CN101515913B - Fixed loop control method based on additions and shifts - Google Patents

Abstract

The invention discloses a fixed loop control method based on additions and shifts. Aiming at realizing the requirement of loop control in processing baseband signals of spread spectrum communication receivers by adopting low-end processors or hardware description languages, in the method, fixed point realization is carried out on a loop discriminator by adopting algorithm realized by shifts and additions; loop filter coefficient and NCO gain are considered and are similar to integer power of 2; by shifts and additions, loop filtering is completed and new carrier frequency control words and code frequency control words are generated. The method not only greatly reduces the computation of loop control, but also can not impair the tracking accuracy of the loop basically.

Description

A kind of fixed point loop control method based on displacement and addition

Technical field

The present invention relates to the loop control field of receiver for spread spectrum communication related channel program, specifically, the present invention relates to a kind of fixed point loop control method based on displacement and addition.

Background technology

Spread-spectrum (spread spectrum) communication system is a kind of more satisfactory communication system that is based upon on the information-theoretical theoretical foundation of C.E.Shannon.It is meant and is used for the radio frequency bandwidth of the information of transmitting much larger than a kind of communication mode of the bandwidth of information own.Spread spectrum communication system has that strong interference immunity, intercepting and capturing rate are low, code division multiple access, signal are hidden, strong security, find range and be easy to the advantage of many uniquenesses such as networking, has been widely used in every field such as communication, navigation, radar, location, range finding, remote control, space flight, electronic countermeasures, mobile communication at present.

Related channel program is one of core processing module of DSSS communication control processor, and its research emphasis mainly is the tracking around signal carrier and pseudo-code.The spread-spectrum signal that antenna receives amplifies through low noise amplifier, and is down-converted to intermediate frequency, becomes digital signal through analog-digital converter (ADC) sampling then.Accomplish after the catching of spread-spectrum signal when band spread receiver, just code phase that captures and carrier doppler are inserted related channel program, begin carrier phase and pseudo-code phase are carried out accurate tracking.

Related channel program is made up of modules such as correlator, loop control, data extract, observed quantity extractions.Correlator is realized by field programmable gate array (FPGA) or application-specific integrated circuit (ASIC) (ASIC) that generally its completion is peeled off carrier wave and pseudo-code, and realizes the pre-detection integration.The loop control module according to the leading, instant of homophase (I) road of correlator output and quadrature (Q) road and hysteresis adds up and, through phase demodulation, filtering and generate new carrier frequency control word and the realization of code frequency control word to the FEEDBACK CONTROL of related channel program.When loop-locking, can carry out bit synchronization, the frame synchronization of data, and the extraction of observed quantity such as pseudorange, Doppler frequency.

The loop control structure of carrier tracking loop and code tracking loop is the same, all is made up of phase discriminator, filter and digital controlled oscillator (NCO) three parts.Carrier tracking loop adopts modulates the accurate tracking of insensitive section Stas (Costas) ring realization to carrier phase to data.The carrier tracking loop of a good design should be earlier be operated in wide band to dynamically more firm FLL (FLL) with the loop closure; Carry out the transition to the Costas ring work of big bandwidth then gradually, at last again with the wide steady operation pattern that narrows to of Costas endless belt.Code tracking loop adopts delay lock loop (DLL) to realize the accurate tracking to pseudo-code phase.Because carrier wave ring auxiliary code loop technique all in can the blanking code ring are dynamic, so endless belt is wide can do very narrowly with respect to the carrier wave endless belt is wide for sign indicating number, to improve the pseudorange precision.

The theory analysis of controlling about loop at present, and relevant characters all has very ripe conclusion.But generally when realizing adopt the control of floating-point loop, though can loss of accuracy, this makes to the having relatively high expectations of processor, and is difficult to realize with the direct hardware of hardware description language.

Summary of the invention

Technical problem to be solved by this invention is: to adopting low side processor or hardware description language to realize the requirement of receiver for spread spectrum communication base band signal process intermediate ring road control; Proposed a kind of fixed point loop control method based on displacement and addition, it is realized through the following step:

A. correlator is accomplished and is exported 6 accumulation results after integration adds up, and the loop control module realizes the control to carrier tracking loop and code tracking loop according to these 6 accumulation results;

B. adopt rotation of coordinate numerical calculation (Cordic) algorithm to realize two quadrant arc tangent (atan), accomplish the work of carrier wave ring phase discriminator, i.e. atan (Q _P/ I _P), form carrier wave ring phase demodulation error x (n);

C. to carrier wave ring phase demodulation error x (n), carrier wave ring intermediate variable u (n-1) and u (n-2), after suitable displacement and add operation, realize the carrier wave ring wave filter, form carrier wave ring wave filter output z (n) and new carrier wave ring intermediate variable u (n);

D. carrier wave ring wave filter output z (n) adds carrier wave IF-FRE control word, forms new carrier frequency control word, feeds back to track loop the carrier wave ring is controlled;

E. upgrade carrier wave ring intermediate variable, use for loop control next time, so far, the control of carrier wave ring loop is accomplished;

F. adopt approximate data to calculate envelope, accomplish respectively the lead and lag calculating with envelope that adds up;

G. adopt the phase discriminator work of accomplishing the sign indicating number ring based on the binary division module of displacement and addition, generated code ring phase demodulation error x (n);

H. to sign indicating number ring phase demodulation error x (n), sign indicating number ring intermediate variable u (n-1), after suitable displacement and add operation, realize the sign indicating number ring wave filter, generated code ring wave filter output z (n) and new yard ring intermediate variable u (n);

I. sign indicating number ring wave filter output z (n) adds that carrier wave ring wave filter output z (n) divided by the carrier wave auxiliary parameter that scale factor obtains, adds a yard IF-FRE control word, forms new code frequency control word, feeds back to track loop the sign indicating number ring is controlled;

J. upgrade sign indicating number ring intermediate variable, use for loop control next time, so far, the control of sign indicating number ring loop is accomplished.

In above-mentioned steps c, the carrier wave ring wave filter is three rank filters, adopts direct II type to realize, and filter coefficient and NCO gain are taken all factors into consideration, and is approximately 2 integral number power, adopts displacement to realize, amount of displacement can be according to the loop bandwidth decision of design.

In above-mentioned steps h, the sign indicating number ring wave filter is a second order filter, adopts direct II type to realize, and filter coefficient and NCO gain are taken all factors into consideration, and is approximately 2 integral number power, adopts displacement to realize, amount of displacement can be based on the loop bandwidth decision of design.

The present invention compared with prior art, maximum characteristics are that all operations all are reduced to a series of displacements and add operation in the whole loop control procedure, and through the choose reasonable bit wide, do not lose tracking accuracy basically.This makes the realization of loop control can adopt the very processor of low side, perhaps can also realize with the direct hardware of hardware description language.Operand is low so the present invention has, and implementation is simple, does not influence the advantage of loop tracks precision.

Description of drawings

Through the detailed description of carrying out below in conjunction with accompanying drawing, above and other objects of the present invention and characteristics will become apparent, wherein:

Fig. 1 is the exemplary block diagram of receiver for spread spectrum communication related channel program.

Fig. 2 is the implementation method of fixed point loop control in the related channel program.

Fig. 3 is the iteration block diagram of Cordic algorithm.

Fig. 4 is the digital filter configuration block diagram of carrier tracking loop.

Fig. 5 adopts displacement and addition to realize the structured flowchart of binary division.

Fig. 6 is the digital filter configuration block diagram of code tracking loop.

Embodiment

Reference is below in conjunction with the detailed description of accompanying drawing to exemplary embodiment, and the method for advantage of the present invention and characteristics and realization can more easily be understood.

Fig. 1 is the extensively exemplary block diagram of the related channel program of employing of present receiver for spread spectrum communication.After sampled data gets into related channel program; At first peel off with the sine and cosine carrier multiplication realization carrier wave of this locality; To produce homophase (I) and quadrature (Q) data, the realization of multiplying each other of the reproduction sign indicating number of leading (E), instant (P) and the hysteresis (L) that produces with this locality respectively then yard is peeled off, and carries out integration and add up.The loop control module generates new carrier frequency control word and code frequency control word according to the integration accumulation result of correlator, and track loop is carried out FEEDBACK CONTROL.

Fig. 2 is the implementation method of fixed point loop control in the related channel program, is divided into control of carrier wave ring and sign indicating number ring control two large divisions.It is realized through following step.

A. correlator is accomplished and is exported 6 accumulation results after integration adds up, i.e. leading (the I of homophase _E), the instant (I of homophase _P), the homophase (I that lags behind _L), the leading (Q of quadrature _E), the instant (Q of quadrature _P), the quadrature (Q that lags behind _L), carrier tracking loop adopts I _PAnd Q _PControl, the sign indicating number ring adopts I _E, I _L, Q _EAnd Q _LControl.

B. adopt the Cordic algorithm to realize two quadrant arc tangent atan, accomplish the work of carrier wave ring phase discriminator, i.e. atan (Q _P/ I _P), form carrier wave ring phase demodulation error x (n).The data area of identified result is [pi/2, a pi/2], when adopting fixed point to realize, need adopt the Q format notation that it is represented, promptly x (n) expanded the position identified result, treat that filtering gives up identical figure place again after intact and get final product.The Q form of x (n) is generally got Q30 by the Q format determination of look-up table content in the Cordic algorithm, but when being input to loop filter, adopts Q30 can occupy excessive bit wide x (n), can it be truncated to Q5, the littler precision that can influence the carrier wave ring.

C. adopt a series of displacements and addition to realize the carrier wave ring wave filter, form carrier wave ring wave filter output z (n) and new carrier wave ring intermediate variable u (n).The carrier wave ring wave filter adopts three rank filters, can carry out tenacious tracking to acceleration.Carrier wave ring wave filter output z (n) is made up of 6 additions altogether, is respectively:

Carrier wave ring phase error x (n) a position that moves to left;

Carrier wave ring phase error x (n) the b position that moves to left;

Carrier wave ring phase error x (n) the c position that moves to left;

Intermediate variable u of the previous moment of carrier wave ring (n-1) move to left (a+2) position;

Intermediate variable u of the previous moment of carrier wave ring (n-1) move to left (b+1) position;

Preceding two intermediate variable u (n-2) (b+1) positions that move to left constantly of carrier wave ring;

New carrier wave ring intermediate variable u (n) is made up of 3 additions altogether, is respectively:

Phase error x (n);

Intermediate variable u of the previous moment of carrier wave ring (n-1) moves to left 1;

Preceding two moment intermediate variable u of carrier wave ring (n-2) get negative;

Wherein a, b, c are meant amount of displacement, move to left for just representing, for negative indication moves to right.

D. after carrier wave ring wave filter output z (n) gives up the figure place that when phase demodulation, expands, add carrier wave IF-FRE control word, promptly form new carrier frequency control word, feed back to track loop the carrier wave ring is controlled.

E. upgrade carrier wave ring intermediate variable, u (n-2) is updated to u (n-1), the u (n) with u (n-1) is updated to new formation uses for loop control next time.So far, the control of carrier wave ring loop is accomplished.

F. adopt approximate data to calculate envelope, accomplish respectively, promptly form the lead and lag calculating with envelope that adds up $E=\sqrt{{\mathrm{<figure-callout\; id="2"\; label="I\; E"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">I</figure-callout>}}_E^{}+{\mathrm{<figure-callout\; id="2"\; label="Q\; E"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">Q</figure-callout>}}_E^{}},$ $L=\sqrt{I_{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">L</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="Q\; L"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">Q</figure-callout>}}_L^{}}.$

G. adopt the phase discriminator work of accomplishing the sign indicating number ring based on the binary division module of displacement and addition, generated code ring phase demodulation error x (n), promptly

$\frac{1}{2}\&CenterDot;\frac{E-L}{E+L}$

Similar with carrier wave ring phase discriminator because (E-L)/(E+L) range of results be [1,1], so also need adopt the Q format notation that it is represented, i.e. the result of phase discriminator output expanded the position data, treat that giving up identical figure place again after filtering finishes gets final product.Concrete expansion position figure place confirms as 7 by emulation.In addition, 2 operations that remove of sign indicating number ring phase discriminator can temporarily not done, and carry out in the lump when being left to after the filtering truncation.

H. adopt a series of displacements and addition to realize the sign indicating number ring wave filter, generated code ring wave filter output z (n) and new sign indicating number ring intermediate variable u (n).Since the carrier wave ring can auxiliary code ring eliminate all dynamically, so the sign indicating number ring wave filter adopts second order filter.Sign indicating number ring wave filter output z (n) is made up of 3 additions altogether, is respectively:

Sign indicating number ring phase error x (n) the d position that moves to left;

Sign indicating number ring phase error x (n) the e position that moves to left;

The previous moment intermediate variable u of sign indicating number ring (n-1) (d+1) position that moves to left;

New sign indicating number ring intermediate variable u (n) is made up of 2 additions altogether, is respectively:

Sign indicating number ring phase error x (n);

Sign indicating number ring previous moment intermediate variable u (n-1);

Wherein d, e are meant amount of displacement, move to left for just representing, for negative indication moves to right.

I. after sign indicating number ring wave filter output z (n) gives up the figure place that when phase demodulation, expands; Add the carrier wave auxiliary parameter that carrier wave ring wave filter output z (n) obtains divided by scale factor; Add a yard IF-FRE control word, promptly form new code frequency control word, feed back to track loop the sign indicating number ring is controlled.

J upgrades sign indicating number ring intermediate variable, and the u (n) with u (n-1) is updated to new formation uses for loop control next time.So far, the control of sign indicating number ring loop is accomplished.

For above-mentioned steps b, Fig. 3 is the iteration block diagram of Cordic algorithm.The Cordic algorithm is rotation of coordinate numerical calculation method (Coordinate Rotation Digital Computer), can carry out a lot of mathematical operations, such as sine, cosine, take advantage of again, arc tangent, ask mould etc.When with Cordic algorithm algorithm computation two quadrant arc tangent, it is operated in vector pattern, promptly

x _i+1＝x _i-y _i·d _i·2 ^-i

y _i+1＝y _i+x _i·d _i·2 ^-i

z _i+1＝z _i-d _i·tan ^-1(2 ^-i)

Wherein work as y _i＜0 o'clock d _i=1, work as y _i＞0 o'clock, d _i=-1.After the several times iteration, obtain

$x_n=A_n\sqrt{x_0^2+y_0^2}$

y _n＝0

z _n＝z ₀+tan ^-1(y ₀/x ₀)

$A_n=\underset{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">n</figure-callout>}}{\mathrm{\&Pi;}}\sqrt{1+2^{-2i}}=1.647$

Tan in the above-mentioned algorithm ^-1(2 ^-i) computing can use the realization of tabling look-up, multiply by 2 ^-iComputing can use displacement to realize, the process of calculating atan like this just by addition, be shifted and table look-up and realized.Since the angle of Cordic algorithm rotation at-pi/2 between the pi/2, so when calculating atan, must guarantee x＞0 with it.When x＜0, need earlier x and all negates of y, and then carry out computing.

For above-mentioned steps c, set forth the method for designing of amount of displacement a, b, c in the carrier track ring wave filter below.Fig. 4 is the digital filter configuration block diagram of carrier tracking loop, and its mathematic(al) representation does

y(n)＝2y(n-1)-y(n-2)+b0*x(n)+b1*x(n-1)+b2*x(n-2)

B0, b1 and b2 determine by loop parameter, promptly

b0＝k1+k2+k3

b1＝2*(k1-k3)

b2＝k1-k2+k3

Wherein

$\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">k</figure-callout>}1=\frac{{\mathrm{\&omega;}}_0^3{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{4},$ $\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">k</figure-callout>}2=\frac{a_3{\mathrm{\&omega;}}_0^2\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}{2},$ k3＝b ₃ω ₀

a3＝1.1，b3＝2.4；

T is that integration adds up the time;

ω ₀Be the loop natural circular frequency, its size is determined by loop bandwidth.

When adopting the fixed point mode to realize this filter, at first change its structure into direct II type and realize, promptly

u(n)＝x(n)+2u(n-1)-u(n-2)

y(n)＝b0*u(n)+b1*u(n-1)+b2*u(n-2)

＝(k1+k2+k3)*u(n)+2*(k1-k3)*u(n-1)+(k1-k2+k3)*u(n-2)

＝k1*[u(n)+2*u(n-1)+u(n-2)]+k2*[u(n)-u(n-2)]

+k3*[u(n)-2*u(n-1)+u(n-2)]

＝k1*[x(n)+4*u(n-1)]+k2*[x(n)+2*u(n-1)-2*u(n-2)]

+k3*x(n)

Carrier wave ring NCO adopts the Nbit accumulator to realize.For carrier wave ring NCO gain, its unit is radiansper second per unit, and meaning is 1 unit how many radians on the represents physical in 1 second of every control, promptly

$K=\frac{f_s}{2^N}\&CenterDot;2\mathrm{\&pi;}$

Because there is gain K in carrier wave NCO, will gain divided by this so feed back to the carrier frequency control word of related channel program, promptly

z(n)＝y(n)/K

＝k1/K*[x(n)+4*u(n-1)]+k2/K*[x(n)+2*u(n-1)-2*u(n-2)]

+k3/K*x(n)

＝h1*[x(n)+4*u(n-1)]+h2*[x(n)+2*u(n-1)-2*u(n-2)]

+h3*x(n)

H1, h2 and h3 are approximately 2 integral number power, so just can realize multiply operation through the mode of displacement.The carrier wave ring wave filter implementation that obtains at last does

u(n)＝x(n)+[u(n-1)＜＜1]-u(n-2)

z(n)＝[x(n)＜＜a]+[u(n-1)＜＜(a+2)]+[x(n)＜＜b]

+[u(n-1)＜＜(b+1)]-[u(n-2)＜＜(b+1)]+[x(n)＜＜c]

Wherein a, b, c are meant the quantity of displacement, and its size is determined by loop parameter, move to left for representing correct time, represent to move to right when negative.

The output z (n) of carrier wave ring wave filter adds the frequency control word f that the carrier wave intermediate frequency is corresponding _i/ f _s2 ^N, being the frequency control word that feeds back to carrier wave ring NCO, z (n) also can assist the sign indicating number ring simultaneously.

For used JPL algorithm among the above-mentioned steps f, be the short-cut method of the calculating envelope that proposes by U.S. jet propulsion laboratory (JPL), promptly for $A=\sqrt{I^2+{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">Q</figure-callout>}}^2}$ JPL be approximately

A=X+1/8Y is when X >=3Y

A=7/8X+1/2Y is when X≤3Y

Wherein X=MAX (| I|, | Q|), Y=MIN (| I|, | Q|).Adopt displacement mode to realize above-mentioned computing, promptly

A=X+ (Y＞＞3) is when X >=[Y+ (Y＜＜1)]

A=X-(X＞＞3)+(Y＞＞1) is when X≤[Y+ (Y＜＜1)]

For above-mentioned steps g and the used division of step I, Fig. 5 shows the realization block diagram that adopts displacement and addition to realize binary division.Binary division compares with divisor and dividend in fact exactly, and what divisors look at has in dividend, so the process of division arithmetic, from dividend, deducts the process of what divisors exactly.In process relatively, at first, deduct divisor with dividend with the highest order of the lowest order alignment dividend of divisor; If enough subtracting explains to comprise 1 divisor in the dividend high position, then switch closure among the figure; From dividend, deduct divisor, on merchant's correspondence position, put 1 simultaneously; Otherwise, not comprising divisor in the dividend high position, switch is not closed, on merchant's correspondence position, puts 0.Constantly the divisor displacement is continued relatively then, when all positions all relatively finish, just accomplished merchant's calculating.It should be noted that this divider can only adapt to dividend and divisor all is the situation of positive number, is the situation of negative for dividend or divisor, needs at first it to be become positive number, and then confirms merchant's sign bit according to the sign bit of dividend and divisor.

For above-mentioned steps h, set forth the method for designing of amount of displacement d, e in the code tracking loop filter below.Fig. 6 is the digital filter configuration block diagram of code tracking loop, and its mathematic(al) representation does

y(n)＝y(n-1)+b0*x(n)+b1*x(n-1)

B0 and b1 determine by loop parameter, promptly

b0＝k1+k2

b1＝k1-k2

Wherein

$\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">k</figure-callout>}1=\frac{{\mathrm{\&omega;}}_0^2\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}{2},$ k2＝a ₂ω ₀

a2＝1.414；

T is that integration adds up the time;

ω ₀Be the loop natural circular frequency, its size is determined by loop bandwidth.

Similar with carrier wave ring wave filter method for designing, change its structure into direct II type and realize, promptly

u(n)＝x(n)+u(n-1)

y(n)＝(k1+k2)*u(n)+(k1-k2)*u(n-1)

＝k1*[x(n)+2*u(n-1)]+k2*x(n)

Sign indicating number ring NCO also adopts the Nbit accumulator to realize.For sign indicating number ring NCO gain, its unit is code persecond per unit, and meaning is 1 unit how many chips on the represents physical in 1 second of every control, promptly

$K=\frac{f_s}{2^N}$

The code frequency control word that feeds back to related channel program does

z(n)＝y(n)/K＝k1/K*[x(n)+2*u(n-1)]+k2/K*x(n)

＝h1*[x(n)+2*u(n-1)]+h2*x(n)

H1 and h2 are approximately 2 integral number power, so just can realize multiply operation through the mode of displacement.The sign indicating number ring wave filter implementation that obtains at last does

u(n)＝x(n)+u(n-1)

z(n)＝[x(n)＜＜d]+[u(n-1)＜＜(d+1)]+[x(n)＜＜e]

Wherein d, e are meant the quantity of displacement, and its size is determined by loop parameter.Move to left for representing correct time, represent to move to right when negative.

The output z (n) of sign indicating number ring wave filter adds carrier wave ring wave filter output z (n) divided by the carrier wave auxiliary parameter that scale factor obtains, and adds the corresponding frequency control word f of yard intermediate frequency _c/ f _s2 ^N, be the frequency control word that feeds back to sign indicating number ring NCO.

Be example with the gps system below, provide the design example of loop filter amount of displacement.Suppose that GPS receiver sample rate is fs=5MHz, the integration time of adding up is T=1ms, and carrier wave NCO is N=32bit with sign indicating number NCO bit wide.At first provide the design example of carrier wave ring wave filter.

The hypothesis loop bandwidth Design is Bn=15Hz, then ω ₀=B _n/ 0.7845=38.241 calculates h1, h2 and h3 then and obtains

$\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">h</figure-callout>}1=\frac{{\mathrm{\&omega;}}_0^3{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{4}\&CenterDot;\frac{2^N}{f_s\&CenterDot;2\mathrm{\&pi;}}=0.24$

$\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">h</figure-callout>}2=\frac{a_3{\mathrm{\&omega;}}_0^2\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}{2}\&CenterDot;\frac{2^N}{f_s\&CenterDot;2\mathrm{\&pi;}}=27.49$

$h3=b_3{\mathrm{\&omega;}}_0\&CenterDot;\frac{2^N}{f_s\&CenterDot;2\mathrm{\&pi;}}=6273.64$

H1, h2 and h3 are similar to 2 integral number power, even h1=1/4, h2=32, h3=8192, anti-then throw-out collar road coefficient calculates ω by h1 ₀, then by h2 and ω ₀Calculate a ₃, by h3 and ω ₀Calculate b ₃, at last by a ₃, b ₃And ω ₀Calculate the loop bandwidth B _n, promptly

${\mathrm{\&omega;}}_0={(\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">h</figure-callout>}1\&CenterDot;\frac{4}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}\&CenterDot;\frac{f_s\&CenterDot;2\mathrm{\&pi;}}{2^N})}^{\frac{1}{3}}=19.41$

$a_3=\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">h</figure-callout>}2\&CenterDot;\frac{2}{{\mathrm{\&omega;}}_0^{2}T}\&CenterDot;\frac{f_s\&CenterDot;2\mathrm{\&pi;}}{2^N}=1.24$

$b_3=h3\&CenterDot;\frac{1}{{\mathrm{\&omega;}}_0}\&CenterDot;\frac{f_s\&CenterDot;2\mathrm{\&pi;}}{2^N}=3.09$

$B_n=\frac{{\mathrm{\&omega;}}_0(a_3{b}_3^2+a_3^2-b_3)}{4(a_3{b}_3-1)}=17.62$

Since h1, h2 and h3 have been got approximate, so all parameters are all different with in advance design load.Parameter a ₃And b ₃Though be not design in advance 1.1 and 2.4, its value also relatively near design load, just can influence the transient response of loop, and is little to the steady track performance impact of loop.Loop bandwidth is more bigger than design load, can increase a little noises, but can change through revising h1, h2 and h3.Following table has been listed h1, h2 and the h3 of various combination, corresponding loop parameter and amount of displacement.

The method for designing of sign indicating number ring and carrier wave lopps are seemingly.The hypothesis loop bandwidth Design is Bn=1Hz, then ω ₀=B _n/ 0.53=1.89 calculates h1 then and h2 obtains

$\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">h</figure-callout>}1=\frac{{\mathrm{\&omega;}}_0^2\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">T</figure-callout>}}{2}\&CenterDot;\frac{2^N}{f_s}=1.53$

$\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">h</figure-callout>}2=a_2{\mathrm{\&omega;}}_0\&CenterDot;\frac{2^N}{f_s}=2291.73$

H1 and h2 are similar to 2 integral number power, even h1=1, h2=2048, anti-then throw-out collar road coefficient calculates ω by h1 ₀, then by h2 and ω ₀Calculate a ₂, at last by a ₂And ω ₀Calculate the loop bandwidth B _n, promptly

${\mathrm{\&omega;}}_0={(\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00033.png"\; state="\{\{state\}\}">h</figure-callout>}1\&CenterDot;\frac{2}{T}\&CenterDot;\frac{f_s}{2^N})}^{\frac{1}{2}}=1.53$

$a_2=\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H2009100804609E00021.png,H2009100804609E00041.png"\; state="\{\{state\}\}">h</figure-callout>}2\&CenterDot;\frac{1}{{\mathrm{\&omega;}}_0}\&CenterDot;\frac{f_s}{2^N}=1.56$

$B_n=\frac{{\mathrm{\&omega;}}_0(1+a_2^2)}{{4a}_2}=0.84$

Following table has been listed the h1 and the h2 of various combination, corresponding loop parameter and amount of displacement.

The present invention compared with prior art, maximum characteristics are that all operations all are reduced to a series of displacements and add operation in the whole loop control procedure, and through the choose reasonable bit wide, do not lose tracking accuracy basically.This makes the realization of loop control can adopt the very processor of low side, perhaps can also realize with the direct hardware of hardware description language.Operand is low so the present invention has, and implementation is simple, does not influence the advantage of loop tracks precision.

Claims (3)

1. one kind based on the displacement and the fixed point loop control method of addition, comprises step:

A. correlator is accomplished and is exported 6 accumulation results after integration adds up, and the loop control module realizes the control to carrier tracking loop and code tracking loop according to these 6 accumulation results; 6 accumulation results are the leading (I of homophase _E), the instant (I of homophase _P), the homophase (I that lags behind _L), the leading (Q of quadrature _E), the instant (Q of quadrature _P), the quadrature (Q that lags behind _L);

B. adopt rotation of coordinate numerical calculation Cordic algorithm to realize two quadrant arc tangent atan, accomplish the work of carrier wave ring phase discriminator, i.e. atan (Q _P/ I _P), form carrier wave ring phase demodulation error x (n), wherein I _PFor homophase instant, Q _PFor quadrature instant;

C. to carrier wave ring phase demodulation error x (n), carrier wave ring intermediate variable u (n-1) and u (n-2), after suitable displacement and add operation, realize the carrier wave ring wave filter, form carrier wave ring wave filter output z (n) and new carrier wave ring intermediate variable u (n);

D. carrier wave ring wave filter output z (n) adds carrier wave IF-FRE control word, forms new carrier frequency control word, feeds back to track loop the carrier wave ring is controlled;

E. upgrade carrier wave ring intermediate variable, use for loop control next time, so far, the control of carrier wave ring loop is accomplished;

F. adopt JPL algorithm computation envelope; Accomplish respectively the lead and lag calculating with envelope that adds up; Promptly forming the wherein said JPL algorithm of

, is the method by the calculating envelope of U.S. jet propulsion laboratory JPL proposition;

G. adopt based on the displacement and the binary division module of addition and accomplish the phase discriminator work that sign indicating number encircles, generated code ring phase demodulation error x ' (n), promptly

$\frac{1}{2}\&CenterDot;\frac{E-L}{E+L};$

H. to sign indicating number ring phase demodulation error x ' (n), sign indicating number ring intermediate variable u ' (n-1), through after suitable displacement and the add operation, realize a sign indicating number ring wave filter, generated code ring wave filter output z ' (n) encircles intermediate variable u ' (n) with new sign indicating number;

I. sign indicating number ring wave filter output z ' (n) adds that carrier wave ring wave filter output z (n) divided by the carrier wave auxiliary parameter that scale factor obtains, adds a yard IF-FRE control word, forms new code frequency control word, feeds back to track loop the sign indicating number ring is controlled;

J. upgrade sign indicating number ring intermediate variable, use for loop control next time, so far, the control of sign indicating number ring loop is accomplished.

2. the method for claim 1; It is characterized in that: in step c, the carrier wave ring wave filter is three rank filters, adopts direct II type to realize; And filter coefficient and digital controlled oscillator NCO gain taken all factors into consideration; Be approximately 2 integral number power, adopt displacement to realize, amount of displacement is according to the loop bandwidth decision of design.

3. the method for claim 1; It is characterized in that: in step h, the sign indicating number ring wave filter is a second order filter, adopts direct II type to realize; And filter coefficient and digital controlled oscillator NCO gain taken all factors into consideration; Be approximately 2 integral number power, adopt displacement to realize, amount of displacement is according to the loop bandwidth decision of design.

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