Filter
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsHiroshi Kushitani, Masayuki Mizuno
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Abstract
Here disclosed is a parallel-resonance type band-pass filter, which is employed for mobile communications equipment such as a mobile phone. According to the filter, each resonator has a single capacitor and serially connected plural inductors both of which are formed on the surface or on an inner layer of a substrate. Electromagnetic coupling between the resonators is established through electromagnetic coupling between at least a pair of inductors—the inductors of the pair belong to respective resonators. The input and the output terminals are coupled with the respective resonators via the capacitor having a properly determined capacitance. With such a simple structure, the filter also can work as an impedance transformer, with the result that the mobile communications equipment will be much smaller.
Claims23
A parallel-resonance type band-pass filter comprising:
- a substrate;
- a first resonator including:
- i) a first capacitor;
- and
- ii) a first plurality of inductors connected to each other in series, both of which are formed on a common surface, or on a common inner layer of the substrate;
- and
- a second resonator including:
- i) a second capacitor;
- and
- ii) a second plurality of inductors connected to each other in series, both of which are formed on the common surface, or on the common inner layer of the substrate,
- wherein electromagnetic coupling between the first resonator and the second resonator is performed by at least electromagnetic coupling between one of the first plurality of inductors and one of the second plurality of inductors, and
- wherein the resonance frequency of the first resonator is derived from a capacitance of the first capacitor and a combined inductance of the respective inductances of the first plurality of inductors.
Dependencies are inferred from the claim text.