Patent Application
20080090529
This invention describes an apparatus for enabling a base station to transmit signals with the transmit diversity technique. The following merely illustrates various embodiments of the present invention for purposes of explaining the principles thereof. It is understood that those skilled in the art will be able to devise various equivalents that, although not explicitly described herein, embody the principles of this invention.
In the signal reception mode, the base station employs the receive diversity technique, and the antennas 202a, 202b, 204a, 204b, 206a and 206b cover a wide range of signal paths, thereby improving the quality of signal reception against multi-path or fading. For example, the antennas 202a and 202b receive signals from a mobile unit (not shown in the figure) at the same time. At one moment during the signal transmission, an object moves in between the antenna tower 200 and the mobile unit, and blocks the signal path from the mobile unit to the antenna 202a. In such case, although signal reception of the antenna 202a is blocked, the antenna 202b continues to receive signals from the mobile unit and therefore ensures the reception quality.
In the signal transmission mode, the base station employs the transmit diversity technique without requiring the mobile unit to have multiple antennas. For example, the antennas 202a and 202b establish a downlink, which occupies a predetermined frequency spectrum, with a mobile unit. The antenna 202a utilizes a first frequency band of the predetermined spectrum for signal transmission, and the antenna 202b utilizes a second frequency band of the predetermined spectrum for signal transmission, wherein the first and second frequency bands do not overlap. As a result, the interference between the signals transmitted by the antennas 202a and 202b can be reduced, thereby ensuring the signal quality at the mobile unit. The predetermined distance D is preferably set to be larger than at least ten times of the wavelength of a signal transmitted from the antennas 202a and 202b in order to avoid interference. In some cases, the predetermined distance can be over twenty times of the wavelength of a signal transmitted from the antennas 202a and 202b.
The antenna placement and frequency allocations may vary without departing the spirit of the invention. For example, the number of antennas used for establishing a downlink can be greater than two, as long as the frequency bandwidths used by each antenna do not overlap. The frequency bandwidths of the antennas do not need to be equal divides, either. For example, the frequency bandwidth of the antenna 202a can be broader than that of the frequency bandwidth of the antenna 202b. In addition, the frequency bands of the antennas 202a and 202b can have an interval inserted there between to further reduce the interference.
In the signal reception mode, the base station employs the receive diversity technique with the antennas 302a, 302b, 304a, 304b, 306a and 306b to improve the quality of signal reception. In the signal transmission mode, the base station employs the transmit diversity technique without requiring the mobile unit to have multiple antennas. For example, the antennas 302a and 302b establish a downlink, which occupies a predetermined frequency spectrum, with a mobile unit. The antenna 302a utilizes a first frequency band of the predetermined spectrum for signal transmission, and the antenna 302b utilizes a second frequency band of the predetermined spectrum for signal transmission, wherein the first and second frequency bands do not overlap. Although the antennas 302a and 302b are placed in the same location, the interference between the two can be avoided as they are orthogonal in polarization.
It is noted that although the above embodiments utilize a triangular signal tower as an example for explaining various embodiments of the invention, the antenna tower can have different shapes. It is also noted that in either embodiment above, the improvement of signal transmission is noticeable.
One advantage of the present invention is that the multiple antennas implemented in the base station can be fully utilized for both receive and transmit diversity techniques. This results in a smooth radiation pattern and reduced peak radiation intensity in a free space environment. This also results in an increased probability of signal reception against multi-path and fading.
Another advantage of the present invention is its simplicity in design. Because the multiple antenna implemented in the base station can be fully utilized for both receive and transmit diversity techniques, no additional combiner is needed to combine outputs from power amplifiers when the base station transmits signals to the mobile unit.
The above illustration provides many different embodiments or embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims.
Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.
The present application claims the benefit of U.S. Provisional Application Ser. 60/851,629, filed Oct. 13, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60851629 | Oct 2006 | US |
