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'[EE] xmit data from inside the body'
2006\12\23@230411 by James Newtons Massmind

face picon face
So... Here's a fun one for the RF people over the holiday.

We need to xmit data from a logger INSIDE a body over a range of a few feet.

And it has to be micro power.

And it has to be faster than 56Kb.

Has anyone done it?

Has anyone tested the fall off of RF from inside a body as frequency
increases?

Has anyone any idea how you go about figuring out what frequency to use?

Has anyone any idea how to setup a test to see find out how the signal falls
off as the frequency increases?

---
James.


2006\12\23@232932 by Sergey Dryga

face picon face
James Newtons Massmind <jamesnewton <at> massmind.org> writes:

>
> So... Here's a fun one for the RF people over the holiday.
>
> We need to xmit data from a logger INSIDE a body over a range of a few feet.
>
> And it has to be micro power.
>
> And it has to be faster than 56Kb.
>
> Has anyone done it?
>
<SNIP>

There is a pill-camera that one can swallow and then see video as it goes
through intestinese.  Not sure about power and distance, but at least should be
faster than 56Kb.

Sergey Dryga



2006\12\24@003357 by Herbert Graf

flavicon
face
On Sun, 2006-12-24 at 04:29 +0000, Sergey Dryga wrote:
> There is a pill-camera that one can swallow and then see video as it goes
> through intestinese.  Not sure about power and distance, but at least should be
> faster than 56Kb.

The one I've seen I believe actually records images at certain intervals
(say one a second) and that data is then downloaded from the pill when
it is "ejected"...

TTYL

2006\12\24@015441 by Jinx

face picon face
> We need to xmit data from a logger INSIDE a body over a range
> of a few feet

Can you have an aerial sticking out.....somewhere ? Didn't think so

> Has anyone any idea how to setup a test to see find out how the
> signal falls off as the frequency increases?

What if you attach the transmitter to your belt and then give
someone a great big hug (as good an excuse as any). The
signal would have to pass through 1/2 (measured at the side)
or 1 body (measured from the back)

One other alternative is to attach a thread to it and swallow

There is another way (think stuffing a turkey), but nobody wants
to be doing that on holiday

2006\12\24@054330 by Peter P.

picon face
Use a magnetic antenna (coil+core) and low frequency (125kHz etc).

To check for attenuation use a sturdy garbage can or plastic drum filled with
water. Body attenuation is nearly the same as saline solution (~= ocean sea
water) for low frequency RF.

Peter P.


2006\12\24@105326 by Vasile Surducan

face picon face
Not exactly what you want but I think is good for the ideea:


"Several hi-tech companies including HP in the US and Nokia in
Finland, are working on a "skin conductance network" which will allow
people to exchange electronic messages, for example, a greeting card
or document, by shaking hands. The actual document is stored on the
mobile phone and is transmitted via electrodes from body to body.
I am researching this story now and will be writing more about it
later.

NASA is also interested in this techniques...consider the
constraints of present-day telemedicine in space...so bionic
headphones are only part of the story!



Invention: Body-wired headphones
> > 15:40 27 November 2006
> > NewScientist.com news service
> > Barry Fox
> >  Body-wired headphones
> > Sony's Tokyo research lab has found a way to connect headphones to portable music and video players without the need for fiddly wiring.
They simply feed an audio signal straight through the listener's body.
Existing wireless headphones use Bluetooth radio, but this means
pairing two devices beforehand and is prone to interference from other
equipment. Another approach – infra-red – relies on line-of-sight,
which is rarely practical.
The new system uses the listener's body as a capacitor that carries a
tiny electrostatic charge. A music or video player sends a fluctuating
signal to a conductive cloth pad – such as a wrist band – and this
slightly charges the wearer's body. A pair of conductive ear pads in
the headphones pick-up the signal and rapidly convert it back into
sound.
Just a few millionths of an amp flow through the wearer's body, so
there should be no nasty tingling effect. To convert the small charge
into good quality audio, Sony uses a high frequency signal, which is
digitally switched to carry data at 48 kilobytes per second. This is
enough to deliver good quality, body-rocking stereo, the company says.

Read the full body-wired headphones patent application at uspto:

United States Patent Application 20060252371
Kind Code  A1

Yanagida; Toshiharu  November 9, 2006

> > Human body communication system and communication device
> > Abstract:
Disclosed herein is a human body communication system for
communicating data via an electric field formed by intervention of a
human body, the human body communication system including: a
transmitter for generating the electric field by transmitting a
potential difference signal corresponding to transmission data from a
transmitting electrode; and a receiver for receiving the data by
reading the potential difference signal in the electric field by a
receiving electrode; wherein the transmitter and the receiver use the
potential difference signal in a frequency band such that a
quasi-electrostatic field formed within the human body is dominant
over a radiation field formed outside the human body when the
transmitting electrode and the receiving electrode are each disposed
in very close vicinity to the human body.

Claim:
1. A human body communication system for communicating data via an
electric field formed by intervention of a human body, said human body
communication system comprising: a transmitter for generating said
electric field by transmitting a potential difference signal
corresponding to transmission data from a transmitting electrode; and
a receiver for receiving the data by reading the potential difference
signal in said electric field by a receiving electrode;
wherein said transmitter and said receiver use the potential
difference signal in a frequency band such that a quasi- electrostatic
field formed within the human body is dominant over a radiation field
formed outside the human body when said transmitting electrode and
said receiving electrode are each disposed in very close vicinity to
the human body.


On 12/23/06, James Newtons Massmind <spam_OUTjamesnewtonTakeThisOuTspammassmind.org> wrote:
{Quote hidden}

>

2006\12\24@123121 by Peter P.

picon face
Vasile Surducan <piclist9 <at> gmail.com> writes:

> Not exactly what you want but I think is good for the ideea:
>
> "Several hi-tech companies including HP in the US and Nokia in
> Finland, are working on a "skin conductance network" which will allow
> people to exchange electronic messages, for example, a greeting card
> or document, by shaking hands. The actual document is stored on the
> mobile phone and is transmitted via electrodes from body to body.
> I am researching this story now and will be writing more about it
> later.

Do the several hi-tech companies include the MIT and IBM ? Because these seem to
have a little head start (we are in 2007 - almost - the article is from 1998):

 http://www.designnews.com/article/CA86072.html

Peter P.

2006\12\24@154802 by Russell McMahon

face
flavicon
face
> So... Here's a fun one for the RF people over the holiday.
> We need to xmit data from a logger INSIDE a body over a range of a
> few feet.
> And it has to be micro power.
> And it has to be faster than 56Kb.

Data !
More data.
Must have data!
To deal with your data :-)

How fast minimum?

How much data  / What duty cycle?
(eg 112 kbps continuous or 10% bursts of 100 bits or ...)

How deep inside?

How much range? Does orientaton affect this?
Add this answer to next question's answer.

Cooperative target or passive?
(target comes to receiver / target orientates to receiver / target
doesn't know receiver location / target essentially doesn't know
receiver/transmitter exist/ ...)

Lifetime?
(Hours / days / months / indefinite?)

Can it be powered by remote powering?

What known regulatory issues?
(Person / animal / cadaver / ...?)

Target actve/passing by/stationary/area restricted/ ... .

RF?
(Capacitive, inductive, near field, optical, ...)
(Having the whole 'body' inside an inductive powering loop could work
very well but may not be permissible in your application.


If you want Russell to see this answer you'll need to include a line
with "::" in it (quotes optional). Which could be this line. Or send a
copy to him directly.




       Russell



2006\12\24@192008 by Peter P.

picon face
Peter P. <plpeter2006 <at> yahoo.com> writes:

> To check for attenuation use a sturdy garbage can or plastic drum filled with
> water. Body attenuation is nearly the same as saline solution (~= ocean sea
> water) for low frequency RF.

While the attenuation is about the same the composition of saline and ocean
water is not the same at all. I omitted this. Ocean ~= 35g/l salt and saline ~=
9g/l salt.

Peter




2006\12\25@163048 by Tachyon

picon face
AFAIR, the pill camera records to solid state storage for later
retrieval. No transmitter.

Anyway Sergey, I think you might want to consider lower frequencies
(i.e. MHz not GHz).
Find one of the small data modules for micro-controllers and give it a
test run transmitting from inside a pig carcass.
Plus you can have a barbecue later and eat the test rig.

Here's a few things to get you started. To search yourself, I'd use the
terms telemetry and miniature.

http://www.melexis.com/ProdMain.aspx?nID=569
http://www.telonics.com/literature/chp/chp.html


Sergey Dryga wrote:
{Quote hidden}

2006\12\25@163536 by Tachyon

picon face
You might also try these guys...
http://www.datasci.com/products/implantable_telemetry/transmitters.asp

James Newtons Massmind wrote:
{Quote hidden}

2006\12\25@173846 by Denny Esterline

picon face
> AFAIR, the pill camera records to solid state storage for later
> retrieval. No transmitter.
>

http://www.centracare.com/sch/centers/digestive/digest_camera_feature.html

2006\12\25@181300 by Xiaofan Chen

face picon face
On 12/26/06, Denny Esterline <.....firmwareKILLspamspam@spam@tds.net> wrote:
> > AFAIR, the pill camera records to solid state storage for later
> > retrieval. No transmitter.
>
> http://www.centracare.com/sch/centers/digestive/digest_camera_feature.html
>

Nice. I just talked to my wift (she used to be a doctor) and she told
me the main problem is how to control the position of the pill.

2006\12\25@182135 by Xiaofan Chen

face picon face
On 12/26/06, Xiaofan Chen <xiaofancspamKILLspamgmail.com> wrote:
> >
> > www.centracare.com/sch/centers/digestive/digest_camera_feature.html
> >
>
> Nice. I just talked to my wift (she used to be a doctor) and she told
> me the main problem is how to control the position of the pill.
>

By the way, it might be more difficult to transmit the power to charge
the internal battery than transmitting data.

6 years ago, I was in a research lab and one student was doing
such research -- transcutaneous planar transformer. The power
achieved was quite limited at that time.
ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1330040

2006\12\25@182503 by Xiaofan Chen

face picon face
On 12/26/06, Xiaofan Chen <.....xiaofancKILLspamspam.....gmail.com> wrote:
>
> By the way, it might be more difficult to transmit the power to charge
> the internal battery than transmitting data.
>
> 6 years ago, I was in a research lab and one student was doing
> such research -- transcutaneous planar transformer. The power
> achieved was quite limited at that time.
> http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1330040
>

Take note the 20W achieved is from simulation (Ansoft Maxwell
to extract the transformer model and Saber/PSpice for circuit
simulation). I believe the achieved power is much less than that.

2006\12\27@002505 by James Newtons Massmind

face picon face


> "Several hi-tech companies including HP in the US and Nokia
> in Finland, are working on a "skin conductance network" which
> will allow people to exchange electronic messages, for
> example, a greeting card or document, by shaking hands. The
> actual document is stored on the mobile phone and is
> transmitted via electrodes from body to body.
> I am researching this story now and will be writing more
> about it later.
>

An absolutely fascinating application, but I believe, after reading
everything I could find about it, that it depends on the surface of the skin
acting as a capacitor and would not function from inside the body to the
outside. Also the speed of the prototype is 2400b although later
developments have increased the speed, as noted.

http://www.almaden.ibm.com/cs/user/pan/pan.html

However, that paper pointed me to a related study E. Richley and L. Butcher,
"Wireless Communications Using Near Field Coupling", U.S. Patent No.
5,437,057 (issued July 25, 1995).

http://www.research.ibm.com/journal/sj/384/zimmerman.pdf

Magnetic field. Richley has implemented a PAN for Weiser's ubiquitous
computers using magnetic fields. The quadratic attenuation of magnetic field
with distance allows the creation of picocells, 6 cubicmeters per base
station, allowing spatial allocation of bandwidth. The system uses a 5 MHz
(megahertz) carrier to achieve 240 Kbps (kilobits per second) and consumes
only 10 milliwatts power.7 Magnetic field is unimpeded by bodies, so human
shielding is not an issue.

<patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2F
netahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2
F5437057>

http://tinyurl.com/y6h6fn This includes some schematics and information on
how to wind the coils.

There is also a patent (#6,893,395) for "Method and apparatus for data
transmission between an electromedical implant and an external apparatus"

http://tinyurl.com/yza2s9


Good stuff!

---
James.


2006\12\27@010613 by Russell McMahon

face
flavicon
face
I am named as inventor in a US patent (assigned to others) about
1988-1989 (I can dig up details) which involved substantial inductive
power transfer to remote units AND signalling across the system using
the power transfer media to and from multiple remote units. So, my
previous questions were somewhat pertinent. Worked quite well. I was
transferring several watts per unit with 10's of units.

I still have the 100m power loop running around my house :-)




       Russell


{Quote hidden}

2006\12\27@135753 by Peter P.

picon face
A H field radiator at 5MHz (60 meters wavelength) should be attenuated by the
salt water in the body as much or as little as any other RF. Only low frequency
(tens to hundreds of kHz) will be relatively unattenuated. I used to work in
tuning up very sensitive RF receivers and I regularly used my hand to shield
successive IF stages while checking the specan picture (the hand replaced the
lid - almost - and saved time).

However it should be possible to overcome this with sufficient transmitter
power. By this I mean using milliwatts instead of microwatts.

It would be good to know how long it has to work. That will give you a power
budget and implicitly the power you have to work with. After that you can decide
on how best to use that. F.ex. it may be necessary to use a storage capacitor
and use burst transmission so there is enough power to get the signal out if the
power budget is very tight, especially if the frequency is low and you cannot
use a large antenna. I happen to know that a ferrite bar about 1in dia. and
1/10in thick wound and tuned to 125kHz will transmit voice (~=5kHz == 5kbit/sec)
) reliably over a meter or so when powered with about 25mW (class A end stage
but MBFM) carrier. The distance is greater is using a loop as receiver. The
device is orientation sensitive. This can be alleviated by using 2 loops.

Peter P.

2006\12\27@150337 by gacrowell

flavicon
face
Here's the pillcam someone mentioned:
www.givenimaging.com/Cultures/en-US/Given/English/Products/ESO_CE
/

It does transmit the images... but notice that the sensors are in
contact with the body.

GC

> {Original Message removed}

2006\12\27@164653 by Christopher Cole

flavicon
face
On Sat, Dec 23, 2006 at 08:03:58PM -0800, James Newtons Massmind wrote:
> We need to xmit data from a logger INSIDE a body over a range of a few feet.
> And it has to be micro power.  And it has to be faster than 56Kb.

If you can place your antenna as close to the surface of the skin as possible, then you will have no problem.

> Has anyone done it?

Yes, I have designed an rf telemetry system for an implant located deep within the body.  It is very
challenging, as I have encountered around 30 dB of attenuation at 403 MHz through 3-4" of tissue.

> Has anyone tested the fall off of RF from inside a body as frequency increases?

I have not performed such a test myself; I have used the MICS band (402-405 MHz), and also ~100kHz.  Lower
frequencies result in a larger depth of penetration.  This is because as the carrier frequency increases, more
power is lost due to the lossy dielectric (wet tissue), which results in dielectric heating of the tissue.
However, at a lower carrier frequency, more power is required by the telemetry system as the bandwidth
decreases with lower frequency (transmissions will take longer for the same amount of data to be sent).

> Has anyone any idea how you go about figuring out what frequency to use?

Ragarding depth of penetration: The lower the frequency, the better... while keeping in compliance with EMC
regulations.  For medical use, your choices are: MICS, WMTS, and ISM.

wireless.fcc.gov/services/index.htm?job=service_home&id=medical_implant
http://wireless.fcc.gov/services/index.htm?job=service_home&id=wireless_medical_telemetry

MICS is intended for implants, and WMTS is intended for external medical telemetry systems (not implanted).  
ISM is for general industrial, scientific, and medical use, but is not as 'safe' as MICS or WMTS as far as
interference goes.  In the US, the FDA wants medical device manufacturers to stay away from ISM in future
medical devices:

http://www.fda.gov/cdrh/safety/emimts.html
http://www.fda.gov/cdrh/emc/index.html

A couple of interesting research documents on the subject of implantable telemetry:
www.speag.com/en/tcad/publications/Johannsson2004.pdf
http://www.ee.qub.ac.uk/radio/GR_M82288_01.pdf
http://www.nanomedicine.com/NMI/6.4.2.htm

DO NOT depend solely on the results of phantom solution tests.  I got MUCH HIGHER signal losses using real
tissue than I did using phantoms at 402-405 MHz.  This is probably due to the fact that in real tissue, there
are many layers of varying permittivity and conductivity creating interfaces of mismatched impedance, resulting
in signal reflection and scattering.  You will not get this in a water/sugar/salt phantom solution.

Regarding the PillCam, it uses a Zarlink implantable transceiver, specifically designed for the MICS band:
news.zarlink.com/archive/2005/Oct/06/Oct6-GivensPillCam-English.htm.en
http://products.zarlink.com/product_portlets/zl70100.htm

Take care,
-Chris

--
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