Pulse or digital communications – Repeaters – Testing
Patent
1992-06-15
1994-05-10
Kuntz, Curtis
Pulse or digital communications
Repeaters
Testing
375 53, 375 57, 375 60, 375 67, 375 85, 375 94, 332103, 329304, H04L 512, H04L 2302
Patent
active
053115520
ABSTRACT:
An optimum communication system for communicating on adjacent frequency bands with minimal interference between adjacent channels comprises an encoder that is serially coupled to a mapper and two parallel processing branches, each processing branch having a transmit filter a digital-to-analog converter, a low pass filter and a modulator coupled in series. Both modulators are coupled to a summer, and an rf amplifier having a transmit antenna. The encoder is optimized by choosing a desired minimum Euclidean distance (DMED) between symbols, an encoder alphabet and a number of constellation points, permutating all possible encoder states and all possible input symbols to result in a plurality of encoder sets U, determining an in-band to adjacent band power ratio P.sub.ib /P.sub.ab for each code set is determined, discarding code sets U that having a minimum distance between symbol sets that do not exceed DMED, shifting by 90 degrees with respect to each other the phase of the signals passing through the modulators, and transmitting to a receiver the summation of the signals in each one of the parallel processing branches, whereby the encoder produces the code set of the remaining sets having the largest in-band to adjacent band power ratio P.sub.ib /P.sub.ab resulting in a transmitted signal having a spectrum that maximizes the ratio of in-band to adjacent band power for LMR systems. Maximizing the in-band to adjacent band power increases the ACIPR and also allows for increased data transmission rates.
REFERENCES:
patent: 5164963 (1992-11-01), Lawrence et al.
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S. Ramseier, "Bandwidth-Efficient Trellis coded Modulation Schemes", 1990, Proceedings of the International Conference on Communications, pp. 1517-1521.
MacMillan Publishing Co., Introduction to Trellis Coded Modulation with Applications, "Computer Programs: Design Technique", 1991, pp. 527-539.
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Anderson John B.
Chennakeshu Sandeep
Hassan Amer A.
Bocure Tesfaldet
General Electric Company
Kuntz Curtis
Snyder Marvin
Zale Lawrence P.
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