Abstract
The concept of a secure electromagnetic building (SEB) which can successfully prohibit wireless communications is presented. Wireless security is achieved using a slow phase-switching technique and can be realized by time-varying the transmission properties of a frequency-selective surface (FSS) to increase the bit error rate (BER) of the unwanted signal. Results are presented which demonstrate that a technique of phase switching at rates much lower than the baseband data rate can be used successfully. The system has been implemented using a reconfigurable dual-polarized dual layer FSS incorporating varactor diodes where over 100° of phase change can be achieved for voltage changes of $\pm 0 - 3V$ . A vector signal analyzer was used to evaluate the BER performance of the system for a GSM signal operating at 2 GHz. BERs are shown to be as high as 36% which are sufficient to successfully prohibit wireless communication. The solution is also shown to be robust over a wide range of incidence angles, which is important for real-world applications where the location of the prohibited wireless source may be unknown or mobile. Furthermore, as the system is reconfigurable, the building can be switched between secure and nonsecure modes.
Highlights
The proliferation of wireless communication devices is increasing globally which brings about the demand for increased signal coverage, network capacity and user quality of service, in densely populated areas
It can be expected that less interference to legitimate users would occur as 1) the Radar Cross Section (RCS) of the Secure Electromagnetic Building (SEB) surface would be less than that of a metal plate due to the reflection los of the SEB, 2) the relative phases of the received signals could produce destructive interference, 3) the locations of the Mobile Station (MS) and base station (BS) are likely to be such that the scattering from the SEB surface is non-specular resulting in a reduced RCS which would depend on d and incidence angles and 4) the assumption of flat metal plate scattering will give an underestimate of SIR as this does not take into account that the incident energy illuminating the SEB is redistributed over a broad frequency range once scattered
This paper introduces the concept of a secure electromagnetic building which can successfully prohibit wireless communications
Summary
The proliferation of wireless communication devices is increasing globally which brings about the demand for increased signal coverage, network capacity and user quality of service, in densely populated areas. Shielding is simple in theory but can be difficult to achieve in practice in high signal coverage areas, due to the very high attenuation levels that may be required to effectively block a communications signal. There has been significant research into reconfigurable FSS which could have applications for smart buildings [11]–[20] and miniaturized FSS design which would be applicable for low frequency in-building communications applications [21]–[24]. The application of stopping or blocking communications signals through the use of FSS is more problematic, in high signal strength areas due to the high sensitivity of modern mobile receivers which can operate with powers as low as -120dBm or less. The remainder of the paper sets out the fundamental concept, system simulations, application specific implications, FSS design and practical demonstration of the proposed system
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