RF power amplifier for Nuclear Quadrupole Resonance (NQR) spectrometer

Hello,

I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using the SpinCore Radio processor USB board. Here is the manual of the board.
http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf

I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 - 10 MHz). 

I have just found the following RF power amplifiers:

1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB

http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8HAQ

2- KAA4020 500 Watts CW, 1 - 50 MHz

http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf

I just want to know, Is it possible to use the continuous wave (CW) amplifiers to amplify the pulsed singals generated by the RadioProcessor board? 

Or I have to use the pulsed amplifiers only? 

A waiting your reply as soon as possible

Thanks

On Tuesday, December 27, 2016 at 12:23:16 AM UTC+11, BioPhysics2016 wrote:
> Hello,
> 
> I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using the SpinCore Radio processor USB board. Here is the manual of the board.
> http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf
> 
> I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 - 10 MHz). 
> 
> I have just found the following RF power amplifiers:
> 
> 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> 
> http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8HAQ
> 
> 2- KAA4020 500 Watts CW, 1 - 50 MHz
> 
> http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> 
> I just want to know, Is it possible to use the continuous wave (CW) amplifiers to amplify the pulsed signals generated by the RadioProcessor board? 
> 
> Or I have to use the pulsed amplifiers only? 
> 
> Awaiting your reply as soon as possible

Continuous wave amplifiers can run continuously at their rated power. If the pulses of RF power that you want don't have a peak power that exceeds the continuous rating, you won't have any problem at all, but the continuous wave amplifier may be more expensive than you actually need.

High RF power implies large voltage swings, so you won't be able to get more power out of the continuous wave amplifiers than their continuous rating.

Designing an amplifier from scratch that can deliver brief bursts of high voltage and current is an expensive and time-consuming exercise.

There are people around here who might be able to help, but you would probably get more help if you specified how long you pulses need to be, and what sort of duty cycle you need.

Most RF amplifiers are designed around a 50R load to feed an antenna transmitting into free space - for ham radio and the like.

If the excitation coils for your NQR have a higher impedance - as seems likely, since you will want a solenoid into which you can put your sample containing some nitrogen-14 nuclei - this also affects what you might need and could get  away with.

http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1065&context=elecengtheses

Talks about a class-D RF amplifier ...

-- 
Bill Sloman, Sydney

Den mandag den 26. december 2016 kl. 15.58.37 UTC+1 skrev bill....@ieee.org:
> On Tuesday, December 27, 2016 at 12:23:16 AM UTC+11, BioPhysics2016 wrote:
> > Hello,
> > 
> > I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using the SpinCore Radio processor USB board. Here is the manual of the board.
> > http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf
> > 
> > I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 - 10 MHz). 
> > 
> > I have just found the following RF power amplifiers:
> > 
> > 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> > 
> > http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8HAQ
> > 
> > 2- KAA4020 500 Watts CW, 1 - 50 MHz
> > 
> > http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> > 
> > I just want to know, Is it possible to use the continuous wave (CW) amplifiers to amplify the pulsed signals generated by the RadioProcessor board? 
> > 
> > Or I have to use the pulsed amplifiers only? 
> > 
> > Awaiting your reply as soon as possible
> 
> Continuous wave amplifiers can run continuously at their rated power. If the pulses of RF power that you want don't have a peak power that exceeds the continuous rating, you won't have any problem at all, but the continuous wave amplifier may be more expensive than you actually need.
> 
> High RF power implies large voltage swings, so you won't be able to get more power out of the continuous wave amplifiers than their continuous rating.
> 
> Designing an amplifier from scratch that can deliver brief bursts of high voltage and current is an expensive and time-consuming exercise.
> 
> There are people around here who might be able to help, but you would probably get more help if you specified how long you pulses need to be, and what sort of duty cycle you need.
> 
> Most RF amplifiers are designed around a 50R load to feed an antenna transmitting into free space - for ham radio and the like.
> 
> If the excitation coils for your NQR have a higher impedance - as seems likely, since you will want a solenoid into which you can put your sample containing some nitrogen-14 nuclei - this also affects what you might need and could get  away with.
> 

the solenoid is generally matched to 50R and used for both tx and rx

you need a pulsed amplifier because it need to ramp up and down and be 
quiet in microseconds after tx

BioPhysics2016 <mabdelaleem2012@gmail.com> wrote:

> Hello,
> 
> I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using
> the SpinCore Radio processor USB board. Here is the manual of the
> board. 
> http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf 
> 
> I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 -
> 10 MHz). 
> 
> I have just found the following RF power amplifiers:
> 
> 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> 
> http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7
> t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8
> HAQ 
> 
> 2- KAA4020 500 Watts CW, 1 - 50 MHz
> 
> http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> 
> I just want to know, Is it possible to use the continuous wave (CW)
> amplifiers to amplify the pulsed singals generated by the
> RadioProcessor board? 
> 
> Or I have to use the pulsed amplifiers only? 
> 
> A waiting your reply as soon as possible
> 
> Thanks

Why not get an RF amplifier made by SpinCore. They have two models:

http://www.spincore.com/CD/RFPA/RFPA_Manual.pdf

Any reason for wanting do do NMR? Apparently it is not very sensitive and 
requires a strong magnet:

https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance

You might be able to do the required analysis with spectrophometry. There 
are dozens of examples on the web. Here is one you can make for under 
$100:

https://hackaday.io/project/10738-ottervis-lgl-spectrophotometer

Here is another using an Arduino:

http://myspectral.com/

Here is one for $10, plus support from an active forum:

https://publiclab.org/wiki/spectrometry

Note: spectrophometry is not very sensitive either, but Fluorescence 
Spectrophotometry may increase the sensitivity 1,000 times:

http://www.biocompare.com/Bench-Tips/173963-Choosing-the-Best-Detection-
Method-Absorbance-vs-Fluorescence/

On 12/26/2016 11:58 AM, Steve Wilson wrote:
> BioPhysics2016 <mabdelaleem2012@gmail.com> wrote:
>
>> Hello,
>>
>> I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using
>> the SpinCore Radio processor USB board. Here is the manual of the
>> board.
>> http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf
>>
>> I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 -
>> 10 MHz).
>>
>> I have just found the following RF power amplifiers:
>>
>> 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
>>
>> http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7
>> t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8
>> HAQ
>>
>> 2- KAA4020 500 Watts CW, 1 - 50 MHz
>>
>> http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
>>
>> I just want to know, Is it possible to use the continuous wave (CW)
>> amplifiers to amplify the pulsed singals generated by the
>> RadioProcessor board?
>>
>> Or I have to use the pulsed amplifiers only?
>>
>> A waiting your reply as soon as possible
>>
>> Thanks
>
> Why not get an RF amplifier made by SpinCore. They have two models:
>
> http://www.spincore.com/CD/RFPA/RFPA_Manual.pdf
>
> Any reason for wanting do do NMR? Apparently it is not very sensitive and
> requires a strong magnet:
>
> https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance

NQR is not NMR.  No magnet required.

https://en.wikipedia.org/wiki/Nuclear_quadrupole_resonance

-- 
Grizzly H.

On Tuesday, December 27, 2016 at 3:58:56 AM UTC+11, Steve Wilson wrote:
> BioPhysics2016 <mabdelaleem2012@gmail.com> wrote:
> 
> > Hello,
> > 
> > I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using
> > the SpinCore Radio processor USB board. Here is the manual of the
> > board. 
> > http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf 
> > 
> > I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 -
> > 10 MHz). 
> > 
> > I have just found the following RF power amplifiers:
> > 
> > 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> > 
> > http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7
> > t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8
> > HAQ 
> > 
> > 2- KAA4020 500 Watts CW, 1 - 50 MHz
> > 
> > http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> > 
> > I just want to know, Is it possible to use the continuous wave (CW)
> > amplifiers to amplify the pulsed singals generated by the
> > RadioProcessor board? 
> > 
> > Or I have to use the pulsed amplifiers only? 
> > 
> > A waiting your reply as soon as possible
> > 
> > Thanks
> 
> Why not get an RF amplifier made by SpinCore. They have two models:
> 
> http://www.spincore.com/CD/RFPA/RFPA_Manual.pdf
> 
> Any reason for wanting do do NMR? Apparently it is not very sensitive and 
> requires a strong magnet:
> 
> https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance

This isn't regular nuclear magnetic resonance spectroscopy but nuclear quadropole resonance spectroscopy, which doesn't require a magnetic field. It only works for nuclei which have a quadropole moment, and nitrogen-14 does happen to be one of them. You find nitrogen atoms in most explosives, so the technique is commercially interesting.

https://en.wikipedia.org/wiki/Nuclear_quadrupole_resonance
 
<snip>

-- 
Bill Sloman, Sydney

On Monday, December 26, 2016 at 9:41:34 AM UTC-8, mixed nuts wrote:
> On 12/26/2016 11:58 AM, Steve Wilson wrote:
> > BioPhysics2016 <mabdelaleem2012@gmail.com> wrote:
> >
> >> Hello,
> >>
> >> I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using
> >> the SpinCore Radio processor USB board. Here is the manual of the
> >> board.
> >> http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf
> >>
> >> I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 -
> >> 10 MHz).
> >>
> >> I have just found the following RF power amplifiers:
> >>
> >> 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> >>
> >> http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7
> >> t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8
> >> HAQ
> >>
> >> 2- KAA4020 500 Watts CW, 1 - 50 MHz
> >>
> >> http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> >>
> >> I just want to know, Is it possible to use the continuous wave (CW)
> >> amplifiers to amplify the pulsed singals generated by the
> >> RadioProcessor board?
> >>
> >> Or I have to use the pulsed amplifiers only?
> >>
> >> A waiting your reply as soon as possible
> >>
> >> Thanks
> >
> > Why not get an RF amplifier made by SpinCore. They have two models:
> >
> > http://www.spincore.com/CD/RFPA/RFPA_Manual.pdf
> >
> > Any reason for wanting do do NMR? Apparently it is not very sensitive and
> > requires a strong magnet:
> >
> > https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
> 
> NQR is not NMR.  No magnet required.
> 
> https://en.wikipedia.org/wiki/Nuclear_quadrupole_resonance

  There's also low-field and zero-field NMR for half-integer-spin isotopes:

https://en.wikipedia.org/wiki/Low_field_nuclear_magnetic_resonance

https://en.wikipedia.org/wiki/Zero_field_NMR

  For integer-spin isotopes like N14 NQR is the ticket.


  Mark L. Fergerson

On Tuesday, December 27, 2016 at 12:23:16 AM UTC+11, BioPhysics2016 wrote:
> Hello,
> 
> I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using the SpinCore Radio processor USB board. Here is the manual of the board.
> http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf
> 
> I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 - 10 MHz). 
> 
> I have just found the following RF power amplifiers:
> 
> 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> 
> http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8HAQ
> 
> 2- KAA4020 500 Watts CW, 1 - 50 MHz
> 
> http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> 
> I just want to know, Is it possible to use the continuous wave (CW) amplifiers to amplify the pulsed singals generated by the RadioProcessor board? 
> 
> Or I have to use the pulsed amplifiers only? 
> 
> A waiting your reply as soon as possible

There are quite a few people interested in this question

http://link.springer.com/chapter/10.1007%2F978-90-481-3062-7_3

talks about using permanent magnets and long excitation sequences to get better signal to noise ratio's.

I'm wondering whether a simple class-D exitation might work.

The simplicity would strictly be in the analog/power part of the circuit - a PMOS power FET tied to a - say - +150V positive rail, and an N-Channel power FET tied to a -say - -150V power rail.

You'd use a cascode driver - more power FETs, possibly in cascode - to turn on the first FET from 30 degrees into the excitation sine wave to 150 degrees and the second FET from 210 degrees to 330 degrees.

Not very complicated.

The complicated - but not all that expensive - bit would be fast digital logic for setting the turn-on and turn-off times for both transistors.

The highest sodium nitrite line at 4.6MHz a period of 217.391 nsec. It has a lie width of 207Hz. The period of a 4.600207Hz cycle is 217.382 nsec so you are going to be wanting to set your pulse timings to better than 10psec.

ON Semiconductor do a chip that is almost equal to the task

http://www.onsemi.com/pub_link/Collateral/MC10EP195-D.PDF

It does offer 10psec timing resolution, over 10nsec - actually from 2nsec to about 12nsec - so if you did your coarse timing from a 100MHz clock and used the MC100EP195 to generate your fine delays you'd be more or less okay.

In fact you'd want edges 72nsec apart to define a class-D approximation to 4.6MHz sinewave, so you'd probably go for a 200MHz clock and use the MC100EP195 to generate 5nsec fine delays.

The actual delay generated by the MC100EP195 is somewhat temperature dependent, so you might want an even faster clock.

The timing module could be done in ECL on a four-layer board with buried ground and -2V planes. More layers would make it easier.

My feeling is that there are some fast programmable logic chips around that could do much the same job in a single - rather expensive device.

comp.arch.fpga might be the place to ask about that.

-- 
Bill Sloman, Sydney

On Monday, December 26, 2016 at 5:23:16 AM UTC-8, BioPhysics2016 wrote:
 
> I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 - 10 MHz). 

Here in UW chem, our older NMR power amps are either ENI wideband amp (like ENI 350 or 3100,) or amateur radio "linear" broadband amps from Henry Radio.

On ebay I see several used ENI amps for $1,500 and up.   In the past I've seen these for under $200, but non-working with dead output transistors (so, buy and repair!)

> I just want to know, Is it possible to use the continuous wave (CW) amplifiers to amplify the pulsed singals generated by the RadioProcessor board?

Yes.

It appears that the main difference with "pulse" amplifiers is the added probe-protecting features, which shut down the output whenever detecting long pulses, CW, or PWM above ~20%.

An amateur radio CW amplifier under $1000 should work fine.  (Some of those ham amp kits are under $100!)  But it lacks the automatic protection.  Just make sure to avoid accidental oscillation caused by old corroded BNC cables with bad shielding.  That, or undergrad students who burn up your match networks with wrong software settings.

Also check out:

https://www.jiscmail.ac.uk/cgi-bin/webadmin?A0=CCPNMR

http://qa.nmrwiki.org/

http://www.bionmr.com/forum/nmr-questions-answers-24/

On Thursday, December 29, 2016 at 6:33:17 PM UTC+11, bill....@ieee.org wrote:
> On Tuesday, December 27, 2016 at 12:23:16 AM UTC+11, BioPhysics2016 wrote:
> > Hello,
> > 
> > I'm building Nuclear Quadrupole Resonance (NQR)to test for 14N. using the SpinCore Radio processor USB board. Here is the manual of the board.
> > http://www.spincore.com/CD/RadioProcessor/RadioProcessor_manual.pdf
> > 
> > I could not find low-cost 50/100/200 Watts RF power amplifiers(0.25 - 10 MHz). 
> > 
> > I have just found the following RF power amplifiers:
> > 
> > 1- ENI 325LA RF Power Amplifier, 250 kHz to 150 MHz, 25 W, 50 dB
> > 
> > http://www.bellnw.com/manufacturer/ENI/325LA.htm?gclid=Cj0KEQiAnIPDBRC7t5zJs4uQu5UBEiQA7u5NexeWcgCpwmo8gfkBHI8TfT7SR8hTVzjdJTujqguMjC8aAkaK8P8HAQ
> > 
> > 2- KAA4020 500 Watts CW, 1 - 50 MHz
> > 
> > http://www.arww-modularrf.com/post/KAA4020%20(7-98-836-003A).pdf
> > 
> > I just want to know, Is it possible to use the continuous wave (CW) amplifiers to amplify the pulsed singals generated by the RadioProcessor board? 
> > 
> > Or I have to use the pulsed amplifiers only? 
> > 
> > A waiting your reply as soon as possible
> 
> There are quite a few people interested in this question
> 
> http://link.springer.com/chapter/10.1007%2F978-90-481-3062-7_3
> 
> talks about using permanent magnets and long excitation sequences to get better signal to noise ratio's.
> 
> I'm wondering whether a simple class-D exitation might work.
> 
> The simplicity would strictly be in the analog/power part of the circuit - a PMOS power FET tied to a - say - +150V positive rail, and an N-Channel power FET tied to a -say - -150V power rail.
> 
> You'd use a cascode driver - more power FETs, possibly in cascode - to turn on the first FET from 30 degrees into the excitation sine wave to 150 degrees and the second FET from 210 degrees to 330 degrees.
> 
> Not very complicated.
> 
> The complicated - but not all that expensive - bit would be fast digital logic for setting the turn-on and turn-off times for both transistors.
> 
> The highest sodium nitrite line at 4.6MHz a period of 217.391 nsec. It has a lie width of 207Hz. The period of a 4.600207Hz cycle is 217.382 nsec so you are going to be wanting to set your pulse timings to better than 10psec.
> 
> ON Semiconductor do a chip that is almost equal to the task
> 
> http://www.onsemi.com/pub_link/Collateral/MC10EP195-D.PDF
> 
> It does offer 10psec timing resolution, over 10nsec - actually from 2nsec to about 12nsec - so if you did your coarse timing from a 100MHz clock and used the MC100EP195 to generate your fine delays you'd be more or less okay.
> 
> In fact you'd want edges 72nsec apart to define a class-D approximation to 4.6MHz sinewave, so you'd probably go for a 200MHz clock and use the MC100EP195 to generate 5nsec fine delays.
> 
> The actual delay generated by the MC100EP195 is somewhat temperature dependent, so you might want an even faster clock.
> 
> The timing module could be done in ECL on a four-layer board with buried ground and -2V planes. More layers would make it easier.
> 
> My feeling is that there are some fast programmable logic chips around that could do much the same job in a single - rather expensive device.
> 
> comp.arch.fpga might be the place to ask about that.

There's nothing like sleeping on a problem.

It might make more sense to use something like an Analog Devices AD9913

http://www.analog.com/media/en/technical-documentation/data-sheets/AD9913.pdf

to generate a sine wave at up to about 60MHz - that's twelve times as fast as the highest NQR frequency needed - 4.952MHz for RDX - and use a programmable logic device (PLD) to generate the various waveforms needed to drive the excitation source and the demodulators.

60MHz isn't all that fast. You'd need a fast comparator to turn the - low-pass filtered up-to-60 MHz sine wave into a square wave to drive the clock input to PLD, and you'd need a bunch of outputs from the PLD to generate the excitation pulses and - a little later - the in-phase and quadrature demodulation pulses.

207Hz line width on the 4.6MHz sodium nitrate line is 45 ppm, so you'd probably want to use a good quality and probably temperature controlled 25MHz crystal oscillator to drive the AD9913 reference input (multiplied up to 250MHz inside the device to keep the up-to-60 MHz output clean and easily low-pass filterable). The AD 9913 does seem to give you all the frequency resolution you could need.

-- 
Bill Sloman, Sydney