Fast carrier capture method with low signal-noise ratio

Abstract

A method for quickly catching the low signal-to-noise ratio carrier comprises the following steps: (1) multiplying an input signal with a cos branching data generated by a first NCO module; (2) executing half band filtering; (3) executing down sampling to a first accumulated down sampling module, temporarily storing into an exterior SDRAM through an FIFO-IN module, and the data speed fsl and the maximum capture bandwidth after the first accumulated down sampling satisfy the relationship: fsl>2*f, [f1, f2] is the capture range, (4) reading the data in the exterior SDRAM through an FIFO-OUT module, and multiplying data of two branches of sin and cos generated by a second NCO; (5) entering a second down-sampling through the LPF; (6) executing FFT procession; and (7) adding a second NCO localoscillating frequency, repeating the steps (4)-(6) for n times to find out a maximum value in the results of step (6) and obtain the final frequency offset result. The method according to the invention has the advantages of adaptability for low signal-to-noise ratio, wide capture range and quick capture on the base that the modulation degree characteristic of the universal controlling signal is satisfied.

Description

technical field [0001] The invention relates to a method for quickly capturing a carrier with a low signal-to-noise ratio and a large frequency deviation, which is mainly applied to the rapid capture of a carrier under a standard USB measurement and control system, and solves the problem of fast capturing of a carrier wave in the case of a large frequency deviation with a low signal-to-noise ratio. Background technique [0002] The unified S-band (USB) measurement and control system is a mature measurement and control system, which can simultaneously complete the functions of angle tracking, speed measurement, distance measurement, telemetry, remote control and voice communication. With the continuous development of digital communication systems, digital carrier capture technology has become a commonly used technology. For the estimation and correction of the frequency offset in the demodulation process, there are more mature algorithms, such as phase-locked loop (PLL) metho...

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Problems solved by technology

The article "Research on the Method of Fast Capture of USB Transponder Carrier", Zhang Chunlong et al., Proceedings of the 2003 National Simulation Technology Academic Conference, according to the characteristics of frequency symmetry, the frequency of the carrier is determined by the combination of FFT and DFT. The resolution of this method is Low, narrow capture range, unable to meet the characteristics of wide capture range and fast capture at the same time

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