CN102095930B - Method for identifying external automatic signal of preselector-free frequency spectrograph under external mixing mode - Google Patents

Abstract

The invention provides a method for identifying an external signal of a preselector-free frequency spectrograph under an external mixing mode, which comprises the following steps of: forming a mixing signal by mixing a harmonic wave of a first-order local oscillation signal from the frequency spectrograph and the external signal in an external mixer; filtering the mixing signal by using an intermediate-frequency filter in the frequency spectrograph to form an intermediate-frequency signal, and displaying multiple response spectral lines corresponding to the intermediate-frequency signal by using the frequency spectrograph; acquiring frequency data of the multiple response spectral lines; and identifying the external signal at intervals according to the acquired frequency of the spectral lines. According to the method, the external signal can be analyzed accurately by the frequency spectrograph without the function of signal identification during the frequency spread of the preselector-free external mixer.

Description

Without the outside automatic signal recognition methods under the outer mixing mode of preselector frequency spectrograph

Technical field

The invention belongs to the spectrum analysis field of microwave signal, particularly relate to a kind of signal recognition method.

Background technology

The frequency of operation of spectrum analyzer all-in-one is the highest at present can arrive 70GHz.For such spectrum analyzer can be worked in higher frequency, generally need to connect outer frequency mixer spectrum analyzer is carried out spread spectrum.Used outer frequency mixer frequency spectrograph frequency of operation in addition can reach 320GHz.Outer frequency mixer divides two kinds, and is a kind of with preselector, and another is not with preselector.Frequency mixer cost ratio with preselector will not held high more expensive with the frequency mixer of preselector, and can only accomplish 75GHz with the maximum operation frequency of the frequency mixer of preselector in the market, works on 75GHz and can only use the frequency mixer of not being with preselector.

Usually the outer frequency mixer that frequency spectrograph is carried out spread spectrum has adopted the working method of harmonic mixing.The problem of this mixing mode is that frequency spectrograph None-identified " multiple " response can appear in the input signal of single-frequency after mixing.Can eliminate this " multiple " response with the frequency mixer of preselector, so that when input needed to analyze the signal of single-frequency, frequency spectrograph was only exported a spectral line that equates with the frequency of input signal.Yet outer frequency mixer is after the input signal of single-frequency enters frequency mixer during without preselector, because the existence of " multiple " response after the mixing, the output of frequency spectrograph will demonstrate many spectral lines, causes being difficult to the frequency spectrum of input signal is analyzed.

Fig. 1 illustrates the schematic diagram of the Spectrum Analyzer System 100 of prior art.Spectrum Analyzer System 100 comprises without preliminary election frequency mixer 2, frequency spectrograph 3.The signal that Spectrum Analyzer System 100 will be analyzed is that frequency range is 75GHz～110GHz by the millimeter-wave signal of for example W wave band of signal source 1 generation.For making frequency spectrograph 3, the sweep limit of its single order local oscillation signal for example is 3GHz～6.8GHz, frequency of operation expand to the wave band that comprises this millimeter-wave signal, adopted 2 pairs of these frequency spectrographs of outer frequency mixer without preselector to carry out spread spectrum.The single order local oscillation signal f of frequency spectrograph in this case _LOSend into frequency mixer.Because frequency mixer is non-linear, this single order local oscillation signal of frequency spectrograph has produced abundant harmonic wave in frequency mixer.Frequency spectrograph 3 is operated in the harmonic mixing mode in this case.Fig. 2 illustrates the fundamental diagram of the harmonic mixing of Spectrum Analyzer System shown in Figure 1.

The input signal f that in Fig. 2, is produced by signal source among Fig. 11 _SWith the single order local oscillation signal f from frequency spectrograph _LOCarry out harmonic mixing in frequency mixer 2, the mixed frequency signal behind harmonic mixing exports the intermediate-frequency filter of frequency spectrograph to.When the frequency of this mixed frequency signal equals the centre frequency of this intermediate-frequency filter, i.e. input signal f _SWith single order local oscillation signal f _LOHarmonic wave when satisfying formula (1), this mixed frequency signal just can become intermediate-freuqncy signal f by this intermediate-frequency filter _IF, this intermediate-freuqncy signal f then _IFFurther processing through frequency spectrograph demonstrates spectral line at display screen.

f _S＝n·f _LO±f _IF (1)

F in the formula _SThe frequency of input signal, f _LOBe the frequency of frequency spectrograph single order local oscillation signal, n is positive integer, the overtone order of expression single order local oscillation signal harmonic wave, f _IFThe centre frequency of frequency spectrograph intermediate-frequency filter, for example

f _IF＝310.7MHz

Generally speaking, when frequency spectrograph is carried out spread spectrum, only select in the whole sweep limit of frequency spectrograph a band frequency scope for example 4.15GHz～6.09GHz as single order local oscillation signal f _LOScan.As input signal f _SWhen for example being the millimeter-wave signal of 75GHz～110GHz, for the formula (2) that is obtained by formula (1)

$n=\frac{f_S\stackrel{\‾}{+}{f}_{\mathrm{IF}}}{f_{\mathrm{LO}}}---\left(2\right)$

F _LOAnd f _SThe bound of sweep limit and the centre frequency f of intermediate-frequency filter _IFThis formula of substitution (2) can get:

$n_{\min }=\mathrm{INT}\left(\frac{75-0.3107}{6.09}\right)=12$

$n_{\max }=\mathrm{INT}\left(\frac{110+0.3107}{4.15}\right)=26$

INT is bracket function in the formula, namely the single order local oscillation signal 4.15GHz～6.09GHz frequency sweeping scope scan the input of above-mentioned millimeter wave during one week the possible span of n be 12～26.

For a definite input signal f _S, the harmonic wave of which local frequency and input signal f in the time of can deriving single order local oscillation signal run-down by formula (1) _SMixing has generated the response spectral line.Computing formula is as follows:

$f_{\mathrm{LO}}=\frac{f_S\stackrel{\‾}{+}{f}_{\mathrm{IF}}}{n}---\left(3\right)$

Formula (4-1) and (4-2) show that can obtain two frequencies for same n value uses respectively

The local oscillation signal of expression

$f_{\mathrm{LO}}^{n+}=\frac{f_S-f_{\mathrm{IF}}}{n}---(4-1)$

$f_{\mathrm{LO}}^{n-}=\frac{f_S+f_{\mathrm{IF}}}{n}---(4-2)$

Wherein working as frequency is

The nth harmonic of local oscillation signal add the centre frequency f of intermediate-frequency filter _IFWith input signal f _SWhen equating, the nth harmonic of this local oscillation signal and the mixing of input signal are called " n+ " mixed-mode; With should frequency being

The nth harmonic of local oscillation signal deduct the centre frequency f of intermediate-frequency filter _IFRear and input signal f _SWhen equating,

The nth harmonic of the local oscillation signal of frequency and the mixing of input signal are called " n-" mixed-mode.

By formula (4-1) and (4-2) as can be known, corresponding two local frequencies of each n value.Usually by frequency being respectively

Nth harmonic and the frequency of local oscillation signal be The nth harmonic of local oscillation signal and the input signal mixing after the response spectral line that produces claim " each other mirror image ", so among this embodiment when n changes in the scope of 12≤n≤26, produce 15 to " mirror image " spectral line after having the harmonic wave of 15 pairs of local oscillation signals and input signal mixing, these spectral lines are exactly " multiple " response that the frequency spectrograph of no signal recognition function may occur on display when adopting without preselector frequency mixer spread spectrum.

Some has the function of signal identification in the existing frequency spectrograph, the realization of this function is the local oscillation signal that obtains departing from by the local oscillation signal frequency departure one number value that makes frequency spectrograph, respectively local oscillation signal and the local oscillation signal and the input signal that depart from are carried out mixing, then compare mixing results, and then obtain the frequency spectrum of input signal.This frequency spectrograph can be selected the frequency mixer of not being with preselector during the frequency mixer spread spectrum outside using.A lot of frequency spectrographs itself do not possess the function of signal identification in the reality, the phenomenon of " multiple " response will appear in this class frequency spectrograph inevitably when adopting without the outer frequency mixer spread spectrum of preselector, will carry out accurate analysis to the frequency spectrum of signal in this case and must seek new method.

Summary of the invention

The problem to be solved in the present invention is exactly " multiple " response that produces when eliminating the frequency mixer spread spectrum, provides the accurate spectral line frequency of input signal.

Foregoing " multiple " response meeting demonstrates the response spectral line of different frequency at the display screen of frequency spectrograph.For the frequency spectrograph with the work of harmonic mixing working method, in general, specified mixed-mode was noted as " N+ " or " N-" when frequency spectrograph was used the frequency mixer spread spectrum, the mixed-mode that is called the frequency spectrograph appointment herein, be that frequency spectrograph shows that the frequency of spectral line is that appointment mixed-mode " N+ " or " N-" according to single order local oscillation signal harmonic wave and external signal demarcates, the such spectral line frequency f on the frequency spectrograph display screen _N, namely the nominal frequency value of frequency spectrograph is pressed following formula and is demarcated

f _N＝N _±·f _LO±f _IF (5)

Generally, when the single order local oscillation signal of frequency spectrograph in its sweep limit interscan during one week, will the response spectral line occur at the frequency spectrograph display screen in case the harmonic wave of certain local oscillation signal and input signal have satisfied mixing formula (1), no matter mixed-mode is " n+ " or " n-".Behind selected frequency spectrograph, under the mixed-mode of determining, the frequency showing screen display of response spectral line is followed formula (5), thus " multiple " thus the response spectral line is because corresponding different single order local oscillation signal has demonstrated different frequency values at the frequency spectrograph display screen.Consider with the single order local oscillation signal same input signal f _SCarry out the response that mixing produces, (4-1) and (4-2) formula substitution (5) formula are obtained

$f_N^{n+}=N_{\±}\·\frac{f_S-f_{\mathrm{IF}}}{n}\±f_{\mathrm{IF}}---(6-1)$

$f_N^{n-}=N_{\±}\·\frac{f_S+f_{\mathrm{IF}}}{n}\±f_{\mathrm{IF}}---(6-2)$

When the frequency spectrograph that equals in the formula (5) to determine as the overtone order n of single order local oscillation signal is demarcated overtone order N, if frequency spectrograph is N in the mixed-mode of this frequency range appointment ₊, " n=N ₊" time, formula (6-1) and (6-2) become

$f_N^{n+}=N_{+\·}\frac{f_S-f_{\mathrm{IF}}}{n}+f_{\mathrm{IF}}=f_S-f_{\mathrm{IF}}+f_{\mathrm{IF}}=f_S---(7-1)$

$f_N^{n-}=N_{+}\·\frac{f_S+f_{\mathrm{IF}}}{n}+f_{\mathrm{IF}}=f_S+f_{\mathrm{IF}}+f_{\mathrm{IF}}=f_S+2f_{\mathrm{IF}}---(7-2)$

If (5) mixed-mode of appointment is N in the formula _-, " n=N _-" time, formula (6-1) and (6-2) become

$f_N^{n+}=N_{-}\frac{f_S-f_{\mathrm{IF}}}{n}-f_{\mathrm{IF}}=f_S-f_{\mathrm{IF}}-f_{\mathrm{IF}}=f_{S-}2f_{\mathrm{IF}}---(8-1)$

$f_N^{n-}=N_{-}\·\frac{f_S+f_{\mathrm{IF}}}{n}-f_{\mathrm{IF}}=f_S+f_{\mathrm{IF}}-f_{\mathrm{IF}}=f_S---(8-2)$

Formula (7) and (8) illustrate when the nth harmonic of single order local oscillation signal and input signal mixing generation response spectral line, when the specified mixed-mode of spot frequency is consistent when this time mixed-mode and frequency spectrograph spread to this wave band, the display frequency of response spectral line namely is the frequency of input signal, it is formula (7-1) or (8-2), this spectral line is exactly the frequency spectrum of input signal, is called " true signal " spectral line.With the display frequency of the spectral line of this spectral line " each other mirror image " be (7-2) and (8-1) than the high 2 times of intermediate frequencies of " true signal " spectral line or low 2 times of intermediate frequencies.

Other each other the frequency interval between the spectral line of mirror image subtract (6-1) formula by (6-2) formula and obtain

${\mathrm{\Δf}}_N^n=f_N^{n-}-f_N^{n+}=\frac{N_{\±}}{n}\·2f_{\mathrm{IF}}---\left(9\right)$

So far as can be known, only has n=N _±The time, the input signal of sign f is just arranged in a pair of spectral line of " each other mirror image " _S" true signal " spectral line, and the distance between the two mirror image spectral lines is 2f _IFIf the mixed-mode of appointment is " N ₊", be spaced apart so 2f _IF" mirror image " spectral line medium frequency low be " true signal " spectral line; If the mixed-mode of appointment is " N _-", be spaced apart so 2f _IF" mirror image " spectral line medium frequency high be " true signal " spectral line.

The present invention namely is that to utilize the frequency interval relation that exists a pair of spectral line of mirror image each other to satisfy formula (9) definition between the shown spectral line of frequency spectrograph be the position of spectral line relation, in " multiple response " spectral line, find out " true signal " spectral line, finish that input signal spectrum is got " signal identification " process.

The invention provides a kind of outer mixing mode without the external signal recognition methods of preselector frequency spectrograph, may further comprise the steps:

Outside frequency mixer and external signal mixing forms mixed frequency signal from the harmonic wave of the single order local oscillation signal of frequency spectrograph;

Mixed frequency signal becomes intermediate-freuqncy signal through the intermediate-frequency filter filtering of frequency spectrograph,

Frequency spectrograph shows the multiple response spectral line that described intermediate-freuqncy signal is corresponding;

Gather the frequency data of described multiple response spectral line;

Frequency interval identification external signal according to the collection spectral line.

Preferably, multiple response spectral line corresponding to the described intermediate-freuqncy signal of demonstration occurs in pairs and satisfies following relational expression:

$f_N^{n+}=N_{\±}\·\frac{f_S-f_{\mathrm{IF}}}{n}\±f_{\mathrm{IF}}$

$f_N^{n-}=N_{\±}\·\frac{f_S\text{+}{f}_{\mathrm{IF}}}{n}\±f_{\mathrm{IF}}$

$\mathrm{\Δ}{f}_N^n=f_N^{n-}-f_N^{n+}=\frac{N_{\±}}{n}\·2f_{\mathrm{IF}}$

Wherein, work as n=N ₊The time, $f_S=f_N^{n+}=f_N^{n-}-{2f}_{\mathrm{IF}}$

When n=N-, $f_S=f_N^{n-}=f_N^{n+}+{2f}_{\mathrm{IF}}$

In the formula:

N _±Be the mixed-mode of described frequency spectrograph appointment,

f _SBe the frequency of described external signal,

f _IFBe the centre frequency of described intermediate-frequency filter,

N is the overtone order of described frequency spectrograph single order local oscillation signal,

Be the right frequency interval of shown mirror image spectral line.

Preferably, described frequency interval identification external signal according to the collection spectral line further comprises:

Mixed-mode " N according to the frequency spectrograph appointment ₊" or " N _-", with each spectral line of gathering intermediate-frequency filter centre frequency to 2 times of low frequency or high frequency translations;

The spectral line of translation spectral line and former overlap of spectral lines is identified as the external signal frequency spectrum, obtains the frequency of this external signal.

Preferably, described frequency interval identification external signal according to the collection spectral line further comprises:

Calculate frequency interval between each spectral line and take out the spectral line pair that frequency interval is 2 times of intermediate-frequency filter centre frequencies;

Mixed-mode " N according to the frequency spectrograph appointment ₊" or " N _-", spectral line is identified as the external signal frequency spectrum to low and medium frequency spectral line or high-frequency spectral line, obtain the frequency of this external signal.

Preferably, the step of the frequency data of described collection multiple response spectral line comprises:

The amplitude threshold of spectral line is set;

Select to observe bandwidth to reach frequency measurement accuracy according to the frequency stability of measured signal;

By according to the observation bandwidth of selecting sweep limit segmentation and each section of frequency spectrograph being scanned described multiple response spectral line collection range value greater than the frequency of each spectral line of amplitude threshold with overlapping.

Preferably, described amplitude threshold is set to be higher than more than the frequency spectrograph background noise level 3dB.

Preferably, select to observe bandwidth according to the frequency stability of measured signal, so that the absolute measurement precision of frequency values is at least 0.1MHz.

Preferably, described segmentation and with overlapping scanning comprise:

For " N _-" mixed-mode, the frequency that at least before pushes away 2 times intermediate-frequency filter centre frequency from the initial frequency of sweep limit begins scanning;

For " N ₊" mixed-mode, the frequency of prolonging at least afterwards 2 times intermediate-frequency filter centre frequency to the termination frequency of sweep limit finishes scanning;

With the reach of the starting point of all the other each section scannings observe bandwidth 1/10 so that overlapping scan.

The present invention further provides a kind of outer mixing mode without the preselector frequency spectrograph, comprising:

The local oscillation signal generator is used for output single order local oscillation signal;

Intermediate-frequency filter carries out filtering for the mixed frequency signal that obtains of the harmonic wave that receives the single order local oscillation signal and external signal mixing and to this mixed frequency signal, the multiple response spectrum of output intermediate-freuqncy signal;

Display unit is used for display;

The frequency collection unit is for the frequency that gathers shown multiple response spectral line;

Data processing unit is used for the frequency interval identification external signal according to the collection spectral line.

Preferably, data processing unit is according to the mixed-mode " N of frequency spectrograph appointment ₊" or " N _-", the frequency values of each spectral line of gathering is deducted or add that 2 times intermediate-frequency filter centre frequency obtains the translation frequency of each spectral line frequency, and by relatively translation frequency and former spectral line frequency, frequency identification that the two is equal is the frequency of this external signal.

Preferably, data processing unit calculates difference on the frequency between each spectral line, and extracting difference is the spectral line frequency value of 2 times of intermediate-frequency filter centre frequencies, and according to the mixed-mode " N of frequency spectrograph appointment ₊" or " N _-", spectral line frequency low and medium frequency or high-frequency are identified as the external signal frequency.

Description of drawings

With reference to the accompanying drawings and in conjunction with the embodiments the present invention is specifically described, wherein:

Fig. 1 illustrates according to prior art Spectrum Analyzer System schematic diagram;

Fig. 2 illustrates the principle of work schematic diagram of Spectrum Analyzer System shown in Figure 1;

Fig. 3 is the schematic diagram of the Spectrum Analyzer System of the preferred embodiment of the present invention;

Fig. 4 illustrates the workflow diagram according to Spectrum Analyzer System of the present invention;

Fig. 5 illustrates the process flow diagram according to the collecting method of spectral frequencies of the present invention and amplitude;

Fig. 6 is that the used signal source of the example according to the present invention is in the situation of 6600A/1 of MARCONI company, when its output signal is 80GHz, computer acquisition to the spectrum analyzer display screen on whole spectrums;

Fig. 7 is that the used signal source of the example according to the present invention is in the situation of 6600A/1 of MARCONI company, when its output signal is 80GHz, utilizes the present invention that its frequency spectrum is analyzed and the net result figure that identifies " true signal " spectral line that obtains;

Fig. 8 is the frequency data table of " true signal " spectral line among all spectral lines and Fig. 7 among Fig. 6;

Fig. 9 is hypothesis input signal when being the 80GHz continuous wave, the spectral line data table of being derived and being obtained by theory.

Embodiment

Present invention is described in conjunction with the preferred embodiments below with reference to accompanying drawings.

Fig. 3 shows the according to the preferred embodiment of the invention schematic diagram of Spectrum Analyzer System.Spectrum Analyzer System 100 according to the present invention comprises without preliminary election frequency mixer 102, frequency spectrograph 103 and data processing equipment 104.Data processing equipment 104 further comprises frequency and amplitude collecting unit 105 and processing unit 106.Fig. 4 shows the workflow diagram according to Spectrum Analyzer System of the present invention.The method of Spectrum Analyzer System analysis external signal frequency may further comprise the steps according to the preferred embodiment of the invention:

Step 401: the harmonic wave of the local oscillation signal of frequency spectrograph and external signal mixing.

Outside frequency mixer and external signal mixing forms mixed frequency signal from the harmonic wave of the single order local oscillation signal of frequency spectrograph.

Step 402: mixed frequency signal is through the intermediate-frequency filter filtering of frequency spectrograph.

Mixed frequency signal becomes intermediate-freuqncy signal through intermediate-frequency filter filtering.The multiple response spectral line that satisfies formula (6) is presented on the display of frequency spectrograph.

Step 403: the spectral frequencies and the range value that gather the response spectral line

In the situation that without preselector, from the input signal f of signal source 101 _SThrough outside frequency mixer 102 and single order local oscillation signal f from frequency spectrograph 103 _LOHarmonic mixing after obtain mixed frequency signal f _H, this mixed frequency signal f _HThrough becoming intermediate-freuqncy signal f after the intermediate-frequency filter filtering in the frequency spectrograph 103 _IFFor selected frequency spectrograph, the response spectral line that satisfies formula (6-1) and formula (6-2) frequency can be presented on the display screen of frequency spectrograph.At first to record collection to these spectral lines that frequency spectrograph shows.Frequency and amplitude harvester 105 are by for example gpib interface collecting test data of frequency spectrograph 103.When usually observing in full frequency band, for example the W wave band is 75GHz-110GHz, and it is very rough observing the spectral line frequency value that spectral line reads, the relation between can not the Accurate Analysis spectral line.While, spectral line was very mixed and disorderly numerous, might not all be real response, and picking rate is very slow owing to the amplitude of normally pressing gathers.But determine that accurately the frequency of spectral line and amplitude are the bases of carrying out signal identification, the frequency and the amplitude that gather roughly spectral line can make signal identification subsequently carry out.

Describe the according to the preferred embodiment of the invention collecting method of spectral frequencies and amplitude below with reference to Fig. 5, the method comprises:

Step 501: the threshold value of collection spectral line amplitude is set with the shielding noise.

The threshold value that set to gather the spectral line amplitude is accurately to gather a kind of uniqueness of the frequency of spectral line and amplitude and effective method.The method can make response less on the display screen and the random noise bounce that occurs ignore, and because having eliminated measuring speed has also been accelerated in the collection of low amplitude response simultaneously.The principle of threshold value setting is with reference to background noise level and some spuious or unsettled small response levels of observing in the frequency range, gets the numerical value a little more than them, more than the preferred high 3dB.Preferably, if the power level of " true signal " spectral line below threshold value, can be carried out mixed frequency signal after the power amplification again input spectrum instrument.Should be appreciated that those skilled in the art can adjust the amplitude threshold that gathers spectral line flexibly according to observation and the last test result of actual conditions.During embodiment described in detail in the back, amplitude threshold was set as-60dBm.

Step 502: choose suitable observation bandwidth according to measuring accuracy.

As mentioned above, mainly utilized position relationship between the spectral line according to signal recognition method of the present invention, i.e. frequency interval is so must accurately measure the frequency values of spectral line.The method according to this invention, frequency values preferably are accurate to 0.1MHz.The frequency accuracy that shows spectral line on the frequency spectrograph screen and observation bandwidth are that the frequency range that shows on the screen is relevant.When for example observing in the Whole frequency band of W wave band, the precision of spectral line display frequency is 10MHz, is reduced to below the 1GHz when observation band is wide, and the precision of spectral line display frequency just can reach 0.1MHz.Two factors that condition each other are depended in the setting of observing bandwidth: the one, for reaching above-mentioned requirements, must suitably reduce to observe bandwidth, and in a narrower frequency range, read the frequency values of every spectral line; The 2nd, can not make the observation bandwidth too narrow according to analyzed signal frequency stability situation, can not make every spectral line show as the bell-shaped pulse pattern, and should keep the shape of wall scroll fine rule.For example, at first judge the frequency stability of signal.Choose that any spectral line frequency is as centre frequency on the frequency spectrograph screen, bandwidth is made as 1GHz, observes whether fine rule of spectral line this moment.If width and the edge of the obvious more than fine rule of this spectral line are jagged, the frequency stability that signal is described is low, observing the broadband can be set to greater than 2GHz, general desirable 4～5GHz will open the accurate measurement switch (FREQ COUNT) of frequency spectrograph this moment for the precision that satisfies spectral line frequency reading 0.1MHz; If spectral line is a fine rule, illustrate that the frequency stability of signal is high, then select this moment little span to measure, observing the broadband can be less than or equal to 1GHz, and needn't open the accurate measurement switch this moment.

Step 503: segmentation and with overlapping the described multiple response spectral line of scanning gather range value greater than the frequency values of each spectral line of amplitude threshold.

After setting observation bandwidth and amplitude threshold, can from the low frequency to the high-frequency, scan piecemeal to search for spectral line in whole sweep limit.To observe bandwidth end to end be not all right but just make every section, because when observing bandwidth hour, spectral line just drops on the edge and is missed sometimes.In addition, if analyzed signal can foreclose its image signal very near the initial frequency of sweep limit.Therefore, the preferred scanning step of the present invention further comprises: at first, with the initial frequency of sweep limit must before push away certain numerical value, prolong certain numerical value after the termination frequency with sweep limit simultaneously.Generally speaking, front pushing volume and after the amount of prolonging should be not less than 2 times of frequency spectrograph intermediate-frequency bandwidth; Secondly, when scanning piecemeal, all to make to push away before the starting point of rear one section search a bit ofly, that is to say that rear one section is wanted overlapping the last period of sub-fraction.Generally speaking, front pushing volume is about 1/10 of this observation bandwidth.

Thus, obtain frequency values and the range value of each bar spectral line.

Step 404: according to the frequency interval identification external signal of collection spectral line.

The front mentions the situation that can occur multiple response when the frequency spectrograph that adopts the outer mixing without preselector is measured the frequency spectrum of input signal, and often in pairs appearance of spectral line.Frequency interval between the spectral line of these " each other mirror images " that occur in pairs satisfies formula (9) so.Only having as can be known the frequency interval between " true signal " and its " mirror image " by formula (9) is 2f _IFIn other words, in the collection spectral line, satisfying frequency interval is 2f _IFTwo spectral lines in must have spectral line to characterize the frequency of " true signal ".

After this constitutive relations that has disclosed between spectral line, the concrete scheme of the signal identification that the present invention proposes has two:

Scheme one, step 404A: when frequency spectrograph when the mixed-mode of this frequency range spot frequency appointment is " N-", with all spectral line frequency integral body of collecting to high-end translation 2f _IFWhen frequency spectrograph is " N in the mixed-mode of this frequency range spot frequency appointment ₊" time, with all spectral line frequency integral body of collecting to low side translation 2f _IF, then the spectral line frequency value before and after the translation being compared, that spectral line that frequency overlaps namely is " true signal " spectral line.

Scheme 2, step 404B: calculating the spacing of " mirror image to " spectral line, find wherein that the interval is the spectral line of twice intermediate frequency, is " N according to frequency spectrograph in the mixed-mode of this frequency range spot frequency appointment ₊" or " N _-", and then low still that the high spectral line of frequency of determination frequency is " true signal " spectral line.

Below, the signal that will send take two kinds of different signal sources of frequency stability carries out spectrum analysis and signal identification as example.The result shows, the spectral line collection is correct, and signal identification is accurately measured with identification and can be finished in a short period of time.

Example 1

The frequency spectrograph test macro of example 1 comprises according to the present invention: signal source 101 is the 6600A/1 of MARCONI company; Frequency mixer 102 is the AV1271X series that the 41st research institute of China Electronic Science and Technology Corporation produces, and is AV12719 in the model of the used mixing instrument of W wave band; The 8563E type frequency spectrograph that selected spectrum analyzer 103 is Hewlett-Packard Corporation; Frequency and amplitude collecting unit 105 comprise Agilent 82357B type USB-GPIB interface card.

At first spectrum analyzer is carried out initialization, comprise the selection of wave band, the selection of measurement pattern and the setting of amplitude threshold.Main Basis is the observation bandwidth selected when measuring and the size of the frequency spectrograph background noise under the resolution bandwidth during selecting range threshold value.Background noise power level mxm. approximately is-65dBm in this example, threshold value is made as-60dBm, this means to require input signal should be not less than-60dBm through the power after the mixing.The conversion loss of frequency mixer AV12719 is about 46dB, so the power of input signal can not be too little.In order accurately to measure the frequency values of spectral line, frequency values preferably is accurate to 0.1MHz.Measurement pattern is divided into large span and little span dual mode, the width of the observation bandwidth of choosing when they represent areal survey respectively for the frequency stability of analyzed signal.Because the frequency stability of different signal sources is different, the poor signal source spectral line in narrow observation bandwidth of frequency stability will broaden even become bell, so that can capture a plurality of frequencies and be not easy to survey accurate, therefore will select the measurement pattern of " large span ".But observe bandwidth when too wide, the precision that reads of peak point frequency reduces, and cursor easily two each other the spectral line of " mirror image " be read as same frequency values.Therefore preferably, observe the bandwidth maximum for the sort signal source and be not more than 10GHz.The used signal source of the present embodiment namely belongs to the poor source of this frequency stability, and its frequency stability is about 10 ^-4Magnitude.Therefore, selecting 4GHz in A, Q-band in the present embodiment, selecting 5GHz more than the W wave band is that bandwidth is observed in segmentation.Under the measurement pattern of large span, to open the meticulous measuring switch of frequency spectrograph for guaranteeing the precision of measuring.The signal source that frequency stability is high is selected " little span ", and this moment, Measurement bandwidth was 500MHz.

Initialization is measured after finishing, with the sine wave signal f of signal source 101 generations _SSend into the frequency mixer 102 without preselector, the higher hamonic wave mixing of signal and local oscillator in frequency mixer, the intermediate-freuqncy signal after the mixing is sent spectrum analyzer HP8563E again back to, can obtain one group of spectral line on the display screen of frequency spectrograph.Measure piecemeal according to the Measurement bandwidth segmentation that chooses, utilize the function of cursor to seek the spectral line that is higher than threshold value, the spectral line frequency value that collects and range value are given array and are arranged from small to large according to frequency values.All spectral line frequency collections finish laggard line number and process: adopt aforementioned signal identifying schemes, namely all spectral line frequencies in the array are added that 2 times of intermediate frequencies deposit new array, each numerical value in the new array and the original interior value of array are compared.If exist the difference of two numbers less than predetermined value, 5MHz for example just thinks two number approximately equals, and the numerical value that belongs to so former array in this two number is exactly the frequency values of " true signal " spectral line.By mapping and listing function the result that described frequency interval calculates is shown, such as Fig. 6, Fig. 7 and shown in Figure 8 in the accompanying drawing.For example, when below adopting during each model instrument configuration described in the example 1, if the analyzed signal source for example is the nominal output frequency of low frequency degree of stability when being the signal source of 80GHz continuous wave, it will produce a series of spectral lines at frequency spectrograph, wherein only have a spectral line representative " true signal ".The result who measures is, in 75～110GHz of tested W wave band frequency range, collects altogether 12 spectral lines, and " true signal " spectral line that identifies is 80.009GHz.Fig. 6 be computer acquisition to frequency spectrograph on shown spectrum, Fig. 7 is " true signal " spectrum that utilizes the present invention to identify, all measurement data are seen accompanying drawing 8.

In fact, the formula that utilizes the present invention to provide can calculate the numerical value of these spectral lines theoretically:

In the present embodiment, the sweep limit of the local oscillator of the outer frequency mixer regulation of frequency spectrograph W wave band is 4.15GHz～6.09GHz, according to mixing formula (1) as can be known:

$n=\frac{(f_S\±f_{\mathrm{IF}})}{f_{\mathrm{LO}}}---\left(10\right)$

Suppose f _LOLRepresent minimum local frequency, f _LOHThe highest local frequency of expression, because

(f _S-f _IF)/f _LOH＝(80-0.3107)/6.09＝13.085 (11)

(f _S+f _IF)/f _LOL＝(80+0.3107)/4.15＝19.352 (12)

Can obtain the local oscillator overtone order scope (n with the signal mixing _Min～n _Max) be 13～19, N is 18 in the embodiment of the invention, specifying mixed-mode is " 18 _-So " by formula (6-1) and (6-2) can calculate the spectral line frequency value that may occur on the frequency spectrograph as shown in Figure 9; comparison diagram 8 and Fig. 9; can find out that spectral line and theoretical analysis that actual measurement obtains are in full accord, minute differences between the two are due to the measuring error.Thus, prove again theory that the present invention provides and the correctness of embodiment.

In addition, in the present embodiment, also make nominal output frequency in analyzed signal source change to respectively 90GHz, 100GHz, 105GHz continuous wave, can both from the multiple response spectral line, accurately identify quickly and easily real signal spectrum.

This shows that the technical scheme that implementation the present invention is given has proved correctness and the validity of its theory and practice fully.

Should be appreciated that the embodiments described herein is illustrative and not restrictive.Those skilled in the art can have a better understanding to technical scheme of the present invention, and can carry out various modifications and variations to embodiments of the invention under spirit of the present invention and aim by reading instructions.Protection scope of the present invention is only limited by the claims of enclosing.

Claims (6)

1. an outer mixing mode may further comprise the steps without the external signal recognition methods of preselector frequency spectrograph:

Outside frequency mixer and external signal mixing forms mixed frequency signal from the harmonic wave of the single order local oscillation signal of frequency spectrograph;

Mixed frequency signal becomes intermediate-freuqncy signal through the intermediate-frequency filter filtering of frequency spectrograph,

Frequency spectrograph shows the multiple response spectral line that described intermediate-freuqncy signal is corresponding;

Gather the frequency data of described multiple response spectral line;

According to the frequency interval identification external signal of collection spectral line,

Multiple response spectral line corresponding to described intermediate-freuqncy signal that shows occurs in pairs, and the frequency of the mirror image spectral line centering spectral line of demonstration satisfies following relational expression:

$f_N^{n+}=N_{\±}\·\frac{f_S-f_{\mathrm{IF}}}{n}\±f_{\mathrm{IF}}$

$f_N^{n-}=N_{\±}\·\frac{f_S+f_{\mathrm{IF}}}{n}\±f_{\mathrm{IF}}$

${\mathrm{\Δf}}_N^n=f_N^{n-}-f_N^{n+}=\frac{N_{\±}}{n}\·{2f}_{\mathrm{IF}}$

Wherein, work as n=N ₊The time, $f_S=f_N^{n+}=f_N^{n-}-{2f}_{\mathrm{IF}}$

When n=N-, $f_S=f_N^{n-}=f_N^{n+}+{2f}_{\mathrm{IF}}$

In the formula:

N _±Be the mixed-mode of described frequency spectrograph appointment,

f _SBe the frequency of described external signal,

f _IFBe the centre frequency of described intermediate-frequency filter,

N is the overtone order of described frequency spectrograph single order local oscillation signal,

Be the right frequency interval of shown mirror image spectral line,

It is characterized in that, described frequency interval identification external signal according to the collection spectral line further comprises:

Mixed-mode " N according to the frequency spectrograph appointment ₊" or " N _-", with each spectral line of gathering intermediate-frequency filter centre frequency to 2 times of low frequency or high frequency translations;

The spectral line of translation spectral line and former overlap of spectral lines is identified as the external signal frequency spectrum, obtains the frequency of this external signal.

2. outer mixing mode according to claim 1 is characterized in that without the external signal recognition methods of preselector frequency spectrograph, and the step of the frequency data of described collection multiple response spectral line comprises:

The amplitude threshold of spectral line is set;

Select to observe bandwidth to reach frequency measurement accuracy according to the frequency stability of measured signal;

By according to the observation bandwidth of selecting sweep limit segmentation and each section of frequency spectrograph being scanned described multiple response spectral line collection range value greater than the frequency of each spectral line of amplitude threshold with overlapping.

3. according to claim 2 method is characterized in that, described amplitude threshold is set to be higher than more than the frequency spectrograph background noise level 3dB.

4. according to claim 2 method is characterized in that, selects to observe bandwidth according to the frequency stability of measured signal, so that the absolute measurement precision of frequency values is at least 0.1MHz.

5. according to claim 2 method is characterized in that, described segmentation and with overlapping scanning comprise:

For " N _-" mixed-mode, the frequency that at least before pushes away 2 times intermediate-frequency filter centre frequency from the initial frequency of sweep limit begins scanning;

For " N ₊" mixed-mode, the frequency of prolonging at least afterwards 2 times intermediate-frequency filter centre frequency to the termination frequency of sweep limit finishes scanning;

With the reach of the starting point of all the other each section scannings observe bandwidth 1/10 so that overlapping scan.

6. an outer mixing mode comprises without the preselector frequency spectrograph:

The local oscillation signal generator is used for output single order local oscillation signal;

Intermediate-frequency filter carries out filtering for the mixed frequency signal that obtains of the harmonic wave that receives the single order local oscillation signal and external signal mixing and to this mixed frequency signal, the multiple response spectrum of output intermediate-freuqncy signal;

Display unit is used for display;

The frequency collection unit is for the frequency that gathers shown multiple response spectral line;

Data processing unit is used for the frequency interval identification external signal according to the collection spectral line,

It is characterized in that, data processing unit is according to the mixed-mode " N of frequency spectrograph appointment ₊" or " N _-", the frequency values of each spectral line of gathering is deducted or add that 2 times intermediate-frequency filter centre frequency obtains the translation frequency of each spectral line frequency, and by relatively translation frequency and former spectral line frequency, frequency identification that the two is equal is the frequency of this external signal.

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