SINGLE INPUT/OUTPUT MESH ANTENNA WITH LINEAR ARRAY OF CROSS POLARITY DIPOLE RADIATING ELEMENTS

BACKGROUND OF THE INVENTION

The present invention relates generally to antennas for receiving radio signals, and more particularly to an improved antenna of simplified construction capable of resolving electromagnetic signals more efficiently and at far greater distances than heretofore for an antenna of the size and cost of the present invention, using a linear array of dipole antenna elements configured on a circuit board in combination with a combiner designed to sum incoming signals of two polarities simultaneously for significant reduction or elimination of multipath fade without the need for piggyback processing.

Wireless Local Area Networks (WLANs) are used to transmit electronic data between computers, servers, and other data storage devices over relatively short distances. The data can be transmitted between areas in a building, between different buildings, and between a building and an external antenna. WLAN systems utilize antennas that operate in designated frequency bands, such as the unlicensed 2.4 GHz frequency band utilized by laptop and desktop computers among other devices. These systems enable wireless communications between separate devices, but the present antennas limit the distance between devices to roughly 100 feet for reliable transmission. Because the distance is limited, more antennas are required to cover a specified area. If the effectiveness of the antenna can be improved, each antenna station can service a greater area and thereby eliminate a great number of stations. This will lead to greater cost savings as the number of stations are reduced.

One reason for the limit on the range of present antennas is the presence of deterioration of the incoming signal due to multipath interference. Wireless WLANs as well as other wireless data telecommunication systems suffer from this problem, referred to as multi-path fading. In wireless telecommunications, multipath is the propagation phenomenon that results in radio signals' reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflection from terrestrial objects, such as mountains and buildings. The deleterious effects of multipath include constructive and destructive interference, and phase shifting of the signal.

Diversity reception is often used to overcome the problem of severe multi-path fading. A diversity technique requires at least two signal paths that carry the same information but have uncorrelated multipath fadings. Several types of diversity reception are

used at base stations in the wireless data and telecommunications industries including space diversity, direction diversity, polarization diversity, frequency diversity, and time diversity. A space diversity system receives signals from different points in space requiring two antennas separated by a significant distance. Polarization diversity does not require large spatial separateness of the antennas, but rather uses closely spaced orthogonal polarization to provide the uncorrelated signal paths to eliminate multipath fade.

As is well-known in the art, the sense or direction of polarization of an antenna is measured from a fixed axis and can vary, depending upon system requirements. In particular, the sense of polarization can range from vertical polarization (0 degrees) to horizontal polarization (90 degrees). Currently, the most prevalent types of polarization used in systems are those which use vertical, horizontal, or +45 degree/-45 degree polarization ("slant 45 degree"). However, other angles of polarization can be used. If an antenna receives or transmits signals of two polarizations normally orthogonal, they are also known as dual polarized antennas.

An array of slant 45 degree polarized radiating elements can be arranged using a linear or planar array of crossed-dipoles located above a ground plane. A crossed dipole is a pair of dipoles whose centers are co-located and whose axes are orthogonal. The axes of the dipoles are arranged such that they are parallel with the polarization sense required. In other words, the axes of each of the dipoles are positioned at some angle with respect to the vertical axis of the antenna array. One such array is taught by Dearnley et al., U.S. Patent No. 5,952,983, the contents of which are fully incorporated herein by reference. [

There have been many efforts in the prior art to develop a more efficient antenna for transmitting wireless data. U.S Patent No. 5,966,102 issued October 12, 1999 to Runyon discloses a planar array antenna having radiating elements characterized by dual simultaneous polarization states. However, Runyon teaches that each radiating element is connected to a distribution network, which in turn is connected to a polarization forming network (PCN). The polarization forming network controls the polarization states of the signals received from the radiating elements through the distribution network.

U.S. Patent No. 6,717,555 issued April 6, 2004 to Teillet et al. discloses an antenna array comprising a series of unitary dipole antenna each fed by two feed systems separated above a ground plane. Phase shifters in combination with a down-tilt control lever are

slidably adjusted beneath the respective dividing portions of the feed systems to adjust signal plane and achieve a uniform beam tilt.

While the teachings of Dearnley, Runyon, and Teillet demonstrate the benefits of a linear dipole array, these antennas lack a simple method of combining the incoming signals in a simple and reliable manner. Rather, these prior art systems rely on secondary processors to process the signals, resulting in complex couplings and multiple input/output connections. Accordingly, the art is in need of an antenna that can extend the distances between bases using a reliable and cost effective antenna without reliance on secondary processing apparatus to process the incoming signals.

SUMMARY OF THE INVENTION

The present invention addresses the shortcomings of the prior art by disclosing a wide area directional antenna or an omni directional antenna comprising a linear array of cross polarity dipole radiating elements mounted at one-quarter wavelengths along a circuit board serving as the ground plane. Each radiating element serves as a high performance data base, and a hybrid combiner on the circuit board sums the signals from each data base before forwarding the radio frequency signals to a connected external device such as a radio. The radiating elements comprise two intersecting orthogonal dipole antenna forming an "X" shaped structure with electromagnetic wave receiving components adapted to receiving incoming data signals and transmit outgoing data signals in the form of electromagnetic waves. The two intersecting orthogonal antenna define four panels each offset forty-five degrees from the longitudinal direction of the ground plane. The ground plane is a platform in the form of a circuit board capable of communicating electromagnetic signals received from the radiating elements. On the circuit board is an integrated hybrid combiner, aka "rat race" that is coupled to a single coaxial data port. Importantly, the path from each radiating element to the coaxial data port is arranged to be equidistance, such that the signals from the plus 45 degree slant antenna and minus 45 degree slant antenna are simultaneously received and combined to fortify the signal strength mechanical amplification or electronic signal processing. The hybrid combiner thus allows a single output (which also serves as the input for transmitting signals), and eliminates the need for a PCN or other complimentary processing equipment.

Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an elevated perspective view of a first preferred embodiment of the present invention showing a 180° coverage antenna;

Fig. 2 is an enlarged, elevated perspective view of a radiating element of Fig. 1;

Fig. 3 is an exploded view of the conducting board and metal cover plate of the embodiment of Fig. 1; and

Fig. 4 is a second preferred embodiment showing a 360° coverage antenna.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment of the present invention is depicted in Fig. 1, which shows an antenna 20 for a communicating wireless information to a laptop computer, desktop computer, cellular device, radio, or other peripheral suited for a WLAN network, cellular network, or other wireless application. In particular, the antenna 20 is particularly well suited for transmission of data such as communication and high speed internet applications. The antenna 20 is comprised of four data bases in the form of cross polarized radiating elements 22 arrayed in a linear arrangement across the platform 26. Both vertical and horizontal polarization can be achieved via the four dipole radiating elements 22, which are each formed from two separate planar panels 24 arranged at plus or minus forty- five degrees with respect to a line connecting the common axes 28 of the radiating elements 22. The radiating elements 22 are preferably spaced one quarter wavelength apart on the platform 26, such that each data base corresponds to a quarter wave node. The type and size of the radiating elements help to determine the radiation characteristics, beam width, and the impedance of the antenna. The radiating element is a dipole in the form of a printed circuit board capable or receiving and transmitting electromagnetic signals. Other suitable radiating elements can be substituted as is known in the art. The gain of the antenna is proportional to the number of radiating elements present in the array, such that the antenna's gain can always be increased by adding additional radiating elements to the array. Therefore, although four radiating elements are shown, the number of radiating elements can be increased to any number to

increase the gain. Conversely, the number of radiating elements can be reduced as required thereby reducing the gain.

The array of crossed, dual-polarized dipole radiating elements 22 are mounted above the platform 26 that serves as a ground plane. The platform 26 is formed of a metal such as aluminum, copper, brass, or other conductive material. As shown in Fig. 3, the ground plane/circuit board 32 can be protected by outer board layer 48 that is metallic or has a metallic outer layer. The circuit board 32 includes an imprinted combiner, or "rat race", which receives the signals from the radiating elements 22 at starting point 34a-d, respectively. Each starting point has two paths, corresponding to the positive 45° antenna and the negative 45° antenna. For example, at starting point 34a, path 38 may correspond to the positive 45° antenna and path 40 may correspond to the negative 45° antenna, where both paths initiate at starting point 34a and terminate at juncture 42. Because the distance traveled along path 38 is identical to the path 40, a signal received at the positive 45° antenna and the negative 45° antenna will arrive at the juncture at the exact same time and undergo reinforcement of the signal to reverse the effect of the multipath fading.

Similarly, paths 39 and 41 are of equal length and result in the signals from starting points 34c,d to juncture 42 and result in a stronger signal at the juncture when the two incoming signals are combined. Multipath fading is significantly reduced or eliminated through the combination of signals received from the positive 45° and the negative 45° antennas. Signals are added vectorially in the combiner before passing through output port 50. The combiner further enhances the dual polarization capabilities of the present invention by producing multi in-phase signals at output port 50 that are proportional to the level of a common input signal. The combiner also splits signals received from connected equipment through port 50 into multiple equal outputs that are transmitted by the radiating elements 22. These enhancements result in significant reception and transmission efficiency for the connected equipment and remote equipment .

As shown in Fig. 4, a second embodiment of an antenna 120 is shown having a first array of radiating elements 22 on a first surface of said circuit board 32 and a second array of radiating elements 22a on an opposite surface of said board. In this embodiment, two identical hybrid controllers such as that shown in Fig. 3 are formed on respective sides of the board 32 allowing the range of signals to increase from 180 degrees for the antenna shown in Fig. 1 to 360 degrees for the antenna shown in Fig. 4.

In both the embodiment 120 of Fig. 4 and the embodiment 20 of Fig. 1, the juncture 42 is coupled to a coaxial data port 50 that may be connected to a coaxial cable or other transmission means to communicate the received signal to the peripheral. Other types of data ports are also used with the present invention, and the port shown is illustrative only and should not be deemed limiting in any manner.