Digital pre-modulation filter

Details Digital pre-modulation filter Digital pre-modulation filter

1988-12-21

1994-06-07

Chin, Stephen

Pulse or digital communications

Repeaters

Testing

36472418, 324 7611, H04L 2503

Patent

active

053196767

ABSTRACT:
A digital pre-modulation filter with a finite impulse response having the value k(t)=h(t).multidot.w(t), where h(t) represents an impulse response of the type that is customary for a modulator, for generating in response to data signals an angle-modulated carrier signal having a substantially constant amplitude, and w(t) represents a window function by which the impulse response of the pre-modulation filter is truncated softly. It turns out to be possible to reduce the disturbing effects with respect to the power spectrum caused by such a soft truncation and cancel them with respect to the phase of the angle-modulated carrier signal. Thereto, according to the invention the impulse response k(t)=A{g(t)+x(t)}.multidot.w(t) is selected where A is a correction factor which is usually equal to one, g(t) is the untruncated impulse response of the filter, x(t) is a constant c.sub.c or a time-dependent correction function which in a preferred embodiment has such a variation that for example ##EQU1## for any integer value of i.

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patent: 4477916 (1984-10-01), Chung
patent: 4531221 (1985-07-01), Chung et al.
patent: 4731800 (1988-03-01), Motley et al.
patent: 4757519 (1988-07-01), Collison et al.
F. de Jager et al., "Tamed Frequency Modulation, a Novel . . . ", IEEE Trans. Comm., vol. Com-26, No. 5(5/78) pp. 534-542.
P. Kabal et al., "Partial-Response Signalling", IEEE Trans. Comm., vol. Com-23, No. 9 (9/75) pp. 921-934.
D. Muilwijk, "Correlative Phase Shift Keying--A Class of Constant . . . ", IEEE Trans. Comm., vol. Com 29, No. 3 (3/81) pp. 226-236.

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