Low pass filter incorporating coupled inductors to enhance stop band attenuation
AssigneeCalifornia Micro Devices Corporation
InventorsWenjiang Zeng, Rong Liu, Yupeng Chen, Wang-Chang Albert Gu
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Abstract
The present invention relates to a low pass filter incorporating coupled inductors to enhance stop band attenuation. In one embodiment, the coupled inductors are provided along with various capacitors to provide for superior performance within a smaller surface area of a semiconductor or ceramic integrated device. In a further specific embodiment, the capacitors are formed on an integrated device within an area on which entirely intertwined inductors are formed. In another embodiment, at least one further pair of coupled inductors is included to create additional frequency attenuation notches, as well as a wide stop-band.
Claims28
A filter circuit disposed between an input line, an output line, and a ground line, each of the input line, the output line and the ground line each having a parasitic resistance and a parasitic inductance associated therewith, the filter circuit comprising:
- a first inductor having first coils disposed in series with a first resistor between the input line and the output line, wherein a first node is created between the first inductor and the first resistor;
- a second inductor having second coils and a first capacitor disposed in series between the first node and the ground line, wherein the second coils of the second inductor at least partially overlap with the first coils of the first inductor, thereby coupling the first and second inductors and reducing a surface area occupied by the first and the second inductors;
- and
- a second capacitor disposed between the output line and the ground line;
- wherein the filter circuit has a predetermined stop-band, a predetermined pass-band cutoff frequency, and wherein the first and second inductors and the first and second capacitors steepen a slope of the roll-off and provide a notch at a stop-band frequency to obtain substantial attenuation beyond the cutoff frequency and minimum attenuation below the cutoff frequency.
Dependencies are inferred from the claim text.