Signal compression/expansion apparatus

Signal compression apparatus, comprising:

• n serially-connected voltage controlled amplifier means, each including a voltage controlled variable impedance and a cascade-connected amplifier, at least one of the cascade-connected amplifiers being comprised of a differential amplifier having a pair of outputs and an operational amplifier having a pair of inputs connected to the pair of outputs of said differential amplifier, said voltage controlled variable impedance being coupled to an input of said differential amplifier;
• input means for supplying an input signal to be compressed to a first of said n voltage controlled amplifier means;
• control signal generating means comprised of an adding circuit having one input connected to the nth of said voltage controlled amplifier means and another input connected to be supplied with a reference voltage for producing at an output terminal thereof a control voltage which is proportional to the sum of the output signal of said nth voltage controlled amplifier means and said reference voltage;
• means for supplying said control voltage to the voltage controlled variable impedance in each of said voltage controlled amplifier means;
• and
• means coupled to a predetermined connection point between adjacent voltage controlled amplifier means for producing an exponentially compressed output signal.

Signal expansion apparatus comprising:

• n voltage controlled amplifier means arranged in two groups, one of said groups comprised of k serially-connected voltage controlled amplifier means and the other of said groups comprised of n-k serially-connected voltage controlled amplifier means;
• input means for supplying an input signal having a voltage V.sub.i to a common connection point between said two groups of voltage controlled amplifier means;
• control signal generating means comprised of an adding circuit having one input connected to the output of the nth voltage controlled amplifier means in said group of n-k voltage controlled amplifier means and another input connected to be supplied with a reference voltage V.sub.F for providing at an output terminal thereof a control voltage V.sub.G which is proportional to the sum of the output signal of said nth voltage controlled amplifier means and said reference voltage V.sub.F ;
• means for supplying said control voltage V.sub.G to each of said n voltage controlled amplifier means for determining the gain thereof;
• and
• output means coupled to said group of k voltage controlled amplifier means for producing an expanded output signal having a voltage V.sub.o proportional to ##EQU4##

Apparatus for compressing and expanding a signal, comprising a signal compressing circuit including:

• a signal input terminal for receiving an input signal to be compressed;
• a signal output terminal for producing a compressed output signal;
• at least two serially-connected voltage controlled amplifiers;
• first circuit means for connecting said input terminal to the first one of said serially-connected voltages controlled amplifiers;
• control signal generating means comprised of an adding circuit having one input connected to the last one of said serially-connected voltage controlled amplifiers and another input connected to be supplied with a reference voltage for producing at an output terminal thereof a control voltage which is proportional to the sum of the output signal of the last voltage controlled amplifier and said reference voltage;
• second circuit means for supplying said control voltage to each of said serially-connected voltage controlled amplifiers;
• and
• third circuit means for connecting said signal output terminal to a predetermined connection point between corresponding voltage controlled amplifiers;
• and a signal expanding circuit including:
• a second signal input terminal for receiving a signal to be expanded;
• a second output terminal for producing an expanded output signal;
• first and second voltage controlled amplifiers;
• fourth circuit means for connecting said second signal input terminal to the connection point between said first and second voltage controlled amplifiers;
• second control signal generating means comprised of a second adding circuit having one inut connected to the output of said second voltage controlled amplifier and another input connected to be supplied with another reference voltage for producing at an output terminal thereof a control voltage which is proportional to the sum of the output signal of said second voltage controlled amplifier and said other reference voltage;
• fifth circuit means for supplying said control voltage to each of said first and second voltage controlled amplifiers;
• and
• sixth circuit means for connecting said second signal output terminal to the first voltage controlled amplifier.

Signal compression apparatus, comprising:

• a plurality of serially-connected voltage controlled attenuators, each of said voltage controlled attenuators having a substantially linear gain characteristic over a range of at least 60dB;
• input means for supplying an input signal to be compressed to a first of said voltage controlled attenuators;
• a source for providing a reference signal;
• control signal generating means connected to the last of said voltage controlled attenuators and to said source for combining the output of said last voltage controlled attenuator and said reference signal to produce a control voltage proportional to the sum of said output and said reference signal;
• means for supplying said control voltage to each of said voltage controlled attenuators to determine the gain thereof;
• and
• output means coupled to the output of a predetermined voltage controlled attenuator for producing an output signal that is compressed with respect to said input signal by an exponential factor.

Signal expansion apparatus comprising:

• at least first and second voltage controlled amplifier means, said first voltage controlled amplifier means including a first voltage controlled impedance having a substantially linear characteristic, and said second voltage controlled amplifier means including a second voltage controlled impedance having a linear characteristic connected in cascade with an amplifier of predetermined gain;
• input means for supplying an input signal to be expanded in common to said first and second voltage controlled amplifier means;
• a source for providing a reference signal;
• control signal generating means connected to said second voltage controlled amplifier means and to said source for combining the output of said second voltage controlled amplifier means and said reference signal to produce a control voltage proportional to the sum of said output and said reference signal;
• means for supplying said control voltages to each of said voltage controlled impedances to determine the respective impedance thereof;
• and
• output means coupled to the output of said first voltage controlled amplifier means for producing an output signal that is expanded with respect to said input signal by an exponential factor.