WO2015088321A1

WO2015088321A1 - A wideband antenna

Info

Publication number: WO2015088321A1
Application number: PCT/MY2014/000174
Authority: WO
Inventors: Hafizal MOHAMAD @ DIN; Mohd Haizal JAMALUDDIN; Nordin Ramli
Original assignee: Mimos Bhd
Current assignee: Mimos Bhd
Priority date: 2013-12-10
Filing date: 2014-06-12
Publication date: 2015-06-18
Anticipated expiration: 2016-06-10
Also published as: MY166707A

Abstract

Disclosed herein is a wideband antenna with multiple functions that can be used in white space devices. Generally, the wideband antenna comprises a U-shaped patch (103) having a meander structure (104) to enable the wideband antenna to operate in high frequency covering the UHF Band IV and Band V, or any other frequencies with high impedance bandwidth; and a dielectric resonator (106) to enable the wideband antenna to support high data rate applications.

Description

A WIDEBAND ANTENNA

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to a wideband antenna, and more particularly to a wideband antenna with multiple functions.

BACKGROUND OF THE INVENTION

Cognitive radio is useful for improving efficiency in spectrum utilization, whereby it can detect and allocate any unutilized spectrum, also known as white space, in an opportunistic manner while ensuring no interference. In 2008, the FCC has adopted rules to allow unlicensed use of television white space (TVWS). This is an important development to promote innovations within the UHF bands and to provide long distance broadband access to hard-to-reach population in typical rural area.

Recently, TVWS has generated much attention in cognitive radio applications due to worldwide digital transition of television broadcasting band. In other words, there is now abundant of white space that is readily to and can be used, especially in the UHF region.

White space device normally operates in UHF Band IV and Band V, i.e. high frequency range in between 470 MHz and 798 MHz. Therefore, the antenna within the white space device is required to be small in size and at the same time supports high bandwidth. These requirements are difficult to be implemented due to the respective large wavelength of 400 mm to 640 mm, resulting in an antenna with very large dimension. Further, TVWS applications require high data rate transmission, and therefore the white space device has to be equipped with more than one antenna. However, the problematic part is that most of the wireless terminal user equipment is small in size and has limited space for attachment of more than one antenna. Even if there is enough space to accommodate more than one antenna, there is always insufficient space to make sure that there is an adequate separation between those antennas. Therefore, it has become an objective of the present invention to overcome the above-identified disadvantages by introducing a multi-functional wideband antenna that operates in high frequency range with high impedance bandwidth, and supports high data rate applications, said wideband antenna is relatively compact and small in comparison with a conventional two monopole multiple- input and multiple-output (MIMO) antenna.

SUMMARY OF THE INVENTION

The core technical aspect of the present invention relates to a wideband antenna with multiple functions that can be used in white space devices.

According to an embodiment of the present invention, the wideband antenna comprises a planar substrate; a partial ground plane attached to a back surface of the planar substrate; a U-shaped patch having a meander structure printed on a front surface of the planar substrate; at least one first feed line connected to the U-shaped patch; a dielectric resonator attached to the front surface of the planar substrate; and at least one second feed line connected to the dielectric resonator. According to a preferred embodiment of the present invention, the meander structure is located at a bottom part of the U-shaped patch.

According to another preferred embodiment of the present invention, the meander structure comprises a slot, wherein the slot has a width of 1 mm.

According to a further preferred embodiment of the present invention, the meander structure comprises at least one line resulting in two slots, wherein the line has a width of 1.5 mm, and each slot has a width of 1 mm. According to still another preferred embodiment of the present invention the meander structure comprises twenty lines resulting in twenty one slots, wherein each line has a width of 1.5 mm, and each slot has a width of 1 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates the front view of the wideband antenna of the present invention;

Figure 2 illustrates the side view of the wideband antenna of the present invention;

Figure 3 illustrates the back view of the wideband antenna of the present invention;

Figure 4 illustrates the meander structure of the U-shaped patch having twenty lines resulting in twenty one slots, as the exemplary; Figure 5 is a chart showing the reflection coefficient of the wideband antenna of the present invention, wherein the wideband antenna comprises a U-shaped patch having a meander structure with twenty lines resulting in twenty one slots;

Figure 6 is a chart showing the radiation pattern of the wideband antenna of the present invention measured at 500 MHz, wherein the wideband antenna comprises a U-shaped patch having a meander structure with twenty lines resulting in twenty one slots;

Figure 7 is a chart showing the reflection coefficient of the wideband antenna of the present invention, wherein the wideband antenna comprises a U-shaped patch having a meander structure with different numbers of slots; Figure 8 is a chart showing the reflection coefficient of the wideband antenna of the present invention, wherein the wideband antenna comprises a U-shaped patch having a meander structure with different slot widths; and Figure 9 is a chart showing the reflection coefficient of the wideband antenna of the present invention, wherein the wideband antenna comprises a U-shaped patch having a meander structure with different line widths.

DETAILED DESCRIPTION OF THE INVENTION

The above mentioned and other features and objects of this invention will become more apparent and better understood by reference to the following detailed description. It should be understood that the detailed description made known below is not intended to be exhaustive or limit the invention to the precise disclosed form as the invention may assume various alternative forms. On the contrary, the detailed description covers all the relevant modifications and alterations made to the present invention, unless the claims expressly state otherwise. The fundamental technical aspect of the present invention relates to a wideband antenna that can be utilized in white space devices. Ideally, an antenna for white space devices has to be multi-functional, i.e. operate in high frequency with high impedance bandwidth, and to support high data rate applications. In order to achieve these objectives, in general, the wideband antenna of the present invention comprises a U-shaped patch (103) having a meander structure (104) to enable the wideband antenna to operate in high frequency covering the UHF Band IV and Band V (i.e. 470 MHz to 798 MHz), or any other frequencies with high impedance bandwidth; and a dielectric resonator (106) to enable the wideband antenna to support high data rate applications.

The size of the wideband antenna of the present invention is relatively small and compact. For example, when compared to a typical two monopole multiple-input and multiple-output (Ml MO) antenna with a λ/2 separation distance at 470 MHz, the wideband antenna of the present invention is 84% smaller.

Figure 1 , Figure 2, Figure 3, and Figure 4 are now being referred.

Specifically, the wideband antenna comprises a planar substrate (101); a partial ground plane (102) attached to a back surface of the planar substrate (101); a U- shaped patch (103) having a meander structure (104) printed on a front surface of the planar substrate (101); at least one first feed line (105) connected to the U-shaped patch (104); a dielectric resonator (106) attached to the front surface of the planar substrate (101); and at least one second feed line (107) connected to the dielectric resonator (106).

An example of a planar substrate (101) that can be used in the present invention is a FR-4 board.

An example of a partial ground plane (102) that can be used in the present invention is a partial metal ground plane. Basically, it is used for the purpose of grounding mechanism.

The specific design of the U-shaped patch (103) allows the wideband antenna to operate in high frequency covering the UHF Band IV and Band V, or any other frequencies with high impedance bandwidth. Additionally, the U-shaped patch has a special characteristic that enhances this particular feature even more, which is the meander structure (104). It is also due to the meander structure that the drastic size reduction of the wideband antenna is made possible. Preferably, the meander structure (104) is located at a bottom part of the U-shaped patch (103), although it is possible to have the meander structure (104) to be located at any part of the U-shaped patch (103).

The U-shaped patch (103) is fabricated firstly by printing an elliptical shaped patch onto the planar substrate (101). Thereafter, an inner part of the elliptical shaped patch is removed to form a O-shaped patch. Subsequently, a top part of the O-shaped patch is removed to form the U-shaped patch (103).

Referring specifically to Figure 4, it can be seen that the meander structure (104) comprises a number of lines (104a) and a number of slots (104b).

The number of slots (104b) of the meander structure (104) plays an important role in determining how well the wideband antenna can operate in terms of impedance bandwidth. Therefore, a specific investigation has been carried out to examine the relationship between number of slots (104b) and impedance bandwidth, and the results are shown in Table 1 , and Figure 7.

Table 1 : The relationship between number of slots and impedance

bandwidth.

Referring now to Table 1 and Figure 7, they show that a small impedance bandwidth of 136 MHz is achieved for U-shaped patch (103) without any slot (104b), i.e. without the meander structure (104). However, when the number of slots (104b) is increased, the value of impedance bandwidth starts to increase as well. The slots (104b) act as a mechanism for matching purposes and at the same time they can enhance the impedance bandwidth of the wideband antenna. It is found that the optimum number of slots (104b) to enable the wideband antenna of the present invention to cover the UHF Band IV and Band V MHz band is twenty one slots (104b). It is further observed that the meander structure (104) with more than twenty three slots (104b) will cause the wideband antenna to operate in high impedance bandwidth with an additional notch. Conclusion is made in that the optimum number of slots (104b) is twenty one slots (104b).

The impedance bandwidth of the wideband antenna is further influenced by the slot (104b) width. A parametric study has been carried out to investigate this particular influence, and the results are shown in Figure 8. The study is carried out with the line (104a) width fixed at 2 mm. From the figure, it can be observed that when the slot (104b) width is increased, the resonant frequency of the wideband antenna is shifted to higher frequency. At the same time, a large impedance bandwidth is obtained for each of the experiments with slot (104b) width of 1 mm and 1.5 mm. Further increase in the slot (104b) width will reduce the impedance bandwidth. Conclusion is made in that the optimum slot (104b) width is 1 mm.

The impedance bandwidth of the wideband antenna is even further influenced by the line (104a) width. Another parametric study has been carried out to investigate this particular influence, and the results are shown in Figure 9. The study is carried out with the slot (104b) width fixed at 1 mm. From the figure, it can be observed that there is not much change on the reflection coefficient for each of the experiments with line (104a) width of 0.5 mm and 1 mm. However, a large impedance bandwidth is achieved for each of the experiments with line (104a) width of 1.5 mm and 2.0 mm. Conclusion is made in that the optimum line (104a) width is 1.5 mm.

In view of the above, the following three embodiments can be made: A first embodiment where the meander structure (104) may comprise a slot (104b), wherein the slot has a width of 1 mm. A second embodiment where the meander structure (104) may comprise at least one line (104a) resulting in two slots (104b), wherein the line has a width of 1.5 mm, and each slot has a width of 1 mm.

A third embodiment where the meander structure (104) may comprise twenty lines (104a) resulting in twenty one slots (104b), wherein each line has a width of 1.5 mm, and each slot has a width of 1 mm. It is determined that this particular embodiment causes the wideband antenna to operate at a frequency range of 459 MHz to 808 MHz with the highest impedance bandwidth of 349 MHz. It should be noted that the above-mentioned studies are simulated, and the above-mentioned frequency ranges and impedance bandwidths are experimental/simulated values. To ascertain the real values, the wideband antenna in accordance with the aforementioned third embodiment is built and tested, and the results are shown in Figure 5 and Figure 6. From Figure 5, the reflection coefficient curve has several resonance frequencies that are combined together to perform high impedance bandwidth. It can be observed that, at Sn < -10 dB, the wideband antenna operates in a frequency range of 325 MHz to 815 MHz with an impedance bandwidth of 490 MHz. We refer now to Figure 6. In order to observe the radiation pattern of the wideband antenna of the present invention, two planes, namely E-plane and H-plane, are selected. It can be observed that the antenna gain is 2.2 dBi with a nearly omnidirectional patter in H-plane, which remains constant at a specific frequency, in this case 500 MHz. It is proven that the wideband antenna radiates over the interested frequency, which is suitable for TVWS applications. The radiation patterns in co-polar of E- plane and H-plane indicate that a good pattern stability has been obtained. Overall, the testing results confirm that the wideband antenna of the third embodiment outperforms the simulated results. Referring back to Figure 1 , Figure 2, Figure 3, and Figure 4, the first feed line (105) allows the U-shaped patch (103) to be connected to a radio transmitter or receiver. Preferably, the first feed line (105) is located at a bottom part of the U- shaped patch (103), although it is possible to have the first feed line (105) to be located at any part of the U-shaped patch (103).

As mentioned previously, the dielectric resonator (106) of the present invention is attached to the front surface of the planar substrate (101), preferably to the center of the front surface of the planar substrate (101). It is also possible to have the dielectric resonator (106) to be attached to any unutilized space of the planar substrate (101). The dielectric resonator (106) has a cylindrical shape, although it is possible to have the dielectric resonator (106) in various kind of shape. The second feed line (107) allows the dielectric resonator (106) to be connected to a radio transmitter or receiver. Preferably, the second feed line (107) is located at the back surface of the planar substrate (101), and connected to the dielectric resonator (106) through the planar substrate (101). It is possible to supply the dielectric resonator (106) with more than one second feed line (107) to perform multi antenna capability by exploiting dielectric permittivity.

Claims

1) A wideband antenna with multiple functions that operates in high frequency with high impedance bandwidth, and supports high data rate applications, the wideband antenna comprises:

a) a planar substrate (101);

b) a partial ground plane (102) attached to a back surface of the planar substrate (101 );

c) a U-shaped patch (103) having a meander structure (104) printed on a front surface of the planar substrate (101);

d) at least one first feed line (105) connected to the U-shaped patch (104);

e) a dielectric resonator (106) attached to the front surface of the planar substrate (101); and

f) at least one second feed line (107) connected to the dielectric resonator (106).

2) A wideband antenna in accordance with claim 1 , wherein the meander structure (104) is located at a bottom part of the U-shaped patch (103).

3) A wideband antenna in accordance with claim 1 , wherein the meander structure (104) comprises a slot (104b).

4) A wideband antenna in accordance with claim 3, wherein the slot (104b) has a width of 1 mm.

5) A wideband antenna in accordance with claim 1 , wherein the meander structure (104) comprises at least one line (104a) resulting in two slots (104b).

6) A wideband antenna in accordance with claim 5, wherein the line (104a) has a width of 1.5 mm, and each slot (104b) has a width of 1 mm. 7) A wideband antenna in accordance with claim 1 , wherein the meander structure (104) comprises twenty lines (104a) resulting in twenty one slots (104b). 8) A wideband antenna in accordance with claim 7, wherein each line (104a) has a width of 1.5 mm, and each slot (104b) has a width of 1 mm.

9) A wideband antenna in accordance with claim 1 is used in white spaces devices.

10) A wideband antenna in accordance with claim 1 operates in a frequency range of 325 MHz to 815 MHz with impedance bandwidth of 490 MHz.