7 results about "Symbol rate" patented technology

This invention discloses an adaptive blind demodulation method, system, terminal, and medium based on a satellite communication system. The method includes: performing parameter estimation, frequency offset compensation, and timing synchronization processing on the original baseband sampled data sequence to obtain a single symbol rate data symbol sequence; performing hierarchical phase-locked loop carrier coarse synchronization iterative processing on the single symbol rate data symbol sequence to obtain a target convergent constellation diagram symbol sequence; extracting high-order cumulant features based on the target convergent constellation diagram symbol sequence and performing modulation scheme identification and confidence judgment, iterating until a preset judgment condition is met to obtain a target modulation identification result; and performing adaptive carrier fine phase-locking and blind equalization joint processing on the target modulation scheme to obtain a demodulated symbol sequence. This invention solves the coupling problem between carrier synchronization and modulation identification by combining hierarchical carrier synchronization, high-order cumulant feature identification, and adaptive fine phase-locking blind equalization, thereby improving demodulation reliability.

The application discloses a time deviation estimation method based on hysteresis back difference processing, and comprises the following steps: setting a processing threshold of hysteresis back difference according to a symbol rate of a communication signal; and processing the polarity of a subsequent time deviation estimation value in a hysteresis mode according to the polarity of a first time deviation estimation. The application sets a time deviation estimation polarity threshold in a hysteresis back difference mode, corrects abnormal polarity jitter of an estimation result of satellite time deviation caused by noise, and improves the correctness of a satellite-ground closed-loop time deviation adjustment by using the monotonic and slow change characteristics of a terminal time delay compensation value.

This invention provides a multi-format, multi-rate adaptive blind demodulation method, terminal device, and storage medium, belonging to the field of space laser communication technology. The invention acquires a baseband IQ signal; performs spectral analysis on the signal to obtain power spectrum characteristic parameters and estimate the 3dB bandwidth; calculates whether effective spectral peaks appear based on the characteristic parameters in the power spectrum, thereby determining the modulation format of the signal and estimating the frequency offset, and finding the maximum spectral line in the envelope spectrum, the position of which is the symbol rate spectral line; based on the modulation format and symbol rate estimation, carrier synchronization, timing synchronization, and symbol decision are performed on the signal to complete the demodulation. This invention enables demodulation of received signals by analyzing the spectral characteristics of the signal to determine the modulation format and estimate the symbol rate when the signal modulation format and symbol rate are unknown. The technology of this invention does not involve complex algorithms and is easy to implement in hardware.

The application discloses a low-orbit satellite Doppler estimation demodulation method and equipment. It relates to high dynamic synchronization technology and is suitable for application in low-orbit satellite communication. The application takes a satellite beacon as a pilot signal, quickly locks the satellite beacon through a phase discrimination method, and extracts a current Doppler frequency shift; then, according to the beacon frequency and the carrier frequency of the symbol rate of the received signal, the Doppler frequency shift of the received signal is determined; finally, through frequency down-conversion, the low symbol rate signal is converted into a baseband signal, and then timing recovery, carrier recovery, demapping and the like are carried out, so as to complete demodulation. The application is suitable for high dynamic conditions of low-orbit satellites, has a large Doppler estimation range and high precision.

The constellation optimization method for terahertz non-ideal channel based on deep learning belongs to the field of terahertz communication.The method of the present application is as follows: a transmitter based on DFT-s-OFDM modulation is designed to generate a transmission signal; a communication system model for terahertz non-ideal channel is established to obtain a received symbol sequence after the transmission signal is transmitted through the channel and processed by a receiver; a constellation optimization model based on a multi-layer neural network is constructed, a joint loss function containing three types of constraint terms is designed, adaptive optimization training is performed on constellation symbols, and an optimized constellation point sequence suitable for terahertz non-ideal channel is obtained; the optimized constellation points output by the multi-layer neural network are screened and constrained, projected and mapped to a standard QAM constellation to obtain a final constellation diagram satisfying the standard modulation format.The present application can reduce the symbol error rate under the condition of terahertz non-ideal channel, improve the robustness of the system to non-linear distortion and phase noise, and simultaneously consider power efficiency and implementation complexity.