CN105445549B - A kind of weak electromagnetic signal frequency spectrum measuring method - Google Patents
A kind of weak electromagnetic signal frequency spectrum measuring method Download PDFInfo
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- CN105445549B CN105445549B CN201510929878.8A CN201510929878A CN105445549B CN 105445549 B CN105445549 B CN 105445549B CN 201510929878 A CN201510929878 A CN 201510929878A CN 105445549 B CN105445549 B CN 105445549B
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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 kind of weak electromagnetic signal frequency spectrum measuring methods, comprising the following steps: connection measured radio frequency signal output port to superhet instrument receiving path input port, setting need to be implemented the instrument state of signal measurement；Single pass measurement is executed, one group of frequency spectrum data is obtained；It is isolated between measured radio frequency signal and the input port of superhet instrument, executes single pass measurement, obtain another group of sets of spectral data, determine its threshold value；The Error Absolute Value of two groups of frequency spectrum datas, the size of error in judgement absolute value and threshold value are sought, if Error Absolute Value is less than threshold value, the spectrum measurement result of radio-frequency input signals is threshold value, and otherwise spectrum measurement result is Error Absolute Value.The present invention, which does not pass through, to be reduced input attenuation or increases the means such as low noise amplification, and small-signal level measurement accuracy is improved.
Description
Technical field
The present invention relates to a kind of weak electromagnetic signal frequency spectrum measuring methods.
Background technique
Superheterodyne reception or analysis instrument are to carry out the most common test equipment of electromagnetic signal spectrum measurement.Wherein heterodyne system
Spectrum analyzer has many advantages, such as simple, flexible, wide frequency range, high sensitivity, is the most widely used at present a kind of super
Heterodyne instrument.The continuous development of radio technology, Weak absorption sensitivity and dynamic range index to spectrum analyzer
It is required that higher and higher.
Measurable minimum signal level and dynamic range are the important of measurement spectrum analyzer Weak absorption ability
Index.The basic principle of superhet spectrum analyzer is as shown in Figure 1.
The signal of usual spectrum analyzer measurement display is equal to input signal+instrument intrinsic noise, thus it is measurable most
Small signal is limited by instrument intrinsic noise, and the index that manufacturer commonly uses display average noise level carrys out regulation instrument and inherently makes an uproar
Sound size.
Show average noise level=- 174dBm+FdB+10log(RBWnoise/Hz)。
Wherein FdBFor total noise of centrifuge coefficient, RBWnoiseIndicate the equivalent noise band of instrument intermediate frequency resolution bandwidth filter
It is wide.
In order to improve the accuracy of Weak absorption, prior art includes: first is that reducing the noise coefficient of instrument
FdB, i.e. reduction input attenuator or unattenuated, or in instrument internal or external increase amplifier circuit in low noise, to reduce
The noise level that screen is shown improves small-signal level measurement ability.
Another existing typical technological means is to reduce intermediate frequency resolution bandwidth RBW, and reduction RBW, which can reduce, to be passed through
The noise level that the noise energy of intermediate-frequency filter, i.e. reduction screen are shown.Although this method is only for measuring sinusoidal signal
Level is highly effective, but causes measuring speed to be greatly lowered simultaneously.If it is desired to what is measured is the noise level of input signal,
Such as the channel power or neighboring trace of the noise-like signals such as digital communication signal inhibit than measurement, reducing RBW will also reduce simultaneously
By the noise energy of intermediate-frequency filter, measuring signal-to-noise ratio can not still improve input signal, can not also improve accuracy of measurement.
Another existing technological means using reduction video filter bandwidth VBW or uses multiple averaging or use
The smoothing actions such as average value detection, also can be improved the measurement capability of small-signal, but what these means only reduced is measurement
As a result variance can not improve the accuracy of small-signal level measurement, can not reduce display average noise level.
The technological means of the noise coefficient of the existing reduction instrument such as reducing attenuator, increase low-noise amplifier,
The hardware cost of instrument is not only significantly increased, in input signal there are when the frequency component of big level, also will cause input signal
Power into instrument internal is excessive, and damages internal circuit device.Even if input signal power is in the acceptable level of instrument
In range, certain non-linear distortion usually will also result in, to reduce measurement dynamic range, distortion component may also be will affect
The signal measurement of small level frequent components.It is limited by current technique and manufacture level, the noise coefficient of instrument can not reduce
To zero, i.e., always there is intrinsic noise.When the level and instrument intrinsic noise level of input signal are about close, signal level measuring
Accuracy is poorer.
Therefore, existing problem is: not by reducing input attenuation or increasing the means such as low noise amplification, by advance
Then during measurement measuring instrument noise level is deleted noise of instrument level value, to improve small-signal level
Accuracy of measurement further decreases influence of the instrument intrinsic noise to Weak absorption, improves faint small signal levels measurement
Accuracy.
Summary of the invention
The present invention to solve the above-mentioned problems, proposes a kind of weak electromagnetic signal frequency spectrum measuring method, and this method is obstructed
It crosses reduction input attenuation or increases the means such as low noise amplification, improve small-signal level measurement accuracy, and further decrease
Influence of the instrument intrinsic noise to Weak absorption.
To achieve the goals above, the present invention adopts the following technical scheme:
A kind of weak electromagnetic signal frequency spectrum measuring method, comprising the following steps:
(1) connection measured radio frequency signal output port is needed to be implemented to superhet instrument receiving path input port, setting
The instrument state of signal measurement；
(2) single pass measurement is executed, one group of frequency spectrum data is obtained；
(3) it is isolated between measured radio frequency signal and the input port of superhet instrument, executes single pass measurement,
Another group of sets of spectral data is obtained, determines its threshold value；
(4) Error Absolute Value of two groups of frequency spectrum datas, the size of error in judgement absolute value and threshold value, if error is absolute are sought
Value is less than threshold value, then the spectrum measurement result of radio-frequency input signals is threshold value, and otherwise spectrum measurement result is Error Absolute Value.
In the step (3), the confirmation method of threshold value are as follows: Z (i)=X (i)/M, M value depend on the sheet of superhet instrument
The size of back noise, Z (i) are threshold value, and X (i) is one group of frequency spectrum data that the element number that scanning survey obtains after being isolated is N, i
=1,2 ..., N.
In the step (3), the method for isolation include it is below any one:
(1-1) disconnects the connection of the input port of measured radio frequency signal and superhet instrument, then by superhet instrument
The load of input port matching connection；
(1-2), can be by superhet instrument in the case where superhet instrument input attenuator pad value is accurately known
Input attenuation amount increases to maximum.
The step (4) method particularly includes:
(4-1) finds out the Error Absolute Value of two groups of data, i.e., S ' (i)=| X (i)-Y (i) |；Wherein, Y (i) is before being isolated
The element number that scanning survey obtains is one group of frequency spectrum data of N, i=1,2 ..., N；
(4-2) enables S (i)=Z (i) if S ' (i) < threshold value Z (i)；Otherwise S (i)=S ' (i)；
(4-3) is by S (i) as the final spectrum measurement result for being directed to radio-frequency input signals.
In the step (2), frequency spectrum data is frequency power numerical value.
In the step (3), frequency spectrum data is frequency power numerical value.
The invention has the benefit that
(1) it is accurate small-signal level measurement is not improved by reducing input attenuation or increasing the means such as low noise amplification
Degree, it is at low cost；
(2) on the basis of by reducing decaying or increasing low noise amplification raising Weak absorption ability, this is used
Method still can further decrease influence of the instrument intrinsic noise to Weak absorption, improve faint small signal levels measurement
Accuracy；
(3) it solves the intermediate frequency resolution bandwidth (RBW) by reducing spectrum analyzer, improves sinusoidal signal level measurement
When the method for accuracy, the accuracy problems of insurmountable noise signal levels measurement；
(4) by reducing video filter bandwidth VBW or smoothly being arranged using multiple averaging or using average value detection etc.
On the basis of applying, small-signal level measurement accuracy still can be further improved using this method；
(5) present invention with above-mentioned prior art means and be not antagonistic, still can be with while use above-mentioned technological means
Small-signal level measurement accuracy is further increased using method proposed by the present invention.
Detailed description of the invention
Fig. 1 is the schematic illustration of superhet spectrum analyzer of the invention；
Fig. 2 is flow diagram of the invention.
Specific embodiment:
The invention will be further described with embodiment with reference to the accompanying drawing.
Small-signal (measured radio frequency signal) spectral measuring method proposed by the present invention operating procedure as shown in Figure 2:
Step 1: correct connection measured radio frequency signal output port to superhet instrument receiving path input port；
Step 2: setting needs to be implemented the instrument state of signal measurement；
Step 3: executing single pass measurement, obtain one group of frequency spectrum data Y (i), i=1,2 ... that element number is N, N；
Step 4: being isolated between measured radio frequency signal and the input port of superhet instrument.
Step 5: single pass measurement is executed, another group of the frequency spectrum data X (i), i=1,2 ... that element number is N are obtained,
N；
Step 6: mathematical operation being executed to frequency spectrum data X (i) twice and Y (i), obtains S (i)；
Step 7: by S (i) as the final spectrum measurement result for being directed to radio-frequency input signals；
Wherein, one group of frequency spectrum data X (i) in step 3, X (i) are a set of frequencies magnitude of power, unit W.
Wherein, another group of frequency spectrum data Y (i) in step 5, Y (i) are another group of frequency power numerical value, unit W.
It is to frequency spectrum data X (i) twice and Y (i) rule for executing mathematical operation in step 6:
Step 1: one group of threshold value Z (i), Z (i)=X (i)/M are found out according to X (i), M value depends on the sheet of superhet instrument
The size of back noise, usual value are the arbitrary constant between 10~1000.
Step 2: finding out the absolute value of X (i)-Y (i), and S ' (i)=| X (i)-Y (i) |；
Step 3: if S ' (i) < Z (i), S (i)=Z (i)；Otherwise S (i)=S ' (i).
Partition method in step 4 can be any one or other effective isolation sides among following two method
Method.Isolation is the bigger the better.
Method 1: the connection of the input port of measured radio frequency signal and superhet instrument is disconnected, then by superhet instrument
The load of input port matching connection.
Method 2:, can be by superhet instrument in the case where superhet instrument input attenuator pad value is accurately known
Input attenuation amount increases to maximum.
Above-mentioned, although the foregoing specific embodiments of the present invention is described with reference to the accompanying drawings, not protects model to the present invention
The limitation enclosed, those skilled in the art should understand that, based on the technical solutions of the present invention, those skilled in the art are not
Need to make the creative labor the various modifications or changes that can be made still within protection scope of the present invention.
Claims (3)
1. a kind of weak electromagnetic signal frequency spectrum measuring method, it is characterized in that: the following steps are included:
(1) connection measured radio frequency signal output port needs to be implemented signal to superhet instrument receiving path input port, setting
The instrument state of measurement；
(2) single pass measurement is executed, one group of frequency spectrum data is obtained；
(3) it is isolated between measured radio frequency signal and the input port of superhet instrument, partition method is to disconnect tested penetrate
The connection of the input port of frequency signal and superhet instrument, then by the input port matching connection load of superhet instrument or
In the case that superhet instrument input attenuator pad value is accurately known, the input attenuation amount of superhet instrument is increased into maximum
Any one, execute single pass measurement, obtain another group of sets of spectral data, determine its threshold value；
(4) 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 small are sought
In threshold value, then the spectrum measurement result of radio-frequency input signals is threshold value, and otherwise spectrum measurement result is Error Absolute Value；
In the step (2), frequency spectrum data is frequency power numerical value；
In the step (3), frequency spectrum data is frequency power numerical value.
2. a kind of weak electromagnetic signal frequency spectrum measuring method as described in claim 1, it is characterized in that: in the step (3), threshold
The confirmation method of value are as follows: Z (i)=X (i)/M, M value depend on the size of the background noise of superhet instrument, and Z (i) is threshold value,
X (i) is one group of frequency spectrum data that the element number that scanning survey obtains after being isolated is N, i=1,2 ..., N.
3. a kind of weak electromagnetic signal frequency spectrum measuring method as described in claim 1, it is characterized in that: the tool of the step (4)
Body method are as follows:
(3-1) finds out the Error Absolute Value of two groups of data, i.e., S ' (i)=| X (i)-Y (i) |；Wherein, Y (i) is scanning before isolation
Measure one group of frequency spectrum data that obtained element number is N, i=1,2 ..., N；
(3-2) enables S (i)=Z (i) if S ' (i) < threshold value Z (i)；Otherwise S (i)=S ' (i)；
(3-3) is by S (i) as the final spectrum measurement result for being directed to radio-frequency input signals.
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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 |
| CN108918966B (en) * | 2018-05-23 | 2020-06-23 | 成都玖锦科技有限公司 | Bottom noise cancellation method based on frequency spectrograph |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1344068A (en) * | 2000-09-19 | 2002-04-10 | 华为技术有限公司 | Method and device for decreasing intrinsic noise of radio receiver |
| CN104062004A (en) * | 2014-06-13 | 2014-09-24 | 中国科学院西安光学精密机械研究所 | Extremely weak optical signal detecting device and method |
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| JP3454206B2 (en) * | 1999-11-10 | 2003-10-06 | 三菱電機株式会社 | Noise suppression device and noise suppression method |
| CN1332186C (en) * | 2004-11-25 | 2007-08-15 | 上海交通大学 | Weak signal detection under complex background and characteristic analysis system |
| CN103136443A (en) * | 2013-01-27 | 2013-06-05 | 长春理工大学 | Method for estimating weak signal amplitude under alpha noise background |
| CN103178860A (en) * | 2013-03-06 | 2013-06-26 | 郑州大学 | Electromagnetic detecting system capable of eliminating background noise and method for eliminating background noise |
| US9319084B2 (en) * | 2013-03-13 | 2016-04-19 | Futurewei Technologies, Inc. | Noise cancellation apparatus and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1344068A (en) * | 2000-09-19 | 2002-04-10 | 华为技术有限公司 | Method and device for decreasing intrinsic noise of radio receiver |
| CN104062004A (en) * | 2014-06-13 | 2014-09-24 | 中国科学院西安光学精密机械研究所 | Extremely weak optical signal detecting device and 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. |