DAC AD9115 with ADRF6720-27

Question

I have implemented the DC blocking capacitor as shown on a previous post to create the level shift at 2.7V. 
 https://ez.analog.com/rf/f/q-a/72214/adrf6720-27-rfoutput-problem/168465#168465 
 I am seeing some ringing on the Vector Signal Analyzer on the burst power output. Attached are the pictures of the VSA output and the IQ waveforms into the modulator.

THA · Accepted Answer

Hello, 
 It looks baseband inputs to ADRF6720-27 are the modulated signal. I suggest to check it with a CW single-tone (few MHz) and check four inputs at phase/amplitude. 
 what is CH3 on your screen shot? Is it enable signal to transmit signal? 
 Is ADRF6720-27 and level shifter all time on and just control baseband inputs on/off? I am not sure if we can see any abnormal operation (like ringing in 200us range) on spectrum analyzer but can you try to check output spectrum with spectrum analyzer? 
 I don't think DC blocking capacitor causes this ringing. Let's see how it looks like with a CW tone. 
 For ADRF6720 with AD9115 DAC, 
 Set full scale 20mA on AD9115 and 10mA midscale with set 500mV with 50 ohm termination on DAC. 
 Thanks 
 Tony

THA · Answer

It is good to hear ADRF6720 works. 
 FYI, If you consider ADRF6720-27, it can interface to AD9152/54 directly without a level shifter. 
 
 Thanks 
 Tony

Electronic Design Services - PartnerZone

DAC AD9115 with ADRF6720-27

Top Replies