Study On Focusing Method Based On Time Reversal Mirror And Its Application

The influence of multipath effects of electromagnetic wave propagation makes thesignal suffering from delay spread and distortion. The time reversal mirror technologyautomatically compensates the multipath which contributes to improving theperformance of energy focusing and target detection. According to the basic theory oftime reversal mirror technology, and the basic method of energy focusing and targetdetection, we have studied the theory and application on time reversal mirrortechnology for energy focusing and target detection. The main works of this thesis areas follows:(1) The basic theory of time reversal mirror(TRM) technology is studied and thecharacteristics of TRC(time reversal channel) is analyzed. The research shows that ifthe single antenna of TRC’s mainlobe is much larger than the sidelobe, theself-adaptive focusing can be realized, and by increasing the number of antenna andthe complexity of environment, we can also achieve self-adaptive focusing.(2) The application of time reversal mirror for energy focusing is studied.Compared with the traditional algorithms, the TRM can obtain focusing gain so thatthe performance of energy focusing can be improved. The time reversal iterationalgorithm and time reversal operator features decomposition algorithm of multipletarget environments are studied. In the low-altitude sea environment, single andmultiple targets of time reversal mirror for energy focusing are simulated. When thearray antenna reaches appropriate numbers, the focusing gain can be obtained. And thelarger the reflection coefficient of the sea surface is, the larger the focus gain will be.The more antennas are used, the larger TRM focusing gain will be obtained; and whenthe number of antennas is large enough, the focusing gain will approach to themaximum value. The multi-targets focusing simulation results show that about2dB offocusing gain will be obtained when the reflection coefficient of sea surface is0.5.Decomposition of the time reversal operator realizes the selective focusing. Due totime reversal energy focusing gain, the performance of energy focusing is improved.(3) The application of time reversal mirror for target detection is studied. According to the Newman-Pearson criteria and the basic principles of time reversalmirror technology, target detection probability and signal-to-noise ratio gain(SNRG)are studied at different number of antennas. The frequency selection time reversaltarget detection(FSTRD) is studied. The single antenna time reversal target detectionsimulation indicates that the SNRG of time reversal mirror technology can improve theperformance of target detection. By using the FSTRD, the performance is largelyimproved. With the increasing of the antennas number, the SNRG and target detectionprobability can become larger, and finally approach to be a stable value.