Research On Subspace-based Narrow-band Interference Rejection In Wide-band Shortwave Probe Systems

The wide-band shortwave probe system plays an important part in obtaining ionosphereparameters and research on characteristics of shortwave channel. But there is too muchnarrow-band interference in shortwave channel, which results in disadvantageous influences tothe capture of probe signal and the estimation of ionosphere parameter. The probe system oneselfanti-interferece is limited because of system complications and characteristic of shortwavechannel. Consequently, narrow-band interference rejection technique must be adopted toimprove quality of receive probe signal, which is very important to enhance performance of theprobe system.With characteristics of shortwave channel, this paper introduces principium of the probesystem and characteristic of the probe sequence first, emphasize analysises the baseband probesignal model and the narrow-band interference model, gets the conclusion that the energy ofinterference concentrates in a low subspace, which provides a theory for next interferencerejection algorithms. The simulation and data processing of our probe system both demonstratethat the interference model can simulate characteristic of practical interference in energydistributing and interference bandwidth. So that the interference model can provide anappropriate simulation environment.To reduce distortion of the probe signal rejected by the Hankel matrix SVD algorithm, thispaper proposes an improved narrow-band interference rejection algorithm of low distortion; andcombines actual characterstics of the probe signal and the narrow-band interference, the thesisputs forward a new interference dimension estimation algorithm based on energy distributing.This new rejection algorithm estimates useful power from the probe signal and noise subspace,attains rejection with low distortion by reserving the useful power. With the demand of real-timedata processing, the thesis proposes a fast and low distortion interference rejection algorithmbased on adapted subspace tracking according to the symmetry of the probe signal spectrum.This fast algorithm realizes unsymmetrical narrow-band interference rejection with lowdistortion.According to the principium of avoiding narrow-band interference, this paper proposes anew time domain algorithm of building probe sequences which can avoid the narrow-bandinterference based on mutually orthogonality of signal gained from interceptive matrx SVD, anddesigns a new improved scheme of the probe system. With the basic principle of TransformDomain Communication System(TDCS), the thesis sets up a frequency domain algorithm ofbuilding probe sequences which can avoid the narrow-band interference and then gives a newprobe scheme. The frequency domain algorithm uses Eigenvalue Value Decomposition(EVD)to separate narrow-band interference. The result of simulation indicates that these new sequencesobtain stronger ablity of anti-interference than traditional probe systems and provide a goodsolution for probe in the condition of intensive interference.Based on the measure platform of the wide-band shortwave probe system, the performanceof the low distortion algorithms toward to practical narrow-band interference is analyzed finally.The thesis discusses the characteristics of these algorithms in interference types, interferncequantity and time-consuming, and gives their applying scene.