Spectral emphasis and de-emphasis

Details Spectral emphasis and de-emphasis Spectral emphasis and de-emphasis

Category

H - Electricity

Subcategory

04

Subsubcategory

B

CPC

354/138, 179/2

IPC codes

H04B 1/62 (2006.01) H03G 5/16 (2006.01) H03G 9/02 (2006.01)

Type

Patent

Patent number

CA 1236405

Description

ABSTRACT This invention is advantageous for reducing noise introduced by a transmission medium whose noise level rises with the signal level in the medium. The spectral emphasis circuit of the invention analyzes the spectral composition of an input signal and generates an emphasis control signal which indicates the spectral composition of the input signal and the regions in the frequency spectrum, if any, where the predominant components of the input signal are concentrated. The emphasis control signal is substantially independent of the amplitude of the input signal. The emphasis control signal is also limited by a limitation circuit to a desired bandwidth. The spectral emphasis circuit further comprises means for altering the spectral composition of the input signal by applying to the spectral components of the input signal, emphasis of varying amounts as a function of the emphasis control signal. A delay circuit delays the input signal relative to the emphasis control signal so that the input signal reaches the spectrum altering circuit when the emphasis control signal is available for controlling the emphasis applied. The spectral de-emphasis circuit restores the spectral composition of the input signal. The spectral de-emphasis circuit comprises means for deriving a de-emphasis control signal of limited bandwidth from the emphasis control signal. The de-emphasis circuit further includes means for applying de-emphasis to the spectral components of the altered signal as a function of the de-emphasis control signal. The de-emphasis applied by the restoring means is comple- mentary to the emphasis applied by the spectral emphasis circuit. Since the de-emphasis control signal has a limited bandwidth, the de-emphasis applied can only change slowly. The effect of transmission errors is reduced. The emphasis control signal also has a limited bandwidth. Hence both the emphasis and de-emphasis change slowly, and the system is tolerant of component and timing errors as well.

Application Number

464817

Affiliated with

Also associated with

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