RF Cafe Software
About RF Cafe
1996 - 2022
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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See the Example Below
Let me demonstrate with the attached workbook, dedicated to TI/Chipcon's CC1100 output matching network, how capable the tool is ( or Excel ). Three worksheets are networked together to form the proposed matching network for the CC1100 at the frequency of 915MHz.
This is the proposed network ( Balun ) out of the CC1100 datasheet:
To analyse this network with the tool, three sheets are necessary. The first sheet represents half a Balun Bridge for the N-Output, named "Matching RF-Nout" The second sheet represents half a Balun Bridge for the P-Output, named "Matching RF-Pout" The third sheet "Antenna matching" combines the the Rp, Cp of the overall "Matching RF-Nout" circuit and Rp, LP of the overall "Matching RF-Pout" circuit plus the few components on the way to the antenna.
Some important notes need to be made:
1. The output impedance of the CC1100 ports is given in the datasheet by looking towards the antenna. In the sheets we are looking to the CC1100 outputs hence the conjugate complex of the given impedance must be used.
2. The capacitor of C121 of 1pF needs to be doubled in value if you connect them to ground on both Balun branches instead between of the branches.
3. The Rp, Cp and the Rp, Lp values in the third sheet "Antenna matching" are links backward to the respective sheets of "Matching RF-Nout" and "Matching RF-Pout". Don't overwrite it.
4. The frequency value of the sheets "Matching RF-Nout" and "Matching RF-Pout" is linked forward to the "Antenna matching" frequency input field.
All the links make it possible to change the components values and the overall impact can be observed in the "Antenna matching" sheet. Also the frequency variation of the whole circuit can be shown if you click on the "fo-Variation Yes/No" button on the "Antenna matching" sheet. ( It will take about 10+ seconds to calculate and display the curve ) But don't do that on the other both sheets, it will destroy the links of the frequency input and you need to establish them again ( that is no problem but you need to be aware of it ).