Signal generator up to 3GHz for phase coding - Page 1
Forum section: electronics / testgear

author: tchiwam
author_rank: Regular Contributor
timestamp: January 14, 2021, 03:09:38 am
content: Anyone here knows a signal generator that can change phase 0, 180 deg at 1 or 2MHz rate ? Doesn't need to be new...

author: joeqsmith
author_rank: Super Contributor
timestamp: January 14, 2021, 04:51:49 am
content: So, the signal is always 3GHz and always 0 or 180 degrees and you just want to be able to modulate the phase at 1MHz or 2MHz and there are no other requirements, anything goes? You don't care about noise, amplitude, stability, features, cost... Is the phase control fixed at the 1MHz or 2MHz rate, 50% DC and always active?Maybe you could provide some basic details.

author: bdunham7
author_rank: Super Contributor
timestamp: January 14, 2021, 05:16:59 am
content: Are you referring to BPSK? Or something similar? There should be some old boat anchors that support BPSK, but if you want something like that at 3GHz, it will get more expensive.HP/Agilent has a whole slew of these, but I haven't had one with 3GHz capability.The R&S SMV03 and SM300 support phase modulation and go over 3GHZ, but unless I know what you are doing (what your modulation signal looks like, exactly) I can't say for sure they will do what you want.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 14, 2021, 05:17:13 am
content: Maybe you could use an external modulator like this?https://www.analog.com/en/technical-articles/bpsk-modulator-for-2ghz-to-12ghz.html#

author: joeqsmith
author_rank: Super Contributor
timestamp: January 14, 2021, 05:22:02 am
content: I just assumed they were referring to BPSK. Maybe something like this?https://signalhound.com/products/vsg60a-6-ghz-vector-signal-generator/Even my cheapo ARB can do the 2MHz modulation but won't quite make it to 3GHz. Close.

author: KE5FX
author_rank: Super Contributor
timestamp: January 14, 2021, 05:47:12 am
content: Seconded, the VSG60A works very well. You could do the same thing with a much less expensive SDR such as a USRP, bladeRF or similar, but the Signal Hound unit will be much more straightforward to set up.

author: colorado.rob
author_rank: Frequent Contributor
timestamp: January 14, 2021, 08:51:45 pm
content: PlutoSDR -- $150 new from Digikey.

author: KE5FX
author_rank: Super Contributor
timestamp: January 14, 2021, 09:14:18 pm
content: Quote from: colorado.rob on January 14, 2021, 08:51:45 pmPossible. If they had only added a 10 MHz reference input to that thing, it would have been a real game-changer.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 15, 2021, 01:35:00 am
content: Showing my Arb at 2GHz, 1MHz symbol rate sending 5's.Also shown is my RF generator at 1GHZ. A trippler was used to get the 3GHz carrier. This was filtered and then mixed with my function generator to get the BPSK. It's no problem to run with a symbol rate of 2MHz.

author: tchiwam
author_rank: Regular Contributor
timestamp: January 15, 2021, 02:42:03 pm
content: I do need something at least frequency locked, phased locked is prefered.I was thinking about IF modulation and up sampling. The DC-6GHz with 2X output did get my attention, as this would allow for more than 180deg binary coding. I'll at least make a test board with a LTC5548Reading the specs of my 8664A/8665B I thought it could do it, but I am limited to about 100kHz... I was thinking about going down the chain and removing the BP filter, or it might be simply out of wack too...I Have a USRPB200 mini and a HackRF and I know I can use those but the output quality is hmmm, interesting.Yeah, having a common clock is rather important, many devices are without it and that's very frustrating, or they can only take a non trivial level, that's why I read all the specs. Not all SDR can take a nice +7dBm 10MHz even if they have a very tempting Ref In SMA connector. Some want a square wave to behave other want a sine, some are defined in the specs, some are for you to discover.

author: KE5FX
author_rank: Super Contributor
timestamp: January 15, 2021, 10:52:29 pm
content: Don't sell the USRP short, there are some real advantages to integration of the whole complex upconversion chain on one die.I use two different vector signal generators pretty regularly, a VSG60A and one of the original bladeRF x40 SDRs. The VSG60A puts out a very clean signal with its LMX2594-based LO and dedicated I/Q modulators (ADL5386/ADL5375), but the warmup characteristics and overall phase stability are better with the cheaper and (much) dirtier LMS6002D in the original bladeRF because everything runs at the same temperature. The VSG60A needs a couple of hours of warmup time, preferably with an actual signal going through it, before it reaches optimum phase stability.Both are capable of decent EVM performance in a communications application. It was a big pain in the neck to modify the bladeRF to run synchronously from 10 MHz, of course, while the Signal Hound makes it easy. The AD9364 in the USRP should be a great middle ground, just a matter of finding or writing the code to generate the signal you need.