We got the initial batch of our custom-designed coils from Chipsen!
- 1300 turns (0.040mm, AWG 46)
- 450Ω D.C. Impedance (Max),
- 20Hz-20kHz flat frequency response
- 9mm diameter, 5mm height.
With the low-Z coils, the frequency response goes way beyond the human hearing range into the ultrasonic range. We band-limit the range to about 160KHz to filter out unwanted high frequency noise.
The coils are vacuum potted with epoxy and individually wrapped with pressure sensitive pickup-coil tape. Each coil sits on its own castellated PCB base. PCB Castellation is a neat trick. The plated half-round vias at the edges make it easy to surface mount the coil assembly into the main PCB.