TR 103 686 - V1.1.1 - Report on Low Duty Cycle Mitigation for UWB Devices

ETSI TR 103 686

V1.1.1 (2020-12)

Report on

Low Duty Cycle Mitigation

for UWB Devices

TECHNICAL REPORT

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Reference

DTR/ERM-TGUWB-592

Keywords

measurement, report, UWB

ETSI

650 Route des Lucioles

F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - NAF 742 C

Association à but non lucratif enregistrée à la

Sous-Préfecture de Grasse (06) N° 7803/88

Important notice

The present document can be downloaded from:

http://www.etsi.org/standards-search

The present document may be made available in electronic versions and/or in print.

The content of any electronic and/or

print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any

existing or perceived difference in contents between such versions and/or in print, the prevailing version of an ETSI

deliverable is the one made publicly available in PDF format at www.etsi.org/deliver.

Users of the present document should be aware that the document may be subject to revision or change of status.

Information on the current status of this and other ETSI documents is available at

https://portal.etsi.org/TB/ETSIDeliverableStatus.aspx

If you find errors in the present document, please send your comment to one of the following services:

https://portal.etsi.org/People/CommiteeSupportStaff.aspx

No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying

and microfilm except as authorized by written permission of ETSI.

The content of the PDF version shall not be modified without the written authorization of ETSI.

The copyright and the foregoing restriction extend to reproduction in all media.

DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its Members.

3GPP™

and LTE™ are trademarks of ETSI registered for the benefit of its Members and

of the 3GPP Organizational Partners.

oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and

of the oneM2M Partners.

GSM

and the GSM logo are trademarks registered and owned by the GSM Association.

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Contents

Intellectual Property Rights ................................................................................................................................ 4

Foreword ............................................................................................................................................................. 4

Modal verbs terminology .................................................................................................................................... 4

1 Scope ........................................................................................................................................................ 5

2 References ................................................................................................................................................ 5

2.1 Normative references ......................................................................................................................................... 5

2.2 Informative references ........................................................................................................................................ 5

3 Definition of terms, symbols and abbreviations ....................................................................................... 6

3.1 Terms .................................................................................................................................................................. 6

3.2 Symbols .............................................................................................................................................................. 6

3.3 Abbreviations ..................................................................................................................................................... 6

4 Duty cycle in UWB regulations ............................................................................................................... 7

5 T

and T

off

definition ................................................................................................................................ 8

6 Current procedures ................................................................................................................................... 9

6.1 Measurements in ETSI EN 303 883 ................................................................................................................... 9

6.2 Clause B.5 in ETSI EN 302 065 series ............................................................................................................. 10

7 Stricter EC requirements ........................................................................................................................ 10

7.1 No declarations or choices................................................................................................................................ 10

7.2 Test modes........................................................................................................................................................ 11

8 Measurement duty cycle per second or per minute ................................................................................ 11

9 Measurement duty cycle per hour .......................................................................................................... 11

9.1 Introduction ...................................................................................................................................................... 11

9.2 Integration method from ETSI TS 103 060 ...................................................................................................... 11

9.3 Integration method from ETSI TS 103 366 ...................................................................................................... 12

9.4 Alternative proposal ......................................................................................................................................... 13

10 Measurement of duty cycle over large bandwidths ................................................................................ 14

11 Conclusions ............................................................................................................................................ 14

History .............................................................................................................................................................. 15

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Intellectual Property Rights

Essential patents

IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information

pertaining to these essential IPRs, if any, is 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 IPR Policy, no investigation, 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.

Trademarks

The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.

ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no

right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does

not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.

Foreword

This Technical Report (TR) has been produced by ETSI Technical Committee Electromagnetic compatibility and Radio

spectrum Matters (ERM).

Modal verbs terminology

In the present document "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.

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

1 Scope

The present document assesses the current LDC mitigation regulations for UWB applications in light of the requirement

to have clear test criteria for the harmonised standards. It reviews the current regulations and related measurements to

highlight the extra parameters that need to be specified in future harmonised standards. It also proposes a method to

measure the duty cycle such that the requirement per hour can be met.

2 References

2.1 Normative references

Normative references are not applicable in the present document.

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 TR 103 181-2 (V1.1.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);

Short Range Devices (SRD) using Ultra Wide Band (UWB); Transmission characteristics Part 2:

UWB mitigation techniques".

[i.2] ETSI EN 302 372 (V2.1.1): "Short Range Devices (SRD);Tank Level Probing Radar (TLPR)

equipment operating in the frequency ranges 4,5 GHz to 7 GHz, 8,5 GHz to 10,6 GHz, 24,05 GHz

to 27 GHz, 57 GHz to 64 GHz, 75 GHz to 85 GHz; Harmonised Standard covering the essential

requirements of article 3.2 of the Directive 2014/53/EU".

[i.3] ETSI EN 302 729 (V2.1.1): "Short Range Devices (SRD);Level Probing Radar (LPR) equipment

operating in the frequency ranges 6 GHz to 8,5 GHz, 24,05 GHz to 26,5 GHz, 57 GHz to 64 GHz,

75 GHz to 85 GHz; Harmonised Standard covering the essential requirements of article 3.2 of the

Directive 2014/53/EU".

[i.4] CEPT Report 045: "Report from CEPT to the European Commission in response to the Fifth

Mandate to CEPT on ultra-wideband technology to clarify the technical parameters in view of a

potential update of Commission Decision 2007/131/EC".

[i.5] ETSI EN 302 065-1 (V2.1.1): "Short Range Devices (SRD) using Ultra Wide Band technology

(UWB); Harmonised Standard covering the essential requirements of article 3.2 of the Directive

2014/53/EU; Part 1: Requirements for Generic UWB applications".

[i.6] ETSI EN 302 065-2 (V2.1.1): "Short Range Devices (SRD) using Ultra Wide Band technology

(UWB); Harmonised Standard covering the essential requirements of article 3.2 of the Directive

2014/53/EU; Part 2: Requirements for UWB location tracking".

[i.7] ETSI EN 302 065-3 (V2.1.1): "Short Range Devices (SRD) using Ultra Wide Band technology

(UWB); Harmonised Standard covering the essential requirements of article 3.2 of the Directive

2014/53/EU; Part 3: Requirements for UWB devices for ground based vehicular applications".

[i.8] ETSI EN 302 065-4 (V1.1.1): "Short Range Devices (SRD) using Ultra Wide Band technology

(UWB); Harmonised Standard covering the essential requirements of article 3.2 of the Directive

2014/53/EU; Part 4: Material Sensing devices using UWB technology below 10,6 GHz".

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

[i.9] ECC/DEC/(06)04: "ECC Decision of 24 March 2006 on the harmonised conditions for devices

using UWB technology in bands below 10.6 GHz, amended 9 December 2011 and amended

8 March 2019".

[i.10] ECC/REC/(11)09: "ECC Recommendation of 21 October 2011 on UWB Location Tracking

Systems TYPE 2 (LT2), amended 22 May 2015".

[i.11] ECC/REC/(11)10: "ECC Recommendation of 1 November 2010 on location tracking application

for emergency and disaster situations".

[i.12] ECC/DEC/(07)01: "ECC Decision of 30 March 2007 on the harmonised use, exemption from

individual licensing and free circulation of Material Sensing Devices using Ultra-Wideband

(UWB) technology, amended on 26 June 2009, corrected on 18 November 2016 and amended on

8 March 2019".

[i.13] ETSI TS 103 060 (V1.1.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);

Short Range Devices (SRD); Method for a harmonized definition of Duty Cycle Template (DCT)

transmission as a passive mitigation technique used by short range devices and related

conformance test methods".

[i.14] ETSI EN 303 883 (V1.1.1): "Short Range Devices (SRD) using Ultra Wide Band (UWB);

Measurement Techniques".

[i.15] ETSI TS 103 366 (V1.1.1): "Short Range Devices (SRD) using Ultra Wide Band technology

(UWB); Time Domain based Low Duty Cycle Measurement for UWB".

[i.16] ETSI ERM(18)66b042: "Final minutes of the workshop DG GROW ESOs on 6

December 2018".

[i.17] ETSI EN 303 883-1 (V1.2.1): "Short Range Devices (SRD) and Ultra Wide Band (UWB);

Part 1: Measurement techniques for transmitter requirements".

3 Definition of terms, symbols and abbreviations

3.1 Terms

Void.

3.2 Symbols

For the purposes of the present document, the following symbols apply:

Mitigation bandwith

thresh

Threshold power

dis

Disregard time

obs

Observation period

off

Off time

On time

span

Span time of the oscilloscope

trig

Trigger time of the oscilloscope

3.3 Abbreviations

For the purposes of the present document, the following abbreviations apply:

DAA Detect And Avoid

LAES Location tracking Application for Emergency and disaster Situations

LDC Low Duty Cycle

LT2 Location Tracking type 2

UWB Ultra-Wide Band

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

TPC Transmit Power Control

STF Special Task Force

FMCW Frequency Modulated Continuous Wave

4 Duty cycle in UWB regulations

An overview of the use of duty cycle restrictions and permission in UWB regulation is presented in clause 6.1 of ETSI

TR 103 181-2 [i.1]. These are summarized in Table 1 and graphically in Figure 1. Trigger-before-transmit for keyless

entry systems is new and has also been added.

In the table and figure, red colour is used to indicate a mandatory duty cycle restriction. Green is used to show optional

duty cycle limits which if respected allow the device to transmit at higher power levels.

In total, there are essentially three different duty cycle related requirements:

• Maximum T

• Minimum mean T

off

per second

• Maximum duty cycle (either per second or per hour)

- Equivalent to minimum sum T

off

per second or per hour

- Equivalent to maximum sum T

per second or per hour

Tank level probing radars (ETSI EN 302 372 [i.2]) also use a duty cycle defined over one-hour periods. For level

probing radars, duty cycle is an optional mitigation technique (ETSI EN 302 729 [i.3]).

Based on CEPT Report 045 [i.4], the ETSI EN 302 065 series of Harmonised Standards ([i.5] to [i.8]) includes a

trade-off between duty cycle and transmit power in Annex C where the T

can be increased as long as the transmit

power is reduced proportionally and the average T

off

remains above 38 ms.

Figure 1: Duty cycle applicability in UWB regulations

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Table 1: Duty cycle applicability in UWB regulations

Application

Frequency

range

Duty

cycle

specifications

Generic UWB

ECC/DEC/(06)04 [i.9]

3,1 to 4,8 GHz

max = 5 ms

off

mean 38 ms (averaged over

1 sec)

off

> 950 ms per second

< 18 s per hour

Location tracking type 2 (LT2)

ECC/REC/(11)09 [i.10]

2,7 to 3,4 GHz DAA & A maximum duty cycle of

5% per transmitter per second and

a maximum T

= 25 ms also apply

3,4 to 4,8 GHz A maximum duty cycle of 5 % per

transmitter per second and a

maximum T

= 25 ms apply

Location tracking for emergency services

(LAES)

ECC/REC/(11)10 [i.11]

3,1 to 3,4 GHz DAA & a maximum duty cycle of

5 % per transmitter per second

also applies.

3,4 to 4,8 GHz A maximum duty cycle of 5 % per

transmitter per second

For indoor and mobile transmitters,

additional maximum duty cycle of

1,5 % per transmitter per minute.

Vehicular UWB

ECC/DEC/(06)04 [i.9]

2,7 to 4,8 GHz

6,0 to 8,5 GHz

max = 5 ms

off

mean 38 ms (averaged over

1 s)

off

> 950 ms per second

< 18 s per hour (see note)

Exterior limit also applies

Trigger-before-transmit

ECC/DEC/(06)04 [i.9]

3,8 to 4,2 GHz LDC 0,5 % (in 1 h)

6,0 to 8,5 GHz LDC 0,5% (in 1 h) or TPC

Material sensing

ECC/DEC/(07)01 [i.12]

2,69 to 2,70 GHz

3,4 to 3,8 GHz

4,8 to 5,0 GHz

Limitation of the Duty Cycle to

10 % per second in each of these

dedicated bandwidths

3,1 to 4,8 GHz The LDC mitigation technique and

its limits is defined in the relevant

version of the Harmonised

European Standard ETSI

EN 302 065-1 [i.5]. When LDC is

implemented, no fixed outdoor

permitted.

NOTE: Within the band 3,4 GHz to 4,8 GHz, this requirement does not apply for operation with vehicle speed above

40 km/h. For vehicle speeds between 20 km/h and 40 km/h a gradual implementation of the long-term duty

cycle limit from 18 s to 180 s per hour is required.

5 T

and T

off

definition

ECC/DEC/(06)04 [i.9] defines T

and T

off

as:

• T

- T

is defined as the duration of a burst irrespective of the number of pulses contained.

• T

off

- T

off

is defined as the time interval between two consecutive bursts when the UWB emission is kept idle.

These definitions of T

and T

off

depend heavily on the interpretation of the concept of a burst.

Previously, ETSI TC ERM organized a Special Task Force (STF 411), with members from TG28 and TGUWB, to find

a harmonised definition and measurement methods for low duty cycle transmissions. STF 411 published its

recommendations as ETSI TS 103 060 [i.13] in September 2013.

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

To decide whether signals are on or off, ETSI TS 103 060 [i.13] first defines a threshold power level, P

thresh

, above

which signals are considered on. Clause 4.1.2 of ETSI TS 103 060 [i.13] specifies that:

Unless otherwise defined P

thresh

is -26 dBc for systems other than UWB and -10 dBc for UWB systems.

This power is measured in a limited mitigation bandwidth, F

Furthermore, ETSI TS 103 060 [i.13] also defines a disregard time, T

dis

, in clause 4.1.7.2:

dis

is defined as the time interval below which interruptions within a transmission are considered part of T

on.

dis

is a measurement procedure parameter, it is not subjected to restrictions but it must be declared by the

device manufacturer".

Both concepts are illustrated in Figure 2, which was copied from ETSI TS 103 060 [i.13].

Figure 2: Illustration P

thresh

, T

off

and T

dis

This additional factor T

dis

ignores 'internal' gaps in the UWB signal and allows UWB signals to meet the restrictions on

the mean T

off

time. Previously, the harmonised standards let the manufacturer declare the T

dis

used. Since the European

Commission no longer allows manufacturer declarations in harmonised standards, a suitable value for T

dis

will have to

be chosen for each application-specific harmonised standard.

ETSI TS 103 060 [i.13] does not use the burst concept. However, following its definitions, a burst is a series of pulses

separated from the next pulse by time intervals less than the disregard time T

dis

6 Current procedures

6.1 Measurements in ETSI EN 303 883

At the time of writing, all relevant Harmonised Standards ([i.5], [i.6], [i.7] and [i.8]) refer to ETSI EN 303 883 [i.14],

clause 7.4.8 for the measurement of the duty cycle. That clause contains two alternative methods, method 1 based on

measurements with a spectrum analyser in clause 7.4.8.1 and method 2 with a high-speed sampling oscilloscope in

clause 7.4.8.2.

Method 1, from clause 7.4.8.1, configures the spectrum analyser in zero span mode, centred on the frequency at which

the highest mean spectral density was observed. The resolution bandwidth should be set to the 'highest available

bandwidth' up to a maximum of 50 MHz. There is no clear definition of P

thresh

. The method then measures the T

and

off

in a pulse frame with maximum T

and minimum T

off

taking into account T

dis

from ETSI TS 103 060 [i.13].

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Method 2, in clause 7.4.8.2, is based on ETSI TS 103 366 [i.15]. A high-speed sampling oscilloscope is used to record

the signal in the time domain. The sampling frequency should be at least twice the pulse bandwidth to capture the

envelope, while the input bandwidth of the scope should be above the upper boundary of the operating bandwidth.

These recordings are then post-processed to extract the duty cycle. No mitigation bandwidth F

is used. In Annex B of

ETSI TS 103 366 [i.15], it is suggested that the threshold used by the postprocessing tool corresponds to 30 % of the

mean voltage of the signal. The disregard time T

dis

is used to determine the duration of bursts.

Method 2 also contains an integration method for observation periods longer than the acquisition and storage capability

of the oscilloscope. In that case, it is suggested that the trigger is delayed by successive spans of the acquisition period

until the full observation period is covered.

6.2 Clause B.5 in ETSI EN 302 065 series

Annex B in the ETSI EN 302 065 series ([i.5] to [i.8]) contains an application form for testing in which the

manufacturer informs the test laboratory of various product details to guide the test house in choosing the right

configurations, tests and test conditions. This application form should form an integral part of the test report.

In clause B.5.2 ([i.5] to [i.8]), the manufacturer specifies the parameters of the low duty cycle scheme implemented:

NOTE 1: If there is a specific mode for testing the manufacture have to declare.

NOTE 2: Table with different parameters for different mitigation techniques.

DAA

LDC

Frequency range A

Frequency range B

Frequency range C

b) T

, max

c) T

off

, mean

off

in1s

in 1h

f) T

dis

7 Stricter EC requirements

7.1 No declarations or choices

Recently, the courts have viewed harmonised standards as legal documents and they are therefore more closely

scrutinized by the European Commission. The minutes of a meeting between the European Commission, ETSI and

CENELEC from December 2018 [i.16] state that:

• Manufacturer-declared requirements, performance criteria and/or tests are not allowed in harmonised

standards.

• Harmonised standards should report precise performance criteria, technical specifications and tests. If deemed

appropriate, the harmonised standard can define different precise performance criteria, technical specifications

and tests for different (sub)categories or (sub)classes of radio equipment.

In the context of LDC, this means that the harmonised standards need to be updated. The current declarations, like T

dis

and

per hour, should be specified and/or tested in the relevant harmonised standard.

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

7.2 Test modes

When an LDC device transmits at most 18 s per hour, any kind of emission testing would take a very long time to

perform without a test mode. Testing of LDC devices would take at least 200 (3 600/18) times longer than for other

UWB devices. In order to lead to practical test durations, devices with a long-term duty cycle (i.e. restrictions over

periods longer than 1 s) therefore require a test mode that allows to disable this long-term duty cycle mechanism.

8 Measurement duty cycle per second or per minute

A large number of devices, both spectrum analysers and oscilloscopes, can capture at least 1 minute of data with high

time resolution. The methods discussed in clause 6 in the present document can therefore be used. Post-processing of

the measurement data then allows to extract the requirement parameters, including:

• Maximum T

;

• Minimum mean T

off

per second;

• Maximum duty cycle per second:

- Equivalent to minimum sum T

off

per second;

- Equivalent to maximum sum T

per second;

provided that the related harmonised standard defines the required parameters (minimum P

thresh

, maximum F

and

maximum T

dis

The fact that both spectrum analysers and oscilloscopes can be used for these measurements ensures wide-spread

availability of the required equipment in test laboratories and throughout the industry.

9 Measurement duty cycle per hour

9.1 Introduction

The methods of clause 6 in the present document are not able to capture the duty cycle over one-hour periods like the

requirement that

< 18 s per hour for generic UWB applications. Measurement devices do not support such a long

observation interval at high enough time resolutions.

Both methods, using the spectrum analyser and the oscilloscope, propose methods to capture durations longer than the

device's signal acquisition time. These integration methods will be discussed in the next two clauses and will be shown

to have some flaws that do not make them generally applicable. A generic solution that avoids these flaws is proposed

and discussed in the final section.

9.2 Integration method from ETSI TS 103 060

In its clause 5.1.3 and Figure 9 (copied here as Figure 3), ETSI TS 103 060 [i.13] proposes the following integration

method to extend the acquisition time:

"In this case acquisition of the signal is triggered on a defined power level. This trigger level should be lower

than P

thresh

in order to capture the entire signal of interest. Upon triggering the signal is acquired for a certain

period of time ("Acquisition time") which shall be at least as long as the expected duration of the transmission.

The acquired data is then time-stamped and stored in memory. With the next transmission the acquisition is

triggered again, and so on, until T

obs

has been reached".

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Figure 3: ETSI TS 103 060 [i.13] long-term integration method

However, this method is not suitable for all signals since the on period of the signal needs to be shorter than the

acquisition time and cannot repeat faster than the time required to store the data.

9.3 Integration method from ETSI TS 103 366

In its clause 5.3 and Figure 5 (copied here as Figure 4), ETSI TS 103 366 [i.15] proposes the following integration

method:

"2) Consider the T

obs

time and check if the Oscilloscope is capable to acquire and store the whole observation

period:

a) If it is the case, save the signal acquired during the whole T

obs

time, and go to step 3.

b) Otherwise:

i) Save the signal that the Oscilloscope can acquire and store.

ii) Record the time

Tspan

of the acquired signal.

iii) Set the new trigger time as:

TspanTtrigTtrig +=

iv) Check if the new trigger time is less or equal than the T

obs

time:

1) If it is the case, repeat the steps from i to iv.

2) Otherwise, go to step 3 (post processing of all acquired and stored signal during T

obs

)".

ETSI

TR 103 686 V1.1.1 (2020

12)

Figure 4: ETSI TS 103 366 [i.15] long-term integration method

This could only work if the transmissions have the same format every time and it could somehow be arranged that the

trigger is always at the same point in the transmission. This method is therefore not suited to all signal formats either.

Moreover, in practice the maximum trigger delay is limited and does not allow delaying up to 1 h.

9.4 Alternative proposal

Both methods from ETSI TS 103 060 [i.13] and ETSI TS 103 366 [i.15] have short-comings and are not able to reliably

capture all signal formats over one-hour observation periods. This clause therefore proposes an alternative, in which the

duty cycle is measured over a shorter interval while guaranteeing that the limit is met.

The requirement

< 18 s per hour corresponds to a maximum duty cycle of 0,5 % per hour. If the harmonised

standards fix a measurement interval for long term duty cycle below one hour while mandating that the maximum duty

cycle in that interval is 0,5 %, the requirement that

< 18 s per hour will automatically be met.

Table 2 lists the maximum

per second and per measurement interval for a number of measurement durations. The

maximum

over the measurement duration is always fixed to 0,5 % to ensure that T

< 18 s per hour. If the

measurement duration is fixed to 1 s, the maximum duty cycle in that second needs to be 0,5 % to ensure that the duty

cycle requirement per hour is also met. Once the measurement duration is ten seconds or longer, the

per second

can be at its maximum of 50 ms. Longer measurement durations offer more flexibility, in the sense that more busy

seconds can be compensate by other quieter periods to achieve an overall duty cycle of 0,5 %.

The measurement durations can be fixed by the harmonised standards based on the available equipment at the time of

drafting.

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

Table 2: Duty cycle limits versus measurement duration

Measurement

duration

Max

any second

Max

measurement duration

Comment

always 0,5 % of

measurement duration

1 s 5 ms 5 ms For measurement durations below to 10 s,

the 0,5 % duty cycle requirement limits the

per second.

1 < X < 10 s 5X ms 5X ms

10 s 50 ms 50 ms

30 s 50 ms 150 ms Beyond 10 s, it gets more interesting, since

more active seconds can be compensated

by quiet ones.

1 minute 50 ms 300 ms

1 < X < 60 minutes 50 ms 300X ms

10 Measurement of duty cycle over large bandwidths

Material sensing devices need to measure the duty cycle over specific, larger bandwidths, i.e. 2,69 to 2,70 GHz,

3,4 to 3,8 GHz and 4,8 to 5,0 GHz.

Spectrum analysers do not have resolution bandwidths large enough to capture up to 400 MHz bandwidth.

Oscilloscopes are not able to limit the signal bandwidth at all.

For pulsed systems, the duty cycle in a specific bandwidth will be close to the duty cycle over the whole band, so there

is no need for a special method. For FMCW and stepped-frequency systems based, the draft update of ETSI

EN 303 883-1 [i.17] contains a method to measure the duty cycle within a frequency band on two synchronized

spectrum analysers.

11 Conclusions

This report gives an overview of the current duty regulations for UWB applications.

To satisfy the requirements from the European Commission, the next generation of harmonised standards will need to

include all parameters required to specify the duty cycle profile. In particular, declarations of the disregard time T

dis

are

no longer allowed. Every harmonised standard will need to specify T

dis

taking into account the applicable usage

scenarios.

To be able to measure the duty cycle requirement per hour, this report proposes to fix the duty cycle over shorter

measurement durations to the duty cycle limit per hour. For all other compliance tests, the UWB device should include

a test mode in which the duty cycle per hour restriction is removed such that the tests can be completed within

reasonable time.

ETSI

ETSI TR 103 686 V1.1.1 (2020

12)

History

Document history

V1.1.1 December 2020 Publication