Telecommunications – Receiver or analog modulated signal frequency converter – Noise or interference elimination
Reexamination Certificate
2001-03-28
2003-12-02
Urban, Edward F. (Department: 2685)
Telecommunications
Receiver or analog modulated signal frequency converter
Noise or interference elimination
C455S306000, C455S200100, C455S339000, C375S347000, C375S349000, C375S350000
Reexamination Certificate
active
06658245
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to receivers and more specifically to radio receivers having a dynamic bandwidth filter and method therefor.
RELATED ART
In broadband FM (frequency modulation) broadcasting systems, one of the most important features of the system is that the bandwidth of the FM modulated signal (radio signal) changes with the envelope of the modulating signal (audio signal). However, in traditional FM receivers, the bandwidth of the intermediate frequency stage is fixed (about 100 KHz, single sided band). When the received FM signal strength is weak, it may become difficult to have good stereo separation due to excessive noise effect. Also, interference from the adjacent station (200 KHz away from the desired station) will degrade the signal quality or even completely replace the desired station signal if the interfering signal is very strong, due to the capture effect of nonlinear demodulation process. Therefore, it would be desirable to have an FM receiver that can dynamically adjust its IF (intermediate frequency) bandwidth according to signal reception conditions.
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International Search Report.
P.O. Vaidyanathan, “Multirate Systems and Filter Banks”, 1993 Prentice Hall P T R, Section 4.6, Chapter 4, pp. 151-166.
Li Junsong
Seaberg Charles E.
Su Jie
Hill Daniel D.
King Robert L.
Motorola Inc.
Nguyen Simon
Urban Edward F.
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