3 Short-Range Comms & IoT Mode
3.3 LoRa (CSS) Demodulation Measurement
No. Window
7 "Metrics" on page 321
8 "Result Table" on page 322
9 "Marker Table" on page 390
10 "Demod Bits" on page 323
11 "Decode Bits" on page 324
12 "Decode Info" on page 324
3.3.2.1 RF Spectrum
This window shows a spectral display of the input RF signal with the ordinate being
amplitude and the abscissa being time. The ordinate is always scaled in dB, with a
unit of dBm.
The information of the center frequency, the span, and the Res BW is displayed at
the bottom of the window. The Ref Value and Scale/Div are annotatedon the grid.
Two vertical lines are centered around the center frequency in this window. The
spacing between the two lines is equal to the channel BW.
3.3.2.2 Demod Waveform
The demodulated signal is displayed in the time domain in this window. The abscissa
is time. And the ordinate is the frequency deviation of the chirp signal. The ordinate
is linearly scaled in Hz.
Before this trace is generated, a burst search is performed on the raw RF envelope
to locate the analyzed burst.
If a valid burst is found, the portion on the raw demod waveform corresponding to
the burst is taken out for further interpolation. The product of the interpolation is
named “demod waveform”. The time elapse of the demod waveform is set by the
demod waveform offset and the demod waveform time under Meas Setup -> Time or
under Sweep -> Sweep/Control. And the number of the points on the demod
waveform trace is set by the demod waveform time under Sweep -> Sweep/Control.
It could be possible that the actual length of the burst is shorter than the product of
the sum of the demod waveform offset and the demod waveform time. In such a
case, the portion after the burst on the trace will be filled with 0. And a piece of
information indicating that the demod waveform time setting is out of range will be
popped up.
If no valid burst is found, the demod waveform is obtained by truncating the raw
demod waveform based on the demod waveform offset and the demod waveform
time under Meas Setup -> Time or under Sweep -> Sweep/Control. An interpolation
316 Short Range Comms & IoT Mode User's &Programmer's Reference
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