Hello,
I am trying to simulate a simple application of AD8333 but have been unsuccessful. My 4*LO input is a 20 MHz sine wave (differential, 3 V peak to peak). The common-mode dc value to the 4*LO pins is about 2.5 V (as in figure 61 in the datasheet). to RF pins I have applied a 5 MHz sine wave (0.2 V amplitude). The common-mode voltage to the RF pins is also just about 2.5 V (as in figure 60 in the datasheet). At the output, I am using AD8021 for I-V conversion. I am not interested in filtering out the oscillations in the I and Q signals so I have the bandwidth of the low pass filter in the I-V conversion stage set to around 20 MHz (10 pF capacitor and 787 Ohm resistor).
My problem is that when I examine the output, I do not see oscillations that resemble the result of mixing (baseband signal + sinusoidal waveforms at twice the of the local oscillator signal). Since my baseband signal is DC, I expected my outputs for I and Q channels to be DC + sinusoids at twice the RF frequency. Instead, at the output of the I-V conversion stage, the simulation does not produce what I expected. There are oscillations but they are not sinusoidal.
When I modulate the amplitude of the RF signal with a 1 MHz baseband signal, I still have a similar problem.
This is my first time working with this part. I do not know if these are the outputs I should expect or if I a making an error with my simulation.
I have looked at previous posts about similar problems but the threads appear to have been closed but the solutions were not provided there.
I would be grateful for any help.
I am attaching a zipped folder of my LTspice XVII schematic, as well as the spice models of the parts I have used in the simulation.
Thanks. 4353.ad8333 test.zip
