Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Reexamination Certificate
1999-11-10
2003-05-13
Le, Thanh Cong (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
C455S277200, C455S278100, C342S368000, C375S347000
Reexamination Certificate
active
06564044
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the use of an adaptive array in radio communications and in particular to improving the performance of communication broadcast systems that incorporate multiple signals that interfere with each other.
BACKGROUND
To obtain high quality reception, communications receivers require a signal that is uncorrupted by interference, such as multipath, adjacent channel or co-channel. One source of interference that can severely degrade reception is multipath. Multipath occurs when the transmitted signals arrives at the receiver's antenna over different propagation paths resulting in different time delays and phase shifts. The multiple paths are generally due to reflections of the transmitted signal from hills, buildings, etc. and can also be the result of atmospheric phenomena. Multipath can cause distortion in the amplitude, phase and frequency of the received signal, which can result in deep signal strength fades, frequency selective fades, intersymbol interference, noise, etc.
The same transmitting antenna can be used for the simultaneous transmission of two radio communications signals in the same frequency channel. At the receiving end, the two radio communications signals can be simultaneously received by the same receiving antenna before being coupled to their individual receivers. Both radio signals can suffer from interference (multipath and/or other shared interference) problems and require that the interference be reduced to improve reception.
Two approaches, well known in the art for reducing the effects of multipath and other interference, are the adaptive array and adaptive filter (see for example Widrow, B. & others, “Adaptive Antenna Systems”, Proceedings of the IEEE, Vol. 55, No. 12, December 1967, pp. 2143-2159; Treichler, John R., Johnson, C. Richard Jr., and Larimore, Michael G.,
Theory and Design of Adaptive Filters,
John Wiley & Sons, New York, 1987; Monzingo, Robert A. and Miller, Thomas W.,
Introduction to Adaptive Arrays
John Wiley & Sons, New York, 1980; Compton, R. T. Jr.,
Adaptive Antenna Concepts and Performance,
Prentice Hall, Englewood Cliffs, N.J., 1988; U.S. Pat. Nos. 4,736,460 and 4,752,969 by Kenneth Rilling, and others). When multiple signals are present, the use of an adaptive array or adaptive filter for each signal can be expensive, complicated and occupy too much space. For some signals, a dedicated adaptive array or adaptive filter may not provide enough performance improvement if the signal structure or available information does not lend itself to the use of an adaptive array or adaptive filter.
SUMMARY OF THE INVENTION
The present invention reduces the degradation in performance of one or more radio signals that are co-transmitted with a first radio signal from the same transmitting antenna in the same frequency channel and received by the same antenna, due multipath or other shared interference, where the one or more radio signals can be separated from the first radio signal. All received signals are coupled to the same adaptive array or adaptive filter to reduce multipath or other shared interference of the first radio signal, which simultaneously reduces multipath and other interference in the other radio signals before they are separated and processed by their respective receivers, or the individual signals are separated before the first signal enters the adaptive array or adaptive filter and each of the other signals coupled to an individual associated adaptive array or adaptive filter slave weighting network with weights slaved to the weights of the adaptive array or adaptive filter of the first signal to reduce the multipath and other shared interference in all the signals.
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Vook, Fred W., and Baum, Kevin L., Adaptive Antennas for OFDM, 48thIEEE Vehicular Technology Conference, May 18-21, 1998, pp 606-610.
Sanada, Yukitoshi, Padilla, Michael, Araki Kiyomichi, Performance of Adaptive Array Antennas with Multicarrier DS/CDMA in a Mobile Fading Environment, IEICE Trans. Commun., vol. E81/B, No. 7, Jul. 1998 pp. 1392-1400.
Raleigh, Gregory, G., and Jones, V.K., Multivariate Modulation and Coding for Wireless Communications, IEEE Journal on Selected Areas in Communications, vol. 17, No. 5, May 1999, pp. 851-866.
Widrow, B., et al., Adaptive Antenna systems, Proceedings of the IEEE, vol. 55, No. 12, Dec. 1967, pp. 2143-2159.
Cong Le Thanh
Harry Andrew T
Jones Allston L.
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