Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via frequency channels
Reexamination Certificate
2006-09-26
2006-09-26
Nguyen, Hanh (Department: 2616)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via frequency channels
C704S208000, C704S228000
Reexamination Certificate
active
07113522
ABSTRACT:
Wideband speech signals must be converted to narrowband speech signals if the transmission medium or the destination terminal is constructed with narrowband constraints. A typical wideband-to-narrowband conversion method is the elimination of frequencies above 3400 Hz using a low pass filter and a down sampler. However, this method produces a muffled speech sound since the resulting narrowband signal has a flat frequency response. Methods and apparatus are presented herein to enhance the acoustic quality of a wideband-to-narrowband converted signal. A bandwidth switching filter is used to emphasize a mid-range frequency portion of the wideband signal so that the resulting narrowband signal has a non-flat frequency spectrum.
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Ananthapadmanabhan Arasanipalai K.
DeJaco Andrew P.
El-Maleh Khaled H.
Brown Charles D.
Chen Alex C.
Nguyen Hanh
QUALCOMM Incorporated
Wadsworth Philip R.
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