Rohde and Schwarz FSIQ26 Data Sheet

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News from Rohde & Schwarz Number 160 (1998/I V)

The FSIQ family comprises three mod­els with different frequency ranges:

• FSIQ3 20 Hz to 3.5 GHz

• FSIQ7 20 Hz to 7 GHz

• FSIQ26 20 Hz to 26.5 GHz

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.

W-CDMA measurements

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 presettings 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.

A major measurement in the frequency
domain is that of adjacent-channel
power [4]. This makes tough demands
on analyzer dynamic range, especially
when you are measuring at component

Articles

Signal Analyzer FSIQ

The ideal analyzer for the
third mobile-radio generation

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.

FIG 1 Signal Analyzer FSIQ7 for 20 Hz to
7 GHz Photo 43 185/2

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News from Rohde & Schwarz Number 160 (1998/I V)

(4.096 MHz channel bandwidth,
5 MHz channel spacing) and approx.
81 dB in the alternate channel. FIG 3
shows the dynamic range achievable
with FSIQ7. This range is determined
by the inherent thermal noise power,
the power of adjacent-channel inter­modulation products and by the SSB
phase noise power of the internal
oscillators in the adjacent channel. The
measurable adjacent-channel power is

largely influenced by the sum of these
three power components.

With a level of approx. –12 dBm at the
input mixer and an 11 dB crest factor of
the W-CDMA signal, FSIQ7 attains an
inherent adjacent-channel power ratio
(ACPR) of about 75 dBc. This not only
meets current standard requirements
for mobile and base stations with a
comfortable margin but also allows
measurements on submodules. The
routines offered for adjacent-channel
power measurements on W-CDMA
signals allow up to seven channels to
be covered in a single sweep (power of
transmit channel and power of three
adjacent channels above and below
transmit channel).

Measurement of spurious emissions

makes exacting demands on analyzer
dynamic range in any type of trans­mission system. High power levels have
to be handled (eg 20 W of a base
station), plus very low spurious emis­sion levels are specified to avoid inter­ference to other radio services. A spe­cial feature of third-generation mobile
radio is its large transmission band­width. To measure spurious emission
levels correctly, you need resolution
bandwidth of 5 MHz for example, cor­responding to the transmission band­width of the useful signal (5 MHz
at 4.096 Mchip/s transmission rate).
FSIQ not only offers the right resolution
bandwidth but, thanks to its low noise

served with close tolerances. To verify
compliance, a signal analyzer must
offer large bandwidth, highly linear
level display and fast power measure-
ment in the time domain. The FSIQ
family is well prepared to handle these
measurements on all three counts. With
measurement bandwidth of 10 MHz
and a 20 MHz A/D converter for
digitization of the video voltage, level
steps are easily followed and dis­played. Display linearity is so high that
tolerance margins can be allowed
practically exclusively for the EUT. The

Articles

or module level, where rated character­istics have to be substantially bettered
for the complete transmitter system
to meet specifications. In addition, the
instrument should have a dynamic
range 6 to 10 dB better than the EUT.
The excellent dynamic range of the
FSE family was improved even more
in FSIQ by implementing new circuit
concepts. For example, the 3rd-order
intercept point for the W-CDMA fre­quency ranges is typically 18 dBm with
FSIQ3, 20 dBm with FSIQ7 and 22 dBm
with FSIQ26. The unparalleled noise
figure of the FSE family is of course
also implemented in FSIQ. The third
parameter decisive for dynamic
range, ie the phase noise of internal
oscillators, was reduced by several dB
for carrier offsets starting from 100 kHz
(FIG 2).

These three characteristics of FSIQ
combine in FSIQ7, for example, to yield
a dynamic range for power measure­ments on W-CDMA signals of approx.
75 dB in the adjacent channel

figure, also the dynamic range neces­sary for measuring spurious emissions
without any additional equipment. Only
harmonics measurements require a
simple highpass filter. The rms detector
ensures accurate, fast and stable meas­urements of spurious emissions (FIG 4).

To achieve optimum capacity in a
CDMA radio network, it is essential
to regulate the transmit levels of all
subscribers to the lowest possible value
to avoid interference to other subscrib­ers, since they all operate on the same
channel. A base station, for example, is
capable of readjusting the transmit
power every 625 µs in steps of 1 dB.
Specified power levels are to be ob-

FIG 2 Phase noise of FSIQ7 and FSIQ26 at
500 MHz compared with FSEB30 and FSEM30

FIG 3 Comparison of achievable inherent
adjacent-channel power ratio (ACPR) of FSIQ7
and FSEB30 as function of level at input mixer

FIG 4 Measurement of spurious emissions from
50 MHz to 2 GHz with rms detector at assumed
20 W power of base station. Red line: 60 dBc
limit value; yellow trace: spurious emissions of
transmitter; blue trace: noise floor of FSIQ7 with­out input signal

110
115
120
125
130
135
140
145
150
155
160

Carrier Offset

10 kHz 30 kHz 100 kHz 300 kHz 1 MHz 3 MHz 10 MHz

Phase Noise

dBc/(1 Hz)

FSEB 30/FSEM 30

FSIQ 7/FSIQ 26

Phase Noise

FSIQ 7

FSEB 30

Thermal Noise

T.O.I.

Level at mixer

dBm2 1 1 1 1 1 -8 -6 -4 -2 0

ACPR

5

5

6

6

7

7

8

8

9

9

dBc

Inherent ACPR with a 4.096-Mc/s W-CDMA Signal at 5 MHz Channel Offset

(Crest factor = 11 dB)

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News from Rohde & Schwarz Number 160 (1998/I V)

rms detector measures power with high
precision, and timeslot measurements
are supported by software routines for
power measurements over definable
time intervals.

Modulation error measurements on
broadband signals place very high
demands on the analyzer’s amplitude
and phase distortion on the entire
signal path from RF connector through
to A/D converter. A new method for
correcting both the inherent amplitude
and phase response of the analyzer
makes for extremely low total distor­tion of FSIQ across a bandwidth of
8 MHz about the receive frequency.
This results in a very low instrument
error in signal demodulation measure­ments. For W-CDMA signals (QPSK,

4.096 Mchip/s), the typical error
vector magnitude (EVM) of less than
1% is low enough to allow even trans­mitter submodules with their stringent
specifications to be measured with high
accuracy (FIG 5). All errors relevant
to modulation such as EVM, magnitude
error, phase error, frequency error,
waveform quality factor, I/Q offset
and I/Q imbalance are tabulated for
the operator to see all information at
a glance.

The FSIQ family not only demodulates
W-CDMA signals but also general
digital modulation formats such as
BPSK, QPSK, offset QPSK, DQPSK,
π/4DQPSK, 8PSK, 16QAM, MSK,

GMSK, 2FSK, 2GFSK and 4FSK as
well as analog modulation like AM,
FM and PM. The maximum symbol rate
for digital modulation is 6.4 Msym­bol/s or 8 MHz signal bandwidth. In
addition, FSIQ offers presettings for the
main standards such as IS95 CDMA,
GSM, NADC, TETRA, PDC, PHS,
CDPD, DECT, PWT, APCO25, CT2,
ERMES, FLEX, MODACOM and TFTS.
This makes FSIQ suitable for multi­standard applications.

General applications,
remote control

Apart from its use for the third mobile­radio generation, the FSIQ family is
also an ideal choice for measurements
in general applications. Application
software is available, for example, for
measurement of noise figure (FSE-K3)
or phase noise (FSE-K4).

High internal computing power
(233 MHz Pentium processor, trans­puter and DSP network) not only results
in high display update rates but also
makes for extremely fast response in
automatic IEC/IEEE-bus operation.

Josef Wolf

REFERENCES
[1] Wolf, J.: Spectrum Analyzer FSEA/FSEB –

New dimensions in spectral analysis. News
from Rohde & Schwarz (1995) No. 148,
pp 4–8

[2] Wolf, J.: Spectrum Analyzer FSE with Option

FSE-B7 – Vector signal analysis, indis­pensable in digital mobile radio. News
from Rohde & Schwarz (1996) No. 150,
pp 19–21

[3] Wolf, J.: Spectrum Analyzer FSEM/FSEK –

Fast spectrum analysis now through to
40 GHz. News from Rohde & Schwarz
(1996) No. 152, pp 7–9

[4] Wolf, J.: Measurement of Adjacent-Channel

Power on Wideband CDMA Signals. R&S
Application Note 1EF04_0E (1998)

Articles

Condensed data of Signal Analyzer FSIQ

Frequency range 20 Hz to 3.5 / 7 / 26.5 GHz
Amplitude measurement range –155 to 30 dBm
Amplitude display range 1 to 200 dB, linear
Amplitude measurement error <1 dB up to 2.2 GHz, <1.5 dB from 2.2 to

7 GHz, <2 dB from 7 to 26.5 GHz

Modulation measurement error EVM <1% rms (typ.) for 4.096 Mchip/s

(W- CDMA)
Resolution bandwidths 1 Hz to 10 MHz in steps of 1, 2, 3, 5
Calibration autocalibration by internal routines
Display 24 cm colour TFT LC display, VGA resolution
Remote control IEC 625-2 (SCPI 1994.0) or RS-232-C

Reader service card 160/01

FIG 5 Measurement of modulation errors of
W-CDMA signal. Top: vector diagram; bottom:
list of modulation errors