EEVblog Electronics Community Forum
Electronics => RF, Microwave, Ham Radio => Topic started by: Yansi 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
-
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
-
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.
-
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.
(https://www.eevblog.com/forum/rf-microwave/adf4350-vco-range-question-2170mhz-possible/?action=dlattach;attach=390479;image)
-
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).
-
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.