IX) Telemetry Flashcards
What are the main component for a wireless system ?
External controler on the skin and the implanted device connected to neural interfaces
What are the two requirements for wireless systems ?
Shall deliver energy supply for the iplant electronics for recording or stimulation
Shall transmit data to and from the implant
What are the objective surrounding the creation of a wireless system ?
Create a magnetic field, transmit and receiveenergy via this magnetic field
What are the laws of maxwell ?
a complete description of electrical and magnetic fields and current flow.
What is “B”
the magnetic induction, it is when the current flow (I) through a straight conductor leads to magnetic induction (B) in dependance of a certain distance.
What is the role of the coil in magnetic induction ?
It is an helical wound conductor. It creates an homogeneous fild that is dependent on density of turns (n) and current (I)
how to calcul the density of turns (n)
n= N/d
N is the number of turns and D the lentght of coil.
What is given as a relation of the magnetic field (H) ad the magnetic induction (B) ?
it is “mu”, or pemeability : B= mu x H
How does magnetic field is calculated ?
it is calculated for a current flow through a straight conductor (H= I / (2 x pi x a))
What is defined as a short coil ?
A coil that the thickness is much smaller than its radius
What is the magnetic flux ?
It is a measure that tells how many magnetic field lines (Bs) cross a given area A.
magneticflux = BxA
It is taken to visualize how field lines cross the space between two transmission coils.
What is the magnetic potential ?
it is for linear conductive loops. It sums up the magnetic flux of N loops ithin a coil of an area A
(= N x mu x H x A)
What is the idea behind the faraday’s law of induction ?
If Magnetic field change iver time, it changes voltage.
We need a temporally changing current in another conductor to induce the changing magnetic induction.
What is the property of a coil ?
It creates inductance
What is the inductance ?
It describes a relation between current through conudctor and magnetic flux through a single loop.
L = (NxmuxHxA)/I
How to calculate the inductance of a loop ?
L = N(squared) x mu0 x r x ln(D/dLeiter)
D/dLeither «_space;0,001
What does the mutual inductance represents ?
It describes the coupling of two electric circuits via a magnetic iels. It is a basic measure for inductive energy and data transmission (how two coils influence eachothers) 221
What is the coefficient of coupling ?
The coefficient of coupling k is a qualitative
measure independent from geometric dimensions
• It is a relation between the mutual inductance and
the inductances of the coils in the primary and
secondary circuit
• Inductively coupled systems: k in the % range
What is the role of the external coil ?
To induce power and send
data to the implant unit
wirelessly using magnetic
induction
What is the role of the internal coil ?
• To collect data and received power from the implant unit • To send data from to implant to the external coil
what is the role of the external part of a resonant circuit ?
- series resonance
- maximize current to drive coil
What is a resonant circuit ?
A circuit that consist of a capacitor and an inductor connected together.
what is the role of the internal part of a resonant circuit ?
parallel resonance
- maximize voltage to
drive circuit
what is the formula to calcul magnetic induction of a coil ?
mu0 x current (I) x density of turn (n)
dencity of turn = number of turns / thrickness of the coil.
What is the quality factor ?
It describes the selectivity of a resonant circuit (serial resoniace vs parallalel resonance)
Give the calculation ofr hte serial resonance and the one for parallel resonance.
serial : energy stored in conductor on energy turned to heat during 1 period
Q= 1/R(squaredrootofL/C)
parallel : energy stored in capacitor on energy turned to heat during 1 period
R(squarerootofC/L)
Where can we find the right frequency to chose ?
International telecommunication union
Were to look at the specific absorbtion rate ?
International commission on non ionizing radiation protection (ICNIRP)
What the classification of primary coil driver ?
classification of amplifiers and drivers for ertain caracteristics.
Describe the D class driver.
Swiching amplifier
two mos fet (transitors)
ideal R is 0 but in reality there is a loss due to switches
Describe the E class driver
switching amplifier
1 transitor
ideal source voltage is 0 if FET switches
Site the 3 mains type of data codes.
Amplitude shift keying
phase shift keying
frquency shift keying,
load shift keing
