The present invention relates to horn antennas and more particularly to an improved patch horn antenna operable in two different frequency bands.
There has been a significant growth in WLAN (wireless local area network) due to an increasing demand of mobile communication products in recent years. IEEE 802.11 WLAN protocol is the most important one among a variety of WLAN standards. The IEEE 802.11 WLAN protocol was established in 1997. The IEEE 802.11 WLAN protocol not only provides many novel functions for WLAN based communication but also proposes a solution for communicating between mobile communication products made by different manufacturers. There is no doubt that the use of the IEEE 802.11 WLAN protocol is a milestone in the development of WLAN. Further, the IEEE 802.11 WLAN protocol assures a single chip as an execution core, reduces a wireless communication cost, and enables WLAN to be widely used in various mobile communication products.
In the 1997 version of the IEEE 802.11 WLAN protocol, rules about physical layer and MAC (Media Access Control) layer are stipulated. As such, mobile communication products made by different manufacturers can not only communicate at the same physical layer but also have a consistent LLC (Logical Link Control). That is, layers under the MAC layer are transparent to network applications. The IEEE 802.11 WLAN protocol was further modified for being adapted to serve as a standard of both IEEE/ANSI and ISO/IEC in August 2000. The modifications comprise an embedded MIB (Management Information Base) of SNMP (Simple Network Management Protocol) for replacing an original MIB of embedded OSI, and two new protocols as follows:
(1) IEEE 802.11a WLAN protocol: It expands the standard physical layer, stipulates an operating frequency band of 5 GHz of the physical layer, uses an orthogonal frequency division technique for modulating data, and stipulates a data transfer rate between 6 Mbps and 54 Mbps in order to meet requirements of both indoor and outdoor wireless communication applications.
(2) IEEE 802.11b WLAN protocol: It is another expansion of the IEEE 802.11 WLAN protocol. It stipulates an operating frequency band of 2.4 GHz of the physical layer, uses CKK (compensation keyboard control) as a modulation technique in which the CKK is derived from a direct serial frequency expansion technique, and uses a multiple speed MAC for ensuring an automatic slowdown of data transfer rate from 11 Mbps to 5.5 Mbps when a distance between two adjacent workstations is too long or interference is severe. Alternatively, the above data transfer rate can be adjusted to 2 Mbps or 1 Mbps by employing the direct serial frequency expansion technique.
The operating frequencies of the standard physical layer are required to set at 5 GHz and 2.4 GHz based on IEEE 802.11a and IEEE 802.11b WLAN protocols respectively. Hence, several antennas are required to install in a wireless electronic product for complying with requirements of frequency band if the product is about to use the IEEE 802.11a and IEEE 802.11b WLAN protocols. However, such can increase a manufacturing cost, complicate an installation procedure, and consume precious space of the product for installing the antennas. As a result, the size of the product cannot be reduced, thereby contradicting the compactness trend.
Recently, there is a trend among wireless communication product designers and manufacturers to develop an antenna capable of operating in two different frequency bands (i.e., dual frequency antenna) in developing electronic products of dual frequency. It is envisaged that the use of dual frequency antenna in a wireless communication product can decrease the number of antennas provided therein and occupied space thereon. Unfortunately, commercially available dual frequency antennas such as chip antennas or patch antennas made by a printing process are not satisfactory in an operating frequency of 5 GHz. Some antennas can meet required features. However, they are bulky, resulting in an unnecessary consumption of space. Moreover, separately manufactured components are required for the well-known dual frequency antennas. Such components are then assembled in the well-known dual frequency antenna prior to together installing in the wireless communication product. Inevitably, it will increase manufacturing and assembly costs, thus contradicting both the cost reduction principle and the mass production trend.
A conventional antenna such as horn antenna 10 well known to wireless communication product designers and manufacturers is shown in FIG. 1. Signal waves are fed into the antenna 10 via a coaxial cable 11. The antenna 10 has advantages such as wide bandwidth, high antenna gain, and distinct polarization direction. Hence, the horn antennas 10 are widely used in experiments as a standard antenna for measuring radiation pattern or gain of a typical antenna. However, the horn antenna 10 is bulky and expensive. Hence, the conventional horn antennas are not suitable and even impossible to install in a typical wireless communication product.
An equivalent patch horn antenna 20 improved from the above horn antenna 10 by one of wireless communication product manufacturers is shown in FIG. 2. The patch horn antenna 20 is formed on a circuit board 9 during a printed circuit board manufacturing process. Characteristics of the patch horn antenna 20 is simulated by effecting various transmission line 21 feed designs in order to produce various patch horn antennas 20. The patch horn antenna 20 as some characteristics of the horn antenna 10. But the patch horn antenna 20 also has several characteristics different from that of the horn antenna 10 due to the use of a transmission line 21 or a matched structure 22. The patch horn antenna 20 is typically designed to operate in a single frequency. As a result, it cannot be incorporated in a wireless communication product of dual operating frequencies.
A widely used dual frequency antenna such as chip antenna 30 is shown in FIG. 3. As seen, a patch antenna 32 having a required shape is printed on a ceramic substrate 31. Next, the chip antenna 30 is formed on a circuit board 9. A patch line 33 of the antenna 30 is used as a feed transmission line for signal wave feed. Typically, the chip antenna 30 has a narrow effective bandwidth in a high frequency range. Thus, the chip antenna 30 cannot satisfy a bandwidth of operating frequency required by a wireless electronic product. Also, the chip antenna 30 is low in antenna gain. In addition to the above drawbacks, additional components are required for installing the chip antenna in the wireless electronic product, resulting in an increase of both manufacturing and assembly costs. Hence, it is not desirable to mount the chip antenna 30 in the wireless electronic product. Thus, the need for improvement still exists.
A primary object of the present invention is to provide a patch horn antenna of dual frequency formed on a printed circuit board of a wireless electronic product during a printed circuit board manufacturing process in which the horn antenna is formed on one side of the print circuit board for significantly reducing the manufacturing cost. Most importantly, the horn antenna can have sufficient bandwidths in two different frequency bands, resulting in an increase of system performance of the wireless electronic product. By utilizing this, the above drawbacks of the prior art chip antenna of dual frequency such as narrow bandwidth, low antenna gain, and high in both the manufacturing and assembly costs can be overcome.
One object of the present invention is to provide a patch horn antenna of dual frequency. A first patch line as a feed transmission line of the patch horn antenna is formed on the other side of the printed circuit board by means of signal wave coupling. The invention can control the ranges of two frequency bands by adjusting the length of the patch horn antenna. Alternatively, the invention can either control an antenna gain by adjusting a degree of the angle between two oblique sides of a horn opening or control a match between high and low frequency bands by adjusting a coupling area between an elongate recess and the first patch line. As an end, the produced patch horn antenna has advantages of simple structure, easy manufacturing, and reduced cost as well as can satisfy product specifications.
Another object of the present invention is to provide a second patch line at the opening of the horn antenna, the second patch line being extended from the mouth of an opening of the horn antenna at one oblique side toward the other oblique side of the opening. It is possible of effectively controlling the ranges of the frequency bands for obtaining a good match between high and low frequency bands by adjusting the size of the second patch line.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.