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Help designing matching circuit - RF Cafe Forums
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| ARQuattr
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Post subject: Help designing matching circuit
Posted: Thu Oct 01, 2009 8:38 am
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Joined: Thu Oct 01, 2009
7:49 am
Posts: 3 |
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I'm relatively new to RF design and I have a 2.4GHz
transceiver I need to match to a balun but I haven't
been able to find good information on how to do
that. The 'optimal load impedance' specified by
the transceiver for the balanced output is something
like 15 + j88 Ohm, and the baluns only shows balanced
input impedances of 50 Ohm, or 100 Ohm, 150 Ohm,
etc.
Any advice would be greatly appreciated.
Regards,
Angelo
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Alberto |
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Post subject: Re: Help designing matching circuit
Posted: Sun Oct 04, 2009 6:16 pm
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Joined: Sun Oct 04, 2009
5:17 pm
Posts: 6 |
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Your question is not very clear to me. Do you want
to build a circuit (RLC) that connected to the unbalanced
input of a balun will be seen at its output as a
balanced impedance of 15 + j88 ohm ? Is your system
narrow or wide bandwidth ? Which balun are you using
? Best regards
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ARQuattr |
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Post subject: Re: Help designing matching circuit
Posted: Sun Oct 04, 2009 11:18 pm
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Joined: Thu Oct 01, 2009
7:49 am
Posts: 3 |
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Alberto |
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Post subject: Re: Help designing matching circuit
Posted: Mon Oct 05, 2009 4:54 pm
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Joined: Sun Oct 04, 2009
5:17 pm
Posts: 6 |
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Ok, I think the fastest way is to connect an external
balun to the CC2591, as suggested in its data sheet,
page 6. Then connect the SMA output (it is a 50
ohm unbalanced) to the matching network you can
find in the nRF24LE1 datasheet, page 186, or at
the link "http://www.nordicsemi.com/files/Product/white_paper/Tuning_the_nFR24xx_matching_network.pdf".
Another way (quite complex) can be the design
of a differential matching network connecting directly
the two ICs. Starting from the CC2591 you have to
apply a differential matching from 50 to 15 ohm
then you can add two inductor (one to each branch)
having 44 ohm reactance each, @ 2.4 GHz. Since VDD_PA
must supply both ANT1 and ANT2 you need also two
high value inductors (let me say 39 nH) to connect
those pins. To calculate the matching network you
can use RFsim99 freeware SW: I suggest the lowpass
implementation to reduce the harmonics content.
To convert the matching circuit to differential
you just have to duplicate the series inductor on
each branch dividing by 2 the original value and
leaving the capacitor to its original value. However
if you are no so familiar with matching netwok I
think this could be a not so easy task.
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Guido7 |
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Post subject: Re: Help designing matching circuit
Posted: Tue Oct 06, 2009 5:38 pm
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Joined: Tue Oct 06, 2009
5:26 pm
Posts: 1 |
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Greetings,
I just went through the entire design
process to do just this. There are several ways
to skin this cat but the simplest and best approach
is to break down the functions to two parts. First
use a 180 Degree hybrid to split the power with
proper phase shift. Then use a lowpass matching
network to step up from 50 Ohms to whatever the
target. The LP is the lowest loss solution to matching
and gives the benefit of additional frequency rejection.
Make it an even number of sections for the assymetric
impedance response. Starting with a series L for
the 50 Ohm side you could possible match with 4
or 6 elements. This means that the coils will increase
in value and the caps will decrease.
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raghavkapur |
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Post subject: Re: Help designing matching circuit
Posted: Wed Apr 04, 2012 7:29 am
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Joined: Mon Aug 09, 2010
5:44 am
Posts: 9 |
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Posted 11/12/2012
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