Patent Grant
7548764
This invention relates generally to antenna systems, and more particularly to the use of a transform matrix of an antenna array to generate multiple radiation patterns.
In communication systems, whether they conform to GSM, CDMA, or other technology standards, the communications between the base stations and the mobile terminals typically include one or more traffic channels for communicating data signals and one or more control channels for exchanging control signals. For some signal control channels, for example, a pilot channel of CDMA systems, the control signals have to be broadcasted omni-directionally to cover the whole or sectored cell. On the other hand, it is desirable to steer narrow beams formed for communicating through traffic channels with specified mobile equipment without interfering with other mobile equipment nearby. The beam formed pattern is directed to particular users, and it has a narrow beam width.
Logically, this can be done by two approaches: the first approach is to generate the beamforming pattern via one set of antennas and generate the omni pattern via another set of antennas. The second approach is to use a single set of antennas but the omni pattern needs to be synthesized with the beamforming pattern. However, the first approach will add the costs associated with the omni pattern generation. The physical arrangement of two antenna sets also adds some difficulties to the first approach. There are discussions about beam forming and omni broadcast synthesis issues. The difficulties of synthesizing omni-broadcast patterns with beam forming means remain as challenges awaiting newer and better engineering solutions.
Therefore, there exists a need to provide an improved approach that allows antenna arrays to provide both beam forming and omni patterns simultaneously without the need of either an additional antenna set for omni pattern or omni pattern synthesis.
A system and method for generating multiple radiation patterns is disclosed here. An antenna system comprises an antenna array having one or more antennas for providing a first radiation pattern and a second radiation pattern, a transform matrix for transforming one or more inputs into one or more outputs according to a transform function, wherein the outputs of the transform matrix provide signals to the antennas with predetermined phases and magnitudes for generating the first and second radiation patterns, and a transmitter for providing a first set of signals corresponding to the first radiation pattern and a second set of signals corresponding to the second radiation pattern to inputs of the transform matrix.
One object of this present invention is to provide an antenna system, which comprises an antenna array having N antennas for providing a first radiation pattern having a narrow beam width and a second radiation pattern having a wide beam width, a transform matrix for transforming N input ends into N output ends according to a transform function M, and a transmitter. The N outputs of the transform matrix provide signals to the N antennas with predetermined phases and magnitudes for generating the first and second radiation patterns. The transmitter is configured to provide a first set of signals to the N inputs of the transform matrix corresponding to the first radiation pattern and a second set of signals corresponding to the second radiation pattern. The transform matrix combines the first and second sets of the signals for generating the predetermined phases and magnitudes needed for the first and second radiation patterns.
Another object of this invention is to disclose a method for generating multiple radiation patterns. The method comprises after determining a first output weight corresponding to a first radiation pattern having a first beam width and a second output weight corresponding to a second radiation pattern having a second beam width to be transmitted by the antenna array, first and second input weights are obtained based on a transform function of a predetermined transform matrix coupled to the antenna array and the first and second output weights. A first and second set of input signals are then generated corresponding to the first and second radiation patterns to be programmed with the first and second input weights respectively.
Although the present invention is illustrated below with regard to a few limited examples, it is understood that the present invention is applicable to any multiple access technologies. Such access technologies include Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Orthogonal Frequency Division Multiplex (OFDM) systems and any combination thereof, whether synchronized or unsynchronized, using Frequency Division Duplex (FDD) or Time Division Duplex (TDD).
As an example, assuming that the number of antennas 110 of this antenna array 110 is eight, it implies that N is equaled to 8. In order to generate a first desired radiation pattern, denoted as N1, an N×1 vectored signal weight, denoted as W1 with appropriate phases and magnitudes corresponding to this first radiation pattern N1, has to be fed into the transmission ends 122 from the output ends 132 of the transform matrix 130. Likewise, in order to generate the i-th desired radiation pattern, denoted as Ni, a corresponding vectored signal weight, Wi, may be fed into the transmission ends 122 and then fed into the antenna array 110.
The vectored signal weight, Wi, for each radiation pattern, Ni, can be determined according to the properties of previous signals exchanged in the communication system in the past or based upon some certain criteria. For example, a vectored signal weight steering narrow-formed beam to a specified mobile terminal is determined by identifying incoming direction of the specified mobile terminal's transmission. In another example, a predetermined vectored signal is determined after the antenna array 110 is physically settled in order to broadcast omni-directionally. The outputted signals of the transmitter 140 could be combined and placed in one or two of the output ends 132 as well as the corresponding antennas 110 by the transform matrix 130.
Since the transform matrix equation M and its inverse transform equation
Wi′=
the equation above is derived from the following transformation equation:
Wi=M*Wi′
wherein Wi′ is a 1×N vector corresponding to the N×1 vector of Wi. Supposing that Wo and Wbare weights for frequency or time diverse signals, Wo is usually for common control and Wb is dedicated for traffic signals. For the purpose of common control broadcast, the radiation pattern generated with Wo has a wide beam width. On the other hand, the radiation pattern generated with Wb has a narrow beam width. Therefore, by applying the inverse transform equations above, Wo′ and Wb′ could be generated and applied by the base station to N signals, which are then fed to the input ends 134 of the transform matrix 130 to generate radiation patterns with the original required weights W0 and Wb. This process assures that the desired two different patterns with expected weights are produced.
After the transform function M provided by the transform matrix 130, two intended radiation patterns generated with appropriate weights Wb and Wo are going to the transmission ends 122 of the Tx/Rx duplexer array 120 from the output ends 132 of the transform matrix 130. Therefore, the radio frequency signals emitted by the antennas 110 of the antenna array 110 could be formed in a narrow beam width and a wide beam width simultaneously.
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In this example, it is assumed that there are two different radiation patterns that are needed, one having a narrow beam width and the other a wide beam width. In order to differentiate the two radiation patterns, they should have their corresponding vector weights. Based on the expected first radiation pattern, a first output vectored signal weight corresponding to the first radiation pattern (e.g., having a narrow beam width) is determined dynamically in step 208. Also in step 212, a second output vectored signal weight of a second radiation pattern (e.g., having a wide beam width) is determined. These two steps may be processed concurrently or in reverse order. It is thus noted that the order of these two steps is not important. Since the transform equation of the transform matrix is known, its inverse function is also determinable. The base station has to generate signal inputs with appropriate input weights so that, when they pass the transform matrix, the output signals from the transform matrix will carry the expected first and second output vectored signal weights to form the two radiation patterns. A first input vectored signal weight could be calculated by applying the inverse of transform function with the first output vectored signal weight in step 216. Similarly, a second input vectored signal weight could be calculated by applying the inverse of transform function with the second output vectored signal weight in step 220. It is also understood that the calculation of the first and second input vectored signal weights in steps 216 and 220 could be done in parallel or in a reverse order. Therefore, in the final step 224, the base station generates the first and second signals corresponding to the first and second radiation patterns with the input vectored signal weights applied therewith. After they are applied with the corresponding weights, the first and second signals become signal vectors of N×, where N is the number of antennas. After combining and feeding these two vector signals through the transform matrix to the antenna array, two desired radiation patterns will be generated.
As an alternative, all inputs to the transform matrix can be combined within the matrix to only generate a single output or a selected number of outputs to be transmitted to a designated antenna or elements. For example, if a particular antenna in the antenna array is designed to transmit the wide beam pattern, the input weights can be adjusted so that signals on other antennas are nulled (e.g., W=[I, 0, 0, 0 . . . 0]). Further, it is also possible that one radiation pattern is generated by the antenna away while the other radiation pattern is only transmitted by one particular antenna within the array. Or, a subset of antennas within the antenna array is producing one pattern, while another subset of the antennas is producing other patterns.
The above disclosure provides many different embodiments, or examples, for implementing different features of the invention. Also, specific examples of components and processes are described to help clarify the invention. For example, the above described process can be applied to generate more than two patterns if needed. These are, of course, merely examples and are not intended to limit the invention from that described in the claims.
While the invention has been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
This application claims the benefits of U.S. Patent Application Ser. No. 60/658,839, which was filed on Mar. 4, 2005 and entitled “Using Transform Matrix to Generate Multiple Desired Radiation Patterns.”
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