Passive filter

Patent metadata

Field	Value
Publication number	US-9257956-B2
Application number	US-201314030357-A
Country	US
Kind code	B2
Filing date	Sep 18, 2013
Priority date	Sep 28, 2012
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A passive filter may include at least one elliptical filter unit and at least one asymmetric rejection filter unit coupled in series with the elliptical filter unit. The at least one asymmetric rejection filter unit may have a frequency response curve that includes a dip with different attenuations on either side, and an overshoot upon exiting the dip at the side with the lower attenuation.

First claim

That which is claimed is:

1. A method of making a passive filter comprising:
providing at least one elliptical filter; and
coupling at least one asymmetric rejection filter in series with the at least one elliptical filter, the at least one asymmetric rejection filter having a frequency response curve including a dip with different attenuations on opposing sides of the dip, and an overshoot upon exiting the dip adjacent the side with a lower attenuation, the overshoot coinciding, in frequency, with, and being adjacent to a top of a slope of a frequency response curve of said at least one elliptical filter.

2. The method of claim 1 , wherein coupling the at least one asymmetric rejection filter comprises coupling at least one high-pass filter.

3. The method of claim 1 , wherein coupling the at least one asymmetric rejection filter comprises:
coupling a resonance capacitor to a first capacitor;
coupling an inductor in parallel with the resonance capacitor; and
coupling a second capacitor in series with the resonance capacitor and the inductor.

4. The method of claim 1 , wherein coupling the at least one asymmetric rejection. filter comprises coupling at least one low-pass asymmetric rejection filter.

5. The method of claim 1 , wherein coupling the at least one asymmetric rejection filter comprises:
coupling a resonance capacitor coupled to a first capacitor;
coupling an inductor in series with the resonance capacitor; and
coupling a second capacitor in parallel with the resonance capacitor and the inductor.

6. The method of claim 1 , wherein providing the at least one elliptical filter comprises providing at least one high-pass elliptical filter.

7. The method of claim 1 , wherein providing the at least one elliptical filter comprises providing at least one elliptical filter by at least:
coupling a resonance capacitor to a capacitor; and
coupling an inductor in series with the resonance capacitor.

8. The method of claim 1 , wherein providing the at least one elliptical filter comprises providing at least one low-pass elliptical filter.

9. The method of claim 1 , wherein providing the at least one elliptical filter comprises providing at least one elliptical filter by at least:
coupling a resonance capacitor coupled to a capacitor; and
coupling an inductor coupled in parallel with the resonance capacitor.

10. A passive filter comprising:
at least one elliptical filter; and
at least one asymmetric rejection filter coupled in series with said at least one elliptical filter and having a frequency response curve including a dip with different attenuations on opposing sides of the dip, and an overshoot upon exiting the dip adjacent to the side with a lower attenuation, the overshoot coinciding, in frequency, with, and being adjacent a top of a slope of a frequency response curve of said at least one elliptical filter.

11. The passive filter of claim 10 , wherein said at least one elliptical filter comprises:
a capacitor;
a resonance capacitor coupled to said capacitor; and
an inductor coupled in parallel with said resonance capacitor.

12. The passive filter of claim 10 , wherein said at least one asymmetric rejection filter comprises at least one high-pass filter.

13. The passive filter of claim 10 , wherein said at least one asymmetric rejection filter comprises:
a first capacitor;
a resonance capacitor coupled to said first capacitor;
an inductor coupled in parallel with said resonance capacitor; and
a second capacitor coupled in series with said resonance capacitor and said inductor.

14. The passive filter of claim 10 , wherein said at least one asymmetric rejection filter comprises at least one low-pass asymmetric rejection filter.

15. The passive filter of claim 10 , wherein said at least one asymmetric rejection filter comprises:
a first capacitor;
a resonance capacitor coupled to said first capacitor;
an inductor coupled in series with said resonance capacitor; and
a second capacitor coupled in parallel with said resonance capacitor and said inductor.

16. The passive filter of claim 10 , wherein said at least one elliptical filter comprises at least one high-pass elliptical filter.

17. The passive filter of claim 10 , wherein said at least one elliptical filter comprises:
a capacitor;
a resonance capacitor coupled to said capacitor; and
an inductor coupled in series with said resonance capacitor.

18. The passive filter of claim 10 , wherein said at least one elliptical filter comprises at least one low-pass elliptical filter.

19. A band-pass filter comprising:
first, second, and third filters coupled in series;
said first filter comprising a high-pass elliptical filter;
said second filter comprising a high-pass asymmetric rejection filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor,
an inductor coupled in parallel with said resonance capacitor, and
a second capacitor coupled in series with said resonance capacitor and said inductor; and

said third filter comprising one of
a low-pass asymmetric rejection filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor,
an inductor coupled in series with said resonance capacitor, and
a second capacitor coupled in parallel with said resonance capacitor and said inductor, and

a low-pass elliptical filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor, and
an inductor coupled in parallel with said resonance capacitor,

said high-pass elliptical filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor, and
an inductor coupled in series with said resonance capacitor.

20. The band-pass filter of claim 19 , wherein said respective inductors comprise corresponding fixed inductors; and wherein said respective first capacitors, said respective second capacitors, and said respective resonance capacitors each comprises a corresponding adjustable capacitor.

21. An integrated circuit (IC) device comprising:
an inductor; and
an IC filter comprising a high-pass elliptical filter, a high-pass asymmetric rejection filter, and at least one of a low-pass asymmetric rejection filter and a low-pass elliptical filter;
said high-pass asymmetric rejection filter comprising
a first capacitor, and
a resonance capacitor coupled to said first capacitor and coupled in parallel with said inductor, and
a second capacitor coupled in series with said resonance capacitor and coupled in series with said inductor,

said low-pass asymmetric rejection filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor and coupled in series with said inductor, and
a second capacitor coupled in parallel with said resonance capacitor and coupled in parallel with said inductor,

said high-pass elliptical filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor and coupled in series with said inductor, and

said low-pass elliptical filter comprising
a first capacitor,
a resonance capacitor coupled to said first capacitor and coupled in parallel with said inductor.

22. The IC device of claim 21 , wherein said inductor comprises a fixed inductor; and wherein said respective first capacitors, said respective second capacitors, and said respective resonance capacitors each comprises a corresponding adjustable capacitor.

23. The IC device of claim 22

Assignees

• St Microelectronics Sa

Inventors

• Ricard Jean-Christophe
• Durand Cedric
• Gianesello Frederic

Classifications

• H03H7/12

  Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency (H03H7/09 takes precedence) · CPC title

• H03H7/463

  Duplexers · CPC title

• H03H7/0161

  Bandpass filters (H03H7/12 takes precedence) · CPC title

• H03H7/1783

  Combined LC in series path · CPC title

• H03H3/00

  Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators · CPC title