CN103916149B - Down conversion method, device and the equipment with this device - Google Patents
Down conversion method, device and the equipment with this device Download PDFInfo
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Abstract
The present invention relates to a kind of down conversion method, device and the equipment with this device, the method comprises: receive digital medium-frequency signal; Obtain the phase value of local carrier signal; Corresponding sine value and cosine value is searched in a lookup table according to the phase value obtained; Polarity according to the sine value searched and cosine value and digital medium-frequency signal is determined and the amplitude of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling.Down conversion method of the present invention, device and the equipment with this device avoid and digital medium-frequency signal and local carrier signal are carried out complicated multiplication and add operation, save resource, decrease operand, improve signal transacting speed.
Description
Technical field
The present invention relates to signal processing technology, particularly relate to a kind of down conversion method, device and the equipment with this device.
Background technology
In GNSS (GlobalNavigationSatelliteSystem, GPS (Global Position System)), the satellite-signal that antenna receives becomes intermediate-freuqncy signal after analog down.In order to this satellite-signal is caught, follows the tracks of or pseudo-time extract (extraction of pseudo-random code sequence synchronised clock), need to carry out digital sample to generate digital medium-frequency signal to this intermediate-freuqncy signal, the digital medium-frequency signal of sampling is multiplied with local quadrature carrier and carries out mixing, realize peeling off (down-conversion) the carrier wave of this satellite-signal, and generate in-phase signal (I) and orthogonal signalling (Q), this in-phase signal is multiplied with orthogonal signalling can realizes despreading with local pseudo noise code.After despreading process, then can carry out follow-up such as catching, follow the tracks of, pseudo-time the process such as extraction.
Carrying out in down-conversion optical mixing process to digital medium-frequency signal in prior art, usually SIN value (sine value) and the COS value (cosine value) of local carrier signal is exported by carrier wave NCO, then it correspondingly with the two paths of signals of intermediate-freuqncy signal is multiplied, need in the process be multiplied to carry out a large amount of computings, take comparatively multiple resource, affect the efficiency of signal transacting.
Summary of the invention
Provide hereinafter about brief overview of the present invention, to provide about the basic comprehension in some of the present invention.Should be appreciated that this general introduction is not summarize about exhaustive of the present invention.It is not that intention determines key of the present invention or pith, and nor is it intended to limit the scope of the present invention.Its object is only provide some concept in simplified form, in this, as the preorder in greater detail discussed after a while.
A main purpose of the present invention is the defect overcoming prior art, provides a kind of down conversion method and the device that improve signal transacting efficiency.
Another main purpose of the present invention is to provide a kind of equipment with above-mentioned down-conversion device.
For achieving the above object, the invention provides a kind of down conversion method, comprising:
S1: receive digital medium-frequency signal, the polarity of described digital medium-frequency signal refers to that the value of the homophase of described digital medium-frequency signal, orthogonal two paths of signals is just or is negative;
S2: the phase value obtaining local carrier signal;
S3: search corresponding sine value and cosine value in a lookup table according to the phase value obtained;
S4: the polarity according to the sine value searched and cosine value and digital medium-frequency signal is determined and the amplitude of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling.
For achieving the above object, present invention also offers a kind of down-conversion device, comprising:
Signal receiving module, for receiving digital medium-frequency signal, the polarity of described digital medium-frequency signal refers to that the value of the homophase of described digital medium-frequency signal, orthogonal two paths of signals is just or is negative;
Phase value acquisition module, for obtaining the phase value of local carrier signal;
Search module, for searching corresponding sine value and cosine value in a lookup table according to the phase value obtained;
Processing module, for determining and the amplitude of the in-phase signal exported after this digital medium-frequency signal down-conversion and orthogonal signalling according to the polarity of the sine value searched and cosine value and digital medium-frequency signal.
For achieving the above object, the present invention also provides a kind of equipment, comprises above-mentioned down-conversion device.
Down conversion method of the present invention, device and the equipment with this device, phase value according to local carrier signal searches sine value and cosine value in a lookup table, and can directly obtain the two paths of signals after down-conversion according to the polarity of the sine value searched and cosine value and digital medium-frequency signal, avoid and digital medium-frequency signal and local carrier signal are carried out complicated multiplication and add operation, save resource, decrease operand, improve signal transacting speed.
Accompanying drawing explanation
Below with reference to the accompanying drawings illustrate embodiments of the invention, above and other objects, features and advantages of the present invention can be understood more easily.Parts in accompanying drawing are just in order to illustrate principle of the present invention.In the accompanying drawings, same or similar technical characteristic or parts will adopt same or similar Reference numeral to represent.
Fig. 1 is the block diagram of a kind of embodiment of GPS (Global Position System), and this GPS (Global Position System) can comprise down-conversion device of the present invention.
Fig. 2 is the flow chart of a kind of embodiment of down conversion method of the present invention.
Fig. 3 is the block diagram of a kind of embodiment of down-conversion device of the present invention.
Embodiment
With reference to the accompanying drawings embodiments of the invention are described.The element described in an accompanying drawing of the present invention or a kind of execution mode and feature can combine with the element shown in one or more other accompanying drawing or execution mode and feature.It should be noted that for purposes of clarity, accompanying drawing and eliminate expression and the description of unrelated to the invention, parts known to persons of ordinary skill in the art and process in illustrating.
The invention provides a kind of down conversion method, comprise the following steps:
S1: receive digital medium-frequency signal;
S2: the phase value obtaining local carrier signal;
S3: search corresponding sine value and cosine value in a lookup table according to the phase value obtained;
S4: the polarity according to the sine value searched and cosine value and digital medium-frequency signal is determined and the amplitude of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling.
Alternatively, digital medium-frequency signal is 1 bit quantized signal.
Alternatively, sine value and the cosine value of the phase value at least any one quadrant is stored under plane right-angle coordinate in look-up table; Corresponding sine value is searched in a lookup table and cosine value is specially according to the phase value obtained:
When the phase value obtained cannot directly find in a lookup table, within the scope according to trigonometric function formula phase value being transformed to the phase value stored in look-up table, then with the phase value after conversion for address, search corresponding sine value and cosine value;
When the phase value obtained can directly find in a lookup table, with the phase value obtained for address, search corresponding sine value and cosine value.
Alternatively, the polarity according to the sine value searched and cosine value and digital medium-frequency signal is determined and the value of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling, is specially:
Digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is imaginary part, and j is imaginary unit;
Work as ri=1, during rq=1, the amplitude of in-phase signal and orthogonal signalling is respectively sin θ and cos θ;
Work as ri=1, during rq=-1, the amplitude of in-phase signal and orthogonal signalling is respectively cos θ and-sin θ;
Work as ri=-1, during rq=1, the amplitude of in-phase signal and orthogonal signalling is respectively-cos θ and sin θ;
Work as ri=-1, during rq=-1, the amplitude of in-phase signal and orthogonal signalling is respectively-sin θ and-cos θ;
Wherein θ is the phase value obtained.
Present invention also offers a kind of down-conversion device, comprising:
Signal receiving module, for receiving digital medium-frequency signal;
Phase value acquisition module, for obtaining the phase value of local carrier signal;
Search module, for searching corresponding sine value and cosine value in a lookup table according to the phase value obtained;
Processing module, for determining and the amplitude of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling according to the polarity of the sine value searched and cosine value and digital medium-frequency signal.
Alternatively, digital medium-frequency signal is 1 bit quantized signal.
Alternatively, sine value and the cosine value of the phase value at least any one quadrant is stored under plane right-angle coordinate in look-up table; Search module for:
When the phase value obtained cannot directly find in a lookup table, within the scope according to trigonometric function formula phase value being transformed to the phase value stored in look-up table, then with the phase value after conversion for address, search corresponding sine value and cosine value;
When the phase value obtained can directly find in a lookup table, with the phase value obtained for address, search corresponding sine value and cosine value.
Alternatively, digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is imaginary part, and j is imaginary unit; Processing module is used for:
When ri=1, rq=1, the amplitude of in-phase signal and orthogonal signalling is made to be respectively sin θ and cos θ;
When ri=1, rq=-1, the amplitude of in-phase signal and orthogonal signalling is made to be respectively cos θ and-sin θ;
When ri=-1, rq=1, the amplitude of in-phase signal and orthogonal signalling is made to be respectively-cos θ and sin θ;
When ri=-1, rq=-1, the amplitude of in-phase signal and orthogonal signalling is made to be respectively-sin θ and-cos θ;
Wherein θ is the phase value obtained.
The present invention also provides a kind of equipment, comprises above-mentioned down-conversion device.
With reference to figure 1, down conversion method of the present invention and device can be applicable to GNSS (GlobalNavigationSatelliteSystem, GPS (Global Position System)) in, this GNSS comprises antenna, radio-frequency module, ADC (Analog-to-DigitalConverter, analog to digital converter), baseband module and post-processing module.Antenna is used for receiving satellite signal, radio-frequency module carries out analog down to generate analog if signal to the satellite-signal that antenna receives, this analog if signal carries out forming digital medium-frequency signal after digitized sampling through ADC, this digital medium-frequency signal generates I, Q (homophase and orthogonal) two paths of signals after the Digital Down Convert device in baseband module carries out Digital Down Convert, and this I, Q two paths of signals is multiplied with the pseudo noise code of this locality in baseband module can realize the despreading of signal.Signal after despreading can carry out subsequent treatment via post-processing module, such as catch, follow the tracks of, pseudo-time extract.Above-mentioned ADC also can be comparator.
A kind of embodiment of down conversion method of the present invention is used for carrying out down-conversion to this digital medium-frequency signal, and it comprises the following steps:
S1: receive digital medium-frequency signal.In this step, the digital medium-frequency signal from ADC or comparator can be received.This digital medium-frequency signal specifically can be described as: r=ri+j*rq, and wherein ri is real number, and rq is imaginary number, and j is imaginary unit.
S2: the phase value obtaining local carrier signal.This step is specifically by detecting the local carrier signal of NCO output to obtain its phase value, and the local quadrature carrier signals produced specifically can be described as s=si+j*sq, and wherein si is real number, and sq is imaginary number, and j is imaginary unit.The phase value obtained in this step can between 0-360 degree.
S3: search corresponding sine value and cosine value in a lookup table according to the phase value obtained.
S4: the polarity according to the sine value searched and cosine value and digital medium-frequency signal is determined and the amplitude of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling.
Particularly, can store sine value and the cosine value of the multiple phase values between 0-360 degree in look-up table, then, when searching, the phase value that can obtain is that address searches corresponding sine value and cosine value in a lookup table.
In order to save memory space, also sine value and the cosine value of the phase value under plane right-angle coordinate at least any quadrant can be only stored in, when the phase value obtained is not in this quadrant, directly cannot search the phase value of acquisition in a lookup table, then according to trigonometric function formula, the phase value of acquisition is transformed to the phase value of the correspondence stored in look-up table, and with the phase value of the correspondence stored in look-up table for address, search corresponding sine value and cosine value.
Such as, can only store in first quartile in look-up table, the sine value of the phase value namely between 0 degree of-90 degree and cosine value, that is, only store corresponding sine value and cosine value using the phase value between 0-90 degree as address.
Suppose that the phase value obtained be φ 1, φ 2 is the phase value stored in look-up table, and there is following relation between φ 1 and φ 2:
When φ 1 is at the second quadrant, φ 1=180-φ 2, then φ 2=180-φ 1;
When φ 1 is at third quadrant, φ 1=180+ φ 2; Then φ 2=φ 1-180;
When φ 1 is in fourth quadrant, φ 1=360-φ 2; Then φ 2=360-φ 1;
So can transform within the scope of the phase value stored in look-up table according to the following phase value that trigonometric function formula (f1)-(f6) cannot directly find in a lookup table, again with conversion after phase value for address, search corresponding sine value and cosine value, then determine the positive and negative of its sine value and cosine value according to the phase value obtained.
sin(π-a)＝sina，(f1)；
cos(π-a)＝-cosa，(f2)；
sin(π+a)＝-sina，(f3)；
cos(π+a)＝-cosa，(f4)；
sin(2kπ-α)＝-sinα，(f5)；
cos(2kπ-α)＝cosα，(f6)。
When φ 1 is at the second quadrant:
From above formula (f1), sin φ 1=sin (180-φ 2)=sin φ 2, (f1.1)
From above formula (f2), cos φ 1=cos (180-φ 2)=-cos φ 2, (f2.1);
So, when φ 1 is at the second quadrant, want to obtain sin φ 1 and cos φ 1, then can with φ 2 for address search be to sin φ 2 and cos φ 2, again according to above formula (f1.1) and (f2.1), the sin φ 2 searched is defined as sin φ 1, cos φ 2 is overturn as-cos φ 2 is defined as cos φ 1.
When φ 1 is at third quadrant:
From above formula (f3), sin φ 1=sin (180+ φ 2)=-sin φ 2, (f3.1);
From above formula (f4), cos φ 1=cos (180+ φ 2)=-cos φ 2, (f4.1);
So, when φ 1 is at third quadrant, want to obtain sin φ 1 and cos φ 1, then can with φ 2 for address search be to sin φ 2 and cos φ 2, again according to above formula (f3.1) and (f4.1), the sin φ 2 searched is defined as sin φ 1 as upset for-sin φ 2, the cos φ 2 searched is overturn as-cos φ 2 is defined as cos φ 1.
When φ 1 is in fourth quadrant:
From above formula (f5), sin φ 1=sin (360-φ 2)=-sin φ 2, (f5.1);
From above formula (f6), cos φ 1=cos (360-φ 2)=cos φ 2, (f6.1);
So, when φ 1 is in fourth quadrant, want to obtain sin φ 1 and cos φ 1, then can with φ 2 for address search be to sin φ 2 and cos φ 2, again according to above formula (f5.1) and (f6.1), the sin φ 2 searched is defined as sin φ 1 as upset for-sin φ 2, the cos φ 2 searched is defined as cos φ 1.
Therefore, in step S4, when determining the amplitude of I, Q two paths of signals according to the polarity of the sine value searched and cosine value and digital medium-frequency signal, there are two kinds of situations, when the phase value obtained can directly find in a lookup table, directly according to the amplitude that the polarity of digital medium-frequency signal is carried out as I, Q two paths of signals after polarity process (keep polarity constant, negatively maybe just to become just becoming negative) to the sine value found and cosine value.
Another is, when the phase value obtained can not directly find in a lookup table, need first to carry out the first polarity process according to the trigonometric function formula of correspondence to the sine value searched and cosine value, be transformed to sine value and the cosine value of the phase value of acquisition, then according to the polarity of digital medium-frequency signal, the second polarity process carried out to the sine value under the phase value of this acquisition and cosine value.The sequencing of the first polarity process described herein and the second polarity process is only used to its principle is described, when actual enforcement is of the present invention, this first polarity process and the second polarity process can be carried out simultaneously, or, first carry out the second polarity process, then carry out the first polarity process.
The polarity of above-mentioned digital medium-frequency signal refers to that the value (ri and rq) of the homophase of this digital medium-frequency signal, orthogonal two paths of signals is just or is negative.Due in the present embodiment, this digital medium-frequency signal is 1 bit quantized signal, then its polarity can comprise following four kinds: the first is ri=1, rq=1; The second is ri=1, rq=-1; The third is ri=-1, rq=1; 4th kind is ri=-1, rq=-1.
In step S4, the amplitude of I, Q two paths of signals can be determined according to the relation of the amplitude of the polarity of digital medium-frequency signal described below and I, Q two paths of signals:
Work as ri=1, during rq=1, the value of in-phase signal and orthogonal signalling is respectively sin θ and cos θ; Work as ri=1, during rq=-1, the value of in-phase signal and orthogonal signalling is respectively cos θ and-sin θ; Work as ri=-1, during rq=1, the value of in-phase signal and orthogonal signalling is respectively-cos θ and sin θ; Work as ri=-1, during rq=-1, the value of in-phase signal and orthogonal signalling is respectively-sin θ and-cos θ, and wherein θ is the phase value obtained.
Further step S4 is described below by citing:
Such as, suppose the phase value that stores in look-up table between 90-180 degree, the phase value θ 1 that obtains is also at 90-180 degree, and sine value corresponding with θ 1 in look-up table and cosine value are respectively A4 and B4, then can find sine value A4 and cosine value B4 in a lookup table.If now the two paths of signals (being set to ri and rq respectively) of digital medium-frequency signal is+1, then keep the polarity constant (being just) of sine value A4 and cosine value B4, and A4 and B4 is defined as respectively the amplitude of I (in-phase signal), Q (orthogonal signalling) two paths of signals; If ri is+1, rq is-1, then keep cosine value B4 polarity constant, become negative by the polarity of sine value A4, then the amplitude of I, Q two paths of signals is respectively-A4 and B4.
Suppose that the phase value θ 2 obtained is at first quartile, the phase value θ 3 of a third quadrant and the phase value θ 4 of a fourth quadrant is stored in look-up table, and θ 2 and θ 3 and between θ 2 and θ 4, there is following relation: θ 2=θ 3-180, θ 2=360-θ 4.Can θ 3 be then address search sin θ 3 and cos θ 3, and the polarity of the sin θ 2, cos θ 2 and the digital medium-frequency signal that obtain according to the relation between the sine value of θ 2 and θ 3, cosine value determine the amplitude of I, Q two paths of signals; Or with θ 4 for address search sin θ 4 and cos θ 4, and the polarity of the sin θ 2, cos θ 2 and the digital medium-frequency signal that obtain according to the relation between the sine value of θ 2 and θ 4, cosine value determines the amplitude of I, Q two paths of signals.Such as:
Sin θ 2=-sin θ 3, cos θ 2=-cos θ 3, when ri be+1, rq is-1, the amplitude of in-phase signal is-cos θ 2=cos θ 3, and the amplitude of orthogonal signalling is-sin θ 2=sin θ 3.
Sin θ 2=-sin θ 4, cos θ 2=cos θ 4, when ri be-1, rq is 1, the amplitude of in-phase signal is-cos θ 2=-cos θ 4, and the amplitude of orthogonal signalling is sin θ 2=-sin θ 4.
Sine value under the amplitude of this I, Q two paths of signals and the phase place of acquisition and the relation between the polarity of cosine value and digital medium-frequency signal are obtained by following inference:
If carry out the signal after down-conversion to this digital medium-frequency signal be:
dem＝r*s＝(ri+j*rq)*(si+j*sq)(1)
Make the signal after Digital Down Convert be dem=demi+j*demq, wherein demi is real number, the in-phase signal obtained after carrying out down-conversion in order to description to digital medium-frequency signal; Demq is imaginary number, the orthogonal signalling obtained after carrying out down-conversion in order to description to digital medium-frequency signal; J is imaginary unit.Then:
demi＝ri*si-rq*sq
demq＝ri*sq+rq*si(2)
Make si=Sin [φ], sq=Cos [φ], wherein φ is arbitrary phase value, then have
demi＝ri*Sin[φ]-rq*Cos[φ]
demq＝ri*Cos[φ]+rq*Sin[φ](3)
Work as ri=1, during rq=1,
Work as ri=1, during rq=-1,
Work as ri=-1, during rq=1,
Work as ri=-1, during rq=-1,
Make φ=θ+π/4, wherein θ is the phase value obtained.Make amplitude simultaneously divided by
then:
Work as ri=1, during rq=1
demi＝Sinθ
demq＝Cosθ(8)
Work as ri=1, during rq=-1
demi＝Cosθ
demq＝-Sinθ(9)
Work as ri=-1, during rq=1
demi＝-Cosθ
(10)
demq＝Sinθ
Work as ri=-1, during rq=-1
demi＝-Sinθ
(11)
demq＝-Cosθ
From above formula (8)-(11), work as ri=1, during rq=1, the value of in-phase signal and orthogonal signalling is respectively sin θ and cos θ; Work as ri=1, during rq=-1, the value of in-phase signal and orthogonal signalling is respectively cos θ and-sin θ; Work as ri=-1, during rq=1, the value of in-phase signal and orthogonal signalling is respectively-cos θ and sin θ; Work as ri=-1, during rq=-1, the value of in-phase signal and orthogonal signalling is respectively-sin θ and-cos θ.
With reference to figure 3, a kind of embodiment of down-conversion device of the present invention comprises: signal receiving module 10, phase place acquisition module 20, search module 30 and processing module 40.
The digital medium-frequency signal that signal receiving module 10 produces for receiving such as ADC.
Phase place acquisition module 20 is for obtaining the phase value of local carrier signal, and particularly, the phase value of this local carrier signal can produce from 0 degree of carry out phase-accumulated via NCO, and phase place acquisition module 20 receives the phase value between 0-360 degree.
Search module 30 for searching corresponding sine value and cosine value in a lookup table according to the phase value obtained, can the phase value between 0-360 be wherein that address stores corresponding sine value and cosine value in look-up table, can the phase value under plane coordinate system at least in any one quadrant be also that address stores corresponding sine value and cosine value.
Processing module 40 is for determining and the amplitude of the in-phase signal exported after digital medium-frequency signal down-conversion and orthogonal signalling (I, Q two paths of signals) according to the polarity of the sine value searched and cosine value and digital medium-frequency signal.
Wherein processing module 40 can determine the amplitude of I, Q two paths of signals according to the relation of the amplitude of the polarity of the sine value/cosine value of the above-mentioned phase value searched, digital medium-frequency signal and I, Q two paths of signals.
When the phase value obtained cannot directly find in a lookup table, within the scope according to trigonometric function formula phase value being transformed to the phase value stored in look-up table, again with conversion after phase value for address, search corresponding sine value and cosine value, determine the positive and negative of its sine value and cosine value according to the phase value obtained again, then determine the amplitude of I, Q two paths of signals according to the sine value of the polarity of digital medium-frequency signal and the phase value of acquisition and cosine value.
When the phase value obtained can directly find in a lookup table, with the phase value obtained for address, search corresponding sine value and cosine value.The amplitude of I, Q two paths of signals is determined again according to the sine value of the polarity of digital medium-frequency signal and the phase value of acquisition and cosine value.
Equipment of the present invention can comprise above-mentioned down-conversion device, and equipment of the present invention can be, such as, for carrying out the equipment of signal transacting in GNSS.
Down conversion method of the present invention and device search sine value and cosine value in a lookup table according to the phase value of local carrier signal, and can directly obtain the two paths of signals after down-conversion according to the polarity of the sine value searched and cosine value and digital medium-frequency signal, avoid and digital medium-frequency signal and local carrier signal are carried out complicated multiplication and add operation, save resource, decrease operand, improve signal transacting speed.
Further, corresponding sine value and cosine value is stored as address by the phase value only arbitrarily in quadrant, and the sine value corresponding to phase value outside this quadrant and cosine value is determined by the symmetric relation of each phase value in quadrant, the amplitude of in-phase signal and orthogonal signalling can either be determined fast, can also storage resources be saved.
Further, digital intermediate frequency is made to be 1 bit quantized signal, when keeping noise less, also can simplified operation further, promotion signal treatment effeciency.
In the system and method for the present invention, obviously, each parts or each step reconfigure after can decomposing, combine and/or decomposing.These decompose and/or reconfigure and should be considered as equivalents of the present invention.Simultaneously, above in the description of the specific embodiment of the invention, the feature described for a kind of execution mode and/or illustrate can use in one or more other execution mode in same or similar mode, combined with the feature in other execution mode, or substitute the feature in other execution mode.
Should emphasize, term " comprises/comprises " existence referring to feature, key element, step or assembly when using herein, but does not get rid of the existence or additional of one or more further feature, key element, step or assembly.
Although described the present invention and advantage thereof in detail, be to be understood that and can have carried out various change when not exceeding the spirit and scope of the present invention limited by appended claim, substituting and conversion.And scope of the present invention is not limited only to the specific embodiment of process, equipment, means, method and step described by specification.One of ordinary skilled in the art will readily appreciate that from disclosure of the present invention, can use perform the function substantially identical with corresponding embodiment described herein or obtain and its substantially identical result, existing and that will be developed in the future process, equipment, means, method or step according to the present invention.Therefore, appended claim is intended to comprise such process, equipment, means, method or step in their scope.
Claims (9)
1. a down conversion method, is characterized in that, comprises the following steps:
S1: receive digital medium-frequency signal, the polarity of described digital medium-frequency signal refers to that the value of the homophase of described digital medium-frequency signal, orthogonal two paths of signals is just or is negative;
S2: the phase value obtaining local carrier signal;
S3: search corresponding sine value and cosine value in a lookup table according to the phase value obtained;
S4: the polarity according to the sine value searched and cosine value and described digital medium-frequency signal is determined and the amplitude of the in-phase signal exported after described digital medium-frequency signal down-conversion and orthogonal signalling.
2. down conversion method according to claim 1, is characterized in that, described digital medium-frequency signal is 1 bit quantized signal.
3. down conversion method according to claim 1 and 2, is characterized in that, to store under plane right-angle coordinate sine value and the cosine value of the phase value at least any one quadrant in described look-up table; Corresponding sine value is searched in a lookup table and cosine value is specially according to the phase value obtained:
When the phase value obtained cannot directly find in described look-up table, within the scope according to trigonometric function formula described phase value being transformed to the phase value stored in described look-up table, again with the phase value after conversion for address, search corresponding sine value and cosine value;
When the phase value obtained can directly find in described look-up table, with the phase value obtained for address, search corresponding sine value and cosine value.
4. down conversion method according to claim 2, it is characterized in that, polarity according to the sine value searched and cosine value and described digital medium-frequency signal is determined and the amplitude of the in-phase signal exported after described digital medium-frequency signal down-conversion and orthogonal signalling, is specially:
Described digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is imaginary part, and j is imaginary unit;
Work as ri=1, during rq=1, the amplitude of described in-phase signal and orthogonal signalling is respectively sin θ and cos θ;
Work as ri=1, during rq=-1, the amplitude of described in-phase signal and orthogonal signalling is respectively cos θ and-sin θ;
Work as ri=-1, during rq=1, the amplitude of described in-phase signal and orthogonal signalling is respectively-cos and sin θ;
Work as ri=-1, during rq=-1, the amplitude of described in-phase signal and orthogonal signalling is respectively-sin θ and-cos θ;
Wherein θ is the phase value obtained.
5. a down-conversion device, is characterized in that, comprising:
Signal receiving module, for receiving digital medium-frequency signal, the polarity of described digital medium-frequency signal refers to that the value of the homophase of described digital medium-frequency signal, orthogonal two paths of signals is just or is negative;
Phase value acquisition module, for obtaining the phase value of local carrier signal;
Search module, for searching corresponding sine value and cosine value in a lookup table according to the phase value obtained;
Processing module, for determining and the amplitude of the in-phase signal exported after described digital medium-frequency signal down-conversion and orthogonal signalling according to the polarity of the sine value searched and cosine value and described digital medium-frequency signal.
6. down-conversion device according to claim 5, is characterized in that, described digital medium-frequency signal is 1 bit quantized signal.
7. the down-conversion device according to claim 5 or 6, is characterized in that, to store under plane right-angle coordinate sine value and the cosine value of the phase value at least any one quadrant in described look-up table; Described search module for:
When the phase value obtained cannot directly find in described look-up table, according to trigonometric function formula, described phase value is become
Within the scope changing to the phase value stored in described look-up table, then with the phase value after conversion for address, search corresponding sine value and cosine value;
When the phase value obtained can directly find in described look-up table, with the phase value obtained for address, search corresponding sine value and cosine value.
8. down-conversion device according to claim 6, is characterized in that, described digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is imaginary part, and j is imaginary unit; Described processing module is used for:
When ri=1, rq=1, the amplitude of described in-phase signal and orthogonal signalling is made to be respectively sin θ and cos θ;
When ri=1, rq=-1, the amplitude of described in-phase signal and orthogonal signalling is made to be respectively cos θ and-sin θ;
When ri=-1, rq=1, the amplitude of described in-phase signal and orthogonal signalling is made to be respectively-cos θ and sin θ;
When ri=-1, rq=-1, the amplitude of described in-phase signal and orthogonal signalling is made to be respectively-sin θ and-cos θ;
Wherein θ is the phase value obtained.
9. an equipment, is characterized in that, comprises the down-conversion device in claim 5-8 described in any one.
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