Digital GMSK modulator with non-integer bit interval handling

Details Digital GMSK modulator with non-integer bit interval handling Digital GMSK modulator with non-integer bit interval handling

1990-05-25

1991-06-04

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

332100, H03K 706, H04L 2712

Patent

active

050220543

ABSTRACT:
A modulation circuit is used in GMSK modulation system. The system includes I-channel and Q-channel ROM look-up tables, each preprogrammed for generating a representative digital waveform based on an input data stream and a clock signal. Each digital waveform is converted to an analog signal for subsequent radio frequency (RF) modulation. Each ROM is addressed by an interpolation counter controlled by a clock signal, by a data shift register receiving input data at a rate corresponding to the clock signal, and by an quadrant register, also receiving the input data, for specifying the phase of the data signal with respect to the clock signal. Additionally, a signal indicates a time at which synchronization to the system clock is required and such synchronization requires synchronizing at a non-integer bit interval time, and in response to that signal, the address of the ROMs is adjusted in order to modify the phase of the data signal so that it is consistent with the system clock requirement.

REFERENCES:
patent: 4414675 (1983-11-01), Comroe
patent: 4562581 (1985-12-01), Tanaka et al.
patent: 4581749 (1986-04-01), Carney et al.
patent: 4606051 (1986-08-01), Crabtree et al.
patent: 4686688 (1987-08-01), Chung et al.
"Digital Phase Modulation", by John B. Anderson, Tor Aulin and Carl-Erik Sundberg, Plenum Press, New York and London, 1986, pp. 209-235.
"Single-Chip Baseband Waveform Generator CMOS-LSI for Quadrature-Type GMSK Modulator", Electronics Letters, 11th Oct. 1984, vol. 20, No. 21, pp. 875-876.
"GMSK Modulation for Digital Mobile Radio Telephony", by Kazuka Murota, IEEE Transactions on Communications, vol. COM-29, No. 7, Jul. 1981, pp. 1044-1050.
"Bit Synchronization of Differentially Detected MSK and GMSK", by Marvin K. Simon and Charles C. Wang, 1985 IEEE, No. CH21-75-8/85/000-0583, pp. 583-590.

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