Method and apparatus for modulating signals

Details Method and apparatus for modulating signals Method and apparatus for modulating signals

1998-04-17

2000-11-21

Chin, Stephen

Pulse or digital communications

Transmitters

Angle modulation

332100, H04L 2712

Patent

active

061513660

ABSTRACT:
A signal modulator includes a digital signal processor, an address buffer, a counter, and a first memory device. The digital signal processor is adapted to receive digital data at a receive sampling rate and define a code word based on a subset of the digital data. The address buffer is coupled to the digital signal processor and adapted to receive the code word and store a base address. The counter is adapted to increment an address offset at a transmit sampling rate. The transmit sampling rate is a multiple of the receive sampling rate. The first memory device has a plurality of memory locations and is adapted to receive the base address and the address offset and provide a first waveform data sample from the memory location addressed by the base address and the address offset. A method for modulating a signal includes receiving digital data at a receive sampling rate. The time interval between digital data samples defines a bit interval. A code word is determined based on a subset of the digital data. A counter is initialized at the start of the bit interval. The counter is incremented at a transmit sampling rate. An address is determined based on the code word and an address offset stored in the counter. A first memory device containing waveform data is accessed based on the address. A first waveform data sample is output from the first memory device.

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patent: 5602848 (1997-02-01), Andrews et al.
patent: 5611075 (1997-03-01), Garde
patent: 5778024 (1998-07-01), McDonough
"A 270-kb/s 35-m W Modulator IC for GSM Cellular Radio hand-Held Terminals", by Johan J. J. Haspeslagh, Danny Sallaerts, Peter P. Reusens, Arnoul Vanwelsenaers, R. Granek, and Dirk Rabaey, IEEE Journal of Solid-State Circuits, vol. 25, No. 6, Dec. 1990.
"Efficient Implementation of an I-Q GMSK Modulator", by Alfredo Linz & Alan Hendrickson, IEE Transactions on Circuits and Systems--II: Analog and Digital Signal Processing, vol. 43, No. 1, Jan. 1, 1996.

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