Method and circuits for combining baseband signals and recovery

Details Method and circuits for combining baseband signals and recovery Method and circuits for combining baseband signals and recovery

1994-07-01

1997-01-07

Chin, Stephen

Pulse or digital communications

Receivers

Interference or noise reduction

375350, 375355, 455137, H04L 102, H04L 700

Patent

active

055925162

ABSTRACT:
The invention relates to a baseband signal combiner and to a sampler typically used in radio relay systems and also in generic communication systems. In order to avoid temporary failures in the free space links, space and/or frequency diversity techniques are used, which consist in the use of two suitably spaced receive antennas or of two transmission frequencies. By suitably combining the signals thus received, the failures in radio links can be redued. The invention provides the use of a particular algorithm of the type CMA (Constant Modulus Algorithm) which, being independent of the combined signal phase, does not interact with the carrier recovery circuits. Moreover, by also applying the same algorithm to the sampler, the cooperation of the two circuits for the optimization of the output signal is obtained.

REFERENCES:
patent: 4512034 (1985-04-01), Greenstein et al.
patent: 4797950 (1989-01-01), Rilling
"Blind Algorithm for Joint Clock recovery and baseband Combining in Digital Radio" F. Gudielmi et al, IEEE Radio Relay System, 1993, pp. 279-286.
Interference Rejection. "Using Time Constant Modulus Algorithm (CAM) and Hybrid CMA/Spectral Correlation Discriminator", R. Uendozo et al, IEEE Tran on Srg. processing, 1991, pp. 2108-2111.
"Joint Blind Equalization, Carrier Recovery, and Timing Recovery for 64 of 128 QAM Signal Consellation" Neil K. Jablen, IEEE International Conf., 1989, pp. 1043-1049.
"Decision Directed Diversity Combiners Principles and Simulation Results" by J. A. Henriksson published in IEEE Journal on Selected Areas in Communications, vol. SAC-5, No. 3, Apr. 1987.
"MMSE baseband combiner for microwave digital radio" by A. N. D'Avolio, et al published in Conference Record, 2nd European Conference on Radio Relay System, pp. 235-242, Apr. 1989.
"Convergence Behaviours of the Constant Modulus Algorithm" by M. G. Larimore et al, published in Conference Record, IEEE Int. Conference on Acoustic Speech Signal Processing, pp. 13-16, Apr. 1983.
Electronics & Communications in Japan, Part I --Communications, vol. 74, No. 9, Sep. 1991, New York US, pp. 43-53.
XP00029159, T. Ohgane, "Characteristics of CMA Adaptive Array for Selective Fading Compensation in Digital Land Mobile Radio Communications".
Proceedings of 1986 IEEE Military Communications Conference -Milcom '86, 5-9 Oct. 1986, Monterey, CA pp. 47.3 1-47 3.5.
J. Treichler and M. G. Larimore, "CMA-BAsed Techniques for Adaptive Interface Rejection".

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