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Measurements >> RF Measurements >> IQ measurement
https://designers-guide.org/forum/YaBB.pl?num=1212550853

Message started by aaron_do on Jun 3^rd, 2008, 8:40pm

Title: IQ measurement
Post by aaron_do on Jun 3^rd, 2008, 8:40pm

Hi all,

I need to measure the IQ performance (amplitude and phase mismatch) of a down-conversion mixer. Due to the limitations of the probe station i can only probe three differential signals. So if i have one as the LO and one as the RF input, I can only measure 1 output. That makes it a little difficult to measure both I and Q at the same time.

Since i have one GSSG output, I was thinking of using it as: Gnd Signal_I Signal_Q Gnd. Then i can take the I and Q signals separately and measure amplitude and phase mismatch on an oscilloscope. Is this possible?

thanks,
Aaron

Title: Re: IQ measurement
Post by ACWWong on Jun 4^th, 2008, 4:21am

why do you need to probe LO ? don't you have an oscillator on the chip ?

if you do only have 1 probe, what you suggest seems reasonable, although i'd also look at G,IB,QB,G to confirm the result and G,I,IB,G and G,Q,QB,G to get the most information. Also you might like to measure the mismatch using a VSA with IQ inputs or similar rather than a scope to get perhaps better phase mismatch accuracy numbers.