IQ mixer LSB and USB image rejection and conversion loss

[Simo.Da]

Good morning gents

I am trying to test the rejection and conversion loss of "HMC1056LP4BE" IQ mixer (https://www.analog.com/media/en/technical-documentation/data-sheets/hmc1056.pdf).

I set the LO to be +10dBm @8.5GHz, , IF1: -10dBm @250MHz, IF2: -10dBm @250MHz - Here I am using 3 different ports of a multichannel signal generator.

On the output, I am getting something wired, as every time I turn the off the IF1 and IF2 I get different values! The three runs below as an example:

-20.07 dBm @8.250GHz, -17.79 dBm @8.750GHz, -27.85 dBm @8.5GHz
-18.89 dBm @8.250GHz, -18.77 dBm @8.750GHz, -27.85 dBm @8.5GHz
-16.45 dBm @8.250GHz, -27.81 dBm @8.750GHz, -29.10 dBm @8.5GHz

On the other hand when I use either IF1 or IF2 and turn the other off, I am getting something consistent like below

(IF2 is off)
-22.26 dBm @8.250GHz, -22.14 dBm @8.750GHz, -27.82 dBm @8.5GHz
-22.19 dBm @8.250GHz, -22.08 dBm @8.750GHz, -27.72 dBm @8.5GHz
-22.12 dBm @8.250GHz, -22.01 dBm @8.750GHz, -27.65 dBm @8.5GHz

(IF1 is off)
-21.79 dBm @8.250GHz, -21.88 dBm @8.750GHz, -27.65 dBm @8.5GHz
-21.81 dBm @8.250GHz, -21.89 dBm @8.750GHz, -27.63 dBm @8.5GHz
-21.83 dBm @8.250GHz, -21.91 dBm @8.750GHz, -27.64 dBm @8.5GHz


Is anybody have any idea why I am getting different value every time please? Is there anything wrong I am doing and not aware of!
Nothing seems right to me

 

[G4BCH]

IF1 & IF2 have to have a 90 degree phase shift between them for it to work correctly as an up converter. Use a single output from your signal generator and pass the output to a 90 degree splitter the connect the outputs of the splitter to the inputs of the mixer.

 

[BigBoss]

Are IF1 and IF2 90 Degree Phase Shifted ? They ought to be..

 

[Simo.Da]

IF1 & IF2 have to have a 90 degree phase shift between them for it to work correctly as an up converter. Use a single output from your signal generator and pass the output to a 90 degree splitter the connect the outputs of the splitter to the inputs of the mixer.

This is what I am planning to do, but I was thinking that if I use a multichannel signal generator to generate two CW one at 90 degrees and the other at 0 would do the job, but it seems the CW signals don't have the same trigger, therefore every time I/Q turned off and on it changes the phase.

If I managed to get 90 deg difference, shall I get both of the LSB and USB at something around -20dBm using the same setup?

--- Updated Jun 1, 2022 ---

Are IF1 and IF2 90 Degree Phase Shifted ? They ought to be..

I was thinking if I generate two CWs (one at 0 and the other at 90) that would do the job, but it seems not!

 

[BradtheRad]

One wavelength=1.4 inches at 8.5 GHz. So theoretically a wire length 1/3 inch delays the electrical signal by a quarter wavelength or 90 degrees.

Youtube video shows this method: Measuring the Speed of Light

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