Rohde & Schwarz FSIQ

The decision to implement digital wideband CDMA for the third generation of
mobile radio – following analog FM and GSM – represents a milestone not
only in transmission technology but also in the related measurement technology
because of the larger bandwidth available for transmitting data and graphics.
The FSIQ signal analyzer family was developed specially for examining the
physical parameters of wideband CDMA signals, besides supporting the
measurements used for previous transmission modes.

The instruments are follow-on developments
of Spectrum Analyzers FSEA30,
FSEB30 and FSEM30 [1; 2; 3]. These
analyzers provide the ideal basis in
terms of bandwidth and dynamic range to meet the requirements of W-CDMA
standards (ARIB and ETSI). Signal Analyzer
FSIQ (FIG 1) analyzes W-CDMA
(wideband code-division multiple access)
signals in frequency, time and
modulation domains, meeting needs
not normally fulfilled by previous instruments
at the RF interface. Essential parameters
of the analyzer are resolution
bandwidths up to 10 MHz, wide dynamic
range, fast sampling in the time
domain and capability for processing
high chip rates. The superior characteristics
of the FSIQ family become evident
when looking at the most important
measurements, for example at the RF
output of a W-CDMA base station.

For high-accuracy power measurements,
FSIQ incorporates an rms
detector that determines power within
the measurement bandwidth over a
wide dynamic range irrespective
of waveform. No software correction
factors are needed since FSIQ
measures the power correctly from
the start. It determines the power of
a signal spectrum at each test point of
a trace. The user can define the duration
of power measurement and thus
the stability of results by selecting the
appropriate sweep time.

To make measured power comparable
with results produced by a thermal
power meter, special importance is
attached to measurement accuracy. Up
to 2.2 GHz, the guaranteed absolute
level measurement uncertainty of FSIQ
is max. 1 dB (from reference level to
50 dB below reference level in the
display range). Statistical analyses of
final production reports of the FSE
family (valid also for the FSIQ family)
covering over 100 units have revealed
a measurement uncertainty of only
0.5 dB (95% confidence level). With
option FSE-B22 (Increased Level Accuracy)
this value is guaranteed. Fitted
with this option, FSIQ can in many
cases replace a power meter, thus
eliminating the need for complex mechanical
switches in automatic test
systems for example.

FSIQ features easy-to-operate software
routines with pre-settings for the
W-CDMA system for measuring power
and occupied bandwidth. It also offers
the bandwidths (5 or 10 MHz) and
detectors required for measuring the
ratio of peak power to average power
(crest factor), which is especially important
in amplifier design for W-CDMA
transmitters and receivers.