Power Sensors ¸NRV-Z
Data sheet
Version
04.00
October
2004
◆ Thermal sensors and diode sensors
for high-precision power measurements
◆ Compatible with ¸NRVS,
¸NRVD, ¸URV35 and
¸URV55 base units
◆ Frequency range DC to 40 GHz
For RF and microwave power measurements
◆ Power range 100 pW to 30 W
◆ Standards:
GSM900/1800/1900, DECT, cdmaOne,
CDMA2000®,
DAB, DVB, etc
◆ Absolute calibration, simply plug in
and measure
WCDMA, NADC, PDC,
◆ Calibration data memory for sensor-
◆ High long-term stability
◆ Excellent temperature response
specific parameters
With its large variety of power sensors,
Rohde&Schwarz is able to provide the
right tool for power measurements with
¸NRVS, ¸NRVD, ¸URV35
and ¸URV55 base units.
15 different types of power sensors in all
cover the frequency range from DC to
40 GHz and the power range from
100 pW (−70 dBm) to 30 W (+45 dBm). In
addition to thermal sensors, which are
ideal as a high-precision reference for
any waveform, diode sensors with a
dynamic range of more than 80 dB are
available.
The peak power sensors of the
¸NRV-Z31/-Z32/-Z33 series allow
power measurements on TDMA mobile
phones to different digital standards as
well as measurement of the peak power
of pulsed or modulated signals.
Plug in and measure
With the individually calibrated sensors
of the ¸NRV-Z series plugged into
the base unit, a fully calibrated power
meter is immediately ready for measurements – without need for entering
calibration factors and without adjustment to a 50 MHz reference: this means a
great benefit in the routine research and
development work and an error source
less when changing the sensor. These
assets are brought about by the calibration data memory
Rohde&Schwarz which contains all the
relevant physical parameters of the sensors, and the excellent long-term stability of
the Rohde&Schwarz power sensors.
Rohde&Schwarz is the world’s only manufacturer to provide absolute calibration
for its power sensors.
first introduced by
The right sensor for every application
Terminating power sensors are used for
power measurements on a large variety
of sources. The requirements placed on
the sensor regarding frequency and
power range, measurement accuracy and
speed may therefore differ a great deal.
Four classes of power sensors allow optimum adaptation to the specific measurement task:
◆ Thermal power sensors
¸NRV-Z51/-Z52/-Z53/-Z54/-Z55
◆ High-sensitivity diode sensors
¸NRV-Z1/-Z3/-Z4/-Z6/-Z15
◆ Medium-sensitivity diode sensors
¸NRV-Z2/-Z5
◆ Peak power sensors
¸NRV-Z31/-Z32/-Z33
Thermal power sensors
The thermal power sensors of the
¸NRV-Z51 to ¸NRV-Z55 series
satisfy the most stringent demands
placed on measurement accuracy and
matching. They cover the power range
from 1 µW (−30 dBm) to 30 W (+45 dBm)
and the frequency range from DC to
40 GHz.
These sensors are capable of measuring –
without any degradation of the measurement accuracy – the power of CW signals
as well as the average power of modulated or distorted signals by RMS weighting of all spectral components within the
specified frequency range. Therefore,
thermal sensors are the first choice for
power measurements at the output of
power amplifiers and on carrier signals
with modulated envelope. Needless to
say that the linearity of the sensor is independent of frequency, ambient temperature and waveform, and with 0.5% or
0.02 dB its contribution to the measurement uncertainty of the ¸NRV-Z51/
-Z52/-Z55 sensors is negligible.
High-sensitivity diode sensors
The ¸NRV-Z1/-Z3/-Z4/-Z6/-Z15
high-sensitivity power sensors based on
zero-bias Schottky diodes open up the
power range below 1 µW down to the
physical limit of 100 pW (−70 dBm). In
this range, from −70 dBm to −20 dBm,
their behaviour is much the same as that
of thermal sensors, i.e. precise measurement of the average power of modulated
signals, RMS weighting of harmonics and
linearity independent of temperature and
frequency.
2 Power Sensors ¸NRV-Z
Peak envelope power (PEP)
Average burst power (pulse power
Pp =
Power
0
Burst width
Definition of the main power parameters using the transmitter signal of an NADC mobile station as an example; the average burst power can be
displayed on the ¸NRVS, ¸NRVD and ¸URV 55 base units after entering the duty cycle t
measure the average power P
t
p
, i.e. a thermal sensor or a diode sensor operated in the square-law region
avg
Average power (
All high-sensitivity sensors from
Rohde&Schwarz are calibrated to allow
precise power measurements also outside the square-law region up to a power
T
P
⋅
avg
t
p
P
)
avg
Burst period
T
earity, greater measurement uncertainties than with thermal sensors are to be
expected in this region due to frequency
and temperature effects.
of 20 mW (+13 dBm). The high signal-tonoise ratio of the sensor output signal in
this region makes for very short measurement times. It should however be noted
that the response of high-sensitivity sensors outside the square-law region differs
from that of thermal sensors so that only
spectrally pure signals with unmodulated
envelope (CW, FM, ϕM, FSK, GMSK) can
be measured. Regarding the display lin-
Medium-sensitivity diode sensors
The ¸NRV-Z2 and ¸NRV-Z5
medium-sensitivity sensors based on
diode sensors with 20 dB attenuator pad
close the gap between the thermal and
the high-sensitivity sensors in applica-
tions where in the power range between
−20 dBm and 0 dBm both high measure-
ment speed and the thermal sensor char-
acteristics are required at a time.
Pp)
Time
/T; required is a sensor that is able to precisely
p
Given a continuous load capability of 2 W,
this type of sensor is extremely robust.
Peak power sensors The ¸NRV-Z31/¸NRV-Z32/ ¸NRV-Z33 peak power sensors take
a special place among diode sensors.
They enable measurement of the peak
envelope power (PEP) of modulated signals during signal peaks of 2 µs to 100 ms
duration. They thus open up a large variety of applications, from the measurement of pulsed transmit power of TDMA
mobile phones through special measurement tasks in applied physics to the
measurement of sync pulse power of
terrestrial TV transmitters. Peak power
sensors from Rohde&Schwarz are available for the frequency range 30 MHz to
6 GHz in the power classes 20 mW
(¸NRV-Z31), 2 W (¸NRV-Z32)
and 20 W (¸NRV-Z33), the latter for
direct power measurement at output
stages.
Power Sensors ¸NRV-Z 3
DC to 40 GHz/100 pW to 30 W – GSM900/1800/1900, DECT,
Various models within a power class
allow the handling of versatile waveforms:
◆ Model .02 (of the ¸NRV-Z31) and
model .05 (of the ¸NRV-Z32) are
designed for general-purpose applications and are suitable for measuring
the power of RF bursts from 2 µs
width and at repetition rates from
10/s (¸NRV-Z31/model 02) and
25/s (¸NRV-Z32/model 05).
◆ Model .03 (high-speed model of the
¸NRV-Z31/¸NRV-Z33) can be
used at repetition rates from 100/s.
Due to its higher measurement speed
it is ideal for system applications and
measurement of the sync pulse power of negatively modulated TV signals
in line with the relevant standards for
terrestrial television (NTSC, ITU-R,
British and OIRT). The picture content
has no effect on the measurement
result, while the effect of the sound
carrier can be compensated using
tabulated correction factors.
◆
Models .04
of all peak power sensors
are tailored to the requirements of
TDMA radio networks and enable measurement of the transmit power of
TDMA mobile stations to GSM and
DECT stan
dards.
The following table serves as a guide in choosing the suitable sensor for digital modulation:
Modulation Time structure Application Suitable sensor Measured
parameter
GMSK, GFSK, 4FSK
(unmodulated envelope)
QPSK, OQPSK continuous
OFDM continuous DVB-T/DAB transmitters ¸NRV-Z51 to -Z55 P
π/4DQPSK, 8PSK,
16QAM, 64 QAM
symbol rate: any
π/4DQPSK, 8PSK,
16QAM, 64 QAM
symbol rate <25 ksps
continuous
one timeslot active,
frame length <10 ms
continuous
continuous
one timeslot active,
frame length ≤40 ms
4 Power Sensors ¸NRV-Z
GSM, DECT base stations;
same power in all timeslots
GSM, DECT mobile stations
cdmaOne, CDMA2000®, WCDMA base
stations
NADC, PDC, PHS, TETRA base stations;
same power in all timeslots
NADC, PDC, TETRA base stations;
same power in all timeslots
NADC, PDC mobile stations
all sensors,
without any restrictions
¸NRV-Z31/-Z32/-Z33
model .04
¸NRV-Z51 to -Z55 P
¸NRV-Z51 to -Z55 P
¸NRV-Z31/-Z32/-Z33
models .02/.03/.05
¸NRV-Z32, model .05 PEP 43 dB
¸NRV-Z51 P
P
avg
Pp (PEP)
avg
avg
avg
PEP 43 dB
p
For footnotes see end of data sheet.
1)
Dynamic range
50 dB to 80 dB
43 dB
50 dB
50 dB
50 dB
40 dB
cdmaOne, CDMA2000®, CDMA, WCDMA, NADC, PDC, DAB, DVB...
The right sensor for digital modulation
There are two main features of digitally
modulated signals that have to be considered in power measurements:
◆
The pulsed envelope power to CDMA,
DAB and DVB standards and all standards prescribing the modulation
modes PSK, QAM and
NADC, PDC, PHS and TFTS) requires a
differentiation between average power and peak power.
All thermal power sensors can be
used without any restrictions for
average power measurements. Diode
sensors may be used, provided they
are operated inside the square-law
region. The peak power sensors of the
¸NRV-Z31/¸NRV-Z32/
¸NRV-Z33 series (models .02, .03
and .05) are suitable for measuring
the peak value at symbol rates of up
to 25 ksps.
π
/4DQPSK (e.g.
Precision calibration
A power sensor can only be as precise as
the measuring instruments used for its cal-
ibration. Therefore, the calibration stand-
ards used by Rohde& Schwarz are directly
traceable to the standards of the German
Standards Laboratory.
All data gained in calibration as well as
the essential physical characteristics of
the sensor, e.g. temperature effect, are
stored in a data memory integrated in the
sensor and can be read by the base unit
and considered in the measurements.
Since all Rohde&Schwarz power sensors
feature absolute calibration, measurements can be started immediately
after plugging the sensor into the base
unit without prior calibration to a 1 mW
reference source. To activate the frequency-dependent calibration factors all
the user needs to do is to enter the test
frequency on the base unit.
◆ In the case of transmission standards
using TDMA structure, such as GSM,
DECT, NADC, PDC or PHS, the data
stream for a channel is compressed to
fit into one of several timeslots, so
that the power measurement has to
be carried out in a certain time interval. In the case of one active timeslot
in the transmit signal (mobile station),
the peak power sensors of the
¸NRV-Z31/¸NRV-Z32/
¸NRV-Z33 series can be used,
with models .02, .03 and .05 being
suitable for measuring the peak power and model .04 for measuring the
average transmit power (GSM and
DECT only).
Power sensors are calibrated to the
power of the incident wave;
this ensures that with a matched
source the available source power into
50 Ω (or 75 Ω) is measured;
with a mismatched source, the power
of the incident wave will differ from
the available power according to the
mismatch uncertainty
Power of
incident
wave
Reflected
power
(frequencydependent)
Calibration of the ¸NRV-Z sensors is directly traceable to the standards of the German Standards
Laboratory
Feed line loss
(frequency-dependent)
Detectable
power
T
U
Thermocouple
sensor
Termination plane
Reference plane of sensor
Power Sensors ¸NRV-Z 5
Measurement accuracy and matching
The accuracy of power measurements is
determined by diverse parameters, such
as the measurement uncertainty in calibration, linearity or ambient temperature:
parameters whose effect can directly be
specified. In contrast, the effect of a mismatched power sensor can only be estimated if the source matching is known.
Mismatch of source and sensor causes
the device under test – the source – to
supply a somewhat higher or lower
power than for an exactly matched output. As shown in the graph on the right,
the resulting measurement error can be
several times greater than the measurement errors caused by all other
parameters. Power sensors from
Rohde&Schwarz therefore feature
excellent matching to ensure optimum
measurement accuracy even under conditions of strong reflections.
1.5
0.16 dB (3.6%)
0
.2 dB (4.6%)
0
.1
dB (2
1.2
sensor
1.1
SWR
0
.00
1.05
1.02
1.02
Maximum measurement error due to mismatch for source power available into 50 Ω (75 Ω);
values stated in dB and in % of power in W
Example shown:
Power measurement on a source with an SWR of 1.5; a sensor with excellent matching with
1.05 SWR (e.g. ¸NRV-Z5) generates a measurement error of as little as 0.04 dB (1%), while
an SWR of 1.2 would result in a measurement error four times greater
5
dB (0.1%)
1.05 1.1 2.0
0.0
1
dB (0.2%)
0.0
2
dB (0.5%)
0
.05
SWR
dB (1
.3%)
.2%)
0.04 dB (1%)
1.5
source
The base units
All power sensors can be used with the
following base units:
¸NRVD
◆ Modern dual-channel power meter
◆ Menu-guided operation
◆ IEC/IEEE-bus interface (SCPI)
◆ Ideal for relative measurements in
two test channels (attenuation,
reflection)
◆ Large variety of measurement
functions
◆ Result readout in all standard units
◆ Many extras like 1 mW test genera-
tor, indication of measurement uncertainty, etc
¸NRVS
◆ Cost-effective, single-channel power
meter
◆ Manual operation like ¸NRVD
◆ Many measurement functions
◆ Result readout in all standard units
◆ Analog output fitted as standard
◆ IEC/IEEE-bus interface (syntax-com-
patible with ¸NRV/¸URV5)
6 Power Sensors ¸NRV-Z
¸NRVD
¸NRVS
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