Experimental and numerical studies on the receiving gain enhancement modulated by a sub-wavelength plasma layer

A novel technique based on sub-wavelength plasma structure effects on enhancement of RF communication signals on a receiving antenna is carried out in this paper in laboratory experiments and analyzed by corresponding numerical simulations.Considerable intensification on receiving signal gain up to -10 d B in comparison with that without the plasma modulation is observed experimentally in -1 GHz RF band,with an effective enhancement bandwidth of -340 MHz and the fractional bandwidth of -34%.Then,the optimal modulation parameters of plasma are further studied by a numerical simulation.It is shown that the number density,the layer thickness,and the collision frequency of the plasma,as well as the relative distance between the plasma layer and antenna synergistically affect the modulation.Compared to the metallic antenna with the same overall dimension,the modulated antenna covered by the subwavelength plasma structure features higher receiving efficiency and lower radar cross section in the studied RF band.The mechanism of the reception enhancement is further revealed by analyzing characteristics of electromagnetic scattering and electric field distribution in the subwavelength plasma layer.The results then exhibit scientific significance and application potential of sub-wavelength plasma modulation on compact receiving antennas with higher performance and better feature of radar stealth.

Anomalous acceleration of ions in a plasma accelerator with an anodic layer

In a plasma accelerator with an anodic layer(PAAL),we discovered experimentally the effect of‘super-acceleration'of the bulk of the ions to energies W exceeding the energy equivalent to the discharge voltage V_(d).The E×B discharge was ignited in an environment of atomic argon and helium and molecular nitrogen.Singly charged argon ions were accelerated most effectively in the case of the largest discharge currents and pressure P of the working gas.Helium ions with W〉eV_(d)(e being the electron charge)were only recorded at maximum pressures.Molecular nitrogen was not accelerated to energies W〉e V_(d).Anomalous acceleration is realized in the range of radial magnetic fields on the anode 2.8×10^(–2)≤B_(rA)≤4×10^(–2)T.It was also found analytically that the cathode of the accelerator can receive anomalously accelerated ions.In this case,the value of the potential in the anodic layer becomes higher than the anode potential,and the anode current exceeds some critical value.Numerical modeling in terms of the developed theory showed qualitative agreement between modeling data and measurements.