Electronic filter

Claim 2

An electronic filter for filtering an electrical signal, comprising: a filter having a plurality of filter stages coupled in cascade, said filter stages respectively filtering said electrical signal at its respective input according to electrical representations of filter parameters producing a plurality of filter signals; and electronic control means coupled to said filter for altering said electrical representations to vary each of said filter parameters in substantially constant percentage amounts of the value of that one of said filter parameters.

Claim 3

An electronic filter as in claim 1 wherein said filter operates in logarithmic form.

Claim 4

An electronic filter as in claim 2 wherein said at least one of said plurality of filter stages produces its associated one of said plurality of filter sum signals in substantially logarithmic form.

Claim 5

An electronic filter as in claim 1 wherein said electronic control means operates by keeping running totals of the incrementing and decrementing as a function of the polarity of the electrical signal to be filtered and the polarity of at least one of said plurality of filter sum signals, by keeping digital values in logarithmic form representing each of said filter parameters, and by respectively adding the running totals to corresponding ones of said digital values.

Claim 6

An electronic filter as in claim 4 wherein said electronic control means respectively adds the running totals to the corresponding ones of said digital values less frequently than the incrementing and decrementing occurs.

Claim 7

An electronic filter as in claim 1 wherein said electronic control means is responsive to first and second externally derived control signals having respective changing polarities, temporarily stores a series of values representing changing polarities of the first externally derived control signal, and increases and decreases each of said filter parameter in magnitude by a constant amount, the increasing and decreasing respectively depending on whether a corresponding value in said series of values has the same or opposite polarity compared to the polarity of the second externally derived control signal currently.

Claim 8

Electronic signal conversion apparatus comprising: means for temporarily holding a digital value which is to be converted to analog form; first and second capacitors; switch means generally operable for executing selective operations including selectively charging at least one of the first and second capacitors, selectively discharging at least one of the first and second capacitors, and selectively connecting the first and second capacitors so that a redistribution of charge between them occurs; and means responsive to said means for temporarily holding the digital value which is to be converted to analog form, for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charge repeatedly occurs a number of times, wherein the number is a function of the digital value which is to be converted to analog form, so that the voltage across at least one of said capacitors after the operations are executed is an analog which is representative of the digital value which is to be converted to analog form; whereby a digital to analog electronic signal conversion is accomplished.

Claim 9

Electronic signal conversion apparatus comprising: means for temporarily holding a digital value which is to be converted to analog form; first and second capacitors; switch means generally operable for executing selective operations including selectively charging at least one of the first and second capacitors, selectively discharging at least one of the first and second capacitors, and selectively connecting the first and second capacitors so that a redistribution of charge between them occurs; and means responsive to said means for temporarily holding the digital value which is to be converted to analog form, for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charge repeatedly occurs a number of times, wherein the number is a function of the digital value which is to be converted to analog form, so that the voltage across at least one of said capacitors after the operations are executed is an analog which is representative of the digital value which is to be converted to analog form; whereby a digital to analog electronic signal conversion is accomplished.

Claim 10

Electronic signal conversion apparatus as set forth in claim 7 wherein the number of times that the redistribution of charge occurs is substantially proportional to the digital value which is to be converted to analog form, so that the voltage across one of said capacitors after the operations are executed is an analog voltage which is representative of the digital value which is to be converted to analog form.

Claim 11

Electronic signal conversion apparatus as set forth in claim 7 wherein said means for operating said switch means includes means for causing said switch means to perform a sequence of initially charging the first capacitor, and repeatedly both discharging the second capacitor and then connecting the first and second capacitors so that the charge is progressively removed from the first capacitor.

Claim 12

Electronic signal conversion apparatus as set forth in claim 7 wherein the voltage across the first capacitor is the analog voltage to which the digital value is converted and is substantially proportional to a first constant d to a power number N where N is substantially proportional to the number of times that the first and second capacitors are connected.

Claim 13

Electronic signal conversion apparatus as set forth in claim 7 wherein the capacitance of the first capacitor divided by the sum of capacitance of the first and second capacitors is a ratio d representing a base of logarithms of the conversion.

Claim 14

Electronic signal conversion apparatus as set forth in claim 11 wherein the ratio d is between 0.85 and 0.99.

Claim 15

Electronic signal conversion apparatus as set forth in claim 7 wherein the capacitance of the first capacitor is at least ten times the capacitance of the second capacitor.

Claim 16

Electronic signal conversion apparatus comprising: means for temporarily holding a sample of an analog signal which is to be converted to a digital value; first and second capacitors; switch means generally operable for executing selective operations including selectively charging at least one of the first and second capacitors, selectively discharging at least one of the first and second capacitors, and selectively connecting the first and second capacitors so that a redistribution of charge between them occurs; means for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charge repeatedly occurs a number of times until a predetermined electrical condition, involving the sample of the analog signal, occurs, and means for producing a digital value as a function of the number of times the redistribution of charge occurs, so that the digital value so produced when the operations are executed is representative of the digital value of which the sample of the analog signal is converted.

Claim 17

Electronic signal conversion apparatus comprising: means for temporarily holding a sample of an analog signal which is to be converted to a digital value; first and second capacitors; switch means generally operable for executing selective operations including selectively charging at least one of the first and second capacitors, selectively discharging at least one of the first and second capacitors, and selectively connecting the first and second capacitors so that a redistribution of charge between them occurs; means for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charge repeatedly occurs a number of times until a predetermined electrical condition, involving the sample of the analog signal, occurs, and means for producing a digital value as a function of the number of times the redistribution of charge occurs, so that the digital value so produced when the operations are executed is representative of the digital value of which the sample of the analog signal is converted.

Claim 18

Electronic signal conversion apparatus as set forth in claim 14 wherein said means for producing a digital value includes means for incrementing a count of a number proportional to the number of times the selective operation of redistribution charge occurs, and for stopping said incrementing when the predetermined electrical condition occurs.

Claim 19

Electronic signal conversion apparatus as set forth in claim 14 wherein said predetermined electrical condition is based upon the voltage across the first capacitor reaching a particular level.

Claim 20

Electronic signal conversion apparatus as set forth in claim 14, wherein the capacitance of the first capacitor is at least ten times the capacitance of the second capacitor.

Claim 21

Electronic signal conversion apparatus as set forth in claim 14, wherein the capacitance of the first capacitor divided by the sum of capacitance of the first and second capacitors is a ratio d representing a base of logarithms of the conversion.

Claim 22

Electronic signal conversion apparatus as set forth in claim 16, wherein the ratio d is between 0.85 and 0.99.

Claim 23

Electronic signal conversion apparatus comprising: means for temporarily holding a sample of a first analog signal which is to be converted to a first digital value; means for temporarily holding a second digital value which is to be converted to an analog level of a second analog signal; first and second capacitors; switch means generally operable for executing selective operations including selectively charging at least one of the first and second capacitors, selectively discharging at least one of the first and second capacitors, and selectively connecting the first and second capacitors so that a redistribution of charge between them occurs; means for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charge repeatedly occurs a number of times until a predetermined electrical condition, involving the sample of the first analog signal occurs; means for producing a digital value as a function of the number of times the redistribution of charge occurs, so that the digital value so produced when the operations are executed is the first digital value which is representative of the sample of the first analog signal; and means, responsive to said means for temporarily holding the second digital value which is to be converted to an analog level of a second analog signal, for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charged repeatedly occurs a distinct number of times, wherein the distinct number is function of the second digital value which is to be converted to an analog level of the second analog signal, so that the voltage across one of said capacitors after the operations are executed is representative of the analog level of the second analog signal to which the second digital value is converted.

Claim 24

Electronic signal conversion apparatus comprising: means for temporarily holding a sample of a first analog signal which is to be converted to a first digital value; means for temporarily holding a second digital value which is to be converted to an analog level of a second analog signal; first and second capacitors; switch means generally operable for executing selective operations including selectively charging at least one of the first and second capacitors, selectively discharging at least one of the first and second capacitors, and selectively connecting the first and second capacitors so that a redistribution of charge between them occurs; means for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charge repeatedly occurs a number of times until a predetermined electrical condition, involving the sample of the first analog signal occurs; means for producing a digital value as a function of the number of times the redistribution of charge occurs, so that the digital value so produced when the operations are executed is the first digital value which is representative of the sample of the first analog signal; and means, responsive to said means for temporarily holding the second digital value which is to be converted to an analog level of a second analog signal, for operating said switch means to make it perform a sequence of the selective operations among which operations the redistribution of charged repeatedly occurs a distinct number of times, wherein the distinct number is function of the second digital value which is to be converted to an analog level of the second analog signal, so that the voltage across one of said capacitors after the operations are executed is representative of the analog level of the second analog signal to which the second digital value is converted.

Claim 25

A digital-to-analog converter for use with an electric source, comprising: counter means for holding a digital value which is to be converted to analog form; first and second capacitors; first switch means generally operable for charging said first capacitor to a first voltage from the electrical source; third switch neans generally operable for connecting said first capacitor so charged to said second capacitor so that a redistribution of charge occurs and the voltage across said first capacitor is reduced to a predetermined fraction of the first voltage; and means responsive to said counter means for repeatedly operating said second and third switch means alternately so that the voltage across said first capacitor is repeatedly reduced by the predetermined fraction a number of times, the number being represented by the digital value held in said counter means, so that the voltage remaining across said first capacitor after being reduced for that number of times is an analog voltage which is representative of the digital value which is to be converted.

Claim 26

A digital-to-analog converter for use with an electric source, comprising: counter means for holding a digital value which is to be converted to analog form; first and second capacitors; first switch means generally operable for charging said first capacitor to a first voltage from the electrical source; third switch neans generally operable for connecting said first capacitor so charged to said second capacitor so that a redistribution of charge occurs and the voltage across said first capacitor is reduced to a predetermined fraction of the first voltage; and means responsive to said counter means for repeatedly operating said second and third switch means alternately so that the voltage across said first capacitor is repeatedly reduced by the predetermined fraction a number of times, the number being represented by the digital value held in said counter means, so that the voltage remaining across said first capacitor after being reduced for that number of times is an analog voltage which is representative of the digital value which is to be converted.

Claim 31

A hearing aid comprising: microphone means for generating an electrical output from sounds external to a user of the hearing aid; electrically driven receiver means for emitting sound into the ear of the user of the hearing aid; logarithmic analog-to-digital and digital-to-­analog signal conversion means including a plurality of capacitors having respective electrical charges and means for redistributing the charges repeatedly a variable number of times, wherein the variable number relates digital to analog.

Claim 32

A hearing aid comprising: microphone means for generating an electrical output from sounds external to a user of the hearing aid; electrically driven receiver means for emitting sound into the ear of the user of the hearing aid; logarithmic analog-to-digital and digital-to-­analog signal conversion means including a plurality of capacitors having respective electrical charges and means for redistributing the charges repeatedly a variable number of times, wherein the variable number relates digital to analog.

Claim 33

An electronic filter for an electroacoustic system having microphone means for generating an electrical output from external sounds and electrically driven transducer means for emitting sound, some of the sound emitted by the transducer means returning to the microphone means to add a feedback contribution to its electrical output, the electronic filter comprising: means for converting the electrical output of the microphone means to an electrical representation; first means for combining the microphone output so controverted with an adaptive output to produce a combined signal input; electronic filtering means for electronically filtering the combined signal input to produce a filtered signal; and adaptive filter means having electrically stored parameters representing coefficients, including linear control means for altering constant percentage amounts, said linear control means interconnected with said electronic filtering means, said adaptive filter means further including means for electronic processing of the filtered signal relative to the electrically stored coefficients to produce said adaptive output to said first means for combining to substantially offset the feedback contribution in the electrical output of the microphone means n the electroacoustic system.

Claim 34

An electronic filter for an electroacoustic system having microphone means for generating an electrical output from external sounds and electrically driven transducer means for emitting sound, some of the sound emitted by the transducer means returning to the microphone means to add a feedback contribution to its electrical output, the electronic filter comprising: means for converting the electrical output of the microphone means to an electrical representation; first means for combining the microphone output so controverted with an adaptive output to produce a combined signal input; electronic filtering means for electronically filtering the combined signal input to produce a filtered signal; and adaptive filter means having electrically stored parameters representing coefficients, including linear control means for altering constant percentage amounts, said linear control means interconnected with said electronic filtering means, said adaptive filter means further including means for electronic processing of the filtered signal relative to the electrically stored coefficients to produce said adaptive output to said first means for combining to substantially offset the feedback contribution in the electrical output of the microphone means n the electroacoustic system.

Claim 35

An electronic filter as in claim 25, wherein said electrical representation is substantially in logarithmic form, wherein said combined signal is substantially in logarithmic form, wherein said adaptive output is substantially in logarithmic form, wherein said combined signal is substantially in logarithmic form, wherein said filtered signal is substantially in logarithmic form , wherein said coefficients are substantially in logarithmic form, and wherein said adaptive filter means operates in substantially in logarithmic form.