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Agilent
Fundamentals of RF and Microwave
Power Measurements (Part 1)
Introduction to Power, History, Definitions,
International Standards & Traceability
Application Note 1449-1
For user convenience, Agilent's Fundamentals of RF and Microwave Power
Fundamentals of RF and
Microwave Power Measurements,
Measurements (Part 1)
application note 64-1, literature Introduction to Power, History, Definitions, International
number 5965-6330E, has been Standards, and Traceability
updated and segmented into four AN 1449-1, literature number 5988-9213EN
technical subject groupings. The
following abstracts explain how the Part 1 introduces the historical basis for power measurements, and provides
total field of power measurement definitions for average, peak, and complex modulations. This application
fundamentals is now presented. note overviews various sensor technologies needed for the diversity of test
signals. It describes the hierarchy of international power traceability,
yielding comparison to national standards at worldwide national measure-
ment institutes (NMIs) like the U.S. National Institute of Standards and
Technology. Finally, the theory and practice of power sensor comparison
procedures are examined with regard to transferring calibration factors and
uncertainties. A glossary is included which serves all four parts.
Fundamentals of RF and Microwave Power
Measurements (Part 2)
Power Sensors and Instrumentation
AN 1449-1, literature number 5988-9214EN
Part 2 presents all the viable sensor technologies required to exploit the wide
range of unknown modulations and signals under test. It starts with explana-
tions of the sensor technologies, and how they came to be to meet certain
measurement needs. Sensor choices range from the venerable thermistor to
the innovative thermocouple to more recent improvements in diode sensors.
In particular, clever variations of diode combinations are presented, which
achieve ultra-wide dynamic range and square-law detection for complex
modulations. New instrumentation technologies, which are underpinned with
powerful computational processors, achieve new data performance.
Fundamentals of RF and Microwave Power
Measurements (Part 3)
Power Measurement Uncertainty per International Guides
AN 1449-1, literature number 5988-9215EN
Part 3 discusses the all-important theory and practice of expressing meas-
urement uncertainty, mismatch considerations, signal flowgraphs, ISO
17025, and examples of typical calculations. Considerable detail is shown on
the ISO 17025, Guide for the Expression of Measurement Uncertainties, has
become the international standard for determining operating specifications.
Agilent has transitioned from ANSI/NCSL Z540-1-1994 to ISO 17025.
Fundamentals of RF and Microwave Power
Measurements (Part 4)
An Overview of Agilent Instrumentation for RF/Microwave
Power Measurements
AN 1449-1, literature number 5988-9216EN
Part 4 overviews various instrumentation for measuring RF and microwave
power, including spectrum analyzers, microwave receivers, network/spec-
trum analyzers, and the most accurate method, power sensors/meters. It
begins with the unknown signal, of arbitrary modulation format, and draws
application-oriented comparisons for selection of the best instrumentation
technology and products.
Most of the chapter is devoted to the most accurate method, power meters
and sensors. It includes comprehensive selection guides,frequency coverages,
contrasting accuracy and dynamic performance to pulsed and complex
digital modulations. These are especially crucial now with the advances in
wireless communications formats and their statistical measurement needs.
2
Table of Contents I. Introduction ......................................................................................... 4
The importance of power .......................................................................... 5
A brief history of power measurements ................................................. 6
A history of peak power measurements ................................................. 7
II. Power Measurement Fundamentals................................ 9
Understanding the characteristics of the signal under test ................ 9
Units and definitions.................................................................................. 11
IEEE video pulse standards adapted for microwave pulses ............... 15
Peak power waveform definitions............................................................ 16
A typical wireless modulation format ..................................................... 17
Three technologies for sensing power .................................................... 17
An overview of power sensors and meters for pulsed and complex
modulations ............................................................................................ 18
Key power sensor parameters .................................................................. 18
Data computation for statistical parameters of power analysis ......... 20
III. The Chain of Power Traceability ......................................... 21
The hierarchy of power measurement, national standards and
traceability .............................................................................................. 21
The theory and practice of sensor calibration....................................... 23
Some measurement considerations for power sensor comparisons .. 24
Typical sensor comparison system .......................................................... 24
Thermistors as power transfer standards .............................................. 26
Other DC substitution meters................................................................... 26
Peak power sensor calibration traceability ............................................ 27
Network analyzer source system.............................................................. 28
NIST Six-port calibration system ............................................................. 28
IV. Glossary and List of Symbols ................................................ 30
3
The purpose of the new series of Fundamentals of RF and Microwave Power
I. Introduction Measurements application notes, which were leveraged from former note 64-1,
is to
1) Retain tutorial information about historical and fundamental
considerations of RF/microwave power measurements and technology
which tend to remain timeless.
2) Provide current information on new meter and sensor technology.
3) Present the latest modern power measurement techniques and test
equipment that represents the current state-of-the-art.
Part 1, Chapter 1 reviews the commercial and technical importance of making
power measurements, equity in trade, the cost of measurement uncertainties,
and the need for two power measurements of the same unit under test will be
the same at two locations in the world. It then presents a brief history of power
techniques, and additionally a history of peak power techniques.
Chapter 2 shows why it is crucial to begin a power measurement task with a
clear understanding of the characteristics of the signal under test. With the
advent of new complex combinations of modulations in the 1990s and forward,
it also presents signal format considerations that users must evaluate when
pondering which sensor technologies to use.
The application note then defines the variety of terminology of units and
definitions of various power measuring terms. It shows how IEEE video pulse
standards were adapted by Agilent for use in microwave pulsed power
envelopes. Brief descriptions of modern wireless formats show how key sensor
performance is required to faithfully capture the system power. Various sensor
technologies and instrumentation are previewed from the complete descrip-
tions in Fundamentals Part 2.
Considerations necessary for capturing and digitizing microwave signals which
are used in modern wireless systems are presented. These often consist of
pulsed carriers plus digital phase modulations, which look like noise, combined
on the same signal. When measured with digital sampling type instrumenta-
tion, the powerful micro-processors can run statistical routines to reveal
computed data, oriented to particular customer requirements.
Chapter 3 presents the matter of basic measurement traceability to national
and world standards. It describes the hierarchy of international traceability,
including comparison processes to national standards at worldwide NMIs such
as the U.S. National Institute of Standards and Technology, Boulder, CO.
The application note reviews the theory and practice of sensor calibration
processes and the need for transportable sensor artifacts which can transfer
higher-echelon uncertainties of the NMIs to company primary lab standards.
It reviews special procedures needed for extended calibration processes on
pulse-power sensors.
Note: In this application note numerous technical references will be made to
the other published parts of the Fundamentals of RF and Microwave Power
Measurements series. For brevity, we will use the format Fundamentals Part X.
This should insure that you can quickly locate the concept in the other
publication. Brief abstracts for the four-part series are provided on the inside
the front cover.
4
The importance of power
The output power level of a system or component is frequently the critical fac-
tor in the design, and ultimately the purchase and performance of almost all
radio frequency and microwave equipment. The first key factor is the concept
of equity in trade. When a customer purchases a product with specified power
performance for a negotiated price, the final production-line test results need
to agree with the customer's incoming inspection data. These shipping, receiv-
ing, installation or commissioning phases often occur at different locations,
and sometimes across national borders. The various measurements must be
consistent within acceptable uncertainties.
Secondly, measurement uncertainties cause ambiguities in the realizable per-
formance of a transmitter. For example, a 10-W transmitter costs more than a
5-W transmitter. Twice the power output means twice the geographical area is
covered or 40% more radial range for a communication system. Yet, if the over-
all measurement uncertainty of the final product test is on the order of