DC blocking design from 900MHz to 2.4GHz?
DC blocking design from 900MHz to 2.4GHz?
(OP)
Hello-
I'm looking for a simple method/circuit that provides DC blocking up to 2.4GHz with low insertion loss, 50ohm network. For this particular application, it needs to be redundant (ex. two capacitors in series) and rated to 125VDC. Spacing is also a requirement between terminals, which forces me to use a 1206 or larger package.
The two operating frequencies that I am concerned with are 902-928MHz and 2.4-2.483GHz.
How do I choose the capacitor values? Can it be done as simply as series caps?
Thanks in advance!
I'm looking for a simple method/circuit that provides DC blocking up to 2.4GHz with low insertion loss, 50ohm network. For this particular application, it needs to be redundant (ex. two capacitors in series) and rated to 125VDC. Spacing is also a requirement between terminals, which forces me to use a 1206 or larger package.
The two operating frequencies that I am concerned with are 902-928MHz and 2.4-2.483GHz.
How do I choose the capacitor values? Can it be done as simply as series caps?
Thanks in advance!





RE: DC blocking design from 900MHz to 2.4GHz?
Here's a link to an example (Data sheet) and it includes a schematic:
http://www.minicircuits.com/pdfs/BLK-6+.pdf
Too bad it doesn't mention the capacitor value. But just choose a value that has very low series reactance, while minding the top end stray inductance.
Redundancy might be also provided by a parallel inductor in case the cap fails, it would short out the voltage.
RE: DC blocking design from 900MHz to 2.4GHz?
Understood that it is typically a series capacitor(s).
I've heard many people mention that they typically use 100pF as a value. I would need to make sure that the SRF is beyond my maximum operating frequency, correct?
RE: DC blocking design from 900MHz to 2.4GHz?
Yes, you'd want to check and double-check for any stray resonances *as installed*. One option would be to sweep it with an analyzer.
RE: DC blocking design from 900MHz to 2.4GHz?
RE: DC blocking design from 900MHz to 2.4GHz?
If you're putting two in series, then you should lean towards a higher value to compensate.
Or use another topology, perhaps with a parallel inductor as backup.
RE: DC blocking design from 900MHz to 2.4GHz?
RE: DC blocking design from 900MHz to 2.4GHz?
With bypass capacitors (for example), one could estimate the installed lead length, and using charts and tables choose a capacitance value that would provide a series resonance at the desired frequency.
I actually used this trick once where I wanted to snub out a 40 MHz oscillation. So I determined the installed lead length and chose the capacitor value to give a series resonance at about 40 MHz. It was probably unnecessary (any old cap would have snubbed it), but I had a strong desire to nuke it.
Working with two frequency bands complicates this approach.
Good luck.
RE: DC blocking design from 900MHz to 2.4GHz?
RE: DC blocking design from 900MHz to 2.4GHz?
RE: DC blocking design from 900MHz to 2.4GHz?
RE: DC blocking design from 900MHz to 2.4GHz?
RE: DC blocking design from 900MHz to 2.4GHz?