Conversion gain for mixer (BJT switch)

[adamaero]

Homework Statement

a) If this mixer is connected to a matching 50Ω resistor, what is the conversion gain?
b) IIP3 (Third Order Intercept Point) is 15 dBm, what would be A_1dB?
c) What is P_1dB?

Homework Equations

https://www.ece.ucsb.edu/Faculty/rodwell/Classes/ece218b/notes/Mixer1.pdf#page=9

b) A_1dB = √[0.145|α₁/α₃|]

c) P_1dB = A_1dB²/(2R_L)

The Attempt at a Solution

a) 1/pi = 0.318

b) I don't understand the alphas.

 

[gneill]

b) I don't understand the alphas.

Perhaps they might be associated with the collector-emitter current gains of the transistors?

You might need to search out a derivation of that formula.

 

[adamaero]

Searching "-datasheet transistor 1db gain .045" doesn't help.

 

[gneill]

Where did you first come across the formula?

 

[adamaero]

 

[adamaero]

Part (a) is
(1/pi)*g_m*R1
(1/pi)*(1/26)*1000 = 12.25 = C.G.

(b) probably in millivolts range

Re-did search with "-datasheet transistor 1db gain" and got some good results... But never mind; I'll move on, sunk cost.