1. Wireless Power Transmission – WPT
A status report
Don Beattie, G3BJ

2. Topics What is happening? What is WPT? What are the plans for WPT?
What are the technical characteristics of WPT?
What problems could this create?
What action is needed?

3. ITU – what is happening (1)?
Question (January 2013):
1 Under what category of spectrum use should administrations consider WPT: ISM, or other?
2 What radio frequency bands are most suitable for WPT?
3 What steps are required to ensure that radiocommunication services, including the radio astronomy service, are protected from WPT operations?

4. ITU – what is happening (2)?
WRC19 agenda Item 9.1.6:
Studies concerning Wireless Power Transmission (WPT) for electric vehicles:
to assess the impact of WPT for electric vehicles on radiocommunication services;
to study suitable harmonized frequency ranges which would minimize the impact on radiocommunication services from WPT for electrical vehicles.

5. What is WPT? Is it a “Short Range Device” ?
Is it ISM (Industrial, Scientific and Medical)
Different spurious emission “rules” for each.
SRD -> defined by CEPT and ITU emission limits
ISM -> defined by CISPR limits
Both are similar, and inadequate
This uncertainty is making the issue of spurious emissions a complex process and manufacturers are likely to argue for the route which demands the least strict limits

6. What’s happened?
Intensive work in CISPR, CEPT and ITU. Some work in other RTOs
CEPT Report 289
Various draft recommendations in ITU
Arguments in CISPR about calculation of emission limits
Although there are differing views on how to treat WPT: SRD or ISM, in both cases no change felt necessary in Radio Regulations
BUT…….this only concerns the operating frequency of WPT
The real problem is the spurious emission level from WPT

7. Signal-to-noise ratios in the amateur service
Based on 528,000 data points
over a 2 x 24 hour period
between MHz
The amateur service is therefore
highly susceptible to any increase
in the background noise level.

8. What is WPT?
Wireless charging of a range of devices at varying power levels
Frequencies being planned:
19-21 kHz for high power
55-65 kHz for medium power (but some concerns)
79-90 kHz for medium power
kHz for lower power (but still up to 2.4 kW!)
Currently all subject to spurious limits at ERC Rec /SM.329/CISPR11 levels

9. What is WPT(EV)?

10. WPT(EV) in the home environment
Charges the car through induction via a pad under the vehicle, rather than “plug-in”
Power levels from 3.3 to 22 kW
Likely to operate around 85 kHz. The harmonics could cause severe interference to local radio reception – both amateur and broadcast.
Charge times of 3-12 hours
64 installations per km2 (=never more than 88m from one)
Frequency stability and phase noise uncertain
CEPT intends to classify as a “Short Range Device” (SRD)
SRDs & ISM are not permitted to cause interference to radio services! But what is “interference”?

11. What is WPT (Generic)?
In-home devices for charging a range of devices:
Mobile phones and accessories, cameras, AV equipment
Power tools, laptops, lighting, household devices, furniture, television, robots (both domestic and industrial), healthcare, e-bikes, drones, garden equipment
Kitchen appliances (blender, rice-cooker, fryer, mixer), lighting, kitchen countertops
Mainly long-duration charging
High density of deployment (6,500/km2)
Generally kHz

12. Projected MINIMUM spurious emissions - EV
Frequency
-Adjustment -> 30m (dB)
Level at 62.5m cf 10m (dB)
Level at 88m cf 10m (dB)
Absolute 88m with emissions at 10m @ ITU-R SM.329
dBµA/m
dB above background 88m (residential/rural)
dB above background 30m
(residential/rural)
900 kHz
-27.5
-46.6
-49.6
-40.6
7.2/3.1
29.3/25.2
1.6 MHz
-26.0
-32.4
-35.4
-28.8
8.4/14.4
27.8/33.8
1.8 MHz
-25.5
-29.4
8.8/13.8
18.7/23.7
5 MHz
-18.2
-24.4
-27.4
-25.8
15.5/21.5
24.7/30.7
10 MHz
-10
-16.3
-19.3
-20.3
24/29
33.3/38.3

13. Projected MINIMUM spurious emissions - generic
Generic WPT
Installed density projected means maximum distance from a WPT installation is 10m in urban areas. So minimum spurious emission is at ERC level – about 40 dB above background noise if equipment “just” meets the specification.
In 78% of cases the emissions will be 9 dB above ERC levels
However, data from Apple suggests emissions from tested devices may be as good as – 30 dB ref ERC closer to the IARU requested levels

14. SRD
In the past, Short Range Devices in the home environment have been:
Low power, and/or
Short duration transmission
WPT is neither
Some have suggested that existing spurious emission limits for inductive SRDs are appropriate.
CISPR limits assume intermittency and distance spacing, which do not apply to WPT.
WPT is generally high duty cycle, located in residential areas and its harmonics are likely to be spread across a band of frequencies in comes cases the whole of the HF spectrum

15. The CEPT / ITU limits and the noise level
Note limits are some 40-60dB above
noise level at 10m distance. CISPR 11
is similar (not shown). This is also the
generic WPT MINIMUM impact level
WPT EV MINIMUM impact of spurious emissions
Recent measurements in UK on noise levels
and other reports submitted to ITU suggest
that, with the exception of a few “hot spots”,
the ITU-R P372 levels are still a reasonable
assessment of the real world

16. Modelled harmonic field strength WPT-EV

17. Modelled harmonic field strength WPT-EV

18. WPT at these limits will severely impact radio reception
EC Decision 2006/771/EC states: Member States shall designate and make available, on a non- exclusive, non-interference and non-protected basis, the frequency bands for the categories of short-range devices. ‘Non-interference and non-protected basis’ means that no harmful interference may be caused to any radio communications service
ITU RR states Administrations shall take all practicable and necessary steps to ensure that radiation from equipment used for industrial, scientific and medical applications is minimal and that, outside the bands designated for use by this equipment, radiation from such equipment is at a level that does not cause harmful interference to a radiocommunication service and, in particular, to a radionavigation or any other safety service operating in accordance with the provisions of these Regulations
A very significant improvement is needed in emission limits to prevent extensive harmful interference to radio services

19. Mitigation The impact of WPT harmonics can be reduced if:
All WPT installations adopt a single highly accurate fundamental frequency – meaning all harmonics are on “spot frequencies” rather than spread across the spectrum
All WPT systems have a very good phase and sideband noise performance
For generic WPT this is simply not possible

20. What has IARU done?
IARU historically slow to respond ! “Monitoring but not initiating or intervening”
Now have deep involvement in CEPT SE24, WGSE, WGFM, SRD/MG, CISPR and ITU SG1
Not active in ETSI yet. Resource limitations.
Active in ITU SG1/WP1B considering fundamental frequency choice and unwanted emissions
CEPT Report 289 now published. Makes clear the adverse impact on broadcasting, amateur and land fixed/mobile services
Arguing in CISPR for new probability factors in the application of CISPR11 to WPT
Briefing to NATO in Brussels in October 2017
Working with BBC, EBU and the military where we have common agenda
Briefs released to all Regions and via WRC Reflector
But we need more people and more activity in MS with their administrations/NSOs. How do we get this?