CN101350629B - Method for predicting latent scrambling frequency band of receiver RF system - Google Patents

Abstract

The present invention discloses a potential interfered band predicting method of the radio frequency system of receiver, and comprises the following steps: 1) searching the ''wave packet'' with a fluctuating curve in the whole frequency selection curve of the radio frequency system of receiver, or the section which is not ideal in a certain range of frequency band; 2) finding the sub-circuit module corresponding to the frequency band which is not ideal in the system, according to the corresponding correlation between the whole frequency selection curve of the radio frequency system of the receiver and the frequency selection characteristic curve of the internal sub-circuit module; 3) analyzing the frequency band of the sub-circuit module and the combination-interference frequency band of vibration signals, and finding the interfered frequency band, so as to provide criteria for the optimization of the whole frequency selectivity. The method can be used for analyzing the interference problem with the unknown condition in the radio frequency system of the receiver, therefore, the method can provide optimization guide for the problem diagnosis of electromagnetic interference and the strengthening of electromagnetic compatibility of the completed system of the receiver, and can also provide optimization guide for the design of the receiver.

Description

The Forecasting Methodology of the potential disturbed frequency band of receiver RF system

Technical field

The present invention relates to a kind of in complex electromagnetic environment the Forecasting Methodology of the potential disturbed frequency band of receiver RF system, belong to the electromagnetic compatibility technology field.

Background technology

At present, radio frequency environment is abominable day by day, particularly is placed in the receiver in the cabin that numerous electronic equipments are housed that composite material constitutes, and emc issue is very obvious.General receiver is made up of reception antenna, radio system and base band demodulating system, and the frequency of radio system selects characteristic directly to influence the ability of receiver processing signals, will guarantee that at last demodulating system can proper solution access required baseband signal.The defective of superheterodyne technology is in the process of mixing, to have produced unnecessary spurious response; Simultaneously; Local oscillation signal has the heavy injection effect of pair transmitted signal energy; Thereby stronger with the signal power of local oscillation signal combination, disturbed the reception of useful signal, this phenomenon of broadband receiver is then more serious.

The potential disturbed frequency band of analyses and prediction receiver is very important, and the interference signal that can let other jamming equipment produce is on the one hand avoided these frequency bands as far as possible; On the other hand, according to the electronic circuit module that the corresponding meeting of receiver system overall performance analysis goes wrong, instruct these electronic circuit module frequencies are optionally optimized to realize the global optimization of receiving system.

Summary of the invention

The purpose of this invention is to provide a kind of in complex electromagnetic environment the Forecasting Methodology of the potential disturbed frequency band of receiver RF system; Specifically; Be that a kind of whole frequently to select characteristic curve be the starting point with receiver RF system; Utilize entire system to select the method for the disturbed frequency band of associated in correspondence Relationship Prediction of characteristic curve and each electronic circuit module selectivity curve frequently, can be superheterodyne receiver, particularly the receiver optimization of broader bandwidth provides guide.

For addressing the above problem, the present invention adopts following technical scheme:

The Forecasting Methodology of the potential disturbed frequency band of a kind of receiver RF system may further comprise the steps:

1) seeks " ripple bag " or undesirable section in some frequency band range that occurs the curve fluctuating in the receiver RF system overall frequency selectivity curve;

2) select characteristic curve associated in correspondence relation frequently according to receiver RF system overall frequency selectivity curve and inner electronic circuit module, find and the corresponding electronic circuit module of the undesirable frequency band of system;

3) analyze the frequency band of this electronic circuit module, find disturbed frequency band, thereby foundation is provided for the optimization of entire system frequency selectivity.

Further:

In said step 2) in, the combination interference frequency band with local oscillation signal also will be analyzed, to find potential disturbed frequency band.

In said step 2) in, the foundation that receiver RF system overall frequency selectivity curve and inner electronic circuit module frequency selectivity curve incidence relation are judged is: frequency mixer is to the last down-conversion mode of signal, and the frequency of signal is behind the process frequency mixer: | f _LO± f _i|, f wherein _LOBe local oscillation signal frequency, f _iFor another frequency input signal of frequency mixer, in case f _iBefore be negative sign, then the filter frequencies selectivity curve behind this frequency mixer can be that left and right sides sideband exchange appears in the boundary with the centre frequency when contribution receiving system overall frequency selectivity.

The analysis emphasis of combination interference is signal and the combination with more superpower local oscillation signal, considers the non-linear of radio system, and analysis is that its input-output characteristic is used power series expansion with the method for the combination interference frequency band of local oscillation signal.

The invention has the advantages that:

1. because the frequency selectivity curve of analysis receiver radio system on the whole; Utilize the associated in correspondence relation of radio system and inner electronic circuit module; The locator module frequency is optionally potential undesirable section fast, thereby has simplified the complicated process of analyzing the electronic circuit module one by one;

2. owing to during the potential disturbed frequency band of prediction, also considered the heavily injection of local oscillation signal to energy, the proposition of therefore as far as possible avoiding these disturbed frequency bands and anti-interference scheme for receiver system in the design phase provides analyzes foundation more all sidedly;

3. because can be under the inner condition of unknown of receiver RF system; Analyze disturbed problem; Therefore can reinforcing provide the optimization guide with electromagnetic compatibility for completed receiver system electromagnetic interference problem diagnosis, also can be used as the optimization guide of receiver design phase.

Description of drawings

Fig. 1 is the structured flowchart of the potential disturbed frequency band prediction of radio system;

Fig. 2 is that the frequency that has undesirable section of ripple bag and the gradient of fluctuating selects characteristic curve;

Fig. 3 is a second order superheterodyne receiver radio system block diagram;

Fig. 4 is the corresponding upset situation of selectivity after the mixing (f in formula (1), (2) _RF, f _IF1Before all be negative sign);

Fig. 5 is the sketch map of receiver RF system selectivity curve emersion wave bag;

Fig. 6 is receiver RF system frequency selectivity curve before submodule is optimized, and ordinate dB (S (2,1)) is that the gain of S (2,1) is represented, abscissa is a frequency, and unit is MHz;

Fig. 7 is for being optimized back receiver RF system frequency selectivity curve to submodule, ordinate dB (S (2,1)) is that the gain of S (2,1) is represented, abscissa is a frequency, and unit is MHz.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is described further.

The present invention be a kind of in complex electromagnetic environment the Forecasting Methodology of the potential disturbed frequency band of receiver RF system, idiographic flow is as shown in Figure 1, comprises following analytical procedure:

(1) analysis receiver radio system overall frequency selectivity curve.With input radio frequency signal (RF signal) is starting point, and signal through gain (dB) expression formula after the whole radio system is:

G _total＝G _f1+G _f2+G _f3+…+G _fn+G _e

G _TotalBe system's overall gain, G _Fn(n=1,2 ...) be the gain (can be negative value) of filters at different levels, G _eOverall gain for other module such as amplifier, frequency mixer.G _FnValue at some band attenuation hour, G _TotalIn the corresponding increase of these frequency bands meetings; " the ripple bag " of fluctuating or the descending grade in some frequency band range relatively slowly (like Fig. 2) often appear; Particularly outstanding for this phenomenon of broadband receiver, the jam-to-signal of correlated frequency is easier to get into receiving system in complex electromagnetic environment.

(2) confirm entire system frequency selectivity curve and main filtration module frequency selectivity curve associated in correspondence relation.With the centre frequency is the boundary; In different received machine radio system structure; The left and right sideband of entire system frequency selectivity curve is different with the corresponding situation of each filtration module frequency selectivity curve right sides frequency band, and each frequency mixer all may change the right sides frequency band corresponding relation of submodule and entire system frequency selectivity curve.

In order to be easier to explain this corresponding relation, be example with a common second order superheterodyne receiver, radio system block diagram such as Fig. 3.Radio frequency (RF) signal gets into behind the LNA through first order filtering, gets into filtering and amplification behind first frequency mixer then, gets into filtering behind second frequency mixer, amplification again, obtains intermediate-freuqncy signal output at last.

Wherein, frequency input signal is f _RF, the first local oscillation signal frequency is f _LO1, the second local oscillation signal frequency is f _LO2, the first intermediate-freuqncy signal frequency is f _IF1, the second intermediate-freuqncy signal frequency is f _IF2Relation between these frequencies is (can not get negative sign simultaneously):

f _IF1＝±f _LO1±f _RF(1)

f _IF2＝±f _LO2±f _IF1(2)

F when (1) formula _RFBefore when being negative sign; IF1 filter frequencies selectivity is when finally contributing receiver RF system overall frequency selectivity among Fig. 3; Can be that left and right sides sideband exchange appears in the boundary with the centre frequency; That is to say that this moment, electronic circuit module selectivity left side frequency bandwidth characteristics can reflect the characteristic of the whole selectivity of radio system the right frequency band, the left frequency band of the whole selectivity curve of the right corresponding radio system of frequency band meeting of the selectivity curve of electronic circuit module.Likewise, f in (2) formula _IF1Before when be negative sign, IF2 filter frequencies selectivity curve relative centre frequency on corresponding radio system selectivity curve also once inside out can occur.Fig. 4 has explained the upset of two frequency mixers to this corresponding relation.

In the superheterodyne receiver structure of different rank, radio system overall frequency selectivity also can be different with inner electronic circuit module selectivity corresponding relation, and this analytic process is fit to any superheterodyne receiver radio system simultaneously.

(3) prediction of potential disturbed frequency band: when radio system frequency selectivity curve occurs undesirable section (" ripple bag " or the slow frequency band of decaying); In conjunction with the associated in correspondence relation of system that analyzes in (2) and electronic circuit module frequency selectivity curve, the combination interference frequency band of consideration and more superpower local oscillation signal is with the potential disturbed frequency band of prediction receiver simultaneously.

Because radio system is non-linear, therefore when the combination interference frequency band was analyzed, its input-output characteristic was used power series expansion:

$u_o=\underset{n=1}{\overset{\∞}{\mathrm{\Σ}}}{a}_n{u}_i^n=a_1{u}_i+a_2{u}_i^2+a_3{u}_i^3\·\·\·+a_n{u}_i^n$

a _nBe each item coefficient.

If u _i=u _I1+ u _I2=V ₁Cos ω ₁T+V ₂Cos ω ₂T, then

$u_0=a_1(V_1\cos {\mathrm{\ω}}_{1}t+V_2\cos {\mathrm{\ω}}_{2}t)$

$+\frac{1}{2}{a}_2\{[V_1^2+V_2^2+V_1^2\cos 2{\mathrm{\ω}}_{1}t+V_2^2\cos 2{\mathrm{\ω}}_{2}t]+2V_1{V}_2[\cos ({\mathrm{\ω}}_1+{\mathrm{\ω}}_2)t+\cos ({\mathrm{\ω}}_1-{\mathrm{\ω}}_2)t]\}$

$\left.\begin{array}{c}+\frac{1}{4}{a}_3\{V_1^3\cos 3{\mathrm{\ω}}_{1}t+V_2^3\cos 3{\mathrm{\ω}}_{2}t+3V_1^2{V}_2[\cos (2{\mathrm{\ω}}_1+{\mathrm{\ω}}_2)t+\cos (2{\mathrm{\ω}}_1-{\mathrm{\ω}}_2)t]\\ +3V_1{V}_2^2[\cos (2{\mathrm{\ω}}_2+{\mathrm{\ω}}_1)t+\cos (2{\mathrm{\ω}}_2-{\mathrm{\ω}}_1)t]\\ +3(V_1^3+2V_1{V}_2^2)\cos {\mathrm{\ω}}_{1}t+3(V_2^3+2V_1^2{V}_2)\cos {\mathrm{\ω}}_{2}t\}\end{array}\right\}$

+...

Can find out that by following formula when double frequency was imported, the composition of output was by DC component, fundamental frequency omega ₁And ω ₂, secondary and triple-frequency harmonics 2 ω ₁, 2 ω ₂, 3 ω ₁And 3 ω ₂, second order inter-modulation component ω ₁± ω ₂, third order intermodulation 2 ω ₁± ω ₂, 2 ω ₂± ω ₁Aliquot is formed, and being write as general type is m ω ₁± n ω ₂(m, n=0,1,2 ...) be called the combination frequency component.

Still be example with second order superheterodyne receiver shown in Figure 3, suppose to occur " ripple bag " in the radio system selectivity curve that frequency band is f ₁～f ₂, like Fig. 5.Notice that the center of overall frequency selectivity curve is final intermediate frequency output frequency among the figure.The centre frequency of the overall frequency selectivity curve that usually, analyzes all is radio frequency incoming frequency (f _RF), so need do conversion according to the process of mixing, the overall frequency selectivity curve that to obtain with final intermediate frequency output frequency be the center.

The centre frequency of noting this curve is f _IF2, that is to say with f _IF2Be the radio system overall frequency selectivity curve that centre frequency draws, then predict that from Fig. 5 potential disturbed frequency band is:

(A) f ₁～f ₂, this frequency band can only be coupled into after the IF2 filter in the filtering effectively of quilt in early stage usually;

(B) | f _LO1-f ₂|～| f _LO1-f ₁| and | f _LO1+ f ₁|～| f _LO1+ f ₂|, this band signal and first local frequency are combined into f ₁～f ₂, but also easily by IF1 filter and the filtering of IF2 filter;

(C) | f _LO2-f ₂|～| f _LO2-f ₁| and | f _LO2+ f ₁|～| f _LO2+ f ₂|, this band signal and the combination of second local frequency can get into to form after the IF1 filter and disturb;

(D)|f _LO1-f ₂-f _LO2|～|f _LO1-f ₁-f _LO2|，|f _LO1+f ₂+f _LO2|～|f _LO1+f ₁+f _LO2|，

| f _LO1+ | f ₂-f _LO2||～| f _LO1+ | f ₁-f _LO2|| and | f _LO1-| f ₂-f _LO2||～| f _LO1-| f ₁-f _LO2||, these band signals and the combination of first and second local oscillators get into receiving system easily.

(B)～(D) formula all be since in the non-linear and optical mixing process of superheterodyne receiver unnecessary spurious response cause.Local oscillation signal has the heavy injection effect of pair interference signal energy, and local oscillation signal power is stronger, and its harmonic wave can not be ignored, particularly for broadband receiver, so also will consider following frequency band:

(E) | mf _LO1-f ₂|～| mf _LO1-f ₁| and | mf _LO1+ f ₁|～| mf _LO1+ f ₂|, m gets 2,3,4 ...;

(F) | nf _LO2-f ₂|～| nf _LO2-f ₁| and | nf _LO2+ f ₁|～| nf _LO2+ f ₂|, n gets 2,3,4 ...;

(G)|mf _LO1-f ₂-nf _LO2|～|mf _LO1-f ₁-nf _LO2|，

|mf _LO1+f ₂+nf _LO2|～|mf _LO1+f ₁+nf _LO2|，

|mf _LO1+|f ₂-nf _LO2||～|mf _LO1+|f ₁-nf _LO2||，

| mf _LO1-| f ₂-nf _LO2||～| mf _LO1-| f ₁-nf _LO2||, m, n get 2,3,4 ...;

Can find out from (A)～(G), comprise all situation, have after the merging when m, n get (G) at 0,1 o'clock:

(H)|mf _LO1-f ₂-nf _LO2|～|mf _LO1-f ₁-nf _LO2|，

|mf _LO1+f ₂+nf _LO2|～|mf _LO1+f ₁+nf _LO2|，

|mf _LO1+|f ₂-nf _LO2||～|mf _LO1+|f ₁-nf _LO2||，

| mf _LO1-| f ₂-nf _LO2||～| mf _LO1-| f ₁-nf _LO2||, m, n get 0,1,2,3,4 ...;

(H) formula is exactly the potential disturbed frequency band of receiver.General m, n value consider that 5 is just enough.The forecasting process of following formula is fit to single order and three rank superheterodyne receivers equally, and the local oscillator item that just will add is different.

Can effectively instruct the optimization of radio system frequency selectivity according to the potential disturbed frequency band of entire system frequency selectivity curve prediction.The system that utilization analyzes and the frequency of submodule select characteristic associated in correspondence relation, optimize submodule one by one, do not need in this process can do analysis to the frequency selectivity of whole submodule, as long as consider corresponding associated frequency band.For example, the frequency band f in (A) above-mentioned ₁～f ₂, usually, it is very big to decay after the signal of this frequency band process prime bandpass filtering, IF1 filtering and the IF2 filtering, can not also can produce interference through after the radio system.If but test truly has the interference signal of this frequency band, this interference signal should be that the module after the IF2 filter gets into, and need in the module after the IF2 filter, measures such as cable enforcement filtering, shielding eliminate interference.

In addition; Signal in the complex electromagnetic environment tends to produce strong third order intermodulation signal through after the receiving system; This signal is near the centre frequency that receives signal, and the existence of " ripple bag " makes the third order intermodulation signal can not get well decay inhibition, from receiver RF system overall frequency selectivity; Frequency band to " ripple bag " corresponding submodule is optimized one by one, realizes optionally global optimization of system frequency.

Below with the application of an instance explanation the inventive method in certain radio station receiver RF system Anti-Jamming Technique.

The theory diagram of certain radio station receiver RF system such as Fig. 3.The receiving center frequency is 86MHz (a RF signal), and the reception bandwidth is 85.081～86.019MHz.The first local oscillation signal frequency is 938.466MHz, and the second local oscillation signal frequency is 836.76MHz.Signal during through first mixing frequency relation be:

f _IF1＝f _LO1-f _RF

Frequency relation is during through second mixing:

f _IF2＝-f _LO2+f _IF1＝f _LO1-f _RF-f _LO2

So first intermediate frequency (IF1) frequency is 852.466MHz, second intermediate frequency (IF2) frequency is 15.706MHz.The centre frequency of three filters is 86MHz, 852.466MHz, 15.706MHz.

Analysis receiver radio system S (2; 1) with the variation of frequency; Represent with dB; Result to receiving after the unit frequency selectivity is analyzed is as shown in Figure 6: near 85.971MHz～85.975MHz, have one little " ripple bag " among the figure, the frequency range of corresponding final intermediate frequency output is that 15.731MHz～15.735MHz (also is f ₁=15.731MHz, f ₂=15.735MHz).The gain of whole radio system (dB) expression formula is:

G _total＝G _f1+G _f2+G _f3+…+G _fn+G _e

Can know G by the associated in correspondence Analysis of Relationship _F1, G _F2, G _F3Decay in this frequency band scope all maybe be undesirable: the undesirable or selectivity curve of the left side frequency band of first filter is to left, and the undesirable or selectivity curve of second and third filter the right frequency band is to right translation.

In the electromagnetic environment of reality, there is the broadband connections machine of 1.795GHz, in the residing cabin, radio station, there is the electronic equipment of a large amount of 42.725MHz crystal oscillators simultaneously, radiation is stronger.

To the formula of having discussed out above utilizing after this ripple bag analysis (H):

|mf _LO1-f ₂-nf _LO2|～|mf _LO1-f ₁-nf _LO2|，

|mf _LO1+f ₂+nf _LO2|～|mf _LO1+f ₁+nf _LO2|，

|mf _LO1+|f ₂-nf _LO2||～|mf _LO1+|f ₁-nf _LO2||，

| mf _LO1-| f ₂-nf _LO2||～| mf _LO1-| f ₁-nf _LO2||, m, n get 0,1,2,3,4 ...;

1.795GHz drop on | f _LO1+ f ₂+ f _LO2|～| f _LO1+ f ₁+ f _LO2| near, the second harmonic of 42.725MHz crystal oscillator (85.45MHz) drops on | f _LO1-f ₂-f _LO2|～| f _LO1-f ₁-f _LO2| near, interfering signal power causes interference to normal signal when strong easily.

Can be to the left side frequency band of first filter, second and third filter the right frequency band is analyzed and emulation, finds that at last the left side frequency band of second filter has skew, and is bigger to the frequency selectivity influence of system.Therefore, work mainly is placed on the optimal design of second filter: corrected the skew of the centre frequency in its filter, and improved the outer attenuation characteristic of filter 3dB passband.After accomplishing the electronic circuit module and optimizing, analyze the whole system frequency selectivity, result such as Fig. 7, can find out optimization from the result after, " ripple bag " is basic to be eliminated.

To sum up; In the present invention; Proposed from the frequency selectivity curve of the angle analysis receiver RF system of integral body; Can under the inner detail parameters condition of unknown of receiver RF system, utilize the associated in correspondence relation of radio system and inner electronic circuit module, the locator module frequency is optionally potential undesirable section fast; When predicting potential disturbed frequency band, also considered the heavily injection of local oscillation signal, the disturbed frequency band of multianalysis to energy.No matter this method is to the receiver prediction in preset meter stage, still to reinforcing all has good directive function with electromagnetic compatibility for completed receiver system electromagnetic interference problem diagnosis.

Claims (4)

1. the Forecasting Methodology of the potential disturbed frequency band of receiver RF system is characterized in that may further comprise the steps:

1) seeks " ripple bag " or undesirable section in some frequency band range that occurs the curve fluctuating in the receiver RF system overall frequency selectivity curve;

2) select characteristic curve associated in correspondence relation frequently according to receiver RF system overall frequency selectivity curve and inner electronic circuit module, find and the corresponding electronic circuit module of the undesirable frequency band of system;

3) analyze the frequency band of this electronic circuit module, find disturbed frequency band, thereby foundation is provided for the optimization of entire system frequency selectivity;

In said step 2) in, the combination interference frequency band with local oscillation signal also will be analyzed, to find potential disturbed frequency band;

The analysis emphasis of combination interference is signal and the combination with more superpower local oscillation signal, considers the non-linear of radio system, and analysis is that its input-output characteristic is used power series expansion with the method for the combination interference frequency band of local oscillation signal:

$u_o=\underset{n=1}{\overset{\∞}{\mathrm{\Σ}}}{a}_n{u}_i^n=a_1{u}_i+a_2{u}_i^2+a_3{u}_i^3\·\·\·+a_n{u}_i^n,$

Wherein: a _nBe each item coefficient, u _iBe input signal, u _oBe the output signal.

2. the Forecasting Methodology of the potential disturbed frequency band of receiver RF system as claimed in claim 1 is characterized in that:

In said step 2) in, the foundation that receiver RF system overall frequency selectivity curve and inner submodule frequency selectivity curve incidence relation are judged is: frequency mixer is to the last down-conversion mode of signal, and the frequency of signal does behind the process frequency mixer | f _LO± f _i|, f wherein _LOBe local oscillation signal frequency, f _iBe the frequency mixer frequency input signal, in case f _iBefore be negative sign, then the filter frequencies selectivity curve behind this frequency mixer can be that left and right sides sideband exchange appears in the boundary with the centre frequency when contribution receiving system overall frequency selectivity.

3. the Forecasting Methodology of the potential disturbed frequency band of receiver RF system as claimed in claim 1 is characterized in that:

Undesirable section in said some frequency band range in receiver RF system overall frequency selectivity curve is meant that the descending grade of curve in these frequency band ranges is slower.

4. the Forecasting Methodology of the potential disturbed frequency band of receiver RF system as claimed in claim 1 is characterized in that:

Said receiver RF system is meant that antenna reception back does not wherein comprise the demodulation part after antenna part and intermediate frequency are exported to this section of intermediate frequency output in the receiver.

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