Low-band frequency selective surface with minimized cell sizes

Abstract

The invention provides a low-band frequency selective surface with minimized cell sizes. The low-band frequency selective surface comprises a printed circuit board (PCB). An upper conductive layer is arranged on the front surface of the PCB, and a lower conductive layer is arranged on the back surface of the PCB. The upper conductive layer consists of upper periodical cells which are periodically arranged. The lower conductive layer consists of lower periodical cells which are periodically arranged. The upper and lower periodical cells are provided with vertically aligned conducting strips which are surface-surface coupled to form high distributed capacitance to reduce the resonance frequency of the frequency selective surface. The more than 20*20 upper periodical cells correspond to the lower periodical cells. According to the frequency selective surface, the vertically aligned conducting strips are arranged in the upper and lower conductive layers, and are surface-surface coupled to form the high distributed capacitance, so that the resonance frequency of the frequency selective surface is remarkably reduced. The frequency selective surface is insensitive to the polarization characteristics of electromagnetic waves, and the passband characteristics of different polarized electromagnetic waves (transverse electric (TE) waves and transverse magnetic (TM) waves) are substantially the same.

Description

technical field [0001] The invention belongs to the field of electromagnetic compatibility, and in particular relates to a low-frequency frequency selective surface with miniaturized unit size. Background technique [0002] At present, for electronic equipment with a low working frequency band (300MHz~1GHz), it is difficult to develop a corresponding passband frequency selection surface radome, mainly for the following reasons: firstly, it can be known from the working principle of FSS that the unit perimeter It is approximately proportional to the free-space wavelength of the electromagnetic wave. The size of the periodic unit of the low resonant frequency FSS will be large. Taking the FSS with a resonant frequency of 300MHz as an example, the free-space wavelength of its electromagnetic wave is about 1000mm, and the variable length of the periodic unit is about 250mm, which is almost the same as the size of the equipment antenna. The frequency selective surface made by us...

AI Technical Summary

Problems solved by technology

Taking the FSS with a resonant frequency of 300MHz as an example, the free-space wavelength of its electromagnetic wave is about 1000mm, and the variable length of the periodic unit is about 250mm, which is almost the same as the size of the equipment antenna. The frequency selective surface made by using this periodic unit Very large area, difficult and expensive to install

In addition, due to the large unit period, when the electromagnetic wave is obliquely incident on the frequency selective surface, the passband frequency of the FSS will change significantly and grating lobes will appear, and its passband performance is poor.

[0003] At present, there have been frequency selective surfaces that reduce the size of the periodic unit of the frequency selective surface by folding the internal structure of the unit, but because it still generates capacitance through the side-to-side coupling between the edges of different conductive sheets in a single conductive layer, the distributed capacitance Small, after using this method, the unit size of the 300MHz ~ 1GHz frequency selective surface is still large

Although loading the lumped capacitor device can significantly reduce the unit size of the frequency selective surface, the performance parameters of the lumped capacitor device will change significantly with the change of ambient temperature and humidity, which will make the passband characteristics of the frequency selective surface change significantly. Change

In addition, the life of lumped capacitors will be significantly shortened under the action of strong electromagnetic fields, so it is not suitable for radome, reflector, etc. of electronic equipment.

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