dual-bifilar-coil

Dual (2-layer) bifilar coil

This is a design of a dual bifilar coil, meaning that when this design is fabricated on a two-layer printed circuit board (PCB), there will be two bifilar coils wired in series, one bifilar coil per layer.

The theory is that when you drive the coil with a sine wave at its resonant frequency, it can transfer power at its greatest efficiency.

The beauty of this design is that there are multiple tap points along the length of the coils that result in different resonant frequencies due to the varying reactance. Thus, if your electronics drive the coils properly from the different tap points, this single coil design can potentially support the optimal energy transfer of multiple frequencies.

How it is wired

All coils are concentric and wind in the same direction. Therefore the magnetic field from each coil section combines uniformly with the other coils resulting in a stronger, cohesive field.

Here is a diagram showing how it is wired:

This shows the various layers on a small (n=20) coil to highlight the wiring and various layers of the PCB:

Parametric design

In this design, coils can be created with varying trace widths, gaps between traces, and number of spirals per coil. As a result, this parametric design could theoretically be used for coils of any manufacturable size (from microscopic on up).

Example coils

In this section, we will document emperically-measured resistances and resonant frequencies of fabricated coils as they become available.

Coil 1

Coil 1 consists of:

PCB thickness = 1.6mm
trace width = 0.15mm (6 mils)
gap width = 0.15mm
number of coils per spiral = 100

Enjoy!

License

Copyright 2019 Glenn M. Lewis. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.