Multiplex communications – Wide area network – Packet switching
Patent
1985-02-12
1987-04-28
Griffin, Robert L.
Multiplex communications
Wide area network
Packet switching
375 39, 332 21, H04J 300
Patent
active
046619488
ABSTRACT:
In a quadrature amplitude modulator, two binary, synchronous data signals representing four possible phase states of a carrier signal are sampled and respectively fed into two shift registers comprising part of a finite impulse response lowpass filter. The samples in each corresponding pair of stages in the shift registers are multiplexed at twice the carrier frequency. Each multiplexer output is then added modulo-two to a binary signal at the carrier frequency using exclusive-OR gates. The gate outputs are weighted in a desired fashion and summed and converted to an analog signal which exhibits a preferred spectral shape. This approach enables the quadrature amplitude modulation function to be included within the structure of the finite impulse response lowpass filter. The binary synchronous nature of the input data enables the structure of the filter to be simplified and the number of multiplexers and modulo-two adders to be reduced to a number equal to the number of bits stored from the input sequences. An extension of this basic concept includes higher levels of encoding, specifically the case of sixteen or more possible phase and amplitude states of a carrier signal. The particular method for weighting and summing the multiplexed and modulated signals may utilize digital logic combined with resistors, switched capacitors, or a stored program combined with a digital-to-analog converter, and is suitable for integrated circuit fabrication.
REFERENCES:
patent: 3349181 (1967-10-01), Ito
patent: 3793588 (1974-02-01), Gerwen et al.
patent: 3985961 (1976-10-01), Voss et al.
patent: 4347616 (1982-08-01), Murakami
patent: 4455649 (1984-06-01), Esteban et al.
patent: 4527275 (1985-07-01), Russell
patent: 4550416 (1985-10-01), Rosanes
Meyer Charles S.
Shapiro Garry R.
Chin Stephen
Fairchild Semiconductor Corporation
Griffin Robert L.
LaBarre James A.
Michaud, Jr. Frederick G.
LandOfFree
Digital quadrature amplitude modulator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital quadrature amplitude modulator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital quadrature amplitude modulator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-481052