JPH03285187A - Measuring device of resistance to disturbance - Google Patents

Abstract

PURPOSE:To improve the operating efficiency and operability of measurement by detecting beforehand only the frequency of generation of a beat disturbance caused by an RF system, by using an unnecessary signal in a state of being interrupted from amplitude modulation. CONSTITUTION:A desired signal (a) from a desired signal oscillator 2 is inputted to a terminal ANT of an apparatus 1 to be tested. Besides, the low frequency component of an amplitude-modulated output signal of an unnecessary signal generating circuit 21 is removed by a high-pass filter 9 and the signal thus processed is inputted as an unnecessary signal (b) to the apparatus 1. Meanwhile, an output signal of a circuit 10a out of pseudo-load circuits 10a and 10b connected to the right and left audio output terminals of the apparatus respectively is inputted to an AF voltmeter 23. An AC output signal of an amplifier 23b is impressed on an oscilloscope 13 and a DC output signal of a detector 23C is impressed on an input terminal of a disturbance wave analyzer 22. The analyzer 22 subjects the execution value of an output signal of the voltmeter 23 to dB display in synchronization with the frequency outputted from the circuit 21. In the analyzer 22, measurement can be executed in the range of 30 to 40 dB without changing over a measuring range of the voltmeter 23.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for measuring interference resistance, which indicates the ability to eliminate externally input interference signals in electronic devices such as broadcast receivers (tuners) and main amplifiers. Concerning a measuring device.

[Prior Art] Generally, interference immunity tests of broadcast receivers and related equipment are carried out based on, for example, the provisions of DIN (Western German Industrial Standard)/VDE 0872 Part 20. According to the same standard, the interference resistance means that the device under test satisfies the specified requirements when a specified level of interference signal is applied to the device under test. It is defined by the S/N ratio of the audio output signal.

Note that the interference signal is a high frequency signal that may interfere with radio broadcast reception or cause malfunction, and the unnecessary signal is an RF (high frequency) signal that simulates this interference signal.

And, the interference resistance includes input interference resistance and interference resistance against conducted voltage, depending on the inflow path of interference waves.

Although it is defined as interference immunity against incoming current and resistance against incident interference, in order to simplify the explanation, the interference immunity against conducted voltage will be explained below using a VHF-band ■ receiver (FM receiver) as an example. do. Note that the interference resistance against conducted voltage is the ability to eliminate unnecessary voltages at the audio input terminal, power supply connection terminal, and audio output terminal. Furthermore, a high frequency signal that simulates an interference signal is called an unnecessary signal.

FIG. 5 is a block diagram showing a schematic configuration of a disturbance resistance measuring device for measuring the interference resistance of the second equipment under test using an FM receiver as the equipment under test. Antenna terminal A of equipment under test
The desired signal a output from the desired signal oscillator 2 is input to the NT via the impedance converter 3. A modulated signal is input to this desired signal oscillator 2 from a stereo modulator 4 .

The desired signal a outputted from the desired signal oscillator 2 is FM modulated No. 12 defined as shown in Table 1.

In addition, a pseudo power supply circuit 5 is connected to the power supply terminal PW of the equipment under test 1.
AC power is supplied from the commercial AC power supply 6 via the AC power source 6. In addition to the commercial AC power supply 6, unnecessary signals are applied to the pseudo power supply circuit 5 from an unnecessary signal generation circuit 7 via an RF amplifier 8 and a bypass filter 9. Therefore, the unnecessary signal is superimposed on the AC power supplied from the pseudo power supply circuit 5 to the equipment under test 1. This unnecessary signal is an AM modulated signal with a modulation frequency of 1 kHz and a modulation depth of 80%, and its carrier frequency is 0.15 to 1.
It is possible to sweep over a wide frequency range of 5(IM)Iz. And the signal level dB (μV) at each frequency
is set as the limit value of inflow disturbance resistance as shown in Table 2.

Note that the linear decrease in the table indicates that the signal level decreases linearly with the logarithm of the frequency from 120 dB to 110 dB.

Furthermore, pseudo load circuits 10a and 10b are connected to the left and right audio output terminals of the device under test 1, respectively. This pseudo load circuit 10a.

For example, if 10b is the equipment under test 1 or an FM receiver, the main amplifier is connected to each output terminal, and the FM receiver built in the amplifier is connected to the main amplifier.
If it is an M receiver, it is assumed that a speaker will be connected, and an 8Ω resistor is generally used. The output signal C of this pseudo load circuit 10a is input to an AF (audio frequency) voltmeter 12 via a band pass filter (BPF) 11. Then, the AF voltmeter 12 measures the voltage level of the output signal C. This AF voltmeter 12 displays the input voltage in dB values. The measuring range is configured to be switchable, for example, in 10 dB increments using a range switch, depending on the signal level of the human input signal.

Furthermore, the sensitivity can be adjusted using the sensitivity adjustment knob. Further, the waveform of the output signal C determined by the AF main voltage t12 is displayed on the oscilloscope 13.

In addition, test equipment 1. Pseudo power supply circuit 5. Pseudo load circuit 1.
0a and 10b are installed on a metal plate 15 to eliminate external influences.

Next, a measurement procedure for measuring the interference resistance of the device under test 1 using the interference resistance measurement apparatus configured as described above will be explained using the flowchart of FIG.

First, in S (step) 1, a desired signal a under the conditions shown in [Table 1] is applied to the device under test 1. In this state, the unnecessary signal generating circuit 7°RF amplifier 8 has not yet been activated. Then, in S2, with only the desired signal a applied, the output level of the desired audio signal output from the audio output terminal of the device under test 1 becomes 50 mW, which is the reference level. Adjust the volume control (volume). For example, the pseudo load circuit 10
If a and 10b are 8Ω, a voltage of 0.63V across both ends is 8Ω.
It's fine as long as it's done.

Next, in S3, with the output set to 50mW,
Set the indicated level of the AF voltmeter 12 to OdB (reference) using the range switch and sensitivity adjustment knob. S4
, the desired signal a applied to the antenna terminal ANT
The desired audio signal is removed by cutting off the stereo modulator 4 and leaving it unmodulated.

In S5, the measurement range of the AF voltmeter 12 is switched from the OdB (reference level) set in S3 to -40 dB (general receiver) or -20 dB (car radio) by operating the range switch. Then, in S6, the unnecessary signal generation circuit 7 and the RF amplifier 8 are activated, and the unnecessary signal is applied to the power supply terminal PW of the device under test 1 via the pseudo power supply circuit 5. Note that the level of the unnecessary signal is measured by a separately provided level meter (not shown). Then, it is held at the limit value shown in εTable 2] and swept over the entire measurement frequency range of 0.15 to 150 M) (z. In S7, the AF voltmeter 1
The indication level of 2 is above -40 over the entire measurement frequency range.
dB (general receiver) or -26dB (car radio)
Make sure that it does not exceed.

The standard for interference is the audio desired signal to interference signal ratio or 40d.
B (26 dB for a car radio), conversely, the AF voltmeter 12 is -40 dB (-26 dB for a car radio).
The signal level of the unnecessary signal is adjusted so as to indicate dB), and the level indicated by the AF voltmeter 12 is recorded over all frequencies. An example of the measurement results is shown in FIG. If the value is below the limit value, interference will occur and the device under test 1 will be rejected.

By the way, when an audio interference signal appears in the equipment under test 1 such as an FM receiver due to the influence of unnecessary signals, there are two types of patterns as shown in FIG.

First, as shown in the waveform of Fig. 7(a), 1k is mainly affected by the amplitude modulation of the audio amplifier system or unnecessary signals.
This is a case where Hz interference appears, and in this case, when the frequency of the unnecessary signal is increased, interference 14a is recognized in a wide frequency range. The other pattern, as shown in the waveform of Fig. 7(b), is when the RF system is affected by unnecessary signals and beat interference appears, and in this case, linear interference 14b occurs in a very narrow frequency range. appears as

For actual measurement, connect the oscilloscope 13 to the AF voltmeter 12, observe the waveform shown in Figure 7(a) or Figure 7(b) appearing on the oscilloscope 3, and plot the frequency on the horizontal axis. Any interference 14a, 1 if indicated
Predict whether it will be 4b.

By the way, when actually measuring according to the flowchart in Figure 6, the signal level of the unnecessary signal is set to a value approximately +10 dB higher than the limit value shown in [Table 2] in S6, and the sweep is started. . Then, frequency sweep is started from 0.15 MHz. That is, the characteristic shown by the dotted line in the lower frequency characteristic of FIG. 7 is the limit value shown in Table 2. The signal level of the unnecessary signal is set to a value 10 dB higher than this limit value, as shown by the solid line.

In addition, increase the signal level of this unnecessary signal by +10 from the limit value.
The reason why the value is set to a value approximately dB higher is to allow measurement with margin relative to the standard.

Then, the frequency of the unnecessary signal is slowly increased, and when the indicated level of the AF voltmeter 12 exceeds -40 dB or -26 dB, it is determined that interference has occurred, and +
The signal level of the unnecessary signal, which has been increased by 10 dB, is
The indicated level of F voltmeter 12 is -40dB or -26d.
Reset it so that it becomes B. Then, the signal level of the unnecessary signal in that state is recorded as the interference occurrence level at the corresponding frequency.

In this way, the signal level of the unnecessary signal is set higher than the limit value, the frequency is increased sequentially, and the signal level of the unnecessary signal is reset each time the instruction level changes.
We will measure the level of interference. When the measurement is completed over the entire frequency range, the measurement results shown in the lower part of FIG. 7 are obtained by taking the frequency as the horizontal axis and the interference generation level as the vertical axis.

[Problems to be Solved by the Invention] However, the following problems still remain to be solved in the interference immunity measuring device in which the operator manually measures the interference level at each frequency using such a measurement procedure. Ta. In other words, the operator observes the waveform shown in FIG. 7(a) or FIG. 7(b) displayed on the oscilloscope 13 and determines whether it is interference or interference caused by the AF system that appears in a wide frequency range. RF that appears in a narrow frequency range
Determine whether it is a system disturbance. If it is determined that the interference is caused by the AF system, the frequency will be set to 20 (] kHz, for example.
The disturbance generation level is measured for each z using the method described above, and the disturbance 14a shown in FIG. 7 is obtained.

On the other hand, if it is determined that the interference is caused by the RF system, the frequency is shifted, for example, by 1 kHz in the vicinity of that frequency, that is, the frequency of the unnecessary signal is finely adjusted, and the frequency of the interference 14b shown in FIG. It is necessary to measure the worst value of the disturbance occurrence level.

The interference 14b caused by this RF system has a frequency width of several tens of kilometres.
) It appears below Iz, and searching for that frequency requires a skilled operator's signal judgment and intuition to search for the frequency. Furthermore, even for an expert, it takes a long time to measure the interference generation level over the entire measurement frequency range.

Furthermore, it is conceivable to automatically measure the interference generation level by automatically sweeping the frequencies of the interference 14a caused by the AF system and the interference 14b caused by the RF system, but Since it is difficult to automatically distinguish between interference and interference caused by the RF system, in order to reliably measure interference 14b caused by the RF system, it is necessary to
Within a wide measurement range of 0 MHz, the signal level of the unnecessary signal must be reset every several kHz, which is the frequency width in which the worst value of the interference 14b can be detected. Therefore, the processing time becomes enormous and is not practical.

The present invention was made in view of these circumstances, and
RF using unnecessary signals with amplitude modulation turned off in advance.
By detecting the frequency of occurrence of beat disturbance caused by the system, it is possible to detect the interference occurrence level for each narrow frequency width at that specific frequency and for each relatively wide frequency other than that frequency. It is an object of the present invention to provide a disturbance resistance measuring device that can shorten processing time, enable automatic measurement, and greatly improve measurement work efficiency and operability.

[Means for Solving the Problems] In order to eliminate the above-mentioned problems, the present invention applies a high frequency signal amplitude-modulated with an audio frequency (AF) signal to one input/output terminal of the equipment under test as an unnecessary signal. Then, while sweeping the carrier frequency of the unwanted signal within a predetermined frequency range, the signal of the unwanted signal is detected when the level of the audio interference signal that appears at the audio output terminal of the equipment under test due to the unwanted signal reaches a predetermined interference standard. In a disturbance immunity measuring device that measures the level, the A of the equipment under test is mainly an audio amplifier system or
In response to interference caused by the amplitude modulation component of the F-fold signal,
A high-speed interference resistance measuring means that sweeps a predetermined frequency range at high speed and measures the frequency and level of an unnecessary signal when the audio interference signal level is the interference reference value S, and a state in which amplitude modulation in the unnecessary signal is removed. a 1,000-fi measuring means for applying a carrier frequency while sweeping it in a predetermined frequency range and detecting the frequency at which beat disturbance occurs due to the carrier wave component; Signal level measuring means for measuring the level of the unwanted signal when the audio interference signal level reaches the interference reference value by applying the carrier frequency while sweeping it in a very narrow range while restoring the amplitude modulation of the unwanted signal in the vicinity. It is equipped with the following.

[Function] As mentioned above, in general, an unnecessary signal amplitude-modulated by the AF multiplied signal is applied to one terminal of the equipment under test, and the audio interference signal appearing at the audio output terminal of the equipment under test is transmitted to the audio amplifier system. There are two types of interference: beat interference, which occurs in a relatively wide frequency range caused by the RF system of the equipment under test, and beat interference, which occurs in a very narrow frequency range caused by the RF system of the equipment under test. Therefore, when measuring the interference generation level at each frequency for these two types of interference, it is necessary to set the measurement frequency interval to correspond to the RF system interference that occurs in a very narrow frequency range.

Therefore, if the amplitude modulation of the unnecessary signal is blocked, as described above, audio interference having a wide frequency range caused by the audio system will not occur. Therefore, in preliminary measurements,
If only the frequency at which beat disturbance caused by the RF system occurs is detected, amplitude modulation is restored only for each frequency in the very narrow vicinity of the detected frequency, and the regular disturbance generation level is measured. The frequency and level of interference caused by the RF system can be efficiently measured.

Further, since interference caused by the audio amplifier system occurs in a wide frequency range, the measurement frequency interval can be set to a certain extent wide without taking into account the beat interference caused by the R system, and high-speed sweeping can be performed.

Therefore, by performing separate measurements depending on the type of disturbance generating factor, the overall measurement efficiency can be improved.

[Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a disturbance resistance measuring device according to an embodiment. The same parts as in FIG. 5 are given the same reference numerals.

The FM-modulated desired signal a specified in Table 1 above, which is output from the desired signal oscillator 2, is inputted to the antenna terminal ANT of the device under test 1 via the impedance converter 3. Further, the amplitude-modulated output signal of the unnecessary signal generation circuit 21 formed by the tracking oscillator is amplified by the RF amplifier 8, and after the low frequency components of 100kHz or less are removed by the bypass filter 9, the output signal is as specified in [Table 2]. The resulting unnecessary signals are input to the device under test 1 via the pseudo power supply circuit 5. The frequency of the unnecessary signal a output from the unnecessary signal generation circuit 21 is the same as the horizontal axis (frequency axis) of the interference wave analyzer 22.

On the other hand, an output signal from one of the pseudo load circuits 10a and 10b connected to the left and right audio output terminals of the device under test 1 is input to the AF voltmeter 23 via the BPFll. As shown in the figure, this AF voltmeter 23 mainly includes a range switcher 23a that switches the measurement range, for example, every 10 dB, an amplifier 23b, and a detector 23.
The AC output signal of the amplifier 23b is applied to the oscilloscope 13, and the DC output signal of the detector 23 is applied to the vertical axis (level axis) input terminal of the interference wave analyzer 22. is applied to.

The display 23d of the AF voltmeter 23 displays dB in the same way as the AF voltmeter 12 shown in FIG.

The measurement range is switched in 10 dB increments using the range switch 23a.

The interference wave analyzer 22 has a logarithmic conversion circuit incorporated therein, and converts the actual value of the output signal of the AF voltmeter 23 into d in synchronization with the frequency output from the unnecessary signal generation circuit 21.
BDisplay. As shown in FIG. 2, the display screen 22a is marked with a scale from OdB to -50 dB. Then, the cane adjustment is performed so that the display level indicates -10 dB when the DC output voltage of the AF voltmeter 23 is approximately IV (reference voltage). In such an interference wave analyzer 22, on the display screen 22a shown in FIG.
A range of 40 dB can be measured without changing the measurement range of the AF voltmeter 23.

In addition, an unnecessary signal generation circuit 21 and an interference wave analyzer 2
The operation No. 2 is controlled by a control unit 24 configured with, for example, a personal computer.

This control section 24 controls the unnecessary signal generation circuit 21 and
Table 1] Sweep frequency of the unnecessary signal input to the equipment under test 1, frequency for detecting the signal level of the output signal from the AF voltmeter 23 to the interference wave analyzer 22, and unnecessary signal frequency
Automatically sets the signal level indicated by the amount of change from the limit value.

In this embodiment, there are two types of measurement conditions: one in which the unnecessary signal is measured with the amplitude modulated according to the standard, and the other in which the unnecessary signal is measured with the amplitude modulation cut off.

Under the measurement conditions where the amplitude is modulated according to the standard, the unnecessary signal level is 0,15~150.
As shown in FIG. 4, the MHz frequency range is divided into five sweeps. Therefore, the frequency range (frequency span) of one sweep is 30 MHz.

Therefore, as shown in FIG. 3, the frequency range of one sweep is displayed on the display screen 22a of the interference wave analyzer 22 on the horizontal axis. In addition, the signal level of the unnecessary signal is 5 dB from the above-mentioned limit value +10 dB to the limit value -30 dB.
It can be set in nine stages for each B.

Then, the sweep speed is set to 0 in the frequency range of 30 to IHz.
．． The speed is set to sweep at 15 seconds. Further, the average processing time required for signal level comparison at each frequency in one sweep is about 0.5S.

Next, under measurement conditions in which the amplitude modulation of unnecessary signals is cut off, the frequency range (frequency span) of one sweep is
Set to 2. Further, the sweep speed is changed to a speed at which the IS sweeps a frequency range of 10 MHz. Therefore, 0.1
5-150M) 12 measurement frequency ranges are swept in 15s. In addition, the signal level of unnecessary signals is the limit value + 10 dB.
Fixed to one type.

Next, a procedure for measuring the interference resistance of the device under test 1 using the interference resistance measuring device configured as described above will be explained.

(1) First, the control unit 24 controls the unnecessary signal generation circuit 2.
The desired signal oscillator 2 is started while the operation of the oscillator 1 is stopped and the application of unnecessary signals to the equipment under test 1 is cut off.

Then, the steps Sl and S shown in FIG. 6 in the conventional device are performed.
2. Perform the g fil A adjustment of the test equipment as in S3, and set the indicated level of the AF voltmeter 23 at that point to Od.
Set to B. In this state, the display level (approximately 1.V) of the display screen 22a of the interference wave analyzer 22 is set to the second level.
As shown in the figure, it is set to -1.0dB.

(2) Next, cut off the output signal of the stereo modulator 4,
FM modulation of the desired signal a input to the equipment under test 1 is cut off. Then, in this state, operate the range switch 23a to change the measurement range of the AF voltmeter 23 from OdB to -20d.
Change to B. Therefore, if the display level of the interference wave analyzer 22 set in step (1) is expressed as the -10 dB point (approximately IV) or the S/N with respect to the desired audio signal level, the S/N- It becomes 20dB.

Similarly, it is displayed that Peru 30dB (about 0.IV) is S
/N=40dB.

(3) Then, the control unit 24 activates the unnecessary signal generation circuit 21 to output an amplitude-modulated unnecessary signal, and the signal level of this unnecessary signal is increased by 10 to the limit value shown in [Table 2].
Set to the value obtained by adding dB.

(4) Then, the unnecessary signal generation circuit 21 is controlled to start the sweep under the measurement condition of measuring with the amplitude modulated in accordance with the above-mentioned standard. Then, if there is interference in the equipment under test 1, the audio interference signal level waveform 25 shown in FIG.
will be displayed. Then, if the signal level of the unnecessary signal is set to the limit value + 10 dB, this audio interference signal level wave R is 25 or - 40 dB (0, I
V) Frequency and disturbance generation level at points that cross the level (
+10dB) is stored. In this way, the audio interference signal level waveform is 25 to 40 dB (0, I V)
L.

When a point crossing the heel is detected, the signal level of the unnecessary signal is lowered by 5 clB and the same frequency range is swept again. If the signal level of the unnecessary signal is lowered, the overall level of the audio interference signal level waveform 25 will move downward, so that this waveform 25 will be -40 dB (0, I V)
The frequency of points that cross the level also moves. Then, the frequency and interference generation level (-5 dB) at this point are stored.

In this way, the audio interference signal level waveform 25 is
The signal level of the unnecessary signal is gradually lowered until it falls below the 0 dB (0, IV) level. Audio interference signal level waveform 25 is -40 dB (0,1 yen) L.

When the frequency falls below the specified frequency range, the measurement for the corresponding frequency range is terminated, and
Move the sweep position to the next frequency range.

(5) When the measurement in each frequency range divided into five sections is completed in this way, the control section 24 prints out the measurement results using a printer or the like as shown in FIG. 4, with the frequency as the horizontal axis. This completes the measurement with the amplitude modulated according to the standard.

(6) Next, the disturbance generation circuit 21 is controlled to start sweeping under the measurement condition of measuring with amplitude modulation of the unnecessary signal interrupted. In this case, since the amplitude modulation of the unnecessary signal is blocked, the interference caused by the audio amplifier system shown in Figure 7(a) will not occur, so the audio interference signal appearing at the output terminal of the equipment under test 1 will be the same. Only the beat disturbance caused by the RF system shown in FIG. 2(b) occurs. Therefore, this interference is only the interference 14b in an extremely narrow frequency width. Therefore,
In this measurement, only the frequency values where interference occurs are detected.

Therefore, the signal level of the unnecessary signal is set to the above-mentioned limit value +
Set it to 10 dB and start the sweep.

If there is interference, the frequency at which the audio interference signal level crosses the 140 dB (0, IV) level is detected and stored. In this way, a total of 15 sweeps are performed while moving through the frequency range. In this case, one frequency range is swept only once, so o
, it takes only about 15 seconds of measurement time to sweep the frequency range of 15-150 MHz.

(7) Next, the signal level of the unnecessary signal is sequentially measured with the amplitude modulated according to the standard only for frequencies within ±100 kHz around each frequency obtained by measurement with amplitude modulation cut off. Measure by lowering.

In addition, the measurement frequency interval in case 2 is 0.0 of the frequency span.
2? The frequency is 0.4kHz.

(8) In this way, once the frequency and interference generation level of the disturbance caused by the beat disturbance of the RF system are determined, the measurement result of the RF system obtained this time is added to the measurement result shown in Figure 4 printed out in (5). join. Therefore, the interference generation level of interference appearing in a relatively wide frequency range caused by the AF system and the RF
The disturbance generation level of disturbances occurring in a very narrow frequency caused by the system can be obtained. .

With the interference resistance measurement device configured as in 2, by applying the unnecessary signal to the equipment under test 1, it is possible to separately distinguish between the interference caused by the audio amplifier system and the beat interference caused by the RF system. It is measured. In response to interference caused by the audio amplifier system that appears in a relatively wide frequency range, the system sweeps the relatively wide frequency range at high speed and brings the audio interference signal to the interference reference level (-40d).
It is determined whether or not B,> is exceeded. Therefore, beat disturbances in the RF system may be missed and the measurement speed can be increased.

On the other hand, when measuring beat interference in an RF system, it is necessary to remove the interference caused by the AF system, which has a relatively wide frequency range, by blocking the amplitude modulation of unnecessary signals. Detects only the frequency at which the disturbance occurs. Then, a very narrow frequency width is measured under regular measurement conditions in which amplitude modulation is applied only to the vicinity of the detected frequency. In the second case, even if the measurement frequency interval is set narrowly, the time required for measurement will not increase because the number of measurement points is small.

For example, when interference as shown in Figure 4 occurs, the signal level of the unnecessary signal is changed in each of the five frequency ranges, and the sweep is performed an average of six times. If the processing time is about 0.55 as described above, the time required for measurement under normal conditions is about 15 seconds. Furthermore, as mentioned above, it takes 15 seconds to detect the occurrence frequency of beat disturbance caused by the RF system, and the disturbance occurrence level of the beat disturbance caused by the RF system existing in the vicinity of each detected frequency is determined under normal conditions. Even if the same 15 seconds were required to measure, the total net measurement time would be less than 1 minute.

Therefore, the overall measurement time can be significantly shortened.

In addition, since interference caused by the audio amplifier system and beat interference caused by the RF system can be automatically determined without relying on the operator's visual inspection, It becomes possible to automatically measure the interference resistance against.

Therefore, even if you are not an expert operator in this measurement,
Measurements can be performed reliably with simple operations.

Note that the present invention is not limited to the embodiments described above. In the embodiment device, the unnecessary signal power supply terminal PW
Although we have described the case where interference resistance is measured when an unnecessary signal is input from the device under test, it is also possible to measure interference resistance when it is applied to the output terminal of the device under test or to the antenna terminal.

[Effects of the Invention] As explained above, according to the interference resistance measuring device of the present invention, only the frequency at which the interference occurs can be detected in advance by using unnecessary signals with amplitude modulation cut off for beat interference caused by the RF system. By doing so, it is possible to detect the interference generation level for each relatively wide frequency other than the specific frequency, which shortens measurement and processing time, making automatic measurement possible and increasing measurement work efficiency and Operability can be greatly improved.

[Brief explanation of drawings]

1 to 4 show an interference immunity measuring device according to an embodiment of the present invention, FIG. 1 is a block diagram showing a schematic configuration, and FIGS. 2 and 3 are displays of an interference wave analyzer. 4 is a diagram showing the measurement results, FIG. 5 is a block diagram showing the schematic configuration of the conventional interference immunity measuring device, FIG. 6 is a flowchart showing the operation of the conventional device, and FIG. 7 is a diagram showing the measurement results. The figure is a diagram showing the measurement results with the same measuring device. 1...Equipment under test, 2...Desired signal oscillator, 4...
Stereo modulator, 5... pseudo power supply circuit, 8... RF
Amplifier, 10a, 10b...pseudo [load circuit, 13...
・Oscilloscope, 21...Unnecessary signal generation circuit, 22
...Interference wave analyzer, 22a...Display screen, 23
...AF voltmeter, 24...Control unit, 25...Audio interference signal level waveform. 2nd vi! J 2a ζ

Claims (1)

[Claims] A high frequency signal whose amplitude is modulated by an audio frequency (AF) signal is applied as an unnecessary signal to one input/output terminal of the equipment under test, and the carrier frequency of the unnecessary signal is swept within a predetermined frequency range. However, in the interference immunity measuring device that measures the signal level of the unnecessary signal when the level of the audio interference signal appearing at the audio output terminal of the equipment under test due to the unnecessary signal reaches a predetermined interference standard, The audio amplifier system of the test equipment sweeps a predetermined frequency range at high speed in response to the interference caused by the amplitude modulation component of the AF signal of the unnecessary signal, and the unnecessary signal is detected when the audio interference signal level reaches the interference reference value. a high-speed interference resistance measuring means for measuring the frequency and level of a signal; a preliminary measurement means for detecting the occurrence frequency of beat interference that appears in the above-mentioned preliminary measurement means; A disturbance resistance measuring device comprising: signal level measuring means for measuring the level of the unnecessary signal when the audio disturbance signal level reaches the disturbance reference value by applying the signal while sweeping it.