Adjustable Dual-frequency FSS-amplifier Metasurface

With the rapid development of communications technology, there are more and more electromagnetic waves of different frequencies in space, the usual communications with fixed frequency suffer from a serious threat. Spatial filtering is used in electromagnetic transmission. Frequency selective surface (FSS) is one of them. Traditional frequency selective surface is always used in signal selection to filer clutter information and retain necessary signal. It is known that the propagation of electromagnetic waves in the normal media has losses because of the dielectric loss or magnetic loss of material. Traditional media material can not avoid the problem because the material permittivity and permeability are positive. All the material found in nature can be called loss type material. That leads to the electromagnetic waves transmission must be lower than 0 dB. Thus, signal always gets distortion as its transmission. In order to solve this problem that reducing the loss in the transmission process and keeping the electromagnetic filtering characteristics, a new thought which can achieve signal selection and amplification integrated is proposed in this letter. The double metallic wire frames structure is designed to achieve dual-band transmission firstly. To achieve transmission enhanced, the active structure based on the radio frequency circuit is coupled to the frequency selective surface. The frequency selective surface can select the electromagnetic waves from 1.4 GHz to 2.4 GHz and 4 GHz to 5.4 GHz above -3 dB. After amplified by the radio frequency circuit which using the Rf field-effect triode that working in the amplifier region, the electromagnetic waves can get high-gain transmission above 10 dB in the 1.0 G-2.4 GHz and 3.8 G-5.4 GHz.