7. RF Performance
7.1 Conducted Power Measurements
During measurements, the BRD4257A Radio Board was attached to a Wireless Starter Kit Mainboard which was supplied by USB. The
voltage supply for the Radio Board was 3.3 V.
7.1.1 Conducted Measurements in the 915 MHz Band
The BRD4257A Radio Board was connected directly to a Spectrum Analyzer through its SMA connector. The supply for the RF section
(RFVDD) was 1.8 V provided by the on-chip DCDC converter, the supply for the sub-GHz power amplifier (SUBGRF_ON,
SUBGRF_OP) was 3.3 V provided by the mainboard (VBIAS through the discrete balun); for details, see the schematic of the
BRD4257A. The transceiver was operated in continuous carrier transmission mode. The output power of the radio was set to 19 dBm.
The typical output spectrum is shown in the following figure.
Figure 7.1. Typical Output Spectrum of the BRD4257A
As shown in the figure, the fundamental is close to 19 dBm so it is compliant with the 30 dBm fundamental limit. The strongest unwan-
ted emission is the double-frequency harmonic, but with only around -38.9 dBm level it is compliant with the corresponding limit
(-20 dBc) with large margin. The other unwanted emissions are under -50 dBm, so the conducted spectrum is compliant with the regu-
lation limits.
BRD4257A Reference Manual
RF Performance
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