Finding power levels at mixer's input
I have a frequency mixer of gain = 7 dB (at frequency which I need). His PLO = -5dBm, PRFIN = -23dBm. At the output of the mixer (RF output), the power is 5 dBm. I would like to calculate the power level at the mixer's inputs.
I am thinking that maybe the power at each of the two mixer inputs is -2 dBm (5 dBm-7dB=-2 dBm). But it's only a guess. I am not sure if I have to include some other parameters like the minimum power that the mixer needs for functioning, noise figure, IIP3, conversion power gain?. to find the power's at each of the mixer's inputs ( IF and LO)? And would the power at each of the 2 inputs (IF and LO) be the same or different ?
So I am asking for some help to find them ?
Thank you
LO Power doesn't contribute into Mixer Gain when it's in saturated driven mode.But there is a unclear point on your numbers.
Is this mixer an active one or passive one ? So, +7dB Gain says that is an active mixer.If output power +5dBm, how the input power becomes -23dBm ?
It should normally be +5-7=-2dBm.?
I think the mixer is not sufficiently driven by LO side, therefore it acts an amplifier-mixer.
What if my mixer is passive for exemple it's LT5511 (http://cds.linear.com/docs/en/datasheet/5511f.pdf) and I should have 5 dBm at the mixer's output. What would be the power at inputs (IF and LO) and how do I calculate them? My operating frequency is 900 MHz.
Thank you
This is not a passive mixer, au contraire it's active mixer and it consists of buffer amplifiers ( 2 stages) in order to hard-drive the mixer core.
As I have stated before.LO input of a mixer is to hardly commutate the RF signal ( I assume that is a down-converter ) to obtain an IF signal.While it is doing that, it drives the transistors up to rail limits
(V(sat)-to-Vcc).So, the transistors act as switches.If you look at the Conversion Gain vs. LO Power curve on page 4, you'll see that the Conversion Gain does not change much with LO Power.
Briefly, if the Conversion Gain is 0dB @ 25C stated in page 4 , RF signal level can be found approximately RF Power@Input=IF Power@Output.