AWG input to RF Sig Generator - Page 1
Forum section: electronics / beginners

author: dc101
author_rank: Regular Contributor
timestamp: August 16, 2012, 02:49:29 am
content: I was wondering if there's any RF experts out there that could help me with a question about AWG/function generators and RF signal generators.I was looking at the new Rigol DG4000 function generator and saw all the fancy modulation types is could and was wondering if there was any way to input this to an RF signal generator as a modulation source. The idea being that since the DG4000 is limited to 160MHz (I believe) you could use it as a modulation source for a 1.2 GHz (just for example) signal being generated by the RF signal generator. The end result being a 1.2GHz signal that's modulated by whatever method chosen by the DG4000. Do RF signal generators support this kind of set up? Or would this have to be done using an off the shelf mixer (ie mini-circuits) using the RF sig generator as the LO and the DG4000 as the mod source? I was thinking that if you went the external mixer route that your signal might be messed up, because the DG4000 would be outputting a carrier that's already modulated and then it's getting mixed w/another carrier. It's also possible that I don't understand RF theory as much as I thought I didRegards,-Tim

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 01:57:41 pm
content: Welcome to the forumI don't know squat about RF but I suggest picking a signal generator that you think might be capable of external modulation input and downloading the manual and making sure it will do what you want and that the impedances can be matched. Not trying to be sarcastic, just seems logical.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 16, 2012, 02:01:42 pm
content: Even if you could output the modulating signal from the DG4000 you would need a signal generator capable of modulating his output in all the different ways, so AM, FM, PM, Pulse, USB, LSB, DSB... Can't recall exactly what the DG can do but you get the point. Mixing is the way to go

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 02:24:29 pm
content: I looked at several RF sig gen manuals and all allowed external modulation at least FM and AM and some allowed 2 simultaneous modulation inputs. You would probably just need a 50 Ohm feed thruough terminator since all the modulation inputs were way above 50 ohm.

author: dc101
author_rank: Regular Contributor
timestamp: August 17, 2012, 01:29:01 am
content: Thanks for the input guys, and thanks for welcoming me to the forum. I've been a long time listener of Dave, but this is obviously my first time checking out the forums.I'll keep an eye out on the input impedance, it's something that I hadn't been paying attention too before.

author: w2aew
author_rank: Super Contributor
timestamp: August 17, 2012, 04:51:05 pm
content: Quote from: dc101 on August 17, 2012, 01:29:01 amNote that more expensive RF sig gens may also include I&Q inputs. This allows you to input baseband IQ signals which will then be quadrature modulated to the RF output. This opens up the possibilities of much more complex modulation than simple AM/FM/PM, provided your ARB can generate the required I and Q signals.