ETSI TS 103 788 V1.1.1 (2022-09)

TECHNICAL SPECIFICATION
Short Range Devices (SRD) and Ultra Wide Band (UWB);
Measurement techniques and specification for
RX conformance tests with target simulator

2 ETSI TS 103 788 V1.1.1 (2022-09)

Reference
DTS/ERM-TGUWB-607
Keywords
measurement, SRD, UWB
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ETSI
3 ETSI TS 103 788 V1.1.1 (2022-09)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Executive summary . 5
Introduction . 5
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 8
3.1 Terms . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 Overview . 9
4.1 Info . 9
5 Radar Target Simulator (Radar Echo Generators) . 9
5.1 Types . 9
5.1.1 General . 9
5.1.2 Analog . 9
5.1.3 Digital . 10
5.1.4 Hybrid . 10
5.1.5 Frontends . 11
5.1.6 Differences . 11
5.2 Parameters . 11
5.2.1 General . 11
5.2.2 RCS . 11
5.2.3 Radial velocity . 12
5.2.4 Minimum range . 13
5.2.5 Accuracy . 13
5.2.6 Unwanted objects and crosstalk . 14
5.2.7 Phase noise. 14
5.2.8 RF saturation . 14
5.2.9 Temperature effects . 14
5.3 RTS/REG requirements - Parameter summary. 14
6 Measurement Setups. 16
6.1 General Guidance . 16
6.2 Antennas . 17
6.3 Anechoic Chamber Setup . 17
6.3.1 General . 17
6.3.2 Direct far-field setup . 18
6.3.3 Near-field/far-field transforming setup . 19
6.4 Positioner . 19
7 Radiated Measurements . 20
7.1 Receiver Baseline Sensitivity . 20
7.1.1 General . 20
7.1.2 Radar Echo Generation/Target Simulation . 20
7.1.3 Receiver Sensitivity . 21
7.2 Receiver Baseline Resilience . 21
7.2.1 General . 21
7.2.2 Interference Signal Generation . 21
7.2.2.1 General . 21
ETSI
4 ETSI TS 103 788 V1.1.1 (2022-09)
7.2.2.2 Interference signal injection through separated mmW remote header (setup 1) . 21
7.2.2.3 Interference signal injection through combiner with single mmW remote header (setup 2) . 22
7.2.2.4 Interference signal injection with IF path of RTS/REG (setup 3) . 22
7.3 Temperature Testing. 23
Annex A (informative): Change History . 24
History . 25

ETSI
5 ETSI TS 103 788 V1.1.1 (2022-09)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
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Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Electromagnetic compatibility and
Radio spectrum Matters (ERM).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Executive summary
Automotive radars follow regulation for certification testing and the respective definition of limits for compliance. The
present document describes new types of test equipment such as radar target generators, anechoic chambers and
methods of measurements.
ETSI
6 ETSI TS 103 788 V1.1.1 (2022-09)
Introduction
Radars are increasingly taking a more important role in the evolving fusion of a variety of sensors to enhance Advanced
Driver-Assistance Systems (ADAS) in the direction of Autonomous Driving (AD). Many of these functions go beyond
driving convenience are related to safety, either reducing road accidents with all participants or ensuring pedestrian
safety. Automotive radar regulations need to improve test coverage and the definition of compliance limits. The former
requires a new type of test equipment, the radar echo generator or also called radar target simulator, which enables a
radar to be functionally tested in a controlled laboratory environment as it would be operating on the road. The later
requires new methods to achieve far-field measurement accuracy in much smaller distances.
With the out phasing of 24 GHz automotive radar implementations in some regions, the present document focusses on
the high frequencies, namely 76 GHz to 81 GHz, without limiting measurement procedures and methods to these
frequencies. Radars, operating in these frequency bands, require relatively large measurement distances, using the
traditional far-field setups, resulting on costly and for some measurements impractical chamber dimensions to achieve
reasonable test accuracies. Compact antenna test range concepts for over-the-air testing will go a long way in
supporting regulators and the industry to establish the compliance limits required for the modern larger MIMO
automotive radar sensors.
At higher frequencies, such as E-Band frequencies where automotive vehicle radar operates today, larger bandwidths,
and MIMO Tx/Rx arrays implementations enable improved resolutions to create more sophisticated ADAS/AD
functions. Higher integration and number of devices in combination with higher frequencies and larger bandwidths
might also require to allow compliance limits to adopt the use of intermediate-frequency test strategies. MIMO
technology demands the use of monostatic antennas to enhance the accuracy of angular measurement resolution and
resolution.
ETSI
7 ETSI TS 103 788 V1.1.1 (2022-09)
1 Scope
The present document contains information on radar target simulators and their application for radar tests identified in
ETSI EN 303 883-1 [i.1] and ETSI EN 303 883-2 [i.2].
The present document describes measurement setups and approaches for anechoic chambers both far-field and near
field-to-far field transforming.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 303 883-1 (V1.2.1) (02-2021): "Short Range Devices (SRD) and Ultra Wide Band
(UWB); Part 1: Measurement techniques for transmitter requirements".
[i.2] ETSI EN 303 883-2 (V1.2.1) (02-2021): "Short Range Devices (SRD) and Ultra Wide Band
(UWB); Part 2: Measurement techniques for receiver requirements".
[i.3] Federal Communications Commission § 15.253 (20.09.2022).
NOTE: Available at https://www.gpo.gov/fdsys/pkg/CFR-2013-title47-vol1/pdf/CFR-2013-title47-vol1-sec15-
253.pdf.
ETSI
8 ETSI TS 103 788 V1.1.1 (2022-09)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
radar echo generator (REG), radar target simulator (RTS): Are both descriptions for the same type of equipment
that can generate synthetic radar echo returns for testing of an actively transmitting radar sensor. This test instruments
are specifically designed to test actively transmitting radar sensors according to ETSI EN harmonised standards.
3.2 Symbols
For the purposes of the present document, the following symbols apply:
� Attenuation within the RTS/REG [in dB]
���
� Speed of light [in m/s]
�
� the physical distance between RTS/REG frontend and EUT [in m]
���
� Centre frequency of the Local Oscillator of the RTS/REG [in Hz]
�
� Doppler frequency shift
�
� Antenna gain of the RTS/REG transmit antenna [in dB]
��_���
� Antenna gain of the RTS/REG receive antenna [in dB]
��_���
� RTS/REG processing time [in s]
����
� Time of flight [in s]
���
� distance of the artificial object generated by the RTS/REG [in m]
� Simulated distance of a target [in m]
���
� Speed of electromagnetic wave in medium 1 [in m/s]
�
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
5G Fifth-Generation
AD Autonomous Driving
ADAS Advanced Driver Assistance Systems
ADC Analog Digital Converter
AWG Arbitrary Waveform Generator
CATR Compact Antenna Test Range
CW Continuous Wave
DAC Digital Analogue Converter
DRFM Digital Radio Frequency Memory
EUT Equipment Under Test
FCC Federal Communications Commission
FF Far Field
FFT Fast Fourier Transformation
FMCW Frequency Modulated Continuous Wave
FODL Fiber Optical Delay Line
FOV Field Of View
FSPL Free Space Path Loss
GUI Graphical User Interface
I/Q Inphase/Quadrature phase
IF Intermediate Frequency
LO Local Oscillator
LRR Long Range Radar
MIMO Multiple Input Multiple Output
mmW millimetre Wave
MRR Mid Range Radar
OSI Open Simulation Interface
RBR Receiver Baseline Resilience
ETSI
9 ETSI TS 103 788 V1.1.1 (2022-09)
RBS Receiver Baseline Sensitivity
RCS Radar Cross Section
REG Radar Echo Generator
RF Radio Frequency
RTS Radar Target Simulator
RX Receive
SG Signal Generator
SRR Short Range Radar
TX Transmit
US United States
4 Overview
4.1 Info
The present document provides practical information and guidance on RTS/REG for compliance tests of Short Range
devices such as automotive radars. The applicability of the procedures described in the present document is not limited
to EUT covered.
5 Radar Target Simulator (Radar Echo Generators)
5.1 Types
5.1.1 General
There is a variety of Radar Target Simulator/Radar Echo Generator (RTS/REG) solutions available, that range from
simple reflectors to complex digital test equipment. This clause describes several types of equipment.
5.1.2 Analog
Analog target simulators apply physical delay lines to delay the incoming electromagnetic wave from the radar and
simulates an object in a certain range � from the radar, formula (1). The simulated range is the sum of the speed of
���
the electromagnetic wave in air/vacuum (speed of light � ) multiplied by the time of flight � divided by two and the
� ���
speed in a certain medium (with speed � ) multiplied by the time within the medium � respectively. This includes
� ����
the time for passing physical distance to the RTS/REG forth and back as well as the internal signal processing time.
� �
� ���
� = +� � (1)
��� � ����
�
• � Simulated distance of a target [in m]
���
• � Speed of light [in m/s]
�
• � Time of flight [in s]
���
• � Speed of electromagnetic wave in medium 1 [in m/s]
�
• � RTS/REG processing time [in s]
����
To delay the signal Fiber Optical Delay Lines (FODLs) are often used. FODLs are relatively flexible, phase coherent
and can create small systems that convert the RF signal of the radar to optical and delay of a certain length. Often an
Intermediate Frequency (IF) is used as low frequency signal handling is easier and creates less loss. After delay, the
signal is then reconverted to RF and retransmitted to the radar. Some systems are also able to introduce Doppler
frequency shift.
ETSI
10 ETSI TS 103 788 V1.1.1 (2022-09)
FODLs offer constant delay versus frequency, are immune to vibration, are largely resistant to electromagnetic
interference, and fiber delays do not radiate energy. Repeatability of simulation, low system cost and time-savings are
key advantages. FODLs cannot generate time-variant range-Doppler targets (a target which has a change in range and
Doppler over time due to its own dynamics), nor do they offer continuous range settings or arbitrary signal attenuation
and gain.
RCS can be simulated by attenuating the radar signal. After considering free space loss and antenna gain (EUT and
RTS/REG) the attenuated signal indicates a target with a certain RCS.
Figure 1 shows a simplified sketch of the optical delay line system including Doppler frequency shift f .
D
Figure 1: Optical delay line including Doppler frequency shift f
D
5.1.3 Digital
Digital target simulators rely on digital signal processing. The target generator receives an electromagnetic wave from
the radar and modifies it digitally to picture the desired scenario. Adding delay on the signal simulates a distance to an
object, frequency shift simulates a Doppler shift indicating the velocity of an object, and signal attenuation indicate a
certain RCS. In addition, it is possible to add multiple delays, frequency shifts, and attenuation simulating multiple
targets.
Often Digital Radio Frequency Memory (DRFM) is used to manipulate the radar signal digitally - down-converting,
filtering and digitizing the received RF signal before storing and modifying it. Signals are then reconverted to analogue
and mixed to RF frequency using the same Local Oscillator (LO) used for down-conversion. This is important to reduce
phase noise. The minimum delay introduced by a DRFM is mainly limited by its ADC and DAC. In addition, signal
processing adds a delay to the radar echo signal. Typical minimum range delays range from below 100 ns to below
1 µs. A further consideration is how the analogue RF signal is represented in the digital domain (amplitude, phase, I/Q)
and the number of bits, because this is what mainly determines the DRFM's signal fidelity. Figure 2 shows a sketch of a

digital representation of an RTS/REG where f denotes the carrier frequency of the down converting local oscillator.
c
Figure 2: Digital representation of an RTS/REG
5.1.4 Hybrid
Hybrid target generators combine analogue and digital target simulator architectures and reduce the disadvantages of
each individual approach. Usually, the analogue technique is used to simulate short distances which is more complex
when using a digital target simulator since the required signal processing time limits the distance minimum that can be
simulated.
On the other hand, the benefit of the high flexibility of digital target simulators can be used to simulate more complex
schemes with multiple targets. Generating a scenario using analogue and digital simulation techniques requires precise
synchronization and calibration between both modes.
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11 ETSI TS 103 788 V1.1.1 (2022-09)
5.1.5 Frontends
For different test needs, different form factors of target simulators exist. Integrated RF architecture combines the RF
frontend as well as signal processing hardware/delay lines in one chassis.
A remote frontend has a separated RF frontend including mixers. Usually the connection to a base unit with delay line
and controller is done using IF cables. Remote frontends offer more flexible use cases and easier integration into
systems while an integrated RF target simulator eliminates possible problems with an accurate calibration of the flexible
IF cables. All types of radar target simulators can be built as integrated RF or remote frontend type.
5.1.6 Differences
The analogue target simulator offers the possibility to simulate short distances while a longer signal processing delay in
the digital units results in a greater minimum range to an object. On the other hand, the digital target simulator often
offers more flexibility to simulate complex scenarios with multiple targets. Analog target simulators exist with one
fixed distance, multiple fixed distances or variable distance using a switch matrix to toggle between different fiber-optic
lengths. Faster switching of the distances can simulate a dynamic scenario of a target but phase jumps and attenuation.
Depending on the update rate of the radar, the required phase coherence and RCS switching between different lengths
back and forth could also simulate multiple targets.
The hybrid target simulator combines both approaches utilizing the fiber-optic cable of the analogue RTS/REG to
simulating short distances and the flexibility of the digital RTS/REG for more distant and complex scenarios.
5.2 Parameters
5.2.1 General
There are many technical parameters of a RTS/REG that have to be defined before testing a radar sensor. This clause
explains how to understand and interpret these parameters.
5.2.2 RCS
The relative size of an object detected by a radar sensor is defined as Radar Cross Section (RCS). Not only the RCS
absolute value is important, but also the dynamic range of the RCS that can be simulated. As there can be targets in
close range and far range with high and low RCS for example, the dynamic range is important. The dynamic range
defines power values which can be simulated by the instrument.
In the following the effect on the RCS of different RTS/REG settings and measurement setup specific parameters are
described.
The RCS calculation within a RTS/REG is done by the following formula (2).
� � ��
� ���
� �
��� = −� + � + � +20���� � −10��� 4� +40���( ) (2)
��� �� ��
��� ���
� �
� ���
• ��� Resulting Radar Cross Section
• � Attenuation within the RTS/REG [in dB]
���
• � Antenna gain of the RTS/REG transmit antenna [in dB]
��_���
• � Antenna gain of the RTS/REG receive antenna [in dB]
��_���
• � Speed of light [in m/s]
�
• � Centre frequency the RTS/REG is set to [in Hz]
�
• � The physical distance between RTS/REG frontend and EUT [in m]
���
• � Distance of the artificial object generated by the RTS/REG [in m]; e.g. 150 m
ETSI
12 ETSI TS 103 788 V1.1.1 (2022-09)
In contrast to over the air measurements with corner reflectors, the RCS value is a function of the generated target
distance as well as the physical distance between RTS/REG and radar under test. This leads to a "range dependent" RCS
cov
...