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Measure of Double Balanced Mixer

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Newbie level 5
Feb 22, 2006
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I am a newbie in RF circuit, and I am required to design a double balanced mixer for research. The RF frequency is about 17 GHz.

The question is is how to measure the mixer. Since all signals (RF, LO, IF) are differential, should I
1. convert both the input signals (RF, LO) from unbalanced (single ended) ones to balanced (differential) ones by balun, and convert the output IF signal to unbalanced one; or
2. using differential signal generator (I don't know if there exist this stuff), and connect one of the output (IF) by a proper impedance, and measure the other.

Also, I am thinking of the possibility of testing the mixer on wafer. Does it feasible? And does it require G-S-S-G probes instead of general G-S-G ones?

The questions may be basic, but It does trouble me. Any advice and comment will be appreciated.

You can use a differential network analyzer. Such as
**broken link removed**


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leander, I'm also working on a double-balanced mixer. For RF port I use this circuit, it converts from single-to-differential. See Roubik Gregorian's books if need further information about it.
Hope helps you, and continuing sharing ideas about mixer.


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boy and STOIKOV, thank you for your replies.

in your circuit, do you short one of the RF port by a capacitor? Then how do you consider the impedance matching on that port? Does it degrade the performace? I think I should read that book first.

I visited the website and I wonder we do not have differential analyzer, and it is impossible for us to get one. So I am considering using balun.

leander, in Mn2 gate I just connect a DC source in order to polarize it. That value is the same than DC component of RF signal applied to Mn1.
See fig.15 of paper "A CMOS passive mixer with low flicker noise for low-power direct-conversion receiver.pdf", a capacitor is connected to ground as you said. So I wonder if it is correct the DC source or maybe the author omits biasing circuits.
Please advise.

If you are going to test the mixer on-wafer anyways, it is probably best to use 180° power splitter/combiner. In this case you will need a a GSSG or GSGSG probes. Good luck.

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