Reduction of intermodulation products

Claim 2

Apparatus for linearly amplifying signals, comprising: a. an amplifier, having a non-linear amplitude characteristic; and b. means, anteriorly connected to said amplifier and having an amplitude characteristic inverse to said amplifier, for predistorting the amplitude of an input signal wherein said means for predistorting includes a feedforward control means for controlling said inverse characteristic.

Claim 3

The apparatus of claim 1 wherein said means for predistorting comprises: a. means for generating a first signal substantially linearly proportional to said input signal; b. means, responsive to said feedforward control means, for generating a second signal substantially exponentially proportional to said input signal; and c. means, connected to said first and second signal generating means, for combining said first and second signals.

Claim 4

The apparatus of claim 1 wherein said means for predistorting comprises: a. means for dividing said input signal into first and second signals; b. means, connected to said dividing means, for substantially linearly attenuating said first signal; c. means, responsive to said feedforward control means, for substantially exponentially attenuating said second signal; and d. means, connected to said first and second signal attenuating means, for adding said linearly attenuated and said exponentially attenuated signals.

Claim 5

The apparatus of claim 3 wherein said means for exponentially attenuating comprises a diode attenuator having a control input terminal and wherein said means for controlling comprises means for generating a control current proportional to the amplitude of said input signal and for feeding said control current to said control input terminal.

Claim 6

The apparatus Of claim 4 further including: a. means, connected to said means for controlling, for passing control current to said diode attenuator up to a predetermined maximum; and b. means, connected between said amplifier and said means for predistorting, for passing said added signal to said amplifier up to a predetermined maximum amplitude.

Claim 7

The apparatus of claim 1 wherein said amplifier has a differential phase characteristic and including means, anteriorly connected to said amplifier, for compensating for said differential phase characteristic.

Claim 8

Apparatus, anteriorly connected to an active device having a non-linear power characteristic, having a power characteristic inverse to that of said active device for effectively linearizing said power characteristic, comprising: a. means, responsive to an input signal, for generating a first signal substantially linearly proportional to said input signal; b. means, responsive to said input signal, for generating a second signal substantially exponentially proportional to said input signal; and c. means for combining said first and second signals.

Claim 9

Apparatus, anteriorly connected to an active device having a non-linear power characteristic, having a power characteristic inverse to that of said active device for effectively linearizing said power characteristic, comprising: a. means, responsive to an input signal, for generating a first signal substantially linearly proportional to said input signal; b. means, responsive to said input signal, for generating a second signal substantially exponentially proportional to said input signal; and c. means for combining said first and second signals.

Claim 10

Apparatus, anteriorly connected to an active device having a non-linear power characteristic, having a power characteristic inverse to the power characteristic of said active device, for predistorting an input signal, comprising: means, responsive to said input signal, for dividing said input signal into first and second signals; b. means, connected to said dividing means, for substantially linearly attenuating said first signal; c. means, connected to said dividing means, for substantially exponentially attenuating said second signal; and d. means, connected to said first and second signal attenuating means, for combining said linearly attenuated signal and said exponentially attenuated signal.

Claim 11

Apparatus, anteriorly connected to an active device having a non-linear power characteristic, having a power characteristic inverse to the power characteristic of said active device, for predistorting an input signal, comprising: means, responsive to said input signal, for dividing said input signal into first and second signals; b. means, connected to said dividing means, for substantially linearly attenuating said first signal; c. means, connected to said dividing means, for substantially exponentially attenuating said second signal; and d. means, connected to said first and second signal attenuating means, for combining said linearly attenuated signal and said exponentially attenuated signal.

Claim 12

The apparatus of claim 8 wherein said means for substantially exponentially attenuating comprises: a. a first diode attenuator, responsive to said second signal and having a control input terminal; b. feedforward control means, responsive to said input signal, for generating a control current proportional to the power of said input signal; and c. means, connected to said feedforward control means, for applying said control current to said control input terminal.

Claim 13

The apparatus of claim 9 wherein said means for generating comprises in series a variable attenuator, a crystal detector and an amplifier.

Claim 14

The apparatus of claim 10 wherein said means for substantially linearly attenuating comprises: a. a second diode attenuator, responsive to said first signal and having a control input terminal; and b. means, connected to said second diode attenuator, for providing a fixed control current to the control input terminal of said second diode attenuator.

Claim 15

The apparatus of claim 11 wherein said means for dividing and said means for combining are hybrid circuits.

Claim 16

The apparatus of claim 12 further including: a. a clamp, connected to said means for generating, for passing control current to said first diode attenuator up to a predetermined maximum; and b. a limiter, connected between said apparatus for predistorting and said active device for passing signals to said active device up to a predetermined maximum amplitude.

Claim 17

Apparatus for amplifying signals, comprising: a. an amplifier, having a differential phase characteristic; and b. means, anteriorly connected to said amplifier, for phase shifting an input signal to said phase shifting means in dependence upon the amplitude of said input signal and for applying said phase shifted signal to said amplifier wherein the phase of the output of a signal from said amplifier, is in the same phase relationship to the phase of said input signal irrespective of the amplitude of said input signal.

Claim 18

Apparatus for amplifying signals, comprising: a. an amplifier, having a differential phase characteristic; and b. means, anteriorly connected to said amplifier, for phase shifting an input signal to said phase shifting means in dependence upon the amplitude of said input signal and for applying said phase shifted signal to said amplifier wherein the phase of the output of a signal from said amplifier, is in the same phase relationship to the phase of said input signal irrespective of the amplitude of said input signal.

Claim 19

The apparatus of claim 14 wherein said means for phase shifting comprises: a. first means for dividing said input signal into first And second signals; b. means, connected to said first dividing means, for differentially varying the amplitude of said first signal with respect to the amplitude of said second signal in dependence upon the amplitude of said input signal; and c. first means, connected to said differentially varying means, for combining said differentially varied signals to obtain a resultant signal having a phase shift with respect to said input signal which will compensate for the phase shift of said resultant signal through said amplifier.

Claim 20

The apparatus of claim 15 wherein said means for differentially varying comprises: a. means, connected to said first dividing means, for substantially linearly attenuating said first signal; b. second means, connected to said first dividing means, for dividing said second signal into third and fourth signals having a phase difference between them; c. means, connected to said second dividing means, for substantially exponentially attenuating said third signal; and d. means, connected to said second dividing means, for substantially linearly attenuating said fourth signal; and e. second means, connected to said third and fourth signal attenuating means, for combining said third and fourth signals into a fifth signal having a phase difference with respect to said first signal.

Claim 21

The apparatus of claim 16 wherein said means for substantially exponentially attenuating comprises: a. a first diode attenuator, having a control input terminal; b. means, responsive to said input signal, for generating a control current proportional to the amplitude of said input signal; and c. means, connected to said control current generating means, for applying said control current to said control input terminal.

Claim 22

The apparatus of claim 17 wherein said first means for combining comprises means for adding said first signal and said fifth signal to provide said resultant signal.

Claim 23

The apparatus of claim 14 wherein said amplifier has a non-linear amplitude characteristic and means, anteriorly connected to said amplifier, for effectively linearizing said non-linear amplitude characteristic.

Claim 24

Apparatus, anteriorly connected to an active device having a differential phase characteristic, comprising: a. means for dividing an input signal into first and second signals; b. means, connected to said dividing means, for differentially varying the power of said first signal with respect to the power of said second signal in dependence upon the power of said input signal; and c. means, connected to said differential varying means, for combining said differentially varied signals to obtain a resultant signal having a phase shift with respect to said input signal which will compensate for the phase shift of said resultant signal through said amplifier.

Claim 25

Apparatus, anteriorly connected to an active device having a differential phase characteristic, comprising: a. means for dividing an input signal into first and second signals; b. means, connected to said dividing means, for differentially varying the power of said first signal with respect to the power of said second signal in dependence upon the power of said input signal; and c. means, connected to said differential varying means, for combining said differentially varied signals to obtain a resultant signal having a phase shift with respect to said input signal which will compensate for the phase shift of said resultant signal through said amplifier.

Claim 26

Apparatus, anteriorly connected to an active device having a differential phase characteristic, comprising: a. first means for dividing an input signal into first and second signals; b. means, connected to said first dividing means, for substantially linearly attenuating said first signal; c. second means, connected to said first dividing means, for dividing said second signal into third and fourth signals having a phase difference between them; d. means, connected to said second dividing means, for substantially exponentially attenuating said third signal; e. means, connected to said second dividing means, for substantially linearly attenuating said fourth signal; f. means, connected to said first dividing means, for phase shifting said first signal -270* with respect to said input signal; g. means, connected to said third and fourth signal attenuating means, for subtracting said third signal from said fourth signal to produce a fifth signal having a phase shift of -180* with respect to said input signal; and h. means, connected to said first signal linearly attenuating and phase shiftIng means and said subtracting means, for adding said linearly attenuated and phase shifted first signal and said fifth signal to produce a resultant signal having a phase shift with respect to said input which will compensate for the phase shift of said resultant signal through said active device.

Claim 27

Apparatus, anteriorly connected to an active device having a differential phase characteristic, comprising: a. first means for dividing an input signal into first and second signals; b. means, connected to said first dividing means, for substantially linearly attenuating said first signal; c. second means, connected to said first dividing means, for dividing said second signal into third and fourth signals having a phase difference between them; d. means, connected to said second dividing means, for substantially exponentially attenuating said third signal; e. means, connected to said second dividing means, for substantially linearly attenuating said fourth signal; f. means, connected to said first dividing means, for phase shifting said first signal -270* with respect to said input signal; g. means, connected to said third and fourth signal attenuating means, for subtracting said third signal from said fourth signal to produce a fifth signal having a phase shift of -180* with respect to said input signal; and h. means, connected to said first signal linearly attenuating and phase shiftIng means and said subtracting means, for adding said linearly attenuated and phase shifted first signal and said fifth signal to produce a resultant signal having a phase shift with respect to said input which will compensate for the phase shift of said resultant signal through said active device.

Claim 28

The apparatus of claim 21 wherein said means for substantially exponentially attenuating comprises: a. a first diode attenuator having a control input terminal; b. means, responsive to said input signal, for generating a control current proportional to the power of said input signal; and c. means, connected to said control current generating means, for applying said control current to said control input terminal.

Claim 29

The apparatus of claim 22 wherein said means for generating comprises, in series, a variable attenuator, a crystal detector and an amplifier.

Claim 30

The apparatus of claim 23 wherein said means for substantially linearly attenuating comprises: a. a second diode attenuator, having a control input terminal; and b. means for providing a fixed control current to the control input terminal of said second diode attenuator.

Claim 31

The apparatus of claim 24 wherein said means for dividing, said means for subtracting, said means for phase shifting, and said means for adding are hybrid circuits.

Claim 32

In combination: a. an amplifier, having a non-linear amplitude characteristic and a differential phase characteristic; b. means, anteriorly connected to said amplifier and having an amplitude characteristic inverse to said amplifier, for predistorting the amplitude of an input signal; and c. means, anteriorly connected to said amplifier, for phase shifting an input signal in dependence upon the amplitude of said input signal and for applying said phase shifted signal to said amplifier wherein the phase of the output of a signal from said amplifier is in the same phase relationship to the phase of the input signal irrespective of the amplitude of said input signal.

Claim 33

In combination: a. an amplifier, having a non-linear amplitude characteristic and a differential phase characteristic; b. means, anteriorly connected to said amplifier and having an amplitude characteristic inverse to said amplifier, for predistorting the amplitude of an input signal; and c. means, anteriorly connected to said amplifier, for phase shifting an input signal in dependence upon the amplitude of said input signal and for applying said phase shifted signal to said amplifier wherein the phase of the output of a signal from said amplifier is in the same phase relationship to the phase of the input signal irrespective of the amplitude of said input signal.

Claim 34

The combination of claim 26 wherein said means for predistorting comprises: a. first means for dividing an input signal into first and second signals; b. means, connected to said first dividing means, for substantially linearly attenuating said first signal; c. means, connected to said first dividing means, for substantially exponentially attenuating said second signal; and d. means, connected to said first and second signal attenuating means, for adding said linearly and exponentially attenuated signals.

Claim 35

The combination of claim 27 wherein said means for phase shifting comprises: a. first means for dividing an input signal into first and second signals; b. means, connected to said first dividing means, for substantially linearly attenuating said first signal; c. second means connected to said first dividing means for dividing said second signal into third and fourth signals having a phase difference between them; d. means, connected to said second dividing means, for substantially exponentially attenuating said third signal; e. means, connected to said second dividing means, for substantially linearly attenuating said fourth signal; f. means, connected to said first dividing means, for phase shifting said first signal -270* with respect to said input signal; g. means, connected to said third and fourth signal attenuating means, for subtracting said third signal from said fourth signal to produce a fifth signal having a phase shift of -180* with respect to said input signal; and h. means, connected to said first signal linearly attenuating and phase shifting means and said subtracting means, for adding said linearly attenuated and phase shifted first signal and said fifth signal to produce a resultant signal having a phase shift with respect to said input signal which will compensate for the phase shift of said resultant signal through said amplifier.

Claim 36

The cOmbination of claim 28 wherein said means for substantially exponentially attenuating comprises: a. a first diode attenuator, having a control input terminal; b. means, responsive to said input signal, for generating a control current proportional to the amplitude of said input signal; and c. means, connected to said control current generating means for applying said control current to said control input terminal.

Claim 37

The combination of claim 29 wherein said means for generating comprises, in series, a variable attenuator, a crystal detector and an amplifier.

Claim 38

The combination of claim 30 wherein said means for substantially linearly attenuating comprises: a. a second diode attenuator, having a control input terminal; and b. means, connected to said second diode attenuator, for providing a fixed control current to the control input terminal of said second diode attenuator.

Claim 39

The combination of claim 31 wherein said means for dividing, said means for phase shifting, said means for subtracting and said means for adding are hybrid circuits.