Intermodulation due to non linearity of amplifier

[jason_class]

Hello All The Experts,

I ask for your kindness to give some advice about Intermodulation due to nonlinearity of amplifer.
Folowing is the output from a non linear amplifier in general,

Vout = Ko + K1 Vin + K2 Vin^2 and so on

May I know how do we get the value of Ki = K1 , K2 , K3 ...if there
are 3 input signals and they form harmonics? Is it through equation or
graphical method?
Kindly share with me any good lecture notes or good website that explain this in details.

Kindly enlighthen me

I wish to hear from you all.

rgds and thanks
jason

 

[Pushhead]

Hello Jason,

The main reason for the non-linearity in an amplifier is the non-lin. characteristics of a diode.

(You can consider the equivalent Ebers-Moll model as an amp. )

Since we are interested in the linear part of the diode I-V relations we bias it and apply relatively small amplitude AC signal added to the DC bias.

The output current is a taylor serie approximation of the I-V function at the Q-Point of the amp. circuit. (i.e. Iout=K1+K2*Vin+K3*Vin^2+....)
The 1st coefficient is the DC current,
2nd is the diode junction conductance, etc.

I recommend "Microwave Engineering" by D.M Pozar Ch. 10.2 "Detectors and mixers",
but I think you'll find the same explanations in any electronic devices theory book (Milman and Halkias maybe ?)

Cheers,
P.

 

[jason_class]

Dear P

Thank you for the comments.
Things are clearer. I will look that book out at library but I know books are always not available when I need it.
If you do have any good notes or link about this, kindly share with me
A document that explain how to get or calculate the k values before we plug in the IM equation will be very much helpful.
Thank you


rgds and thanks
Jason