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Need reasonably priced (i.e. cheap) signal generator with low phase noise
Posted by Leo Bodnar on 13 Dec, 2018 20:03 -
I am looking for low phase noise benchtop signal generator for use in day-to-day phase noise measurements. I still haven't found what I'm looking for.
Here are my rough criteria:
10MHz..1GHz range. More is better
+7..+15dBm output
External frequency control (FM with DC coupling) or internal reference tuning input. 10Hz BW and few ppm is enough
10MHz carrier phase noise: 10dB better than attached chart
1GHz carrier phase noise:–90dBc/Hz at 10Hz, –120dBc/Hz at 1kHz offset, –150dBc/Hz at 100kHz offset
Higher carrier frequencies are OK to follow 20dB/decade degradation rule.
Not more than £2k from eBay in fully working shape (to be able to use two for cross-check tests)
I have a few Agilent ESG-AP and ESG-DP series but they are not very impressive below 250MHz where they start heterodyning the output. R&S SM300 and few Marconis that I have tested are way off too.
Would Aeroflex/IFR/Marconi 2040, 2041, 2042 or R&S be anywhere close?
If you have any generator phase noise graphs you took please drop it in this thread - even if they are noisy. This makes selection process much easier.
Cheers
Leo
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The SSG3021X (2.1 GHz) is 2k Euro new.
Phase noise graph on P8 in the datasheet:
https://www.siglenteu.com/wp-content/uploads/dlm_uploads/2018/11/SSG3000X_DataSheet.pdf -
HP8662A?
EDIT: not easy to reach, your requirements... -
HP8662A is good for close-in noise but a bit rubbish at 100kHz.
Siglent is a bit rubbish throughout for XXI century instrument. It also does not seem to have DC coupling on FM mod input. Datasheet says "10 Hz~100 kHz" which makes it unusable as controlled signal source in PLL loop.
I'd like to test HP8644A someday but they weigh a tonne and still too expensive to impulse-buy.
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What about a 8642A? Got one of those inbound...
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not easy to reach, your requirements...
Flukes are close but they are very rare and very expensive - even used.
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HP 8662A/8663A is best at low phase noise close to carrier.
HP 8642B is better at low phase noise far away.
I have a couple of HP8662As and they are far superior to other HP instruments such as HP 8656B/8657B (sold them already) and nowadays digital DDS rubbish from china.
http://hpmemoryproject.org/technics/bench/3048/config_hard_01.htm
Apparently, HP8642B has lots of SAW filter magic inside and I hate HP LCDs, (particularity the HP3457 display) so I didn't get one already. Also weights a ton (I think even more than HP8663A), so it's expensive to ship
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Doesn't fit your requirements, but there's a chart in the spec sheet:
http://wunderkis.de/mg3633a/manual/
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What about a 8642A? Got one of those inbound...
8642A is good at 1kHz and further out but rubbish at close-in. I have seen HP recommending using both 8642A and 8662 and patching together measurements. It's a bit too much for a small lab.
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Thanks. Close in noise is not the best but otherwise not bad.
Doesn't fit your requirements, but there's a chart in the spec sheet:
http://wunderkis.de/mg3633a/manual/
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Marconi 2041
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What about a 8642A? Got one of those inbound...
8642A is good at 1kHz and further out but rubbish at close-in. I have seen HP recommending using both 8642A and 8662 and patching together measurements. It's a bit too much for a small lab.
Too much gear? What have you been smokin' son? -
I have a Hameg-HM8135 which is about 30dB above your required level! (it was cheap though at £400 for new-old stock):
https://www.testwall.com/wp-content/uploads/2016/10/Hameg-HM8135.pdf
Your requirements are very demanding especially at 1GHz. Looking at SAW oscillators such as the crystek ones mentioned above :
https://www.digikey.co.uk/product-detail/en/crystek-corporation/CRBSCS-01-1000.000/744-1659-ND/4741148
its output is too noisy and it is designed as a low phase noise test source!
Your 10MHz requirements are more reasonable at least compared with low noise OCXOs.
If you use the cross-correlation approach to phase noise measurement then this reduces the noise requirements on the references:
http://www.holzworth.com/Aux_docs/Holz_MWJ_TechFeat_Feb2011.pdf
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Thanks. Close in noise is not the best but otherwise not bad.
I don't have a proper phase noise analyzer, yet I'm pretty confident the MG3633A is about the best you can get and its close-in phase noise is actually much better than indicated by the graph in the data sheet. Here's a phase noise measurement at 1GHz, actually showing the phase noise of the analyzer rather than the MG3633A, but still indicating a much lower phase noise below 60Hz than what would be expected from the data sheet graph.Doesn't fit your requirements, but there's a chart in the spec sheet:
http://wunderkis.de/mg3633a/manual/
Also at 10MHz, the MG3633A should be at least 5dB better than the plot you've shown. I know, you want 10dB and it might well be that the MG3633A can deliver that, I'm just unable to verify it.
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Gigatronic's 2400 series generators advertise low phase noise but don't even come close to some of your specifications (a table in the datasheet)... maybe their newer stuff fares better, but it's not going to qualify as cheap and they've essentially ended any kind of support for their non-current model generators, which is frustrating.
I think you can find low phase noise in that budget to 1GHz, I don't think you can find phase noise class you're looking for in that range unless you find a steal. -
I'm fairly convinced that there are no signal generators that meet your requirements. The Phase Matrix QuickSyns are generally lauded for their phase noise performance but are 10 dB short of your 1 GHz 100kHz offset number, even used they'd probably be >$2k.
The Holtzworth HSX are the same.
Though the just "scrape by" at 10 MHz.
It sounds like you need a cross-correlation based phase noise system. That way the reference sources can be above your DUT's phase noise by a few dB. The Holtzworth analyzers do this and can measure far below your requirements.
http://www.holzworth.com/Spec_sheets/HA7062C_Web_Datasheet.pdf
The Erasynth generators meet your price requirement and are solidly competitive with the above signal generators in performance. I've wanted to build a phase noise analyzer using cross correlation for some time but it keeps slipping on the project list. I'd use Erasynths or similar in that case. -
Does anyone have a full DS for an R&S SMHU? Seems like it should be pretty good, but I only have the two-pager on the internets.
I have one. Albeit with a PSU that I've blown. Twice. -
-90 dBc/Hz at 10 Hz from a 1 GHz carrier is a tall order. To this day I'm unaware of anything on the market with lower close-in noise than an 8662A, and it will just barely meet that requirement if you get a good one that outperforms its 'typical' specs by a couple dBc/Hz.
Pro tip: spend a bit more for an 8663A, and buy two of them, and then buy another for a parts mule... and as you note, this will provide good close-in noise at the expense of poor broadband noise. An 8663A and 8642B make a good combination in that respect.
Basically, getting all of that stuff from a single synthesizer is going to cost about as much as a new Jaguar. You're much better off using separate sources for different measurements. Or put together a cross-correlating rig; see this thesis and attached articles by Simon Bale for some good pointers there. -
The idea of having a spare 866x for replacement parts is a good one.
When I compare my 8662A to my SMPD and SMIQ4, there is
one clear loser: the 8662A. Most time, it has some "issues".
currently, it works from 0 to 160 MHz, works not from 160 to 320,
works again for 160 MHz and so on. Sick of repairing it; I have
alternatives and it collects dust in a corner.
For close-in noise the choice is crystal oscillators anyway.
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to complete the two pages, taken from U. Rohde: Microwave & wireless synthesizers, J.Wiley
I think that U.Rohde is preparing an update with E.Rubiola; at this price level you might want to avoid
the double expense.
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Adret 7100A won't meet your phase noise spec but it wasn't too bad for back in the day, 1978. I think Marconi aquired Adret and one family of Marconi synthesizers is based on the Adret design but I can't remember which one.
Adret 7100A phase noise at 160MHz
100Hz -87dBc/Hz
1kHz -117dBc/Hz
10kHz -136dBc/Hz
100kHz -136dBc/Hz
1MHz -145dBc/Hz
I will have to go and dig out my copy Frequency Synthesizers: Theory and Design by Vadim Manassewitsch and have a look at how double or triple mix/divide synthesizers performed back in the day. It's a brute force synthesis technique that was replaced by PLL synthesisizers but potentially has much better phase noise performance. Even with todays improved techniques the double or triple mix/divide synthesier will still cost a lot more than a PLL based synthesier. Just my 2 cents worth.
edit: DDS synthesis has improved a lot since the days of double or triple mix/divide techniques and high speed D-A converters are a lot smaller and cheaper these days. If you summed the signals from N D-A converters and assume the D-A converter noise is incoherent do you still get an N/root(N) SNR improvement. Paralleled amplifiers were used back in the day to get very low noise floors and in principle I don't see why you can't use the same technique for oscillators.
Now you've got me wondering if an injection locked oscillator has a lower phase noise than a free running oscillator, damn it.
Chris -
Now you've got me wondering if an injection locked oscillator has a lower phase noise than a free running oscillator, damn it.
Do you mean self-injection-locked via delay line? -
In Rohde, Poddar, Böck: The Design of modern microwave oscillators for wireless applications,
there is a whole section on the noise of n coupled oscillators.
More math than I'm willing to digest unless someone pays me for that.
Methinks Rohde has also written sth. on self-locking in Microwave journal last year.
cheers, Gerhard
(who would like to couple 16 MTI-260 crystal ovens, but forced by a slooow PLL. The oscillators
are here, time is mising. More like locking the 16 pcs. to a 17th and wilkinson the outputs together.) -
I've wanted to build a phase noise analyzer using cross correlation for some time but it keeps slipping on the project list. I'd use Erasynths or similar in that case.
I have the same fantasies here. The idea is to use some AD JESDI-204B 2GSPS ADCs,
an Artix FPGA and a BeagleboneBlack.
In a former project I had easy everyday access to to an E5052B, but now I'm hacking something
together centered around my Agilent 89441A FFT ( can do Xcorr...), ring mixers and a delay line
made from 6 1:6 coax relays and lots of SMA-Semi-Rigid that can enforce 90° delay for any
frequency between 5 and 100+ MHz. That SMA-soldering orgy is of great meditation value.
< https://www.flickr.com/photos/137684711@N07/40639478472/in/album-72157662535945536/lightbox/ >
Some of the coax relays had TTL drivers and I quickly found out why they did end up on ebay. :-(
I did grind them open, removed the drivers and switch the coils myself. They do not look pretty
any more.
regards, Gerhard