A filter which has a single transmission band extending from a finite lower cutoff frequency greater than zero to a finite upper cutoff frequency. The cutoff frequencies are defined as those points on either side of the center frequency where the amplitude is attenuated by 3dB. At the center frequency, the signal amplitude is not attenuated. [Field of Rotating Machinery Measurement, Monitoring and Analysis, Bentley Nevada Corporation]
Resonant inductive coupling or magnetic phase synchronous coupling is a phenomenon with inductive coupling where the coupling becomes stronger when the "secondary" (load-bearing) side of the loosely coupled coil resonates. A resonant transformer of this type is often used in analog circuitry as a bandpass filter. Resonant inductive coupling is also used in wireless power systems for portable computers, phones, and vehicles. wikipedia
A resonant transformer is a transformer in which one or both windings has a capacitor across it and functions as a tuned circuit. Used at radio frequencies, resonant transformers can function as high Q factor bandpass filters. The transformer windings have either air or ferrite cores and the bandwidth can be adjusted by varying the coupling (mutual inductance). One common form is the IF (intermediate frequency) transformer, used in superheterodyne radio receivers. They are also used in radio transmitters. wikipedia
See Also
Bessel Filter
Butterworth Filter
cavity resonator
Chakra System
Endocrine System
High-Pass Filter
Low-Pass Filter
Sense