A GPS Weak Signal Acquisition Method Based on Differential Loop Coherent Integration
A technology of weak signal capture and coherent integration, which is applied in satellite radio beacon positioning systems, measuring devices, instruments, etc., can solve the problems that GPS cannot be well applied, signal coherent integration value decreases, and coherent integration time increases
Inactive Publication Date: 2016-06-29
HARBIN ENG UNIV
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Problems solved by technology
The superiority of GPS has received everyone's attention, and its application range is extremely wide, but there are still limitations: for example, when the signal is attenuated to very weak in indoor, forest, urban and other environments, GPS cannot be well applied
However, as the integration time length increases, the coherent integration value of the signal will decrease relatively
Due to the influence of data bit jumps, the coherent integration time cannot be increased without limit, and the non-coherent integration will cause square loss, and the non-coherent integration cannot be performed without limit
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[0038] like Figure 4 As shown, the present invention is based on the differential cyclic coherent integration GPS weak signal acquisition method comprising the following steps:
[0039] Step 1: Take a piece of 20Mms intermediate frequency signal data, M=1, 2, 3..., divide the received data into blocks with a length of L=10ms; set the Doppler frequency shift range (ω Dmin ,ω Dmax ) and search frequency step Δω D , and set the detection threshold γ at the same time;
[0040] Every 20ms data is divided into two pieces, which are recorded as , where m=1,2,3,...,M; for example, the first 20ms data length (not necessarily exactly one data bit) is divided into 2 blocks, which are recorded as After the second 20ms data block is divided, it is recorded as And so on.
[0041] Step 2: Estimate data bit flips and select data blocks;
[0042] The length of the navigation data is exactly 20ms, and the bits of the navigation data may flip every 20ms. Divide the first 20ms data int...
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The invention relates to a GPS weak signal capturing method based on differential circular coherent integration. The method includes the first step of fetching data of a section of 20M-millisecond (ms) intermediate frequency signals and segmenting the received data according to the length of L=10ms, setting a Doppler frequency shift range ( ) and searching for a stepped frequency , and setting a detection threshold value gamma, wherein M is equal to one, two, three, ..., the second step of conducting estimation on data bit flipping and selecting data blocks, the third step of carrying out carrier stripping on the selected data, carrying out frequency mixing on stripped data and sinusoidal signals on an in-phase branch of local copied carriers and frequency mixing on the stripped data and cosine signals of an orthogonal branch to obtain I-path signals and Q-path signals, and carrying out coherent integration on in-phase data and data of the orthogonal branch, the fourth step of multiplying the data of each block and a latter adjacent block in a complex conjugation mode, that is, carrying out differential circular correlation, and the fifth step of carrying out correlation and summation on results in the fourth step to obtain a peak value Y, comparing the peak value Y with the detection threshold value gamma, and judging whether the signals are captured successfully.
Description
technical field [0001] The invention relates to a GPS weak signal acquisition method based on differential cyclic coherent integration. Background technique [0002] In the 1970s, the U.S. Department of Defense, together with the Army, Navy and Air Force, began to develop the Global Positioning System—Global Positioning System, or GPS for short. GPS can provide users with accurate location, speed, time and other information, and has been widely used. GPS (Global Positioning System) is the earliest and most mature navigation and positioning system. The superiority of GPS has received everyone's attention, and its application range is extremely wide, but there are still limitations: for example, when the signal is attenuated to very weak in indoor, forest, urban and other environments, GPS cannot be used well. In a GPS software receiver, capture is the first module to be started by the receiver, which has an important impact on the performance of the entire receiver. In ord...
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IPC IPC(8): G01S19/29G01S19/30
CPCG01S19/29G01S19/30
Inventor 沈锋桑靖韩浩周阳李强刘明凯兰晓明迟晓彤张金丽李伟东
Owner HARBIN ENG UNIV