Printed antenna and a wireless network device having the antenna

A printed antenna suitable for wireless networking device comprising a base plate, a grounding member, a first antenna, a second antenna and a third antenna is disclosed. The base plate is made of dielectric material where on a surface of which a first direction and a second direction perpendicular to each other are defined. The grounding member is electrically grounded and covers at least a partial area of the base plate surface. The first antenna is a dipole antenna extending from the grounding member generally towards the first direction. The second antenna is a monopole antenna extending from the grounding member generally towards the second direction. The third antenna is a monopole antenna extending from the grounding member generally towards the second direction. The second antenna and the third antenna are substantially disposed on the two opposing sides of first antenna.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a kind of printed antenna, more particularly a printed antenna suitable for MIMO wireless networking device and a wireless networking device having the same.

2. Description of the Prior Art

FIG. 1depicts the perspective view of a typical wireless networking device10, comprising a body11, internal circuitry12disposed inside the body, a connecting member13disposed at one end of body11to connect an external host (not shown in the figure), and an antenna signal transceiver14arranged on the other end of body11and corresponding to the connecting member13. Generally, the shell of antenna signal transceiver14is made of non-metallic material. When the wireless networking device10is connected to an external host, the antenna signal transceiver14must be exposed outside the external host for effective receiving and transmission of wireless signals. Based on the practice of regular users, the X-Y plane as shown inFIG. 1should be the plane with better wireless signal transmission. Thus the design of antenna for wireless networking device10focuses primarily on how to improve the isolation between antennas mounted in X-Y direction and reduce the dead space in the radiation pattern of antenna so as to enhance the receiving and transmitting ability of antenna on X-Y plane.

FIG. 2depicts the diagram of a conventional internal circuitry20in a MIMO wireless networking device. The conventional internal circuitry20comprises a base plate21, a control circuit disposed on the base plate21, a grounding member23covering a predefined area of base plate21, and an antenna unit24electrically connected to the control circuit22.

Antenna design that complies with the MIMO spec wireless networking device uses three antennas to form a three transmitter/two receiver antenna unit. For example, in the conventional MIMO antenna unit24as shown inFIG. 2, it includes a first antenna241configured in the middle, and a second antenna242and a third antenna243disposed respectively on each side of first antenna241. The three antennas241,242,243are monopole antennas adjacent to each other and facing the same direction (i.e. in X direction on the right side ofFIG. 2). The three antennas241,242,243respectively pass (cross) through grounding member23to connect to control circuit22via a first, a second and a third feedline251,252,253and are driven and controlled by the control circuit22. A major drawback in this kind of conventional MIMO antenna unit24is that its three monopole antennas241,242,243are arranged next to each other and extend in the same direction, resulting in inadequate isolation between adjacent antennas (e.g. between first antenna241and second antenna242). In addition, the design of using monopole for first antenna241results in bigger dead space in the radiation pattern on the X-Y plane.FIG. 3shows the radiation pattern measured from the X-Y plane of first antenna241used by the conventional MIMO antenna unit24as depicted inFIG. 2. As shown, the maximum horizontal gain of conventional first antenna241is merely −0.79 dBi, meaning there is practically no gain.FIG. 4illustrates the isolation graph measured between first antenna241and second antenna242in the conventional MIMO antenna unit24as shown inFIG. 2. Based on the graph, the isolation between conventional first antenna241and second antenna242in the operating frequency range of 2.4 GHz and 2.5 GHz is approximately −6.01 dB, which is still higher than the −10 dB or under requirement in the market for high-performance antenna and leaves room for further improvement.

SUMMARY OF INVENTION

The first object of the present invention is to provide a printed antenna with better radiation pattern to improve gain and reduce dead space and having better antenna-to-antenna isolation to avoid interference and enhance antenna performance.

The second object of the present invention is to provide a printed antenna which uses a dipole antenna coupled with a monopole antenna on each side to form a three transmission/two receiver antenna configuration for use in MIMO wireless networking device.

The third object of the present invention is to provide a printed antenna for MIMO wireless networking device which includes three antennas with two adjacent antennas extending in approximately vertical arrangement to improve the antenna-to-antenna isolation.

The fourth object of the present invention is to provide a wireless networking device having a printed antenna of the invention.

To achieve the aforesaid objects, the printed antenna of the present invention changes its middle antenna in the three-antenna configuration of the MIMO antenna unit to a T-dipole antenna and arranges the two monopole antennas on each side of the T-dipole in a direction generally vertical to the T-dipole. Such arrangement is different from the conventional three-antenna system where all three antennas are adjacent to each other and face the same direction. As such, in the printed antenna of the invention, the T-dipole antenna which itself is a radiator and the grounding member configured between the T-dipole and the monopole antenna helps enhance the isolation between two adjacent antennas. In addition, the design of a T-dipole antenna coupled with a monopole antenna on each side extending in different direction can produce better radiation pattern on X-Y plane and higher gain, hence greatly improving the antenna performance.

DETAILED DESCRIPTION

FIGS. 5˜7disclose a preferred embodiment of the printed antenna60and a wireless networking device50having printed antenna60according to the invention.FIG. 5andFIG. 6show respectively the component side and the solder side of the internal circuitry of the wireless networking device50having a printed antenna60according to the invention.FIG. 7is a magnified view of the printed antenna60in the wireless networking device shown inFIG. 5andFIG. 6.

As shown inFIG. 5, the wireless networking device50having a printed antenna60according to a preferred embodiment of the invention comprises: a base plate51, a control circuit52, a grounding member53and a printed antenna60.

The base plate51is made of dielectric material in the shape of a generally flat rectangle. In a preferred embodiment, the base plate51is a FR4 circuit board. The base plate51has a component side surface disposed with a plurality of electronic circuits (called first surface511or top surface below) and a solder side surface disposed with a plurality of solder points (called second surface512or bottom surface below as shown inFIG. 6). The first surface511of base plate51is defined with a first direction (X direction) and a second direction (Y direction) perpendicular to each other, and the base plate51has a first edge513generally perpendicular to the first direction, and a second edge514and a third edge515generally perpendicular to the second direction. The second edge514and the third edge515are respectively connected to each end of first edge513.

The control circuit52is generally provided on the first surface511of base plate51and comprises a plurality of IC components and a plurality of electronic components to provide the function of wireless network transmission. The control circuit52can be implemented using prior art.

The grounding member53is electrically grounded (GND) and covers at least partial area on the first surface511and the second surface512of base plate51, in particular the area on first surface511adjacent to the printed antenna60and extensively a major part of second surface512other than the part opposing the printed antenna60. The grounding member513also provides the function of resonance with printed antenna60in addition to grounding. In a preferred embodiment, the grounding member53is a first space (not numbered) apart from the first edge513in the first direction (X direction), a second space (not numbered) apart from the second edge514in the second direction (Y direction), and a third space (not numbered) apart from the third edge515in the second direction (Y direction). In the area adjoining printed antenna60, the areas on first surface511and second surface512covered by the grounding member53generally correspond to each other and have the same contour.

The printed antenna60is arranged on base plate51at a place uncovered by grounding member53. The printed antenna60connects to control circuit52by means of a plurality of feedlines541,542,543so as to provide the function of wireless signal receiving/transmission. In a preferred embodiment, the printed antenna further comprises: a first antenna61, a second antenna62, and a third antenna63. The first antenna61extends from a front edge531of grounding member53generally towards the first edge513and is positioned exactly in the first space. The second antenna62extends from a first side edge532of grounding member53generally towards the second edge514and is positioned exactly in the second space. The third antenna63extends from a second side edge533of grounding member53generally towards the third edge515and is positioned exactly in the third space. The grounding member53on the first surface511also comes with a first rear edge534extending from the end of first side edge532to the second edge514, and a second rear edge535extending from the end of second side edge533to the third side edge515. As shown inFIG. 5, the edges531˜535of grounding member53constitute substantially a ladder-shaped structure. On each side of the front edge531of grounding member53, there forms an ungrounded square area defined respectively by the first side edge532and the first rear edge534, and the second side edge533and the second rear edge535. The second antenna62and the third antenna63are exactly and respectively positioned in the ungrounded area defined by the first side edge532and the first rear edge534, and in the ungrounded area defined the second side edge533and the second rear edge535. As such, the second antenna62and the third antenna63are substantially isolated from each other by the grounding member53, and the grounding member52also provides isolation between the first antenna61and the second antenna62(or the third antenna3) to some extent.

As shown inFIGS. 5 & 6, first antenna61is a T-dipole antenna which further comprises: a T-shaped radiating element611and a microstrip line612. The T-shaped radiating element611is configured on the second surface512of base plate51and comprises: a body613, a long narrow slot614, and two extension members615,616. The body613extends from grounding member53along the first direction to a place adjacent to first edge513. The long narrow slot614is formed in the middle of body613and extends a predetermined length from the end of first edge513nearer the body613along the first direction towards the grounding member53. The two extension members615,616respectively extend a predetermined length from the left and right side of body613at the end nearer first edge513in a direction generally parallel to the second direction. The body613of T-shaped radiating element611is connected to the grounding member53on second surface512. In an area on the first surface511adjoining the vicinity of microstrip line612, another body613aopposing and having the same contour as body613on second surface512is disposed. This another body613ais connected to the grounding member53situated on first surface511.

The microstrip line612is positioned on the first surface511of base plate51and adjoins the long narrow slot614. The microstrip line612comprises: a first long narrow member617, a bend member618, and a second long narrow member619. The first long narrow member617extends from the grounding member53in a direction roughly parallel to the direction of long narrow slot614to a place near the first edge513. One end of the bend member618is connected to one end of the first long narrow member617and extends along the second direction to cross over the long narrow slot614. One end of the second long narrow member619is connected to the other end of bend member618and extends in a direction roughly parallel to the long narrow slot614towards the grounding member53. The body613and the extension members615,616at its end that extend towards the sides visually constitute a T-shape. The microstrip line612and T-shaped radiating element611combined together possess the properties of a dipole antenna, thus called T-dipole antenna.

Again referring toFIG. 5, in this preferred embodiment, the second antenna62and the third antenna63are disposed on two opposing sides of first antenna61in a substantially symmetrical manner, and the shapes of the second antenna62and the third antenna63substantially correspond to each other. Thus only the structure of the second antenna62is described below without reiterating the configuration of the third antenna63.

In a preferred embodiment, the second antenna62comprises: an end-section member621, a first bend section622, a second bend section623, a third bend section624, and a fourth bend section624. One end of the end-section member621adjoins the first side edge532of grounding member53and protrudes a small length towards the second direction. One end of the first bend section622is connected to the other end of said end-section member621and extends a first length roughly along the first direction away from the first edge513. One end of the second bend section623is connected to the other end of first bend section622and extends a second length roughly along the second direction towards the second edge514. One end of the third bend section624is connected to the other end of second bend section623and extends a third length roughly along the first direction towards the first edge513. One end of the fourth bend section625is connected to the other end of third bend section624and extends a fourth length roughly along the second direction away from the second edge514. As shown inFIG. 5, the first to fourth bend sections622˜625of second antenna62roughly constitute a D-shaped antenna structure. The space between the first and the second bend sections622,623of the second antenna62and the first side edge532and the first rear edge534of the grounding member53substantially forms a resonance surface of second antenna62. The D-shaped area configured between the third and the fourth bend sections624,625and the first and the second bend sections622,623substantially forms a resonance chamber of second antenna62to provide good antenna performance.

As shown inFIG. 7, the printed antenna60can change its operating frequency bandwidth or range by adjusting the length or bend at different parts of antennas61,62,63. For example, changing the extension length of the long narrow slot614of first antenna61can decide the width of the operating frequency range of first antenna61. Also, adjusting the length of first long narrow member617and second long narrow member619of the microstrip line612of first antenna61can change the operating frequency range of first antenna61. Also, adjusting the length of the first bend-section622and second bend-section623of second antenna62(or third antenna63) can decide the width of operating frequency range of second antenna62(or third antenna63). Changing the length and location of the third bend-section624can adjust its operating frequency range.

In the example of wireless networking device50for WLAN that complies with IEEE802.11g, the operating frequency range of its printed antenna60must be in the range of 2.4 GHz˜2.5 GHz. In a preferred embodiment, the lengths and relative positions of antennas61,62,63of the printed antenna60can be designed in the following manner:

1. The length of the two extension members615,616of the T-shaped radiating element611of first antenna61(measured from the end of long narrow slot614) is respectively ¼ wavelength of the operating frequency range of first antenna61, and the shapes of the two extension members615,616are symmetrical to each other.

2. The total length of the long narrow slot614of the T-shaped radiating element611of first antenna61is approximately ¼ wavelength of the operating frequency range of first antenna61.

3. The first and the second long narrow members617,619of the microstrip line612of first antenna61are respectively 50 ohm microstrips and their length is respectively ¼ wavelength of the operating frequency range of first antenna61, while the bend member618is relatively shorter. Thus substantially the total length of microstrip line612is equal to ½ wavelength of the operating frequency range of first antenna61.

4. The point at where feedline542,543is connected to second antenna62and third antenna63respectively is called the feedpoint of the second antenna62and the third antenna63. The feedpoint of first antenna61is located at where its bend member618crosses over the long narrow slot614. As such, the distance between the feedpoint of first antenna61and that of second antenna62is approximately ¼ wavelength of the operating frequency range of first antenna61.

5. In the second antenna62, the combined length of first bend section622and second bend section623is approximately ⅛ wavelength of the operating frequency range of second antenna62, and the combined length of the third bend section624and fourth bend section625is also approximately ⅛ wavelength of the operating frequency range of second antenna62.

In a preferred embodiment, the plurality of feedlines541,542,543are 50 ohm microstrips to provide better power shift function.

As shown inFIGS. 5˜7, the unique design of printed antenna60of the invention enable the second antenna62and the third antenna63to be isolated from each other by grounding member53. In addition, the radiating element611of the first antenna61(T-dipole antenna) and the grounding member53situated between the first antenna61and second antenna62will enhance the isolation between two antennas61,62. Also, the design of T-dipole antenna (first antenna61) coupled with two monopole antennas (second antenna62and third antenna63) on each side extending in different directions also produces better radiation pattern and higher gain on X-Y plane, thereby greatly enhancing the antenna performance.

Referring toFIG. 8andFIG. 9,FIG. 8shows the radiation pattern measured from the X-Y plane of the first antenna61in the printed antenna60of the invention as shown inFIG. 5andFIG. 6.FIG. 9shows the isolation graph measured between the first antenna61and the second antenna62of the printed antenna60as shown inFIG. 5andFIG. 6.

It is seen from the radiation pattern inFIG. 8that the horizontal gain of first antenna61of printed antenna60reaches 3.59 dBi, which is much higher than the gain of −0.79 dBi from prior art as shown inFIG. 2. It is conceivable that printed antenna60of the invention provides better wireless signal communication quality and transmission efficiency than prior art. Also as seen from the isolation graph inFIG. 9, in the operating frequency range of 2.4 GHz˜2.5 GHz, the isolation between the first antenna61and second antenna62of the printed antenna60can be as low as −13.42 dB. Such isolation value is not only far superior to the −6.01 dB produced by prior art as shown inFIG. 2, it also surpasses the market requirement of −10 dB or under isolation for high-performance antenna. The present invention apparently greatly improves the antenna design and performance of prior art.