LO and SSB Calibration (ADMV1013)

Hi Siddharth,

You would have to do this for every LO frequency. Not IF and RF frequency.

Thanks,

Taz

Hi, Thank you for the response.

The setup is for deferentially driven LO port and IF mode.

Okay, we will do for every LO Freq. as suggested. As you asked to adjust the MXER_OFF_ADJ_I_P,  MXER_OFF_ADJ_I_N, MXER_OFF_ADJ_Q_N, MXER_OFF_ADJ_Q_P and Quad until there is no more improvement in LO Leakage. 

So how should we approach for SSB suppression and LO Leakage both.

As when we are trying to adjust LOAMP_PH_ADJ_I_FINE, LOAMP_PH_ADJ_Q_FINE for SSB suppression/ phase adjust I suppose, it affects the LO amplitude setup done earlier.

Regards,

Siddharth Shah

Hi Siddharth,

We havent seen the phase adjustments typically affecting the 4xLO leakage at the RF output. Could you share your measurement results? 

Additionally here is a second method for 4xLO nulling which might be somewhat easier.

1. After going through the power on sequence write 0x505A to register 0x05.
2. Write 0xBF7C to register 0x07 (offsets will now be 95 for I_P and  I_N
3. Write 0xBF7C to register 0x08 (offsets will now be 95 for Q_P and Q_N)
4. Keep Q_P and Q_N at 95. Sweep offset I_P from 63 to 127. Offset I_N will be swept simultaneously from 127 to 63. E.g If I_P is 63, I_N should be 127. If I_P is 70, I_N should be 120. So the difference between 95 and I_P should be equal and opposite for I_N. While sweeping the I_P and I_N offsets monitor the 4xLO. After sweeping the offset I_P and I_N, choose the offset values that give the best 4xLO.

         5. Now sweep offset Q_P and Q_N the same way as offset I_P and I_N and choose the offset values that give                 the best 4xLO.

Thanks,

Taz

Hi Taz,

Not only phase adjustments is affecting the 4xLO leakage at the RF output, but LO Leakage adjustment is also affecting SSB Suppression. It should not affect either way but it is you can check with the Eval board there, that's the reason i want to know the approach / flow for calibration instead of trial method. (Using LMX2594 EVAL for LO)

Will share measurement snaps in a day or two. 

Thanks, and Regards,

Siddharth Shah

Hi Siddharth,

I do see at some frequencies where the phase adjust impacts the LO leakage. For most of my measurements if the sideband rejection improves using the phase adjust bits the 4xLO leakage will improve as well.

At some frequencies where I did not see such a correlation I had to go back and follow the LO nulling algorithm (the second LO nulling algorithm I posted earlier). Though, in this case the nulled 4xLO leakage will not be the same as before. If the 4xLO leakage is still too high for your system then I recommend using a bandpass filter at the RF output.

Please share your measurements results as well.

Thanks,

Taz 

Hi Taz,

I figured out some part on adjusting the bits to suppress, little bit exhaustive. sharing the measured result of our prototype board trying to suppress LO leakage and USB. Yeah a BPF will do the remaining for USB.

My Observation:

Mixer_Vgate plays a major role. while the other bits of register 5, 6, 7, 8, 9 needs to be varied repeatedly to get better suppression. Have tried for several frequency it works.

Any comments on my response?

Any comments on my response?