1. Project: IEEE P802.15 Working Group for Wireless Body Area Networks (WBANs)
Submission Title: [Limitations of WPT carrier frequency for the Implant Devices]
Date Submitted: [Mar. 2009]
Source: [KiBum Kwon, YangMoon Yoon, SangYun Lee, WonHo Jang]
Company [KORPA (Korea Radio Promotion Agency)]
Voice: [ ]
Re: []
Abstract: [This document presents considerations of WPT carrier frequency for the implant devices]
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P

2. Limitations of WPT carrier frequency for the Implant Devices
KiBum Kwon, YangMoon Yoon, SangYun Lee, WonHo Jang KORPA (Korea Radio Promotion Agency)
Good afternoon. Nice to meet you. I’m glad to see you again after Dallas meeting.
Let me introduce myself. My name is KiBum Kwon. And I’m senior engineer working in KORPA.
OK, now I’d like to explain why wireless power transmission scheme need for the implant devices and what limitations are considered for using wireless power transmission.

3. Purpose and Contents Contents
This document presents considerations of WPT (Wireless Power Transmission) carrier frequency for the implant devices
Contents
Advantages of WPT
What we consider about WPT for TG 6 Standardization?
What kind of frequency we could consider for WPT?
General Public Exposure limits to electromagnetic radiation
Future Works for Proposals of TG 6 Standardization with Wireless Power Transmission
Even though this page shows that the purpose of presentation is just considering about WPT frequency, but I’d like to propose WPT to TG6 standardization.
If I have a chance, I’d like to propose WPT to TG6 standardization with formal style in Montreal meeting. 3

4. Energy Limitation of Implant Devices
It is difficult to change and charge the implant device’s battery rather than that of out-body device.
The life time of implant device for WBAN depends on the battery capacity.
Since shape and size of battery is constraint.
OK, when we design implant devices, we should be faced with energy limitation problem. Because it is difficult to change and charge battery of the implant devices rather than that of out-body devices.
As you know a battery capacity depends on battery shape and size. Of course, battery capacity could be various according to what schemes are used at the same constraint.
This figure shows the mini battery in capsule endoscope.
E.g.) Capsule Endoscope 4

5. Advantages of Wireless Power Transmission
We can extend the lifetime of implant device and be free to the power-constrained characteristics.
We can reduce the battery size in manufacturing the implant device.
So, minimizing the device size
If we use wireless power transmission for implant devices, we can extend the life time of implant devices and can be free from the power-constrained characteristics. Some kind of device’s life time could become semi-permanent.
And we can also reduce the battery size in manufacturing the implant device. Finally, we may not take battery into account. So, we can make the device without considering of space for battery. 5

6. What we consider about WPT for TG 6 Standardization?
WPT Schemes
RF radiation
Inductive coupling
…ETC
We may not need to consider currently about what WPT schemes used.
But, we should check about WPT carrier frequency since it is related to Safety and Efficiency of Power Transmission.
OK, Let’s think about the items for TG6 standardization with WPT.
Even if there are various WPT schemes such as RF radiation, Inductive coupling, etc, but we may not need to consider about what WPT schemes used.
Because my proposal is not focused on WPT scheme itself but on limitations for WPT first.
OK, let’s think about the conditions for safety and efficiency of power transmission.
These are mainly related to not only transmitting power level but also carrier frequency for power transmission.
So, we should check about WPT carrier frequency first. 6

7. What kind of frequency we could consider for WPT?
90kHz ~ 110kHz (a)
Traditional frequency band for inductive coupling
400MHz (b)
Nearby MICS band
2.4GHz (c)
ISM band
Worst case for human body (resonance problem)
We can consider some carrier frequencies for WPT.
First, 90kHz to 110kHz bands. These bands have used for inductive coupling.
FCC has defined these band to use inductive coupling.
And second 400MHz band. This band is selected because of nearby MICS band.
Finally, 2.4GHz band. This band is worst case for human body.
As you know, 2.45GHz is used in micro-wave oven. This frequency has the resonance problem with water which contains in large amount of human body. 7

8. What kind of frequency we could consider for WPT?
Selection of Frequency for Wireless Power Transmission
Safety
Probability of affecting to tissues in body could be increased in E-H field using high frequency
Efficiency of Power Transmission
High Power Transmission Rate could be achieved by carrier frequency and transmit power increasing
OK, well, when we select the WPT carrier frequency, which factors should be considered?
Safety and efficiency of power transmission issues are sensitive according to carrier frequency.
Probability of affecting to body tissues in E-H field could be increasing proportional to a square of frequency and transmit power level.
And efficiency of power Transmission is the same case.
This is a big dilema.
Safety and Efficiency are trade off.
But different power limitations are applied for different frequencies
Let’s see the next page
Safty  Trade off  Efficiency 8

9. General Public Exposure limits to electromagnetic radiation
Exposure limits of E-field and H-field strength
(a)
(b)
(c)
(a)
(b)
(c)
Let me check how frequency and transmit power are limited in several countries.
According to the grape, Both of E-field and H-field have no limits or high exposure limits around 100kHz.
But the limit levels are going down according to increasing frequency.
However, the limit levels higher than 400MHz after 2 or 3GHz.
Both of E-field and H-field cases, which have no limits (U.S.) or high exposure limits (Korea, U.K., China, Canada, Japan) in (a) band (yellow).
But, the limit levels are going down in (b) band (cyan).
The limit levels are higher than (b) band after (c) band (pink). 9

10. General Public Exposure limits to electromagnetic radiation
Exposure limits of Power density
(a)
(b)
(c)
The limits of power density level are not existed below 300kHz.
After 300kHz, the exposure limits of power density grape show the similar to exposure limits of E-H field.
The limits of power density level are not existed below 300kHz.
The limits are severest over 10MHz to 400MHz.
But, the limits are more increased after (c) band. 10

11. WPT for the implant devices are available over all frequencies.
Conclusions
WPT for the implant devices are available over all frequencies.
Specially, 90 to 110kHz bands could be allowed to WPT with high power transmission over the power requirement of WBAN devices.
But, SAR which is one of important factors to analyze to impact of human body is not considered with exposure limits for WPT yet.
WPT for the implant devices are available over all frequencies under exposure limits.
Specially, 90 to 110kHz bands could be allowed to WPT with high power transmission over the power requirement of WBAN devices.
But, SAR is not considered yet. It is one of important factors to analyze to impact of human body by radio waves. So, we will continue the study of influence and relation of SAR and exposure limits for WPT. 11

12. Proposals for Standardization
Future Works for Proposals of TG 6 Standardization with Wireless Power Transmission
Proposals for Standardization
Maximum WPT Tx. Power depends on set of WPT carrier frequencies
within Exposure limits of E-H field and Power density and SAR limits.
As I mentioned at the beginning, I’d like to propose about WPT for TG6 standardization at next meeting based on Maximum WPT Tx. Power, which depends on set of WPT carrier frequencies within exposure limits of E-H field and power density with SAR limits. 12

13. Thank you for your attention!
Q & A.

14. Reference
[1] WHO, International EMF project ( 14