This is a design of a quad bifilar coil, meaning that when this design is fabricated on a four-layer printed circuit board (PCB), there will be four 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.
Another experiment to try is to ground the second tap from the end, drive the end tap with a sine wave at the resonant frequency of the remainder of the coil, and then get the amplified benefits of the remainder as in a secondary coil of a transformer.
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:
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).
In this section, we will document emperically-measured resistances and resonant frequencies of fabricated coils as they become available.
Coil 1 consists of:
PCB thickness = 1.6mm
trace width = 0.15mm (6 mils)
gap width = 0.15mm
number of coils per spiral = 100
| From point | To point | DC resistance (Ω) | Resonant Frequency |
|---|---|---|---|
| TR | BR/TL | 105.3 ? | |
| BR/TL | BL/3L | 105.4 ? | |
| BL/3L | 2R/3R | 441 | |
| 2R/3R | 2L | 442 | |
| TR | 2L | 989.7 | ~25kHz |
Enjoy!
Copyright 2019 Glenn M. Lewis. All Rights Reserved.
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