Low-loss tunable radio frequency filter

Patent metadata

Field	Value
Publication number	US-10027310-B2
Application number	US-201715694653-A
Country	US
Kind code	B2
Filing date	Sep 1, 2017
Priority date	Nov 17, 2006
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

First claim

What is claimed is:

1. A radio frequency (RF) filter, comprising:
a signal transmission path having an input and an output;
a plurality of resonant elements disposed along the signal transmission path between the input and the output; and
a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and at least one sub-band respectively between at least one adjacent pair of the transmission zeroes, wherein the non-resonant elements comprise at least one variable non-resonant element for selectively introducing at least one reflection zero within the stop band to create a pass band in one of the at least one sub-bands.

2. The RF filter of claim 1 , wherein the at least one sub-band comprises a plurality of sub-bands.

3. The RF filter of claim 2 , wherein the at least one variable non-resonant element is for displacing the at least one reflection zero along the stop band to create the pass band within selected ones of the sub-bands.

4. The RF filter of claim 3 , wherein the pass band has substantially different bandwidths within the selected sub-bands.

5. The RF filter of claim 2 , wherein the at least one variable non-resonant element is for displacing at least another reflection zero within the stop band to create another pass band within another one of the sub-bands.

6. The RF filter of claim 1 , wherein the at least one variable non-resonant element is for displacing the at least one reflection zero along the stop band to selectively move the pass band within the one sub-band.

7. The RF filter of claim 1 , wherein the at least one reflection zero comprises a plurality of reflection zeroes.

8. The RF filter of claim 1 , wherein the at least one variable non-resonant element comprises a plurality of variable non-resonant elements.

9. The RF filter of claim 1 , further comprising at least one tuning element configured for modifying the frequency of at least one of the resonant elements.

10. The RF filter of claim 9 , wherein the at least one tuning element is configured for modifying the frequency of the at least one resonant element to displace the transmission zero corresponding to each frequency of the at least one resonant element along the stop band relative to the at least one reflection zero.

11. The RF filter of claim 9 , wherein the at least one tuning element comprises a plurality of tuning elements configured for modifying the frequencies of the resonant elements to simultaneously displace the stop band with the pass band along a frequency range.

12. The RF filter of claim 1 , wherein the at least one variable non-resonant element has an adjustable susceptance.

13. The RF filter of claim 1 , wherein the at least one variable non-resonant element comprises at least one of a variable capacitor, a loss-loss switch, a varactor, and a switched capacitor.

14. The RF filter of claim 1 , wherein each of the resonant elements comprises a thin-film lumped element structure.

15. The RF filter of claim 14 , wherein the thin-film lumped element structure comprises a high temperature superconductor (HTS).

16. The RF filter of claim 1 , further comprising a controller configured for generating electrical signals to adjust the at least one variable non-resonant element.

17. A radio frequency (RF) filter, comprising:
a signal transmission path having an input and an output;
a plurality of resonant elements disposed along the signal transmission path between the input and the output;
a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a plurality of sub-bands between a plurality of adjacent pairs of the transmission zeroes; and
an electrical controller configured for varying at least one of the non-resonant elements to introduce at least one reflection zero along the stop band to create a pass band within selected ones of the sub-bands.

18. The RF filter of claim 17 , wherein the pass band has substantially different bandwidths within the selected sub-bands.

19. The RF filter of claim 17 , wherein the electrical controller is configured for varying the at least one non-resonant element to displace the at least one reflection zero along the stop band to create another pass band within another one of the sub-bands.

20. The RF filter of claim 17 , wherein the electrical controller is configured for varying the at least one non-resonant element to displace the at least one reflection zero along the stop band to selectively move the pass band within each of the selected sub-bands.

21. The RF filter of claim 17 , wherein the at least one reflection zero comprises a plurality of reflection zeroes.

22. The RF filter of claim 17 , wherein the at least one non-resonant element comprises at least two non-resonant elements.

23. The RF filter of claim 17 , further comprising a plurality of tuning elements configured for modifying the frequencies of the resonant elements to independently displace the respective transmission zeroes relative to the at least one reflection zero.

24. The RF filter of claim 17 , wherein the electrical controller is configured for adjusting a susceptance of the at least one non-resonant element.

25. The RF filter of claim 17 , wherein the at least one non-resonant element comprises at least one of a variable capacitor, loss-loss switch, a varactor, and a switched capacitor.

26. The RF filter of claim 17 , wherein each of the resonant elements comprises a thin-film lumped element structure.

27. The RF filter of claim 17 , further comprising a controller configured for generating electrical signals to adjust the at least one variable non-resonant element.

28. The RF filter of claim 17 , wherein the thin-film lumped element structure comprises a high temperature superconductor (HTS).

29. A radio frequency (RF) filter, comprising:
a signal transmission path having an input and an output;
a plurality of resonant elements disposed along the signal transmission path between the input and the output; and
a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and at least one sub-band respectively between at least one adjacent pair of the transmission zeroes, wherein the non-resonant elements have susceptance values that locate at least one reflection zero within the stop band to create a pass band in one of the at least one sub-bands.

30. The RF filter of claim 29 , wherein the at least one sub-band comprises a plurality of sub-bands.

31. The RF filter of claim 29 , wherein the at least one reflection zero comprises a plurality of reflection zeroes.

32. The RF filter of claim 29 , wherein each of the resonant elements comprises a thin-film lumped element structure.

33. The RF filter of claim 32 , wherein the thin-film lumped element structure comprises a high temperature superconductor (HTS).

34. A radio frequency (RF) filter, comprising:
a signal transmission path having an input and an output

Assignees

• Resonant Inc

Inventors

• Tsuzuki Genichi
• Willemsen Balam A

Classifications

• H03H2009/02204

  operating on an additional circuit element, e.g. applying a tuning DC voltage to a passive circuit element connected to the resonator · CPC title

• H03H2007/013

  Notch or bandstop filters · CPC title

• H03H9/171

  implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type · CPC title

• H03H2210/033

  Continuous · CPC title

• H03H7/12 Primary

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