We have the eval board of ADL5380. We desire to operate it in a single-ended mode. As suggested in the datasheet the RF and LO input already has a 100pf capacitor connected to one port and ground on the eval board for single-ended mode. According to the datasheet per pin impedance is 25ohm so in the eval board with the onboard baluns connected do we need to match it at 50ohm since according to the datasheet all the pins are at 25ohm impedance or all are at 50ohm differential. Please correct if any confusion in understanding.
We have given 5.81Ghz input to RF port at -10dBm and 5.81Ghz input to LO at -5dBm. The board I guess is by default configured to single-ended operation since the SMA connecter not connected to RFIN & LOIN and 100pf already connected. ILO & QLO we have terminated with 50ohm. Is the experiment setup correct or we have to make changes to work in a single-ended configuration?
We expect a DC signal at the output I and Q single-ended but while observing on the scope but we find the noise at 10mV. We want to observe a DC signal flat line and only the phase difference between the RF and LO. Please correct us if any mistakes and suggest a way to achieve the same. Attaching images of the test setup and observations on the scope for 5.81Ghz at the RF and LO. Using this setup we have also done a trial with 4.7Ghz and 4.8Ghz at the RF and LO respectively to and we could observe 100Mhz signal at around 160mV as shown in the attached image.
The importance is the DC voltage across the load resistor. As the phase changes it causes the output stage to pump current from one side of the diff pair to the other.
If you are working with…
Thank you for the timely response. We have gone through the updated schematic and I think it is the same what we have and we have not connected or removed any component.
We are giving trigger to RF and LO at the same time, if there is any other way to make sure if signals are in sync then please guide for the same.
From datasheet page number 34, table 5 it is shown that for the single-ended output, the resistors R2x-R5x needs to be populated for bypassing the output transformer and R13x-R18x needs to be populated for a single-ended mode. Please correct us if anything is written is incorrect. According to our understanding we have to populate registers at R2x-R5x.
Another point which is not clear is about the 200ohm impedance, is the eval board configured for 50ohm per pin? please elaborate a little on this. And I guess since the output being DC we might not require any matching at the output ports, please correct if any mistake in understanding.
You're welcome. Please see below for some more guidance.
Thank you for such an elaborate explanation. Will do this and get back as soon as possible.
I am making the register changes to bypass transformer balun as written in my previous message and use the differential load impedance as suggested by you. While testing for DC may I get some reference data or input Vs expected output if any observations are recorded at your end to verify proper configuration of the board. Or else please guide on verification of correct configuration.
And if I bypass the balun, according to my understanding please correct me if wrong I will get differential output but I want single ended output so how to achieve that for DC output at 5.81ghz RF and LO.
We also tried to see the inputs of the balun at the I and Q side after giving 5.81Ghz at RF and LO. We observed 2.4 V DC at both I and Q. But this value did not change even after changing the cable length at RF. We were expecting to see a voltage change with respect to the phase change due to cable length change at the RF but at both times we observed same 2.4V at the input of the Balun. Here we have not yet made any change to the eval board. We did testing this way to check the desired DC signal since the balun will block our desired DC signal. Actually we dont think this voltage is due to the signal but it was also present when the RF and LO were OFF and only board was powered on. Please correct us if there is any confusion in our understanding.