WO2020157039A3 - Vorrichtung zum verarbeiten eines signals eines ortungssystems sowie verfahren zum simulieren und zum orten eines objekts - Google Patents

Vorrichtung zum verarbeiten eines signals eines ortungssystems sowie verfahren zum simulieren und zum orten eines objekts Download PDF

Info

Publication number
WO2020157039A3
WO2020157039A3 PCT/EP2020/051997 EP2020051997W WO2020157039A3 WO 2020157039 A3 WO2020157039 A3 WO 2020157039A3 EP 2020051997 W EP2020051997 W EP 2020051997W WO 2020157039 A3 WO2020157039 A3 WO 2020157039A3
Authority
WO
WIPO (PCT)
Prior art keywords
signal
locating
processing unit
signal processing
simulating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2020/051997
Other languages
English (en)
French (fr)
Other versions
WO2020157039A2 (de
Inventor
Dominik Bok
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Publication of WO2020157039A2 publication Critical patent/WO2020157039A2/de
Publication of WO2020157039A3 publication Critical patent/WO2020157039A3/de
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/021Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06Systems determining position data of a target
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50Systems of measurement based on relative movement of target
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50Systems of measurement based on relative movement of target
    • G01S13/58Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G01S13/583Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
    • G01S13/584Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets adapted for simultaneous range and velocity measurements
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/66Radar-tracking systems; Analogous systems
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/82Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/86Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/35Details of non-pulse systems
    • G01S7/352Receivers
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40Means for monitoring or calibrating
    • G01S7/4052Means for monitoring or calibrating by simulation of echoes
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40Means for monitoring or calibrating
    • G01S7/4052Means for monitoring or calibrating by simulation of echoes
    • G01S7/4056Means for monitoring or calibrating by simulation of echoes specially adapted to FMCW
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40Means for monitoring or calibrating
    • G01S7/4052Means for monitoring or calibrating by simulation of echoes
    • G01S7/4082Means for monitoring or calibrating by simulation of echoes using externally generated reference signals, e.g. via remote reflector or transponder
    • G01S7/4091Means for monitoring or calibrating by simulation of echoes using externally generated reference signals, e.g. via remote reflector or transponder during normal radar operation
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40Means for monitoring or calibrating
    • G01S7/4052Means for monitoring or calibrating by simulation of echoes
    • G01S7/4082Means for monitoring or calibrating by simulation of echoes using externally generated reference signals, e.g. via remote reflector or transponder
    • G01S7/4095Means for monitoring or calibrating by simulation of echoes using externally generated reference signals, e.g. via remote reflector or transponder the external reference signals being modulated, e.g. rotating a dihedral reflector or modulating a transponder for simulation of a Doppler echo
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/415Identification of targets based on measurements of movement associated with the target
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/497Means for monitoring or calibrating
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004Means for monitoring or calibrating
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09BEDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
    • G09B9/00Simulators for teaching or training purposes
    • G09B9/54Simulation of radar
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09BEDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
    • G09B9/00Simulators for teaching or training purposes
    • G09B9/56Simulation of sonar

Landscapes

  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Theoretical Computer Science (AREA)
  • Business, Economics & Management (AREA)
  • Educational Administration (AREA)
  • Educational Technology (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

Eine Vorrichtung 10 zum Verarbeiten eines Signals 12 eines Ortungssystems umfasst einen Abtastratenwandler, wobei der Abtastratenwandler eine erste Signalverarbeitungseinheit 14 zum Empfangen des Signals 12, wobei der ersten Signalverarbeitungseinheit 14 ein erster Taktgeber 15 zugeordnet ist sowie eine zweite Signalverarbeitungseinheit 16, die an einen Signalausgang der ersten Signalverarbeitungseinheit 14 gekoppelt ist, wobei der zweiten Signalverarbeitungseinheit 16 ein zweiter Taktgeber 17 zugeordnet ist, aufweist. Der erste Taktgeber 15 ist ausgebildet ist, eine erste Taktfrequenz zu erzeugen und der zweite Taktgeber 17 ist ausgebildet ist, eine von der ersten Taktfrequenz abweichende zweite Taktfrequenz zu erzeugen, wobei ein Verhältnis zwischen erster und zweiter Taktfrequenz auf der Bewegung eines Objekts basiert.
PCT/EP2020/051997 2019-01-28 2020-01-28 Vorrichtung zum verarbeiten eines signals eines ortungssystems sowie verfahren zum simulieren und zum orten eines objekts Ceased WO2020157039A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102019102077.8A DE102019102077A1 (de) 2019-01-28 2019-01-28 Vorrichtung zum Verarbeiten eines Signals eines Ortungssystems sowie Verfahren zum Simulieren und zum Orten eines Objekts
DE102019102077.8 2019-01-28

Publications (2)

Publication Number Publication Date
WO2020157039A2 WO2020157039A2 (de) 2020-08-06
WO2020157039A3 true WO2020157039A3 (de) 2020-09-24

Family

ID=69374294

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2020/051997 Ceased WO2020157039A2 (de) 2019-01-28 2020-01-28 Vorrichtung zum verarbeiten eines signals eines ortungssystems sowie verfahren zum simulieren und zum orten eines objekts

Country Status (2)

Country Link
DE (1) DE102019102077A1 (de)
WO (1) WO2020157039A2 (de)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102019126352A1 (de) * 2019-09-30 2021-04-01 Friedrich-Alexander-Universität Erlangen-Nürnberg Radar-System sowie Verfahren zum Betreiben eines Radar-Systems
US11940556B2 (en) 2021-09-09 2024-03-26 Dspace Gmbh Testing device for testing a distance sensor that operates using electromagnetic waves
DE102021126144A1 (de) * 2021-10-08 2023-04-13 Valeo Schalter Und Sensoren Gmbh Kalibriervorrichtungsanordnung für eine Kraftfahrzeugradarvorrichtung, Kalibriervorrichtung und Kalibrierverfahren
DE102021126142A1 (de) 2021-10-08 2023-04-13 Valeo Schalter Und Sensoren Gmbh Kalibriervorrichtungsanordnung für eine Kraftfahrzeugradarvorrichtung, Kalibriervorrichtung und Kalibrierverfahren
DE102024101567B4 (de) * 2024-01-19 2026-01-29 Jenoptik Robot Gmbh Radarsensorbaugruppe, Verfahren, Computerprogrammprodukt
CN120849753B (zh) * 2025-09-22 2025-11-18 东南大学 一种运动条件下的传感器接收目标信号的计算方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013021454A1 (de) * 2013-12-14 2015-06-18 Jenoptik Robot Gmbh Verfahren und Vorrichtung zum Überwachen eines Umfelds eines Verkehrsüberwachungssystems
KR20160050121A (ko) * 2014-10-28 2016-05-11 한남대학교 산학협력단 다중 샘플링 클럭 주파수를 이용한 레이더 표적 시뮬레이터
DE102016121296A1 (de) * 2016-11-08 2018-05-09 HELLA GmbH & Co. KGaA Vorrichtung und Verfahren zum Simulieren von Radarzielen

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3798590A (en) * 1968-09-12 1974-03-19 Us Navy Signal processing apparatus including doppler dispersion correction means
US5506582A (en) * 1979-01-15 1996-04-09 Lawsine; Leo Signal processing apparatus
DE10347414A1 (de) 2003-10-13 2005-05-04 Bosch Gmbh Robert Elektronisch abstimmbarer Phasenschieber
US10527715B2 (en) 2016-06-20 2020-01-07 Rohde & Schwarz Gmbh & Co. Kg Radar target stimulation device and method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013021454A1 (de) * 2013-12-14 2015-06-18 Jenoptik Robot Gmbh Verfahren und Vorrichtung zum Überwachen eines Umfelds eines Verkehrsüberwachungssystems
KR20160050121A (ko) * 2014-10-28 2016-05-11 한남대학교 산학협력단 다중 샘플링 클럭 주파수를 이용한 레이더 표적 시뮬레이터
DE102016121296A1 (de) * 2016-11-08 2018-05-09 HELLA GmbH & Co. KGaA Vorrichtung und Verfahren zum Simulieren von Radarzielen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PERRY R P ET AL: "Coherent Integration With Range Migration Using Keystone Formatting", RADAR CONFERENCE, 2007 IEEE, IEEE, PI, 1 April 2007 (2007-04-01), pages 863 - 868, XP031181021, ISBN: 978-1-4244-0283-0, DOI: 10.1109/RADAR.2007.374333 *

Also Published As

Publication number Publication date
WO2020157039A2 (de) 2020-08-06
DE102019102077A1 (de) 2020-07-30

Similar Documents

Publication Publication Date Title
WO2020157039A3 (de) Vorrichtung zum verarbeiten eines signals eines ortungssystems sowie verfahren zum simulieren und zum orten eines objekts
MX2022011172A (es) Sistemas, metodos y dispositivos para salida acustica.
EP3843269A3 (de) System und verfahren zur kalibrierung eines frequenzverdopplers
WO2020018811A3 (en) Srs resource configuration enhancements
IL286336A (en) A vector signal generator operating at microwave frequencies, and a method for generating time-controlled vector signals at microwave frequencies
EP3842824A3 (de) Verfahren und vorrichtung zur verarbeitung eines radarsignals
SA519401991B1 (ar) طريقة لإرسال الإشارات المرجعية وجهاز إرسال
EP4693975A3 (de) Zeitcodiertes datenkommunikationsprotokoll, vorrichtung und verfahren zum erzeugen und empfangen eines datensignals
WO2019203886A8 (en) Contextual auto-completion for assistant systems
WO2020145879A3 (en) Methods and apparatuses for positioning based on the sounding reference signal
EP4475017A3 (de) Verfahren und vorrichtung zur benutzerauthentifizierung
EP3686622A3 (de) Fahrzeugantriebssteuerungsvorrichtung mit schallsensor und fahrzeugantriebssteuerungsverfahren mit der fahrzeugantriebssteuerungsvorrichtung
US20180137876A1 (en) Speech Signal Processing System and Devices
EP4637186A3 (de) Signalverarbeitungsvorrichtung, system und verfahren zur verarbeitung von audiosignalen
SG11201901441QA (en) Information processing apparatus, speech recognition system, and information processing method
EP4346175A3 (de) Referenzsignalübertragungsverfahren, -vorrichtung und -system
WO2021178985A3 (en) Methods and apparatus for communicating sounding reference signals
WO2016020511A3 (de) Verfahren zur senkung der verständlichkeit von sprachsignalen und trennbauteil zur beeinflussung der schallübertragung
MY205964A (en) Method and device for signal detection
WO2019199349A3 (en) Multi-static frequency diverse waveform (mfdw)
EP2113789A3 (de) Reduktionssysteme zur Radarzielverarbeitung und Verfahren mit kooperativen Überwachungsquellen
MY202741A (en) Apparatuses and methods for superposition based wave synthesis
GB2493030B (en) Method of sound analysis and associated sound synthesis
EP4585970A3 (de) Ultraschalldiagnosevorrichtung und verfahren zum betrieb davon
MY209858A (en) Method for reference signal generation and communications device

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20702447

Country of ref document: EP

Kind code of ref document: A2

122 Ep: pct application non-entry in european phase

Ref document number: 20702447

Country of ref document: EP

Kind code of ref document: A2