# Plume – Magnetic Resonant Coupling

Looks like we have a winner.

Today, I started to study the Magnetic Resonant Coupling technology.
First with the schematic of the Razer Hydra.
For the receiver, they use a low noise Precision CMOS Amplifier and a multiplexer to choose one of the three coils.
For the transmitter, they also use a multiplexer and a LOW-VOLTAGE RAIL-TO-RAIL OUTPUT OPERATIONAL AMPLIFIERS but i still don’t know why.
Afterwards, I studied some scientific publications about the subject.

One of the solution to get the position and the orientation is to use the 3 transmitter axes and 3 receiver axes successively.
We will have 9 equations for 6 unknowns. We should be able to solve the system thanks to the following property.
The magnetic field of a typical coil is elongated along the coil axis so that the field strength depends not only on the
distance but also on where around the coil the receiver is placed.

But with this solution will we have to solve the following problems :
-How we will handle the synchronization between the transmitter and the receiver ?
-How we will solve the physics equations ?
-With the symmetry of the magnetic field we will only have the position in a 1/8 of space. We may need an accelerometer.
-We need a 5 meters range but the energy transmitted in the field decreases with 1/r^6 and the WHO (World Health Organization)  say that the magnetic field should be bellow 100 micro Tesla to be harmless.

Olivier

 successively

### 2 comments to Plume – Magnetic Resonant Coupling

• Phh

Rail to Rail means the output can (almost) go from Vdd to Vss.
For the low voltage part, I’m guessing it’s around 1v. If so, then it’s most likely because it then goes into an analog to digital converter, probably a high speed one. If it is the case, take care that those op amps doesn’t have their zero output at 0v (it can’t do negative voltage). (same applies of it’s a DAC)

• oliviert

Ok thanks, this help.