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The Aerospace Corporation was tasked to assess radio frequency (RF) blackout phenomena caused by plasma generation around vehicles during reentry and presently known methodologies for mitigation of this condition inhibiting communications. The purpose was to understand these phenomena and mitigation approaches applicable to reusable launch vehicles (RLVs) used for commercial space. The viability and limitations of selecting frequency bands amenable to continuous communication in presence of plasma sheaths were assessed and mitigation recommendations provided. The ability to predict the ionized flow field for classes of vehicles most likely to emerge as hypersonic space transportation systems, with sufficient accuracy to identify the altitudes of blackout onset and recovery within reasonable bounds, has been demonstrated for altitudes greater than approximately 100 kft. This highaltitude regime is the most likely for future space transportation due to low g forces and low heat loads. For the lower, suborbital altitudes, many commercial RLVs will not be subjected to RF blackout because their relatively low velocities will not create conditions that generate plasma. Determination of the interaction of RF with a known ionized layer, including reflection, attenuation, refraction, high-power breakdown limits, and also effects of the plasma on the antenna characteristics, have been demonstrated successfully. Analytic codes are available to evaluate these phenomena. Approaches for mitigating the interruption of communications due to interactions of plasma electrons with RF signals are reviewed. The most promising are: aerodynamic shaping, injection of quenchants, use of magnetic windows, and use of high frequencies. 12

In this paper, a compact, low-profile, coplanar waveguide-fed metamaterial inspired dual-band microstrip antenna is presented for Wireless Local Area Network (WLAN) application. To achieve the goal a triangular split ring resonator is used along with an open-ended stub. The proposed antenna has a compact size of 20 × 24 mm2 fabricated on an FR-4 epoxy substrate with dielectric constant (εr) 4.4. The antenna provides two distinct bands I from 2.40 to 2.48 GHz and II from 4.7 to 6.04 GHz with reflection coefficient better than −10 dB, covering the entire WLAN (2.4/5.2/5.8 GHz) band spectrum. The performance of the proposed metamaterial inspired antenna is also studied in terms of the radiation pattern, efficiency, and the realized gain. A comparative study is also presented to show the performance of the proposed metamaterial inspired antenna with respect to other conventional antenna structures in terms of overall size, bandwidth, gain, and reflection coefficient. Finally, the antenna is fabricated and tested. The simulated results show good agreement with the measured results.

In the past few decades, metamaterial absorbers (MA) have become an important area of research due to their potential application as ultrathin perfect absorbers. There are various approaches proposed in the literature to obtain multiband and broadband absorption characteristics. This paper presents all the different approaches followed by different authors along with their respective drawbacks and advantages. Metamaterial absorbers have numerous applications in today's technological advancement. This paper presents the review of literature on previously proposed MA applied for radar cross-section reduction and used as sensors in several applications. The aim is to help the user choose a suitable approach for particular specifications and also develop new devices in the future.