Dynamic range modifying circuits utilizing variable negative resistance

Claim 2

A circuit for modifying the dynamic range of an input signal, comprising at least one impedance means, input terminals for energising the impedance means in accordance with an input signal, the impedance means comprising at least one linear impedance component providing a component of an output signal which is linear with respect to dynamic range at any given frequency, and means effectively providing a variable impedance which includes an equivalent negative resistance component and which provides a dynamic range modifying component of said output signal within at least one frequency band, said variable impedance being arranged to vary as a function of a signal in the circuit thereby to restrict said at least one frequency band within which said dynamic range modifying component is provided, and output means for deriving said output signal in accordance with either a voltage or a current in the circuit.

Claim 3

A circuit according to claim 1, wherein the relative value of the resistance of the linear impedance component is approximately 3.16 and of the equivalent negative resistance component is approximately 2.16, to provide approximately 10dB modification of dynamic range.

Claim 4

A circuit according to claim 1, wherein the relative value of the resistance of the linear impedance component is approximately 3.16 and of the equivalent negative resistance component is approximately 2.16, to provide approximately 10dB modification of dynamic range.

Claim 5

A circuit according to claim 1, wherein the magnitude of the negative resistance decreases as a function of increasing current in thE circuit.

Claim 6

A circuit according to claim 4, comprising a voltage drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the current through the circuit.

Claim 7

A circuit according to claim 4, comprising a current drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the voltage across the circuit.

Claim 8

A circuit according to claim 1, wherein the variable impedance has a reactive component which decreases as a function of increasing current in the circuit.

Claim 9

A circuit according to claim 7, wherein the reactive component is in shunt with the equivalent negative resistance.

Claim 10

A circuit according to claim 7, comprising a voltage drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the current through the circuit.

Claim 11

A circuit according to claim 7, comprising a current drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the voltage across the circuit.

Claim 12

A circuit according to claim 1, wherein the variable impedance means comprises a negative resistance component shunted by a variable reactance component which has a high impedance relative to the negative resistance component to one side of a turnover frequency and a negligible impedance relative to the negative resistance component to the other side of the turnover frequency, and wherein the reactance varies as the input signal level to the said one side of the turnover frequency varies so as to shift the turnover frequency.

Claim 13

A circuit according to claim 11, wherein the said one and other side of the turnover frequency are above and below the turnover frequency respectively and wherein the turnover frequency rises as the input signal level above the turnover frequency increases.

Claim 14

A circuit according to claim 11, wherein the variable reactance is varied in response to a control signal derived by rectifying and smoothing the voltage across the variable reactance.

Claim 15

A circuit according to claim 11, wherein the variable reactance has the characteristics of a variable inductor.

Claim 16

A circuit according to claim 1, wherein the magnitude of the negative resistance component increases as a function of increasing current in the circuit.

Claim 17

A circuit according to claim 15, comprising a current drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the voltages across the impedance means.

Claim 18

A circuit according to claim 15, comprising a voltage drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the current through the circuit.

Claim 19

A circuit according to claim 1, wherein the variable impedance has a reactive component which increases as a function of increasing current in the circuit.

Claim 20

A circuit according to claim 18, wherein the reactive component is in shunt with the equivalent negative resistance.

Claim 21

A circuit according to claim 18, comprising a current drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the voltages across the impedance means.

Claim 22

A circuit according to claim 18, comprising a voltage drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the current through the circuit.

Claim 23

A circuit according to claim 1, wherein the variable impedance means comprises a negative resistance component shunted by a variable reactance component which has a negligible impedance relative to the negative resistance component to one side of a turnover frequency and a high impedance relative to the negative resistance component to the other side of the turnover frequency, and wherein the reactance varies as the input signal level to the said one side of the turnover frequeNcy varies so as to shift the turnover frequency.

Claim 24

A circuit according to claim 22, wherein the said one and other side of the turnover frequency are above and below the turnover frequency respectively and wherein the turnover frequency rises as the input signal level above the turnover frequency increases.

Claim 25

A circuit according to claim 22, wherein the variable reactance is varied in response to a control signal derived by rectifying and smoothing a signal derived from the current through the variable reactance.

Claim 26

A circuit according to claim 22, wherein the variable reactance has the characteristics of a variable capacitance.

Claim 27

A circuit according to claim 1, wherein the variable impedance means comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce into the current path between the two terminals a voltage of such polarity as to create the characteristics of an impedance which includes the said negative resistance component.

Claim 28

A circuit according to claim 26, wherein the frequency selective circuit includes a variable filter.

Claim 29

A circuit according to claim 26, wherein the frequency selective circuit comprises a plurality of signal paths to provide path output signals, and means for combining the path output signals to provide the said introduced voltage, each signal path comprising a filter defining a frequency band individual to the path and limiting means.

Claim 30

A circuit for modifying the dynamic range of an input signal, comprising first and second impedance means connected in a series combination, input terminals for energising the combination in accordance with an input signal, the first means comprising at least one resistor and providing characteristics which are linear with respect to dynamic range at any given frequency, the second means effectively providing a variable impedance arranged to vary as a function of a signal in the combination, and output means for deriving an output signal in accordance with a voltage or a current in the combination, and wherein the second means comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce a voltage into the current path between the two terminals, and wherein the frequency selective circuit comprises a series combination of two filters arranged to develop the said introduced voltage, one filter being a filter having fixed high pass characteristics and the other having variable high pass characteristics, the variable characteristics so varying as to restrict the said introduced voltage to a small fractional part of the voltage across the said first means at maximum signal level.

Claim 31

A circuit for modifying the dynamic range of an input signal, comprising first and second impedance means connected in a series combination, input terminals for energising the combination in accordance with an input signal, the first means comprising at least one resistor and providing characteristics which are linear with respect to dynamic range at any given frequency, the second means effectively providing a variable impedance arranged to vary as a function of a signal in the combination, and output means for deriving an output signal in accordance with a voltage or a current in the combination, and wherein the second means comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce a voltage into the current path between the two terminals, and wherein the frequency selective circuit comprises a series combination of two filters arranged to develop the said introduced voltage, one filter being a filter having fixed high pass characteristics and the other having variable high pass characteristics, the variable characteristics so varying as to restrict the said introduced voltage to a small fractional part of the voltage across the said first means at maximum signal level.

Claim 32

A circuit according to claim 29, wherein the voltage introduced into the current path is of such polarity as to give the second means the characteristics of an impedance including positive resistance.

Claim 33

A circuit according to claim 30, wherein the frequency selective circuit is operative above about 1.5 kHz and wherein the relative value of the resistance of the first means is 1.00 and of the resistive component of the second means is approximately 2.16, to provide approximately 10dB modification of dynamic range.

Claim 34

A circuit according to claim 30, comprising a current drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the voltage across the combination.

Claim 35

A circuit according to claim 30, comprising a voltage drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the current through the combination.

Claim 36

A circuit for modifying the dynamic range of an input signal, comprising first and second impedance means connected in a series combination, input terminals for energising the combination in accorDance with an input signal, the first means comprising at least one resistor and providing characteristics which are linear with respect to dynamic range at any given frequency, the second means effectively providing a variable impedance arranged to vary as a function of a signal in the combination, and output means for deriving an output signal in accordance with a voltage or a current in the combination, and wherein the second means comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce a voltage into the current path between the two terminals, and wherein the frequency selective circuit comprises a variable filter whose characteristics so vary as to restrict the said introduced voltage to a small fractional part of the voltage across the said first means at maximum signal level, and instantaneous limiting means connected to suppress overshoots of said introduced voltage above said small fractional part.

Claim 37

A circuit for modifying the dynamic range of an input signal, comprising first and second impedance means connected in a series combination, input terminals for energising the combination in accorDance with an input signal, the first means comprising at least one resistor and providing characteristics which are linear with respect to dynamic range at any given frequency, the second means effectively providing a variable impedance arranged to vary as a function of a signal in the combination, and output means for deriving an output signal in accordance with a voltage or a current in the combination, and wherein the second means comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce a voltage into the current path between the two terminals, and wherein the frequency selective circuit comprises a variable filter whose characteristics so vary as to restrict the said introduced voltage to a small fractional part of the voltage across the said first means at maximum signal level, and instantaneous limiting means connected to suppress overshoots of said introduced voltage above said small fractional part.

Claim 38

A circuit for modifying the dynamic range of an input signal, comprising first and second impedance means connected in a series combination, input terminals for energising the combination in accordance with an input signal, the first means comprising at least one resistor and providing characteristics which are linear with respect to dynamic range at any given frequency, the second means effectively providing a variable impedance arranged to vary as a function of signals in the combination, and output means for deriving an output signal in accordance with a voltage or a current in the combination, and wherein the second network comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce a voltage into the current path between the two terminals, and wherein the frequency selective circuit comprises a plurality of signal paths arranged to provide path output signals, and means for combining the path output signals to provide the said introduced voltage, each signal path comprising a filter defining a frequency band individual to the path and limiting means.

Claim 39

A circuit for modifying the dynamic range of an input signal, comprising first and second impedance means connected in a series combination, input terminals for energising the combination in accordance with an input signal, the first means comprising at least one resistor and providing characteristics which are linear with respect to dynamic range at any given frequency, the second means effectively providing a variable impedance arranged to vary as a function of signals in the combination, and output means for deriving an output signal in accordance with a voltage or a current in the combination, and wherein the second network comprises two terminals, a current path extending between the two terminals, and a frequency selective circuit responsive to the current flowing in the current path to introduce a voltage into the current path between the two terminals, and wherein the frequency selective circuit comprises a plurality of signal paths arranged to provide path output signals, and means for combining the path output signals to provide the said introduced voltage, each signal path comprising a filter defining a frequency band individual to the path and limiting means.

Claim 40

A circuit according to claim 35, wherein the voltage introduced into the current path is of such polarity as to give the second means the characteristics of an impedance including positive resistance.

Claim 41

A circuit according to claim 36, wherein the paths of the frequency selective circuit pertain to four audio frequency bands and wherein the circuit provides a dynamic range modification of approximately 10dB.

Claim 42

A circuit according to claim 36, comprising a current drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the voltage across the combination.

Claim 43

A circuit according to claim 36, comprising a voltage drive source connected to the input terminals and wherein the output means derive an output signal in accordance with the current through the combination.

Claim 44

In a circuit wherein the dynamic range of a signal is modified within a restricted frequency band by the action of a frequency selective circuit which is responsive to signal components exceeding a selected value within said frequency band to narrow said frequency band to exclude said components from dynamic range modification, the improvement wherein: said frequency selective circuit comprises a variable equivalent negative resistance whose variation in response to said components effects said narrowing of said frequency band.

Claim 45

In a circuit wherein the dynamic range of a signal is modified within a restricted frequency band by the action of a frequency selective circuit which is responsive to signal components exceeding a selected value within said frequency band to narrow said frequency band to exclude said components from dynamic range modification, the improvement wherein: said frequency selective circuit comprises a variable equivalent negative resistance whose variation in response to said components effects said narrowing of said frequency band.