JP2003075493A - Measuring apparatus and signal analysis apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the level at a cable end to a desired level accurately by a simple measuring apparatus. SOLUTION: A signal generator 20 generates a signal at a level that is specified by an output level specification means 60 in a signal analysis apparatus 40 for outputting to a signal output terminal 22. A level difference detection means 61 in the signal analysis apparatus 40 detects the difference between the level in power that is measured by a power measurement circuit 52 and a level that is specified by the level specification means 60. A correction circuit 63, a correction value detection means 64, and a correction value memory 65 control the level of the output signal in a signal generator 20 so that the level difference that is detected by a level difference detection means 61 becomes nearly zero, and output a signal at a level that is specified by the level specification means 60 from the end section of a cable that is connected to the side of a signal input terminal 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for increasing the level accuracy of an output signal of a signal generator.

[0002]

2. Description of the Related Art A signal generator is used when measuring various instruments. FIG. 13 shows a general configuration of a conventional signal generator 10 used for measurement.

This signal generator 10 generates a signal S1 of a predetermined level at a predetermined frequency by a reference signal generation circuit 11 and inputs the signal S1 to a modulation circuit 12, which then modulates the signal S1.
Modulate with.

Then, the modulated signal S2 is input to the amplifier 13, the output signal S3 of the amplifier 13 is input to the frequency conversion circuit 14, and the local oscillation signal Sa is used to convert it to the signal S4 of the desired frequency. The frequency-converted signal S4 is converted into a signal S5 of a desired level by the attenuator 15 and the signal output terminal 10a and this signal output terminal 10a are converted.
It is supplied to the measuring object 1 via the cable 2 connected to the.

The signal generator 10 having such a configuration is provided as an accessory of another measuring device (for example, a signal analyzing device) in addition to the one that operates alone, and the local oscillator signal is supplied from the measuring device side. There is a simple type that operates by receiving a signal such as Sa supplied and designating the attenuation amount of the attenuator 15.

In the signal generator 10 having the above structure, the frequency of the signal S5 output from the signal output terminal 10a can be varied by varying the frequency of the local oscillation signal Sa, but the frequency variable range is widened. Then, due to variations in the frequency conversion characteristics of the frequency conversion circuit 14, the level of the signal S5 output from the signal output terminal 10a changes depending on the frequency.

In order to prevent the change of the level of the output signal with respect to this frequency, in the conventional signal generator 10, the gain is controllable in the amplifier 13 as shown in FIG. The level detection circuit 16 detects the detected voltage V corresponding to the level, and the detected voltage V and the voltage V corresponding to the reference level.
The difference with r is obtained by the error detection circuit 17, and the error voltage Ve
The gain of the amplifier 13 is variably controlled in accordance with the above, so that the level of the signal output from the frequency conversion circuit 14 is stabilized.

[0008]

However, even if the level of the output signal of the frequency conversion circuit 14 is stabilized as described above, it is impossible to eliminate the influence of the attenuation amount error of the attenuator 15 and the frequency characteristic, and If the frequency becomes higher, the loss of the cable 2 connecting the signal output terminal 10a and the measurement target 1 cannot be ignored.

Therefore, the level of the signal actually input to the measuring object 1 has a large error with respect to the level determined by the set value of the attenuator 15.

Particularly, in the above-mentioned simplified signal generator,
It is not possible to use an expensive attenuator that has a uniform amount of attenuation over a wide frequency range, the level error described above becomes large, and it is not possible to perform measurement that requires strict accuracy as the input signal level.

The present invention solves this problem and provides a measuring device and a signal analyzing device which can set the level at the cable end to a desired level with high accuracy even if it is a simple type. Is intended.

[0012]

In order to achieve the above object, the measuring apparatus of the present invention generates a signal of a specified level and a signal output terminal (22) for outputting a signal to an object to be measured. Output to the signal output terminal (3)
0 to 37), a signal input terminal (42) for inputting a signal to be measured, power measuring means (52) for measuring the power of the signal input from the signal input terminal, and the signal generator. Output level designating means (60) for designating the level of a signal to be output to the signal output terminal and the power measured by the power measuring means when the signal output terminal and the signal input terminal are connected by a cable. A level difference detecting means (61) for detecting a difference between a level and a level designated by the level designating means, and a level difference detecting means (61) for making the level difference detected by the level difference detecting means almost zero. The level of the output signal is controlled so that the level of the signal output from the end of the cable connected to the signal input terminal side is specified by the level specifying means. Level correcting means to match the Le (63
~ 65).

A signal analysis apparatus of another invention is a housing (41), a signal input terminal (42) provided on the outer surface of the housing for inputting a signal to be measured, and the signal. A power measuring means (51) for measuring the power of a signal input from an input terminal, and a level for designating an external signal generator (20) a level of a signal output from the signal output terminal of the signal generator. When the designating means (60) and the signal input terminal and the signal output terminal of the signal generator are connected by a cable, the level of power measured by the power measuring means and the level designating means are designated. Level difference detecting means (6
1) and controlling the level of the output signal of the signal generating section so that the level difference detected by the level difference detecting means becomes substantially zero, and the end of the cable connected to the signal input terminal side. Level correction means (63 to 65) for adjusting the level of the signal output from the unit to the level designated by the level designation means.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a measuring apparatus to which the present invention is applied, and FIG. 2 shows its appearance.

This measuring device is composed of a signal generator 20 and a signal analyzing device 40 each having an independent casing.

The signal generator 20 is a simple type used as a unit attached to the signal analysis device 40.
As shown in FIG. 2, a signal output terminal 22 is provided on the outer surface of the housing 21.

Although not shown in FIG. 2, a local signal input terminal 25, a level designation signal input terminal 26, and a reference voltage signal input terminal are provided on the outer surface portion (for example, the rear surface) of the housing 21 of the signal generator 20. 27 are provided.

Inside the housing 21 of the signal generator 20, as shown in FIG. 1, a reference signal generation circuit 30, a modulation signal generation circuit 31, a modulation circuit 32, an amplifier 33, a frequency conversion circuit 34, and an attenuator. 35, a level detection circuit 36,
An error detection circuit 37 is provided.

The reference signal generation circuit 30 generates a signal S1 of a predetermined level at a predetermined frequency (for example, 60 MHz) and inputs it to the modulation circuit 32, and the modulation signal generation circuit 31 outputs a predetermined modulation signal M (quadrature modulation signals I and Q). In some cases) is input to the modulation circuit 32.

The modulation circuit 32 modulates the signal S1 with the modulation signal M and inputs the modulated signal S2 to the amplifier 33.

The amplifier 33 amplifies the input signal S2 with a gain corresponding to the error signal Ve output from the error detection circuit 37, and the amplified signal S3 is amplified by the frequency conversion circuit 34.
To enter. An attenuator is used instead of the amplifier 33 to attenuate the input signal S2 by an attenuation amount according to the error signal Ve output from the error detection circuit 37, and attenuate the signal S3 to generate the frequency conversion circuit 34. May be input to.

The frequency conversion circuit 34 converts the signal S3 into a desired frequency by the local oscillation signal Sa input from the local oscillation signal input terminal 25, and inputs the frequency-converted signal S4 to the attenuator 35 and the level detection circuit 36. To do.

For example, as shown in FIG. 3, the frequency conversion circuit 34 mixes the signal S3 and the local oscillator signal Sb of a fixed frequency (for example, several GHz band) output from the local oscillator circuit 34a by the first mixer 34b. Then, the sum (or difference) mixed component is extracted by the bandpass filter 34c, and the extracted mixed component and the local oscillator signal Sa input from the local oscillator signal input terminal 25 are mixed by the second mixer 34d. , The mixed component of the difference is extracted by the low-pass filter 34e and output, and the frequency of the local oscillator signal Sa is set to the local oscillator signal Sb.
By varying several GHz from the vicinity of, the frequency of the output signal S4 can be varied over a wide range of several tens MHz to several GHz.

The attenuator 35 can change the amount of attenuation in steps of 1 dB, for example, and the level of the input signal S4 is a reference level Lr (for example, 10 dB).
m), the signal S4 is reduced by an attenuation amount corresponding to the difference between the level Ls designated by the level designation signal input from the level designation signal input terminal 26 and the reference level Lr.
Is attenuated, and the attenuated signal S5 is output from the signal output terminal 22.

The level detection circuit 36 detects the signal S4 and outputs the voltage V corresponding to the level of the signal S4 to the error detection circuit 37.

The error detection circuit 37 obtains the difference between the reference voltage Vrh input from the reference voltage signal input terminal 27 and the output voltage V of the level detection circuit 36 as an error signal Ve, and supplies this error signal Ve to the amplifier 33. The gain is variably controlled to stabilize the level of the signal S4 output from the frequency conversion circuit 34 to the reference level Lr.

On the other hand, as shown in FIG. 2, a signal input terminal 42 for inputting a signal to be analyzed, an operation section 43, and a display 44 are provided on the outer surface of the housing 41 of the signal analysis device 40. It is provided. Although not shown in FIG. 2, a local signal output terminal 45, a level designation signal output terminal 46, and a reference voltage signal output terminal 47 are provided on the outer surface (for example, the back surface) of the housing 41.

As shown in FIG. 1, the signal analyzer 40 receives the operation of the operation unit 43 and the like, and sets the operation mode of the signal analyzer 40 to the wideband power measurement mode, spectrum measurement mode, and signal measurement mode. A mode designating means 50 for designating one of the generator level calibration modes is provided.

Here, the signal generator level calibration mode is
The signal input terminal 42 and the signal output terminal 22 of the signal generator 20
A mode for adjusting the level of the signal at the cable end to the level specified by the level specifying means 60 described later by connecting the cable between the cable and the cable and measuring the power of the signal output from the signal generator 20. Is.

The signal input terminal 4 of the signal analyzer 40
A signal changeover switch 51 is connected to 2.

When the wide band power measuring mode or the signal generator level calibration mode is designated by the mode designating means 50, the signal changeover switch 51 outputs the signal Sx inputted from the signal input terminal 42 to the power measuring circuit 52, When the reception demodulation mode or the spectrum measurement mode is designated, the signal Sx input from the signal input terminal 42 is output to the frequency conversion circuit 53.

The power measuring circuit 52, as shown in FIG.
A wide band power sensor 52a (for example, a thermocouple) that converts the power of the signal Sx input via the signal changeover switch 51 into heat and outputs a signal according to the amount of heat generated, and the output of the power sensor 52a at the power level. It is composed of a conversion means 52b for converting and outputting to Lx.

Further, the frequency conversion circuit 53 has a predetermined intermediate frequency component of the signal Sx input through the signal changeover switch 51, which is determined by the frequency of the local oscillation signal Sa output from the local oscillation signal generation circuit 54. Frequency band signal S
Convert to x '.

This frequency conversion circuit 53 is used for the signal generator 2
The reverse processing of the frequency conversion circuit 34 of 0 is performed,
As shown in FIG. 5, the signal Sx and the local oscillation signal Sa are mixed by the first mixer 53a, a component of several GHz band is extracted from the mixed component by the first bandpass filter 53b, and the extracted signal is extracted. And a fixed frequency (for example, several GHz) local oscillation signal Sc output from the local oscillation circuit 53c
The mixer 53d is configured to mix, and a component of the intermediate frequency band of several tens of MHz of the mixed component of the difference is extracted by the second bandpass filter 53e.

The local oscillator signal generation circuit 54 generates a local oscillator signal Sa whose frequency is controlled by the frequency control means 55 and outputs it to the frequency conversion circuit 53 and the local oscillator signal output terminal 45.

The frequency control means 55 is a mode designating means 5
When the reception demodulation mode is designated by 0, the local oscillation signal generation circuit 54 is controlled so that the frequency of the local oscillation signal Sa becomes the frequency corresponding to the reception frequency designated by the operation unit 43 or the like, and the spectrum measurement mode is set. When designated, the local oscillator signal generation circuit 54 is controlled so that the frequency of the local oscillator signal Sa sweeps in a predetermined step in a frequency range corresponding to the reception frequency range designated by the operation unit 43 or the like.

When the signal generator level calibration mode is designated, the local oscillator signal generation circuit 54 is controlled so as to sweep the frequency range of the local oscillator signal Sa corresponding to the entire reception frequency range in a predetermined step. Along with the frequency information, a correction circuit 63 and a correction value memory 6 described later
Output to 5.

The signal S output from the frequency conversion circuit 53
x ′ is input to the logarithmic amplifier 56 and the demodulation circuit 57.

The logarithmic amplifier 56 logarithmically amplifies the signal Sx 'output from the frequency conversion circuit 53 when the spectrum measuring mode is specified by the mode specifying means 50, and is proportional to the logarithm of the level of the signal Sx'. Output the voltage.

The demodulation circuit 57 has a mode designating means 5
When the reception demodulation mode is designated by 0, the signal Sx ′ output from the frequency conversion circuit 53 is demodulated and a demodulated signal is output.

The display control means 58 is a mode designating means 50.
When the wide band power measurement mode is designated, the output of the power measurement circuit 52 is displayed on the display 44, and when the spectrum measurement mode is designated, the output voltage of the logarithmic amplifier 56 is plotted on the vertical axis (Y axis) and the frequency. Control means 55
The display 44 displays a spectrum waveform having the horizontal axis (X axis) of the reception frequency controlled by the sweep, and when the reception demodulation mode is designated, the signal demodulated by the demodulation circuit 57 is displayed on the display 44. .

The level designating means 60 outputs to the level designating signal output terminal 46 a level designating signal Ls designating the level input by the operation of the operating section 43.

The level difference detecting means 61 has a signal input terminal 4
2 and the signal output terminal 22 of the signal generator 20 are connected by a cable, and the power measured by the power measurement circuit 52 when the signal generator level calibration mode is designated by the mode designation means 50. The difference ΔL between the level Lx and the level Ls designated by the level designating means 60 in the signal generator 20 is obtained.

The reference voltage generating circuit 62 generates a reference voltage Vr equal to the voltage obtained by detecting the signal of the reference level Lr.

The correction circuit 63 constitutes the level correction means of this embodiment together with a correction value detection means 64 and a correction value memory 65 which will be described later, and outputs from the reference voltage generation circuit 62 in the signal generator level calibration mode. The reference voltage Vr is output to the reference voltage output terminal 47, and in a mode other than the signal generator calibration mode, after the correction value ΔV stored in the correction value memory 65 described later, the frequency information from the frequency control means 55 ( The correction value ΔV (fi) corresponding to fi) is read out, and the correction value ΔV (f
The reference voltage V output from the reference voltage generation circuit 62 in i)
r is added and corrected, and the corrected reference voltage Vrh is output to the reference voltage output terminal 47.

The correction value detecting means 64 obtains the correction value ΔV of the voltage corresponding to the level difference ΔL detected by the level difference detecting means 61 in the signal generator level calibration mode for each frequency and stores it in the correction value memory 65. .

The detection of the correction value ΔV is based on the relationship between the change of the reference voltage Vrh and the change of the level of the output signal of the signal generator 20, and the level difference ΔL is substantially zero (zero or centered at zero). A method of calculating the voltage required to be within the allowable range) and obtaining the difference between the voltage and the reference voltage Vr, and the reference voltage until the level difference ΔL actually detected by the level difference detecting means 61 becomes substantially zero. Vrh to V
There is a method of changing from r and using the voltage changed at that time as a correction value.

In the latter case, the correction value detecting means 64 outputs the adjustment voltage ΔV ′ to the correction circuit 63, and the correction circuit 63
Is configured to add the adjustment voltage ΔV ′ and the reference voltage Vr and output to the reference voltage output terminal 47, and the adjustment voltage when the level difference ΔL detected by the level difference detection means 61 becomes substantially zero. Let ΔV ′ be the correction value at that frequency.

The signal analysis device 40 configured in this way
Then, for example, when the signal Sx to be measured is input to the signal input terminal 42 in a state where the mode designating unit 50 designates the wide band power measurement mode in response to the operation on the operation unit 43, the power measurement circuit 52 outputs the signal. The power of Sx is measured, and the measurement result is displayed on the display unit 44.

Further, when the signal Sx to be measured is input to the signal input terminal 42 in the state where the mode designating unit 50 designates the spectrum measurement mode, the frequency conversion is performed in response to the frequency-swept local oscillation signal Sa. Each frequency component of the signal Sx is converted into an intermediate frequency band by the circuit 53, logarithmically amplified by the logarithmic amplifier 56, the power of each frequency component is detected, and the spectrum is displayed on the display 44.

Further, as shown in FIG.
The signal input terminal 42 of 0 and the signal output terminal 22 of the signal generator 20 are connected by the cable 2, and the local signal output terminal 4
5 and the local oscillator signal input terminal 25, between the level designation signal output terminal 46 and the level designation signal input terminal 26, and between the reference voltage output terminal 47 and the reference voltage input terminal 27.
When the signal generator level calibration mode is designated by the mode designating means 50 with the cables 3 to 5 respectively connected, the output signal frequency of the signal generator 20 and the reception frequency of the signal analyzer 40 are set to the sweep start frequency fa. ,
A difference ΔL between the level Lx of the power measured by the power measuring circuit 52 and the level Ls designated by the level designating means 60 at that frequency is detected, and a correction value ΔV (fa) for making the level difference ΔL zero. ) Is detected and stored in the correction value memory 65.

This processing is performed every time the reception frequency changes, and when the processing for the sweep end frequency fb ends,
The correction value memory 65 includes, for example, the signal generator 2 shown in FIG.
The correction value ΔV for eliminating the level error ΔL with respect to the frequency change of the output signal of 0 is stored for each frequency as shown in FIG.

Then, after the correction value ΔV for each frequency is obtained by this signal generator level calibration mode, the operation mode of the signal analyzer 40 is switched to a mode other than the signal generator level calibration mode, and as shown in FIG. As described above, by disconnecting the tip of the cable 2 from the signal input terminal 42 of the signal analyzer 40 and connecting it to the measurement target 1, it is possible to supply the measurement target 1 with a signal at a desired frequency and at a desired level.

At this time, the correction circuit 6 of the signal analysis device 40
3 supplies the reference voltage Vrh corrected by the correction value corresponding to the frequency of the signal output from the signal generator 20 to the signal generator 20, so that the measurement target 1 has the signal analyzer 4
A signal of a level that matches the level Ls designated by the level designating unit 60 of 0 with high precision is input, and accurate measurement can be performed even on the measurement target 1 whose input level precision is severe.

When measuring the response characteristic of the measuring object 1 to the signal from the signal generator 20, the output signal of the measuring object 1 is passed through the cable 6 and the signal analyzing device 40 is used as shown in FIG. It may be input to the signal input terminal 42 of.

The above-mentioned measuring device was composed of the signal analysis device 40 each having an independent casing and the simple type signal generator 20 attached thereto.
As in the measuring device 70 shown in FIG. 1, it is possible to house the respective units 30 to 37 that constitute the signal generator 20 in the housing 41 and provide the signal output terminal 22 on the outer surface thereof.

Further, the signal analysis device 40 and the measurement device 70 described above have functions of spectrum measurement and reception demodulation in addition to wide band power measurement, but may include other signal analysis functions, In addition, the measuring device 8 shown in FIG.
As in 0, it may have only the wide band power measurement function as the signal analysis function.

In addition, in each of the above measuring devices, in order to correct the level of the output signal of the signal generator 20, the reference voltage for level stabilization is corrected and the gain of the amplifier 33 is variably controlled. However, this is not a limitation of the present invention, and may be provided between the frequency conversion circuit 34 and the attenuator 35,
An amplifier or an attenuator may be provided between the attenuator 35 and the signal output terminal 22, and the gain of the amplifier and the attenuation amount of the attenuator may be variably controlled.

[0059]

As described above, the measuring device of the present invention has the signal output terminal (2) for outputting a signal to the object to be measured.
2), a signal generator (30 to 37) that generates a signal of a specified level and outputs the signal to the signal output terminal, a signal input terminal (42) for inputting a signal to be measured, and the signal. Power measuring means (52) for measuring the power of the signal input from the input terminal, output level designating means (60) for designating the level of the signal output by the signal generating section to the signal output terminal, and the signal output Level difference detecting means (61) for detecting a difference between the level of electric power measured by the electric power measuring means and the level designated by the level designating means when the terminal and the signal input terminal are connected by a cable. And controlling the level of the output signal of the signal generating section so that the level difference detected by the level difference detecting means becomes substantially zero, and connecting the signal to the signal input terminal side. And a level correcting means to align to the specified level (63 to 65) by the level specifying means the level of the signal output from the end of Buru.

Therefore, the signal level at the end of the cable connected to the signal output terminal can be accurately set to the desired level.

Further, the signal analysis device of the present invention comprises a housing (4
1), a signal input terminal (42) provided on the outer surface of the housing for inputting a signal to be measured, and a power measuring means (51) for measuring the power of the signal input from the signal input terminal. ), A level designating means (60) for designating the level of the signal output from the signal output terminal of the signal generator to the external signal generator (20), the signal input terminal and the signal generator. Level difference detecting means (61) for detecting a difference between the level of electric power measured by the electric power measuring means and the level designated by the level designating means when the signal output terminals are connected by a cable.
And controlling the level of the output signal of the signal generating section so that the level difference detected by the level difference detecting means becomes substantially zero, and from the end of the cable connected to the signal input terminal side. Level correction means (63 to 65) for adjusting the level of the output signal to the level designated by the level designation means.

Therefore, the level of the signal at the end of the cable connected to the signal output terminal of the external signal generator can be accurately set to the desired level.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an appearance of an embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration example of a main part of the embodiment.

FIG. 4 is a block diagram showing a configuration example of a main part of the embodiment.

FIG. 5 is a block diagram showing a configuration example of a main part of the embodiment.

FIG. 6 is a diagram showing a connection state at the time of level calibration.

FIG. 7 is a diagram showing an example of a level change of an output signal with respect to a frequency change.

FIG. 8 is a diagram showing an example of a correction value obtained for each frequency.

FIG. 9 is a diagram showing a connection state when a measurement is performed by a signal generator.

FIG. 10 is a block diagram showing the configuration of an integrated measuring device.

FIG. 11 is a diagram showing the appearance of an integrated measuring device.

FIG. 12 is a block diagram showing a configuration of a measuring device having only a wideband power measuring function as a signal analyzing function.

FIG. 13 is a block diagram showing a configuration of a conventional signal generator.

[Explanation of symbols]

1 ... Measurement target, 2-5 ... Cable, 20 ... Signal generator, 21 ... Casing, 22 ... Signal output terminal, 25 ...
Local signal input terminal, 26 ... Level designation signal input terminal,
27 ... reference voltage input terminal, 30 ... reference signal generation circuit, 31 ... modulation signal generation circuit, 32 ... modulation circuit, 3
3 ... Amplifier, 34 ... Frequency conversion circuit, 35 ... Attenuator, 36 ... Level detection circuit, 37 ... Error detection circuit,
40 ... Signal analysis device, 41 ... Case, 42 ... Signal input terminal, 43 ... Operation section, 44 ... Display unit, 45 ... Local signal output terminal, 46 ... Level designation signal output terminal, Four
7: reference voltage output terminal, 50: mode designating means, 5
1 ... Signal changeover switch, 52 ... Power measurement circuit, 5
3 ... Frequency conversion circuit, 54 ... Local signal generation circuit, 5
5 ... Frequency control means 56 ... Logarithmic amplifier 57 ...
Demodulation circuit, 58 ... Display control means, 60 ... Level designation means, 61 ... Level difference detection means, 62 ... Reference voltage generation circuit, 63 ... Correction circuit, 64 ... Correction value detection means,
65 ... Correction value memory, 70, 80 ... Measuring device

Claims (2)

[Claims] 1. A signal output terminal (22) for outputting a signal to a measurement target, a signal generating section (30-37) for generating a signal of a designated level and outputting the signal to the signal output terminal, Signal input terminal (42) for inputting the target signal
Power measuring means (52) for measuring the power of the signal input from the signal input terminal, and output level designating means (60) for designating the level of the signal output by the signal generator to the signal output terminal. , A level difference detection for detecting a difference between the level of power measured by the power measuring means and the level designated by the level designating means when the signal output terminal and the signal input terminal are connected by a cable Means (61) and the cable connected to the signal input terminal side by controlling the level of the output signal of the signal generating section so that the level difference detected by the level difference detecting means becomes substantially zero. And a level correcting means (63 to 65) for adjusting the level of the signal output from the end of the to the level designated by the level designating means. 2. A housing (41), a signal input terminal (42) provided on an outer surface of the housing for inputting a signal to be measured, and power of a signal input from the signal input terminal. A power measuring means (51) for measuring the level, a level designating means (60) for designating the level of the signal output from the signal output terminal of the signal generator to the external signal generator (20), A level for detecting a difference between the level of power measured by the power measuring means and the level designated by the level designating means when the input terminal and the signal output terminal of the signal generator are connected by a cable. The level of the output signal of the signal generator is controlled so as to make the level difference detected by the level difference detection means and the level difference detection means substantially zero, and is connected to the signal input terminal side. The level of the signal output from the end of the cable was the signal analysis apparatus and a level correcting means to align to the specified level (63 to 65) by the level specifying means.