CN102565828A - Method for reducing signal emitting power of satellite navigation and positioning system - Google Patents

Abstract

The invention relates to a method for reducing the signal transmission power of a satellite navigation and positioning system, which does not change other generation processes and links of the navigation signal, but only changes the generation and modulation mode of the spread spectrum code of the navigation signal to realize the rational and effective use of the navigation signal. The transmission power spectral density within the bandwidth, so as to achieve the purpose of reducing the signal transmission power. That is to say, in the navigation signal spreading code, the code clock frequency of the high-length fine code is N times that of the short and thick code. If the code clock frequency of the short and thick code is increased by N times, while keeping the cycle period of the short and thick code unchanged, the total power Under changing conditions, the number of spectral lines of the spread spectrum signal can be increased by N times, and the height of the spectral lines can be reduced by N decibels, thus forming short precision codes. In this way, when the long precise code and the short precise code are added to the two orthogonal branches and modulate the carrier at the same time, the height of the frequency spectrum is the same as when the long precise code or the short precise code is modulated separately.

Description

A method for reducing signal transmission power used in satellite navigation and positioning system

technical field

The invention relates to a method for reducing signal transmission power of a satellite navigation and positioning system, and is especially suitable for the condition that the signal transmission power is limited.

Background technique

Each Global Navigation Satellite System (GNSS), such as GPS in the United States, GALILEO in Europe and GLONASS in Russia, has its own unique signal transmission power according to its own system structure, positioning method and modulation method Efficient and comprehensive utilization.

At present, the foreign GNSS systems all adopt spread spectrum modulation technology, which is analyzed from the perspective of signal power spectral density function. The power spectral density function of GNSS navigation signal spread spectrum modulation directly affects the effective distribution and utilization of signal transmission power; and the spread spectrum code Design and generation are the core technologies of spread spectrum modulation.

There are two main types of spreading codes used in foreign GNSS systems: short thick codes and long precise codes. The short and thick codes have a short repetition period, which is easy for GNSS receivers to capture, but the positioning accuracy is low; the long and precise codes have a long repetition period, and the long and precise codes need to be captured under the guidance of the short and thick codes, but the positioning accuracy is high. Since these two spreading codes have good complementarity, they are usually modulated on two orthogonal branches of the same carrier and used together.

In engineering implementation, the size of the satellite transmission power is measured by the highest spectral line of the satellite transmission signal reaching a certain threshold value. The code clock frequency of the short and thick code is low, and the power of the signal is concentrated on a few spectral lines in a narrow frequency band. The lower the frequency of the spread spectrum code clock, the higher the spectral line height, and the higher the actual required transmission power; The code clock frequency of the fine code is higher, and the power of the signal is dispersed on many spectral lines in a wider frequency band. The higher the frequency of the spread spectrum code clock, the lower the height of the spectral line, and the lower the actual required transmission power. Therefore, the higher power required to transmit the short and coarse codes raises the overall transmit power required to transmit the signal, compared to the lower power required to transmit the long and fine codes, resulting in a waste of transmit power, as shown in Figure 1 .

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a method for reducing signal transmission power in a satellite navigation and positioning system, which overcomes the problem of transmission power caused by the relatively high power required for transmitting short and thick codes in the process of signal generation and transmission. waste.

Technical solutions

A method for satellite navigation and positioning system to reduce signal transmission power, characterized in that the steps are as follows:

Step 1 generates the navigation message: according to the design and arrangement format of the navigation message, generate the bit information P _data of the navigation message;

Step 2 generates a long precise code: the generation cycle is T _{long_code} seconds, the rate is F _{long_code} MHz, and the length of the code chip in the cycle is L _{long_code} = T _{long_code} * F _{long_code} Long precision code P _{long_code} = X ₁ +X ₂ , where , the symbol "+" represents a mole addition operation, and X ₁ and X ₂ represent polynomials generated by two pseudo-random sequences;

Step 3: generate the short code: determine that the rate of the short code is consistent with the long code as F _{long_code} MHz, the code period T _{short_code} satisfies the condition T _{short_code} <T _{long_code} /10, and the chip length is L _{short_code} = T _{short_code} * F _{long_code} , Its short code P _{short_code} = X' ₁ +X' ₂ , wherein, the symbol "+" represents a mole addition operation, and X' ₁ and X' ₂ are respectively pseudo-random sequences generated by generator polynomials of X ₁ and X ₂ according to L The length of _{short_code} is truncated;

Step 4 Spread spectrum modulation: Carry out spread spectrum modulation with the navigation message bit information and the long precise code and the short precise code respectively, and obtain the long precise code spread spectrum modulation signal S _long and the short precise code spread spectrum modulation signal S _short respectively:

S _long ＝P _{long_code} +P _data

S _short = P _{short_code} + P _data

Step 5 Carrier modulation: use the carrier signal S _carrier to perform carrier modulation on the generated long-precision code spread spectrum modulation signal S _long and short-fine code spread spectrum modulation signal S _short , and complete the shift of the spread spectrum signal spectrum in the carrier frequency band to obtain the satellite The modulated signal transmitted by the navigation and positioning system:

S _signal1 = S _long * S _carrier

S _signal2 ＝S _short *S _carrier

The symbol "*" represents a numerical multiplication operation.

Beneficial effect

A method for reducing the signal transmission power of the satellite navigation and positioning system proposed by the present invention does not change other generation processes and links of the navigation signal, but only changes the generation and modulation method of the spread spectrum code of the navigation signal to realize the rational and effective use of the navigation signal The transmission power spectral density within the effective bandwidth, so as to achieve the purpose of reducing the signal transmission power. That is to say, in the navigation signal spreading code, the code clock frequency of the high-length fine code is N times that of the short and thick code. If the code clock frequency of the short and thick code is increased by N times, while keeping the cycle period of the short and thick code unchanged, the total power Under changing conditions, the number of spectral lines of the spread spectrum signal can be increased by N times, and the height of the spectral lines can be reduced by N decibels, thus forming short precision codes. In this way, when the long precise code and the short precise code are added to the two orthogonal branches and modulate the carrier at the same time, the height of the frequency spectrum is the same as when the long precise code or the short precise code is modulated separately.

The beneficial effect of the present invention is that the short precision code is a distance measuring code with a relatively short code length and a relatively high code rate. It adopts the speed of the fine code and the code length of the coarse code, so the short fine code not only absorbs the advantages of the length of the coarse code and easy capture, but also absorbs the advantages of high positioning accuracy of the fine code. It is a high-performance ranging code. The combination of short precise code and long precise code replaces the combination of short thick code and long precise code in the traditional GNSS system, which can effectively reduce the overall transmission power required by the signal and help to make reasonable and effective use of signal transmission power, saving the overall power consumption and cost of the system.

Description of drawings

Figure 1 is a schematic diagram of the comparison between the transmission power required for the long fine code and the required transmission power for the short thick code

Figure 2 is a schematic diagram of the long precise code generation method

Figure 3 is a schematic diagram of the method for generating short and precise codes

Figure 4 is a schematic diagram of the required transmit power for short and precise codes

Figure 5 is a schematic diagram of the transmission power required by the long precise code

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

In the embodiment of the present invention, China Area Positioning System (China Area Positioning System, referred to as CAPS) is used as the supporting platform to illustrate the implementation process of the method for generating short and precise codes in the spreading codes of the global navigation and positioning system proposed by the present invention. The specific implementation steps are as follows:

Step 1: Generate navigation message:

According to the design and arrangement format of the navigation message, under the action of the navigation information rate clock signal, the bit information P _data of the navigation message is sequentially read from the queue, and is ready to be processed with the spreading code for molar addition operation.

In this embodiment, the rate of navigation message information P _data is set as F _data =50 Hz.

Step 2: Generate long precise code

Determine the generation method of the long precise code. Assuming that the cycle period of the long code is T _{long_code} seconds, and the rate of the long code is F _{long_code} MHz, then the chip length in one cycle of the long code is L _{long_code} = T _{long_code} * F _{long_code} .

The long precise code generation process is shown in Figure 2.

As shown in Fig. 2, the generator polynomial of the long precise code is represented by P _{long_code} , and the two pseudo-random sequence generator polynomials are respectively represented by X ₁ and X ₂ , then: P _{long_code} = X ₁ +X ₂ , wherein the symbol "+" represents mole plus operation.

In this embodiment, the long code period is set as T _{long_code} =1 second, and the code rate is F _{long_code} =10.23 MHz, then the chip length in one long code period is L _{long_code} =T _{long_code} *F _{long_cod} =10230000.

In this embodiment, the generating polynomial of X ₁ is expressed as X ₁ =x ¹⁵ +x ¹⁴ +1, and the generating polynomial of X ₂ is expressed as X ₂ =x ¹⁵ +x ¹⁴ +x ¹² +x ³ +1, then the long precise code is generated The polynomial P _{long_code} =X ₁ +X ₂ , and the symbol "+" represents a mole addition operation.

Step 3: Generate Short Precision Code

According to the code cycle and code rate of the long code, the code cycle of the short code is determined to be T _{short_code} seconds, and T _{short_code} satisfies the condition T _{short_code} <T _{long_code} /10, and the code rate is still F _{long_code} MHz, then a short code cycle The internal chip length is L _{short_code} =T _{short_code} *F _{long_code} .

According to the generation method of the long precise code, the generation method of the short precise code is shown in Fig. 3 .

From Fig. 3, the generator polynomial of the short and precise code is represented by P _{short_code} , and the generator polynomials of the two pseudo-random sequences are represented by X' ₁ and X' ₂ respectively, then: P _{short_code} = X' ₁ +X' ₂ , where the symbol "+ "Indicates the mole addition operation, X' ₁ and X' ₂ are the pseudo-random sequences generated by the generating polynomials of X ₁ and X ₂ respectively, which are truncated according to the length of L _{short_code} .

P _{short_code} is the generated short code.

In this embodiment, according to the code cycle and the code rate of the long code, the code cycle of the short code is determined to be T _{short_code} = 1*10 ^-3 seconds, and the code rate is still F _{long_code} = 10.23MHz, then a short code cycle The internal chip length is L _{short_code} =T _{short_code} *F _{long_code} =10230.

According to the short-precision code generation method shown in Figure 3, in this embodiment, the generator polynomial of X' ₁ is expressed as X' ₁ =x ¹⁵ +x ¹⁴ +1, and the generator polynomial of X' ₂ is expressed as X' ₂ =x ¹⁵ +x ¹⁴ +x ¹² +x ³ +1, then the short-precision code generator polynomial P _{short_code} = X' ₁ +X' ₂ , the symbol "+" represents a mole addition operation, and the initial state settings of X' ₁ and X' ₂ are the same as those of X ₁ , X ₂ are the same.

Step 4: Spread Spectrum Modulation

The bit information of the navigation message is spread-spectrum modulated with the long-fine code and the short-precision code respectively, and the long-fine-code spread-spectrum modulation signal S _long and the short-fine code spread-spectrum modulation signal S _short are respectively obtained:

In this embodiment, the generated navigation message is respectively combined with the long precise code and the short precise code to perform a mole addition operation:

S _long ＝P _{long_code} +P _data

S _short = P _{short_code} + P _data

Step 5: Carrier Modulation

Carrier modulation is performed on the generated long-fine code spread spectrum modulation signal and short precision code spread spectrum modulation signal respectively with the carrier signal S _carrier to obtain the final modulation signals S _signal1 and S _signal2 , thus completing the transfer of the spectrum of the spread spectrum signal on the carrier frequency band .

S _signal1 = S _long * S _carrier

S _signal2 ＝S _short *S _carrier

The symbol "*" represents a numerical multiplication operation.

In this embodiment, the carrier signal S _carrier is set to 71MHz, then the carrier modulation is carried out to the spread spectrum signal:

S _signal1 = S _long * S _carrier

S _signal2 ＝S _short *S _carrier

The navigation signal modulated by the intermediate frequency can be obtained.

The transmit power required by the navigation signal modulated by the short-precise code and the transmit power required by the navigation signal modulated by the long-precise code proposed by the present invention are shown in Fig. 4 and Fig. 5 respectively. It can be seen from Fig. 4 and Fig. 5 that the transmission power required by the short-precision code proposed by the present invention is the same as that required by the long-precision code, thereby overcoming the problem of waste of transmission power and realizing the full utilization of transmission power.

Claims (1)

1. one kind is used for the method that satellite navigation and location system reduces signal transmission power, it is characterized in that step is following:

Step 1 generates navigation message: press navigation message design and array format, generate navigation message bit information P _Data

Step 2 generates long smart sign indicating number: the generation cycle period is T _{Long_code}Second, speed is F _{Long_code}Chip lengths is L in the MHz, cycle period _{Long_code}=T _{Long_code}* F _{Long_code}Long smart sign indicating number P _{Long_code}=X ₁+ X ₂, wherein, symbol "+" expression mole adds computing, X ₁And X ₂Represent the polynomial expression that two pseudo-random sequences generate;

Step 3 generates short smart sign indicating number: the speed of definite short smart sign indicating number is consistent with long essence sign indicating number to be F _{Long_code}MHz, the sign indicating number cycle T _{Short_code}T satisfies condition _{Short_code}＜T _{Long_code}/ 10, chip lengths is L _{Short_code}=T _{Short_code}* F _{Long_code}, its short smart sign indicating number P _{Short_code}=X ' ₁+ X ' ₂, wherein, symbol "+" expression mole adds computing, X ' ₁, X ' ₂Be respectively by X ₁, X ₂The pseudo-random sequence that generator polynomial produces is pressed L _{Short_code}Length brachymemma gained;

Step 4 band spectrum modulation: navigation message bit information is carried out band spectrum modulation with long smart sign indicating number and short smart sign indicating number respectively, obtain long smart sign indicating number modulated spread spectrum signal S respectively _LongWith short smart sign indicating number modulated spread spectrum signal S _Short:

S _long＝P _{long_code}+P _data

S _short＝P _{short_code}+P _data

Step 5 carrier modulation: adopt carrier signal S _CarrierTo the long smart sign indicating number modulated spread spectrum signal S that generates _LongWith short smart sign indicating number modulated spread spectrum signal S _ShortCarry out carrier modulation, accomplish spread-spectrum signal frequency spectrum moving on carrier wave frequency range, obtain the modulation signal of satellite navigation and location system emission:

S _signal1＝S _long*S _carrier

S _signal2＝S _short*S _carrier

The computing of symbol " * " expression numerical multiplication.

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