Modulators – Phase shift keying modulator or quadrature amplitude modulator
Patent
1995-05-08
1996-04-30
Grimm, Siegfried H.
Modulators
Phase shift keying modulator or quadrature amplitude modulator
332104, 375283, 375308, H04L 2720
Patent
active
055128653
ABSTRACT:
The preferred embodiment modem is an all hardware modulator which receives as its input two baseband drive signals, I and Q, which can come from a ROM filter or any other digital filter. Instead of storing modem responses in a ROM, multiplexers for the I and Q channels are used in combination with a control circuit to essentially perform as sine/cosine modulators for the baseband signal. The inputs into the I channel multiplexer include a non-inverted I signal, an inverted I signal, and a mid-value signal. The Q channel multiplexer has applied to it a non-inverted Q signal, an inverted Q signal, and a mid-value Q signal. Two-bit counters are applied to the control terminals of the I and Q multiplexers, where the 2-bit counters are clocked by a sample frequency. In one embodiment, the sample frequency is chosen to be four times the carrier frequency. The counter for the Q channel begins one count behind the I channel counter, thus giving a 90.degree. phase shift for the Q channel. The outputs of the two multiplexers are added to provide the output of the digital modem. The resulting word is then applied to a digital-to-analog converter and subsequently up-converted, filtered, and amplified for transmission.
REFERENCES:
patent: 4213094 (1980-07-01), Wood
patent: 5379242 (1995-01-01), Rose et al.
"Personal Handy Phone System," RCR Standard, Version 1, RCR STD-28, Dec. 20, 1993, pp. 29-31.
Bjorn Bjerede et al., "An Intermediate Frequency Modulator using Direct Digital Synthesis Techniques for Japanese Personal Handy Phone (PHP) and Digital European Cordless Telecommunications (DECT)", pp. 467-471. IEEE Vehicular Technology Conference, Stockholm, Sweden Jun. 1994.
Yoshihiko Akaiwa, "Digital Modulation/Demodulation Techniques for Mobile Radio Communications in Japan," IEICE Transactions, vol. E 74, No. 6 Jun. 1991, pp. 1503-1511.
Dr. Kamilo Feher, Ph.D., "Bandlimited Baseband Systems," Digital Communications Satellite/Earth Station Engineering, 1983 by Prentice-Hall Inc. Englewood Cliffs, NJ 07632, pp. 91-115, 162-174, 200-201.
LMX2411 Baseband Processor For Radio Communications, National Semiconductor Corporation, Sep. 1993, pp. 1-8.
LMX2410 Baseband Processor for Radio Communications, National Semiconductor Corporation, Mar. 1993, pp. 1-16.
Grimm Siegfried H.
National Semiconductor Corporation
LandOfFree
Digital oversampled quadrature 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 oversampled quadrature modulator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital oversampled quadrature modulator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-631651