Security information factor based airborne radar RF stealth

Radar radio frequency （RF） stealth is very important in electronic war （EW）, and waveform design and selection. Existing evaluation rules of radar RF stealth include too many parameters of radar and interceptors, such as Schleher interception factor, which makes it difficult to evaluate radar RF stealth technologies if interceptor parameters are unknown. In communication, security capacity has been presented to describe the possible ability to communicate in complete security. Since the essential of the secu- rity capacity is to have the interceptor get none valued information from the emitter, this paper is proposed to study security infor- mation factors taking advantage of mutual information to evaluate radar RF stealth under some conditions. Through analyzing mutual information obtained by the radar and the interceptor, this paper defines the security information factor with and without cooperative jamming. Furthermore, this paper deduces the ratio of the match filter to the match incoherent filter and discuss mutual information received by the interceptor. Numerical simulations illustrate radar RF stealth effects based on the security information factor concept under different conditions.

Large Scale Antenna Arrays with Increasing Antennas in Limited Physical Space

Large Scale multiple input multiple output(MIMO) systems have recently emerged as a promising technology for 5G communications.While they have been shown to offer significant performance benefits in theoretical studies,the large scale MIMO transmitters will have to be deployed in the limited physical space of today's base stations(BSs).Accordingly,this paper examines effects of deploying increasing numbers of antennas in fixed physical space,by reducing the antenna spacing.We focus on the resulting performance of large-scale MIMO transmitters using low complexity closed form precoding techniques.In particular,we investigate the combined effect of reducing the distance between the antenna elements with increasing the number of elements in a fixed transmitter space.This gives rise to two contradicting phenomena:the reduction of spatial diversity due to reducing the separation between antennas and the increase in transmit diversity by increasing the number of elements.To quantify this tradeoff,we investigate densely deployed uniform antenna arrays modelled by detailed electromagnetic simulation.Our results show the somewhat surprising result that,by reducing the separations between the antennas to significantly less than the transmit wavelength to fit more antennas,the resulting system performance improves.