Abstract An outside loop adaptive delta modulation system. The transmission side of the system includes an envelope detector for detecting the envelope of an analog input signal and a divider for dividing the analog input signal by the envelope signal detected in order to produce a normalized analog signal. An adder is provided for adding the envelope signal and the normalized analog signal and the output of such adder is fed to a nonadaptative delta modulator for modulating the output signal of the adder. The receiving end of the delta modulation system includes a first local demodulator for demodulating an input signal received from the modulator and composed of the envelope of the analog signal and of the normalized signal resulting from the division of such analog signal by the envelope signal, and a low pass filter connected to the output of the first local demodulator for recovering the envelope signal. Such envelope signal corresponds to the envelope signal detected at the input of the transmission side of the delta modulation system. A second local demodulator is also provided for demodulating the normalized signal. The input of such second local demodulator is connected to the input of the receiving system through delay means so as to delay the input of the second local demodulator in such a way that its output is in phase with the output of the above-mentioned low pass filter. The output of the low pass filter and the one of the second local demodulator are fed to a multiplier so as to permit to recover the analog signal. The output of the multiplier is fed to a band-pass filter to eliminate the envelope signal present in the output of the second local demodulator and to filter the high frequency components of the signal which are higher than the audio level.
An outside loop adaptative delta modulator comprising: a. an envelope detector for detecting the envelope of an analog input signal so as to produce an envelope signal; b. a divider for dividing the analog input signal by the envelope signal detected in order to produce a normalized analog signal; c. an adder for adding said envelope signal and said normalized analog signal; and d. a non-adaptative delta modulator connected to the output of said adder for modulating the output signal of said adder.
Claim 2
Dependent Claim
83 words
An outside loop adaptative delta modulator comprising: a. an envelope detector for detecting the envelope of an analog input signal so as to produce an envelope signal; b. a divider for dividing the analog input signal by the envelope signal detected in order to produce a normalized analog signal; c. an adder for adding said envelope signal and said normalized analog signal; and d. a non-adaptative delta modulator connected to the output of said adder for modulating the output signal of said adder.
Claim 3
Dependent Claim
67 words
An outside loop adaptative delta modulator as defined in claim 1, further comprising a first amplifier connected to the output of said envelope detector for amplifying the envelope signal, and a second amplifier connected to the output of said divider for amplifying said normalized signal, the amplification factors of said amplifiers being chosen in function of the desired ratio of the envelope signal over the normalized signal.
Claim 4
Dependent Claim
156 words
A demodulator for use with an outside loop adaptative delta modulator comprising: a. a first local demodulator for demodulating an input signal composed of the envelope of an analog signal and of a normalized signal resulting from the division of said analog signal by said envelope signal; b. a low pass filter connected to the output of said first local demodulator for recovering said envelope signal; c. delay means for delaying said input signal; d. a second local demodulator for demodulating the output signal of said delay means, said second local demodulator producing an output signal in phase with the output signal of said low pass filter; e. a multiplier for multiplying the output signals of said low pass filter and of said second local demodulator to reconstitute the analog signal; f. a band-pass filter connected to the output of said multiplier for eliminating the envelope signal and the frequencies higher than the normal voice frequencies.
Claim 5
Dependent Claim
156 words
A demodulator for use with an outside loop adaptative delta modulator comprising: a. a first local demodulator for demodulating an input signal composed of the envelope of an analog signal and of a normalized signal resulting from the division of said analog signal by said envelope signal; b. a low pass filter connected to the output of said first local demodulator for recovering said envelope signal; c. delay means for delaying said input signal; d. a second local demodulator for demodulating the output signal of said delay means, said second local demodulator producing an output signal in phase with the output signal of said low pass filter; e. a multiplier for multiplying the output signals of said low pass filter and of said second local demodulator to reconstitute the analog signal; f. a band-pass filter connected to the output of said multiplier for eliminating the envelope signal and the frequencies higher than the normal voice frequencies.