Negative impedance repeater

Claim 2

A negative impedance repeater for use with non-loaded transmission facilities comprising in combination, a gain unit having a substantially constant image impedance, impedance corrector means shunted across the transmission facility for correcting the impedance thereof to match the image impedance of the gain unit, said impedance corrector means including amplifier means having feedback paths at least one of which is frequency dependent for establishing a crossover frequency and lowering the apparent impedance of the facility below said crossover frequency and increasing the apparent impedance of the facility above said crossover frequency thereby to yield a corrected impedance having a characteristic attenuation vs. frequency slope, said gain unit including means for providing a gain vs. frequency characteristic which complements the corrected attenuation vs. frequency slope.

Claim 3

The negative impedance repeater as set forth in claim 1 wherein the gain unit comprises a series negative impedance element interposed in series with the transmission facility, a shunt negative impedance element arranged in bridged-T configuration with the series element, each of the shunt and series elements including feedback amplifiers for establishing the magnitudes of the negative impedances of said elements to achieve a substantially constant image impedance, the series element feedback paths including means for increasing the magnitude of the negative impedance of the series element with increasing frequency, the shunt element feedback paths including means for decreasing the magnitude of the negative impedance of the shunt element with increasing frequency to complement the increase in magnitude of the series element impedance, whereby the gain unit maintains a substantially constant image impedance while providing a gain which increases as a function of frequency.

Claim 4

A negative impedance repeater for use in non-loaded audio frequency transmission facilites comprising in combination, a bridged-T series-shunt gain unit having a substantially constant image impedance across the audio frequency band, active impedance corrector means bridged across the transmission facility for correcting the impedance of the facility to match the image impedance of the gain unit, the impedance corrector means including feedback amplifier means having feedback impedances for causing said active impedance corrector means to shunt the transmission facility with a resistance varying from a positive to a negative value as a function of frequency in series with a frequency dependent negative capacitance thereby to raise the apparent impedance of the facility over a portion of the audio frequency band, said bridged-T sereis-shunt gain unit including gain setting means for establishing the gain of said gain unit, the increased corrected impedance of the facility serving to allow an increased gain for said gain unit while maintaining stable operation within said transmission facility.

Claim 5

A negative impedance repeater for use in non-loaded audio frequency transmission facilites comprising in combination, a bridged-T series-shunt gain unit having a substantially constant image impedance across the audio frequency band, active impedance corrector means bridged across the transmission facility for correcting the impedance of the facility to match the image impedance of the gain unit, the impedance corrector means including feedback amplifier means having feedback impedances for causing said active impedance corrector means to shunt the transmission facility with a resistance varying from a positive to a negative value as a function of frequency in series with a frequency dependent negative capacitance thereby to raise the apparent impedance of the facility over a portion of the audio frequency band, said bridged-T sereis-shunt gain unit including gain setting means for establishing the gain of said gain unit, the increased corrected impedance of the facility serving to allow an increased gain for said gain unit while maintaining stable operation within said transmission facility.

Claim 6

The negative impedance repeater as set forth in claim 3 wherein the gain unit includes overall feedback means for varying the amount of gain in response to variations in the corrected impedance in a direction oposing oscillation, whereby variations in the characteristic of the transmission facility serve to drive the gain unit in a direction toward stability.

Claim 7

The negative impedance repeater as set forth in claim 3 wherein the impedance corrector includes overall feedbacK means for varying the impedance of the corrector unit in response to changes in impedance in the transmission facility, whereby the corrected impedance of the transmission facility is maintained near the image impedance of the gain unit.

Claim 8

An impedance corrector for use in a non-loaded transmission facility comprising in combination, an amplifier arranged to derive an input signal from across the transmission facility, said amplifier having positive and negative feedback paths, at least one of the feedback paths including a frequency dependent impedance, means for coupling the amplifier output signal across the transmission facility to shunt said facility with a frequency dependent impedance comprising a resistance in series with a negative capacitance, means for adjusting at least one of said feedback paths for selecting a gain crossover frequency above which the frequency dependent impedance serves to increase the apparent impedance of the facility, whereby the apparent impedance of the transmission facility is increased to provide apparent gain above said crossover frequency.

Claim 9

An impedance corrector for use in a non-loaded transmission facility comprising in combination, an amplifier arranged to derive an input signal from across the transmission facility, said amplifier having positive and negative feedback paths, at least one of the feedback paths including a frequency dependent impedance, means for coupling the amplifier output signal across the transmission facility to shunt said facility with a frequency dependent impedance comprising a resistance in series with a negative capacitance, means for adjusting at least one of said feedback paths for selecting a gain crossover frequency above which the frequency dependent impedance serves to increase the apparent impedance of the facility, whereby the apparent impedance of the transmission facility is increased to provide apparent gain above said crossover frequency.

Claim 10

An impedance corrector for use in a non-loaded transmission facility comprising in combination, an input transformer having a primary shunted across said transmission facility, a differential amplifier having one of its inputs coupled to the secondary of the input transformer, the amplifier output coupled to the primary of an output transformer, the output transformer having a secondary shunted across the transmission facility, the amplifier having a positive feedback path and a negative feedback path, at least one of said feedback paths including a reactance for causing the gain of the amplifier to increase with increasing frequency, at least one of said feedback paths having an adjustable impedance for establishing the basic gain of said amplifier, whereby the shunted impedance corrector appears to the transmission facility as a resistance having a frequency dependent characteristic varying from a positive to a negative value in series with a negative capacitance having a frequency dependent characteristic.

Claim 11

An impedance corrector for use in a non-loaded transmission facility comprising in combination, an input transformer having a primary shunted across said transmission facility, a differential amplifier having one of its inputs coupled to the secondary of the input transformer, the amplifier output coupled to the primary of an output transformer, the output transformer having a secondary shunted across the transmission facility, the amplifier having a positive feedback path and a negative feedback path, at least one of said feedback paths including a reactance for causing the gain of the amplifier to increase with increasing frequency, at least one of said feedback paths having an adjustable impedance for establishing the basic gain of said amplifier, whereby the shunted impedance corrector appears to the transmission facility as a resistance having a frequency dependent characteristic varying from a positive to a negative value in series with a negative capacitance having a frequency dependent characteristic.

Claim 12

The impedance corrector as set forth in claim 7 wherein said impedance corrector is adapted to be used with a gain unit having a substantially constant image impedance, said impedance corrector including means for varying the slope of the frequency dependent resistance and capacitance characteristics, whereby the impedance corrector may be adjusted to correct the impedance of the transmission facility to match the image impedance of the gain unit.

Claim 13

The impedance corrector as set forth in claim 7 including means in one of the feedback paths for increasing the amplifier gain above said basic gain to increase the magnitude of the corrected impedance thereby to deliver additional gain to the transmission facility.

Claim 14

A two port negative impedance repeater adapted to be interposed in a transmission facility to provide bidirectional gain thereto, the portion of the transmission facility coupled to at least one of said ports having characteristic impedance and attenuation characteristics which are frequency dependent, comprising in combination, a bridged-T series-shunt negative impedance gain unit having a substantially constant image impedance, impedance corrector means coupled in shunting relationship across the gain unit at the port having the frequency dependent transmission facility coupled thereto, the impedance corrector means comprising feedback amplifier means including a feedback reactance for varying the impedance of said corrector over a predetermined frequency range from a first impedance comprising a positive resistor in series with a negative capacitor to a second impedance comprising a negative resistor in series with a negative capacitor, said feedback amplifier further including feedback adjusting means for adjusting the magnitudes of said frequency variable resistor and capacitor over said predetermined frequency range to correct the frequency dependent iMpedance of the transmission facility to match the image impedance of the gain unit.

Claim 15

A two port negative impedance repeater adapted to be interposed in a transmission facility to provide bidirectional gain thereto, the portion of the transmission facility coupled to at least one of said ports having characteristic impedance and attenuation characteristics which are frequency dependent, comprising in combination, a bridged-T series-shunt negative impedance gain unit having a substantially constant image impedance, impedance corrector means coupled in shunting relationship across the gain unit at the port having the frequency dependent transmission facility coupled thereto, the impedance corrector means comprising feedback amplifier means including a feedback reactance for varying the impedance of said corrector over a predetermined frequency range from a first impedance comprising a positive resistor in series with a negative capacitor to a second impedance comprising a negative resistor in series with a negative capacitor, said feedback amplifier further including feedback adjusting means for adjusting the magnitudes of said frequency variable resistor and capacitor over said predetermined frequency range to correct the frequency dependent iMpedance of the transmission facility to match the image impedance of the gain unit.

Claim 16

The negative impedance repeater as set forth in claim 10 wherein one of the ports has an impedance corrector bridged across the transmission facility coupled thereto, the other of said ports adapted to be coupled directly to a transmission facility having a frequency invariant characteristic impedance approximately equal to the image impedance of the gain unit.

Claim 17

The negative impedance repeater as set forth in claim 10 wherein the gain unit includes means for increasing the gain thereof as a function of increasing frequency, thereby to compensate the frequency dependent attenuation characteristic of the transmission facility.

Claim 18

A negative impedance repeater for use with a non-loaded transmission facility and operable over a predetermined operating frequency range, comprising in combination, a gain unit including a negative impedance series element and a negative impedance shunt element coupled in bridged-T configuration to the transmission facility, impedance corrector means shunted across the transmission facility intermediate the gain unit and the non-loaded transmission facility for providing a correcting impedance shunting the transmission facility, the parallel combination of the correcting impedance and the transmission facility impedance serving to provide a corrected impedance to the gain unit, the impedance corrector means including first amplifier means having positive and negative feedback paths for establishing the gain of the amplifier and thereby the magnitude of the correcting impedance, a reactance interposed in one of said feedback paths for causing the gain of the amplifier to increase with increasing frequency, means interposed in the feedback paths for adjusting the amplifier gain over a predetermined frequency range to produce a correcting impedance having a frequency dependent resistive component which is positive below an intermediate frequency and negative above said intermediate frequency and a frequency dependent negative capacitive component, said adjusting means serving to adjust the magnitude of the resistive and capacitive components to provide a corrected impedance which is substanially constant at a preselected value over said operating frequency range, the series element including second amplifier means having positive and negative feedback paths for establishing the magnitude of the negative impedance thereof, the shunt element including third amplifier means having positive and negative feedback paths for establishing the magnitude of the negative impedance thereof, the feedback paths of the second and third amplifier means arranged to cause the magnitudes of the negative impedances of the series and shunt elements to provide an image impedance which is fixed at the preselected corrected value, each of the impedance corrector means, the series element and the shunt element including overall feedback means for adjusting the gains of the associated amplifiers in a direction to maintain stability in the transmission facility, whereby the negative impedance repeater may be adjusted to provide gain to the transmissiion facility while maintaining stable operation of said facility.

Claim 19

A negative impedance repeater for use with a non-loaded transmission facility and operable over a predetermined operating frequency range, comprising in combination, a gain unit including a negative impedance series element and a negative impedance shunt element coupled in bridged-T configuration to the transmission facility, impedance corrector means shunted across the transmission facility intermediate the gain unit and the non-loaded transmission facility for providing a correcting impedance shunting the transmission facility, the parallel combination of the correcting impedance and the transmission facility impedance serving to provide a corrected impedance to the gain unit, the impedance corrector means including first amplifier means having positive and negative feedback paths for establishing the gain of the amplifier and thereby the magnitude of the correcting impedance, a reactance interposed in one of said feedback paths for causing the gain of the amplifier to increase with increasing frequency, means interposed in the feedback paths for adjusting the amplifier gain over a predetermined frequency range to produce a correcting impedance having a frequency dependent resistive component which is positive below an intermediate frequency and negative above said intermediate frequency and a frequency dependent negative capacitive component, said adjusting means serving to adjust the magnitude of the resistive and capacitive components to provide a corrected impedance which is substanially constant at a preselected value over said operating frequency range, the series element including second amplifier means having positive and negative feedback paths for establishing the magnitude of the negative impedance thereof, the shunt element including third amplifier means having positive and negative feedback paths for establishing the magnitude of the negative impedance thereof, the feedback paths of the second and third amplifier means arranged to cause the magnitudes of the negative impedances of the series and shunt elements to provide an image impedance which is fixed at the preselected corrected value, each of the impedance corrector means, the series element and the shunt element including overall feedback means for adjusting the gains of the associated amplifiers in a direction to maintain stability in the transmission facility, whereby the negative impedance repeater may be adjusted to provide gain to the transmissiion facility while maintaining stable operation of said facility.

Claim 20

The negative impedance repeater as set forth in claim 13 wherein the impedance corrector means serves to modify the characteristic of the transmission facility to provide a characteristic attenuation vs. frequency slope, a second reactance in at least one of the feedback paths of the second amplifier for causing the magnitude of the negative impedance of the series element to increase with increasing frequency, a third reactance in at least one of the feedback paths of the third amplifier for causing the magnitude of the negative impedance of the shunt element to decrease with frequency, the values of the second and third reactances selected to cause the magnitude of the negative impedance of the series element to inversely track the magnitude of the negAtive impedance of the shunt element with frequency, thereby to provide a gain which increases as a function of frequency while maintaining said fixed image impedance.

Claim 21

The negative impedance repeater as set forth in claim 14 further including high frequency cut off feedback means associated with each of the first, second and third amplifier means for reducing the gains of said amplifiers at frequencies higher than the operating frequency range, thereby to enhance the stability of the repeater.

Claim 22

A two port negative impedance repeater operable within a predetermined frequency band and adapted to be interposed in a transmission facility for providing bidirectional gain thereto, the segment of the transmission facility coupled to at least one of the ports having an impedance which is frequency dependent, comprising in combination, impedance corrector means bridged across the port to which the frequency dependent transmission facility is coupled, the impedance corrector means including a first input transformer having a primary bridged across the last mentioned port and a first output transformer having a secondary also bridged across said port, a first amplifier having an input coupled to the secondary of the first input transformer and an output coupled to the primary of the first output transformer, the first amplifier having positive and negative feedback paths, a reactance in one of the feedback paths for providing an amplifier gain dependent upon frequency, means in one of said feedback paths for establishing a basic amplifier gain, a gain unit comprising a negative impedance series element and a negative impedance shunt element, the negative impedance series element including second input transformer means for coupling the series element in series with the transmission facility and providing internal terminals for bridging of the shunt element, the series element including a second amplifier coupled to the second transformer means, said second amplifier including positive and negative feedback paths, at least one of said second amplifier feedback paths being adjustable for establishing the gain of the series element, the series element further including a reactance common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, the shunt element including third transformer means having a primary bridged across said terminals for coupling the shunt element to the transmission facility, the shunt element also including a third amplifier coupled to the secondary of the third transformer means, the third amplifier including positive and negative feedback paths, at least one of said third amplifier feedback paths including a variable impedance for adjusting the basic gain of the shunt element, the shunt element further including a reactance common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, whereby enhanced gain is provided to the transmission facility while maintaining stable operation.

Claim 23

A two port negative impedance repeater operable within a predetermined frequency band and adapted to be interposed in a transmission facility for providing bidirectional gain thereto, the segment of the transmission facility coupled to at least one of the ports having an impedance which is frequency dependent, comprising in combination, impedance corrector means bridged across the port to which the frequency dependent transmission facility is coupled, the impedance corrector means including a first input transformer having a primary bridged across the last mentioned port and a first output transformer having a secondary also bridged across said port, a first amplifier having an input coupled to the secondary of the first input transformer and an output coupled to the primary of the first output transformer, the first amplifier having positive and negative feedback paths, a reactance in one of the feedback paths for providing an amplifier gain dependent upon frequency, means in one of said feedback paths for establishing a basic amplifier gain, a gain unit comprising a negative impedance series element and a negative impedance shunt element, the negative impedance series element including second input transformer means for coupling the series element in series with the transmission facility and providing internal terminals for bridging of the shunt element, the series element including a second amplifier coupled to the second transformer means, said second amplifier including positive and negative feedback paths, at least one of said second amplifier feedback paths being adjustable for establishing the gain of the series element, the series element further including a reactance common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, the shunt element including third transformer means having a primary bridged across said terminals for coupling the shunt element to the transmission facility, the shunt element also including a third amplifier coupled to the secondary of the third transformer means, the third amplifier including positive and negative feedback paths, at least one of said third amplifier feedback paths including a variable impedance for adjusting the basic gain of the shunt element, the shunt element further including a reactance common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, whereby enhanced gain is provided to the transmission facility while maintaining stable operation.

Claim 24

A two port negative impedance repeater operable within a predetermined frequency band and adapted to be interposed in a transmission facility for providing bidirectional gain thereto, the segment of the transmission facility coupled to at least one of the ports having an impedance which is frequency dependent, comprising in combination, impedance corrector means bridged across the port to which the frequency dependent transmission facility is coupled, the impedance corrector including a first input transformer having a primary bridged across the last mentioned port and a first output transformer having a secondary also bridged across said port, a first amplifier having an input coupled to the secondary of the first input transformer and an output coupled to the primary of the first output transformer, the first amplifier having a positive feedback path and a negative feedback path, an inductor in the negative feedback path for providing an amplifier gain depeNdent upon frequency, means in one of said feedback paths for establishing a basic amplifier gain, a gain unit comprising a negative impedance series element and a negative impedance shunt element, the negative impedance series element including a second input transformer and a second output transformer having windings coupled in series with the transmission facility and providing internal terminals for bridging of the shunt element, the series element including a second amplifier having an input coupled to the secondary of the second input transformer, said second amplifier including a positive feedback path and a negative feedback path, at least one of said feedback paths being adjustable for establishing the gain of the series element, the series element further including a capacitor common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, the shunt element including a third input transformer having a primary bridged across said terminals and a third output transformer having a secondary bridged across said terminals, the shunt element also including a third amplifier having an input coupled to the secondary of the third input transformer and an output coupled to the primary of the third output transformer, the third amplifier including a positive feedback path and a negative feedback path, at least one of said feedback paths including a variable impedance for adjusting the basic gain of the shunt element, the shunt element further including a capacitor common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, whereby enhanced gain is provided to the transmission facility while maintaining stable operation.

Claim 25

A two port negative impedance repeater operable within a predetermined frequency band and adapted to be interposed in a transmission facility for providing bidirectional gain thereto, the segment of the transmission facility coupled to at least one of the ports having an impedance which is frequency dependent, comprising in combination, impedance corrector means bridged across the port to which the frequency dependent transmission facility is coupled, the impedance corrector including a first input transformer having a primary bridged across the last mentioned port and a first output transformer having a secondary also bridged across said port, a first amplifier having an input coupled to the secondary of the first input transformer and an output coupled to the primary of the first output transformer, the first amplifier having a positive feedback path and a negative feedback path, an inductor in the negative feedback path for providing an amplifier gain depeNdent upon frequency, means in one of said feedback paths for establishing a basic amplifier gain, a gain unit comprising a negative impedance series element and a negative impedance shunt element, the negative impedance series element including a second input transformer and a second output transformer having windings coupled in series with the transmission facility and providing internal terminals for bridging of the shunt element, the series element including a second amplifier having an input coupled to the secondary of the second input transformer, said second amplifier including a positive feedback path and a negative feedback path, at least one of said feedback paths being adjustable for establishing the gain of the series element, the series element further including a capacitor common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, the shunt element including a third input transformer having a primary bridged across said terminals and a third output transformer having a secondary bridged across said terminals, the shunt element also including a third amplifier having an input coupled to the secondary of the third input transformer and an output coupled to the primary of the third output transformer, the third amplifier including a positive feedback path and a negative feedback path, at least one of said feedback paths including a variable impedance for adjusting the basic gain of the shunt element, the shunt element further including a capacitor common to the positive and negative feedback paths for providing a gain which increases as a function of frequency, whereby enhanced gain is provided to the transmission facility while maintaining stable operation.

Claim 26

The negative impedance repeater as set forth in claim 17 wherein the impedance corrector means includes an overall feedback path including the impedance of the transmission facility, further including a capacitor selectively interposable into said overall feedback path for providing additional gain to the first amplifier at the higher frequencies in the predetermined frequency band.

Claim 27

The negative impedance repeater as set forth in claim 18 wherein the impedance corrector means further includes means interposed in the overall feedback path for increasing the gain of the first amplifier at the lower frequencies in the predetermined frequency band.

Claim 28

The negative impedance repeater as set forth in claim 17 wherein each of the first, second and third amplifiers includes high frequency cutoff feedback means for reducing the gain of the associated amplifiers at frequencies higher than the predetermined frequency band thereby to increase stability.

Claim 29

The negative impedance repeater as set forth in claim 20 wherein each of the series and shunt elements include associated overall feedback paths, said feedback paths adapted to adjust the gains of the associated amplifiers to move the operating point of the repeater toward increased stability in response to variations in the characteristics of the transmission facility.