inductor to be used at 2.4 ghz

[aashishsharma]

Hey I am designing some circuit which needs inductors.
My problem is my circuit is functioning at 2.4 ghz and i have not worked at such high freq.I found on internet that SRF might pose problem although i understood the concept but still in the dark regarding what inductors to use.
some inductors to be used in elliptical low pass filter and other in LNA
thnks in advance

 

[HMS1021]

There are many good inductors that have a SRF of greater than 10GHz. You will find them limited to <10nH but this is ok for most designs at 2.4GHz. The best performance are the wire wound on a air or ceramic core.

If you use the sort filter on the digikey page at https://www.digikey.com/scripts/dks...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

you will see what is available.

 

[aashishsharma]

hey i found 3.3nH here but i also need 1.2uh and 0.68uH too.
any ideas?

 

[keith1200rs]

Are you sure that is a 2.4GHz filter? I think you need to show your design.

Keith

 

[aashishsharma]

hey keith 1st 3.3nH inductor for LNA datasheet:https://datasheets.maximintegrated.com/en/ds/MAX2644EVKIT.pdf
and other 2 inductors are for filter to be used at IQ demodulator.Datasheet:https://www.analog.com/static/imported-files/data_sheets/AD8347.pdf

- - - Updated - - -

also i have modified the filter given in the datasheet to have 3db freq of 11khz but have left the inductors untouched(tuned just the capacitors in ADS) as i knew they will be difficult to handle

 

[keith1200rs]

OK, I don't think you will be expecting the IQ demodulator inductors to be working at 2.4GHz. Use the Digikey search tool with appropriate filters to narrow your search:

https://www.digikey.com/product-search/en/inductors-coils-chokes/fixed-inductors/196627

Keith.

 

[aashishsharma]

OK, I don't think you will be expecting the IQ demodulator inductors to be working at 2.4GHz. Use the Digikey search tool with appropriate filters to narrow your search:



Keith.

Do you mean its not possible to find the inductors to be working at that range???

 

[keith1200rs]

I don't think you will find an inductor around 1uH with an SRF above 2.4GHz. These: are probably the highest ones I know of and they are not meant for filters - they are power inductors.

2.4GHz operation is not required for the IQ demodulator filter - the demodulator bandwidth is only 90MHz.

Keith

 

[aashishsharma]

2.4GHz operation is not required for the IQ demodulator filter - the demodulator bandwidth is only 90MHz.


Keith

yeah I saw the bandwidth in the datasheet. Basically I have a 2.4 ghz LO frequency signal and other RF input signal that i will be feeding will be 2.4 + some frequency. So the mixer will be giving me a sum and a difference frequency. I am only interested in difference frequency that would be < 10 Khz { which means 2.4 +10 khz would be coming to RFIN}.
so i need to filtler out sum frequency.
I saw many other demods too but i am sure this is right one as it allows LO freq to be upto 2.7ghz
I COULD NOT UNDERSTAND EXACTLY THE MEANING OF DEMOD BANDWIDTH???
AASHISH

 

[keith1200rs]

My understanding is that the demodulator will filter the higher frequency components (2.4GHz and higher) so you don't have to worry about them. Maybe someone else can give a better explanation.

Keith