Direct sequence spread spectrum signal acquisition method
A direct sequence spread spectrum, signal technology, applied in the field of spread spectrum signal capture
Inactive Publication Date: 2014-04-09
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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Problems solved by technology
The lack of low-cost high-speed ADC has become one of the main reasons restricting the application of ultra-high-speed and ultra-wideband communication technology
Regardless of whether it is time-domain capture or frequency-domain capture, the main problem is that in order to achieve better spread spectrum performance, the code rate of the spread spectrum sequence is generally very high, resulting in a wide bandwidth of the spread spectrum signal. Due to the Nyquist ( Nyquist) sampling law, the sampling rate is often higher
Even if there is data compression in the subsequent processing, the data is first sampled according to the Nyquist law and then compressed, which does not fundamentally solve the problem of high sampling rate
This will inevitably increase the system's requirements for the front-end analog-to-digital converter (ADC), and also increase the system's computing and storage costs
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[0071] A typical application of direct sequence spread spectrum is in the GPS system, using Gold codes to spread the GPS navigation message to ensure the anti-jamming performance of long-distance transmission. The implementation of the technical solution of the present invention will be described below by taking the capture of the GPSL1 signal as an example.
[0072] The first step is to set parameters, spread spectrum sequence length L=1023, code rate c=1.023MHz of spread spectrum sequence, carrier frequency f c =1575.42MHz, intermediate frequency f I =4.7224MHz, the sampling frequency f that satisfies the Nyquist theorem s =16.368MHz, reference sampling interval T s =1 / f s =0.061us, the received data length T for capture P =1ms, compression ratio r=0.1, the search range of Doppler frequency is [f I -10KHz, f I +10KHz], the search interval is 1KHz, the preset decision threshold Thresh=4, the actual sampling rate is f r =1.6368MHz, the actual sampling inter...
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The invention relates to a novel direct sequence spread spectrum signal acquisition method in the direct sequence spread spectrum signal acquisition technology field. According to a technical scheme of the invention, obtained data is subjected to pretreatment, the data is sampled with a low sampling rate, and an observation signal is obtained. Through calculating projection value change of the observation signal on a product matrix of a pretreatment matrix and a cyclic shift matrix of a spread spectrum sequence, a phase value of a received spread spectrum signal is estimated. When employing the technical scheme to carry out spread spectrum signal acquisition, under a condition that a sampling rate is lower than Nyquist sampling law requirement, spread spectrum sequence acquisition is completed, thus cost of an acquisition system is substantially reduced.
Description
technical field [0001] The invention relates to a spread spectrum signal acquisition technology in the field of digital signal processing, in particular to a method for capturing direct sequence spread spectrum signals. Background technique [0002] A key technology in the reception and processing of direct sequence spread spectrum signals is the synchronization of spread spectrum sequences, that is, the sequences used for despreading at the receiving end must be aligned with the spread spectrum sequences in the spread spectrum signals, or in other words, have the same phase. To ensure that the original signal can be obtained correctly. Since the starting phase of the spread spectrum sequence in the received signal is random, it is necessary to capture the spread spectrum sequence first, that is, to obtain the estimated value of its starting phase, and then carry out precise synchronization in the subsequent tracking link. [0003] Suppose the signal at the receiving end i...
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IPC IPC(8): H04B1/7075
Inventor 林静然李玉柏
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA