Methods and apparatus for substantially reducing third order intermodulation distortion and other nonlinear distortions
First Claim
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1. An apparatus for substantially reducing nonlinear distortion, the apparatus comprising:
- an input coupling means having an input and first and second outputs, the input coupling means capable of splitting an input signal into first and second coupled signals that are in-phase with respect to each other;
a first nonlinear device having an input in communication with the first output of the input coupling means and an output;
a second nonlinear device having an input in communication with the second output of the input coupling means and an output; and
a subtractor having a first input in communication with the output of the first nonlinear device, a second input in communication with the output of the second nonlinear device and an output, wherein the subtractor is capable of subtracting an output signal of the second nonlinear device from an output signal of the first nonlinear device to generate a final output signal wherein the first nonlinear device defines a gain as G1 dB, the second nonlinear device defines a gain as G2 dB, the first nonlinear device defines a third order output intercept point as OIP31 dBm and the second nonlinear device defines a third order output intercept point as OIP32 dBm, and K=10 log10(p2/p1 ), where p1 is the input signal power level of the first nonlinear device and p2 is the input signal power level of the second nonlinear device, such that the first and second nonlinear devices and the input coupling means are provided such that most nearly 2(OIP31−
OIP32)=3(G1−
G2−
K), where G1 is not equal G2+K and such that the first and second nonlinear devices have substantially equal time delay and phase to substantially reduce third order nonlinearity.
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Abstract
Methods and apparatus are provided for substantially reducing and/or canceling nonlinearities of any order in circuits, devices, and systems such as amplifiers and mixers. In particular, methods and apparatus are provided for substantially reducing and/or canceling third order nonlinearities in circuits, devices, and systems such as amplifiers and mixers. A first coupler is used to split an input signal into two equal-amplitude in-phase components, each component is processed by two nonlinear devices with different nonlinearities, and a final combiner, such as a 180-degree hybrid, recombines the processed signals 180 degrees out of phase and substantially reduces and/or cancels the undesired nonlinear distortion components arising due to nonlinearities in the nonlinear devices.
101 Citations
12 Claims
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1. An apparatus for substantially reducing nonlinear distortion, the apparatus comprising:
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an input coupling means having an input and first and second outputs, the input coupling means capable of splitting an input signal into first and second coupled signals that are in-phase with respect to each other;
a first nonlinear device having an input in communication with the first output of the input coupling means and an output;
a second nonlinear device having an input in communication with the second output of the input coupling means and an output; and
a subtractor having a first input in communication with the output of the first nonlinear device, a second input in communication with the output of the second nonlinear device and an output, wherein the subtractor is capable of subtracting an output signal of the second nonlinear device from an output signal of the first nonlinear device to generate a final output signal wherein the first nonlinear device defines a gain as G1 dB, the second nonlinear device defines a gain as G2 dB, the first nonlinear device defines a third order output intercept point as OIP31 dBm and the second nonlinear device defines a third order output intercept point as OIP32 dBm, and K=10 log10(p2/p1 ), where p1 is the input signal power level of the first nonlinear device and p2 is the input signal power level of the second nonlinear device, such that the first and second nonlinear devices and the input coupling means are provided such that most nearly 2(OIP31−
OIP32)=3(G1−
G2−
K), where G1 is not equal G2+K and such that the first and second nonlinear devices have substantially equal time delay and phase to substantially reduce third order nonlinearity. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for substantially reducing nonlinear distortion the apparatus comprising:
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an input coupling means having an input and first and second outputs, the input coupling means capable of splitting an input signal into first and second coupled signals that are in-phase with respect to each other;
a first nonlinear device having an input in communication with the first output of the input coupling means and an output;
a second nonlinear device having an input in communication with the second output of the input coupling means and an output; and
a subtractor having a first input in communication with the output of the first nonlinear device, a second input in communication with the output of the second nonlinear device and an output, wherein the subtractor is capable of subtracting an output signal of the second nonlinear device from an output signal of the first nonlinear device to generate a final output signal, wherein the first nonlinear device is provided such that it has a Taylor series expansion describing the output signal of the first nonlinear device, y1, in terms of an input signal of the first nonlinear device, x1, as y1=a0+a1x1+a2x12+a3x13+a4x14 . . . , the second nonlinear device is provided such that it has a Taylor series expansion describing the output signal of the second nonlinear device, y2 in terms of an input signal of the second nonlinear device, x2, as y2=b0+b1x2+b2x22+b3x23b4x24 . . . , the ratio, k, is provided such that k=x2/x1, where k is set by the input coupling means provided, such that nonlinearities of order n are substantially reduced and/or canceled by setting most nearly k=(an/bn)1/n. - View Dependent Claims (7, 8)
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9. A method for substantially reducing third order distortion in an apparatus, the method comprising the steps of:
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splitting an input signal into first and second in-phase coupled signals, the ratio of a second in-phase coupled signal power, p2, to a first coupled signal power, p1, is defined as K=10 log10(p2/p1);
processing the first in-phase coupled signal at a first nonlinear device and the second in-phase coupled signal at a second nonlinear device, the first nonlinear device has a gain defined as, G1 dB, and a third order output intercept point defined as, OIP31 dBm, the second nonlinear device has a gain defined as, G2 dB, and a third order output intercept point defined as, OIP32 dBm, such that the relationship between the first and second nonlinear devices and the input coupling means is defined as, most nearly 2(OIP31−
OIP32)=3(G1−
G2−
K), where G1 is not equal to G2+K and the first and second nonlinear devices have substantially equal time delay and phase; and
subtracting an output signal of the second nonlinear device from an output signal of the first nonlinear device to yield a final output signal that substantially reduces third order nonlinearities.
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10. A method for substantially reducing nonlinear distortion in an apparatus, the method comprising the steps of:
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splitting an input signal into first and second in-phase coupled signals, wherein the ratio of the second in-phase coupled signal, x2, to the first in-phase coupled signal, x1, is defined as k=x2/x1;
processing the first in-phase coupled signal at a first nonlinear device and the second in-phase coupled signal at a second nonlinear device, the first nonlinear device has a Taylor series expansion describing an output signal, y1, in terms of an input signal, x1, as y1,=a0+a1x1+a2x12+a3x13+a4x14 . . . , the second nonlinear device has a Taylor series expansion describing an output signal y2, in terms of an input signal, x2, as y2=b0+b1x2+b2x22+b3x23+b4x24 . . . , such that the first and second nonlinear devices and the input coupling means are defined as most nearly k=(an/bn)1/n; and
subtracting an output signal of the second nonlinear device from an output signal of the first nonlinear device to yield a final output signal that substantially reduces nonlinear distortion of order n. - View Dependent Claims (11, 12)
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Specification
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Current AssigneeUniversity of North Carolina At Charlotte (University of North Carolina System)
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Original AssigneeUniversity of North Carolina At Charlotte (University of North Carolina System)
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InventorsWeldon, Thomas Paul
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Primary Examiner(s)Choe, Henry
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Application NumberUS10/794,005Publication NumberTime in Patent Office466 DaysField of Search330/149, 330/124.R, 330/254, 330/295, 330/84, 333/117US Class Current330/149CPC Class CodesH03F 1/3205 in field-effect transistor ...H03F 1/3211 in differential amplifiersH03F 1/3229 using a loop for error extr...H03F 1/3241 using predistortion circuit...
