Design And Implementation Of Multi-band Frequency Selective Surface(FSS)

Frequency selective surface(FSS),a two-dimensional or three-dimensional structure arranged periodically,essentially a spatial filter.It has the characteristics of selective transmission or reflection of electromagnetic waves at different frequencies,polarization,and incident angles.It has been widely used in stealth technology,high gain antenna and other fields.In this paper,we mainly study the method of reducing the pitch and profile of the frequency selective surface cells.The main research work includes the following aspects:(1)Starting from the working principle of frequency selective surface,the effects of element shape,miniaturization,arrangement,media loading and incident wave on the performance of FSS were analyzed;The influence of grating lobes and surface waves on FSS performance was described;The classical analytical methods such as the subdivision method,mode matching method,spectral domain method,and also the three main methods of electromagnetic simulation software including moment method,finite element method,and finite-difference time-domain method were analyzed.(2)The principle of the miniaturized element frequency selective surface(MEFSS)was described.From the engineering practice,a band-pass MEFSS was designed in the X-band.When electromagnetic wave is incident vertically,-1dB relative bandwidth reaches 40%in the direction of the offset normal line.In the case of oblique incidence within 40 degree,its-1dB relative bandwidth is still 35%.(3)To reduce the distance between the elements to improve the angle stability,a low-profile X\Ku\Ka three-band dual-polarized FSS with large angle stability was designed.The X\Ku band is well within the incident angle 0°-80° and the Ka band is well within the incident angle 0°-60°,the measured and simulated results are consistent.In the simulation,the FSS is made into the antenna sub-reflection surface and the metal sub-reflection surface for comparison simulation,which proves that it can be used in engineering applications.(4)Theory of fractal technology is introduced and applied to FSS design,which reduce FSS unit size.X/Ka/W three-band frequency selective surface is designed using single-layer loaded high dielectric constant dielectric board.The unit spacing was miniaturized to ?/13 with a thickness of only ?/50,excellent angular stability was obtained.At incidence angle of 0°-80°,the resonance point of the X/Ka band was stabilized,the W-band grating lobe was suppressed,and a good reflection band was obtained with different polarization.The large angle stability of electromagnetic waves can be used in X/Ka/W three-band antennas.