Research And Application Of Multi-Functional Frequency Selective Surfaces

Frequency selection surfaces?FSSs?have a wide range of applications in the field of military and civilian with unique electromagnetic properties.In this thesis,we mainly study the application of frequency selective surfaces in the field of communication,that is,multi-functional frequency selective surface radome and energy saving glass with frequency selective surface structure.As a precision device in wireless communication systems,antenna usually needs radome to protect itself from outside interference.In addition,because of antenna's shortcomings,such as low gain,secondary radiation interference and so on,multi-functional radome can be designed to solve the above problems.With the exploration and research about 5G technology,the demands for adaptive beam and multi-beams,it requires that each element of a large-scale antenna array has a separate radio-frequency?RF?channel,which requires high performance filter devices.The traditional RF circuit is difficult to be used because of the small space in millimeter RF front-end.So we adopt the concept of multi-function FSS radome to achieve the overall control and integrated design of antenna and filter,which will greatly simplify the design of each RF channel front-end.Based on the above challenges,this thesis designs a multi-functional FSS radome which has low insertion loss characteristics in the working pass-band,a steep out-of-band suppression characteristics and wide bandwidth suppression in out of working band,and a second harmonic suppression characteristics.Firstly,we design a FSS element structure with pass-band characteristics.The steep out-of-band suppression and suppression bandwidth of the structure is realized by introducing the zero point method.Then,the FSS structure with the second harmonic suppression characteristic is designed.In this design,the passb-and structure and the second harmonic suppression structure are designed separately to control the two structures to achieve frequency band grafting characteristics.Finally,the multi-functional FSS radome is simulated and measured with 0°,15°and 45°scanning antennas.The measurement results show that the designed multi-functional FSS radome has very low insertion loss in the pass-band.When the antenna scans to 0°direction,the insertion loss of the pass-band can be controlled within 1.7dB.For 15°scanning direction,the insertion loss of the pass-band can be controlled within 1.3dB.For 45°scanning direction,the insertion loss of the pass-band can be controlled within 3.6dB.The radome has a steep out-of-band suppression characteristics and wide bandwidth suppression in out of work band.The transition band is0.039 f₀,the near-end suppression bandwidth is0.17 f₀,and the radome has a 20dB suppression in the second harmonic band.Note that in the future 5G applications,the multi-function FSS radome can replace the traditional RF front-end filter to achieve better filtering functions.In this thesis,we apply the FSS structure to energy-saving glass of buildings to improve the transmission efficiency of electromagnetic waves.Energy-saving glass is coated with one or more layers of metal alloy or metal compound on its surface,so this kind of glass can achieve the role of thermal and insulation.However,the propagation of electromagnetic waves is hindered owing to the metal compounds on the surface of the glass.Therefore,Based on ITO energy-saving glass,this thesis designs a kind of FSS structure on the coating,so that the electromagnetic waves we needed can transmit through the energy-saving glass.Finally,the simulation and measurement results show that the electromagnetic waves in 2-6GHz band can successfully go through the ITO energy-saving glass,and the transmission efficiency can achieve 30%to 40%.It is worth pointing out that due to the etched area is about 27%,the integration with ITO FSS has less effect on the energy-saving efficiency.