Modulator having direct digital synthesis for broadband RF trans

Details Modulator having direct digital synthesis for broadband RF trans Modulator having direct digital synthesis for broadband RF trans

1994-04-18

1995-05-02

Mis, David

Modulators

Phase shift keying modulator or quadrature amplitude modulator

375257, 375279, 375308, H03C 300

Patent

active

054123526

ABSTRACT:
A modulator for data transmitted in a reverse channel or upstream spectrum in a cable transmission system requires a single frequency translation from baseband to a selected RF channel, thus eliminating conventional intermediate frequency (IF) translation. The modulator requires fewer components than the conventional modulator while eliminating nonlinearity, noise, and delay introduced by the IF upconversion. In a preferred embodiment, the modulator includes a serial to parallel differential quadrature phase shift keying encoder with transversal FIR filters and interpolation filters connecting the phase shift keyed data to a single mixer stage for directly translating the baseband signal to an RF (e.g., 5-40 MHz) channel spectrum.

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Stanford Telecom, ASIC Custom Products Division Brochure entitled "Introduction to Direct Digital Synthesis", Jun. 1991.
Lyford et al., "Telephony over cable: CISN and CLC-500", Communications Technology 54: 46, 70, 72, 73 (Dec. 1993).

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