CN105445549A - Weak electromagnetic signal frequency spectrum measuring method - Google Patents
Weak electromagnetic signal frequency spectrum measuring method Download PDFInfo
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- CN105445549A CN105445549A CN201510929878.8A CN201510929878A CN105445549A CN 105445549 A CN105445549 A CN 105445549A CN 201510929878 A CN201510929878 A CN 201510929878A CN 105445549 A CN105445549 A CN 105445549A
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- frequency spectrum
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
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Abstract
The invention discloses a weak electromagnetic signal frequency spectrum measuring method. The weak electromagnetic signal frequency spectrum measuring method is characterized in that a measured radio frequency signal output port is connected with a superheterodyne device receiving path input port, and a device state requiring signal measurement can be set; scanning measurement can be carried out to acquire a group of frequency spectrum data; measured radio frequency signals and an input port of a superheterodyne device can be isolated, and the scanning measurement can be carried out to acquire another group of frequency spectrum data set, and then the threshold value can be determined; the error absolute value of the two groups of the frequency spectrum data can be calculated, and the comparison between the error absolute value and the threshold value can be carried out; when the error absolute value is smaller than the threshold value, the frequency spectrum measurement result of the radio frequency input signals can be the threshold value; when the error absolute value is not smaller than the threshold value, the frequency spectrum measurement result of the radio frequency input signals can be the error absolute value. The weak electromagnetic signal frequency spectrum measuring method is advantageous in that the accuracy of the weak signal level measurement can be improved without reducing the input attenuation or increasing the low noise amplification.
Description
Technical field
The present invention relates to a kind of weak electromagnetic signal frequency spectrum measuring method.
Background technology
Superheterodyne reception or analytical instrument carry out the most frequently used testing tool of electromagnetic signal spectrum measurement.Wherein heterodyne system spectrum analyzer have simply, flexibly, wide frequency range, sensitivity advantages of higher, be current the most widely used a kind of superhet instrument.The development of radiotelegraphy, to the Weak absorption sensitivity of spectrum analyzer and dynamic range index request more and more higher.
Measurable minimum signal level and dynamic range weigh the important indicator of spectrum analyzer Weak absorption ability.The ultimate principle of superhet spectrum analyzer as shown in Figure 1.
The signal that display measured by usual spectrum analyzer equals input signal+instrument intrinsic noise, and therefore measurable minimum signal is by the restriction of instrument intrinsic noise, and the index that manufacturer commonly uses display average noise level carrys out regulation instrument intrinsic noise size.
Display average noise level=-174dBm+F
dB+ 10log (RBW
noise/ Hz).
Wherein F
dBfor total noise of centrifuge coefficient, RBW
noiserepresent the equivalent noise bandwidth of instrument intermediate frequency resolution bandwidth filter.
In order to improve the accuracy of Weak absorption, prior art comprises: one is the noise figure FdB reducing instrument, namely input attenuator or unattenuated is reduced, or at instrument internal or outside increase amplifier circuit in low noise, thus reduce the noise level of screen display, improve feeble signal level measurement ability.
Another typical technological means existing reduces intermediate frequency resolution bandwidth RBW, reduces the noise energy that RBW can be reduced by intermediate-frequency filter, namely reduce the noise level of screen display.Although this method is only very effective for measurement sinusoidal signal level, cause measuring speed significantly to reduce simultaneously.If what wish to measure is the noise level of input signal, the channel power of the noise-like signals such as such as digital communication signal or neighboring trace rejection ratio are measured, reduce RBW and also will reduce the noise energy of input signal by intermediate-frequency filter simultaneously, measure signal to noise ratio (S/N ratio) still cannot improve, also cannot improve accuracy of measurement.
Another technological means existing, adopt and reduce video filter bandwidth VBW or adopt multiple averaging or adopt the smoothing action such as average value detection, also the measurement capability of feeble signal can be improved, the variance of measurement result that what but these means only reduced is, the accuracy of feeble signal level measurement can not be improved, display average noise level can not be reduced.
The existing technological means such as reducing attenuator, increase the noise figure of the reduction instruments such as low noise amplifier, not only significantly increase the hardware cost of instrument, when there is the frequency component of large level in input signal, input signal also can be caused to enter the power of instrument internal excessive, and damage internal circuit device.Even if input signal power, in the acceptable level range of instrument, also can cause certain nonlinear distortion usually, thus reduce measurement dynamic range, distortion component also may can affect the signal measurement of little level frequent components.By the restriction of current technique and manufacture level, the noise figure of instrument can not be reduced to zero, namely always there is intrinsic noise.When the level of input signal and instrument intrinsic noise level about close, signal level measuring accuracy is poorer.
Therefore, an existing difficult problem is: not by reducing input attenuation or increasing the means such as low noise amplification, by shifting to an earlier date surveying instrument noise level, then when performing measurement, noise of instrument level value is deleted, thus improve feeble signal level measurement accuracy, reduce instrument intrinsic noise further to the impact of Weak absorption, improve faint small signal levels accuracy of measurement.
Summary of the invention
The present invention is in order to solve the problem, propose a kind of weak electromagnetic signal frequency spectrum measuring method, this method by reducing input attenuation or increasing the means such as low noise amplification, does not improve feeble signal level measurement accuracy, and reduces instrument intrinsic noise further to the impact of Weak absorption.
To achieve these goals, the present invention adopts following technical scheme:
A kind of weak electromagnetic signal frequency spectrum measuring method, comprises the following steps:
(1) connect measured radio frequency signal output port to superhet instrument receiving path input port, the instrument state needing executive signal to measure is set;
(2) perform single pass to measure, obtain one group of frequency spectrum data;
(3) isolate between measured radio frequency signal and the input port of superhet instrument, perform single pass and measure, obtain another group sets of spectral data, determine its threshold value;
(4) ask for the Error Absolute Value of two groups of frequency spectrum datas, the size of error in judgement absolute value and threshold value, if Error Absolute Value is less than threshold value, then the spectrum measurement result of radio-frequency input signals is threshold value, otherwise spectrum measurement result is Error Absolute Value.
In described step (3), the confirmation method of threshold value is: Z (i)=X (i)/M, M value depends on the size of the background noise of superhet instrument, Z (i) is threshold value, X (i) for the element number that obtains of scanning survey after isolation be one group of frequency spectrum data of N, i=1,2,, N.
In described step (3), the method for isolation comprises following any one:
(1-1) connection of the input port of measured radio frequency signal and superhet instrument is disconnected, then by the input port matching connection load of superhet instrument;
(1-2) when superhet instrument input attenuator pad value is accurately known, can the input attenuation amount of superhet instrument be increased to maximum.
The concrete grammar of described step (4) is:
(4-1) obtain the Error Absolute Value of two groups of data, i.e. S ' (i)=| X (i)-Y (i) |; Wherein, Y (i) is that before isolation, the element number that obtains of scanning survey is one group of frequency spectrum data of N, i=1,2 ..., N;
If (4-2) S ' (i) < threshold value Z (i), then make S (i)=Z (i); Otherwise S (i)=S ' (i);
(4-3) using S (i) as the spectrum measurement result finally for radio-frequency input signals.
In described step (2), frequency spectrum data is frequency power numerical value.
In described step (3), frequency spectrum data is frequency power numerical value.
Beneficial effect of the present invention is:
(1) not by reducing input attenuation or increasing the means such as low noise amplification, improve feeble signal level measurement accuracy, cost is low;
(2) by reducing decay or increase low noise amplification to improve on the basis of Weak absorption ability, use this method still can reduce the impact of instrument intrinsic noise on Weak absorption further, improve faint small signal levels accuracy of measurement;
(3) the intermediate frequency resolution bandwidth (RBW) by reducing spectrum analyzer is solved, when improving the method for sinusoidal signal level measurement accuracy, the accuracy problems that insurmountable noise signal levels is measured;
(4) by reducing video filter bandwidth VBW or adopting multiple averaging or adopt on the basis of the smoothing action such as average value detection, this method is used still can to improve feeble signal level measurement accuracy further;
(5) the present invention and above-mentioned prior art means be not antagonistic, while the above-mentioned technological means of employing, the method that the present invention still can be adopted to propose improves feeble signal level measurement accuracy further.
Accompanying drawing explanation
Fig. 1 is the principle schematic of superhet spectrum analyzer of the present invention;
Fig. 2 is schematic flow sheet of the present invention.
Embodiment:
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
Feeble signal (measured radio frequency signal) the spectral measuring method operation steps as shown in Figure 2 that the present invention proposes:
Step 1: exact connect ion measured radio frequency signal output port is to superhet instrument receiving path input port;
Step 2: the instrument state needing executive signal to measure is set;
Step 3: perform single pass and measure, obtain one group of frequency spectrum data Y (i) that element number is N, i=1,2 ..., N;
Step 4: isolate between measured radio frequency signal and the input port of superhet instrument.
Step 5: perform single pass and measure, obtains another group frequency spectrum data X (i) that element number is N, i=1,2 ..., N;
Step 6: mathematical operation is performed to twice frequency spectrum data X (i) and Y (i), obtains S (i);
Step 7: using S (i) as the spectrum measurement result finally for radio-frequency input signals;
Wherein, one group of frequency spectrum data X (i) in step 3, X (i) is a class frequency magnitude of power, and unit is W.
Wherein, in step 5 another group frequency spectrum data Y (i), Y (i) for another class frequency magnitude of power, unit be W.
In step 6 to the rule that twice frequency spectrum data X (i) and Y (i) perform mathematical operation be:
1st step: obtain according to X (i) size that one group of threshold value Z (i), Z (i)=X (i)/M, M value depends on the background noise of superhet instrument, usual value is the arbitrary constant between 10 ~ 1000.
2nd step: the absolute value obtaining X (i)-Y (i), S ' (i)=| X (i)-Y (i) |;
3rd step: if S ' (i) <Z (i), then S (i)=Z (i); Otherwise S (i)=S ' (i).
Partition method in step 4 can be any one below among two methods, or other effective partition methods.Isolation is the bigger the better.
Method 1: the connection disconnecting the input port of measured radio frequency signal and superhet instrument, then by the input port matching connection load of superhet instrument.
Method 2: when superhet instrument input attenuator pad value is accurately known, can the input attenuation amount of superhet instrument is increased to maximum.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.
Claims (6)
1. a weak electromagnetic signal frequency spectrum measuring method, is characterized in that: comprise the following steps:
(1) connect measured radio frequency signal output port to superhet instrument receiving path input port, the instrument state needing executive signal to measure is set;
(2) perform single pass to measure, obtain one group of frequency spectrum data;
(3) isolate between measured radio frequency signal and the input port of superhet instrument, perform single pass and measure, obtain another group sets of spectral data, determine its threshold value;
(4) ask for the Error Absolute Value of two groups of frequency spectrum datas, the size of error in judgement absolute value and threshold value, if Error Absolute Value is less than threshold value, then the spectrum measurement result of radio-frequency input signals is threshold value, otherwise spectrum measurement result is Error Absolute Value.
2. a kind of weak electromagnetic signal frequency spectrum measuring method as claimed in claim 1, it is characterized in that: in described step (3), the confirmation method of threshold value is: Z (i)=X (i)/M, M value depends on the size of the background noise of superhet instrument, and Z (i) is threshold value, and X (i) is that after isolation, the element number that obtains of scanning survey is one group of frequency spectrum data of N, i=1,2 ..., N.
3. a kind of weak electromagnetic signal frequency spectrum measuring method as claimed in claim 1, is characterized in that: in described step (3), and the method for isolation comprises following any one:
(1-1) connection of the input port of measured radio frequency signal and superhet instrument is disconnected, then by the input port matching connection load of superhet instrument;
(1-2) when superhet instrument input attenuator pad value is accurately known, can the input attenuation amount of superhet instrument be increased to maximum.
4. a kind of weak electromagnetic signal frequency spectrum measuring method as claimed in claim 1, is characterized in that: the concrete grammar of described step (4) is:
(4-1) obtain the Error Absolute Value of two groups of data, i.e. S ' (i)=| X (i)-Y (i) |; Wherein, Y (i) is that before isolation, the element number that obtains of scanning survey is one group of frequency spectrum data of N, i=1,2 ..., N;
If (4-2) S ' (i) < threshold value Z (i), then make S (i)=Z (i); Otherwise S (i)=S ' (i);
(4-3) using S (i) as the spectrum measurement result finally for radio-frequency input signals.
5. a kind of weak electromagnetic signal frequency spectrum measuring method as claimed in claim 1, it is characterized in that: in described step (2), frequency spectrum data is frequency power numerical value.
6. a kind of weak electromagnetic signal frequency spectrum measuring method as claimed in claim 1, it is characterized in that: in described step (3), frequency spectrum data is frequency power numerical value.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106980045A (en) * | 2017-05-12 | 2017-07-25 | 北京航空航天大学 | A kind of high-frequency electromagnetic signal time-frequency characteristic measuring system and method |
| CN108918966A (en) * | 2018-05-23 | 2018-11-30 | 成都玖锦科技有限公司 | Bottom based on frequency spectrograph, which is made an uproar, offsets method |
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| CN108918966A (en) * | 2018-05-23 | 2018-11-30 | 成都玖锦科技有限公司 | Bottom based on frequency spectrograph, which is made an uproar, offsets method |
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Effective date of registration: 20220616 Address after: 266555 No. 98 Xiangjiang Road, Huangdao District, Qingdao City, Shandong Province Patentee after: CLP kesiyi Technology Co.,Ltd. Address before: 266555 No. 98 Xiangjiang Road, Qingdao economic and Technological Development Zone, Shandong Patentee before: THE 41ST INSTITUTE OF CHINA ELECTRONICS TECHNOLOGY Group Corp. |