GNSS system bit synchronization method based on phase difference matched filtering

Abstract

The invention discloses a GNSS system bit synchronization method based on phase difference matched filtering. The GNSS system bit synchronization method based on phase difference matched filtering comprises the following steps that S1, an antenna receives satellite signals and conduct frequency shift and A / D sampling quantization; S2, frequency tracking and code tracking are conducted on digital intermediate frequency signals; S3, integration and zero clearing are both conducted on the two channels of tracked I / Q signals, and relevant complex signal data X[i]=I[i]+Q[i]*j within 1ms are obtained; S4, synchronous processing is conducted on X[i]. According to the step S4, two methods are provided, wherein the first method comprises the steps that delay conjugate of X[i] is solved, Z[i]=X[i]*X<*>[i-1] is calculated, circular correlation is conducted on Z[i] and LocalCode, Z'[i] is calculated, integration is conducted on Z'[i], so that the value of V[delta] (please see the equation of V[delta] in the specification) is obtained, and then the minimum V[delta] is the bit boundary; the second method comprise the steps that Z[i]= =X[i]* X<*>[i-1]is calculated, integration is conducted on Z[i], so that the value of V[delta] (please see the equation of V[delta] in the specification) is obtained, circular correlation is conducted on Z[i] and LocalCode, the maximum correlation value in correlation results is the bit boundary. The GNSS system bit synchronization method based on phase difference matched filtering is suitable for large-frequency-offset condition, not insensitive to frequency offset and small in calculation amount, only one channel of matched filtering and one channel of noncorrelation integral are needed, and resource consumption and time consumption are small.

Description

technical field [0001] The invention relates to a global satellite navigation system (GNSS), in particular to a bit synchronization method of the GNSS system based on phase difference matched filtering. Background technique [0002] For the received signal of the global satellite navigation system (GNSS), in order to read out the navigation message and assemble the pseudorange measurement value, it is necessary to find the data bit boundary from the received signal, that is, to perform bit synchronization. Common bit synchronization methods include histogram method, phase difference method, likelihood estimation and likelihood estimation matched filtering and other bit synchronization methods. The advantages and disadvantages of this method are: [0003] (1) The histogram method is simple to calculate but not suitable for large frequency offset or weak signal environment, so it is not suitable for calculating signals with secondary encoding; [0004] (2) The phase differen...

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Problems solved by technology

[0003] (1) The histogram method is simple to calculate but not suitable for large frequency offset or weak signal environment, so it is not suitable for calculating signals with secondary encoding;

[0004] (2) The phase difference method is not sensitive to frequency offset and is suitable for large frequency offset conditions, but not suitable for weak signal environments and signal calculations with secondary encoding;

[0005] (3) The likelihood estimation method is sensitive to frequency offset in the ideal case of no frequency offset, and is suitable for weak signal conditions and signals with secondary encoding, but not for large frequency offset conditions; and, although suitable for weak signal scenarios, But in reality, the frequency offset correction is inaccurate in weak signal scenarios, and the more accurate the estimated frequency offset is, the longer the integration time will be. In high dynamic scenarios, this integration time is contradictory to high dynamics, and the calculation is complicated high degree

[0006] (4) Likelihood estimation Matched filtering is suitable for weak signal conditions and signals with secondary encoding under the ideal condition of no frequency offset. It is sensitive to frequency offset and is not suitable for large frequency offset conditions, but requires 20 matched filters and 20 Channel frequency correction, high computational complexity

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