Digital quadrature amplitude modulators

Details Digital quadrature amplitude modulators Digital quadrature amplitude modulators

1996-12-13

1998-07-14

Grimm, Siegfried H.

Modulators

Phase shift keying modulator or quadrature amplitude modulator

375261, 375298, H04L 2736

Patent

active

057810761

ABSTRACT:
A digital modulator and digital demodulator with quadrature amplitude modulation (QAM) schemes, which are designed to modulate or demodulate RZ-coded baseband signals. The digital modulator includes first to fourth roll-off filters and a first and second inverters connected to the second and fourth roll-off filters. It also includes a parallel-to-serial converter to successively select the outputs of the first roll-off filter, third roll-off filter, first inverter, and second inverter. A D/A converter converts the selected digital signal stream into an analog signal. The roll-off filters and inverters operate at a predetermined clock frequency, while the parallel-to-serial converter and the D/A converter work at a frequency four times the predetermined clock frequency. The digital demodulator reverses the above modulation process to reproduce the baseband signals.

REFERENCES:
patent: 5534828 (1996-07-01), Okada et al.

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