Topic 3 - RF Power Measurement, Keysight

Power
Measurement
Basics
Speaker Name
Keysight Technologies
January 2017
Objectives
On completion of this module, you will be able to:
• Understand the importance of power measurements
• Define the three basic types of power measurements
• Describe the power meter/sensor measurement method
• Explain the two most prevalent sensor technologies
• Describe advanced measurements used for the latest RF &

microwave applications
• Calculate power measurement uncertainty
• Outline Keysight’s broad range of power measurement solutions
Power Measurement Basics Page 2

Agenda
• Importance of Power Measurements
• Average, Peak and Pulse Power
• Power Meter & Sensor Measurement Method
• Sensor Technologies
• Keysight Power Measurement Solutions
• Advanced Power Measurements
• Measurement Uncertainty, Standards and Traceability
• Keysight Power Sensor Selection Guides (Appendix)

Signal Power Levels are Critical
Too low:
Signal buried in
noise
Too high:
Nonlinear
distortion...
...Or even
worse!

Importance of Power Measurements
• Critical to specified performance at every level of a system
• Many measurements made in design and manufacturing
• Measuring equipment and techniques must be:
• Accurate
• Repeatable
• Traceable
• Convenient

Why Not Measure Voltage?
DC Low Frequency
+ ZS ZS
V
± R
L P = IV = V2/R R
L
V
–
I I
High Frequency
Z
S
R • I and V vary with position
L AC component of
Z
O • Power is constant power
DC component of
P power
V Inc
Amplitude
V Ref
t
I
V

Agenda

Units and Definitions
• Power = energy transferred per unit time
• Basic power unit is the watt (W)
• 1W=1A x 1V
• A logarithmic (decibel) scale is often used to compare two power levels
• Relative power in decibels (dB):

 P 
P (dB)  10 log 
P 
 ref 
• Absolute power is expressed by assigning a reference level to Pref in dBm:
 P 
P (dBm )  10 log 
 1mW 

Average Power
AM
Average over many modulation cycles
Pulsed
t
Average over many pulse repetitions

Pulse Power
Pulse Power = Average Power/Duty Cycle
Power
• Rectangular pulse
• Constant duty cycle
A (pulse width) A
Duty Cycle =
B
B
(pulse repetition
interval)
Time

Envelope Power and Peak Envelope Power
Instantaneous Power
Peak Envelope Envelope Power
Power
“Peak Power”

Summary: Types of Power Measurements
EPM power meter
• Average Power
Average
power
EPM power meter

• Pulse Power
Pulse power
Average
power
EPM-P or P-Series
• Peak Envelope Power

Agenda


Instruments That Measure RF & Microwave Power
Power Meter and Sensor
• ± 0. 0X dB
• Broadband
• > – 70 dBm • ± 0. X dB or greater
• Frequency selective
Vector Signal Analyzer

The Power Meter and Sensor Method
Power Meter
Power Sensor
Thermistor Display
Thermocouple
(dBm or W)
RF power Diode Detector DC or low-frequency
equivalent

Agenda


Thermistors
• One of the earliest types of power sensors
• Have been replaced in most applications by thermocouples and diode

detectors
• Still used for power transfer standards in metrology applications

Thermocouples
• A junction of two dissimilar metals generates a voltage
related to temperature
RF
• Junction temperature is directly related to RF power Power
Cc
Cold
Junction
Hot
Hot
RF Junction
Input
Cold
Thin-Film
To DC
Thermocouples C
b Voltmeter

Diode Detectors
+
Rs
Vs C Vo
Rmatching b
-
• Diode detector does not measure the heat content of a signal but rectifies the
signal
• The matching resistor (approximately 50 ohms) is the termination for the RF
signal
• The RF signal voltage (Vs) is converted to a DC voltage (Vo) at the diode
• The bypass capacitor (Cb) is a lowpass filter that removes any RF signal
getting through the diode.

Square-Law Region of Diode Sensors
Linear Region
V O = nV2 = Pn IN
S
Square-Law Region
V O(log)
Noise Floor
50 dB
0.1 nW P 0.01 mW
– 70 dBm IN – 20 dBm

Multiple Path Diode Architecture
Low-Power Path
(– 60 to –10 dBm)
To -9dBm
RF Input
RF Input
To +2dBm
To +14dBm
High-Power Path To +26dBm

(–10 to +20 dBm)
2-path / 80 dB dynamic range with any 4-path / 96 dB dynamic range with

signal type (U2000/E9300) any signal type (U2040)
• Multiple-path design – always operate under diode square law region

• Diode/attenuator/diode topology
• Automatic path switching – best diode for the signal is automatically selected
and square-law maintained throughout sensor’s dynamic range

Power Sensor and Meter Signal Path
Power Sensor Power Meter
Synchronous
Diode BPF Ranging Detector LPF ADC
Detector Chopper
RF DC AC
AUTOZERO
220 Hz Squarewave µProcessor

Generator
DAC

U2040 X-Series Power Sensors – Signal
Path
USB Power Sensor
4 parallel paths for extended dynamic range
Zero/Cal Synchronous
Path Load Detector Range Measurement
Diode Switching filter* ADC (De-chop) Selection V2P Processing
Detector 100kHz,
Chopper
RF DC Internal
zero/cal 300kHz
2MHz, Display
5MHz
CAL DAC
Voltage Ref • Freq
• Temp
500Hz- • Offset
50kHz Trigger • Zero/cal
Squarewave
Generator
12.34 dBm
* Bandwidth is selectable dependent on mode

Power Sensor Comparisons
Power Sensor Advantages Disadvantages
Thermistor Directly traceable to Slow, low sensitivity

NPL/NIST*, good
match
Thermocouple Rugged, stable, Slow, low sensitivity
reliable
Diode Detector Fast, sensitive, enable Easily overloaded

peak & pulse
parameters
measurements
* Each thermistor mount contains data showing the calibration factor and effective efficiency at six frequencies, directly
traceable to the NPL/NIST at those frequencies where NPL/NIST provides calibration service.

Power Range of Various Sensor Types
Thermistors
Thermocouple Extended range

square-law region using an attenuator
Diode detector
square-law region
Wide Dynamic Range using Diode Detector

for CW only Signals
Extended range
Wide Dynamic Range using Diode
using an
Detector for Modulated Signals attenuator
-70 -60 -50 -40 -30 -20 -10 0 +10 +20 +30 +40 +50 [dBm]

Pulse Power Measurement Comparison
between CW and Average Sensors
Pulse Power Measurement Comparison

10
CW only power sensor

5
Thermocouple power
Error (dB)
0
sensor
-69-65-61-57-53-49-45-41-37-33-29-25-21-17-13 -9 -5 -1 3 7 Two path diode stack
sensor
-5
4-path diode stack sensor
-10
Pulse width 50us, pulse

-15 period 1ms
Average power input to the sensor (dBm)
• CW only sensor resulted in high error for pulse signal measurement above -20dBm
• Thermocouple power sensor offers the highest accuracy down to ~-35dBm
• Two path diode stack sensor provides good accuracy down to ~-60dBm
• 4-path diode stack sensor provides good accuracy down to ~-70dBm

Agenda


Keysight Power Meter Series
Power meters and sensors for RF and microwave measurement
World market leader* with over 60 years of experience in power meter design, offering
a complete measurement solutions from 9 kHz to 110 GHz, -70 dBm to +44 dBm.
NEW! 8990B Peak Power

Option up NEW! Analyzer
to 50 GHz
PERFORMANCE
• Peak, Average,
CCDF (<160MHz VBW)
• Pulse Measurement
• Radar Pulse Tr < 5ns
U2040 X-Series
• World’s widest dynamic range U2020 X-Series
• Peak & Average • Peak & Average,
• >50,000 readings/sec CCDF (<=30MHz) N1911/12A P-Series N8262A P-Series LXI
• USB or LAN • Peak, Average, CCDF • Peak, Average, CCDF
(<=30MHz VBW) • (<30MHz VBW)
• Wireless Networking • Compact, modular, faceless
(WLAN, WiMAX, MIMO) • For A&D ATE/ CASS
• Radar Pulse Tr > 13ns
E4416/17A EPM-P
U2000 Series • Peak & Average (<5MHz
USB Sensors VBW)
• Average Power N1913/14A EPM • Wireless Com (GSM, EDGE,
• Low Cost Solution • Average Power WCDMA, Bluetooth, etc.)
• I&M market, R&D • R&D & Mfg (Std • Radar Pulse Tr > 200ns
& Mfg Rack Size)
• Military & ATE
Handheld Systems
Power Meter
• Average Power PRICE
• Handheld solutions

Average Power Measurements
METROLOGY MULTI-CHANNEL WIDE DYNAMIC RANGE HIGH ACCURACY LOWEST COST
N432A N1913/14A U2040 X-Series U2000 Series U8480 Series V3500A

Thermistor Mount EPM Power Meter USB Wide USB Power USB Thermocouple Handheld Power
Power Meter Dynamic Range Sensor Power Sensor Meter
Power Sensor
NEW
U2041/43XA
• High accuracy of • Single, dual, or four • 10 MHz to 18 GHz • 9 kHz to 26.5 GHz • DC to 70 GHz • 10 MHz – 6 GHz
≤ 0.2% ± 0.5 uW channel measurements
• World’s widest dynamic • Wide dynamic range of - • Dynamic range of • Wide dynamic range of
• Excellent for 1mW • Wide freq/power range range of -70 dBm to 60 dBm to +20 sdBm -35 dBm to +20 dBm -63 dBm to +20 dBm
transfer calibration (with of 9 kHz to 110 GHz, +26 dBm
• Quick and easy setup • High accuracy of <0.1dB • Absolute accuracy to
478A-H75/76 thermistor -70 dBm to +44 dBm
• Fast measurement with USB connectivity (~2.3%) with +/-0.21 dB
mount sensor) (sensor dependent)
speed to 50,000 thermocouple sensor
• Internal zeroing without • Built-in display &
• Built-in 6.5 digit ADC • Fast measurement readings/sec
disconnecting from DUT • Built-in trigger input port integrated power sensor
eliminates the needs of speed of 400 readings/s
• Internal zero and and calibration source
external DMM • Bundled with N1918A • Internal power reference
• Code compatible with calibration
Power Panel software enables self calibration
• Digital color LCD legacy E4418/19B,
• Bundled with BenchVue for easy monitoring
display, user friendly 436A, 437B, and 438A
software for easy
interface. power meters (Opt 200)
monitoring
From $9,687 From $4,551 From $3,623 From $3,031 From $2,939 $2,260
1. Calibration 1. Manufacturing 1. Manufacturing 1. Manufacturing 1. Instrument / test system 1. Installation &
2. Metrology 2. System integration 2. Installation & 2. Installation & calibration maintenance
maintenance maintenance 2. Metrology & research 2. Field service / repair
3. Field service 3. Field service applications
Peak & Average Power Measurements
WIDE WIDE
HIGH
COMPACT WIDEBAND DYNAMIC WIDEBAND DYNAMIC
PERFORMANCE
RANGE RANGE
8990B N8262A N1911/12A E4416/17A U2020 U2040

Peak Power P-Series Modular P-Series power EPM-P Power X-Series USB Peak X-Series USB Peak
Analyzer Power Meter meter Meter & Average Power & Average Power
Sensor Sensor
NEW
U2042/44XA
• 5 ns rise time/ fall time • 1U half-rack size • 100 MSa/s • 20 MSa/s sampling rate • 100 MSa/s • 20 MSa/s
sampling rate sampling rate sampling rate
• 100 MSa/s • 100 MSa/s sampling • ~ 13 ns rise / fall time
sampling rate rate • ~ 13 ns rise/ fall time • ~13 ns rise/ fall time • ~100 ns rise/ fall time
• 5 MHz VBW
• 160 MHz VBW • ~ 13 ns rise time/ fall • 30 MHz VBW • 30 MHz VBW • Wideband average
time power, peak power
• 2 RF channels+ 2 • -35 dBm to +20dBm • 3500 readings/s
VBW 5 MHz
analog channels • 30 MHz VBW
• Internal Zero + • -35 dBm to +20dBm
• 50 000 readings/s
• Internal Zero + • Internal Zero + Calibration
• Internal Zero +
Calibration Calibration • -70 to +26dBm
Calibration
• LXI Class C • Internal Zero / Cal
Price: $32,416 Price: $13,419 Price from $8,308 Price from $5,265 Price from $7,486 Price from $5,175
1. R&D 1. System Integration 1. Manufacturing 1. Manufacturing 1. Manufacturing 1. Manufacturing
2. Design verification 2. System Integration 2. System Integration 2. Installation & 2. Installation &
maintenance maintenance
Power Measurement Basics Page 30 3. System integration 3. System integration

U2040 X-Series Wide Dynamic Range Power Sensors
The ideal sensor for any wireless signal formats
LTE-Advanced WLAN 802.11ac
LTE-TDD/FDD WLAN 802.11a/b/g/n
WCDMA WiMAX
• 10 MHz to 6/18 GHz

• World widest dynamic range:
GSM/EDGE -70 dBm to +26 dBm Bluetooth
• Broadband coverage
• Super fast speed
• Real time measurements
MCPA • Internal zero/calibration APCO/iDEN
• 100 ns rise time / 20 MSa/s
Model Freq range Power range Connector
U2041XA 10 MHz to 6 GHz (Average only)

U2042XA 10 MHz to 6 GHz (Peak & Average)
-70 dBm to +26 dBm N-type (male)
U2043XA 10 MHz to 18 GHz
Power (Average
Measurement only)Page 31
Basics
U2044XA 10 MHz to 18 GHz (Peak & Average)
World Widest Dynamic Range Power Sensor
1% error
1ms down
aperture -to -50dBm(X.01.34.04),
MY54520007 at avg count ofSpeed,
NORMAL 1 (@Freq
200ms aperture
1GHz, Read?, setting)
AvgCount 1 & Meas Speed 4.2ms/rdg
2% error
50msdown
apertureto -50dBm (X.01.34.04),
- MY54520007 at avg count of Speed,
NORMAL 1 (@ Freq
50ms aperture
1GHz, Read?, AC1setting)
& Meas Speed 53ms/rdg
0.5
0.4
0.3
1ms aperture (4ms/rdg)
0.2
0.1
Error (dB)
±0.08dB
0
-0.1
-0.2 50ms aperture (53ms/rdg)

-0.3
Measurement is very fast,
-0.4
accurate and repeatable.
-0.5
-60 -50 -40 -30 -20 -10 0 10 20 30
Input power to Sensor (dBm)
Measurement repeatability at 50ms (default aperture) and 1ms, average count of 1

(10 data collected at each power level)

U2049XA TVAC PoE/LAN Power Sensor
The ideal sensor for remote monitoring, fault detection, and

in-space performance monitoring of satellite systems
 Wide frequency coverage: 10 MHz to 33 GHz
 Widest dynamic range: -70 dBm to +20 dBm
 Patented internal zero/calibration
 TVAC test for operation in vacuum
 PoE/LAN connectivity for long distance remote monitoring
 Best-in-class long term drift performance

U2020 X-Series USB Power Sensors
USB power sensors with peak and
Internal zeroing and calibration
average power measurement capability of
eliminates external calibration needs
a bench power meter
Wideband peak & average

USB power sensor
 Wide 30MHz single shot
bandwidth
Works with any PC  100 MSa/s cont. sampling
30MHz VBW, and many Keysight
80MSa/s, 25000 instruments  50MHz – 18/ 40GHz
rdg/s, wide 50dB  -35 to +20dBm
peak dynamic range
 13ns rise time spec
Built-in external trigger in and
USB allows remote trigger out / video out / recording  Internal zero and
measurements beyond out ports calibration
typical cable length
 Built-in trigger in/out
Model Freq range Power range Connector

U2021XA 50M – 18GHz, -35 to +20dBm N-type (male)
U2022XA 50M – 40GHz -35 to +20dBm 2.4mm (male)

Internal Zero and Cal
P-Series & U2040/U2020 Series Power Sensors
Internal zero and calibration within the N192XA & U2020/U2040 Series
sensors - eliminates multiple connections with external calibration source
From CAL
DAC
Voltage
Reference
Zero and Cal To wideband

RF Input amplifier and
Path Switching
100 MHz Sampler
Diode Detectors
Wideband Power Sensor Block Diagram

USB Power Sensor Compatibility with Keysight Instruments
Perform source Perform scalar network
power analysis of frequency
calibration converter
ENA Vector
Network Analyzer
FieldFox Handheld
PNA series Vector Analyzer
Network Analyzer
Handheld Cable
and Antenna Tester
E/MXG Signal Generator
Perform user Turn the unit into a

flatness correction. power meter.
Supports two USB Handheld Spectrum Display power
X-series Signal Analyzer Analyzer measurement with
power sensors
measurement. RF Spectrum its user interface.
Analyzer
Each compatible instrument comes with built-in firmware to support the USB power sensor, unless specified that
N1918A Power Analysis Manager, BenchVue Power Meter App software, or VBA wizard is required.
Compatibility Guide:
http://literature.cdn.keysight.com/litweb/pdf/5989-8743EN.pdf
Page 37
8990B Peak Power Analyzer
Offers fastest rise and fall time of 5ns in the peak power
measurement market (160 MHz VBW)
15 inch XGA
Standard Keysight
color display
Oscilloscope knobs
+ touch
layout – easy to get
screen
familiarize
Simple soft
key menu Interactive controls
with color coded
knobs for each
channel.
15 automatic
pulse
characteristics
measurements Easy waveform
storage with USB
storage device
1.05GHz absolute accuracy

source for calibration Two RF channels and two Analog
channels with color coded.

8990B Peak Power Analyzer
Key Features 5nsec (System Rise/ Fall Time)
160MHz VBW
 15” XGA Color Display + Touch Screen Dynamic Range: -35dBm to +20dBm
Sampling Rate: 100MSa/sec
 4 channels (Two RF and two Analog)
Eff sampling rate: 1GSa/sec
 Dual Screen Zoom Window
 15 Pulse Characterization Measurements
Sensor Model Freq range Power range Connector
 Automatic pulse delay measurement between channels
N1923A 50M – 18GHz, -35 to +20dBm N-type (male)
N1924A 50M – 40GHz -35 to +20dBm 2.4mm (male)
Power Amplifier/ TR Module Test Transponder Test
• Measure Pulse Time Delay measurement  Measure reply pulse delay measurement
• Power Gain Measurement  Measure peak power, rise/ fall time, pulse width
• Pulse Droop Measurements 8990B
Signal Generator
PPA
Triggering
pulse
Interrogation
Interrogation pulse
pulse Reply
Amplifier pulse
response RF
pulse Reply
pulse
Trigger
delay
Radar Application Reply pulse delay

N191X Power Meters and N192X Power Sensors
Keysight’s P-Series power meters and power sensors provide
wide bandwidth, fast, accurate and repeatable power
measurements for R&D and manufacturing
• 30 MHz video bandwidth, 13 ns rise/fall time

• Single-shot and real time capture at 100 M-samples per second
• Zero and calibrate while still connected to the DUT
• Peak, average and peak-to-average ratio power measurements
plus automatic time measurements
• 50MHz to 18GHz / 40GHz
MKR 1 MKR 2
Gated power Pulse parameters analysis

measurements

Agenda


Technology Drivers
• Aerospace and Defense (Radar)
• Digital Wireless Communications
GSM / EDGE cdma2000 LTE Advanced
• 2G/3G technology
• TDMA system
• Time-gated average power • 3G technology • 4G technology
• Peak-to-average ratio • OFDMA system

• Fast measurements
• 20MHz to 100MHz VBW
• CCDF

Peak Power Measurement System
Power Sensor
Video BW
RF IN
High-speed sampling
measurement path
(P-Series/PPA)
Detected envelope power
Key system characteristics:

High-frequency modulated • Sufficient video (modulation) bandwidth
signal power
• High-speed, continuous sampling
• High-speed, continuous sampling

Remote Power Measurements
With USB sensor With LAN/PoE sensor
U2049XA
U2001A
LAN/ PoE
switch
Long distance
connection via
fiber optic link
PoE switch

Power Added Efficiency Test (With 8990B)
One of the typical Power Amplifier measurements besides the gain, output
power, S-parameters, P1dB, IP3, etc
Power amplifier 8990B Peak Power Analyzer
RF in RF out
Drain Voltage (Vd)
DC power DC Current Clamp 4 channels

Drain Current (Id)
Measure RF, Voltage and Current in one box

Transponder Test in Radar System
8990B enables automatic pulse parameters, pulse
spacing and pulse delay measurements
Interrogation from
ground station
Reply from Transponder
On-board Transponder
P1 P3
[1030MHz]
Ground Interrogation
Pulse to
Station Transponder
Reply Delay
Double Pulse Spacing
F1 F2
Reply Pulse from

Transponder
[1090MHz] Reply Pulse Spacing

Advance Radar Pulse Measurements
Pulse width Triggering
Inter Channel Pulse Spacing/

delay
Multi-pulse analysis
Page
S-Parameter / Gamma Corrections
Gamma Correction
• To correct for mismatch between sensor and DUT
PG Pi
Source/ DUT sensor
Гsensor = 0.05 Гsource = 0.33

(SWR = 1.11) (SWR = 2)
Mismatch error = 2 x Гsensor x Гsource x 100% = 3.5% (0.15dB)
S-parameter Correction
• To correct for any devices connected between sensor and
DUT
• Examples: cable,Padapter,
G attenuator, power
cable splitter,
Pi etc
Attenuator sensor
Source / DUT
Plane 2 Plane 1
Keysight U8480, U2020 or U2040 offer S-parameter/gamma correction

capability for improved
Page accuracy
Real Time Measurement Uncertainty Display
Provide real time display of power measurement uncertainties without

going through manual mathematic calculations (U8480 series)

RF/MW Component Tests
With USB sensor based scalar network analysis

GPIB to USB connection
Signal source
Power Directional
Splitter coupler Transmitted, B
DUT
Reflected, A
Incident, R
Allows stimulus-response measurements such as

Gain, Insertion Loss, Frequency Response and Return Loss

Agenda


What is Measurement Uncertainty and Why Does it Matter?
• Dispersion of the values attributed to a

measured parameter
• A measured value is only complete if it

is accompanied by a statement of the
associated uncertainty
• The actual test equipment accuracy is

only as good as the measurement
uncertainty of last calibration

Advantage of Test Equipment’s Low Measurement Uncertainty
Large measurement uncertainty increases the risk that your instrument is operating out-of-spec,
risking measurement errors that impact the quality or performance of the your design. Lower
measurement uncertainty of your test equipment and knowledge of what it is can save you cost,
schedule time, and increase the reliability of your design
Tolerance margins in your measurements can be made tighter, reducing false pass/fail rate, thus
enabling more accurate design calculations and allowing you to have more confidence in your
measurements.

Measurement Uncertainty versus Measurement Accuracy
Two sides of the same coin
Engineer Metrologist
Responsible for the integrity of measurements

Sources of Power Measurement Uncertainty
• Sensor and Source Mismatch Errors
• Power Sensor Errors
• Power Meter Errors
Sensor
Meter
Mismatch

Sensor and Source Mismatch
Signal Source
Impedance  Z0
Power Sensor Power Meter

Ideal impedance =
Z0
VSWR

Calculation of Mismatch Uncertainty
Signal Source
(2 GHz, 0 dBm)
Power Sensor
E9301A Power Meter

VSWR = 1.13
VSWR = 2.0  = 0.06
SENSOR
 = 0.33 VSWR  1
SOURCE  = VSWR  1
Mismatch Uncertainty = ± 2 x  SOURCE

x 
SENSOR
x 100%
= ± 2 x 0.33 x 0. 06 x 100% = ± 3.96%

Power Sensor Uncertainties
Various sensor
losses
Pi Pgl DC
Element Power Meter
Pr
Power Sensor
Pgl
: b = he
Cal Factor K (he = Effective Efficiency)
Pi
• Printed on sensor label (8480 series)
• Stored in EEPROM (E-series and P-series)

Power Meter Instrumentation Uncertainties
Power Reference
Uncertainty
 0.6 %
Instrumentation Uncertainty
 0.5 %

What is an Acceptable Measurement Uncertainty?
• Which is the smaller error:  1.0 dB … or ± 20% ?
Answer:  20% !
( 1.0 dB is + 26%,  21%)
• Sensor and meter uncertainties are specified in

percentage (linear) and dB (log)
• Marketing Manager’s Law of Small Numbers:
“A small-numbered uncertainty specification sounds

better than a large-numbered one.”

Calculating Power Measurement Uncertainty
1. Identify significant uncertainties
• Mismatch uncertainty: ± 3.96%
• Power linearity: ± 2.0% 1
• Cal factor uncertainty: ± 1.8% 1
• Power reference uncertainty: ± 0.6% 1
• Instrumentation uncertainty: ± 0.5%
1Specifications apply for an E9301A sensor and Keysight power meter over a temperature range
of 25 ±10 degrees C.
2. Combine uncertainties
• Worst-case or Root Sum of the Squares (RSS) method

Worst-Case Uncertainty
• Worst-case situation is assumed
• All sources of error at their extreme values
• Errors add constructively
• In our example measurement:

3.96% + 2.0% + 1.8% + 0.6% + 0.5% = ± 8.86%
Or, in log terms:
+ 8.86% = 10 log (1 + 0.089) = + 0.37 dB
– 8.86% = 10 log (1 - 0.089) = – 0.40 dB
• Extremely conservative

RSS (Root Sum of the Squares) Uncertainty*
Standard
Source of Probability
Value (± %) Divisor Uncertainty Ui
Uncertainty Distribution
(k=1)
Source/Sensor
Mismatch at 2 3.96 U-shaped 1.414 2.8
GHz
Calibration Factor
Uncertainty at 2 2.0 Normal 2 1.0
GHz
Linearity at 0 dBm 1.8 Normal 2 0.9
Power Reference
0.6 Normal 2 0.3
Uncertainty
Instrumentation
0.5 Normal 2 0.25
Uncertainty
Combined Standard Uncertainty = uc = RSS of ui
* In accordance to guidelines published in the ISO Guide to the Expression of Uncertainty in Measurement and
ANSI/NCSL Z540-2-1996, US Guide to the Expression of Uncertainty in Measurement.

Combined Standard Uncertainty (Uc)
• In our example:
uc = (2.8)2 + (1.0) 2 + (0.9) 2+ (0.3) 2+ (0.25)2
=  3.13%
• Expanded uncertainty (k = 2)
= k x uc =  6.26%
Worst-case
= 10 log (1 + 0.063) = + 0.27 dB + 0.37 dB
10 log (1  0.063) = – 0.28 dB – 0.37 dB
• Keysight AN 1449-3 covers uncertainty calculations

Keysight Power Measurements Uncertainty Calculators
P-Series Power Meter’s Uncertainty Calculator
EPM power meter’s Uncertainty Calculator
EPM-P/E9320 Uncertainty Calculator
U2000/U8480 USB Sensor Uncertainty Calculator
U2020 USB Sensor Uncertainty Calculator
8990B PPA Uncertainty Calculator
N432A Thermistor Power Meter Uncertainty Calculator
Download:
http://www.keysight.com/main/facet.jspx?&cc=US&lc=eng&k=uncertainty+calculator&sm=g

Standards Lab Calibration
Small measurement uncertainty. Greatest Confidence.
A Keysight Standards Lab Calibration is an
exacting process that focuses on the crucial
parameters you specify. We can perform these
calibrations on more than 500 instruments and
devices, and we will compare yours to either a
primary standard or a reference that has been
directly calibrated by a national metrology
institute (NMI).
– Depend on accurate measurements based on very low
measurement uncertainties
– Count on fast & predictable turnaround time
– Reduce your calibration costs
– Get documented compliance with ANSI/NCSL Z540.3-

2006 and ISO/IEC 17025:2005
www.keysight.com/find/StandardsLab

Choose the standard of test equipment calibration
suitable for your measurement needs

Power Sensor Calibration Traceability
Example
Calibration Cal factor TAT

Standard or measurement (days)
System uncertainty:
NIST/NMI primary
standard - X
NIST/NMI CN mount
- X
NIST/NMI thermistor cal 0.57% @ 8 GHz 8 – 12 weeks
(such as 8487B) (see curve) weeks
Roseville Standards Lab 0.67% @ 8 GHz 15 days

(8487A-H84)
Roseville Keysight cal + 0.98% @ 8 GHz 7 days

uncertainty (8487A)
http://www.nist.gov/calibrations/rf-microwave.cfm#611

National Standards and Traceability
Offers increased confidence in your power measurements and enhances audit success rate
Property of the result of a measurement

or the value of a standard whereby it can
be related to the international system of
units (SI units) via national metrology
institutes, through an unbroken chain of
comparisons all with stated uncertainties.
Source: International Vocabulary of Basic and General
Terms in Metrology (VIM)

Calibration should not be treated as a commodity
Why accredited calibration matters
Accreditation is a formal audit by a representative of an Accreditation Body to assess
conformance of a cal lab to internationally accepted standards (ISO/IEC 17025: 2005) and
ensures traceability back to SI units through the national metrology institutes
Calibration Laboratory Keysight Roseville Cal Lab ABC
A2LA Certification Number 1920.01 1395.09
I. Electrical – DC/Low
Frequency
DC Voltage  
DC Current  
Resistance  
AC Current  
AC Voltage 
AC Voltage Flatness 
Resistance 
Capacitance 
II. Electrical – RF / Microwave
Frequency Modulation  Cal Lab
Digital Modulation 
RF Absolute Power 
ABC is
Tuned RF Power  NOT
Power Sensor Calibration Factor 
Thermal Noise Figure System 
accredited
Pulse  for these
CISPR Pulse Response 
Attenuation 
Reflection S11 / S22 
All Keysight calibrations are performed by a lab with the scope-of-accreditation for the relevant
parameters

Summary
• Accurate power measurements (made with a power meter/sensor
combination) are crucial in RF and microwave applications.
• The three fundamental power measurements are average, peak and pulse.
• Modern wireless and radar technologies require time-gated and advanced

measurements.
• Keysight provides solutions for basic and advanced measurements.
• Measurement uncertainty is often calculated using the RSS method.
• The accuracy of Keysight power sensors is traceable to national

standards.

For More Information
Keysight Website
• URL: http://www.keysight.com/find/powermeters
Keysight Literature
• Application Note AN 1449–1, 2, 3 and 4, Fundamentals of RF and
Microwave Power Measurements (Parts 1, 2, 3 and 4).
• Product Note, Choosing the Right Power Meter and Sensor (Lit.
No. 5968-7150E).
• Application Note AN 64-4D, 4 steps for making better power
measurements (Lit. No. 5965-8167E)

Thank you!
2/14/2017
Page
Appendix: Power Measurement
Basics Page
Power Sensor Selection Guides

Average/CW Power Sensors
POWER All the following sensors are compatible with EPM, EPM-P and P-series power meters
N848x B-Series N8481B
N848x Average Thermocouple Sensor
-5 to +44 dBm N8482B
848x Average Diode Sensor
E930x B-Series E9300B
-30 to +44 dBm E9301B
848x Average Thermocouple Sensor
N8481H
E441x 1-Path Diode CW-only Sensor
N848x H-Series
-15 to +35 dBm N8482H E930x 2-Path Diode True-Average sensor
E9300H
E9301H
E930x A/H-Series
-50 to +30 dBm E9300A OPT –H25
E9304A OPT -H19
848x A-Series V8486A W8486A

-30 to + 20 dBm 8483A (75 ohm)
N8486AQ
N8486AR
N8488A
N848x A-Series N8487A
-35 to + 20 dBm N8485A OPT 33
N8481A
N8482A
E9300A OPT –H24
E930x Series E9301A
-60 to +20 dBm
E9304A OPT -H18
E441x Series E4413A OPT –H33
-70 to +20 dBm E4412A
8487D
Q8486D
848x D-Series R8486D
-70 to -20 dBm 8485D OPT 33
8481D
FREQUENCY
9 100 10 50 2 4.2 6 18 26.5 33 40 50 67 75 110
kHz kHz MHz MHz GHz GHz GHz GHz GHz GHz GHz GHz GHz GHz GHz
Peak & Average/CW & Wideband Power Sensors
POWER
N1923/24A Peak, Average, rise time,

fall time, pulse width sensor for PPA
N1921/22A Peak, Average, rise time, fall
time, pulse width sensor for P-Series
E932X Peak and Average sensor
N1924A (150MHz BW)

Compatible with 8990B PPA
N1923A (150MHz BW)
N192x A-Series
N1922A (30MHz BW)
-35 to + 20 dBm Compatible with P-series
N1922A (30MHz BW)
E9327A (5MHz BW)
E932x A-Series E9326A (1.5MHz BW)
-60 to +20 dBm E9323A (5MHz BW)

E9322A (1.5MHz BW) Compatible with EPM-P and P-Series power meters
E932x A-Series E9325A (300kHz BW)

-65 to +20 dBm E9321A (300kHz BW)
9 100 10 50 2 4.2 6 18 26.5 33 40 50 75 110

FREQUENCY
kHz kHz MHz MHz GHz GHz GHz GHz GHz GHz GHz GHz GHz GHz

U2040 X-Series USB Wide Dynamic Range Power Sensors
USB Power Sensors U2020 X-Series USB Peak & Average Power Sensors
U8480 Series USB Average Power Sensor (Thermocouple)

POWER
U2000 Series USB Average Power Sensors (Diode)
U2022XA
U2020 X-Series
-35 to +20 dBm U2021XA
USB Peak & Average Power Sensors
U2044Xa
U2040 X-Series
-70 to +26 dBm U2042XA
U2001B
U200xB Series
-30 to +44 dBm U200oB
U2002H
U200xH Series U2001H

-50 to +30 dBm
U2000H
USB Average Power Sensors
OPT-200 U8485A
U8480 Series
-35 to +20 dBm OPT-200 U8481A
E9304A
U2004A
OPT-
U2002A
H26
U200xA Series U2001A
-60 to +20 dBm
U2000A
U2043XA
U2040 X-Series
-70 to + 26 dBm U2041Xa
FREQUENCY
DC 9 10 50 2 4.2 6 18 24 26.5 33 40 50 75 110
kHz MHz MHz GHz GHz GHz GHz GHz GHz GHz GHz GHz GHz GHz
Any
Questions?

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Power

• Define the three basic types of power measurements

• Describe the power meter/sensor measurement method

• Explain the two most prevalent sensor technologies

• Describe advanced measurements used for the latest RF &

• Outline Keysight’s broad range of power measurement solutions

Power Measurement Basics Page 2

Power Measurement Basics Page 3

Power Measurement Basics Page 4

• Many measurements made in design and manufacturing

• Measuring equipment and techniques must be:

Power Measurement Basics Page 5

Power Measurement Basics Page 6

Power Measurement Basics Page 7

• A logarithmic (decibel) scale is often used to compare two power levels

• Relative power in decibels (dB):

Power Measurement Basics Page 8

Average over many modulation cycles

Power Measurement Basics Page 9

Power Measurement Basics Page 10

Power Measurement Basics Page 11

EPM power meter

Power Measurement Basics Page 12

• Importance of Power Measurements

Power Measurement Basics Page 13

Vector Signal Analyzer

Power Measurement Basics Page 14

Power Measurement Basics Page 15

• Importance of Power Measurements

Power Measurement Basics Page 16

• One of the earliest types of power sensors

• Have been replaced in most applications by thermocouples and diode

• Still used for power transfer standards in metrology applications

Power Measurement Basics Page 17

Power Measurement Basics Page 18

Power Measurement Basics Page 19

Power Measurement Basics Page 20

High-Power Path To +26dBm

2-path / 80 dB dynamic range with any 4-path / 96 dB dynamic range with

• Multiple-path design – always operate under diode square law region

Power Measurement Basics Page 21

220 Hz Squarewave µProcessor

Power Measurement Basics Page 22

* Bandwidth is selectable dependent on mode

Power Measurement Basics Page 23

Power Sensor Advantages Disadvantages

Thermistor Directly traceable to Slow, low sensitivity

Diode Detector Fast, sensitive, enable Easily overloaded

Power Measurement Basics Page 24

Thermocouple Extended range

Wide Dynamic Range using Diode Detector

Power Measurement Basics Page 25

Pulse Power Measurement Comparison

CW only power sensor

Pulse width 50us, pulse

Power Measurement Basics Page 26

• Importance of Power Measurements

Power Measurement Basics Page 27