wireless power transmission by resonant coupling

[Josephchiang]

Hello everyone, my research topic is wireless power transmitter(WPT) in 13.56MHz.

I know that there are two major ways to achieve the WPT, including inductive coupling and resonant coupling.

Base on my knowledge, resonant coupling could achieve higher efficiency and longer propagation distance than inductive coupling. Is that true? what's the reason?

But after reading lots of paper and material, I am still confused about some points.

The following graph show the schematic of the resonant coupling, Rs and Rr are the resistances and losses in the associated capacitors and inductors. Ls and Lr

are coupled by small coupling coefficient, k, usually below 0.2 .





I don't know why the L-C component is always connected as series at transmitter, but parallel at receiver. what's the advantage of the series-parallel L-C

topology?

How to determine/optimize the value of L-C component to achieve the maximum power coupling?

I only know the resonant frequency is determine by the equation(1/2*pi*(L*C)^0.5).
What's happened if enhance L and decrease C to meet the same resonant frequency in the transmitter?

 

[tony_lth]

Hi, The basic principle is very simple, I guess so.
TX: series resonant have lowest resistance at resonant freq, so max power can be emiitted.
RX: shunt resonant has max resistance at resonant freq, so it act like as a current surce, the load has little effect on the RX L.
For change L and C, you can simulate it, although the resonant freq may be the same, but Q of the resonant is changed also. If I remember correctly.

 

[Josephchiang]

Thanks for your reply

I think your explanation is right,

But how does the Q of the resonant affects the power transmission?

Does the efficiency will be enhanced for higher Q value ?
(I know that the bandwidth is depend on the Q value，but I don't make a decision yet)

So could you give me more information or reference? Thanks a lot

 

[jiripolivka]

To my knowledge the circuit shown is an ordinary band.pass filter, possibly patented in 1910 or so. The Serbian doctorand at Ohio University discovered it in 2010. Now everyone copies what was used as an IF bandpass filter in every radio.
All radio amateurs know that the higher Q, the higher efficiency of transmission. Have you seen the photograph of this "wonder" in action? The coils are .5 meter in diameter and the system transmits 40 W over 50-100 cm distance. Efficiency posibly 30 per cent, means that 70 per cent is lost by radiating to the surrounding space.
I would not see such thing a sucess, it is a shame of engineering.

 

[Josephchiang]

To my knowledge the circuit shown is an ordinary band.pass filter, possibly patented in 1910 or so. The Serbian doctorand at Ohio University discovered it in 2010. Now everyone copies what was used as an IF bandpass filter in every radio.
All radio amateurs know that the higher Q, the higher efficiency of transmission. Have you seen the photograph of this "wonder" in action? The coils are .5 meter in diameter and the system transmits 40 W over 50-100 cm distance. Efficiency posibly 30 per cent, means that 70 per cent is lost by radiating to the surrounding space.
I would not see such thing a sucess, it is a shame of engineering.

The Q value of the R-L-C series connection could be expressed as 2*pi*freq*L/R

The efficiency of power transmission is depend on how high the Q value is.(also depend on the coupling factor)

if I want to optimize the design,have any tips to achieve high Q value of inductance?