High frequency filter with blocking circuit coupling

• US 20080157899A1
• Filed: 12/27/2006
• Published: 07/03/2008
• Est. Priority Date: 12/27/2006
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Kathrein-Werke KG. (Kathrein SE)
• Inventors: Weitzenberger, Wilhelm
• Granted Patent: US 7,777,593 B2
• Time in Patent Office: Days
• US Class Current: 333/134
• CPC Class Codes: H01P 1/2053 the coaxial cavity resonators being disposed parall to each other

Abstract

An improved high frequency filter displays the following features: the high frequency filter displays transmission behavior with a coupling impedance resonance having at least one blocking point at a frequency, the blocking point at the frequency being adjustable by presetting and/or preselecting a defined capacitive and inductive coupling between two coaxial resonators, one immediately following the other on a signal path.

Claims

1. A high frequency filter, for a duplex filter comprising:

a plurality of electromagnetically coupled coaxial resonators, wherein the high frequency filter displays transmission behavior with a coupling impedance resonance having at least one blocking point at a frequency (f_s),

the blocking point at the frequency (f_s) being adjustable by presetting and/or preselecting a defined capacitive and inductive coupling between two coaxial resonators one immediately following the other on a signal path.

2. The high frequency filter as claimed in claim 1, wherein the at least one coupling capacitance and the at least one coupling inductance are selected in such a way that the at least one blocking point is at a frequency (f_s) which is no further than ±

50% from the center frequency of the band-pass filter.

3. The high frequency filter as claimed in claim 1, wherein n-coaxial resonators are cross-coupled to one another on a signal path, more than one and less than n-1 blocking circuit couplings being provided.

4. The high frequency filter as claimed in claim 1, wherein the high frequency filter comprises at least two band-pass filters, the at least one pair, per band-pass filter, of adjacent coaxial resonators, one immediately following the other in the signal path, having a blocking circuit coupling at a frequency (f_s) in such a way that the blocking point is located outside the pass range of the respective band-pass filter, at least one blocking point preferably being located in the pass range of the respective other band-pass filter.

5. The high frequency filter as claimed in claim 4, wherein the at least two band-pass filters are part of a duplex filter.

6. The high frequency filter as claimed in claim 4, wherein the at least one blocking point or preferably the plurality of blocking points is or are located, viewed from the center frequency of a band-pass filter, no further than five times the duplex separation, i.e. the center frequency separation of the two band-pass filters of a duplex filter, preferably less than four times, three times, twice or, in particular, one times the duplex separation.

7. The high frequency filter as claimed in claim 1, wherein a plurality of pairs of coaxial resonators, one immediately following the other on a signal path, are provided with defined frequencies (f_s1, f_s2, f_s3, . . . ), thus generating a plurality of defined blocking circuit couplings, the blocking frequencies being at least partially different or at least partially identical.

8. The high frequency filter as claimed in claim 7, wherein the capacitive and the inductive coupling can be preset in such a way that the at least one frequency (f_s) of the associated blocking circuit coupling has a lower frequency or a higher frequency than the band-pass filter.

9. The high frequency filter as claimed in claim 1, wherein the degree of capacitive cross-coupling between two adjacent internal conductors of two adjacent coaxial resonators can be preset by a radially protruding internal conductor extension toward each coupled adjacent internal conductor and thus by corresponding presetting of the clearance between two corresponding internal conductors or associated internal conductor extensions.

10. The high frequency filter as claimed in claim 9, wherein the internal conductor extension is formed transversely and preferably perpendicularly to the axial extent of an associated internal conductor in the upper end region of the internal conductor.

11. The high frequency filter as claimed in claim 9, wherein the internal conductor is formed with a corresponding internal conductor extension in the manner of an inverted L.

12. The high frequency filter as claimed in claim 10, wherein one internal conductor is cross-coupled to a preceding and subsequent coaxial resonator in the signal path, thus generating two blocking circuit couplings, for which purpose the associated internal conductor is provided, in the direction of both the preceding and the subsequent cross-coupled coaxial resonator, with an internal conductor extension.

13. The high frequency filter as claimed in claim 12, wherein the internal conductor forms a T with the associated internal conductor extension.

14. The high frequency filter as claimed in claim 1, wherein there is provided between two internal conductors, preferably in the upper free end region thereof, an electrically conductive bridge member which shortens the free stretch between the two internal conductors and is set apart from the respective internal conductors or the internal conductor extensions formed at these locations, thus allowing a presettable total distance, consisting of the two clearances between the bridge member and the adjoining internal conductors or the associated internal conductor extensions, to be preset, as a result of which the capacitive coupling can be adjusted.

15. The high frequency filter as claimed in claim 1, wherein from the opposing side of the housing of the coaxial resonator, a coupling pin protrudes between two adjacent coaxial resonators into the interior of the resonator for varied adjustment of the coupling capacitance.

16. The high frequency filter as claimed in claim 1, wherein the inductive coupling between two adjacent coaxial resonators can be preset and/or varied by presetting the distance between the position of the internal conductors and/or the internal conductor extending transversely from the housing base or the housing cover.

17. The high frequency filter as claimed in claim 1, wherein the inductive coupling between two adjacent coaxial resonators can be preset and/or varied by a differing size of a coupling window or a coupling aperture between two adjacent coaxial resonators.

18. The high frequency filter as claimed in claim 1, wherein the inductive coupling between two adjacent coaxial resonators can be preset and/or varied by coupling pins which are positioned on the same side of the housing as the internal conductors on the housing.

19. The high frequency filter as claimed in claim 1, wherein the inductive coupling between two adjacent coaxial resonators can be preset and/or varied by a coupling web which extends between two internal conductors at a partial height compared to the internal conductors and is preferably positioned on the same housing wall on which the internal conductors are electrically and mechanically bound and held.

20. The high frequency filter as claimed in claim 1, wherein the inductive coupling between two adjacent coaxial resonators can be preset and/or varied by at least one coupling loop arranged between two internal conductors of two adjacent coaxial resonators, the coupling loop being bendable and/or rotatable for varying the coupling inductance.

21. The high frequency filter as claimed in claim 1, wherein the high frequency filter comprises, in addition to one or more blocking circuit couplings, one or more capacitive cross-couplings.