Author Topic: ERASynth: Open Source RF Signal Generator - Request for Feedback  (Read 2240 times)

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Offline edensrock

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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
 

Offline Rick

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #1 on: May 19, 2017, 10:17:18 AM »
You need to send a free sample to Dave and he might review it if he is in good mood... Cheers.
« Last Edit: May 19, 2017, 10:45:26 AM by Rick »
 

Online KE5FX

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #2 on: May 19, 2017, 11:08:41 AM »
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.
« Last Edit: May 19, 2017, 11:11:04 AM by KE5FX »
 

Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #3 on: May 19, 2017, 06:30:17 PM »
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.

 

Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #4 on: May 19, 2017, 07:24:19 PM »
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.
 

Online hendorog

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #5 on: May 24, 2017, 08:03:54 PM »
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.




 

Offline awallin

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #6 on: May 25, 2017, 12:00:23 AM »

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?  :-//
 

Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #7 on: May 25, 2017, 01:39:44 AM »
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.
 
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Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #8 on: May 25, 2017, 02:16:45 AM »
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?  :-//
 

Online hendorog

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #9 on: May 25, 2017, 06:42:43 AM »
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.
 

Online KE5FX

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #10 on: May 25, 2017, 11:09:06 AM »
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.
 

Online hendorog

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #11 on: May 25, 2017, 12:08:32 PM »
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.
 

Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #12 on: May 25, 2017, 05:07:04 PM »
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.
 

Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #13 on: May 25, 2017, 05:21:23 PM »
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.
« Last Edit: May 25, 2017, 05:53:09 PM by edensrock »
 

Online orin

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #14 on: June 07, 2017, 03:09:33 PM »
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.
 

Offline edensrock

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Re: ERASynth: Open Source RF Signal Generator - Request for Feedback
« Reply #15 on: June 08, 2017, 04:16:55 AM »
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.
 


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