Signal processing apparatus including deemphasis processing

• US 5,194,998 A
• Filed: 10/05/1989
• Issued: 03/16/1993
• Est. Priority Date: 10/11/1988
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kawasaki, Somei
• Primary Examiner(s): Levy, Stuart S.
• Assistant Examiner(s): EVANS, JEFFERSON A
• Application Number:
  US07/417,240
• Time in Patent Office: 1,258 Days
• Field of Search: 360/65, 360/67, 360/10.1, 360/19.1, 360/30, 360/32, 360/33.1, 358/320, 358/328, 358/336, 358/337, 358/340, 358/335
• US Class Current: 360/65
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 5/035 Equalising
• CPC Class Codes: H04N 5/923 using preemphasis of the signal before modulation and deemphasis of the signal after demodulation volume compression or expansion in amplifiers in general H03G7/00

Abstract

A signal processing apparatus includes a deemphasis processor, which is arranged to receive a signal which has been emphasis-processed on the basis of a predetermined emphasis characteristic, to separate only a signal of a predetermined frequency band from the received signal, to effect deemphasis-processing of the separated signal on the basis of a deemphasis characteristic corresponding to said emphasis characteristic and then to effect phase-compensation of the signal, thereby restoring an original signal corresponding to the received signal. This apparatus enables stable restoring processing, without being subjected to adverse influence by a noise component.

Claims

1. A signal processing apparatus in which a first frequency-modulated signal, which has been formed by applying an emphasis-processing to a signal on the basis of a predetermined emphasis characteristic at the time of sending out said signal and then frequency-modulating said emphasis-processed signal in a first deviation, and a second frequency-modulated signal, which has been formed by frequency-modulating the emphasis-processed signal in a second deviation different from said first deviation, are selectively received and an original signal is restored from said received first or second frequency-modulated signal, comprising:

(A) frequency demodulating means for demodulating the received first or second frequency-modulated signal and outputting the demodulated signal;

(B) separating means for separating and outputting a signal of a predetermined frequency band from the signal outputted from said frequency demodulating means;

(C) first phase compensating means arranged to input the signal outputted from said separating means and to apply phase compensating processing to said inputted signal and then output the phase-compensated signal in the case where the inputted signal is a signal which has been separated by said separating means from the demodulated signal demodulated from said first frequency-modulated signal by said frequency-modulating means or to output the signal, without applying the phase compensating processing to said inputted signal, in the case where the inputted signal is a signal which has been separated by said separating means from the demodulated signal demodulated from said second frequency-modulated signal by said frequency demodulating means;

D) deemphasis means arranged to input the signal outputted from said first phase compensating means, to apply deemphasis-processing to the inputted signal on the basis of a predetermined deemphasis characteristic corresponding to said emphasis characteristic, and to output the deemphasis-processed signal; and

(E) second phase compensating means arranged to input the signal outputted from said deemphasis means, and to apply the phase compensating processing to said inputted signal and output the phase compensated signal in the case where the inputted signal is a signal which has been separated by said separating means from the signal which is demodulated from said second frequency-modulated signal by said frequency modulating means or to output the inputted signal, without applying the phase compensating processing to said inputted signal, in the case where said inputted signal is a signal which has been separated by said separating means from the signal which is demodulated from said first frequency-modulated signal by said frequency-modulating means.

2. An apparatus according to claim 1, wherein said second deviation is wider than said first deviation.