Compact tunable dual band stop filter
View Patent ↗Various exemplary embodiments include a technique for tuning a filter to have two stop bands. This technique may involve combination of signals from a plurality of high-band notch resonators and low-band notch resonators. Loop wires may couple both high-band and low-band notch resonators to a central conductor, thereby enabling the central conductor to transmit a signal having dual stop bands.
1. A tuner for a band stop filter, said tuner comprising:
a coupling element that combines signals from a high-band notch resonator and a low-band notch resonator to produce a filtered signal that has dual stop bands disposed symmetrically on either side of a central frequency; and
a central conductor that receives said filtered signal from said coupling element, wherein said coupling element has a length equal to an integral multiple of a quarter wavelength of said central frequency and said coupling element is soldered to be substantially perpendicular to said central conductor.
2. The tuner of claim 1 , wherein said central conductor is a transmission line.
3. The tuner of claim 1 , wherein said central conductor is a stripline.
4. The tuner of claim 1 , wherein said central conductor is a coaxial line.
5. The tuner of claim 1 , wherein said central conductor is a microstrip line.
6. The tuner of claim 1 , wherein said coupling element comprises a loop wire, said loop wire extending from said high-band notch resonator to said low-band notch resonator.
7. The tuner of claim 6 , wherein said loop wire extends through a first open slot in a cavity wall of said high-band notch resonator to said central conductor and extends from said central conductor through a second open slot in a cavity wall of said low-band notch resonator.
8. A tunable filter that provides dual stop bands, said filter comprising:
a central conductor disposed along a first axis; and
a plurality of filter elements that encompass said central conductor, each of said filter elements aligned along a respective axis substantially orthogonal to said first axis, each of said filter elements further comprising:
a high-band notch resonator disposed on a first side of said central conductor;
a low-band notch resonator disposed on a second side of said central conductor, said second side being substantially opposite to said first side with respect to said central conductor; and
a coupling element disposed between said high-band notch resonator and said central conductor, disposed between said low-band notch resonator and said central conductor, and soldered so that at least a portion of said coupling element is substantially orthogonal to said central conductor along said respective axis of said filter element, wherein:
said coupling element combines signals from said high-band notch resonator and said low-band notch resonator to produce a filtered signal that has dual stop bands disposed symmetrically on either side of a central frequency, and
said coupling element has a length substantially equal to an integral multiple of a quarter wavelength of said central frequency.
9. The filter of claim 8 , wherein said central conductor is a transmission line.
10. The filter of claim 8 , wherein said central conductor is a stripline.
11. The filter of claim 8 , wherein said central conductor is a coaxial line.
12. The filter of claim 8 , wherein said central conductor is a microstrip line.
13. The filter of claim 8 , wherein said coupling element comprises a loop wire, said loop wire extending from said high-band notch resonator to said low-band notch resonator.
14. The filter of claim 13 , wherein said loop wire extends through a first open slot in a cavity wall of said high-band notch resonator to said central conductor and extends from said central conductor through a second open slot in a cavity wall of said low-band notch resonator.
15. A method of tuning a signal to produce dual stop bands, said method comprising:
using a plurality of high-band notch resonators to produce a first notch in a signal characteristic;
using a plurality of low-band notch resonators to produce a second notch in said signal characteristic;
using a plurality of coupling elements to combine signals from said plurality of high-band notch resonators and said plurality of low-band notch resonators to produce a filtered signal that has dual stop bands disposed symmetrically on either side of a central frequency; and
sending said filtered signal from said coupling elements to a central conductor, wherein each of said coupling elements has a length equal to an integral multiple of a quarter wavelength of said central frequency and each of said coupling elements is soldered to be substantially perpendicular to said central conductor.
16. The method of claim 15 , wherein said central conductor is a transmission line.
17. The method of claim 15 , wherein said central conductor is a stripline.
18. The method of claim 15 , wherein said central conductor is a coaxial line.
19. The method of claim 15 , wherein said central conductor is a microstrip line.
20. The method of claim 15 , wherein each of said coupling elements comprises a loop wire, said loop wire extending from one of said high-band notch resonators through said central conductor to one of said low-band notch resonators.