NFC-A and NFC-B Sideband Measurements
应用文章
Load modulation of NFC-A and NFC-B target/listener devices is based on a 13.56 MHz carrier frequency (fC) with a subcarrier at 848 kHz (fSC). This creates an upper sideband frequency (fUSB) at 14.41 MHz and a lower sideband frequency (fLSB) at 12.71 MHz. Although characterizing load modulation is more often performed in the time domain using an oscilloscope or a one-box NFC tester, engineers that develop the RF technology blocks of NFC devices often prefer to perform load modulation measurements in the frequency domain. This is the natural measurement domain of spectrum analyzers, as well as that of most RF engineers. But there are several advantages in using a Keysight InfiniiVision X-Series oscilloscope to not only view and measure NFC signals in the time domain, but to also perform NFC-A and -B sideband measurements in frequency domain — simultaneously. This allows for cross-correlation between time-domain and frequency-domain measurements. One of the advantages of using an oscilloscope for frequency-domain measurements is the scope’s ability to synchronize acquisitions on sequences of complex RF communication with optional NFC triggering. Another advantage is “gated” FFT measurements. Gated FFT measurements allow you to isolate frequency-domain measurements onto specific bursts of subcarrier-generated load modulation for more accurate sideband measurements.