Rohde and Schwarz AMIQ Modulation Generator Teardown

Summary

Introduction Every few months, a local company auctions off all kinds of lab, production and test equipment. I shouldn’t be subscribed to their email list but I am, and that’s one way I end up with more stuff that I don’t really need. During a recent auction, I got my hands on a Rohde & Schwarz AMIQ, an I/Q modulation generator, for a grand total of $45. Add to that another 30% for the auction fee and taxes and you’re still paying much less than what others would pay for a round of golf? But instead of one morning of fun, this thing has the potential to keep me busy for many weekends, so what a deal! (Click to enlarge) A few days after “winning” the auction, I drove to a dark dungeon of a warehouse in San Jose to pick up the loot. The AMIQ has a power on/off button and 3 LEDs and that’s in terms of user interface. There are no dials, there’s no display. So without any other options, I simply powered it up and I was immediately greeted by the ominous clicking of a hard drive. I was right: this thing would keep me entertained for at least a little bit! (Click to enlarge) It took a significant amount of effort to restore the machine back to its working state. I’ll write about that in future blog posts, but let’s start with an overview of the functionality and a teardown of the R&S AMIQ and then deep dive into some of its analog circuits. AMIQ prices on eBay vary wildly, from $129 to $2600 at the time of writing this. Even if you get one of the higher priced ones, you should expect to get a unit that’s close to failing due to leaking capacitors and a flaky harddrive! The Rohde & Schwarz AMIQ Modulation Generator Reduced to an elevator sales pitch, the AMIQ is a 2-channel arbitrary waveform generator (AWG) with a deep sample buffer. That’s it! It has a streaming buffer that feeds samples to 2 14-bit DACs at a sample rate of up to 105MHz. Two output channels I and Q will typically contain quadrature modulation signals that are sent to an RF vector signal generator such as...