Author Topic: ADF4350 - VCO range question, 2170MHz possible?  (Read 1333 times)

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Offline YansiTopic starter

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ADF4350 - VCO range question, 2170MHz possible?
« on: January 28, 2018, 08:14:39 pm »
Hi

playing with some interesting ideas to use the ADF4350 for, I run into an issue regarding the VCO range.  I need to generate two frequencies: 2170MHz and 1085MHz, which is exactly a half of the first one.  ADF4350 (4351) did look exact fit for the job, until I realized the bottom end of the VCO range is 2200MHz.

I need 2170, which is a 1.36% lower, than the specified minimum. Do you think it is possible or wise to use the ADF4350 slightly out of the range? I currently do not have any of these so I can't test it myself.

Do you know any other suitable single chip solution, that could output simultaneously these two frequencies? (2170MHz, 1085MHz) I did search a bit on the Analog Devices website, but could not find any suitable ones.

Thanks,
Y
 

Offline RadioNerd

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Re: ADF4350 - VCO range question, 2170MHz possible?
« Reply #1 on: January 28, 2018, 08:33:02 pm »
as far as I know the ADF4350/1 has an output divider... you can thetefore set the VCO to twice the desired frequency and divide it by 2. Or by 4 for 1084 MHz
 

Offline YansiTopic starter

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Re: ADF4350 - VCO range question, 2170MHz possible?
« Reply #2 on: January 28, 2018, 08:36:00 pm »
There is only one divider present on RFoutA, RFoutB is directly VCO output. There is no other divider available.

I need output of 2170 and 1085 MHz simultaneously from a single IC.

I do not want two ICs, if it can be done with only one.
 

Offline YansiTopic starter

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Re: ADF4350 - VCO range question, 2170MHz possible?
« Reply #3 on: January 28, 2018, 08:50:12 pm »
According to fig 20 from the datasheet, it may be possible to operate at 2170MHz (red line marker), but guessing at reduced temperature range.  After reading through the datasheet a bit, cold temperatures <0°C  may become an obstacle.

 

Offline RadioNerd

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Re: ADF4350 - VCO range question, 2170MHz possible?
« Reply #4 on: January 28, 2018, 08:51:25 pm »
sorry I didnt read your post carefully...
pushing the spec by 1-2% is probaby no problem as long as you stay around room temperature.
The actual VCO range is wider than the spec anyway to guarantee correct operation within the full temperature range (-40 to at least 85deg C).
 

Offline YansiTopic starter

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Re: ADF4350 - VCO range question, 2170MHz possible?
« Reply #5 on: January 28, 2018, 09:06:59 pm »
Okay, I will try it, once I'll have a bit of time spared for it. It is one (of many) ideas for some future RF projects.  If it'll work from at least 0°C and up, it will be good enough.  :)

It is a kind of idea how to make a convertor for a 3400MHz HAM band - I am still trying to attack that one. More or less successfully.

3400MHz input,  1230MHz IF1, 145MHz IF2/output.   (Hence LO1=2170, LO2=1085)

There are suitable SAW filters available for 1230MHz, input filter could be realized using microstrip. 
« Last Edit: January 28, 2018, 09:15:22 pm by Yansi »
 


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