Dear Analog Devices,
We are trying to do a demo for a customer in which we would like to use the LTC5562 DC2483A-B evaluation board (LTC5562 mixer as a downconverter) spannered in to our set-up. For this demo we only need one set of frequencies:
RF = 5.5GHz
LO = 7.1GHz
IF = 1.6GHz (LO - RF)
There is a major hang up though: On the evaluation board the RF port of the mixer has a 1:1 transformer fitted, the TC1-1-13M+ from Mini Circuits, which doesn't go up to 5.5GHz. Mini Circuits do have transformers that go up to 6GHz, even 8GHz, BUT they are not footprint compatible. Does anyone here know of any transformers that can fit on the evaluation board to allow us to tune the LTC5562 to the aforementioned frequencies. For the IF port there are footprint compatible alternatives, while the LO can be single-endedly driven. The RF port is holding us up though.
While the Mini-Circuits 6 and 8GHz transformers do not have exact footprint as the TC1-1-13M+. They are close enough that you can fit them onto the eval board with some hacking. I have done it many times.
Thanks for your reply. I tried doing this using the Mini Circuits TCM1-83X+ with short-circuiting pins No 5 and 6 to accommodate the part on the existing layout of the DC2483A-B evaluation board. Whilst it works, I think the conversion loss of the mixer takes a hit by a few dB. Have you noticed anything similar?
You do need to modify the matching network to get good return loss with the TCM1-83X+ transformer. Also don't forget to rematch the IF output to your frequency. At high frequencies, the circuit is more sensitive to component mounting. If you have dedicated, properly laid out PCB, the performance would be better. However, you should not experience several dBs of addition loss, and you should be able to get performance similar to what is shown in the datasheet.