Post on 19-Aug-2020
RF and Microwave PowerMeasurement
Murat Celep, UME
Martin Hudlička, CMI
Contact: murat.celep@tubitak.gov.tr
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
• RF power
• RF power traceability
• Diode sensor
• Skin effect
• Connectors
Contents
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS2
• Electrical power is defined as quantity of dissipated energy per unit of time.
• The SI (International System of Units ) unit of power is the Watt.
• In the case of resistive (Ohmic, or linear) load, power that is dissipated at a load can be defined as a product of voltage on the load and current passing through a circuit.
P=VI
RF Power
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS3
RF Power
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
dttT
itT
vnT
dttitvnT
P
nT
pp
nT
)2
(sin.)2
sin(1
)().(1
∫∫00
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RF Power
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Properties of Power Sensors:
• Sensitivity
• Frequency range
• Power range
Microwave power is measured by sensors.
Power Sensor Types:
• Bolometer
Barretter
Thermistor
• Thermocouple
• Diode
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RF Power
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Microwave power traceability is obtained over power sensors.
http://www.powerbackup.co.za/about-us/
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• RF power
• RF power traceability
• Diode sensor
• Skin effect
• Connectors
Contents
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS7
RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS8
Microwave power traceability is obtained from effective efficiency measurement of the standard sensor using the microcalorimeter system.
RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Bolometer type sensors
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RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Thermistor is a temperature sensitive resistor.
Before the microwave power measurement, thermistor sensor is connected
to Wheatstone bridge then DC power applied on it.
PDC1 is related to V1 and R1
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RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
When the microwave power is applied to thermistor sensor,
RF
SUB
P
P
PDC2 is related to V2 and R1
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RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
V1: Wheatstone voltage (V), RF off
V2: Wheatstone voltage (V), RF on
e1: Thermopile output voltage (V), RF off
e2: Thermopile output voltage (V), RF on
LT: Thermopile linearity
T
T
R
Le
Lee
VV
V
1
122
22
1
211
1
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RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
dBR A115.01
AdB: Thin line attenuation (dB)
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21,VVTLee ,, 21
R
dBA
RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
21 CF
: Reflection coefficient of the thermistor
sensor
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RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Type : TwinPower Range : 1 mW to 10 mWConnector : Precision N Type
Sensor Type : ThermistorOperating freq. : 100 kHz to 18 GHz
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RF Power traceability
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS16
• RF power
• RF power traceability
• Diode sensor
• Skin effect
• Connectors
Contents
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS17
Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Characteristic of diode
100 -VeII
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
......8
1
2
11 3
3
0
22
0000
0 tCosV
VtCos
V
VtCos
V
VIeII mmmV
-
In this equation:I : Diode currentI0 : Leakage currentV0 : Thermal voltage
k : Boltzmann constantT : Temperature (K)e : Electron charge
tConsTk
V tan.
0 e
example: R&S NRV-Z4 power sensor
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
.......2cos25.0cos25.0
2
0
0
0
0
2
0
0
t
V
VIt
V
VI
V
VII mmm
ACDC III
DC current :2
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025.0mDC V
V
II
diode sensor – rather a voltage detector than a power detector
very sensitive to impedance mismatch
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
2
mDC VI
2
mm VP DCm2
mDC
2
mmIP
VI
VP
The DC component of current is proportional with the square of the applied voltage magnitude
Since microwave power, Pm, is proportional with the square of voltage, it is also proportional with the DC current.
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
Characteristic output of diode sensor
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
The generated voltage is rectified by the diode and while the AC component flows to ground, the DC component is resulted on ampermeter.
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
typical power measurement method: the power is measured through amplified low-frequency AC or DC voltage
source: http://www.keysight.com/find/backtobasics
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
measurement errors due to harmonics
- dependent on the crest factor (peak / average ratio), major errors can occur outside the square-law region
- improvement by use a full-wave rectifier instead of a half-way rectifier (elimination of even harmonics, i.e. 2nd, 4th, ...)
- phase between the harmonics is important
waveform distortion due to the2nd order harmonic
Voltage and Power Measurements,R&S application note, 1999
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
measurement errors due to harmonicsVoltage and Power Measurements,R&S application note, 1999
2nd harmonic 3rd harmonic
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Diode sensor
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
increase of dynamic range
(90 dB, three different power paths)e.g. R&S NRP-Z23 three-path diodepower sensors
automatic path switching in power transition regions
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• RF power
• RF power traceability
• Diode sensor
• Skin effect
• Connectors
Contents
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS28
Skin effect
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
: Conductivity of the metal
: Permeability of the metal
f : Frequencyf...
1
Effect of skin depth
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Skin effect
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
: Conductivity of the metal
: Permeability of the metal
f : Frequencyf...
1
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• RF power
• RF power traceability
• Diode sensor
• Skin effect
• Connectors
Contents
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS31
Connectors
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
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Frequency Range
Transmission Line Connector Type
DC-2 (?) GHz Coaxial, Microstrip lines BNC
DC-18GHz Coaxial, Waveguide, Microstrip lines 7 mm, Type N
DC-26.5 GHz Coaxial, Waveguide, Microstrip lines SMA, 3.5 mm
DC-40 GHz Coaxial, Waveguide, Microstrip lines 2.92 mm
DC-50 GHz Coaxial, Waveguide, Microstrip lines 2.4 mm
Transmission lines and connectors according to the frequency range
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Connectors
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS33
Connectors
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
•Coaxial transmission lines, consist of the nested two conductors.
•In order to keep constant the distance between conductors, an
insulating material is used with certain intervals or continuously.
•The inner conductor is usually a single wire, the outer conductor is
woven.
•Coaxial transmission lines, carry the signal as the electromagnetic
wave. There is no radiation loss at the coaxial lines.
•
•But there are copper losses in both coaxial and two wire lines. The
copper losses are related to the square of the current which is flowing
in the conductor and the resistance of the conductor( I2 R ) and are
expressed in Watt unit.
•Even if the conductor is produced with any metal different from
copper, the loss is called copper loss.
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Connectors
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS
1. Doug Skinner , “Guidance on using Precision Coaxial Connectors in Measurement”, Version 3, National Physics Laboratory. 2007.
2. IEEE 287 standard.3. Guidance on Selecting and Handling Coaxial RF Connectors used with Rohde &
Schwarz Test Equipment, Rohde & Schwarz, 20124. Connector care for RF & microwave coaxial connectors, HP, 1991.
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Thank you for attention
EMPIR 15RPT01 workshop, 7. 11. 2016, METAS36
EMPIR project “15RPT01 Development of RF and microwave metrology capability”http://rfmw.cmi.cz/