Multiband antenna

A multiband antenna used for a portable communication device includes a first antenna unit, a second antenna unit, a third antenna unit, and feed member. The first antenna unit, the second antenna unit and the third antenna unit are capable of receiving and/or sending wireless signals. The second antenna unit is connected to the first antenna unit, the third antenna unit is connected to the first antenna unit, and the feed member is electrically connected to the first antenna unit and the second antenna unit. The feed member receives wireless signals and transmits the wireless signals through the first antenna, the second antenna unit and the third antenna unit to generate corresponding current paths, and the first antenna unit is located between the second antenna unit and the third antenna unit to isolate the second antenna unit and the third antenna unit to avoid coupling interference of their resonant frequencies.

BACKGROUND

1. Technical Field

The disclosure generally relates to antennas, particularly to, to a multiband antenna for use in a portable communication device.

2. Description of the Related Art

Antennas are used in mobile phones, personal digital assistants (PDAs), and other portable communication device to receive and/or send wireless signals. Commonly, a portable communication device may receive and/or send wireless signals of different frequencies, which require its antenna to be a multiband antenna. Generally, the multiband antennas achieve multiband frequencies by the coupling effect and the parasitic effect.

However, many multiband antennas have complicated structures and are large in size, making it difficult to miniaturize the portable communication devices. Moreover, coupling effects among different current paths may affect their own operating frequencies of each current path. Therefore, it is difficult for the multiband antenna to have independent and non-interfering resonant frequencies. It can also be difficult to adjust the bandwidths of the independent operating frequencies.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

FIGS. 1 and 2schematically show an exemplary embodiment of a multiband antenna10for use in a portable communication device, such as a mobile phone or a PDA for receiving and/or sending wireless signals.

The multiband antenna10is made of conductive materials, such as copper or other metals. The multiband antenna10includes a first antenna unit11, a second antenna unit13, a third antenna unit15, and a feed member17, all of which can be substantially flat sheets. The first antenna unit11is connected to the second antenna unit13, the third antenna15, and the feed member17cooperatively. The first antenna unit11, the second antenna unit13and the feed member17are coplanar, and the third antenna unit15is substantially perpendicularly connected to the first antenna unit11, namely, the third antenna unit15is substantially perpendicular to the plane of the first antenna unit11.

The first antenna unit11includes a first radiating member111, a second radiating member112, a third radiating member113, a fourth radiating member114, a fifth radiating member115, and a connection member116, which are substantially flat strip sheets. The second radiating member112is connected to an end of the first radiating member111, forming an angle less than 90° with the first radiating member111. An end of the third radiating member113is connected to the second radiating member112opposite to the end connected to the first radiating member111. The other end of the third radiating member113is substantially perpendicularly connected to the fourth radiating member114. The second radiating member112and the fourth radiating member114are located on the same side of the third radiating member113.

The third radiating member113is substantially parallel to the fifth radiating member115and an end of the fifth radiating member115is substantially perpendicularly connected to the fourth radiating member114. The fifth radiating member115and the first radiating member111are aligned with each other and are spaced from each other. Thus, the first radiating member111and the fifth radiating member115are on substantially the same extended line. The connection member116is adjacent to the second radiating member112and is connected between the third radiating member113and the third antenna unit15. The third radiating member113and the fifth radiating member115are respectively connected to opposite sides of the fourth radiating member114to cooperatively define a slot117.

The second antenna unit13includes a first sheet body131connected to a second sheet body132. The first sheet body131and the second sheet body132are substantially flat strip sheets. The width of the first sheet body131is slight larger than the width of the first radiating member111. The first sheet body131is connected to the distal end of the first radiating member111and is spaced from the fifth radiating member115. The first sheet body131is substantially parallel to the third radiating member113and is aligned with the fifth radiating member115. The outer edge (namely, the lateral side away from the third radiating member113) of the first sheet body131is respectively aligned with the outer edge of the first radiating member111and the fifth radiating member115.

The second sheet body132is partially connected to the inner edge (namely, the lateral side facing toward the third radiating member113) of the first sheet body131and is substantially parallel to the third radiating member113. The second sheet body132is aligned with the fourth radiating member114and is partially received in the slot117.

The third antenna unit15is substantially a flat sheet and has an end substantially perpendicularly connected to the connection member116. The remaining part of the third antenna unit15is spaced from the third radiating member113. Two long sides of the third antenna unit15are substantially parallel to the third radiating member113. The length of the third antenna15is less than the length of the third radiating member113.

The feed member17is a substantially “L” shaped flat sheet and includes a connecting arm171and a feed arm173. The first radiating member111and the feed arm173are substantially perpendicularly connected to the opposite ends of the connecting arm171, respectively, and the connecting arm171is substantially adjacent to the first sheet body131. The feed arm173is a substantially strip flat sheet and is substantially parallel to the first radiating member111. In this exemplary embodiment, the opposite the ends of the feed arm173can be respectively defined as a signal feeding end and a grounding end. The signal feeding end is connected to the connecting arm171and is electrically connected to a corresponding signal transmitting portion on a circuit board (not shown) for receiving and/or sending wireless signals. The grounding end opposite the signal feeding end is electrically connected to ground portion on the circuit board.

In communication, the signal feeding end of the feed arm173receives the wireless signals and transmits the wireless signals through the first antenna unit11, the second antenna unit13, and the third antenna unit15to generate corresponding current paths, resulting in different resonant frequencies. In use, the resonant frequency range of the first antenna unit11is about 824 MHz-894 MHz, and used to receive and/or send global system for mobile communication (GSM) wireless signals. The resonant frequency range of the second antenna unit13is about 1850 MHz-1990 MHz, and used to receive and/or send personal communication services (PCS) wireless signals. The resonant frequency range of the third antenna unit15is about 1570 MHz-1580 MHz, and used to receive and/or send global positioning system (GPS) wireless signals. One skilled in the art would know how to size the various antennas to create these resonant frequency ranges.

Further referring toFIGS. 1 and 2, the first antenna unit11is located between the second antenna unit13and the third antenna unit15, and the first antenna unit11forms a low frequency radiating area, the second antenna unit13and the third antenna15respectively form a high frequency radiating area. Thereby, in actual use, the low frequency radiating area is formed between the two high frequency radiating areas and is capable of isolating the two high frequency radiating areas to avoid mutual coupling between high frequencies of the second antenna unit13and the third antenna15. Thus, the first antenna unit11, the second antenna unit13and the third antenna15respectively have an independent and non-interfering resonant frequencies, and are capable of adjusting the bandwidths of the independent operating frequencies.

FIG. 3shows an exemplary test diagram when the multiband antenna10is used in the slide-type mobile phone, disclosing return loss (RL) varying with frequency. The horizontal axis of the test diagram is expressed as the frequency, and the vertical axis of the test diagram is expressed as the return loss. Among them, curve1represents the return loss curve of the multiband antenna10when the slide-type mobile phone is in a closed state, and curve2represents the return loss curve of the multiband antenna10when the slide-type mobile phone is in an open state.

In this exemplary embodiment, during testing, all the return losses are less than −6 decibels (dBs) in the frequency band 824 MHz-894 MHz and the frequency band 1850 MHz-1990 MHz, which has better radiating efficiency. In actual use, the resonance point A of the GPS frequency band 1570 MHz-1580 MHz may shift to the low frequency band, so the multiband antenna10also has better radiating efficiency between 1570 MHz-1580 MHz of the GPS frequency band.

In summary, in the multiband antenna10of the exemplary embodiment. The first antenna unit11of the multiband antenna10is positioned between the second antenna unit13and the third antenna unit15to isolate the second antenna unit13and the third antenna15, avoiding mutual coupling between high frequencies of the second antenna unit13and the third antenna unit15. Thus, the first antenna unit11, the second antenna unit13and the third antenna unit15respectively have their own independent and non-interfering operating frequencies such that the bandwidths of the multiband antenna10can be adjusted independently. Moreover, the multiband antenna10has simple design structure, and its different operating frequencies also do not couple with each other, thus, the multiband antenna10can be applied to different kinds of wireless communication systems/devices.