SIST EN 61828:2002
(Main)Ultrasonics - Focusing transducers - Definitions and measurement methods for the transmitted fields
Ultrasonics - Focusing transducers - Definitions and measurement methods for the transmitted fields
Provides definitions for the transmitted field characteristics of focusing transducers for applications in medical ultrasound; relates these definitions to theoretical descriptions, design, and measurement of the transmitted fields of focusing transducers. Gives measurement methods for obtaining defined characteristics of focusing transducers. Specifies beam axis alignment methods appropriate for focusing transducers.
Ultraschall - Fokusierende Wandler - Definitionen und Messverfahren für die erzeugten Felder
Ultrasons - Transducteurs focaliseurs - Définitions et méthodes de mesure des champs transmis
La présente Norme internationale spécifie: - des définitions des caractéristiques du champ transmis de transducteurs focalisants pour des applications ultrasonores médicales; - la relation entre ces définitions et les descriptions théoriques, la conception et le mesurage des champs transmis par des transducteurs focalisants; - des méthodes de mesurage pour l'obtention de caractéristiques définies de transducteurs focalisants; - des méthodes d'alignement de l'axe du faisceau adaptées aux transducteurs focalisants. La présente Norme internationale se réfère à des transducteurs ultrasonores focalisants fonctionnant dans la plage de fréquences appropriée pour des applications ultrasonores médicales (soit de 0,5 MHz à 40 MHz) aussi bien thérapeutiques que diagnostiques. La présente norme montre comment les caractéristiques du champ transmis par les transducteurs peuvent être décrites du point de vue de la conception et mesurées par une personne n'ayant aucune connaissance préalable des détails de construction d'un appareil spécifique. Le champ ultrasonore émis pour une excitation spécifiée est mesuré par un hydrophone soit dans un milieu d'essai standard (par exemple de l'eau), soit dans un autre milieu donné. La Norme s'applique uniquement à des milieux où le comportement du champ est essentiellement similaire à celui constaté dans un fluide (c'est-à-dire où l'influence des ondes de cisaillement et de l'anisotropie élastique est faible), cela comprenant les tissus mous et les gels imitant un tissu. Tous les aspects du champ affectant leur description théorique ou qui sont importants pour la conception sont aussi inclus. Ces définitions peuvent être utiles dans des communications scientifiques, pour la conception d'appareils et pour la description du rendement et de la sécurité de systèmes utilisant ces dispositifs.
Ultrasonics - Focusing transducers - Definitions and measurement methods for the transmitted fields (IEC 61828:2001)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61828:2002
01-september-2002
Ultrasonics - Focusing transducers - Definitions and measurement methods for
the transmitted fields (IEC 61828:2001)
Ultrasonics - Focusing transducers - Definitions and measurement methods for the
transmitted fields
Ultraschall - Fokusierende Wandler - Definitionen und Messverfahren für die erzeugten
FelderUltrasons - Transducteurs focaliseurs - Définitions et méthodes de mesure des champs
transmisTa slovenski standard je istoveten z: EN 61828:2001
ICS:
11.040.55 'LDJQRVWLþQDRSUHPD Diagnostic equipment
17.140.50 Elektroakustika Electroacoustics
SIST EN 61828:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 61828:2002
EUROPEAN STANDARD EN 61828
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2001
ICS 17.140.50
English version
Ultrasonics -
Focusing transducers -
Definitions and measurement methods
for the transmitted fields
(IEC 61828:2001)
Ultrasons - Ultraschall -
Transducteurs focaliseurs - Fokusierende Wandler -
Définitions et méthodes de mesure Definitionen und Messverfahren
des champs transmis für die erzeugten Felder
(CEI 61828:2001) (IEC 61828:2001)
This European Standard was approved by CENELEC on 2001-09-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61828:2001 E---------------------- Page: 3 ----------------------
SIST EN 61828:2002
EN 61828:2001 - 2 -
Foreword
The text of document 87/196/FDIS, future edition 1 of IEC 61828, prepared by IEC TC 87, Ultrasonics,
was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61828 on
2001-09-01.The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2002-06-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-09-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A, B and C are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61828:2001 was approved by CENELEC as a European
Standard without any modification.In the official version, for Bibliography, the following notes have to be added for the standards
indicated:IEC 61161:1992 NOTE: Harmonized as EN 61161:1994 (not modified).
IEC 62092:2001 NOTE: Harmonized as EN 62092:2001 (not modified).
__________
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SIST EN 61828:2002
- 3 - EN 61828:2001
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates, by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references, the latest edition of the publication referred to applies (including
amendments).NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.Publication Year Title EN/HD Year
IEC 60050-801 1994 International Electrotechnical --
Vocabulary (IEV) -
Chapter 801: Acoustics and
electroacoustics
IEC 61102 1991 Measurement and characterisation of EN 61102 1993
ultrasonic fields using hydrophones in
the frequency range 0,5 MHz to 15 MHz
IEC 61157 1992 Requirements for the declaration of the EN 61157 1994
acoustic output of medical diagnostic
ultrasonic equipment
IEC 61689 1996 Ultrasonics - Physiotherapy systems - EN 61689 1996
Performance requirements and methods
of measurement in the frequency range
0,5 MHz to 5 MHz
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SIST EN 61828:2002
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SIST EN 61828:2002
NORME CEI
INTERNATIONALE
IEC
61828
INTERNATIONAL
Première édition
STANDARD
First edition
2001-05
Ultrasons – Transducteurs focalisants –
Définitions et méthodes de mesurage
pour les champs transmis
Ultrasonics – Focusing transducers –
Definitions and measurement methods
for the transmitted fields
IEC 2006 Droits de reproduction réservés Copyright - all rights reserved
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Pour prix, voir catalogue en vigueur
For price, see current catalogue
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61828 IEC:2006 – 3 –
CONTENTS
FOREWORD...........................................................................................................................7
INTRODUCTION...................................................................................................................11
1 Scope.............................................................................................................................13
2 Normative references .....................................................................................................13
3 General ..........................................................................................................................15
3.1 Focusing transducers ............................................................................................15
3.2 System and measurement requirements................................................................19
3.3 General focused field descriptions.........................................................................21
4 Focusing definitions........................................................................................................25
4.1 Background information.........................................................................................25
4.2 Definitions .............................................................................................................25
5 List of symbols ...............................................................................................................51
6 Measurement procedures ...............................................................................................53
6.1 General .................................................................................................................53
6.2 Finding the beam axis ...........................................................................................53
6.3 Determining if transducer is focusing.....................................................................57
6.4 Measuring other focal parameters of a focusing transducer ...................................59
Annex A (informative) Background for the transmission/ Characteristics of focusing
transducers ....................................................................................................................81
Annex B (informative) Methods for determining the beam axis for well-behavedbeams ............................................................................................................................91
Annex C (informative) Methods for determining the beam axis for beams that are not
well-behaved ..................................................................................................................99
Bibliography........................................................................................................................103
Figure 1 – Transducer options – Top: Transducer with a radius of curvature R and a focal
length equal to R – Middle: Transducer with a plano-concave lens – Bottom: Transducer
with a plano-convex lens.......................................................................................................63
Figure 2 – Definitions for focusing measurements when the transducer geometry isunknown ...............................................................................................................................65
Figure 3 – Field parameters for non-focusing and focusing transducers ................................67
Figure 4 – Beam contour plot – Contours at –6, –12, and –20 dB for a 5 MHz transducer
with a diameter of 25 mm and a radius of curvature of 50 mm centred at location 0,0
(bottom centre of graph) .......................................................................................................69
Figure 5 – Parameters for describing a focusing transducer of a known geometry.................71
Figure 6 – Path difference parameters for describing a focusing transducer of a known
geometry ..............................................................................................................................73
Figure 7 – Beamwidth focus in a principal longitudinal plane.................................................75
Figure 8 –Types of geometric focusing..................................................................................77
Figure 9 – Pressure focus in a principal longitudinal plane....................................................79
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61828 IEC:2006 – 5 –
Figure B.1 – X-axis scan at 9 cm depth for the first focal zone with beam centre ..................93
Figure B.2 – X-axis scan at 4,4 cm depth for the second focal zone......................................95
Figure C.1 – Asymmetric beam showing beamwidth midpoint method .................................101
Table B.1 – Standard deviations for x and y scans using three methods of determining
the centre of the beam ..........................................................................................................93
Table B.2 – –dB beamwidth levels for determining midpoints ...............................................97
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS – FOCUSING TRANSDUCERS –
DEFINITIONS AND MEASUREMENT METHODS
FOR THE TRANSMITTED FIELDS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61828 has been prepared by IEC technical committee 87:
Ultrasonics.This bilingual version (2006-07) replaces the English version.
The text of this standard is based on the following documents:
FDIS Report on voting
87/196/FDIS 87/204/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
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61828 IEC:2006 – 9 –
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;• withdrawn;
• replaced by a revised edition, or
• amended.
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61828 IEC:2006 – 11 –
INTRODUCTION
Focusing transducers are essential in medical applications for obtaining high-resolution
images, Doppler and flow data and for concentrating ultrasonic energy at desired sites for
therapy. Present terminology for focusing transducers is inadequate for communicating
precisely the characteristics of the focused fields of the wide variety of transducers and
transducer array types and focusing means in common usage.This International Standard provides specific definitions appropriate for describing the
focused field from a theoretical viewpoint for transducers with known characteristics intended
by design. Other specific definitions included in this standard, based on measurement
methods, provide a means of determining focusing properties, if any, of a transducer of
unknown field characteristics. The measurement method and definitions provide criteria for
determining if the transducer is focusing, as well as a means of describing the focusing
properties of the field. Beam axis alignment methods are given for focusing transducers.
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61828 IEC:2006 – 13 –
ULTRASONICS – FOCUSING TRANSDUCERS –
DEFINITIONS AND MEASUREMENT METHODS
FOR THE TRANSMITTED FIELDS
1 Scope
This International Standard
− provides definitions for the transmitted field characteristics of focusing transducers for
applications in medical ultrasound;− relates these definitions to theoretical descriptions, design, and measurement of the
transmitted fields of focusing transducers;− gives measurement methods for obtaining defined characteristics of focusing transducers;
− specifies beam axis alignment methods appropriate for focusing transducers.This International Standard relates to focusing ultrasonic transducers operating in the
frequency range appropriate to medical ultrasound (0,5 MHz to 40 MHz) for both therapeutic
and diagnostic applications. It shows how the characteristics of the transmitted field of
transducers may be described from the point of view of design, as well as measured by
someone with no prior knowledge of the construction details of a particular device. The
radiated ultrasound field for a specified excitation is measured by a hydrophone in either a
standard test medium (for example, water) or in a given medium. The standard applies only to
media where the field behaviour is essentially like that in a fluid (i.e. where the influence of
shear waves and elastic anisotropy is small), including soft tissues and tissue-mimicking gels.
Any aspects of the field that affect their theoretical description or are important in design are
also included. These definitions would have use in scientific communications, system design
and description of the performance and safety of systems using these devices.This standard incorporates definitions from other related standards where possible, and
supplies new, more specific terminology, both for defining focusing characteristics and for
providing a basis for measurement of these characteristics.2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.IEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) – Chapter 801:
Acoustics and electroacousticsIEC 61102:1991, Measurement and characterization of ultrasonic fields using hydrophones in
the frequency range 0,5 MHz to 15 MHz___________
Specifically, IEC 61102 and IEC 61157 (see clause 2).
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61828 IEC:2006 – 15 –
IEC 61157:1992, Requirements for the declaration of the acoustic output of medical
diagnostic ultrasonic equipmentIEC 61689:1996, Ultrasonics – Physiotherapy systems – Performance requirements and
methods of measurement in the frequency range 0,5 MHz to 5 MHz3 General
The information contained in this clause is an introduction to the definitions given in clause 4
and the measurement methods given in clause 6.3.1 Focusing transducers
The term "focusing transducer" is commonly used for a device which has a smaller
beamwidth in some regions of the field than a device which is "non-focusing". A "non-
focusing transducer" can still have a natural focus, so it is necessary to distinguish a
focusing transducer as having a greater concentration of pressure amplitude (for a given
power output) than a non-focusing transducer at its natural focus. For example, a non-
focusing transducer made of a simple disc of uniformly poled piezoelectric material has a
beam whose intensity at its natural focus can be as much as four times the average intensity
at the source, and whose –6 dB beamwidth can be approximately half of that at the source. A
definition of a focusing transducer is given in 4.2.33 to make a quantitative distinction
between focusing and non-focusing transducers.3.1.1 Focusing methods
The simplest means of intentionally focusing an ultrasonic transducer, borrowed from
analogous optical principles, is that of shaping the ultrasonic transducer into a concave form
or adding to it a physical lens as illustrated in figure 1. In the top part of this figure, a
transducer curved with a radius R is shown focusing to the centre of curvature, where R is
positive by convention. By the geometrical-optics approximation, the focal length F is equal to
R and hence is also positive. In the middle of figure 1 is shown a transducer with a plano-
concave lens made of a material with longitudinal velocity, c , which is curved on one side
with a radius, R , and radiates into a medium in which the velocity is c . In acoustics, c
LENS W Wis typically less than c , i.e., the index of refraction n (equal to c /c ) is less than 1. When
L W Lthis is true, the radius is considered to be negative and the focal length, given by the
geometric-acoustics approximation as R divided by (n – 1), is positive. At the bottom of
LENSthe figure, for comparison, the typical situation for a convex lens in optics is shown: n is
greater than 1 and the radius is considered to be positive, so the focal length is positive.
3.1.2 Known and unknown focusing transducersFor ultrasonic transducers currently used in medical ultrasound applications, it is difficult to
determine from physical observation if an ultrasonic transducer is focusing, because
additionally many other focusing methods such as geometric shaping and arrangement,
reflectors, arrays with electronic phasing and delay, Fresnel lenses, shading, etc. may be
used singly or in combination. Because of inherent natural focusing and the potential
complexity of additional focusing means used, any generally useful definition of a focusing
transducer must be in terms of its field rather than its construction. If a focusing source were
to be defined in terms of its pressure field, then this would be relatively easy to apply in
practice, since the pressure can be measured directly with a hydrophone.___________
Terms in bold print are defined in clause 4.
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A distinction is also made between ultrasonic transducers whose construction is known and
transducers about which very little information is available. For the first category of ultrasonic
transducers, certain theoretical definitions, such as geometric focal length, are useful for
describing and modelling focusing characteristics. Ultrasonic transducers falling in the
second category function as an unknown "black box" and only the field may be accessible.
In the latter case, and in general, focusing parameters are determined from measurements,
and the measurement procedures of clause 6 are appropriate. In clause 6, measurement
methods are given for determining if a transducer system radiating into known propagation
media under specified excitation conditions is "focusing". Because of the lack of knowledge of
ultrasonic transducer construction and limited access to the ultrasonic transducer field, the
focusing definitions shown in figure 2 are required. These definitions are given in clause 4
and their use is explained in 3.1.5.3.1.3 Focusing and beamwidth
Previously, hydrophone measurements of beam characteristics were based on regions of axial
peak pressure. For example, definitions for a depth-of-field were based on the fall-off in
intensity on either the near side or the far side of an axial peak on the beam axis. For axially
symmetric beams, this axial peak can be related to the geometric focal length. For typical
rectangular arrays, azimuthal plane electronic focusing and elevational plane mechanical lens
focusing can cause peaks of axial pressure at different locations along a beam axis. These
individual peaks can be dealt with separately by beamwidth measurements made in the
corresponding orthogonal planes: therefore, new definitions are based on beamwidths in a
specified longitudinal plane (refer to figure 7). Focusing definitions must also distinguish
between natural and intentional focusing.3.1.4 New focusing parameter definitions
This document introduces new focusing parameters and provides more specific contexts for
existing terminology. For example, the terms "near field" and "far field" are often misapplied
to focusing transducers, though they have traditionally been defined for non-focusing
transducers only. The definitions near Fresnel zone, far Fresnel zone and focalFraunhofer zone, apply to focusing transducers. These definitions, explained in more detail
in 3.3 and derived from annex A, are illustrated in figure 3b and are applied to a strongly
focusing circular aperture in figure 4. Other concepts such as focusing in a particular plane
are also necessary to reduce ambiguity in usage.For the purposes of this document, the following definitions for a focusing transducer will be
used.For ultrasonic transducers of known construction (refer to figure 5 for transducer geometry
and terms), a focusing transducer is an electro-acoustic device that produces, at any
distance less than one-half of the transition distance from the transducer aperture, a –6 dB
beamwidth in a longitudinal plane that is less than half the transducer aperture width in
that plane. For measurement purposes and cases (see figure 2) where the geometry of the
ultrasonic transducer is not known or where there is no direct access to the ultrasonic
transducer (because of the device being used in some stand-off arrangement), a definition of
focusing based on data is more appropriate. For this second case, a focusing transducer is
an electro-acoustic device that produces, at any distance less than half of the transition
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61828 IEC:2006 – 19 –
distance from the source aperture, a –6 dB beamwidth in a longitudinal plane that is less
than one-half the –20 dB source aperture width (measured in a plane as close as possible to
the ultrasonic transducer) in that plane. For arrays with a rectangular geometry, a specified
longitudinal plane is either an xz or yz plane with z along the beam axis. Non-focusing
transducers are those not meeting the conditions specified above.3.1.5 Applications of focusing definitions
Two definitions of focusing are given in 3.1.4, which apply in two cases.
a) For transducers for which the construction is known, an ideal definition is given for
describing, modeling or design purposes.b) A second definition applies to measurements of the focusing characteristics of real
transducers which either have an unknown construction or imperfect realization.Use of the first definition is not a substitute for actual measurement. Whether or not a
transducer is focusing in practice must be determined by the second definition for transducers
of unknown construction and by the measurement procedures of clause 6. Knowledge about
the transducer (first definition) may be helpful in guiding measurements. If measurements
meet the criteria of the second definition, the transducer is focusing, irrespective of whether
focusing was intentional or accidental.3.1.6 Relation of present definitions to physiotherapy transducers (treatment heads)
The definition of focusing in the present document is not related to the definitions of
“divergent, collimated and convergent” beams as described in IEC 61689. The definition of
beam type is based on energy and area considerations that are more important forphysiotherapy transducers. The definition of focusing in the present document is based on a
different parameter: –6 dB beamwidth. This definition is useful in identifying the existence and
location of the highest field concentrations. When the current document is applied to
physiotherapy transducers, focusing can be understood to correspond to high-beam non-
uniformity ratio “hot-spot” transducers.3.2 System and measurement requirements
In 3.1 it was shown that the radiating device has to be considered as a who
...
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