# Patent

## Title
Antenna module and design method thereof

## Abstract

An antenna module is provided. The antenna module includes a reflective superstrate, an antenna substrate, an antenna and a reflective pattern. The antenna is disposed on the antenna substrate. The reflective pattern is formed on the reflective superstrate, wherein a reflection gap is formed between the reflective superstrate and the antenna substrate. The reflective pattern provides a first reflection phase angle, the antenna substrate provides a second reflection phase angle, the first reflection phase angle includes a first determined phase angle Δ1, the first determined phase angle Δ1 is not 0°, the first reflection phase angle is about −(180°−Δ1), the second reflection phase angle includes a second determined phase angle Δ2, the second reflection phase angle is about −(180°−Δ2), a dimension of the reflection gap is directly proportional to a total predetermined phase angle Δ=Δ1+Δ2, and the total predetermined phase angle is between 0° ̃90°.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This Application claims priority of Taiwan Patent Application No. 098121311, filed on Jun. 25, 2009, the entirety of which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna module, and in particular relates to an antenna module having an Electromagnetic Band Gap cover.
2. Description of the Related Art
FIG. 1a shows a conventional antenna module 1, comprising a cover 10, an antenna substrate 20 and an antenna 30. The antenna 30 provides a wireless signal 2. The cover 10 increases reflection times of the wireless signal 2 to increase the energy intensity thereof. The cover 10 has a first reflection phase angle Φ1, and the antenna substrate 20 has a second reflection phase angle Φ2. The first reflection phase angle Φ1 is about −180°. The second reflection phase angle Φ2 is about −180°. To regulate the reflected wireless signal 2 in phase, a formula (A) is utilized:




  
    
      
        
          
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According to the formula (A), a distance d1 between the cover 10 and the antenna substrate 20 is at least equal to half of a wavelength of the wireless signal 2.

FIG. 1b shows another conventional antenna module 1′, comprising a cover 10, an antenna substrate 20′ and an antenna 30. The antenna 30 provides a wireless signal 2. The cover 10 increases reflection times of the wireless signal 2 to increase the energy intensity thereof. The cover 10 has a first reflection phase angle Φ1, and the antenna substrate 20′ has a second reflection phase angle Φ2′. The first reflection phase angle Φ1 is about −180°. The second reflection phase angle Φ2′ is about 0°. To regulate the reflected wireless signal 2 in phase, a distance d2 between the cover 10 and the antenna substrate 20′ is at least equal to a quarter of a wavelength of the wireless signal 2.
Conventionally, the distance between the cover 10 and the antenna substrate 20(20′) is large, and the volume of the antenna module is thus large.
BRIEF SUMMARY OF THE INVENTION
A detailed description is given in the following embodiments with reference to the accompanying drawings.
An antenna module is provided. The antenna module comprises a reflective superstrate, an antenna substrate, an antenna and a reflective pattern. The antenna is disposed on the antenna substrate. The reflective pattern is formed on the reflective superstrate, wherein a reflection gap is formed between the reflective superstrate and the antenna substrate. The reflective pattern provides a first reflection phase angle, the antenna substrate provides a second reflection phase angle, the first reflection phase angle comprises a first determined phase angle Δ1, the first determined phase angle Δ1 is not 0°, the first reflection phase angle is about −(180°−Δ1), the second reflection phase angle comprises a second determined phase angle Δ2, the second reflection phase angle is about −(180°−Δ2), a dimension of the reflection gap is directly proportional to a total predetermined phase angle Δ=Δ1+Δ2, and the total predetermined phase angle is between 0° ̃90°.
The antenna module of the embodiment provides return loss bandwidth of 23.59%, realized gain of 11.14 dBi and pure polarization. The antenna module of the embodiment is a wide bandwidth, high gain, and high cross polarization isolation antenna module.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
FIG. 1a shows a conventional antenna module;
FIG. 1b shows another conventional antenna module;
FIG. 2 shows an antenna module of the embodiment of the invention;
FIG. 3 shows the reflective pattern and the antenna of one embodiment of the invention;
FIG. 4a shows the return loss of the antenna module of the embodiment of the invention when compared to a simple Patch Antenna;
FIG. 4b shows the realized gain of the antenna module of the embodiment of the invention when compared to a simple Patch Antenna;
FIG. 4c shows the realized gain pattern on XZ plane of the antenna module when transmitting a wireless signal of 5.2 GHz;
FIG. 4d shows the realized gain pattern on YZ plane of the antenna module when transmitting a wireless signal of 5.2 GHz; and
FIG. 5 shows an antenna module of another embodiment of the invention.



DETAILED DESCRIPTION OF THE INVENTION
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
FIG. 2 shows an antenna module 100 of the embodiment of the invention, comprising a reflective superstrate 110, an antenna substrate 120, an antenna 130, a ground layer 140 and a reflective pattern 150. The reflective superstrate 110 is a partial reflective superstrate, comprising a first surface 111 and a second surface 112. The first surface 111 is opposite to the second surface 112. The antenna substrate 120 has a third surface 123 and a fourth surface 124. The third surface 123 is opposite to the fourth surface 124. The antenna 130 is disposed on the third surface 123. The ground layer 140 is disposed on the fourth surface 124. The reflective pattern 150 is formed on the first surface 111. The reflective pattern 150 is corresponding to the antenna 130. A reflection gap d is formed between the first surface 111 and the third surface 123. The reflective pattern 150 provides a first reflection phase angle Φ1, and the third surface provides a second reflection phase angle Φ2. The first reflection phase angle Φ1 comprises a first determined phase angle Δ1. The first determined phase angle Δ1 is not 0°. The first reflection phase angle Φ1 is about −(180°−Δ1). The second reflection phase angle Φ2 comprises a second determined phase angle Δ2. The second reflection phase angle Φ2 is about −(180°−Δ2). A dimension of the reflection gap is directly proportional to a total predetermined phase angle Δ=Δ1+Δ2, and the total predetermined phase angle is between 0° ̃90°.
The embodiment designs the first determined phase angle Δ1 by modifying the reflective pattern 150. The second determined phase angle Δ2 can be designed by choosing material (dielectric coefficient) and thickness of the antenna substrate 120. According to the Formulas (B1) and (B2):




  
    
      
        
          
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Therefore, the dimension of the reflection gap d is directly proportional to the total predetermined phase angle Δ=Δ1+Δ2. The total predetermined phase angle Δ is designed by modifying the first determined phase angle Δ1 (reflective pattern) and the second determined phase angle Δ2 (antenna substrate). The reflection gap d can be minimized by modifying the total predetermined phase angle Δ, and the volume of the antenna module 100 is decreased.

The material of the reflective superstrate 110 and the antenna substrate 120 can be dielectric material. The reflection gap d can be an empty space (filled by air), or filled by dielectric material.
In one embodiment of the invention, the total predetermined phase angle Δ is not 0°. The total predetermined phase angle is between 0° ̃90°, is preferred between 0° ̃60°, and is further preferred between 0° ̃20°.
FIG. 3 shows the reflective pattern 150 and the antenna 130 of one embodiment of the invention. The reflective pattern 150 comprises a plurality of reflective units 151. Each reflective unit 151 comprises a major axis x and a minor axis y. The reflective units 151 are equidistantly arranged along a first direction Y, and the minor axes y of the reflective units 151 are parallel to the first direction Y. In this embodiment, the reflective units are rectangular, and the reflective units are arranged into a 4×1 matrix. A unit gap g is formed between contiguous reflective units. The total predetermined phase angle Δ is about ±20°, a length P1 of the reflective unit 151 is 50 mm, a width Pw of the reflective unit 151 is 11.975 mm, the unit gap g is 0.7 mm, a width ex of the antenna 130 is 8.5 mm, a length ey of the antenna 130 is 14.54 mm, and the reflection gap d is 1 mm.
In the embodiment above, the first determined phase angle Δ1 can be designed by modifying the length P1 of the reflective unit, the width Pw of the reflective unit, and the unit gap g.
In the embodiment, the antenna 130 is a Patch Antenna, providing a wireless signal 2, wherein the wireless signal comprises a major polarization direction and a cross polarization direction, and the first direction Y is parallel to the major polarization direction.
In the embodiment, the antenna is a Patch Antenna, but the invention is not limited thereto. The antenna can also be a slot antenna or other antenna design.
FIG. 4a shows the return loss of the antenna module 100 of the embodiment of the invention when compared to a simple Patch Antenna. As shown in FIG. 4a, the antenna module 100 of the embodiment of the invention has greater bandwidth.
FIG. 4b shows the realized gain of the antenna module 100 of the embodiment of the invention when compared to a simple Patch Antenna. As shown in FIG. 4b, the antenna module 100 of the embodiment of the invention has increased realized gain.
FIG. 4c shows the realized gain pattern on XZ plane of the antenna module 100 when transmitting a wireless signal of 5.2 GHz. FIG. 4d shows the realized gain pattern on YZ plane of the antenna module 100 when transmitting a wireless signal of 5.2 GHz. As shown in FIGS. 4c and 4d, the antenna module 100 of the embodiment provides improved directivity and cross polarization isolation.
The antenna module of the embodiment provides return loss bandwidth of 23.59%, realized gain of 11.14 dBi and pure polarization. The antenna module of the embodiment is a high bandwidth, high gain, and high cross polarization isolation antenna module.
FIG. 5 shows an antenna module 200 of another embodiment of the invention, wherein the reflective pattern 250 comprises a plurality of reflective units 251. The reflective units 251 are square, and equidistantly arranged into a phalanx. In this embodiment, the antenna 230 is a Patch Antenna.
The reflective pattern mentioned above is an Electromagnetic Band Gap pattern. The reflective pattern can be modified.
In the embodiment of the invention, the dimension of the reflection gap can be first determined, then the total predetermined phase angle Δ is achieved according to the dimension of the reflection gap. Then, the reflective pattern and the antenna substrate are designed accordingly. Or, the total predetermined phase angle Δ is first determined, then the dimension of the reflection gap is achieved according to the total predetermined phase angle Δ. Then, the reflective pattern and the antenna substrate are designed accordingly.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

## Claims

1. An antenna module, comprising:
a reflective superstrate, comprising a first surface and a second surface, wherein the first surface is opposite to the second surface;
an antenna substrate, comprising a third surface and a fourth surface, wherein the third surface is opposite to the fourth surface;
an antenna, disposed on the third surface; and
a reflective pattern, formed on the first surface and facing the antenna, wherein a reflection gap is formed between the first surface and the third surface, the reflective pattern provides a first reflection phase angle, the third surface provides a second reflection phase angle, the first reflection phase angle comprises a first determined phase angle Δ1, the first determined phase angle Δ1 is not 0°, the first reflection phase angle is about −(180°−Δ1), the second reflection phase angle comprises a second determined phase angle Δ2, the second reflection phase angle is about −(180°−Δ2), a dimension of the reflection gap is directly proportional to a total predetermined phase angle Δ=Δ1+Δ2, and the total predetermined phase angle is between 0° ̃90°, wherein the reflective pattern comprises a plurality of reflective units, each reflective unit comprises a major axis and a minor axis, the reflective units are equidistantly arranged along a first direction, and the minor axes of the reflective units are parallel to the first direction, wherein the reflective units are arranged into a 4×1 matrix.

2. The antenna module as claimed in claim 1, wherein the total predetermined phase angle is between 0° ̃60°.

3. The antenna module as claimed in claim 1, wherein the total predetermined phase angle is between 0° ̃20°.

4. The antenna module as claimed in claim 1, wherein the reflective units are rectangular.

5. The antenna module as claimed in claim 1, wherein a unit gap is formed between contiguous reflective units.

6. The antenna module as claimed in claim 1, wherein the antenna provides a wireless signal, and the wireless signal comprises a major polarization direction and a cross polarization direction, and the first direction is parallel to the major polarization direction.

7. The antenna module as claimed in claim 1, further comprising a ground layer, disposed on the fourth surface.

8. The antenna module as claimed in claim 1, wherein a dielectric material is filled in the reflective gap.