AD8333 - AD8332 interfacing

 

Hi,

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.

SDR1.PDF
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  • Hi Filep,

    Thanks for the email. You definitely cannot use the AD8333 negative outputs, these shouldn't have been pinned out.

    You will need a SE-to-differential conversion of some kind. I've used the ds90c401 in certain applications, and it should work in this instance as well. ADI has a lot of SE-DIF parts for interfacing any kind of single-ended output to pretty much any differential-input device. These are new parts so you might find something that better meets your needs. Check out the ADA4932, copy of data sheet attached.

    Good Luck,

    js

    ADA4932-1_4932-2.pdf
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