| As one of the most important components of earth observation satellite,satellite data transmission system plays an important role in space-ground data distribution and realtime space-based information applications.With the increase of user demand and the change of satellite application mode,satellite data transmission system faces great challenges.Firstly,the original input data rate has reached tens of Gbit/s.There are already technical bottlenecks for the traditional data transmission system,which pursues high bit rate by employing higher order modulation and higher transmission frequency.Secondly,the traditional point-to-point transmission mode between satellite and ground station cannot meet the requirements of multi-point transmission from satellite to different ground platforms in data distribution application scenarios.To address the problems above,the thesis focuses on the high bit rate satellite data transmission technique and the adaptive receiving technique of homologous satellite data for receivers with different capabilities,under the condition of time-delay Doppler satellite channel.A new satellite data transmission mechanism based on linear frequency modulation(LFM)signal with high reliability and low complexity has been innovatively proposed.The main contents and innovative contributions of this paper include:1.A novel satellite data transmission mechanism with high bit rate based on cyclic time-shift LFM is proposed.Under the time-delay Doppler channel in satellite-ground transmission,the high-speed satellite signal cannot be correctly distributed to different application platforms due to the serious distortion and inter-symbol interference(ISI).Aiming at this problem,a novel satellite high-speed data transmission mechanism is proposed,in which the LFM with cyclic time shift is innovatively applied in the carrier modulation of satellite signal.By optimizing the sampling rate and time-bandwidth product of signals,based on non-coherent pulse compression and combination of specially designed window function,the proposed mechanism reduces the influence of pulse compression sidelobe and solve the reception problem of various ground platform in time-varying channel.Moreover,it also provides necessary control parameters for engineering realization.2.A cyclic time-shift LFM based incoherent burst pulse multicarrier communication mechanism is proposed.Considering the low ratio of bandwidth utilization of LFM carrier,a cyclic time-shift LFM based incoherent burst pulse multicarrier communication mechanism is proposed,in which scalable quality signals are designed and transferred.At the sending end,N time-shift signals superimposed together and transmitted within one cycle time;at the receiving end,signal detection and reception are based on the frequency domain pulse compression,and the receiving terminal with different performance can obtain the image data that matching its resolution demand.Theoretical derivation and simulations show that the proposed multi-carrier mechanism conforms to the optimal transmission form under the double dispersion channels and can effectively solve the problem of low ratio of bandwidth utilization of LFM carrier,while reduce the complexity of receiving equipment.3.A novel ISI suppression method based on warping mapping spectral transform is proposed.In order to suppress the serious ISI caused by overlapping transmission and multipath environment,a novel warping mapping spectral transform-based method is proposed.In this transform,the nonlinear homeomorphism mapping between domains is generated into a new transform domain,in which the local resolution of the signal is greatly improved compared with that in the original transform domain(frequency domain).Based on reasonable design of θ(v)function in the domain transform,the ISI can be reduced to an acceptable range in engineering reality.Theoretical analysis and simulations demonstrate the effectiveness of proposed ISI suppression method.4.A new channel linearization method based on homotopy perturbation nonlinear algorithm is proposed.In order to suppress the nonlinear distortion caused by the strong interference that entering the front-end,the homotopy perturbation method is employed to analyze the nonlinear product in the channel.Firstly,a nonlinear system model is established from the perspective of predistortion.Then,through theoretical derivation,it is concluded that the nonlinear component of the channel is mainly determined by the first-order precise solution,and the main contribution of spectrum spread comes from the nonlinear term.On the basis of theoretical analysis,an engineering realization scheme of nonlinear interference suppression based on warping mapping Fourier filtering is proposed.It is worth mentioning that the proposed scheme has the advantage of simple implementation.Simulation analysis shows that the proposed has remarkable effect on suppressing the nonlinear products caused by strong interference,while traditional predistortion method cannot eliminate the strong interference effect.The proposed satellite data transmission technique has good performance and is closely related to the engineering reality.All theoretical research and simulation analysis are carried out around the key design elements such as adaptability of satellite-ground channel,high rate of spectrum utilization,reliable distribution of homologous data,resistance to burst strong interference,low complexity and low cost,which has important guiding significance for engineering development. |
