Patent Application
20140320358
This Application claims priority of Taiwan Patent Application No. 102114536 filed on Apr. 24, 2013, the entirety of which is incorporated by reference herein.
1. Field of the Invention
The disclosure generally relates to a communication device, and more particularly, relates to a mobile communication device comprising a switchable dual-feed antenna element.
2. Description of the Related Art
With fast development in the wireless communication industry nowadays, the use of communication devices for human beings is not merely limited to talking. Instead, the users demand communication devices to have more and more functions. To satisfy the users' requirements and to maintain the thin and small appearance of a communication device, efficient utilization of the limited space inside the communication device is very important.
It is a critical challenge for antenna designers to design an antenna element configured to cover multiple bands with smaller available space in a communication device.
The invention is aimed to provide a communication device and a switchable dual-feed antenna element therein. The communication device at least comprises an antenna element and a ground element. A ground plane antenna with an asymmetrical dipole antenna structure is formed by the antenna element and the ground element. The antenna element has two different feeding points. On the condition that the antenna size is unchanged, the antenna element is selectively coupled to different matching circuits to operate in a plurality of communication bands comprising high bands and low bands by controlling closed and open states of a switch circuit. Accordingly, the invention can achieve multi-band operations of a compact antenna element.
In a preferred embodiment, the invention provides a communication device, comprising: a ground element, wherein an edge of the ground element has a notch; and an antenna element, comprising a metal element, wherein the metal element is disposed inside the notch, and the metal element has a first end and a second end. The first end and the second end are spaced away from each other and are respectively positioned adjacent to two ends of a diagonal line of the notch. The first end of the metal element is used as a first feeding point of the antenna element, and the second end of the metal element is used as a second feeding point of the antenna element, wherein the first feeding point is coupled through a switch and a first matching circuit to a first signal source, and the second feeding point is coupled through an inductive element and a second matching circuit to a second signal source.
In some embodiments, the antenna element may operate as follows. When the antenna element is fed from the second feeding point, the switch coupled to the first feeding point is switched to be open. Accordingly, the antenna element is not affected by the first feeding point, and generates a second resonant mode in a second band (lower band). On the other hand, when the antenna element is fed from the first feeding point, the switch coupled to the first feeding point is switched to be closed. The first signal source feeds the antenna element through the first feeding point, and the antenna element generates a first resonant mode in a first band (higher band). Note that the second feeding point is not coupled to another switch to prevent the second feeding point from affecting the first resonant mode in the first band. Instead, the second feeding point is coupled to an inductive element. Since the inductive element provides high impedance in a high band, the inductive element can effectively solve the problem of the resonant currents flowing to the second feeding point when the first resonant mode in the first band is excited. Accordingly, the first feeding point and the second feeding point do not interfere with each other in the first band. That is, the function of an inductive element is similar to that of the mentioned switch.
In some embodiments, when the antenna element operates in the first band, the first matching circuit provides a first reactance such that a total length of a resonant path of the antenna element is smaller than 0.15 wavelength of the lowest frequency in the first band, and the total length is much smaller than 0.25 wavelength of the relative prior art. When the antenna element operates in the second band, the second matching circuit provides a second reactance such that the total length of the resonant path of the antenna element is smaller than 0.15 wavelength of the lowest frequency in the second band, and the total length is much smaller than 0.25 wavelength of the relative prior art.
In some embodiments, the first band at least covers bands which are approximately from 1710 MHz to 2690 MHz, and the second band at least covers bands which are approximately from 824 MHz to 960 MHz. In some embodiments, the inductive element is a chip inductor, a distributed inductor, or a combination of the chip inductor and the distributed inductor. In some embodiments, the metal element substantially has an inverted L-shape or a triangular shape. In some embodiments, the notch of the ground element substantially has a rectangular shape or substantially has a smoothly curved edge. In some embodiments, the notch of the ground element is substantially formed at a corner of the ground element.
In some embodiments, the notch in which the antenna element is disposed has a small size of about 150 mm2 (10 mm by 15 mm). With such a small size, the antenna element can at least cover two wide bands of GSM850/900 bands and GSM1800/1900/UMTS/LTE2300/2500 bands.
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
In order to illustrate the foregoing and other purposes, features and advantages of the invention, the embodiments and figures thereof in the invention are described in detail as follows.
The first end 111 of the metal element 110 is used as a first feeding point of the antenna element 11, and the second end 112 of the metal element 110 is used as a second feeding point of the antenna element 11. The first feeding point is coupled through a switch 12 and a first matching circuit 13 to a first signal source 14, and the second feeding point is coupled through an inductive element 15 and a second matching circuit 16 to a second signal source 17. In some embodiments, each of the first matching circuit 13 and the second matching circuit 16 comprises one or more capacitors and inductors (not shown). In some embodiments, the inductive element 15 is a chip inductor, a distributed inductor, or a combination of the chip inductor and the distributed inductor. In some embodiments, the switch 12 is implemented with a PIN diode. When the switch 12 is closed, the antenna element 11 receives power from the first feeding point and operates in a first band. When the switch 12 is open, the antenna element 11 receives power from the second feeding point and operates in a second band. The frequencies of the second band are lower than the frequencies of the first band. The inductive element 15 prevents the resonant currents from flowing into the second feeding point in the first band. The first matching circuit 13 provides a first reactance, and a total length of the metal element 110 is smaller than 0.15 wavelength of the lowest frequency in the first band. The second matching circuit 16 provides a second reactance, and the total length of the metal element 110 is smaller than 0.15 wavelength of the lowest frequency in the second band. In some embodiments, the communication device 100 further comprises a control unit (not shown). The control unit selectively closes and opens the switch 12 according to a user input signal or a detection signal. In some embodiments, the communication device 100 further comprises a sensor (not shown). The sensor detects a frequency of an electromagnetic signal nearby and accordingly generates the detection signal. Note that the communication device 100 may further comprise other components, such as a touch panel, a processor, a speaker, a battery, and a housing (not shown).
The invention proposes a communication device and an antenna element therein. The antenna element comprises a ground plane antenna which is excited to generate a ground plane mode to improve the radiation performance thereof. Accordingly, the invention can effectively reduce the total size of the antenna element and the communication device, and can be suitably applied to a variety of small mobile devices.
Note that the above element sizes, element shapes, element parameters, and frequency ranges are not limitations of the invention. An antenna designer can adjust these setting values according to different requirements.
Use of ordinal terms such as “first”, “second”, “third”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
It will be apparent to those skilled in the art that various modifications and variations can be made in the invention. It is intended that the standard and examples be considered as exemplary only, with a true scope of the disclosed embodiments being indicated by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102114536 | Apr 2013 | TW | national |
