Communications: directive radio wave systems and devices (e.g. – With particular circuit – Display
Patent
1986-03-21
1988-10-25
Blum, Theodore M.
Communications: directive radio wave systems and devices (e.g.,
With particular circuit
Display
342383, G01S 338
Patent
active
047807210
DESCRIPTION:
BRIEF SUMMARY
GENERAL PURPOSE
The general purpose of this invention is to permit directional interference sources (atmospheric noise, other users etc.) to be removed from received communications signals, while maximizing the desired signal through the use of an adaptive antenna array.
BACKGROUND
The present invention relates generally to the field of adaptive antenna array processors for use in adaptive antenna array systems that remove undesired signals from the received signal and at the same time maximize the signal-to-noise ratio by forming a beam on the desired signal.
In omnidirectional high-frequency communication systems, undesired interfering signals from various localized sources lying in various directions can be received along with the desired signals. If these signals are powerful enough, they can seriously degrade performance. The effect of these interfering signals can be reduced or negated by employing an adaptive antenna array. An adaptive antenna array utilizes at least two antennas hereafter referred to as antenna elements, with a receiving system. By appropriately weighting and summing the outputs of the signals received by these antenna elements, the interfering signals can in general be reduced or cancelled.
Typically, these prior art adaptive antenna arrays required a large number of samples to be taken before a null could be formed on an interfering signal, and a beam formed on the desired signal. Also, they could not null an interfering signal without also nulling the desired signal unless either the signal contained a reference identifier, or else the direction of the signal was known.
The use of adaptive spatial nulling techniques to remove undesired signals from desired signals has been established for many years in both the radar and communications fields. See for example, Monzingo and Miller, "Introduction to Adaptive Antenna Arrays", John Wiley and Sons, 1981.
SUMMARY OF THE INVENTION
The present invention is a digital adaptive antenna array processor which does not require either the direction of the desired signal to be known, or the desired signal to contain any special reference pattern or spreading code to be continuously present. Instead, the present invention relies merely on a knowledge of the time when the desired signal is not present. Waveforms which have a known "time-out" are found in Time Division Multiple access systems, frequency hopping systems and polling or "roll call" systems. The present invention partitions the optimization problems of formation of nulls and beams and the identification of individual interference sources by the monitoring of individual nodes of the array processor, and dynamically reconfigures the array processor to meet the changing environment. The present invention not only reduces or eliminates atmospheric and other-user interference, but also counters sophisticated pulse jamming techniques, generally in one sample.
In accordance with the present invention the in-phase and quadrature baseband signals derived from the output of each antenna in the array are digitized in analogue-to-digital converters and the inputs to the present invention are these digitized baseband components. The baseband components can be obtained, for example, as described in Nathanson, "Radar Design Principles", McGraw Hill, New York, 1969, page 472.
These digitized samples are then processed in a digital signal processor which performs linear algebraic operations on the incoming data. By performing orthogonalization operations on the outputs of two antennas, a complex weight can be determined which, when multiplied by the output of the first antenna and the resultant added to the output of the second antenna, will cause a directional interference source to be minimised in the resultant.
By monitoring each of the orthogonalizer nodes with an intelligent controller, sufficient information can be obtained to make this algorithm superior to others for any communication system which has a known time period in which the transmitter is not transmitting. For example, the num
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Introduction to Adaptive Arrays; Robert A. Monzingo and Thomas W. Miller; pp. 364-377.
Cascade Preprocessors for Adaptive Antennas; Warren D. White; pp. 670-684.
IEE Processings, vol. 131, Pt. F, No. 6, Oct. 1984, C. R. Ward et al, "Application of a Systolic Array to Adaptive Beam Forming".
Blum Theodore M.
Hellner Mark
The Commonwealth of Australia
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