.

The photoelectric conversion probe 34 uses two antenna elements of a dipole antenna disclosed in, for example, JP-A-2-275370 as contacts. When detecting an inter-terminal signal from the EUT, the intensity of the optical signal from the light source 31 is modulated by the inter-terminal signal in the optical modulator 31. Then, the OE converter 33 returns the optical signal to an electric signal. In such a probe, only the contact portion is made of metal, and the detected inter-terminal signal is converted into light by the optical modulator 31, so that the receiver terminal R
Even if a common mode high-frequency signal exists in R1 and R2, the signal between terminals does not fluctuate due to probe contact.

[0041]

As described above, according to the present invention, the high-frequency unbalance characteristic tester generates noise sound pressure by the high-frequency signal detecting means which is less affected even when it comes into contact with the receiver terminal. The configuration measures the signal between terminals electrically, eliminating problems such as difficulty in mounting the handset during acoustic coupling due to the shape of the earpiece and instability of the detection level due to improper mounting. When measuring audible immunity of many EUTs at the same time, there is an effect that it is possible to provide a device capable of performing measurement with high reproducibility in a short time.

In place of an actual audible signal such as an AM-modulated sine wave, an unmodulated common-mode high-frequency signal
To detect a non-audible high-frequency signal between the receiver terminals, which is a signal converted into a differential mode by an unbalanced component of the circuit, and evaluate the audible immunity by comparing this with an applied signal. Therefore, there is an advantage that the audible immunity characteristics can be easily evaluated using a commonly used tracking generator or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a high-frequency unbalance characteristic evaluation tester according to one embodiment of the present invention.

FIG. 2 is a waveform diagram showing a test signal and a high-frequency signal between receiver terminals.

FIG. 3 is a characteristic diagram showing an example of a high-frequency component and a low-frequency component generated between receiver terminals.

FIG. 4 is a characteristic diagram illustrating an example of a high-frequency unbalance characteristic.

FIG. 5 is a configuration diagram showing a configuration of a test system in which an EUT is terminated by an equivalent impedance of a handset circuit.

FIG. 6 is a configuration diagram illustrating a configuration example of a high-frequency signal detection unit.

FIG. 7 is a configuration diagram showing another configuration example of the high-frequency signal detection means.

FIG. 8 is a waveform diagram showing an AM modulated sine wave and its unmodulated wave.

FIG. 9 is a configuration diagram showing a configuration of a conventional noise audible immunity test system.

FIG. 10 is a configuration diagram showing a configuration in which one test signal applicator is connected to a system including a plurality of EUTs.

[Explanation of symbols]

 1A, 1B EUT 4A, 4B High frequency signal detecting means 5 Channel selection switch 6 High frequency signal measuring instrument 7 Applied signal detecting means 8 High frequency applied signal generator (SG) 9 Programmable attenuator (ATT) 10 Amplifier 11 Switch switching section 12 Measurement control Unit 13 Storage unit 14 Display unit 15 Setting unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04M 3/22

Claims (2)

(57) [Claims] 1. A high-frequency unbalance characteristic evaluation tester for evaluating a high-frequency unbalance characteristic by applying a test signal containing a high-frequency component from a line of a device under test, wherein the test signal is applied to the device under test in a common mode. An application level setting means for increasing, stopping, and returning to zero the output level of the test signal; and an application frequency having high frequency common mode high impedance characteristics, and an application frequency generated between receiver terminals of the device under test. High-frequency detection means for detecting the same non-audible high-frequency signal; and an applied signal level when the level of the high-frequency signal by the high-frequency detection means exceeds a predetermined limit level corresponding to the noise and audible sound pressure from the receiver. A high frequency unbalance characteristic evaluation tester comprising: an applied signal detecting means for measuring. 2. A high-frequency unbalance characteristic evaluation tester for evaluating a high-frequency unbalance characteristic by applying a test signal containing a high-frequency component from a line of a device under test, wherein the test signal is applied to the device under test in a common mode. An application level setting means for increasing, stopping, and returning to zero the output level of the test signal; and an application frequency having high frequency common mode high impedance characteristics, and an application frequency generated between receiver terminals of the device under test. High-frequency detection means for detecting the same non-audible high-frequency signal; applied signal detection means for measuring the level of an applied signal of the device under test by the applied level setting means; and the level and application of the high-frequency signal detected by the high-frequency detection means A high-frequency unbalance characteristic evaluation tester, comprising: a characteristic evaluation means for obtaining a ratio to a signal level.