Analogue multiplier

Claim 2

Equipment for use in analogue multiplication comprising apparatus to receive first and second input signal components a difference between said first and second input signal components representing a first input signal and the apparatus being arranged to produce in response thereto first, second, third and fourth output signal components such that, the sum of the first and second output components is substantially linearly proportional to the first input component and the sum of the third and fourth output components is substantially linearly proportional to the second input component and, the first output component is related to the second in a controllably variable ratio and the third output component is related to the fourth in substantially the same ratio, means to derive from said first to fourth output components an output signal which is a function of a product of the input signal and a term including the ratio, and control means responsive to said first to fourth output components and to a further input signal to produce a control signal, to which the apparatus is responsive to adjust the ratio such that there is a determinable relationship between said term and the further input signal, whereby a first multiplicand can be represented by the first input signal, a second multiplicand can be represented by said further input signal and the product of the first and second multiplicands can be represented by said output signal.

Claim 3

Equipment as claimed in claim 1, wherein said determinable relationship is substantially independent of variables other than the further input signal and the ratio.

Claim 4

Equipment as claimed in claim 2, wherein said determinable relationship is substantially linear.

Claim 5

Equipment as claimed in claim 1, wherein the sum of the fIrst and second input components is predetermined.

Claim 6

Equipment as claimed in claim 1, wherein the control means is responsive to a difference between the sum of the first and third output components and the sum of the second and fourth output components, the control signal being such as to cause adjustment of the ratio to cause said difference to correspond with the further input signal.

Claim 7

Equipment as claimed in claim 1, wherein means are provided to derive a first signal representative of the sum of the first and third output components and to derive a second signal representative of the sum of the second and fourth output components, the control means being responsive to a difference between said first and second derived signals.

Claim 8

Equipment as claimed in claim 6, wherein the control means comprises superposing means to enable superposition of said further input signal, said first derived signal and said second derived signal, the latter two being superposed in opposition to each other, the control signal being the resultant of said superposed signals.

Claim 9

Equipment as claimed in claim 1, wherein the control means comprises means to derive a third signal representative of the difference between the first and second derived signals, and means to compare said third derived signal with said further input signal, the control signal being representative of a difference between the further input signal and the third derived signal.

Claim 10

Equipment as claimed in claim 1, wherein the output signal is representative of a difference between the sum of the first and fourth output components and the sum of the second and third output components.

Claim 11

Equipment as claimed in claim 9, wherein the means to derive the output signal comprises means to derive a fifth output signal component representing the sum of the first and fourth output components and to derive a sixth output signal component representing the sum of the second and third output components.

Claim 12

Equipment as claimed in claim 1, wherein said apparatus comprises a first device having a first input and a first and second outputs, and a second device having a second input and third and fourth outputs, the first device being arranged to receive said first input component via said first input and to produce the first and second output components which leave the device via the first and second outputs respectively, the second device being arranged to receive the second input component via said second input and to produce the third and fourth output components which leave the device via the third and fourth outputs respectively.

Claim 13

Equipment as claimed in claim 11, including means to connect the first output to the fourth so as to obtain a fifth output signal component representing the sum of the first and fourth output components, and means to connect the second output to the third so as to obtain a sixth output signal component representing the sum of the second and third output components, the output signal being represented by a difference between said fifth and sixth output components.

Claim 14

Equipment as claimed in claim 11, including means to connect the first output to the third so as to derive a first signal representative of the sum of the first and third output components, and means to connect the second output to the fourth so as to derive a second signal representative of the sum of the second and fourth output components, the control means being responsive to a difference between said first and second derived signals.

Claim 15

Equipment as claimed in claim 11, wherein the first device is arranged to divide the first input component to produce the first and second output components, and the second device is arranged to divide the second input component to produce the third and fourth output components.

Claim 16

Equipment as claimed in claim 1, wherein said apparatus comprises a first device having a first input to receive said first input component, first and second elements arranged to deterMine, in response to the control signal, said first and second output components respectively, and first and second outputs by which the first and second output components respectively depart from the device, and comprises also a second device having a second input to receive said second input component, third and fourth elements arranged to determine, in response to the control signal, said third and fourth output components respectively, and third and fourth outputs by which the third and fourth output components respectively depart from the device.

Claim 17

Equipment as claimed in claim 15, wherein the arrangement of the elements is such that variation of the control signal causes corresponding variation in one sense of the first and third output components and corresponding variation in the opposite sense of the second and fourth output components.

Claim 18

Equipment as claimed in claim 15, wherein each element is such that a small variation in control signal causes a corresponding amplified variation in the output component determined by the element.

Claim 19

Apparatus as claimed in claim 1, wherein the signal components are electrical quantities.

Claim 20

Equipment as claimed in claim 18, wherein the first and second input components are electrical currents.

Claim 21

Equipment as claimed in claim 1, comprising an energizing source arranged to produce a predetermined output signal, and means to derive said first and second input components from said predetermined signal such that the sum of the first and second input components is substantially linearly proportional to the predetermined signal.

Claim 22

Equipment as claimed in claimed in claim 20, wherein the means to derive the first and second input components is arranged to divide said predetermined output signal.

Claim 23

Equipment for use in analogue multiplication comprising apparatus to receive first and second input signal components, a difference between said first and second components representing a first input signal and said apparatus being arranged to produce in response to said components first, second, third and fourth output signal components such that, the sum of the first and second output components is substantially linearly proportional to the first input component and the sum of the third and fourth output components is substantially linearly proportional to the second input component, and the first output component is related to the second in a controllably variable ratio and the third output component is related to the fourth in substantially the same ratio, means to derive from said first to fourth output components an output signal which is a function of the product of the input signal and a term including the ratio, and control means responsive to said first to fourth output components and to a further input signal to produce a control signal to which the apparatus is responsive to adjust the ratio such that there is a determinable, substantially linear relationship between said term and the further input signal, and said relationship is substantially independent of variables other than the other input signal and the ratio, whereby a first multiplicand can be represented by the first input signal, a second multiplicand can be represented by said further input signal and the produce of the first and second multiplicands can be represented by said output signal.

Claim 24

Equipment for use in analogue multiplication comprising apparatus to receive first and second input signal components, a difference between said first and second components representing a first input signal and said apparatus being arranged to produce in response to said components first, second, third and fourth output signal components such that, the sum of the first and second output components is substantially linearly proportional to the first input component and the sum of the third and fourth output components is substantially linearly proportional to the second input component, and the first output component is related to the second in a controllably variable ratio and the third output component is related to the fourth in substantially the same ratio, means to derive from said first to fourth output components an output signal which is a function of the product of the input signal and a term including the ratio, and control means responsive to said first to fourth output components and to a further input signal to produce a control signal to which the apparatus is responsive to adjust the ratio such that there is a determinable, substantially linear relationship between said term and the further input signal, and said relationship is substantially independent of variables other than the other input signal and the ratio, whereby a first multiplicand can be represented by the first input signal, a second multiplicand can be represented by said further input signal and the produce of the first and second multiplicands can be represented by said output signal.

Claim 25

Equipment as claimed in claim 22 wherein the control means is responsive to a difference between the sum of the first and third output components and the sum of the second and fourth output components, the control signal being such as to cause adjustment of the ratio to cause said difference to correspond with the further input signal.

Claim 26

Equipment as claimed in claim 22 wherein the output signal is representative of a difference between the sum of the first and fourth output components and the sum of the second and third output components.

Claim 27

Equipment for use in analogue multiplication comprising apparatuS to receive first and second input signal components, a difference between said first and second components representing a first input signal and said apparatus being arranged to produce in response to said components first, second, third and fourth output signal components such that, the sum of the first and second output components is substantially linearly proportional to the first input component and the sum of the third and fourth output components is substantially linearly proportional to the second input component, and the first output component is related to the second in a controllably variable ratio and the third output component is related to the fourth in substantially the same ratio, means to derive from said first to fourth output components an output signal which is representative of a difference between the sum of the first and fourth output components and the sum of the second and third output components, so that the output signal is a function of the product of the input signal and a term including the ratio, and control means arranged to produce a control signal by comparing a further input signal with a difference between the sum of the first and third output components and the sum of the second and fourth output components, the apparatus being responsive to the control signal to adjust the ratio such that there is a determinable relationship between said term and the further input signal, whereby a first multiplicand can be represented by the first input signal, a second multiplicand can be represented by said further input signal and the product of the first and second multiplicands can be represented by said output signal.

Claim 28

Equipment for use in analogue multiplication comprising apparatuS to receive first and second input signal components, a difference between said first and second components representing a first input signal and said apparatus being arranged to produce in response to said components first, second, third and fourth output signal components such that, the sum of the first and second output components is substantially linearly proportional to the first input component and the sum of the third and fourth output components is substantially linearly proportional to the second input component, and the first output component is related to the second in a controllably variable ratio and the third output component is related to the fourth in substantially the same ratio, means to derive from said first to fourth output components an output signal which is representative of a difference between the sum of the first and fourth output components and the sum of the second and third output components, so that the output signal is a function of the product of the input signal and a term including the ratio, and control means arranged to produce a control signal by comparing a further input signal with a difference between the sum of the first and third output components and the sum of the second and fourth output components, the apparatus being responsive to the control signal to adjust the ratio such that there is a determinable relationship between said term and the further input signal, whereby a first multiplicand can be represented by the first input signal, a second multiplicand can be represented by said further input signal and the product of the first and second multiplicands can be represented by said output signal.

Claim 29

Equipment as claimed in claim 25 wherein said relationship is substantially linear and substantially independent of variables other than the further input signal and the ratio.