A method of navigation signal noise power estimation

Abstract

The application provides a navigation signal noise power estimation method and relates to the field of satellite navigation. The method is characterized in that: a pseudo code similar to the real navigation signal is constructed, real-time correlation accumulation is carried out with the digital intermediate frequency data, the noise energy estimation result with the same period as the real navigation signal is obtained, and the noise power estimation result is obtained by carrying out smoothing filtering on the noise energy estimation result. The application realizes real-time and accurate estimation of the noise signal power through configuration, realizes estimation and smoothing of the noise power in the RTL, reduces the operation complexity of the software, improves the estimation accuracy of the subsequent carrier-to-noise ratio, and realizes accurate evaluation of the quality of the navigation signal.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation, and in particular to a method for estimating the noise power of navigation signals. Background Technology

[0002] In navigation signal receiving algorithm design, the carrier-to-noise ratio (CNR) is typically used as a metric for the quality of navigation signals. The accuracy of the CNR estimation has a significant impact on receiver performance. Firstly, the estimated CNR can assist acquisition and tracking algorithms in determining the state of the signal. Secondly, the CNR is used as a selection criterion for whether a specific satellite should participate in the positioning calculation. Traditional CNR estimation methods primarily analyze the statistical characteristics of the I and Q branch integrals to obtain estimates of signal power and noise power, thereby deriving the CNR or signal-to-noise ratio (SNR). In complex electromagnetic environments, large estimation errors in navigation signal noise power directly lead to inaccurate CNR estimation, thus affecting the performance of the navigation signal receiving algorithm. Summary of the Invention

[0003] This invention aims to address the shortcomings of existing technologies by providing a method for estimating navigation signal noise power, overcoming the drawback of large noise power estimation errors in traditional estimation methods.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for estimating navigation signal noise power, the method comprising the following steps:

[0006] (1) Configure the pseudocode generator parameters required for the noise channel, including polynomial, initial phase, pseudocode period length and pseudocode chip length, configure carrier NCO parameters, and configure the noise energy accumulation period length and noise power smoothing parameters of the noise channel.

[0007] (2) The satellite navigation signals broadcast by the navigation satellites are down-converted and AD sampled to obtain digital intermediate frequency data;

[0008] (3) Under the control of the intermediate frequency data enable signal, a local carrier signal is generated according to the carrier NCO parameters, and the digital intermediate frequency data is frequency converted using the local carrier signal.

[0009] (4) Under the control of the intermediate frequency data enable signal, the chip enable signal is obtained according to the configured pseudo code chip length. Under the control of the chip enable signal, the pseudo random code for despreading is generated according to the configured pseudo code generator polynomial, initial phase and pseudo code period length.

[0010] (5) Under the control of the intermediate frequency data enable signal, noise energy is accumulated on the intermediate frequency data after frequency conversion according to the pseudo-random code;

[0011] (6) Generate a noise power cycle enable signal under the control of the intermediate frequency data enable signal, clear the noise energy accumulation result to zero under the control of the noise power cycle enable signal, and sample to obtain the noise energy estimation result within one cycle;

[0012] (7) Under the control of the noise power cycle enable signal, the noise power is calculated using the noise energy estimation result, and the noise power is smoothed by filtering to obtain the smoothed noise power.

[0013] In step (5), the noise energy accumulation period is the same as the minimum integration period of the navigation signal.

[0014] Compared with the prior art, the beneficial effects achieved by this invention are as follows:

[0015] This invention enables real-time and accurate estimation of noise signal power through configuration, thereby improving the accuracy of subsequent carrier-to-noise ratio estimation.

[0016] This invention achieves noise power estimation and smoothing within the RTL, reducing the computational complexity of the software. Attached Figure Description

[0017] Figure 1 This is a general implementation block diagram of an embodiment of the present invention. Detailed Implementation

[0018] See attached document Figure 1 The embodiments of the present invention will be described below.

[0019] A method for estimating navigation signal noise power, the method comprising the following steps:

[0020] (1) Configure the pseudocode generator parameters required for the noise channel, including polynomial, initial phase, pseudocode period length and pseudocode chip length, configure the carrier NCO parameters of the noise channel, and configure the noise energy accumulation period length and noise power smoothing parameters of the noise channel.

[0021] In this embodiment, the pseudo-random code should be a GOLD code that is similar to the navigation signal parameters but has good cross-correlation performance with the existing navigation signal; the noise energy accumulation period length is consistent with the minimum period of the navigation signal, which is generally the number of digital intermediate frequency sampling points within 1ms; the noise power smoothing parameter is k; all parameters are configured during the power-on initialization process.

[0022] (2) The satellite navigation signals broadcast by the navigation satellites are down-converted and AD sampled to obtain digital intermediate frequency data;

[0023] In this embodiment, real sampling is used, and the intermediate frequency signal is if_data.

[0024] (3) Under the control of the intermediate frequency data enable signal, a local carrier signal is generated according to the carrier NCO parameters, and the local carrier signal is used to perform frequency conversion processing on the digital intermediate frequency data.

[0025] In this embodiment, the local carrier signal obtained from the carrier NCO is denoted as cos and sin; the digital intermediate frequency data is multiplied by the local carrier to obtain the zero intermediate frequency digital signal, denoted as if_data_i and if_data_q respectively. The calculation process is as follows:

[0026] if_data_i=if_data*cos

[0027] if_data_q=if_data*sin

[0028] (4) Generate the chip enable signal of the pseudo code generator under the control of the intermediate frequency data enable signal. Under the control of the chip enable signal, generate the pseudo random code for despreading according to the pseudo code generator polynomial, initial phase and pseudo code period length.

[0029] In this embodiment, under the control of the intermediate frequency signal enable if_en, the chip enable signal code_en is obtained according to the externally configured pseudo-code chip length code_len. Under the control of code_en, a pseudo-random code is generated, and the period of the pseudo-random code is pn_len, which is 10230.

[0030] (5) Under the control of the intermediate frequency data enable signal, noise energy is accumulated on the intermediate frequency data after frequency conversion according to the pseudo code symbol;

[0031] In this embodiment, the energy accumulation process is as follows:

[0032] I(n)=I(n-1)+if_data_i(pn_code==0)

[0033] Q(n)=Q(n-1)+if_data_q(pn_code==0)

[0034] I(n)=I(n-1)-if_data_i(pn_code==1)

[0035] Q(n)=Q(n-1)-if_data_q(pn_code==1)

[0036] Where n is the number of sampling points.

[0037] (6) Generate a noise power cycle enable signal under the control of the intermediate frequency data enable signal, clear the accumulated noise energy accumulation result to zero under the control of the noise power cycle enable signal, and sample to obtain the noise energy estimation result within one cycle.

[0038] In this embodiment, the energy accumulation process is essentially a process of integrating and clearing the digital intermediate frequency (IF) signal. Under the control of the IF signal enable `if_en`, the digital IF signal is accumulated based on the symbol main sampling point of the pseudocode `pn_code`. Simultaneously, a clearing enable signal `dump_en` is generated based on `dump_len`. Under the control of the `dump_en` signal, the accumulated noise energy is cleared, and the noise energy I is obtained by sampling the noise. N (m) and Q N (m), where m is the dump cycle count.

[0039] (7) Under the control of the noise power periodic energy signal, the noise power is calculated using the noise energy estimation results, and the noise power is smoothed by filtering to obtain the smoothed noise power.

[0040] In the embodiment, the noise power N(m) is composed of the noise energy I. N (m) and Q N (m) is calculated, and the calculation process is as follows:

[0041]

[0042] Let the current noise power estimate be N(m), and the smoothed noise power be... The smoothing process is as follows:

[0043]

[0044] The smoothing filter coefficient is: α = 1 - 1 / 2 k .

[0045] This invention discloses a navigation signal noise power estimation method that, through configuration, achieves real-time and accurate estimation of noise signal power. The method performs noise power estimation and smoothing within the RTL, reducing software computational complexity, improving the estimation accuracy of subsequent carrier-to-noise ratio, and enabling accurate evaluation of navigation signal quality.

[0046] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for estimating the noise power of navigation signals, characterized in that, The method includes the following steps: (1) Configure the pseudocode generator parameters required for the noise channel, including polynomial, initial phase, pseudocode period length and pseudocode chip length, configure carrier NCO parameters, and configure the noise energy accumulation period length and noise power smoothing parameters of the noise channel. (2) The satellite navigation signals broadcast by the navigation satellites are down-converted and AD sampled to obtain digital intermediate frequency data; (3) Under the control of the intermediate frequency data enable signal, a local carrier signal is generated according to the carrier NCO parameters, and the digital intermediate frequency data is frequency converted using the local carrier signal. (4) Under the control of the intermediate frequency data enable signal, the chip enable signal is obtained according to the configured pseudo code chip length. Under the control of the chip enable signal, the pseudo random code for despreading is generated according to the configured pseudo code generator polynomial, initial phase and pseudo code period length. (5) Under the control of the intermediate frequency data enable signal, noise energy is accumulated on the intermediate frequency data after frequency conversion according to the pseudo-random code; (6) Generate a noise power cycle enable signal under the control of the intermediate frequency data enable signal, clear the noise energy accumulation result to zero under the control of the noise power cycle enable signal, and sample to obtain the noise energy estimation result within one cycle; (7) Under the control of the noise power cycle enable signal, the noise power is calculated using the noise energy estimation result, and the noise power is smoothed by filtering to obtain the smoothed noise power.

2. The navigation signal noise power estimation method according to claim 1, characterized in that, In step (5), the noise energy accumulation period is the same as the minimum integration period of the navigation signal.

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