Really thank you for your help.
I am struggling with the application of AD8333.
I am confused that when I input 4*LO sine wave to Din of DS90C401, its output (Dout-, Dout+) was not a sine wave. Even though I adjust the amplitude of the input. It still could not work.
I don't how to solve this issue.
The purple trace with a sine wave is the input to Din of DS90C401，but the other two traces were Dout(+, -). I don't know why they were not sinewave.
Thanks for your kind help
Can you provide a schematic of your circuit? Do you have the transimpedance amplifiers on the outputs of the AD8333? See Figure 64 in the AD8333 datasheet as a reference.
I am very grateful for your kind reply. I actually followed the reference design of the AD8333 datasheet. I firstly simulated this circuit in Multism, but it seemed to have problems that are shown below.
As the figure above, I input a reference signal with 4MHz(sinewave) to 4LO directly, and I set Reset to a high level. RFIP and RFIN were a pair of differential signals which were converted by the previous VGA circuit. The output was as follows. In fact, It did not accomplish I/Q demodulation when I set Reset to High.
However, when I put Reset to a Low level. It seemed to work with 2Lo signal plus DC component, but its signal was definitely weird, like below.
In addition, I also made an AD8333 circuit board without the previous VGA differential conversion module because I did that on another board in advance. According to the official recommendation, I used LVDS DS90C401 before my input reference signal entered 4LO. I looked up a lot of articles that told me the LVDS was used to process a digital signal instead of an analog signal. So I was confused that if 4LO's input should be an analog or digital signal. If it is a digital signal like a square wave, how they perform the mixing operation? The following figure shows the schematic.
When I changed a sine wave as the reference and I canceled the connection of DS90C401. The output was still wrong. I/Q could not track the tested signal's amplitude or phase.
I am really upset about its application because I have spent plenty of time to study it. But the outcome was always filled with errors.
What is the DC common-mode of the LO in the above schematic?
In your first screenshot, it looks like the Dout(+,-) are going below ground. Where are these points being measured? The LO common-mode voltage range for the AD8333 is 0.2V to 3.8V.