Pulse or digital communications – Transmitters – Quadrature amplitude modulation
Patent
1995-11-24
1998-07-07
Chin, Stephen
Pulse or digital communications
Transmitters
Quadrature amplitude modulation
375305, H04L 2736
Patent
active
057780277
ABSTRACT:
Methods and systems for determining a cosine (I) or sine (Q) component for the purpose of modulating a digital signal in radiocommunication systems are disclosed. Exemplary embodiments describe how such determinations may be performed using digital signal processing techniques to improve component accuracy, while reducing the amount of processor memory (e.g., DSP memory) used to accomplish this task. Phase information from a sampled signal is used to access one or more tables containing component values, or a combination of a component base values and difference values between consecutive base values. The phase information can be used derive an offset value from the difference values, which offset value is added to a component base value to provide a component value for output. This has the effect of reducing the amount of memory consumed while maintaining high resolution.
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European Standard Search Report No. RS 96059 Date of Completion of Search: 12 Jun. 1996.
"Putting DDS to Work", Hickman, Electronics World and Wireless World, vol. 98, No. 1679, pp. 937-941 (Nov. 1992).
Engman Anders
Ostman Thomas
Chin Stephen
Ghayour Mohammad
Telefonaktiebolaget LM Ericsson
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