Marconi Instruments 6900 Series User manual

Ma .. coni
Instruments
RF POWER SENSORS
6900 SERIES
Instruction Manual

CONTENTS
Page
PREFACE iii
OPERA TING PRECAUTIONS iv
Chapter 1GENERAL INFORMATION 1·1
Chapter 2INSTALLATION 2-1
Chapter 3OPERATION 3-1
Chapter 5MAINTENANCE 5-1
Chapter 6REPLACEABLE PARTS 6-1
Chapter 7SERVICING DIAGRAMS 7·1
PREFACE
WARNINGS, CAUTIONS and NOTES
These terms have specific meanings in this manual:
WARNINGS contain information to prevent personal injury.
CAUTIONS contain information to prevent damage to the equipment.
Notes contain important general information.
HAZARD SYMBOLS
The meaning of symbols that appear on the equipment is as follows:-
Symbol Type of hazard Reference in manual
AStatic sensitive component Page iv
.&.
Dismantling may cause irreparable Chap. 5
damage to this unit
&.
Precision connector Page iv
SYMBOLS IN THE MANUAL
The meaning of symbols used in this manual is as follows:-
(I) Sequence of steps in a procedure.
• List of topics or items
CAPS Capitals are used to identify names of controls and panel markings.
[ ] Square brackets are used to distinguish push-button keys.
MANUAL AMENDMENT STATUS
Each page bears the date of the original issue or the date of the latest amendment. Any
changes subsequent to the latest amendment state of the manual are included on inserted sheets
coded
Cl, C2 etc.
46882-1501<
Feb.92 46882-150K
Feb.92 iii

OPERATING PRECAUTIONS
These sensors, when used with the 6950 or 6960 Series of RF Power Meters, the 6970
Power Meter or the 6200 Series of Microwave Test Sets, are protected in accordance with IEC
Safety Class I. They have been designed and tested according to IEC Publication 348 'Safety
Requirements for Electronic Measuring Apparatus', and have been supplied in a safe condition.
CAUTION - AVOIDANCE OF MEASUREMENT ERRORS
To prevent stray radiation being detected and displayed on the power meter, the sensor
should be properly terminated in 50 n(75 nfor the 6919).
Before zeroing and operating the power meter, sufficient time should be allowed for the
sensor to take up the ambient temperature of the measuring environment. Rapid temperature
changes should be avoided while operating.
CAUTION - STATIC SENSITIVE COMPONENTS
These sensors contain static sensitive components which may be damaged by handling.
CAUTION - PRECISION CONNECTOR
All Marconi Instruments Power Sensors are fitted with precision connectors. Good
connector care is essential to maintain the performance of the Power Sensor. The following
guidelines must always be adhered to when making connections:
• The connector interfaces must be clean and free of any mechanical damage.
• The connector should be measured with a connector gauge to ensure they are within
mechanical tolerance.
• Connections should be made by rotating the outer locking nut only, NEVER the
body of the device.
• Always use a torque spanner with 3.5 mm and 2.92 mm connectors.
The Warranty does not cover connector damage due to mis-use or normal wear and tear.
WARNING - TOXIC HAZ.'\RD
Many of the electronic components used in this sensor employ resins and other chemicals
which give off toxic fumes if incinerated. Appropriate precautions should therefore be taken in
the disposal of these items.
WARNING - TEMPERATURE HAZARD
When a 6930 Series sensor is used for measuring high powers the device has a high
operating surface temperature.
Chapter 1
GENERAL INFORMATION
CONTENTS
Page
FEATURES I-I
PERFORMANCE DATA I-I
SUPPLIED ACCESSORIES 1-6
FEATURES
The 6900 Series of RF Power Sensors is used with Marconi Instruments RF Power
Meters 6950 (analogue) and 6960 Series (digital), the 6970 RF Power Meter and the 6200 Series
of Microwave Test Sets. Note, however. that the
6<)30 Series of sensors can be used with the
6960A and 6960B RF Power Meters. but cannot be used with the 6960 RF Power Meter. The
sensors provide the meter with a chopped DC analogue of the RF power. and collectively they
cover a power range from -70 dBm to +35 dBm (0.1 nW to 3 W) at frequencies from 30 kHz to
40GHz.
Each sensor has an individual label showing a graph of 'calibration factor', and values of
'50 MHz reference calibration factor' and 'linearity factor'. The calibration factor appropriate to
the measurement frequency may be entered into both the 6950, 6960 Series and 6970 power
meters to enhance accuracy. The linearity factor may also be entered into the 6960 and 6970 to
compensate for non-linearity at higher powers (compensation is preset internally in the 6950).
The 6200 Series of Microwave Test Sets allow entry and storage of all the calibration data
supplied with the sensors.
A 'calibration record' giving linearity factor and calibration data to two decimal places is
also provided with each sensor.
VSWR and uncertainty values are low across the entire frequency range of the sensor.
Each sensor has a multi-way output connector for connection to the power meter via the
sensor cable that is supplied with the meter. The sensor provides high level signals to the power
meter so that the possibility of significant RF interference during measurements is negligible. A
high damage level threshold minimizes the possibility of damage to the RF unit. Damaged units
are, however, field replaceable in most cases (see Chapter 5).
Its small, light. rugged construction allows the sensor to be used confidently in bench or
field applications without the need for any mechanical support.
PERFORMANCE DATA
The specifications for the sensors are shown on the following pages.
Iv 46882-150K
Sep.93 46882-150K
Feb.93 1·1

6920 6923 6924
POWER RANGE -70 dBm to -20 dBm -70 dBm to -20 dBm -70 dBm to -20 dBm
(0.1
nWto 10 ~W)
(0.1 nW to 10 ~W)
(0.1 nW to 10 ~W)
MAX RF INPUT +26 dBm (400 mW) CW +26 dBm (400 mW) CW +26 dBm (400 mW) CW
+30 dBm (1 W) peak +30 dBm (1 W) peak +30 dBm (1 W) peak
for
2!!S
for 2 us for
2!!S
FREQUENCY RANGE 10 MHz - 20 GHz 10 MHz - 26.5 GHz 10 MHz - 40 GHz
VSWR 1.4 - 1.2
10MHz
- 40 MHz 1.4 10 MHz -
40MHz 1.58 10 MHz -40 MHz
1.2
40MHz
- 10GHz
1.15 40 MHz -100 MHz 1.15
40MHz
-100 MHz
1.35
10GHz
- 18GHz
1.12 100 MHz
2GHz 1.12
100MHz
-2 GHz
1.4 typical
18GHz
- 20GHz
1.17 2 GHz
8GHz 1.33
2GHz
-
18GHz
1.3
8GHz
-
18GHz 1.5
18GHz
33GHz
1.5
18GHz
-26.5 GHz 1.95
33GHz
-
40GHz
1.97 26.5 GHz -
40GHz
(-002 version)
DRIFT 20
~W (typical, 1 hr after 24 hr 20
~W (typical, 1 hr after 24 hr 20 J!W(typical, 1 hr after 24 hr
warm-up at constant warm-up at constant warm-up at constant
temperature) temperature) temperature)
LINEARITY FACTOR Provided
w~h sensor Provided with sensor Provided
w~h sensor
Accuracy ±1% at 25°C between ±1% at 25°C between ±1% at 25°C between
-30 and -20 dBm -30 and -20 dBm -30 and ·20 dBm
Improves by a factor of 10 Improves by a factor of 10 Improves by a factor of 10
for each lower range for each lower range for each lower range
CALIBRATiON FACTOR
Accuracy Uncertainty provided Uncertainty provided Uncertainty provided
with sensor with sensor with sensor
Resolution 0.01% 0.01% 0.01%
RF CONNECTOR Precision N-type, male, 50 nMPC 3.5 mm, male, 50 nMPC 2.92 mm, male, 50 n
SIZE &WEIGHT 104 mm long, 33.5 mm dia. 180 g 87 mm long, 33.5 mm dia. 180 g 88.5 mm long, 33.5 mm dia. 150 g
/i)
m
z
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~
s
2 GHz
16GHz
18GHz
00 ....
CD 0>
"000
. 00
<0'"
"'..:.
s
;>\ POWER RANGE
MAX
RFINPUT
FREQUENCY RANGE
VSWR
DRIFT
LINEARITY FACTOR
Accuracy
CALIBRATION FACTOR
Accuracy
Resolution
RF CONNECTOR
SIZE &WEIGHT
6930
-15 dBm to +35 dBm
(30
~Wt03W)
+37 dBm (5 W) CW
+50 dBm (100 W) peak
for 2 !!S
10 MHz -18 GHz
1.1 10 MHz -
1.18 2 GHz -
1.28
16GHz-
10 J.!W (typical, 1 hr after 24 hr
warm-up at constant
temperature)
after 24 hr warm-up at
constant temperature
Provided with sensor
-2.5% to +3.5% with 6950
-1% to +2%
w~h 6960AIB
between +25 and +35 dBm
Improves by a factor of 10
for each lower range
Uncertainty provided
with sensor
0.01%
Precision N-type, male,
50n
93 mm long, 33.5 mm dia. 190 9
6932
-15 dBm to +35 dBm
(30 J!Wto 3 W)
+37 dBm (5 W) CW
+50 dBm (100 W) peak
tor z us
30 kHz - 4.2 GHz
1.1 30 kHz 4.2 GHz
10 J!W (typical, 1 hr after 24 hr
warm-up at constant
temperature)
after 24 hr warm-up at
constant temperature
Provided with sensor
-2.5% to +3.5%
w~h 6950
-1% to +2%
w~h 6960AIB
between +25 and +35 dBm
Improves by a factor of 10
for each lower range
Uncertainty provided
with sensor
0.01%
Precision N-type, male,
50n
93 mm long, 33.5 mm dia. 190 9
6934
-15 dBm to +30 dBm
(30~Wto 1 W)
+33 dBm (2 W) CW
+45 dBm (32 W) peak
tor z us
10 MHz - 40 GHz
1.5 10 MHz - 40 MHz
1.12 40 MHz - 100 MHz
1.1 100 MHz - 2 GHz
1.15
2GHz - 12.4GHz
1.2 12.4GHz - 18GHz
1.25 18 GHz - 26.5 GHz
1.43 26.5 GHz - 40 GHz
(1.55 for version -002)
10 J!W(typical, 1 hr after 24 hr
warm-up at constant
temperature)
after 24 hr warm-up at
constant temperature
Provided with sensor
-1.5% to +3.5% with 6950
-1% to +3%
w~h 6960AlB
between +25 and +35 dBm
Improves by a factor of 10
for each lower range
Uncertainty provided
with sensor
0.01%
MPC 2.92 mm, male,
50n
87 mm long, 33.5 mm dia. 150 g
/i)
m
z
m
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~
s
z

GENERAL INFORMATION
SUPPLIED ACCESSORIES
6913,6914
N-type male / SMA female adapter (to connect to 0 dBm power reference)
6919
75 nto 50 nadapter (to connect to 0 dBm power reference)
6920
30 dB precision attenuator - for use in calibration
Attenuation: 30 dB ±0.05 dB at 50 MHz at 25°C
6923,6924
30 dB precision attenuator - for use in calibration
Attenuation: 30 dB ±0.05 dB at 50 MHz at 25°C
N-type male / SMA female adapter to connect to 0 dBm power reference
6934
N-type male / SMA female adapter
Part No.
23443-822K
23443-842W
06920-023P
06920-023P
23443-822K
Chapter 2
INSTALLATION
UNPACKING AND REPACKING
Retain the packing materials and the packing instruction note (if included) in case it is
necessary to reship the sensor.
If the sensor is to be returned for servicing attach a label indicating the service required,
type number, serial number and your return address.
If the original container or materials are not available use a strong double-wall carton
packed with shock absorbing material around all sides of the sensor to hold it firmly.
The 001 versions of the 40 GHz power sensors (i.e. 56914-001, 56924-001 and 56934-001) are
supplied with accessories as above. The 002 versions also include a waveguide 22 transformer
and calibration table.
OPTIONAL ACCESSORIES
The following items are required when using the 6920 and 6930 series sensors with the
6950 RF Power Meter. They are available from the Service Unit (address on rear cover of this
manual).
6920Series
Range scale (-65 to -20 dB!TI) for attaching
magnetically to the 6950 range control.
6930Series
Range scale (-10 to +35 dBm) for attaching
magnetically to the 6950 range control.
1-6
06920-008L
41179-028M
46882-150K
Feb.93 46882-150K
Feb.92 2-1

INSTALLATION
BlankPage
Chapter 3
OPERATION
CONTENTS
Page
PREPARATION FOR USE 3-1
WITH 6950 POWER METER 3-2
Zeroing 3-2
Calibration 3-2
Linearity Factor Correction for 6920 Series Sensors 3-3
WITH 6960 SERIES POWER METER 3-3
Zeroing 3-3
Calibration , 3-3
WITH 6970 POWER METER 3-4
Zeroing 3-4
Calibration 3-4
WITH 6200 SERIES OF MICROWAYE TEST SETS 3-5
PREPARATION FOR USE
Note...
The 6930 Series power sensors can only be used with the 6950, 6960N6960B and 6970
RF Power Meters, and also the 6200 Series of Microwave Test Sets. They cannot be
used with the 6960 RP Power Meter.
Before making measurements, the power meter must be matched to the individual
characteristics of the sensor. This entails the following procedures:
• Zeroing the meter.
• Calibration, that is, entering the sensor's calibration factor and linearity factor.
Note...
If the sensor has been stored at a temperature different from that of the measurement
environment, allow sufficient time for thermal equilibrium to be established before
zeroing or calibration. Avoid rapid temperature changes while operating.
WARNING
When using 6930 Series sensors, dissipation of the applied power can cause the sensor to
have a high surface temperature. Take care when handling.
CAUTION
Avoid applying excessive torque when tightening RF connectors or damage may occur.
Finger-tight is usually sufficient, especially for type N connectors. If a torque wrench is
used for 3.5 mm and 2.92 mm connectors, set it to break at 1 Nm (8 Ib in).
246882-150K
Feb. 92 46882-150K
Sep.93 3-1

OPERATION OPERATION
The power meter can now be used for measuring RF power. For full instructions and
uncertainty calculations, refer to the power meter Operating Manual, Chapter 3.
Linearity Factor Correction for 6920 Series Sensors
At -20 dBm, corrected reading =Displayed reading +Correction Factor
where Correction Factor =Sensor Lin Factor - 8%
For each 3 dB decrease in power level, this correction figure should be halved. At
-30 dBm or lower the error will be negligible and the above correction is not necessary.
The linearity factor of 6920 Series sensors can vary from unit to unit. Since the 6950 has
two preset linearity factor correction values, measurement errors will result when using 6920
Series sensors with a linearity factor that is significantly different from this value, and when the
power level is above -30 dBm. If necessary, the displayed reading can be corrected to give a
more accurate power measurement figure, as follows:
Adjust the ZERO control for zero reading on the meter, using the special tool
provided with the power meter.
With no power applied to the sensor, select the most sensitive range by turning the
RANGE switch fully counter-clockwise.
Connect the sensor to the SENSOR INPUT socket of the power meter using the
sensor cable supplied with the power meter.
(2)
(3)
It may be helpful in setting zero to adjust the RESPONSE TIME control on the rear panel
to reduce noise. You may also find it easier to set zero first on a less sensitive range, as
slight adjustments of the ZERO control have considerable effect on the most sensitive
range.
Hint...
WITH 6950 POWER METER
Zeroing
(1)
With no power applied to the sensor, press [AUTO ZERO]. Five dashes appear
on the display, representing the power meter's five ranges. When the last of these
disappears, all five ranges have been zeroed. This takes approximately 25
seconds.
Connect the sensor to the SENSOR INPUT of the power meter, using the sensor
cable supplied with the pow.ermeter.
(2)
WITH 6960 SERIES POWER METER
Zeroing
(1)
(2) Attach the appropriate magnetic range scale to the skirt of the RANGE switch if
required and set the switch to 0 dBm.
Use the N-type to SMA adapter for 6913/6914/6934
Use the 75 Qto 50 Qadapter for 6919
Use the 30 dB pad for 6920
Use the 30 dB pad and N-type to SMA adapter for 6923/6924
Calibration
(1) Connect the sensor to the POWER REFERENCE output of the power meter.
(5) Adjust the GAIN control for full-scale meter reading.
(3) Set the CAL FACTOR control to the value of the reference calibration factor
given on the sensor label. Some sensors, e.g. the 6910, do not have this
information on the label; in these cases the default value of 100% is assumed.
(4) On the rear panel, switch POWER REF to ON and the
UN F : 6%/8% switch to
the setting which is nearest to the value of the linearity factor shown on the
sensor label or its calibration data chart. (If the
UN F switch positions on your
6950 are designated 75 Qand 50 Q, these should be interpreted as 6% (75 Q) and
8% (50
Q) and the switch set accordingly as above.)
(6)
(7)
Switch POWER REF off and disconnect the sensor from the POWER
REFERENCE socket.
Determine the calibration
factor for the measurement frequency, whether from
the graph on the sensor label or from its calibration data chart. Set the CAL
FACTOR control to the same value.
Calibration
(1) Determine the linearity factor, either from the label on the sensor or from its
calibration data chart, Press [UNEARITYFACTOR] and enter this value in the
power meter.
(2) Connect the sensor to the POWER REFERENCE output of the power meter.
Use the N-type to SMA adapter for 6913/6914/6934
Use the 75 Qto 50 Qadapter for 6919
Use the 30 dB pad for 6920
Use the 30 dB pad and N-type to SMA adapter for 6923/6924
(3) Press [CAL FACTOR] and enter the value of the reference calibration factor
given on the sensor label. Some sensors, e.g. the 6910, do not have this
information on the label; in these cases the default value of 100% is assumed,
3-2 46882-150K
Feb. 93
46882-150K
~~ N

OPERATION
(4) Press [AUTO CAL]. Note that the POWER REFERENCE LED comes on and
'CAL' is displayed. The auto cal routine takes approximately 10 seconds for most
sensors, the 6930 Series requiring about 45 seconds.
(3)
OPERATION
Press [CAL FACTOR] and enter the value of the reference calibration factor
given on the sensor label. Some sensors, e.g. the 6'J 10, do not have this
information on the label; in these cases the default value of
IOO'lf, is assumed.
Press [ONIENTER] to activate the instrument.
(5) When calibration is completed, you can check that it has been successful by
pressing [POWER REF]. This switches the power reference signal on, and 0
dBm
(I mW) should be displayed.
(6) Press [POWER REFI again to switch off the power reference signal and
disconnect the sensor from the POWER REFERENCE socket.
(7) Determine the calibration factor for the measurement frequency, either from the
graph on the sensor label or from its calibration chart. Press [CAL FACTOR] and
enter this value in the power meter.
The power meter can now be used for measuring RF power. For full instructions and
uncertainty calculations, refer to the power meter Operating Manual, Chapter 3.
WITH 6970 POWER METER
Zeroing
(I)
(4) When calibration is completed, you can check that it has been successful by
pressing [SHIFT} [PWR. REF]. This switches the power reference signal on, and
odBm (I mW) should be displayed.
(5) Press [SHIFT] [PWR. REF] again to switch off the power reference signal and
disconnect the sensor from the POWER REF socket.
(6) Determine the calibration
factor for the measurement frequency, either from the
graph on the sensor label or from its calibration chart. Press lCAL FACTOR] and
enter this value in the power meter.
The power meter can now be used for measuring RF power. For full instructions and
uncertainty calculations, refer to the power meter Operating Manual, Chapter 3.
WITH 6200 SERIES OF MICROWAVE TEST SETS
For calibration instructions, refer to Chapter 3 of the 6200 Operating Manual.
Calibration
(I)
(2)
(3)
Connect the sensor to the SENSOR INPUT of the power meter, using the sensor
cable supplied with the power meter.
With no power applied to the sensor, press [SHIFT] [ZERO]. The display will be
cleared and the peaking meter bar will progress across the display during the
zeroing sequence. On completion the instrument will be restored to normal
operation.
Determine the linearity factor, either from the label on the sensor or from its
calibration data chart. Press
[UN FACTOR] and enter this value in the power
meter.
Note... For the best measurement accuracy, the sensor should be calibrated against the optional
integral power reference, immediately following a sensor zero. as described in steps (2)
to (5). An external power reference may be used if the power reference option is not
fitted.
(2) Connect the sensor to the POWER REF output of the power meter
Use the N-type to SMA adapter for 6913/6914/6934.
Use the 75 nto 50 nadapter for 6919.
Use the 30 dB pad for 6920.
Use the 30 dB pad and N-type to SMA adapter for 6923/6924.
3-4 46882-150K
Feb.93 46882-150K
Feb.93 3-5

Chapter 4
TECHNICAL DESCRIPTION
CONTENTS
Page
OVERALL CIRCUIT DESCRIPTION 4-1
DETAILED DESCRIPTION 4-2
RF Sensor 4-2
Signal chopper 4-2
Amplifier 4-2
LIST OF FIGURES
Fig. 4-1 Block Diagram of RF Power Sensor 4-1
Fig. 4-2 Simplified Diagram of Amplifier 4-2
OVERALL CIRCUIT DESCRIPTION
Refer to Fig. 4-I. The RF sensor gives a small DC output voltage when RF power is
applied. This DC voltage is converted to an AC signal by the signal chopper. The chopped
signal is fed to the amplifier which is divided into two parts, the first part being in the power
sensor and the other in the power meter. The signal is then processed by the power meter to give
a power reading. A Zener diode in the power sensor provides sensor type information for the
power meter.
Sensor
Meter
RF
SENSOR
P~~er -11.- _
Power Reading
Chopper Drive
Zero Control
Sensor Type
•
[illl------;-.-
Zener
Fig. 4-1 Block Diagram. of RF Power Sensor
46882-150K
Feb. 92 4-1

TECHNICAL DESCRIPTION
DETAILED DESCRIPTION
Refer to Chapter 7 for the circuit diagram of the sensor.
RF Sensor
For the 6910 Series and 6930 Series sensors, the sensing element consists of a monulithic
semiconductor thermocouple element. The 6920 Series uses a Schottky barrier diode. Both
types of sensor provide an output voltage proportional to the RF power.
Signal chopper
The signal chopper consists of two field-effect transistors which act as a sampling gate.
The sampling rate is controlled by a 925 Hz squarewave signal from the power meter. The
output of the signal chopper is a 925 Hz square wave with amplitude proportional to the RF input
power.
A zero control signal from the power meter is introduced at the input of the signal
chopper. This allows the power meter to cancel any residual output that occurs with no RF power
applied.
Amplifier
The amplifier is divided between the power sensor and the power meter. A simplified
circuit is shown in Fig. 4-2.
.Ve
---------..,
Meter
Sensor
TECHNICAL DESCRIPTION
The amplifier has a gain of approximately 1000 and a band-pass characteristic centred at
the sampling rate of 925 Hz. For a full description of the amplifier refer to the appropriate
power meter Service Manual.
A Zener diode is mounted in the sensor to provide sensor type information for the power
meters. The Zener voltage is detected by the power meter and indicates the type of sensor in use.
This in turn defines the required scaling and linearity corrections that must be applied to give a
true power reading.
Ch_
Signal
4-2
Output
-Ve
Fig. 4-2 Simplified Diagram of Amplifier
46882-150K
Feb.92 46882-150K
Feb.92 4-3