MicroControlled 3 Channel Sin Generator 0 ... 60 MHz

[Fraser]

Hi All,

I'm starting this thread to document my ongoing build of a 3 channel pure SIN generator.

Specs:

• 3 Channels (hopefully phase locked).
• 0 ... 60MHz with 1Hz resolution.
• 4V p2p into 50 Ohm.
• Microcontroller controlled.
• 3D sweeping capability (sweep width and resolution adjustable on each channel)
• When sweeping samples analog input signal in order to hunt for optimum power out.
• Ability to log scan results into PC over USB cable for analysis on PC in excel etc.

I already have a 2nd hand tektronix FG504 sig genny which is great and handy but the output, like most bench gennys, is NOT radio frequency quality, it is in fact VERY poor with regard to stability and purity.

The hard work I have purchased premade in the form of 3 x DDS60 modules, designed and used by amateur radio enthusiasts. The design has evolved over quite a few years and is very stable:

http://www.amqrp.org/kits/dds60/index.html

The modules will be under the control of an ATMega Microcontroller and JogWheel.

[Fraser]

Well, I've put a few hours into finishing the hardware for this generator, here's a quick youtube vid showing it covers off:

I'll post up another vid soon showing it in action on a scope and also listening to all three channels heterodyning with a sideband radio, some quite complex sounds can be heard.

[Peterae]

Nice work Fraser, a very nice build indeed 

You will be able to do some great bench work with this gen.

Look forward to seeing the results

Cheers,
Peter

[Fraser]

Thanks Peter! I´m pleased with it so far, but it won´t win a beauty contest , fingers crossed it´ll last a few years though and provide a nice stable frequency source for any experiments that need it.

The signal out the front BNCs is fairly clean and is very stable. Amazingly I´m able to tune 2 oscillators as close as possible and they drift thru a phase cycle say once every 4 seconds, so 0.25Hz drift at 50Mhz that´s 1 part in 200million!, proving these crystal oscillator clocks are real nice temperature compensated devices. Of course when I clock from one oscillator it will be zero phase drift.

Next step is to make comparitors that have variable fire level, looking at fast opamps, logic buffers and FETS bugbuilt onto solid copperclad board, i´m hoping to get to 50MHz with this approach, I know I can get to 30Mhz any higher will be a bonus. The 3 channel comparitor and amp module will be housed in the same type of case and stacked under the freq genny.


P.S.
I wonder if I should set up a bench board and move this subject there?

[Peterae]

Hi Fraser

I would certainly be very interested in an output stage with this capacility.

I would built each stage as a seperate board, that way it's just a matter of duplication.

If you wanted i can cad this up and make some double sided pcb's to send out to you.

Peter

[Fraser]

RE: power pulse generation stages.

That sounds great Peter! With a double sided board it will make thigs faster (both build time and faster risetimes). I would be wiling to order some (hopefuly all depending on price) of the silicon components in bulk, and post you a set, just add passive components and its complete.

We will aim for as powerful an amp stage as possible, with high peak pulse current being a primary criteria.

Impedance matching I will leave out, it's up to us to make that alongside any particular system under test because each application might have vastly different input impedances.

[Peterae]

Hi Fraser
Looking forward to it, i so need a better fet stage for my controller, so this will be very welcome.
Do you have a circuit for me to cad up, either PM me or post if you are going to open source it.

Cheers,
Peter

[Fraser]

I don´t have a final design yet. I want to use cheapish FETs and also have some isolation to protect my generator. I think 10ns rise and falls is something to aim for. Motorola do some real fast FETs but they´re a bit pricey so still scouting round.

When I get something working well on solid copper board I´ll photo it so you can CAD it up, that´d be great!

[Fraser]

I forgot to use the youtube embedd button you´ve put in Peter  : sorted now.

[c2]

Fraser,

Nice work on the signal generator(s). I found your video on YouTube looking for new Arduino projects to study.

What brought me to Arduino is a means to control a DDS signal source, and here you have programed simultaneous control of three such devices with such a simple, yet eloquent interface. It is impressive to me.

I'm wondering if you are interested in helping me with my development, mostly with Arduino code, which has proven to be the most difficult for me. would you be willing to share some of the code for the DDS control and jog wheel?

My initial project is to build a single output source with sweeping capabilities, level control, and an ability to phase lock to a GPS disciplined clock for absolute accuracy. Later I plan to work with a more sophisticated DDS that offers a variety of modulation capabilities.

I do look forward to seeing more of your triple source.

Thank you

[Fraser]

Hi C2,

Sorry for the delayed reply, I´ve been mad busy lately with other things and haven´t checked this thread in over a week. Welcome to this fairly new forum.

Fraser,

Nice work on the signal generator(s). I found your video on YouTube looking for new Arduino projects to study.

What brought me to Arduino is a means to control a DDS signal source, and here you have programed simultaneous control of three such devices with such a simple, yet eloquent interface. It is impressive to me.

Thanks for the nice words, I´m glad you like it!

I'm wondering if you are interested in helping me with my development, mostly with Arduino code, which has proven to be the most difficult for me. would you be willing to share some of the code for the DDS control and jog wheel?

Sure, provided you aren´t going to use this in a commercial product you can use or modify my source code (I will open source it and post it here as an attached file).

You should be able to rip out alot of my stuff and keep the core stuff you need, It´s fairly well commented but any questions let me know on this thread (then others can benefit from the info too).

Yes to get a jog wheel running nice you need to employ interrupts, this enables real fast response so no jogs are missed.

My initial project is to build a single output source with sweeping capabilities, level control, and an ability to phase lock to a GPS disciplined clock for absolute accuracy. Later I plan to work with a more sophisticated DDS that offers a variety of modulation capabilities.

Sounds interesting, is this for a homebrew radio rig you´re building?

Level control, how will you implement that? with some digitally controlled potentiometer? Interested to hear more.

Phase lock to GPS disciplined clock? again sounds interesting, any info on good chips and hardware to do this, I´d appreciate if you post it here. So seperate signal sources (over large distances) using this could mantain a perfect phase lock with no drifting whatsoever?

I do look forward to seeing more of your triple source. Thank you

I´ll try and do a video soon of it running on a scope and listening to all three freqs on a SSB receiver.

[Fraser]

Software release v1.01 (beta)

[c2]

Thank you, Fraser.

I do understand completely.

The GPS-DO concept was introduced to me at calibration laboratories. I've since discovered J. Miller designs as plausable. Here are some links to his documents:

http://www.jrmiller.demon.co.uk/projects/ministd/manual.pdf

http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm

And he sells this standard as well:

http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm

But I am an amateur radio enthusiast and enjoy the technology as a means of exploration and experimentation. I've always been interested in signal sources and various measurement devices such as spectrum analyzers and vector network analyzers. Another signficant project I've been pursuing is the N2PK VNA project:

http://n2pk.com/

I do not have specific objectives with these projects such as building a communications transceiver, but like to use the equipment to test and explore, mostly with antennas...

Thank you very much for offering open source code and I now find rejuvinated interest. Of course my projects too are open to collaborative interests. I've been sharing most of this on the Arduino forum, mostly with parsing NMEA data and for some code help (with the Arduino tinyGPS library), and it would be fun to share here as well.

[Fraser]

@C2,

Thanks for the info on GPS phase locking, amazing.
Also, N2PK VNA looks to be a powerful tool!

@All, moved this back here again  Sorry for flip flopping back and forth but I only just realised benches are only viewable by members so I'll keep it here, more in the public domain.

Bruce_TPU seems to be active again, shame he doesn't post over here, he's got another guy building to his magic three freqs, interesting stuff!

[poynt99]

Bench visibility to guests is your choice. Let me know, it's as easy as a check box.

.99

[Pulser]

Hey Fraser,
               Are you looking to Market this?...I've been wanting to build one of these..but my technical know how is limited....Do you have or would you be willing to do a tutorial for us less technical on how to go about building?....thanks...and your build is very nice!

[Fraser]

Hey Fraser,
               Are you looking to Market this?...I've been wanting to build one of these..but my technical know how is limited....Do you have or would you be willing to do a tutorial for us less technical on how to go about building?....thanks...and your build is very nice!

Hi Pulser.

Thanks for the compliment. Sorry I won´t be marketing it no.

But I have released the source code so far. Within that code is very detailed comments on pinouts wirings and the setup as a whole.

Steps to replicate are as follows:

(1)
Purchase a freeduino board and nokia screen from nuelectronics:

http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=14

http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=12

(2)
Purchase 1, 2 or 3 DDS modules either preassembled or as kits from these guys:
http://www.amqrp.org/kits/dds60/

(3)
Obtain a Windows or MAC PC with USB port and download the free development environment for Arduino/Freeduino onto it:
http://www.arduino.cc/en/Main/Software

(4)
Download my source code from earliear in this thread (PDE file and gfx library file)

(5)
Load the project into the environment and upload it via USB into the microboard.

(6)
Wire up your DDS modules as specified in the comments of the source code and that´s about it.

To get started with Arduino tools and boards I recommend the arduino.cc site.

All you have to do really is figure out how to upload the code. I´m REAL busy at the moment with other moneymaking work, so I can only give a tiny amount of time to this hobby. If you get real stuck though drop into this thread with problem and ask (Also PM me a heads up because I don´t check this thread regularly).

One thing that may trip you up is where to put the graphics library part of the code... Well the .c and .h files (and the folder they are within) need to be copied into the "library" folder of your arduino directory tree. Any Arduino forum will set you straight on this real quick if you have probs.

I plan to develop this further, with nice amp drive stages and software enhancements but its pretty much on hold at the moment.