US 7,321,284 B2
Miniature thin-film bandpass filter
Qiang Richard Chen, Phoenix, Ariz. (US); and Hajime Kuwajima, Tokyo (Japan)
Assigned to TDK Corporation, Tokyo (Japan)
Filed on Jan. 31, 2006, as Appl. No. 11/345,428.
Prior Publication US 2007/0176727 A1, Aug. 02, 2007
Int. Cl. H01F 5/00 (2006.01); H03H 7/00 (2006.01)
U.S. Cl. 336—200  [336/232; 336/223; 333/175] 24 Claims
OG exemplary drawing
 
1. A thin-film bandpass filter comprising:
at least two thin-film layers;
a first resonant circuit including a first inductor; and
a second resonant circuit including a second inductor;
wherein the first inductor comprises a coil having a counter-clockwise rotation positioned in two or more of the at least two thin-film layers;
wherein the second inductor comprises a coil having a clockwise rotation positioned in two or more of the at least two thin-film layers; and
wherein the first inductor is coupled to the second inductor in at least one of the at least two thin-film layers when the bandpass filter is energized.