Methods and apparatus for substantially reducing nonlinear distortion using multiple nonlinear devices

An apparatus for substantially reducing nonlinear distortion, the apparatus comprising:

• an input coupling means having an input and first and second outputs that is capable of splitting an input signal into first and second in-phase signals;
• 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;
• an attenuator having an input in communication with output of the first nonlinear device and an output;
• a second coupling means having a first input in communication with the output of the second nonlinear device, a second input in communication with the output of the attenuator and an output;
• the second coupling means combines a 180 degree phase shifted and attenuated output of the second nonlinear device with an output of the attenuator;
• a third nonlinear device having an input in communication with output of the first nonlinear device and an output;
• a fourth nonlinear device having an input in communication with the output of the second coupling means and an output;
• and
• a third coupling means having a first input in communication with the output of the third nonlinear device, a second input in communication with the output of the fourth nonlinear device and an output, wherein the third coupling means combines a 180 degree phase shifted and attenuated output of the fourth nonlinear device with the output of the third nonlinear device to form a final output signal.

A method substantially reducing nonlinear distortion, in accordance with an embodiment of the present invention comprising the steps of:

• transmitting an input signal to an input coupling means that splits the input signal into first and second in-phase coupled signals;
• transmitting the first coupled signal to a first nonlinear device, having a Taylor series expansion describing a first nonlinear device output signal, y1, in terms of a first nonlinear device input signal x1, as y1=α0+α1x1+α2x12+α3x13+α4x14 . . . ;
• transmitting the second coupled signal to a second nonlinear device, having a Taylor series expansion describing a second nonlinear device output signal, y2 in terms of a second nonlinear device input signal, x2, as y2=b0+b1x2+b2x22+b3x23+b4x24 . . . , and with substantially equal time delay and phase in the first and second nonlinear devices;
• transmitting the first nonlinear device output signal to an attenuator such that an attenuator output signal is, k times an attenuator input signal;
• subtracting the second nonlinear device output signal from the attenuator output signal to form a difference signal;
• transmitting the first nonlinear device output to a third nonlinear device, with Taylor series expansion describing a third nonlinear device output y3, in terms of a third nonlinear device input signal x3, as y3=c0+c1x3+c2x32+c3x33+c4x34 . . . ;
• transmitting the difference signal to a fourth nonlinear device, with Taylor series expansion describing a fourth nonlinear device output signal, y4, in terms of a fourth nonlinear device input signal, x4, as y4=d0+d1x4+d2x42+d3x43+d4x44 . . . , and with substantially equal time delay and phase in the third and fourth nonlinear devices;
• and
• subtracting the fourth nonlinear device output signal from the third nonlinear device output signal to form a final output signal.