Author Topic: RF Synthesizer IC  (Read 954 times)

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Offline perdrixTopic starter

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RF Synthesizer IC
« on: August 01, 2020, 02:08:28 am »
Hi folks

I'm looking for a synthesizer chip that will go from very near DC (0.1Hz or so) up to (say) 1 or 2GHz.

Is there anything that will do this?  I couldn't find one that fitted the bill on Analog Devices site.

Thanks
David

 

Offline KaneTW

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Re: RF Synthesizer IC
« Reply #1 on: August 01, 2020, 02:15:56 am »
You pretty much need DDS or two separate synths (DDS + PLL) for that.

https://www.analog.com/en/products/ad9914.html does DDS up to 1750MHz.
 

Offline perdrixTopic starter

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Re: RF Synthesizer IC
« Reply #2 on: August 01, 2020, 12:59:28 pm »
Oh dear LFCSP-88 with a pad underneath.   Not something I fancy soldering at home ... 

Sadly the eval board is a bit more than I would like.

David
 

Offline KaneTW

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Re: RF Synthesizer IC
« Reply #3 on: August 01, 2020, 04:26:03 pm »
I would just split it into two signal paths. That's how basically everyone does it.

LFCSP-88 is fairly solderable IMO, but i understand the trepidation with a $160 IC.
 

Offline radar_macgyver

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Re: RF Synthesizer IC
« Reply #4 on: August 01, 2020, 05:41:48 pm »
You'd likely need multiple signal paths anyway since a single amplifier operating from 0.1 Hz to 1 GHz is in itself quite hard.
 

Offline KaneTW

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Re: RF Synthesizer IC
« Reply #5 on: August 01, 2020, 07:39:57 pm »
Minicircuits RAM-6A+ is a pretty decent DC to 2GHz amplifier.
 

Offline radar_macgyver

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Re: RF Synthesizer IC
« Reply #6 on: August 01, 2020, 08:54:37 pm »
Nice find! What biasing inductor and coupling cap would you choose to work from 0.1 Hz to 1 GHz?
 

Offline KaneTW

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Re: RF Synthesizer IC
« Reply #7 on: August 01, 2020, 09:20:39 pm »
Ah, yeah, good call. That gets difficult.
 

Offline KE5FX

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Re: RF Synthesizer IC
« Reply #8 on: August 01, 2020, 09:30:35 pm »
For true-DC applications, look at the LMH3401 that nctnico used in his 1 GHz+ differential probe.  You'll need a split supply (and he also uses a good part for that purpose, the LM27762). 

For that matter, there's no religious reason why you couldn't use a 50-ohm MMIC with a split supply.  It's not commonly done for a couple of reasons, one being that it complicates grounding and the other being the traditionally-high flicker noise near DC from GaAs and similar materials.  Newer parts will still have the first limitation but may do better at the second.
 


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