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ERASynth: Open Source RF Signal Generator - Request for Feedback
Posted by edensrock on 14 May, 2017 18:19 -
Hi everyone,
We are running our crowdfund campaign ERASynth on CrowdSupply. We would like to see your valuable feedback and recommendations. Your comments are very important since we are still in the process of taping out last revision of the board.
Thanks in advance.
edensrock -
You need to send a free sample to Dave and he might review it if he is in good mood... Cheers.
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Hi everyone,
We are running our crowdfund campaign ERASynth on CrowdSupply. We would like to see your valuable feedback and recommendations. Your comments are very important since we are still in the process of taping out last revision of the board.
Thanks in advance.
edensrock
Hey, this really does look cool. -125 dBc/Hz at 10 kHz from a 1 GHz carrier out of an ADF4356 is pretty impressive.
It's good to see so much technical detail up front. Good luck with the Kickstarter!
Some brief thoughts:
- If you use a DDS anywhere in the design, consider adding an LF output path for it. It'd be nice to offer 9 kHz-15 GHz coverage, or even lower. Not a huge deal but occasionally useful.
- Offer a version on your Kickstarter without the OCXO. Many of your customers will have their own stable 10 MHz references available, so it's a waste of money to include OCXOs at the instrument level.
- Lack of ALC is probably the biggest Achilles' heel I see. Calibrated and leveled output power is pretty important. I'd suggest prioritizing this in the next spin.
- LMX2594 just came out. Could be worth looking at, but it sounds like you're getting similar performance from the ADF4356 already, so maybe not.
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We are planning on sending one unit to Dave for Monday mailbag once we finish the final revision.
You need to send a free sample to Dave and he might review it if he is in good mood... Cheers.
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Thank you KE5FX for insightful suggestions
We are not getting -125dBc/Hz PN out of ADF4356. We used ADF4356 + LTC6945 combination as the main PLL plus HMC830 as the tunable reference generator to get -120 dBc/Hz in our current revision. At that time, LMX2594 wasn't around (we started this project in August 2016). Just before the launch of our campaign, TI released LMX2594, and it was scary good (*). We were going to do one final revision anyway, so we decided to use LMX2594 as the main PLL as well as the tunable reference generator. We purchased two copies of the LMX25945 the eval board and tested to see everything was inline with the datasheet, and it was. Here is the block diagram of both current revision and the final revision of ERASynth:
http://erainstruments.com/erasynth/erasynth-current-block.png
http://erainstruments.com/erasynth/erasynth-final-block.png
The phase noise graphs shown on the campaign page were taken with our current revision. Hence, tunable ref is HMC830, VCO is the VCO of ADF4356 and Int-N PLL is LTC6945. You may see the PN graphs here:
https://www.crowdsupply.com/img/35ff/erasynth-pn-10ghz.png
https://www.crowdsupply.com/img/f040/erasynth-pn-1ghz.png
These are respectable numbers to squeeze out of ADF4356. Yet, we are targeting another 5 dB improvement (in the pedestal region) over these numbers in the final revision.
We will be using a DDS to go down as much as possible in the plus version in the final revision, we are planning on using AD9913. We will consider adding an LF output. It will require an extra SMA connector, which may not be possible. We will see what we can do when we do the final layout.
There is a model on the campaign without the OCXO, but it only goes up to 6 GHz. However, both of the ERASynth models also accept external 10 MHz reference signal. If you have your own more stable 10MHz signal you may use it. Default inclusion of the OCXO just increased the cost a little bit, but people who doesn't have their own ultrastable timebase will appreciate it.
As for ALC, it is really beyond the scope of this project. Open loop calibration doesn't mean that the amplitude accuracy will be all over the place. At the moment, we are doing tests to see how our open loop calibration performs. We will publish the results as an upcoming campaign update. Please follow our campaign page for updates.
(*) LMX2594 has the best flat phase noise FOM -236dBc/Hz in the industry at the moment. However, LTC6945 is still better when it comes to flicker FOM (Flicker FOMs: LTC6945=-274dBc/Hz vs LMX2594=-269dBc/Hz).Hi everyone,
We are running our crowdfund campaign ERASynth on CrowdSupply. We would like to see your valuable feedback and recommendations. Your comments are very important since we are still in the process of taping out last revision of the board.
Thanks in advance.
edensrock
Hey, this really does look cool. -125 dBc/Hz at 10 kHz from a 1 GHz carrier out of an ADF4356 is pretty impressive. It's good to see so much technical detail up front. Good luck with the Kickstarter!
Some brief thoughts:
- If you use a DDS anywhere in the design, consider adding an LF output path for it. It'd be nice to offer 9 kHz-15 GHz coverage, or even lower. Not a huge deal but occasionally useful.
- Offer a version on your Kickstarter without the OCXO. Many of your customers will have their own stable 10 MHz references available, so it's a waste of money to include OCXOs at the instrument level.
- Lack of ALC is probably the biggest Achilles' heel I see. Calibrated and leveled output power is pretty important. I'd suggest prioritizing this in the next spin.
- LMX2594 just came out. Could be worth looking at, but it sounds like you're getting similar performance from the ADF4356 already, so maybe not. -
Cool project and impressive specs!
My ideas (based on the final block diagram):
Use the/a DDS for the < 10MHz output, which frees up RF Out A to be differential - so now you can use a balun on RF Out A to reduce the 2nd harmonic on the <6GHz output.
Expose the SYNC pin of the LMX2594 so that multiple devices can be made phase coherent.
Expose the RAMPCLK, RAMPDIR and MUXOUT (for Ramp Status) pins too.
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I'm too lazy to read the fine-print myself, can someone clarify what happens with a Crowd Supply project if I back it but then the supplier fails to deliver?
Any guarantees at all that I will get anything if I now feel like I have about $750 extra in the bank?
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hendorog,
Thanks for the valuable feedback
We are going to use the DDS but probably cannot do the balun. I am not aware of any single balun (with reasonable cost) that can cover 10 MHz to 6 GHz. Besides, our tests on the LMX2594 eval board showed good results for 2nd harmonic. The -10 dBc typical value given in the campaign page was mainly due to 3rd harmonic.
We are going to consider to expose SYNC and MUXOUT pins. For ramping we have a multi-purpose trigger input, same functionality can be implemented using the trigger pin + GUI.Cool project and impressive specs!
My ideas (based on the final block diagram):
Use the/a DDS for the < 10MHz output, which frees up RF Out A to be differential - so now you can use a balun on RF Out A to reduce the 2nd harmonic on the <6GHz output.
Expose the SYNC pin of the LMX2594 so that multiple devices can be made phase coherent.
Expose the RAMPCLK, RAMPDIR and MUXOUT (for Ramp Status) pins too. -
awallin,
As far as I know Crowd Supply is the only crowdfunding site with 100% delivery rate. We -as ERA Instruments- have no intention of destroying that reputation. We already have a working prototype and will do our best to deliver the best possible product to our backers. Although the prices shown on the campaign page might seem high for a crowd-funded project, we are not really making any profit in this project. RF components are not cheap. Just the main PLL IC on our final BOM (LMX2594) costs more than $50 (and we are using two of these in a single ERASynth).
Then, why are we doing this project? We have been working as consultant to some local defense companies in Turkey for several years. This project is our first attempt to create our own business. We would like build a good global reputation. Not delivering would defeat the whole purpose of doing it.
I'm too lazy to read the fine-print myself, can someone clarify what happens with a Crowd Supply project if I back it but then the supplier fails to deliver?
Any guarantees at all that I will get anything if I now feel like I have about $750 extra in the bank? -
Another idea - I'm sure you have already considered this, but how about another option without the case?
I know performance would suffer but it should allow a decent price reduction, and so get the price down enough to engage DIY/maker types.
I was thinking a reference design for a 3d printer could be published on thingiverse. Printing and internal shielding done with copper tape by the purchaser.
The pricing of the ERASynth is just a bit higher than what a maker would go for. -
We are going to use the DDS but probably cannot do the balun. I am not aware of any single balun (with reasonable cost) that can cover 10 MHz to 6 GHz.
You could use a Mini-Circuits TCM1-63-AX+ or TCM1-83-AX+, but if the goal is to cut down on harmonic output, one of their inexpensive ceramic filters would make more sense. The only real advantage to the balun would be a couple dB more power output.
Harmonic content can actually be kind of useful with these chips, so I don't know that I would go out of my way to suppress it. The user can always add a filter of their own. -
We are going to use the DDS but probably cannot do the balun. I am not aware of any single balun (with reasonable cost) that can cover 10 MHz to 6 GHz.
You could use a Mini-Circuits TCM1-63-AX+ or TCM1-83-AX+, but if the goal is to cut down on harmonic output, one of their inexpensive ceramic filters would make more sense. The only real advantage to the balun would be a couple dB more power output.
Harmonic content can actually be kind of useful with these chips, so I don't know that I would go out of my way to suppress it. The user can always add a filter of their own.
Yeah those were the baluns I was thinking of. Whether they are resonably priced is open to discussion
The even harmonics should theoretically be perfectly cancelled as they are in phase at the balun input.
Also the 2nd harmonic of the < 6ghz fundamental under discussion wouldn't be useful either as there would still be the 6-15ghz output available.
But of course no point given the odd harmonics dominate. -
KE5FX,
These are nice baluns but as you said several lower cost (such as LFCN series) filters would make more sense. As Jorgesen and Marki pointed out in Marki Microwave's Balun Primer, the max rejection we can get out of these baluns is about 15 to 25dB with the values given for the phase and amplitude imbalance values. We can easily get more from inexpensive filters. If we decide to use filters, it will also require using switches since we cannot use a single filter over a multi-octave range. That will further increase the BOM and complicate the board. Just as you said we think it is best to leave it to user to reject the harmonics with their own external filters.We are going to use the DDS but probably cannot do the balun. I am not aware of any single balun (with reasonable cost) that can cover 10 MHz to 6 GHz.
You could use a Mini-Circuits TCM1-63-AX+ or TCM1-83-AX+, but if the goal is to cut down on harmonic output, one of their inexpensive ceramic filters would make more sense. The only real advantage to the balun would be a couple dB more power output.
Harmonic content can actually be kind of useful with these chips, so I don't know that I would go out of my way to suppress it. The user can always add a filter of their own. -
hendorog,
We have seen other projects where only the board (even unpopulated boards) are offered as options. We didn't do that because -as you said- performance would take a huge blow without the case.Another idea - I'm sure you have already considered this, but how about another option without the case?
I know performance would suffer but it should allow a decent price reduction, and so get the price down enough to engage DIY/maker types.
I was thinking a reference design for a 3d printer could be published on thingiverse. Printing and internal shielding done with copper tape by the purchaser.
The pricing of the ERASynth is just a bit higher than what a maker would go for. -
edensrock,
This looks really nice. I'd wondered about the concept of using the modern RF chips to make a sig gen... and you've gone and done it!
I've put my 'order' in and hope you make your target!
Orin. -
Orin,
Thank you very much for your support. We are now at 97%. Almost there edensrock,
This looks really nice. I'd wondered about the concept of using the modern RF chips to make a sig gen... and you've gone and done it!
I've put my 'order' in and hope you make your target!
Orin. -
edensrock,
What is going on with the project? The last post on EEVBlog forum was in the beginning of June, the last post on Crowdsupply, in which ERA team promised frequent updates, was on the last day of the campaign, and not a word since then. Is the project still alive? Are you planning to deliver ERASynths to backers? -
You can look at the time plan on the crowdsupply website.
I think it says September 21 is when they plan to ship to backers.
With 25 weeks lead time on some components and no visible buffer time planned for 'things that can go wrong'I'd be surprised if you'll get it this year
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I am familiar with their schedule and, based on my experience from other crowdfunded project, I don't expect the units to ship on time. I'm not blaming anybody, I realize that it's very hard to set specific date of delivery ahead of time.
However, the sudden drop of updates on the day when the funding campaign closed, from a team who have been very active and very open in their communication to the investors, and who promised frequent updates in their last message, is quite unsettling. -
Why have you added wi-fi to this unit? I can't possibly understand why a device that has been designed to output a pure monochromatic signal has another radio stuck in it somewhere. I'd be a fan of adding ethernet, but definitely not wi-fi.
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Update! looks like they have sent the products to the crowdsupply facilities in Portland:
https://www.crowdsupply.com/era-instruments/erasynth/updates/erasynths-on-their-way-to-crowd-supply
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Got my ship notice this morning. Looking forward to using this in numerous projects.
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I've just got my unit. Looks super solid and sturdy. Powers up, blinks the lights. Next challenge: finding the documentation how to connect
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I've just got my unit. Looks super solid and sturdy. Powers up, blinks the lights. Next challenge: finding the documentation how to connect
PDF with user guide linked on crowdsupply page does not work, but all docs are available on github: https://github.com/erainstruments/ -
Mine arrived yesterday.
I could not get the wifi hotspot to work correctly. It showed up, but connecting to it took a long time and once connected, the UI took minutes to show up and was unresponsive.
I used the serial interface to switch to wifi station mode and it seems to be working OK now.