I am developing a SDR receiver as my bachelor thesis. I am new in hardware design.
This is expected block schema:
I am using SDR concept, which is based on I/Q demodulator (AD8333) for mixing RF frequency to baseband.
Then is signal sampled by A/D converter on 1,5 MSPS (ADS7851) and send to pc.
But I have some problems with interfacing AD8332 and AD8333. According to AD8333 datasheet example is AD8332 LNA connected to AD8333. After mixing are I/Q rails connected to transimpendance amplifiers for converting currents to voltage. So, I have single ended signal. But I need to connect this signal back to AD8332 - VGA, which has differential input. Can I simple use an LVDS driver such as ds90c401?
Or it is possible to use negative I/Q Outputs?
My schematic - working version attached.
Can you please elaborate on unusability of AD8883 negative outputs?
I have not found not a single mention about this in whole datasheet and related documentation. In case that output current mirrors are disabled by connecting VNEG to ground and output swing is limitied within 0,6Vpp (to avoid distortion by ESD clamps/BJTs) it should be perfectly fine - or am I mistanken? I have whole signal chain designed as fully differential, so this would mean major issue for me.