R&S FSL WLAN TX Measurements (Option K91)
1300.2519.12 2.135 E-11
This description gives a rough overview of the signal processing concept of the IEEE 802.11b
a
pplication.
A block diagram of the measurement application is shown in Fig. 2-88. The baseband signal of an IEEE
802.11b wireless LAN system transmitter is sampled with a sampling rate of 44 MHz.
Fig. 2-88 Signal processing of the IEEE 802.11b application
The first task of the measurement application is to detect the position of the bursts within the
measurement signal
)(
1
vr . The detection algorithm is able to find the positions of the beginning of
short and long bursts and can distinguish between them. The algorithm also detects the initial state of
the scrambler. This is required if IEEE 802.11 signals should be analyzed, because this standard does
not specify the initial state of the scrambler.
With the knowledge of the start position of the burst, the header of the burst can be demodulated. The
bits transmitted in the header provide information about the length of the burst and the modulation type
used in the PSDU.
After the start position and the burst length is fully known, better estimates of timing offset, timing drift,
frequency offset and phase offset can be calculated using the entire data of the burst.
At this point of the signal processing a demodulation can be performed without decision error. After
demodulation the normalized and undisturbed reference signal
)(vs is available.
If the frequency offset is not constant and varies with time, the frequency– and phase offset in several
partitions of the burst must be estimated and corrected. Additionally, timing offset, timing drift and gain
factor can be estimated and corrected in several partitions of the burst. These corrections can be
separately switched off in the demodulation settings menu.
Knowing the normalized power and undisturbed reference signal, the transmitter baseband filter is
estimated by minimizing the cost function
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