StoppTidigare
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Hi all, I also have some questions about the IP2/IP3 paper.
Ken, you wrote that IPN= P+DeltaP/(N-1).
This is how I've understood it: Say that one applies an input signal with power P to a nonlinear device. If I connect a power meter at the input I'll measure the power y1, which of course I can write as the function y1=x, where x is the input power in dBm. A linear function that starts at the origin.
If I measure the n-order component at the output it will certainly contain less power, and if I increase the input power it will increase as x^N.
If I linearise this function at x=1. I will be able to draw a tangent described by the line y2=N*x + C, where C is a constant to be determined.
The value of IPn is the point where the functions y1=x and y2=N*x + C cross.
This is done by finding the value of x where y1=y2, and then instert that value of x in either of the functions y1 or y2.
Starting first with the determination of C...
From your definitions of P and deltaP, we have that the difference y1-y2 =delta_p at inputsignal x= P This gives: y1-y2 =Delta_p= x- (N*x +C), this is at x=P,so therfore Delta_p=P-(N*P +C) <=> Delta_p=P(1-N) -C <=> C=-Delta_P + P(1-N)
So know we can write the function y2 as: y2=N*x + P(1-N) - Delta_p
For which x are they equal ? y1=y2 => x= N*x + P(1-N) - Delta_p <=> x(1-N) = P(1-N) - Delta_p <=> x= P - Delta_p/(1-N) <=> x= P + Delta_P/(N-1)
What value y1 or y2 (IPN)is there at the crosspoint? Plug x into the function y=x ,so
Am I correct ? I'm sure about the algebra but I've might misinterpeted the concept anyway.
You donīt show in your paper that IPN formula written above here is equal to formulas at page 4, for instance iIP2=pi1 +(po2 - po12)
How should I proceed to derive that they are equal ? (equal to IP2= P + Delta_P/(2-1)
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