Pulse or digital communications – Receivers – Angle modulation
Reexamination Certificate
1998-03-04
2002-08-27
Chin, Stephen (Department: 2634)
Pulse or digital communications
Receivers
Angle modulation
C375S329000, C329S304000
Reexamination Certificate
active
06442216
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to electronic circuits and more specifically to a digital demodulator and a communication device having said digital demodulator.
BACKGROUND OF THE INVENTION
Thus far, some communication devices such as paging products have exclusively used the superheterodyne receiver as its principal method to recover data from the frequency modulated (FM) signal which is received. The superheterodyne receiver provides a filtered signal at some intermediate frequency (IF) to the demodulator circuit. This requires the use of a traditional FM demodulator such as a frequency discriminator.
With the introduction of zero IF (ZIF) technology into pagers and other communication devices, new technology for a demodulator has to be developed. The zero IF technology generates an I and Q signal which are in phase quadrature. A need thus exists in the art for a digital demodulator which can accept the I and Q signals and optimally decode the data at different baud rates (e.g., 512, 1200, 2400 bits-per-second, etc.) and a communication device which can use such a demodulator. It would also be beneficial if the digital demodulator could also operate in non-zero IF environments such as when using up-mixing techniques to produce an intermediate non-zero IF which is then demodulated.
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Park, John H., An FM Detector fo Low S/N, Apr., 1970, IEEE Transactions in Communications, vol. COM-18, No. 2, pp. 110-118.*
Frerking, Marvin E., Digital Signal Processing in Communication Systems, 1994, Kluwer Academic Publishers, pp. 193-199, 249, 250, 329-333.
McLaughlin Kevin
Nag Manbir
Webster James Rodney
Chin Stephen
Deppe Betsy L.
Dulaney Randi L.
Fuller Andrew S.
Motorola Inc.
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