JPS62225964A - Spectrum analyzer - Google Patents

Abstract

PURPOSE:To obtain the maximum dynamic range regardless of changes in display level of a noise, by making attenuation of an input attenuator operate in conjunction not only a reference level and a resolution band-width but also with a video band-width. CONSTITUTION:A control circuit 11 consists of an input attenuator setting means 12 which calculates and sets the attenuation of an input attenuator 1 enough to impart the maximum input level an input to a mixer 3 from a desired resolution band-width and a desired video band-width and reference level value; an intermediate frequency amplification factor setting means 13 which calculates and sets the amplification factor of an intermediate frequency amplifier 7 from the attenuation of the input attenuator 1 and the reference level value; a resolution band-width setting means 14 which selects a filter corresponding to a resolution band-width memorized in a memory means 16; and a video band-width setting means which selects a video filter 9 corresponding to a video band-width memorized into the memory means 16. The dynamic range can be kept at its maximum according to the attenuation and amplification factor set by the means 12 and 13 and with the filters 6 and 9 selected by the means 14 and 15.

Description

Detailed Description of the Invention (Industrial Application Field) [Industrial Field of Application] Uninventively, setting t% of the attenuation amount of a spectrum analyzer, sometimes a manual attenuator, and the amplification degree of an intermediate station V incrementer.
This invention relates to a spectrum analyzer configured in such a way that the dynamic range is always maximized by changing the reference level, the decomposition range, and the video bandwidth in conjunction with each other.

(Prior art) In order to make measurements by making the most of the dynamic range of a spectrum analyzer, it is necessary to set the mixer input value to an appropriate value, and in order to set the mixer input to an appropriate value. It is necessary to optimally set the attenuation amount of the input attenuator located before the mixer and the amplification degree of the intermediate frequency amplifier located after the mixer.

(Problems to be solved by the invention) In early spectrum analyzers, humans used judgment to set the attenuation t of the input attenuator, which was inconvenient and easy to make mistakes. There were drawbacks.

To improve this drawback, (1) a method of automatically setting the attenuation t of the input attenuator in conjunction with the reference level; (2) a method of automatically setting the attenuation t of the input attenuator by setting the reference level and resolution bandwidth (R, BW) to the attenuation t' of the input attenuator. A method has been proposed in which the settings are automatically set by exercising.

The level of the input signal under test is normally adjusted to the reference level using a spectrum analyzer. Here, the reference level refers to the level corresponding to the reference scale position of the display device.

By the way, the dynamic characteristics of the spectrum analyzer
The noise level is determined by both the distortion caused by the mixer and the noise level. That is, the upper limit of the dynamic range is determined by adjusting the distortion generated by the mixer91, and the lower limit is determined by adjusting the noise level.

In general, the average noise of a spectrum analyzer increases proportionally to the bandwidth and Benault resolution, but the noise level above the apparent σ displayed on the display device as a percentage of the video bandwidth (V, BW
), and the wider the video bandwidth, the larger it becomes.

Therefore, when the video bandwidth is changed, the apparent noise level changes, so it is not possible to obtain the optimum dynamic range simply by linking the attenuation amount of the input attenuator to the reference level and the resolution bandwidth.

The present invention aims to solve the above-mentioned drawbacks,
A spectrum analyzer that eliminates the input attenuator and is linked not only to the total reference level and resolution bandwidth, but also to the video bandwidth, allowing you to change the video bandwidth and always obtain the maximum dynamic range even when the displayed noise level changes. The purpose is to provide.

(A means of communication to solve problems) This purpose is one! In order to achieve the gist of obscurity.

From the values of reference level, resolution bandwidth and video bandwidth,
Set the input attenuator to the input attenuator so that the mixer input level of the input signal to be measured becomes the optimum input level after being attenuated by the input attenuator. - Set the intermediate frequency from the value of the input attenuator and the reference level value. Amplification degree? Then, the amplification degree of the intermediate frequency amplifier is set so as to obtain that value.

The inventive spectrum analyzer is equipped with an input attenuator 1 for wiping out the input signal to be measured, and a local oscillator 4 and a mixer 3 for converting the frequency of the output signal of the input attenuator 1. Frequency converter 2
And the desired frequency band? A filter 6 for passing, an intermediate frequency amplifier 7 for amplifying the output signal of the filter 6, a detector 8 for fully detecting the amplified intermediate station m signal, a video filter 9 for determining the bandwidth after detection, and a video filter 9 for determining the bandwidth after detection. Output of video filter 9? It includes a display device 10 for displaying images and a control circuit 11. and storage means 16 for storing a desired resolution bandwidth, a desired video bandwidth and a desired reference level in the control circuit 11; an input attenuator setting means 12 that calculates and sets the attenuation ti of the input attenuator 1 at which the input becomes an acceptable power level, and calculates the degree of increase of the intermediate frequency amplifier 7 from the attenuation amount of the input attenuator 1 and the reference level value. intermediate frequency amplification setting means 13 for setting the intermediate frequency amplification degree; resolution bandwidth setting means 14 for selecting all the filters corresponding to the resolution bandwidth stored in the storage means 16; and a video bandwidth setting means 15 for selecting the corresponding video filter 9? We are prepared. Based on the set reference level, resolution bandwidth, and video bandwidth, the attenuation amount of the input attenuator 1 and the amplification degree of the intermediate frequency amplifier 7 that maximize the dynamic range are automatically set.

(Function) In FIG. 1, the input signal to be measured input to the input attenuator 1 is attenuated in accordance with the attenuation tIC set by the input attenuator setting means 12 in the control circuit 11,
The frequency is converted by the frequency converter 2, and this frequency conversion is performed using a sweep signal generated from the station S oscillator 4. The control circuit 1 receives the intermediate frequency signal output from the mixer 3.
The signal passes through the filter 6 of the frequency band selected by the resolution bandwidth setting means 14 in the filter 1, and is input to the intermediate frequency amplifier 7. The intermediate frequency signal input to the intermediate frequency amplifier 7 is
Due to the amplification set in the intermediate frequency amplification setting means 13 of the control circuit 11P'3, the intermediate frequency amplification bandwidth setting means 1
The signal passes through a video filter 9 having a frequency band selected by adjusting the frequency band 5, and the detected output that has passed is displayed on a display device 10.

A storage means 16 within the control circuit 11 stores a desired resolution bandwidth, a desired reference level value and a desired video bandwidth. The storage means 1 is stored in the input attenuator setting means 12.
From the desired resolution bandwidth, reference level, and video bandwidth values stored in input attenuator 6, input attenuator 1 is configured such that the maximum input signal to mixer 3, which has been attenuated by input attenuator 1, becomes the optimum input level. Attenuation of t? The value is calculated and set to the input attenuator 1. The intermediate frequency amplification degree setting means 13 calculates the amplification degree of the intermediate frequency amplifier 7 from the attenuation amount of the input attenuator 1 calculated and set by the input attenuator setting means 12 and the reference level value stored in the storage means 16FC, The value is set in the intermediate frequency amplifier 7. The resolution bandwidth setting means 14 operates to select all filters corresponding to the resolution bandwidth stored in the storage means 16. Further, the video bandwidth setting means 15 functions to select a filter corresponding to the video bandwidth stored in the storage means 16.

In this process, the attenuation 1 of the input attenuator 1 is calculated and set respectively in the input attenuator setting means 12 and the intermediate frequency amplification degree setting means 13 in the control circuit 11. Amplification degree and resolution bandwidth setting means 14 for intermediate frequency amplifier 7. The operation described above is performed by the filter 6 and the video filter 1 which are respectively set and selected in the video bandwidth establishment means 15.

The dynamic range of the spectrum analyzer is maintained at maximum.

(Example) A specific example will be described below with reference to FIG. 2.

In the figure, 17Z to 11 correspond to those in FIG. The input signal to be measured inputted to the input attenuator 1 is attenuated by the control circuit 11 according to the amount of attenuation set in the input attenuator 1, and then inputted to the mixer 3 in the frequency converter 2. The input signal to be measured input to the mixer 3 is frequency-converted into an intermediate frequency signal by a sweep signal from the local oscillator 4.

The intermediate frequency 15 obtained by the frequency converter 2 is input to the intermediate frequency amplifier 7 via the filter 6 in the intermediate frequency amplifying section 5. The intermediate frequency signal inputted to the intercontinental frequency amplifier 7 is amplified by the control circuit 11 according to the m width set in the F intermediate frequency amplifier 7, detected by the post-resistance detector 8, and then passed through the video filter 9. is displayed on the display device [10].

By the way, 17 is a reference level setting key.

The maximum level of the input signal to be measured is displayed on the display device 1[0, for example, at the reference level on the ORT tube surface.

Use the key to set the reference level. 18 is a resolution bandwidth setting key, which is used to set the resolution bandwidth to be measured =9. The filter 5t in the intermediate frequency amplifier 5 is changed to a filter having filter characteristics corresponding to the set resolution bandwidth. 19 is the video bandwidth setting key, and should the video bandwidth be measured? By setting the filter characteristics according to the set video bandwidth? This is a key for filter selection that changes the video filter 9 to the filter that has the video filter.

The control circuit 11 has a reference level set in the reference level setting key 17, a resolution bandwidth set in the resolution bandwidth setting key 18, and a video bandwidth setting key 19.
Based on the video bandwidth set up in the construction 9, the attenuation amount of the input attenuator 1 is determined so that the input to the mixer 3 is at the upper limit level that does not cause distortion or blurring caused by the mixer 3, that is, the optimal human power level, and the corresponding attenuation amount. Input attenuator 1
A function to calculate the amplification degree of the intermediate frequency amplifier 7 according to the attenuation amount and reference level, a function to set the calculated decrease of the large power attenuator 1 to the input attenuator 1, and a function to set the calculated intermediate station V increase @ and a function for setting the amplification degree of the amplifier 7 to the intermediate frequency amplifier 7.

The filter 6?corresponds to the resolution bandwidth set with the resolution band fine setting key 18 and has filter characteristics of the resolution bandwidth. a- A filter selection function to change;
A filter selection function that changes the video filter 9 to a filter that corresponds to the video bandwidth set with the video bandwidth setting key 19 and has filter characteristics of the video bandwidth? We are prepared.

These are operated or controlled by a microprocessor or the like (not shown).

For example, if the resolution bandwidth and video bandwidth are set to R, BW(b), V, BW(b)K in FIG. 'L
, 'BW(b), a filter that corresponds to the video bandwidth V and BW(b), respectively? The filter 6 and video filter 9 of the intermediate frequency amplification s5 are selected, and the level of Lb at point Y in FIG. The amount of attenuation of the input attenuator 1 is set to the cutting edge. Also, when the reference level is adjusted to the level of all measured foot input signals, the input level to mixer 3 is [input level to mixer]
= [Input signal to be measured (i.e., reference level)] - [Attenuation amount of input attenuator] Therefore, the amplification degree of the intermediate frequency amplifier 7 can be obtained according to the attenuation amount of the input attenuator 1 and the reference level. A set value is output from the control circuit 11.

In addition, in Fig. 3, the value of resolution bandwidth BW is (a)<(
b) < (c) Terror, video bandwidth V, BWO value rc(
a) <(b) < (c)? It shows. And since the average noise level changes when R and BW change,
Even if V and BW are constant, does the noise level on the apparent σ change? It represents.

Also, when V and BW are the same, it is the same as the average noise level, but the apparent noise level above changes depending on V and BW.

Here, use the 1 resolution bandwidth setting key 18 to set the resolution bandwidth.
For example, change to 几, BW (cl, video bandwidth setting -?-
In step 19, if you change the video bandwidth by 1, for example, V, BW(c), and widen the resolution bandwidth and video bandwidth, the operating point will move from point Y to point 2 in Figure 3, and the average The apparent noise level increases with the noise level, and the 8/N becomes worse and the dynamic range becomes narrower. Therefore, the control circuit 11 adjusts the reference level set by the reference level setting key 17 and the resolution bandwidth R set by the reference level setting key 17. ,BW(c
) and the video bandwidth V, BW (c), the input attenuator 1 is set to the error where the dynamic range is maximum.
The attenuated wave sound of the input attenuator 1 is calculated so that the output level of the mixer 3, that is, the input level of the mixer 3 becomes Lc located at the point P shown in FIG. This calculated data is transmitted to the input attenuator 1, and the attenuation amount of the large-power attenuator 1 is set to this value. As a result, the optimum input level at which distortion and streaks do not occur is input to the mixer 3. Based on the attenuation amount of the input attenuator 1 and the reference level, the amplification degree of the intermediate frequency amplifier 7 is calculated by the control circuit 1'1, and this calculated data is transmitted to the intermediate frequency amplifier 7. Then, the amplification degree of the intermediate frequency amplifier 7 is set to the amplification factor. At the same time, as mentioned above, the resolution bandwidth setting key 18 contains the resolution bandwidth setting key 18, BW (c), and the video bandwidth setting key 191C.
J:! l The set video bandwidths V and BW (cl) are transmitted to the filter 6 and video filter 9 through the control circuit 11', so the filters for each corresponding bandwidth are has been selected.

′! For example, if the resolution bandwidth is set to 几, BW(a), and the video bandwidth is set to V, BW(a)vr-, then the point will be located at point Y shown in FIG. 3, as described above. Change the input level Lb to mixer 3 to the Q point! The input level La to the mixer 3 is calculated by the control circuit 11. Based on this human power level oil, the control circuit 11 raises and sets the amount of reduction of the large force attenuator 1 and the amplification degree of the intermediate frequency amplifier 7, respectively. The filter 6 has a filter corresponding to μ resolution bandwidth ratio, BW (a), and the video filter 9 has a video bandwidth V, BW (a).
Filters corresponding to each are set and selected.

Also, for example, with the same resolution bandwidth, BW(b),
Assuming that the video bandwidth is set from V, BW (cl to V, BW (a)), the input level Lr1C to the mixer 3 located at point R shown in FIG. The input level Ls to the mixer 3 located at 8 points is calculated by the control circuit 11. Based on the input level L8 of C, the control circuit 11 calculates the amount of reduction of the large power attenuator 10 and the amplification degree of the intermediate frequency amplifier 7, respectively. A filter corresponding to the resolution bandwidth R, BW(b) is installed in the filter 6, and a filter corresponding to the video bandwidth Vcr[, video bandwidth V, BW(a) is installed/selected. An example of the waveform at C is shown in FIG.

Figure 4 (1), (the resolution bandwidth is the same as nl,
BW, and the waveform diagram when the video bandwidth V and BW are different. Figure 4 (video bandwidth of Il is V, BW(c
l, and the video bandwidth rX, V, in FIG. 4 (11)
BW (a) T h'), V, BW (c)) V
, has the relationship BW(a).

Therefore, the video bandwidth changes from V,BW(c) to V,BW(
When set to a), the video filter 9 apparently suppresses the upper noise level as shown in FIG. No. 1g component 30 has become apparent.

In this way, the noise level, which varies depending on the resolution bandwidth and video bandwidth, is minimized, and the distortion and noise caused by mixer 3 are minimized. Optimal value of input attenuator 1 to minimize? This value is automatically added to all input attenuators 1 to obtain the optimum input level to mixer 3, and the amplification level is determined accordingly. It is automatically set to the intermediate frequency amplifier and always operates to maximize the dynamic range.

In addition, the diagram shown in FIG. 3 is made into a table.

For example, the resolution bandwidth set in the storage means 16 with the 1-resolution bandwidth setting key 18 and the video bandwidth set with the video bandwidth setting key 19 are stored in the storage means 16. The table in Figure 3? access,
It is also possible to determine the optimum input level r of the large-power attenuator 1 by using two.

(Effect of the invention) As explained above, according to non-invention.

Even if the measurer arbitrarily changes the reference level, resolution bandwidth, and video bandwidth 1m'r measurement conditions, the input level to the mixer will be controlled to the optimum human power level by adjusting these settings. , the dynamic range is always at its maximum. Therefore, the measurement operation becomes easy.

Troublesome operation? Since this is not necessary, the measurement time for the signal under test can be shortened, and the dynamic range can be reliably adjusted to the maximum state.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the spectrum analyzer according to the invention, Fig. 2 is a specific example of the spectrum analyzer according to the invention, and Fig. 3 is the characteristics of the homomixer input level and the distortion and noise level caused by the mixer. Figure 4 shows the change in noise level due to change in video bandwidth? O explaining
This is a waveform diagram of the RT tube surface. In the figure, 1 is an input attenuator, 2 is a frequency converter, 3 is a mixer, 4 is a local oscillator, 5 is an intermediate frequency amplification section, 6 is a filter % 7μ inter-A frequency amplifier, 8 is a detector, 9 is a video filter, 10r+, device on the front. 11rX is a control circuit; 12 is an input attenuator setting means; 13 is an instep circumference increasing @degree setting means; 14jC resolution bandwidth setting means; 15rx is a video imperial width setting means. 16 is a storage means, 17 is a reference level setting key, 18 is a decomposition range setting key, and 19 is a video bandwidth setting key.

Claims (1)

[Claims] A frequency converter (1) comprising an input attenuator (1) that attenuates an input signal to be measured, and a local oscillator (4) and a mixer (3) that converts the frequency of the output signal of the input attenuator.
2) and a filter (6) that passes the desired frequency band
and an intermediate frequency amplifier (
7) and a detector (8) that detects the amplified intermediate frequency signal.
), a video filter (9) that determines the bandwidth after detection, and a display device (10) that displays the output of the video filter.
and a control circuit, the control circuit comprising: (a) storage means (16) for storing a desired resolution bandwidth, a desired video bandwidth and a desired reference level; and (b) )
input attenuator setting means (12) for calculating and setting an attenuation amount of an input attenuator such that the input to the mixer has an optimum input level from the resolution bandwidth, video bandwidth and reference level value stored in the storage means; c) intermediate frequency amplification degree setting means (13) for calculating and setting the amplification degree of the intermediate frequency amplifier from the attenuation amount of the input attenuator and the reference level value, and (d) the resolution bandwidth stored in the storage means. (e) video bandwidth setting means (14) corresponding to the video bandwidth stored in the storage means and selecting the video filter;
5) It is characterized by being able to automatically set the attenuation amount of the input attenuator and the amplification degree of the intermediate frequency amplifier to maximize the dynamic range based on the set reference level, resolution bandwidth, and video bandwidth. spectrum analyzer.