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Operating frequency of the Wireless power system in biomedical application

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bhl777

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Hi all, I am curious about the operating frequency of the wireless power transfer system for biomedical applications. Most of the cases for the implantbale electronic devices are using 6.78MHz or 13.56MHz.
I am wondering what is the main issue in using lower operating frequencies, in addition to the coil size.

For example, I have one WPT kit WP3W-RK (https://www.idt.com/products/power-...-power-reference-solution-05w-3w-applications), whose Tx and Rx coils operates at around 180kHz. If the coil size is acceptable for implantable electronics, what are the other problems in using this WPT system for the biomedical applications?

Thank you!
 

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Its more a case of what you are allowed to use, rather than what can work.

Power transmission does radiate power, and operation is confined to the ISM bands, of which there are several. (industrial, scientific, medical).

You can kick up as much noise as you like on those ISM frequencies without ending up in court.
 

Warpspeed said:
Its more a case of what you are allowed to use, rather than what can work.

Power transmission does radiate power, and operation is confined to the ISM bands, of which there are several. (industrial, scientific, medical).

You can kick up as much noise as you like on those ISM frequencies without ending up in court.
Click to expand...

Hi Warpspeed，thank you for your help! Would you teach me another 2 questions if you know?
(1) Does this ISM band limitation only apply to power transfer? Is there any specific limitation to the data transfer? In my application, in addition to the power coil, I also have a data coil by transmitting the sine signal between 1MHz to 5MHz?
(2) do you know how to determine the safety supply voltage/power to the implantbale devices? I heard some words called "Specific Absorption Rate (SAR)", but do not know how to use it to determine the safety related issues. For example, can I say the supply voltage of the implantable devices should be less than xxV? Or the power consumption per unit must be below xxW/cm^2? Would you teach me about this?
 

The ISM bands are a kind of "outlaw band" where nobody can complain about interference.

If you are doing some critical biomedical data transfer and it does not work because somebody else nearby has some kind of high power industrial process operating on the exact same frequency as you, that's just tough luck.

If you start transmitting between 1Mhz and 5Mhz, and you start interfering with licensed commercial radio services. If somebody complains and you are caught, the authorities will deal with you.

And you will be caught, because people like the marine operations centres now have very efficient radio direction finding facilities to locate very brief distress messages from ships for example. They can pinpoint you in minutes if you start to become a real nuisance.

Please understand, the radio spectrum is a very limited resource and you cannot just do anything you want that might greatly disadvantage other users.
 

Warpspeed said:
The ISM bands are a kind of "outlaw band" where nobody can complain about interference.

If you are doing some critical biomedical data transfer and it does not work because somebody else nearby has some kind of high power industrial process operating on the exact same frequency as you, that's just tough luck.

If you start transmitting between 1Mhz and 5Mhz, and you start interfering with licensed commercial radio services. If somebody complains and you are caught, the authorities will deal with you.

And you will be caught, because people like the marine operations centres now have very efficient radio direction finding facilities to locate very brief distress messages from ships for example. They can pinpoint you in minutes if you start to become a real nuisance.

Please understand, the radio spectrum is a very limited resource and you cannot just do anything you want that might greatly disadvantage other users.
Click to expand...

Thank you Warpspeed for your detailed instruction. I have another question about my application.
For conventional data transfer, the data is with a fixed data rate. In my case, the purpose of the data coil is to pass the frequency of the primary coil to the secondary coil. Therefore, what I am doing is to send a sinusoidal signal at the primary coil (say, 1MHz) and try to generate a sinusodail signal at the secondary coil for some post signal processing. Therefore, I am not sure if my case is a real data transfer, or just some "frequncy transmission". Is this also regualated by ISM?
 

A 1Mhz carrier wave will create interference right in the middle of the AM commercial radio band in most countries. If you need an exactly 1Mhz reference frequency at the receive end, just as easy to do it with a very stable 1 Mhz crystal oscillator.

If you need exact frequency locking at both ends, lock to the carrier frequency of some very strong commercial broadcast station that is already there.
 

Warpspeed said:
A 1Mhz carrier wave will create interference right in the middle of the AM commercial radio band in most countries. If you need an exactly 1Mhz reference frequency at the receive end, just as easy to do it with a very stable 1 Mhz crystal oscillator.

If you need exact frequency locking at both ends, lock to the carrier frequency of some very strong commercial broadcast station that is already there.
Click to expand...

Thank you Warpspeed. I do not need exact frequency locking for my sinusoidal signal frequency transfer. My question is related to the ISM regulation, based on your answer to my post. If my WPT use 13.56MHz fixed frequency to my implantable devices, and I use a sinusoidal signal within the range of 1MHz to 5MHz at Tx (say 1.6MHz, 2.2MHZ, 2.8MHz, ....., 4.6MHz). Because we have the control of the frequency at Tx, and this frequency will be exactly transfered to Rx, will it cause any proctical problems as you mentioned in the previous thread due to that fact that it is not within the ISM band?
 

will it cause any proctical problems as you mentioned in the previous thread due to that fact that it is not within the ISM band?
Click to expand...
It need to comply with applicable regulations in your country, e.g. FCC 47 Part 18 or respective ETSI standards.
 
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