Research On Mutual Coupling Calibration Method Of Virtual Antenna

In recent years, with the increase in wireless communication equipment, electromagneticcompatibility problems have been arousing universal attention home and abroad. There are alot of antennas in small spaces such as ships, how to reduce the electromagnetic interferenceeffectively has become an important issue. Smart antenna system, as one of the keytechnologies of the wireless communication system, is a study hotspot, which makes thedirection of the main lobe of the antenna to align a desired signal, and adaptively suppressingmulti-user interference. However, the Smart antenna does not work when the number of thesignal is more than the number of array elements. In order to solve the problem, the virtualantenna technology came into being. By pre-processing algorithm such as interpolationtransform and high-order cumulants, the antenna freedom degree can be increased, and theinterference signal, which is caused by the number of the signal is more than the number ofarray elements, can be suppressed effectively by combining pre-processing algorithms withbeamforming algorithms and spatial spectrum estimation algorithms. In other words, thenumber of array elements to deal with signal source will be less. In this way, the virtualantenna can reduce the antenna radiation energy and interference coupling, therefore, thevirtual antenna is a possible way to reduce the electromagnetic interference.This research paper explored such challenges using higher order cumulants andinterpolation transform method to increase the freedom of array antenna, and two ways areused in the DOA algorithm. Through theoretical analysis and simulation experiments, we canincrease the degree of freedom of virtual antenna and the expansion of the effective apertureof the antenna. Then the two methods are mainly researched, we can get the advantages anddisadvantages of the two methods and applicable range by simulation.The above two methods are used under ideal conditions. Nevertheless, in engineeringapplications, there are various kinds of errors inevitable, and the virtual antenna is unable todistinguish the signal sources. The two uniform linear array virtual antenna mutual couplingself-tuning algorithms are based on combination of Fourth-order cumulants and second-orderstatistics of the "decoupling" self-correction algorithm. To exclude mutual couplingcoefficient influence of direction finding, the two methods deform the steering vector of arraymutual coupling. We present two new calibration methods that are based on the fourth-order cumulants of virtual antenna array for a uniform linear array and a new calibration methodthat based on a uniform circular array. The simulation results demonstrated that all calibrationmethods of virtual antenna array are able to increase the degree of system freedom and extendthe antenna effective aperture. In addition, arrival direction of signal sources can be accuratelycalculated when the mutual coupling is presented.