The BRD41XX type boards applies the UFL RF connector and a UFL-SMA transition. These two elements cause approximately 0.5 dB
additional attenuation. Therefore, the real delivered power is approximately 0.5 dB higher.
The main conclusions are as follows:
1. The Tline match has nearly the same fundamental power, harmonic levels, and current consumption as the ladder four-element
lumped element match (see
3.5 Bench Tuning and Measured Results
), but with a lower cost.
2. The Tline match complies with the U.S. FCC (-41.2 dBm EIRP) and EU ETSI (-30 dBm EIRP) harmonic limits with large (>10 dB)
margin at ~ 20 dBm power levels and below.
3. Different EFR32 package versions can be operated with the same Tline match without a significant effect on the output spectrum.
The difference is usually less than 0.5 dB, which is less than the chip-to-chip variation.
The 2.4 GHz Tline matches are measured on eight boards with each EFR32 package versions to have more reliable test data.
Figure
4.9 Measured Results of the Bench Tuned 2.4 GHz Tline Matches in TX Mode with Different EFR32 Packages on page 34
shows the
test results on maximum power state. After compensating the UFL coSMA transition loss, the real delivered power is approxi-
mately 0.5dB higher.
Figure 4.9. Measured Results of the Bench Tuned 2.4 GHz Tline Matches in TX Mode with Different EFR32 Packages
The fundamental power second and third harmonic variations across the 2.4–2.48 GHz band are also shown in Appendix 1. According
to
Appendix 1. PA Optimum Impedance Determination
, the fundamental variation is less than 0.5 dB, and the harmonics are far below
the regulation (ETSI and FCC) limits.
The minimal BOM two-element match (with L0-C0 parallel resonator pair) for low-power regimes (<+13 dBm) are also measured on
eight boards for each package versions (7x7 mm 48-pin dual band BRD4152A, 7x7 mm 48-pin 2.4 GHz BRD4102A, 5x5 mm 32-pin 2.4
GHz BRD4112A). Here, the PA is fed from 1.8 V generated by the internal dc-dc converter.
Figure 4.10 Measured Results of the 2.4
GHZ Minimal BOM Low-Power Matches in TX Mode with Different EFR32 Packages on page 34
the ~13 sdBm results at middle band
(2.45 GHz).
Figure 4.10. Measured Results of the 2.4 GHZ Minimal BOM Low-Power Matches in TX Mode with Different EFR32 Packages
As can be seen, the two-element minimal BOM matches comply both with the ETSI and FCC regulations up to 13 dBm power level.
Note that conducted spectrum plots are measured with the wideband 50 Ω termination of the Spectrum Analyzer. Different termination
impedance at the harmonics generated by a real connecting Tline combination may result in much higher harmonic levels on
the antenna.
AN930: EFR32 2.4 GHz Matching Guide
Transmission Line (Tline) Match for Minimal BOM Solutions (U.S. Patent US9780757B1)
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