Universal Radio Communication Tester CMU200

First WCDMA measurement functions

After providing support for the most Main parameters of a and <– 50 dBm which corresponds
WCDMA mobile phone to a dynamic range of more than
important 2nd-generation mobile 83 dB. The individual power levels
The most important parameter is the (1/2/3 dB) must be accurately met.
radio standards such as GSM, IS136, transmit power of the uplink signal:
• To ensure proper performance of the The CMU200 measures this dynamic
AMPS and CDMA [1], [2], mobile phone, it is essential that the range with different measurement band-
maximum transmit power (+33 dBm widths for the maximum and the
Rohde & Schwarz now presents the +1/–3 dB) is accurately met. If the minimum/off power. The excellent level
transmit power is too high, too much measurement accuracy and linearity of
CMU200 as a tester for mobile current will be drained from the bat- the CMU200 are a great advantage in
tery and other mobile phones in the this case.
phones to the WCDMA (3GPP/FDD) network will be disturbed. If it is too
low, the coverage range or the QoS is Another important parameter is the
standard*. The first functions reduced. modulation quality. If the modulation
• The mobile phone must be able to quality is poor, bit errors and mutual
described in this article carry out reduce its transmit power below a interference of the code channels will
defined maximum level (<–50 dBm). occur. The error vector magnitude (EVM)
transmitter measurements on • When inactive, the mobile phone and the frequency error are measured.
should not exceed a defined off power I/Q errors, i.e. I/Q origin offset and
WCDMA uplink signals. (–56 dBm). I/Q imbalance, can be analyzed at the
• As with CDMA systems, accurate baseband level. They indicate a malfunc-
power ramping is also essential tion of the I/Q modulator. A typical
in WCDMA systems. With WCDMA, parameter of WCDMA is the peak code
* Abbreviations in the text are explained in the the mobile phone should send at domain error (PCDE). To measure this
box on page 15. a power level between +33 dBm error, the total error vector is divided

FIG 1 Graphical display of modulation analysis FIG 2 Code domain power

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 MOBILE RADIO Radiocommunication testers

among the individual code channels. The FIG 2 shows a CDP measurement with Because of national requirements, addi-
code domain error is the ratio of the aver- the CMU200. The CDP of the control tional spectrum characteristics are spec-
age code power to the average power channel (DPCCH) and of the six possible ified by the 3GPP standard: the spec-
of the reference signal. The PCDE is the data channels (DPDCH) of a mobile trum emission mask (continuous spec-
maximum code domain error that occurs phone is displayed. In the example, the trum measured at 30 kHz and 1 MHz
for all codes within a timeslot. CDP of the data channels is reduced bandwidths, FIG 6) and the occupied
by 10 dB with reference to the control bandwidth (bandwidth covering 99 % of
Results of modulation analysis are dis- channel. the total signal power). These measure-
played on the CMU200 graphically ments are an integral part of the ACLR
versus time (FIG 1) or as numeric values analysis in the CMU200.
in an overview menu. Frequency spectrum

The frequency spectrum of the WCDMA A test platform with proven

Code domain power signal generated by the transmitter characteristics
limits the system performance. If a
Since data and control channels of mobile phone exceeds the frequency As defined by the standard, the CMU200
WCDMA/FDD are separated by different range assigned to it, other subscribers or always considers a whole timeslot which
codes that are mutually orthogonal, it services will be disturbed. The 3GPP stan- is 666 µs long and contains 2560 chips.
is important for the analysis that the dard defines an adjacent-channel leak- Free running and external triggering
signal sent by the DUT can be split age ratio (ACLR) measurement where modes are provided so that continuous
up again into the code channel com- the power of adjacent channels (±5 MHz or one-shot measurements can be taken.
ponents used. The power of one of offset from frequency used) and of alter-
these code channels is referred to as nate channels (±10 MHz) is measured. Statistical evaluation is possible by
the code domain power (CDP) (see also The CMU200 displays a continuous fre- recording average, maximum and mini-
[3] and [4]). quency spectrum with a span of 25 MHz mum values for a selectable number of
(FIG 3) and the integrated power values timeslots.
of the four adjacent channels (FIG 4).
The CMU200 naturally offers a sufficient Markers (absolute and relative) as well
dynamic range for the measurement as auxiliary marker lines facilitate the
(FIG 5). reading of measured values in the dis-

FIG 3 ACLR displayed as continuous frequency spectrum FIG 4 ACLR in adjacent channels

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play menus. Tolerances can be set for • Remote-control capabilities
REFERENCES
go/nogo evaluation. Results violating a correspond to those of the CMU basic [1] CMU 200 – Adding CDMA now provides full
tolerance limit are displayed on a red unit. Know-how acquired in the gen- 2G capability. News from Rohde & Schwarz
background. eration of remote-control programs for (2001) No. 170, pp 7–11
[2] CMU 200 – Successful mobile-radio tester
other function groups can therefore now with US TDMA and AMPS standards.
Using the CMU200 platform for WCDMA be directly utilized. News from Rohde & Schwarz (2000)
has great advantages: No. 168, pp 10–15
[3] Signal Analyzer FSIQ – Ready for all mea-
• The CMU200 is a multistandard tester, surements on 3GPP base station transmit-
i.e. measurement functions for all Functions planned for the future ters. News from Rohde & Schwarz (2001)
essential standards can be imple- No. 170, pp 15–17
[4] Signal Generator SMIQ – Fit for 3G with
mented. Switching from one standard The evolution of the CMU200 advances new options. News from Rohde & Schwarz
to another takes only a few seconds. at a great pace: (2000) No. 166, pp 10–12
• A flexible hardware and software • Measurements of power ramping
ADDITIONAL REFERENCES
update concept for the integration of versus time (inner loop power) – See box on page 12
additional WCDMA functionality levels • WCDMA generator for synchronizing
or for the adaptation to changes in the mobile phones and for BER measure-
3GPP standard. ments Abbreviations used
• The CMU200 has proven its great reli- • Signalling for call setup and call clear- ACLR Adjacent channel leakage
power ratio
ability, high measurement speed and down as well as loop-back for BER
CDP Code domain power
accuracy as well as signal quality in measurements. EVM Error vector magnitude
many production lines. Gottfried Holzmann FDD Frequency division duplex
• Low weight and compact design make ME Magnitude error
it easy to handle. OBW Occupied bandwidth
PCDE Peak code domain error
• The well-known menu structure which PE Phase error
provides easy operation of the QoS Quality of service
CMU200 is used for the WCDMA SEM Spectrum emission mask
option. Users familiar with operating TDD Time division duplex
WCDMA Wideband code divison multiple
the CMU200 in another network, e.g.
access
GSM, will have no problems using 3GPP 3rd generation partnership
WCDMA. project

FIG 6 Spectrum emission mask

Minimum requirements Guaranteed dynamic

Mobile phone Base station range of CMU200
Adjacent channel 33 dB 45 dB 54 dB
Alternate channel 43 dB 50 dB 62 dB

FIG 5 Dynamic range of CMU 200 with comfortable margin

Condensed data of WCDMA option for CMU200

Standard 3GPP-FDD, testing mobile phones
Frequency range specified: 1920 MHz to 1980 MHz
unit functioning: 10 MHz to 2700 MHz
Measurement capabilities
Power measurements Max / Min /Off
Modulation analysis EVM, ME, PE, freq error, I/Q offset, I/Q imbalance, rho, PCDE
Code domain power CDP / rho value
Spectrum measurement ACLR, OBW, SEM
Order designation U65 / K65

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News from Rohde&Schwarz Number 171 (2001/II)