CN101509968A - High dynamic high precision intermediate frequency simulation satellite signal generating method - Google Patents

Abstract

The invention relates to a method for generating medium-frequency satellite signals with high dynamic situation and high precision, and the method comprises the following steps: 1) parameters of a radio-frequency carrier are received, including the initial pseudo distance, the speed, the acceleration and the jerk; 2) the carrier phase with high precision and including Doppler frequency shift is generated by a method of three-phase carrier phase accumulation; 3) a medium-frequency carrier signal is obtained after carrier phase truncation by searching sine and cosine tables; 4) parameters of a ranging code are received, including the initial pseudo distance, the speed, the acceleration and the jerk; 5) a code clock with high precision is generated by a method of three-phase code phase accumulation; 6) under the action of the code clock, I-path and Q-path spreading codes are generated; 7) I-path and Q-path navigation messages are read and binary addition is carried out with the spreading codes; 8) the spreading codes are molded, filtered and modulated onto the medium carrier; 9) power control and digital-to-analog conversion are carried out to the spreading signals, thus obtaining the medium-frequency analogue satellite signals. The method has the advantages of simple structure, smooth speed without step and high precision.

Description

High dynamic high precision intermediate frequency simulation satellite signal generating method

Technical field

The present invention relates to a kind of satellite signal generating method, more particularly, relate to a kind of high dynamic high precision intermediate-freuqncy signal production method that is used for the satellite-signal simulation.

Background technology

High dynamic satellite signal simulator is the satellite-signal that receives of analog carrier accurately, and is powerful as a kind of high-precision testing apparatus, uses very extensive in civilian and national defence scientific experimentation field.Its typical use comprises the acquisition performance of the high dynamic signal of analog satellite emission with test receiver, as the dynamic measurement precision of ratio of precision than the standard test receiver, and design specific signal confirmatory measurement scheme etc.In recent years, autonomous navigation positioning system is progressively set up in China's beginning, and is in continuous development and the every performance index of raising system, also more and more higher to the requirement of satellite-signal simulation and test.Therefore the development of high-performance satellite signal simulator has very important realistic meaning to the satellite navigation system of developing China.The intermediate-freuqncy signal production method of high dynamic high precision wherein is one of development satellite signal simulator gordian technique that need solve.

At present, the satellite signal simulator of BJ University of Aeronautics ﹠ Astronautics's development utilizes the software wireless method for electrically, has set up the mathematical model that the satellite signal simulator intermediate-freuqncy signal is handled.This method is by carrying out 4 times of interpolations, digital filtering to digital baseband modulation signal, D/A (Digital/Analog) conversion and analog filtering are realized the frequency transformation of intermediate-freuqncy signal, obtain the intermediate frequency satellite-signal.When Doppler simulation, adopt the Doppler simulation algorithm of full coherent, the range difference of moving target in the sampling interval is become the neighbouring sample phase differential of pseudo-code and carrier wave constantly, adding up by recursion obtains the pseudo-code phase and the carrier phase of next sampling instant.System adopts the digital carrier structural principle of traditional frequency ladder stepping based on Direct Digital Frequency Synthesizers (DDS) to generate digital carrier, and it is output as a linear FM signal.In the speed cycle that ladder temporal logic unit comes controlled variable to refresh according to the time step control word of input, the change information of frequency represented in frequency step Variable Control word, thereby make the digital carrier of generation have multidate informations such as speed and acceleration.This method can be finished the required basic function of test receiver under certain precision, have certain dynamic property, but the real high-precision signal simulation of distance still has certain distance.Its major defect is: adopt 4 times zero interpolations to produce the signal of upper frequencies, and each secondary mirror frequency component of back tape splicing bandpass filter filtering, this method work clock is lower, and complex structure has reduced the simulation precision of signal.Adopt single order Direct Digital frequency synthesis (DDS) model, come emulation to have the signal of acceleration and acceleration by renewal speed parameter in the time interval, this method causes speed to have rank more, can only increase simulation accuracy by shortening the parameter update time interval.

Therefore, the intermediate frequency satellite signal generating method that needs a kind of high dynamic high precision.

Summary of the invention

The technical problem to be solved in the present invention is the above-mentioned deficiency that overcomes existing method, and a kind of intermediate frequency satellite signal generating method of high dynamic high precision is provided.

In order to achieve the above object, the present invention comprises as the lower part:

(1) parameter of received RF carrier wave comprises initial pseudo, speed, acceleration and acceleration;

(2) method that adds up by three rank carrier phases produces the high-precision carrier phase that comprises Doppler shift; It is to be that the DDS model carries out three-stage cascade and obtains with traditional single order Direct Digital frequency synthesis that three rank carrier phases add up, the corresponding first order DDS of initial pseudo and speed wherein, the corresponding second level DDS of acceleration, the corresponding third level DDS of acceleration; Under the clock effect, carrier wave acceleration totalizer (third level DDS) adds up to acceleration, obtains the acceleration sequence, obtains the instantaneous acceleration value after this sequence and the addition of acceleration initial value; In like manner, carrier wave acceleration accumulator (second level DDS), instantaneous acceleration added up obtains velocity series, obtains the instantaneous velocity value after this sequence and the addition of speed initial value; Carrier wave speed totalizer (first order DDS) adds up to instantaneous velocity, obtains the carrier phase sequence, obtains the instantaneous carrier phase value after this sequence and the initial pseudo addition;

(3) look into sine after carrier phase is blocked, cosine table obtains intercarrier signal;

(4) parameter of reception ranging code comprises initial pseudo, speed, acceleration and acceleration parameter;

(5) adopt the phase-accumulated method of three exponents to produce high-precision sign indicating number clock; The phase-accumulated method of three exponents obtains traditional DDS cascade; The corresponding first order DDS of initial pseudo and speed wherein, the corresponding second level DDS of acceleration, the corresponding third level DDS of acceleration; Sign indicating number acceleration totalizer (third level DDS) adds up to acceleration, obtains the acceleration sequence, obtains the instantaneous acceleration value after this sequence and the addition of acceleration initial value; In like manner, sign indicating number acceleration accumulator (second level DDS), instantaneous acceleration added up obtains velocity series, obtains the instantaneous velocity value after this sequence and the addition of speed initial value; Sign indicating number speed totalizer (first order DDS) adds up to instantaneous velocity, obtains code phase sequences, obtains the instantaneous code phase value after this sequence and the initial pseudo addition, and the most significant digit of code phase is as the sign indicating number clock;

(6) under the effect of sign indicating number clock, produce I road and Q road spreading code;

(7) read I road and Q road navigation message, and carry out mould 2 with spreading code and add;

(8) spreading code is carried out molding filtration and be modulated on the intermediate frequency carrier;

(9) spread-spectrum signal is carried out power control and digital-to-analog conversion obtains the intermediate frequency simulation satellite signal.

Compared with prior art, the invention has the beneficial effects as follows: do not carry out interpolation and filtering, directly produce intermediate frequency carrier, simple in structure; Adopt three rank DDS cascades to realize the Doppler simulation of carrier wave and sign indicating number, rate smoothing does not have rank more, and can reach very high precision.

Description of drawings

Fig. 1 is the realization block diagram of high dynamic high precision intermediate frequency satellite signal generating method according to an exemplary embodiment of the present invention;

Fig. 2 is included in Fig. 1 intermediate frequency satellite-signal to produce the realization block diagram that three rank carrier phases in the block diagram add up according to an exemplary embodiment of the present invention;

Fig. 3 is the phase-accumulated realization block diagram of three exponents that is included in according to an exemplary embodiment of the present invention in Fig. 1 intermediate frequency satellite-signal generation block diagram.

Embodiment

For making purpose of the present invention, technical scheme and advantage clearer, with reference to the accompanying drawings and embodiment, the present invention is described in further detail.

Fig. 1 is the realization block diagram of intermediate frequency satellite signal generating method according to an exemplary embodiment of the present invention.

As shown in Figure 1, the intermediate frequency satellite signal generating method comprises the steps:

In step 101, parameters such as the initial pseudo of received RF carrier wave, speed, acceleration, acceleration, and convert three required in the step 102 rank carrier phases add up parameter K 0a, K1a, K2a and K3a (Fig. 2) to.Conversion formula is as follows:

$k_{0a}=\frac{f_m{R}_0}{c}\×2^{\mathrm{Na}}.$

$k_{1a}=\frac{f_{m}v}{{\mathrm{cf}}_s}\×2^{\mathrm{Na}}$

$k_{2a}=\frac{f_{m}a}{{\mathrm{cf}}_s^2}{2}^{\mathrm{Na}}\×2^{c_{1a}}$

$k_{3a}=\frac{f_{m}b}{{\mathrm{cf}}_s^3}{2}^{\mathrm{Na}}\×2^{c_{1a}+c_{2a}}$

F wherein _mBe radio frequency carrier frequency, R ₀Be the pseudorange initial value, v is a speed, and a is an acceleration, and b is an acceleration, and c is the light velocity, f _sBe working clock frequency; Na is the length of carrier wave speed totalizer 205 (Fig. 2), C _1aBe the length of carrier wave acceleration accumulator 203 (Fig. 2), C _2aLength for carrier wave acceleration totalizer 201 (Fig. 2).

In step 102, traditional single order Direct Digital frequency synthesis (DDS) model is carried out three-stage cascade, obtain three rank carrier phase totalizers (Fig. 2), adding up by three grades obtains carrier phase.The corresponding first order DDS of the initial phase of carrier wave and speed wherein, the corresponding second level DDS of acceleration, the corresponding third level DDS of acceleration.Corresponding relation between the parameter K 0a that calculates in the step 101, K1a, K2a and K3a and the three rank carrier phase totalizers will be described in Fig. 2.

The three rank carrier phases carrier phase that obtains that adds up is carried out phase truncation by step 103, the phase place after blocking as just/Input Address of cosine look-up table (105 and 104).

Cosine look-up table 104 and sine lookup table 105 stored just/the cosine look-up table file, realize the conversion of phase-magnitude, obtain comprising doppler information just/cosine intercarrier signal (107 and 106).

In step 108, parameters such as the initial pseudo of reception ranging code, speed, acceleration, acceleration, and convert the phase-accumulated parameter K 0b of three exponents required in the step 109, K1b, K2b and K3b (Fig. 3) to.Conversion formula is as follows:

$k_{0b}=\frac{f_c{R}_0}{c}\×2^{\mathrm{Nb}}.$

$k_{1b}=\frac{f_{c}v}{{\mathrm{cf}}_s}\×2^{\mathrm{Nb}}$

$k_{2b}=\frac{f_{c}a}{{\mathrm{cf}}_s^2}{2}^{\mathrm{Nb}}\×2^{c_{1b}}$

$k_{3b}=\frac{f_{c}b}{{\mathrm{cf}}_s^3}{2}^{\mathrm{Nb}}\×2^{c_{1b}+c_{2b}}$

F wherein _cBe code check, Nb is the length of sign indicating number speed totalizer 305 (Fig. 3), C _1bBe the length of sign indicating number acceleration accumulator 303 (Fig. 3), C _2bLength for sign indicating number acceleration totalizer 301 (Fig. 3).

It is identical that the realization principle of three exponents phase-accumulated (step 109) and three rank carrier phases add up, and all traditional DDS cascade obtained (Fig. 3); The corresponding first order DDS of Ma initial pseudo and speed wherein, the corresponding second level DDS of the acceleration of sign indicating number, the corresponding third level DDS of the acceleration of sign indicating number.Corresponding relation between the parameter K 0b that calculates in the step 108, K1b, K2b and K3b and the three exponent phase accumulators will be described in Fig. 3.

In step 109, the most significant digit of code phase totalizer is used to produce I road spreading code (110) and Q road spreading code (111) as the sign indicating number clock.I road spreading code in step 112 with carry out mould 2 from the I road navigation message that buffer zone reads and add, obtain I road ranging code; Q road spreading code in step 113 with carry out mould 2 from the Q road navigation message that buffer zone reads and add, obtain Q road ranging code.

In order to reduce the intersymbol interference of different passage spread spectrum codes, improve signal constellation (in digital modulation) plot quality and pseudorange phase control precision, I road ranging code is obtained filtered I road ranging code through sign indicating number formed filter 114, Q road ranging code is obtained filtered Q road ranging code through sign indicating number formed filter 115.

In the step 116, will multiply each other, obtain I road modulated intermediate frequency signal from 106 intermediate frequency cosine signal and I road ranging code from 114; In like manner, in step 117, will multiply each other, obtain Q road modulated intermediate frequency signal from 107 intermediate frequency sinusoidal signal and Q road ranging code from 115.

The addition in step 118 of I/Q two-way modulated intermediate frequency signal realizes that signal is synthetic, obtains the high dynamic high precision QPSK spreading code modulation signal of quadrature.After with multiplier output signal power being controlled again, obtain comprising the satellite analog intermediate frequency signal of doppler information through digital-to-analog conversion (119).

Fig. 2 is included in the realization block diagram of three rank carrier phase totalizers 102 among Fig. 1.

Three rank carrier phase totalizers 102 are according to the DDS principle, adopt the three rank model that adds up, parameters such as the carrier phase in the time of can accurately simulating each satellite-signal arrival receiver, Doppler shift, acceleration, acceleration when realizing high dynamic similation, also have very high resolution.

As shown in Figure 2, under the clock effect, 201 pairs of acceleration parameter K of carrier wave acceleration totalizer 3a adds up, and obtains the acceleration sequence that is produced by acceleration; This sequence obtains the instantaneous acceleration value after doing that with acceleration initial value K2a the symbol addition is arranged by totalizer 202.In like manner, under the clock effect, 203 pairs of instantaneous acceleration parameters of carrier wave acceleration accumulator add up, and obtain the velocity series that is produced by acceleration; This sequence obtains the instantaneous velocity value after doing that with speed initial value K1a the symbol addition is arranged by totalizer 204.205 pairs of instantaneous velocity parameters of carrier wave speed totalizer add up, and obtain the phase sequence that is produced by speed; This sequence obtains the instantaneous phase value after doing that with initial phase K0a the symbol addition is arranged by totalizer 206.Upgrade the value of K3a, K2a, K1a according to satellite trajectory and user movement state, then can realize continuously, high dynamic, high-precision carrier signal emulation.

Fig. 3 is included in the realization block diagram of three exponent phase accumulators 109 among Fig. 1.

Three exponent phase accumulators 109 realize that principles are identical with three rank carrier phase totalizers 102, adopt the add up parameters such as pseudorange, speed, acceleration, acceleration of the accurate analogue ranging sign indicating number of model of three rank.

As shown in Figure 3, under the clock effect, 301 pairs of acceleration parameter K of sign indicating number acceleration totalizer 3b adds up, and obtains the acceleration sequence that is produced by acceleration; This sequence obtains the instantaneous acceleration value after doing that with acceleration initial value K2b the symbol addition is arranged by totalizer 302.In like manner, under the clock effect, 303 pairs of instantaneous acceleration parameters of sign indicating number acceleration accumulator add up, and obtain the velocity series that is produced by acceleration; This sequence obtains the instantaneous velocity value after doing that with speed initial value K1b the symbol addition is arranged by totalizer 304.305 pairs of instantaneous velocity parameters of sign indicating number speed totalizer add up, and obtain the phase sequence that is produced by speed; This sequence obtains the instantaneous phase value after doing that with initial phase K0b the symbol addition is arranged by totalizer 306.Upgrade the value of K3b, K2b, K1b according to satellite trajectory and user movement state, then can realize continuously, high dynamic, high-precision pseudorange emulation.

The present invention has the following advantages:

(1) directly produce intermediate-freuqncy signal, simple in structure, accurately simulate the signal of each clock sampling point, guarantee The simulation precision of signal;

(2) adopt the cumulative method of three rank carrier phases, direct acceleration, acceleration, speed to carrier wave The degree parameter is cumulative to obtain high accuracy, continuous carrier phase information;

(3) adopt the phase-accumulated method of three exponents, direct acceleration, acceleration, speed to spreading code The degree parameter is cumulative to obtain high accuracy, continuous code phase information.

Claims (1)

1, a kind of high dynamic high precision intermediate frequency simulation satellite signal generating method is characterized in that, may further comprise the steps:

(1) parameter of received RF carrier wave comprises initial pseudo, speed, acceleration and acceleration;

(2) method that adds up by three rank carrier phases produces the high-precision carrier phase that comprises Doppler shift; It is to be that the DDS model carries out three-stage cascade and obtains with traditional single order Direct Digital frequency synthesis that three rank carrier phases add up, the corresponding first order DDS of initial pseudo and speed wherein, the corresponding second level DDS of acceleration, the corresponding third level DDS of acceleration; Under the clock effect, carrier wave acceleration totalizer is that third level DDS adds up to acceleration, obtains the acceleration sequence, obtains the instantaneous acceleration value after this sequence and the addition of acceleration initial value; In like manner, the carrier wave acceleration accumulator is that second level DDS adds up to instantaneous acceleration and obtains velocity series, obtains the instantaneous velocity value after this sequence and the addition of speed initial value; Carrier wave speed totalizer is that first order DDS adds up to instantaneous velocity, obtains the carrier phase sequence, obtains the instantaneous carrier phase value after this sequence and the initial pseudo addition;

(3) look into sine after carrier phase is blocked, cosine table obtains intercarrier signal;

(4) parameter of reception ranging code comprises initial pseudo, speed, acceleration and acceleration parameter;

(5) adopt the phase-accumulated method of three exponents to produce high-precision sign indicating number clock; The phase-accumulated method of three exponents obtains traditional DDS cascade; The corresponding first order DDS of initial pseudo and speed wherein, the corresponding second level DDS of acceleration, the corresponding third level DDS of acceleration; Sign indicating number acceleration totalizer is that third level DDS adds up to acceleration, obtains the acceleration sequence, obtains the instantaneous acceleration value after this sequence and the addition of acceleration initial value; In like manner, a sign indicating number acceleration accumulator is that second level DDS adds up to instantaneous acceleration and obtains velocity series, obtains the instantaneous velocity value after this sequence and the addition of speed initial value; Sign indicating number speed totalizer is that first order DDS adds up to instantaneous velocity, obtains code phase sequences, obtains the instantaneous code phase value after this sequence and the initial pseudo addition, and the most significant digit of code phase is as the sign indicating number clock;

(6) under the effect of sign indicating number clock, produce I road and Q road spreading code;

(7) read I road and Q road navigation message, and carry out mould 2 with spreading code and add;

(8) spreading code is carried out molding filtration and be modulated on the intermediate frequency carrier;

(9) spread-spectrum signal is carried out power control and digital-to-analog conversion obtains the intermediate frequency simulation satellite signal.

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