Frequency Selective Surfaces for Long Wavelengths

移动通信和无线计算机联网已经非常流行，用户数量和系统类型将继续增加。每个系统都需要使用某些传输频率，这些频率必须以某种方式分开以避免干扰。向无线电频谱发放许可证的政府机构英国通信办公室(Ofcom)正开始放松对无线电频率使用过程的监管，至关重要的是要设计出一种方法，使无线电环境既不受干扰，又更安全，不受窃听。此外，不应被允许使用电话的囚犯正在使用走私进入监狱的移动电话。这些手机被用来在外面组织犯罪，走私毒品，协调逃跑和骚乱。这引起了监狱当局和英国政府的高度关注，因为在不干扰监狱附近无辜用户手机的情况下，从技术上讲很难阻止手机通讯。与上述问题平行的是，现代建筑内衬着一层金属隔热层。这一层屏蔽了建筑内部，可以显著降低通过内部的无线电信号的强度。这可能会减少建筑物内应急服务部门使用的无线电系统的覆盖范围，使人员处于危险之中。这项研究旨在创建频率选择性表面(FSS)，以过滤移动频率上的无线电信号，同时通过授权服务使用的频道。FSS的设计将是卷曲和交织，以压缩其大小，并将安装在金属屏蔽墙的小孔中。通过将开关二极管集成到设计中，将以指定的隔离级别为目标，并使性能具有适应性。将进行计算机模拟，以预测信号通过FSS和进入房间的传播。

Mobile communications and wireless computer networking are already enourmously popular with user numbers and system types set to continue increasing. Each system requires the use of certain transmission frequencies which must be separated in some way to avoid interference. OFCOM, the government body that licences the radio spectrum is beginning to deregulate the process of radio frequency usage and it is vital to devise a means of making the radio environment both more immune from interference and safe from eavesdropping. Also prisoners who should not be allowed access to telephones are using mobile phones smuggled into prisons. The phones are used to organise crime outside, smuggle in drugs and coordinate escapes and riots. This is of great concern to the prison authorities and the UK government as it is technically difficult to stop mobile phone communications without interfering with the phones of innocent users near the prisons. Parallel to the above issues is the fact that modern buildings are lined with a metallic layer for thermal insulation. This layer screens building interiors and can significantly reduce the strength of radio signals passing inside. This can reduce the coverage of radio systems used by the emergency services within buildings placing personnel at risk. This research seeks to create Frequency Selective Surfaces (FSS) to filter out radio signals at mobile frequencies while passing channels used by authorised services. The FSS designs will be convoluted and interweaved to compress their size and will be mounted in small apertures in metal screened walls. A specified isolation level will be aimed for and the performance will be made adaptable by integrating switching diodes to the design. Computer simulations will be made to predict the propagation of signals through the FSS and into rooms.