Device without blocking wireless signals based on impedance matching

Abstract

The present invention provides a device without blocking wireless signals based on impedance matching. The device is constructed by periodically stacking two building materials with different dielectric constants in the same direction. The device without blocking wireless signals based on impedance matching can be designed as a wall body, and can improve wave transmission of microwaves to ensure that wireless signals won't be blocked at any incident angle, thereby achieving the unblocked transmission of wireless signals. Furthermore, compared with metal hole arrays, the component materials of the devices can include polypropylene and concrete, that expands the applications from micro circuit electronic devices to macro walls, and greatly reduces the manufacturing and maintenance cost.

Claims

1. A device without blocking wireless signals based on impedance matching, the device comprising periodically stacked two building materials with different dielectric constants in the same direction, wherein the two building materials are polypropylene having a dielectric constant of 2.3 and concrete having a dielectric constant of 9, and wherein the period length of the two building materials is 4.25 cm.

2. The device without blocking wireless signals based on impedance matching as claimed in claim 1, wherein the two building materials are periodically stacked in an alternate mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of the device of present invention;

(2) FIG. 2 shows a minimum period structure of the device of the present invention;

(3) FIG. 3 shows the constant-impedance curve distribution of a minimum periodic structure in one fourth of a k space of the present invention;

(4) FIG. 4 is an equal frequency contour diagram corresponding to the constant-impedance curve distribution shown in FIG. 3; and

(5) FIG. 5(a) is a structure simulation diagram, FIG. 5(b) represents full-angle transmission response and frequency response, wherein only .sub.1 is included, FIG. 5(c) represents a transmission situation of angle and frequency response, wherein only .sub.2 is included, and FIGS. 5(d) and (e) show the frequency- and angle-dependent transmission diagrams of a composite material for TE and TM polarization incidence, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The invention will be further illustrated in more detail with reference to the accompanying drawings and embodiments. It is noted that, the following embodiments only are intended for purposes of illustration, but are not intended to limit the scope of the present invention.

(7) A device without blocking wireless signals based on impedance matching of a preferred embodiment of the present invention, is formed by periodically stacking polypropylene (dielectric constant .sub.1=2.3) and concrete (dielectric constant .sub.2=9) in the same direction in an alternate mode. As shown in FIG. 1, the polypropylene and the concrete are arranged as ABABABABA . . . , and are arranged periodically only in the z direction, wherein d.sub.AB=a with a being the period length.

(8) In order to study the impedance when electromagnetic waves enter the composite material of the present invention, a multi-physical field simulation software COMSOL Multiphysics software based on finite element method is used for theoretical simulation.

(9) To simplify the operation, a minimal periodic repeating unit is selected for study, as shown in FIG. 2.

(10) A broadband and wide-angle high transmission composite material indicates that its impedance is completely match with the impedance of the background medium. Because a symmetric structure is selected, and an electric (or magnetic) field is uniformly distributed at its boundary, on the basis of the definition of impedance in electrodynamics, the impedance of the composite material is calculated as followings:

(11) $\begin{array}{cc}{Z}_x^{\mathrm{PC}}{|}_{x_{\mathrm{incident}}}=\frac{{}_L{E}^{\mathrm{PC}}.Math.\hat{z}\mathrm{dy}}{{}_L{H}^{\mathrm{PC}}.Math.\hat{y}\mathrm{dy}},Z_y^{\mathrm{PC}}{|}_{x_{\mathrm{incident}}}=\frac{{}_L{E}^{\mathrm{PC}}.Math.\hat{z}\mathrm{dy}}{{}_L{H}^{\mathrm{PC}}.Math.\hat{x}\mathrm{dy}}.& \left(1\right)\end{array}$

(12) Z represents the impedance. E and H represent the electric and magnetic fields, respectively. x represent an incidence direction, y represents a direction vertical to the incidence direction, and z represents a direction perpendicular to the xy plane. The PC represents a short name (Photonic crystals) of the material. Meanwhile, the air impedance can be obtained as:

(13) $\begin{array}{cc}{Z}_x=\left|Z_0\right|=\frac{{}_0}{\sqrt{k_0^2-k_y^2}},& \left(2\right)\end{array}$

(14) where represents a circular frequency. .sub.0 represents a magnetic permeability in vacuum. FIG. 3 shows the constant-impedance curve distribution of the periodic structure in one fourth of the k-space. It can be seen that the deepest black region represents a place where the impedance of the composite material (i.e., photonic crystal) is equal to the impedance of air. The equal frequency contour of the photonic crystal is shown in FIG. 4, where the black solid line shows the frequency for exact impedance matching (f=8*c=2.4 GHz, c=3 e.sup.8). The frequencies in a range from 0.25 to 0.75 on the horizontal axis in FIG. 4 can almost enable the impedance to basically match with the air impedance, thereby achieving the wide-angle broadband and unpolarized transmission of light waves in optical frequencies.

(15) Referring to the structure simulation diagram of FIG. 5(a), .sub.1=2.3, .sub.2=9, and the period a is 4.25 cm, wherein the dark grey represents the .sub.1 portion, d1=0.6 a, the light grey represents the .sub.2 portion, d2=0.4 a, and represents an incident angle. FIG. 5(b) represents the full-angle transmission response and frequency response, wherein only .sub.1 is included (10-layer transmission). FIG. 5(c) represents a transmission situation of angle and frequency response, wherein only .sub.2 is included (also 10-layer transmission). It can be seen that at 2 GHz to 2.7 GHz, the transmission in the presence of only one medium is not continuous, the angle of a high-permeability portion is also very narrow, but when the two media are arranged as the periodic structure (10-layer stacking) shown in FIG. 5(a), the inter-frequency discontinuous transmission can be partially eliminated, the range of the corresponding super-penetration angle becomes wider. As shown in FIGS. 5(d) and (e), nearby a Wi-Fi transmitting frequency of 2.4 GHz, both TE- and TM-polarized waves can achieve almost perfect transmission from 0 to 90 degree, thereby achieving invisibility for the Wi-Fi singles at this frequency. Furthermore, the composite material also has a relatively wide frequency response, and the 4G signal wavebands of China's three major communication operators can be basically covered.

(16) Meanwhile, the materials for manufacturing the structure are also very common in daily life, mainly including polypropylene (.sub.1=2.3) and concrete (.sub.2=9) which are common building materials. The concrete, as a wall building material, has good durability, good plasticity and high strength. PP plastic (i.e., polypropylene) has low density, good formability, mechanical properties and bending fatigue resistance, and is non-toxic and anti-voltage, heat-resistant and corrosion-resistant, and has basic characteristics of wall materials. Also, the two materials are very cheap, and the process for manufacturing the structure is easy (the multilayer stacking depending on the specific thickness of the wall), and thus the construction cost can be greatly reduced.

(17) The above description is only preferred embodiments of the present invention and not intended to limit the present invention, it should be noted that those of ordinary skill in the art can further make various modifications and variations without departing from the technical principles of the present invention, and these modifications and variations also should be considered to be within the scope of protection of the present invention.