The propagation characteristics of electromagnetic waves through plasma in the near-field region of low-frequency loop antenna

Abstract

A high-speed vehicle flying through the atmosphere between 100 and 20 km may suffer from a “communication blackout.” In this paper, a low frequency system with an on-board loop antenna to receive signals is presented as a potential blackout mitigation method. Because the plasma sheath is in the near-field region of the loop antenna, the traditional scattering matrix method that is developed for the far-field region may overestimate the electromagnetic (EM) wave's attenuation. To estimate the EM wave's attenuation in the near-field region, EM interference (EMI) shielding theory is introduced. Experiments are conducted, and the results verify the EMI shielding theory's effectiveness. Simulations are also conducted with different plasma parameters, and the results obtained show that the EM wave's attenuation in the near-field region is far below than that in the far-field region. The EM wave's attenuation increases with the increase in electron density and decreases with the increase in collision frequency. The higher the frequency, the larger is the EM wave's attenuation. During the entire re-entry phase of a RAM-C module, the EM wave's attenuations are below 10 dB for EM waves with a frequency of 1 MHz and below 1 dB for EM waves with a frequency of 100 kHz. Therefore, the low frequency systems (e.g., Loran-C) may provide a way to transmit some key information to high-speed vehicles even during the communication “blackout” period.

Mitigation of blackout problem for reentry vehicle in traveling magnetic field with induced current

“…Figure 10 shows the relation between attenuations and reentry altitude. The plasma parameters at different reentry altitudes used in the proposed model are given in table 3 [32], and a comparison of results of the proposed model and the RAM-C measurement data is presented in table 4. It can be found that the attenuation results without applying the TMF are consistent with the measurement data.…”

Experimental Investigation of the Dynamic Effects of Time-Varying Plasma on Low-Frequency Electromagnetic Wave Propagation

“…As a result, the communications between the vehicle and ground stations are cut off, which is often known as "radio blackout" [1]- [4]. Several methods have been proposed to mitigate radio blackout, such as electrophilic injection [5], magnetic field control [6], the high-frequency (HF) propagation method [7], and the low-frequency (LF) propagation method [8].…”

“…In the last decade, the LF propagation method has been considered a potentially feasible method for maintaining lowrate communications [8]- [11]. The EM wave frequency in the LF propagation method (in the range of 0.1 MHz to 30 MHz) is much lower than the plasma frequency, for which the wavelength is much larger than the size of the plasma sheath.…”

“…The EM wave frequency in the LF propagation method (in the range of 0.1 MHz to 30 MHz) is much lower than the plasma frequency, for which the wavelength is much larger than the size of the plasma sheath. To deeply understand the physical process of the interactions between LF EM waves and the plasma sheath, several propagation models were proposed, including flat plasma [8], spherical shell plasma [9], and cylindrical enveloping plasma [10]. At the same time, corresponding numerical simulations and experiments were conducted to verify these models [8]- [10].…”

“…To deeply understand the physical process of the interactions between LF EM waves and the plasma sheath, several propagation models were proposed, including flat plasma [8], spherical shell plasma [9], and cylindrical enveloping plasma [10]. At the same time, corresponding numerical simulations and experiments were conducted to verify these models [8]- [10]. The above research indicates that the magnetic field attenuation of the LF EM wave in the plasma sheath is much smaller than the electric field attenuation.…”