CN101969353A - Method for generating spread spectrum code in satellite navigation system - Google Patents

Abstract

The invention provides a method for generating a spread spectrum code in a satellite navigation system in the technical field of information processing. In the method, a spread spectrum code is subject to Legendre sequence generation processing and Weil sequence generation processing to acquire a spread spectrum code sequence, and the spread spectrum code sequence is subject to judgment of even cross-correlation and odd cross-correlation to acquire a required spread spectrum sequence. Based on the Weil sequence generation spread spectrum code, the method realizes the requirement of the satellite navigation system to the spread spectrum code, and has the advantages of great number of generation code sequences and good cross-correlation character of the sequence.

Description

The generation method of spreading code in the satellite navigation system

Technical field

What the present invention relates to is a kind of method of technical field of information processing, specifically is the generation method of spreading code in a kind of satellite navigation system.

Background technology

Spreading code in the satellite navigation system signals can the enhanced navigation signal noise resisting ability, help the user to distinguish different satellites fast, therefore in the design of satellite navigation system signals system, occupy critical role.Owing to good randomness is arranged between the spreading code chip, but the generation of sign indicating number all has certain rule again, be not real completely at random, so spreading code also is pseudo noise code.C/A sign indicating number based on the gold sequence is the whole world first satellite navigation system---GPS (Global Positioning System, global positioning system) satellite navigation signals spreading code, as the spreading code of code division multiple access satellite navigation system, be used for three more than ten years so far and also continued use.The C/A sign indicating number is produced by linear feedback shift register, the generation method is simple, but has preferably negligible amounts from the spreading code of their cross correlation, and flourish along with the global navigation satellite cause on the other hand, Galileo as Europe, Muscovite GLONASS, the Compass of China, the appearance of the satellite navigation systems such as QZSS of Japan, after these systems build up, space will have a hundreds of satellite, and will be also very urgent to the quantity demand of spreading code on the satellite navigation system signals, existing spreading code sign indicating number family can not satisfy the demand, therefore generates abundant quantity and have better spreading code from their cross correlation just to seem particularly important.

Through existing literature search is found, Chinese patent application number is: 200580051474, name is called: be used for the spreading code of satellite navigation system, this technology adopts alternative manner to revise or replace the bit mode collection that does not satisfy optimisation criteria, and the spreading code set cooperation of establishment suboptimum is final spreading code.But this method should not generate on satellite in real time, needs all to be stored on the satellite in advance, has increased the satellite burden; And whole process is consuming time longer, the limited amount of the code character of generation.

Summary of the invention

The objective of the invention is to overcome above-mentioned deficiency of the prior art, the generation method of spreading code in a kind of satellite navigation system is provided, generate spreading code based on the Weil sequence, realized the demand of satellite navigation system to spreading code, One's name is legion with generated code sequence, sequence is from the good advantage of their cross correlation.

The present invention is achieved by the following technical solutions, the present invention includes following steps:

The first step, when the length q that treats spreading code was prime number, it was that the Legendre sequence of q generate to be handled and length is that the Weil sequence of q generates processing to obtain (q-1)/2 group length be the Weil sequence of q and carried out for the 3rd step that the band spreading code is carried out length;

Otherwise it is that the Legendre sequence of p generate to be handled and length is that the Weil sequence of p generates and handles that to obtain (p-1)/2 group length be the Weil sequence of p and carry out second and go on foot that the band spreading code is carried out length;

Wherein: p is the prime number nearest apart from q less than q and p.

Described Legendre sequence generates to be handled, and may further comprise the steps:

1) satisfies x ≡ y ²(modp) set that all x form is SM _p, the set that remaining x forms is SNM _p, wherein: y ∈ (1,2 ..., m), x ∈ (1,2 ..., m-1), m is a prime number;

2) as x ∈ SM _p, L (x)=1 then is as x ∈ SNM _p, L (x)=0 then, thus the Legendre sequence that length is m obtained.

Described Weil sequence generates to be handled, and may further comprise the steps:

1) be that the Legendre sequence of m moves right one and handles with length, and the Legendre sequence after will being shifted and former Legendre sequence does XOR, obtain the Weil sequence of first group of sequence length m;

2) method employing 1) is handled the Legendre sequence after the displacement, obtains the Weil sequence of second group of sequence length m;

3) constantly repeat above-mentioned steps, until the Weil sequence that obtains (m-1)/2 group sequence length m.

Second step was to take out length in the Weil sequence of p for the short sequence of (q-p) and carry out the insert division and manage in the length that the first step obtains, and to obtain p (p-1)/2 group length be the spread spectrum code sequence of q and carried out for the 3rd step.

Described insertion is handled and is meant: each length is total p insertion point in the Weil sequence of p, is that the short sequence of (q-p) is inserted each insertion point that length is the Weil sequence of p respectively with length, and obtaining p (p-1)/2 group length altogether is the spread spectrum code sequence of q.

The 3rd step, judge that each length is maximum side lobe levels of spread spectrum code sequence idol auto-correlation and the maximum side lobe levels of strange auto-correlation of q, with the maximum side lobe levels of even auto-correlation smaller or equal to threshold value T1 and the maximum side lobe levels of strange auto-correlation smaller or equal to the spread spectrum code sequence of threshold value T2 as alternative sequence.

The maximum side lobe levels of described strange auto-correlation obtains in the following manner:

1) basis

τ ∈ (1,2 ..., q-1), computational length is the strange autocorrelation value of the spread spectrum code sequence of q, obtains (q-1) individual strange autocorrelation value, wherein: q is a sequence length, a _iBe the i position of sequence, a _{I+ τ}Represent ((i+ τ) modq) position of sequence, τ is the figure place that sequence moves right;

2) basis

Obtain q-1 strange auto-correlation side lobe levels, maximum is exactly the maximum side lobe levels of strange auto-correlation in q-1 the strange auto-correlation side lobe levels.

The maximum side lobe levels of described even auto-correlation obtains in the following manner:

1) basis

τ ∈ (1,2 ..., q-1), computational length is the even autocorrelation value of the spread spectrum code sequence of q, obtains (q-1) individual even autocorrelation value, wherein: q is a sequence length, a _iBe the i position of sequence, a _{I+ τ}Represent ((i+ τ) modq) position of sequence, τ is the figure place that sequence moves right;

2) basis

Obtain q-1 even auto-correlation side lobe levels, maximum is exactly the maximum side lobe levels of even auto-correlation in q-1 the even auto-correlation side lobe levels.

The 4th step, selecting the n group length from alternative sequence is the spread spectrum code sequence of q and maximum side lobe levels of even cross-correlation between the wherein per two groups of frequency expansion sequences of calculating and the maximum side lobe levels of strange cross-correlation, when the maximum side lobe levels of all even cross-correlation that obtain all equaled threshold value T4 less than the person smaller or equal to threshold value T3 and all maximum side lobe levels of strange cross-correlation, the spread spectrum code sequence that described n group length is q was for treating frequency expansion sequence; Otherwise the spread spectrum code sequence that to reselect other n group length be q, wherein: n is the group number of required frequency expansion sequence.

Compared with prior art, the invention has the beneficial effects as follows: the quick generation method that a kind of Weil sequence is provided, by to inserting under the short sequence condition target sequence from the computational analysis of cross-correlation side lobe levels, reduce the redundancy object sequence and generate quantity, the cross-correlation test search of alternative sequence is very beneficial for determining fast of cross-correlation secondary lobe threshold value.

Description of drawings

Fig. 1 Weil sequence generating principle figure.

Fig. 2 spread spectrum code sequence generating principle figure.

Insert 4 kinds of maximum side lobe levels under the different short sequence set in Fig. 3 k=1 Weil sequence relatively.

Insert 4 kinds of maximum side lobe levels under the different short sequence set in Fig. 4 k=510 Weil sequence relatively.

The maximum side lobe levels of 520170 groups of spread spectrum code sequence odd evens of Fig. 5 auto-correlation.

Fig. 6 w=111, the odd even cross-correlation between p=258 alternative sequence and other alternative sequence.

Embodiment

Below embodiments of the invention are elaborated, present embodiment is being to implement under the prerequisite with the technical solution of the present invention, provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

As Fig. 1-shown in Figure 2, present embodiment may further comprise the steps:

The first step, when the length q that treats spreading code was prime number, carrying out length was the Legendre sequence generation processing of q and the Weil sequence generation processing that length is q, obtains the Weil sequence that (q-1)/2 group length is q, directly carries out for the 3rd step;

Otherwise carrying out length is the Legendre sequence generation processing of p and the Weil sequence generation processing that length is p, obtains the Weil sequence that (p-1)/2 group length is p, and wherein: p is the prime number nearest apart from q less than q and p, carries out second and goes on foot.

1023 is not prime number in the present embodiment, need to select from 1023 nearest prime numbers 1021, and it is 1021 Weil sequence that Mr. becomes length.

Described Legendre sequence generates to be handled, and may further comprise the steps:

1) satisfies x ≡ y ²(modp) set that all x form is SM _p, the set that remaining x forms is SNM _p, wherein: y ∈ (1,2 ..., m), x ∈ (1,2 ..., m-1), m is a prime number;

2) as x ∈ SM _p, L (x)=1 then is as x ∈ SNM _p, L (x)=0 then, thus the Legendre sequence that length is m obtained.

In the present embodiment: when x=1, have y=1, make (1 ²-1)/and 1021=0, so 1 ∈ SM ₁₀₂₁

When x=3, there is y=32, make (32 ²-3)/and 1021=1, so 3 ∈ SM ₁₀₂₁

When x=4, there is y=2, make (2 ²-4)/and 1021=0, so 4 ∈ SM ₁₀₂₁

When x=5, there is y=106, make (106 ²-5)/and 1021=11, so 5 ∈ SM ₁₀₂₁

And work as x=2, during x=6, there is not y, y ∈ (1,2 ..., 1023), feasible (y ²-x)/1021 the result is an integer, therefore, and (2,6) ∈ SNM ₁₀₂₁

2) contrast (1,2 ..., 6) under set, the sequence first six digits is, 101110, the sequence front adds one 0 again, the result is 0101110.

3) get (7,8, ..., 1020), and repeat 1) and 2), obtain that (the Legendre sequence is shown with 8 system numerical tables shown in the Legendre sequence table 1 of 1021 length, from left to right, deposit successively line by line from top to bottom, list 1023 values in the table altogether, need ignore preceding two ' 0 ', therefore preceding 7 values of sequence of 056 representative are 0101110).

Table 1

Described Weil sequence generates to be handled, and may further comprise the steps:

1) be that the Legendre sequence of m moves right one and handles with length, and the Legendre sequence after will being shifted and former Legendre sequence does XOR, obtain the Weil sequence of first group of sequence length m;

2) method employing 1) is handled the Legendre sequence after the displacement, obtains the Weil sequence of second group of sequence length m;

3) constantly repeat above-mentioned steps, until the Weil sequence that obtains (m-1)/2 group sequence length m.

Present embodiment moves right 1 with the Legendre sequence in the table 1 earlier, generates the 1st Weil sequence;

A) the 1021st of Legendre sequence is put into the 1st of new sequence, and the 1st, 2 ..., 1020 are put into new sequence 2,3 successively ..., 1021, preceding 6 that generate new sequence is 101011;

The XOR that 1021 new sequences that b) will generate and former Legendre sequence are done bit-by-bit obtains the 1st Weil sequence, and generating preceding 6 of Weil sequence is 111101.

Then the Legendre sequence in the table 1 is moved right 2, generate the 2nd Weil sequence;

C) the 1020th, 1021 of Legendre sequence is put into the 1st, 2 of new sequence, and the 1st, 2 ..., 1019 are put into new sequence 3,4 successively ..., 1021, preceding 6 that generate new sequence is 011011;

The XOR that 1021 new sequences that d) will generate and former Legendre sequence are done bit-by-bit obtains the 2nd Weil sequence, and generating preceding 6 of Weil sequence is 111101.

Then getting mobile figure place successively is 3,4 ... 510, thus obtain the 3rd, 4 ... 510 Weil sequences;

Second step chose at random in the length that the first step obtains is the Weil sequence of p wherein that length is the short sequence of (q-p), and inserted processing, and obtaining p. (p-1)/2 group length is the spread spectrum code sequence of q, carries out for the 3rd step.

Described insertion is handled, and is: each length is total p insertion point in the Weil sequence of p, is that the short sequence of (q-p) is inserted each insertion point that length is the Weil sequence of p respectively with length, and obtaining p. (p-1)/2 group length altogether is the spread spectrum code sequence of q.

The Weil sequence length is 1021 in the step (1), is 2 apart from spread spectrum code sequence length 1023, and therefore short sequence length is 2, and short sequence has 4 kinds may make up, i.e. [00], and [01], [10], [11] need to determine to insert short sequence from 4 kinds of combinations.

The short sequence of described definite insertion, step is as follows:

1) note Weil sequence sequence number is w, w ∈ (1,2 ..., 510), the position, insertion point is p, p ∈ (1,2 ..., 1021);

2) in w=1 Weil sequence, insert short sequence;

Described inserting step is as follows:

A) during the p=1 of position, insertion point, short sequence [00] is put into the 1st, 2 of spread spectrum code sequence, 1 to 1021 of Weil sequence is put into 3 to 1023 of spread spectrum code sequence, obtains one 1023 length sequences;

B) p=2 of position, insertion point the time, the 1st the 1st of being put into spread spectrum code sequence of Weil sequence, short sequence [0 0] is put into the 2nd, 3 of spread spectrum code sequence, 2 to 1021 4 to 1023 of being put into spread spectrum code sequence of Weil sequence obtain one 1023 length sequences;

C) allow all insertion point p=(1,2 ..., 1021) repeating step b), obtain 1021 group of 1023 length spread spectrum code sequence.

3) successively [01], [10], [11] are by 2) method insert, promptly obtain 3 * 1023 groups of spread spectrum code sequences.

4) utilize in the specification 7), 8), 9) description of step, calculate 2 respectively) and 3) in the idol of 4 * 1021 groups of spread spectrum code sequences, the maximum side lobe levels of strange auto-correlation;

5) according to 1021 insertion point p, obtain 4 respectively) in 4 different short combined sequence generate spread spectrum code sequence at place, identical insertion point even auto-correlations, minimum and maximum values of the maximum side lobe levels of strange auto-correlation inserted;

6) in like manner, repeating step 2) to 5), draw in the w=510Weil sequence, insert the even auto-correlation that 4 different short combined sequence generate spread spectrum code sequence, the minimum and maximum value of the maximum side lobe levels of strange auto-correlation at place, identical insertion point;

7) draw 5 respectively) and 6) in obtain the figure of numerical value, from Fig. 3 and Fig. 4, find out at the maximin curve of 4 the maximum side lobe levels in 1021 insertion points very approaching, so it is very little to the formation sequence properties influence to insert short sequence various combination.

8) from the sequence balance, getting and inserting short sequence is [10].

In the 3rd step, generation length is 1023 spread spectrum code sequence

Described generation length is 1023 spread spectrum code sequence, and step is as follows:

1) get the short sequence [01] of insertion, according to 2 in second step), 1021 groups of spread spectrum code sequences of generation w=1Weil sequence;

2) get successively w=(2,3 ..., 510) the Weil sequence, repeating step 1), obtain the Weil sequence of 509 * 1021 group of 1023 length altogether;

3) comprehensive 1) and 2), the result obtains the spread spectrum code sequence of 510 * 1021=520710 group.

The 4th step is to the optimization of 1023 length spread spectrum code sequences

Described spread spectrum code sequence optimization comprises the steps:

1) note Weil sequence sequence number is w, w ∈ (1,2 ..., 510), the position, insertion point is p, p ∈ (1,2 ..., 1021), be 1023 spread spectrum code sequence generative process by length in the 3rd step, each spread spectrum code sequence is by w as can be known, and two parameters of p are determined;

2) utilize formula (1) and (2) to calculate w=1, the even autocorrelation value of p=1 spread spectrum code sequence, strange autocorrelation value

The idol auto-correlation: $\underset{i=1}{\overset{1023-\mathrm{\τ}}{\mathrm{\Σ}}}{a}_i{a}_{i+\mathrm{\τ}}+\underset{i=1023-\mathrm{\τ}+1}{\overset{1023}{\mathrm{\Σ}}}{a}_i{a}_{i+\mathrm{\τ}},\mathrm{\τ}\∈(\mathrm{1,2}...,1023-1)---\left(1\right)$

Strange auto-correlation: $\underset{i=1}{\overset{1023-\mathrm{\τ}}{\mathrm{\Σ}}}{a}_i{a}_{i+\mathrm{\τ}}-\underset{i=1023-\mathrm{\τ}+1}{\overset{1023}{\mathrm{\Σ}}}{a}_i{a}_{i+\mathrm{\τ}},\mathrm{\τ}\∈(\mathrm{1,2}...,1023-1)---\left(2\right)$

Wherein, a _iBe the i position of sequence, a _{I+ τ}Represent ((i+ τ) mod1023) position of sequence, τ is the sequence figure place that moves right;

The calculating of above-mentioned formula (1) and (2) comprises the steps:

A) get shift count τ=1, with w=1, the p=1 spread spectrum code sequence is substitution formula (1) and (2) respectively, obtains an antithesis, strange autocorrelation value-1,1;

B) get successively τ ∈ (2,3 ..., 1023-1), and repeat step a), obtain (1023-2) antithesis, strange autocorrelation value.

2) with 1) in the 1023-1 antithesis that obtains, strange autocorrelation value substitution formula (3) is scaled the 1023-1 antithesis, strange auto-correlation side lobe levels.

Unit is dB;

3) calculate 2 respectively) in the maximum of 1023-1 even auto-correlation and strange auto-correlation side lobe levels, the result be-19dB-17.3dB, these two idols that maximum is respectively this sequence, strange auto-correlation maximum side lobe levels.

4) repeating step 1), 2), 3), calculate the idol of all spread spectrum code sequences that the 3rd step generated, the maximum side lobe levels of strange auto-correlation obtains 1021. (1021-1)/2 antithesis, the maximum side lobe levels of strange auto-correlation, as shown in Figure 5;

5) analyze 4) in the idol of 1021. (1021-1)/2 pair spread spectrum code sequences, the maximum side lobe levels of strange auto-correlation is determined even auto-correlation respectively, the screening threshold value of the maximum side lobe levels of strange auto-correlation be-23.9dB and-20dB;

6) screening threshold value contrast 5), an antithesis auto-correlation of each sequence correspondence, the maximum side lobe levels of strange auto-correlation respectively with-23.9dB and-the 20dB contrast, eliminate even auto-correlation greater than after-23.9dB or the maximum side lobe levels of strange auto-correlation the sequence greater than-20dB, obtain 55 groups of sequences, and as alternative sequence;

7) utilize formula (4) and (5) to calculate 6) obtain w=111 in the alternative sequence, p=258 and w=112, the idol between two sequences of p=182, strange cross correlation value,

The idol cross-correlation: $\underset{i=1}{\overset{1023-\mathrm{\τ}}{\mathrm{\Σ}}}{a}_i{b}_{i+\mathrm{\τ}}+\underset{i=1023-\mathrm{\τ}+1}{\overset{1023}{\mathrm{\Σ}}}{a}_i{b}_{i+\mathrm{\τ}},\mathrm{\τ}\∈(\mathrm{1,2}...,1023)---\left(4\right)$

Strange cross-correlation: $\underset{i=1}{\overset{1023-\mathrm{\τ}}{\mathrm{\Σ}}}{a}_i{b}_{i+\mathrm{\τ}}-\underset{i=1023-\mathrm{\τ}+1}{\overset{1023}{\mathrm{\Σ}}}{a}_i{b}_{i+\mathrm{\τ}},\mathrm{\τ}\∈(\mathrm{1,2}...,1023)---\left(5\right)$

Wherein, a _i, b _iBe respectively the i position of two sequences, b _{I+ τ}Represent ((i+ τ) mod1023) position of sequence, τ is the sequence figure place that moves right;

The calculating of above-mentioned formula (4) and (5) comprises the steps:

A) get shift count τ=1,, obtain an antithesis, strange cross correlation value-1 ,-1 two alternative sequence difference substitution formula (4) and (5);

B) get successively τ ∈ (2,3 ..., 1023), and repeat step a), obtain (1023-1) antithesis, strange cross correlation value.

8) with 7) in 1023 antithesis that obtain, strange autocorrelation value substitution 2) in formula (3), be scaled 1023 antithesis, strange cross-correlation side lobe levels;

9) calculate 8 respectively) in the maximum of 1023 even cross-correlation and strange cross-correlation side lobe levels, the result be-20.5dB and-19.4dB, these two idols that maximum is two sequences, strange cross-correlation maximum side lobe levels;

10) repeating step 7), 8), 9), calculate w=111, p=258 alternative sequence and 6) in the idol of other 52 groups of alternative sequence, the maximum side lobe levels of strange cross-correlation, as shown in Figure 6, last surface curve be very to be correlated with, following surface curve is even being correlated with;

11) w=111 that obtains analysis 10), p=258 alternative sequence and 6) idol of other all alternative sequence in, the maximum side lobe levels of strange cross-correlation, thereby determine respectively-18dB and-two values of 17.2dB are as idol, the maximum side lobe levels threshold value of strange cross-correlation, and setting selection number of times is 30;

12) establish desire from 6) obtain 19 groups of sequences in 55 groups of alternative sequence;

13) select 19 groups of sequences in 55 groups of alternative sequence, select 19 groups of sequences at random, sequence numbering is (1,2,3,4,7,8,11,12,15,23,26,27,32,33,44,45,46,52);

14) repeating step 7) to 9), calculating 13) provide 19 groups of sequences idol between any two, the maximum side lobe levels of strange cross-correlation, find that the maximum side lobe levels of even cross-correlation is-16.9dB between the sequence numbering 1 and 3, greater than the maximum side lobe levels threshold value-18dB of even cross-correlation, therefore get rid of this combination, and get back to 13) reselect different combined sequence;

15) obtain 19 groups of idols after selecting 17 times, the maximum side lobe levels of strange cross-correlation all is not more than the spread spectrum code sequence of threshold value in twos; 19 groups of spread spectrum code sequences that obtain are provided by parameter w and p, as following table 2

Table 2 generates 19 groups of spread spectrum code sequence parameter lists.

Sequence number	Weil sequence number (w)	Insertion point (p)	Sequence number	Weil sequence number (w)	Insertion point (p)
						1	111	258	11	364	114
2	112	182	12	373	55
						3	168	144	13	410	126
4	175	206	14	455	589
						5	176	163	15	476	9
6	217	151	16	481	457
						7	254	104	17	483	502
8	269	131	18	497	21
						9	350	100	19	502	1008
10	360	590

19 groups of spread spectrum code sequences that table 3 generates contrast with the spread spectrum code sequence characteristic of GPS C/A sign indicating number.

Characteristic	GPS?C/A	19 groups of sequences
			Idol auto-correlation (dB)	-23.9	-23.9
Strange auto-correlation (dB)	-19.9	-20
			Idol cross-correlation (dB)	-60.1	-18
Strange cross-correlation (dB)	-19.7	-17.2

As seen from Table 3, the spread spectrum code sequence autocorrelation performance of generation slightly is better than GPS C/A sign indicating number, and cross-correlation is poor slightly.

Claims (6)

1. the generation method of spreading code in the satellite navigation system is characterized in that, may further comprise the steps:

The first step, when the length q that treats spreading code was prime number, it was that the Legendre sequence of q generate to be handled and length is that the Weil sequence of q generates processing to obtain (q-1)/2 group length be the Weil sequence of q and carried out for the 3rd step that the band spreading code is carried out length;

Otherwise it is that the Legendre sequence of p generate to be handled and length is that the Weil sequence of p generates and handles that to obtain (p-1)/2 group length be the Weil sequence of p and carry out second and go on foot that the band spreading code is carried out length;

Wherein: p is the prime number nearest apart from q less than q and p,

Second step was to take out length in the Weil sequence of p for the short sequence of (q-p) and carry out the insert division and manage in the length that the first step obtains, and to obtain p (p-1)/2 group length be the spread spectrum code sequence of q and carried out for the 3rd step,

The 3rd step, judge that each length is maximum side lobe levels of spread spectrum code sequence idol auto-correlation and the maximum side lobe levels of strange auto-correlation of q, with the maximum side lobe levels of even auto-correlation smaller or equal to threshold value T1 and the maximum side lobe levels of strange auto-correlation smaller or equal to the spread spectrum code sequence of threshold value T2 as alternative sequence

The 4th step, selecting the n group length from alternative sequence is the spread spectrum code sequence of q and maximum side lobe levels of even cross-correlation between the wherein per two groups of frequency expansion sequences of calculating and the maximum side lobe levels of strange cross-correlation, when the maximum side lobe levels of all even cross-correlation that obtain all equaled threshold value T4 less than the person smaller or equal to threshold value T3 and all maximum side lobe levels of strange cross-correlation, the spread spectrum code sequence that described n group length is q was for treating frequency expansion sequence; Otherwise the spread spectrum code sequence that to reselect other n group length be q, wherein: n is the group number of required frequency expansion sequence.

2. the generation method of spreading code is characterized in that in the satellite navigation system according to claim 1, and described Legendre sequence generates to be handled, and may further comprise the steps:

1) satisfies x ≡ y ²(modp) set that all x form is SM _p, the set that remaining x forms is SNM _p, wherein: y ∈ (1,2 ..., m), x ∈ (1,2 ..., m-1), m is a prime number;

2) as x ∈ SM _p, L (x)=1 then is as x ∈ SNM _p, L (x)=0 then, thus the Legendre sequence that length is m obtained.

3. the generation method of spreading code is characterized in that in the satellite navigation system according to claim 1, and described Weil sequence generates to be handled, and may further comprise the steps:

1) be that the Legendre sequence of m moves right one and handles with length, and the Legendre sequence after will being shifted and former Legendre sequence does XOR, obtain the Weil sequence of first group of sequence length m;

2) method employing 1) is handled the Legendre sequence after the displacement, obtains the Weil sequence of second group of sequence length m;

3) constantly repeat above-mentioned steps, until the Weil sequence that obtains (m-1)/2 group sequence length m.

4. the generation method of spreading code in the satellite navigation system according to claim 1, it is characterized in that, described insertion is handled and is meant: each length is total p insertion point in the Weil sequence of p, length is inserted each insertion point that length is the Weil sequence of p respectively for the short sequence of (q-p), and obtaining p (p-1)/2 group length altogether is the spread spectrum code sequence of q.

5. the generation method of spreading code is characterized in that in the satellite navigation system according to claim 1, and the maximum side lobe levels of described strange auto-correlation obtains in the following manner:

1) basis

τ ∈ (1,2 ..., q-1), computational length is the strange autocorrelation value of the spread spectrum code sequence of q, obtains (q-1) individual strange autocorrelation value, wherein: q is a sequence length, a _iBe the i position of sequence, a _{I+ τ}Represent ((i+ τ) modq) position of sequence, τ is the figure place that sequence moves right;

2) basis

Obtain q-1 strange auto-correlation side lobe levels, maximum is exactly the maximum side lobe levels of strange auto-correlation in q-1 the strange auto-correlation side lobe levels.

6. the generation method of spreading code is characterized in that in the satellite navigation system according to claim 1, and the maximum side lobe levels of described even auto-correlation obtains in the following manner:

1) basis

τ ∈ (1,2 ..., q-1), computational length is the even autocorrelation value of the spread spectrum code sequence of q, obtains (q-1) individual even autocorrelation value, wherein: q is a sequence length, a _iBe the i position of sequence, a _{I+ τ}Represent ((i+ τ) modq) position of sequence, τ is the figure place that sequence moves right;

2) basis

Obtain q-1 even auto-correlation side lobe levels, maximum is exactly the maximum side lobe levels of even auto-correlation in q-1 the even auto-correlation side lobe levels.

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