DDS-based Doppler compensation device in real-time water sound communication

Abstract

The invention discloses a DDS-based Doppler compensation device in real-time water sound communication. An analogue-to-digital conversion circuit at the front end of a communication processing plate is connected with a universal I/O port of a field programmable logic device FPGA in a parallel interface mode through a group of data buses; a signal processing chip DSP serving as a processing core chip is connected with the FPGA through the data buses of EMIFA interfaces in and out of the chip; a chip selection wire, a reading control wire and partial address wires of an EMIFA interface are connected with the universal I/O interface of the FPGA; 10/100Mb/s Ethernet comprising a DSP for interconnecting networks controls an external network interface circuit; and a frequency synthesis module is connected with the universal I/O interface of the FPGA through a group of data buses and reading control wires of the DDS. The device can well compensate the Doppler frequency shift in the real-timewater sound communication in real time with high precision, and has the characteristics of high output frequency precision, real-time Doppler communication, strong applicability, high speed, stability and flexible application.

Description

technical field [0001] The invention relates to a DDS-based high-precision Doppler compensation processing platform structure used in multi-carrier real-time underwater acoustic communication. Background technique [0002] Orthogonal Frequency Division Multiplexing (OFDM) technology has been applied in underwater acoustic communication, and it is a high-speed transmission method. However, OFDM transmission requires high subcarrier orthogonality, so the severe Doppler frequency shift in underwater acoustic communication limits the application of OFDM technology in underwater acoustic communication. In order to eliminate the influence of the inevitable Doppler shift on underwater acoustic communication, many correction methods have been proposed. [0003] At present, in the field of underwater acoustic communication, there are two commonly used theoretical methods for Doppler compensation: one is to use the structure of DFE plus second-order digital phase-locked loop (DPLL), ...

AI Technical Summary

Problems solved by technology

This method is suitable for small Doppler frequency shift, but the structure of this equalizer is complex, especially in high-speed underwater acoustic communication, which has reached the level of hindering real-time communication; another method is to add Doppler processing structure, estimate the Doppler frequency shift, and then compensate it

This kind of interpolation requires a lot of calculation and storage. If linear interpolation is used, the calculation is small, but when the signal-to-noise ratio is small, its performance deteriorates sharply.

Performing Doppler compensation on the received signal is equivalent to resampling the received signal, but it is difficult to change the sampling rate when the Doppler frequency shift is small and the accuracy requirements are high

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