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How to match mixer's LO and RF input?(Gilbert mixer)

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Karenhuang888

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I am a new RF designer.

Now I got the LO and RF input reflection coefficient(or input impedance) using large signal simulation @ ADS. However, when I use Smith Chart to conjugate match this impedance to 50 Ohm. I find it's totally wrong. It is does not improve the reflection coefficient, but it makes it worse. I don't know why. Could you tell me why?

Thanks a lot.
 

Hi

I am not an expert too, but you can take a look on some articles where it is mentioned how to make a match. As far as I can see from the Agilent article, it is not possible to make a simple match.

Hope it can help or at least give some understanding.

**broken link removed**
http://eesof.tm.agilent.com/pdf/mixerpag.pdf
 

Karenhuang888 said:
I am a new RF designer.

Now I got the LO and RF input reflection coefficient(or input impedance) using large signal simulation @ @DS. However, when I use Smith Chart to conjugate match this impedance to 50 Ohm. I find it's totally wrong. It is does not improve the reflection coefficient, but it makes it worse. I don't know why. Could you tell me why?

Thanks a lot.
Click to expand...

use attanuator
 

You don't generally need to match LO port of Gilbert cell to drive LO signal. If LO signal is sufficiently high, for instance 200mVpk or more it will work. LO port is namely has high input impedance.

But RF port, small signal s-parameters will be enough to match to the source. In fact some mixers have relatively high input impedance at RF port, so in that case (maybe) you won't need to matching circuit.

I don't know your case, therefore I can't say a certain thing...
 

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