Filter with improved stop/pass ratio
First Claim
1. A resonator coupling comprising:
- a transmission line resonator having an upper end which is open-circuited, a lower end which is short-circuited, and a length substantially equal to a quarter wavelength of its resonant frequency;
a transmission line for coupling to the resonator;
a tap point at which the transmission line and the transmission line resonator are in direct contact with each other, said transmission line resonator is divided at the tap point into a first lower part and a second upper part; and
a coupling element in parallel with said transmission line resonator at said tap point and being electromagnetically coupled to said transmission line resonator.
2 Assignments
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Accused Products
Abstract
The invention relates to a resonator coupling and a radio frequency filter, which comprise a transmission line resonator (106), preferably a helix resonator, having an upper and lower end, a transmission line (108, SL3) for coupling to the resonator, and a tap point (121), at which the transmission line (108, SL3) and the transmission line resonator (106) are in direct contact with each other, whereby the transmission line (106) is divided at the tap point (121) into a lower and upper part, the lower part comprising a first part (SL1) and the upper part comprising a second part (SL2). A coupling element (SL4) is placed at the tap point (121) in parallel with the transmission line resonator (106), coupled (M1) electromagnetically to the transmission line resonator (106), thus improving the stop/pass ratio of the filter. In addition, a second transmission line (SL5) can be arranged in parallel with the coupling element, coupled (M2) to said coupling element (SL4), whereby said coupling (M2) compensates for the resonating frequency change of the helix resonator with respect to the temperature.
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Citations
16 Claims
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1. A resonator coupling comprising:
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a transmission line resonator having an upper end which is open-circuited, a lower end which is short-circuited, and a length substantially equal to a quarter wavelength of its resonant frequency; a transmission line for coupling to the resonator; a tap point at which the transmission line and the transmission line resonator are in direct contact with each other, said transmission line resonator is divided at the tap point into a first lower part and a second upper part; and a coupling element in parallel with said transmission line resonator at said tap point and being electromagnetically coupled to said transmission line resonator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A radio frequency filter comprising at least one transmission line resonator, said transmission line resonator comprising:
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a transmission line resonator having an upper end which is open-circuited, a lower end which is short-circuited, and a length substantially equal to a quarter wavelength of its resonant frequency; a transmission line for coupling to said resonator and said filter; a tap point at which the transmission line and the transmission line resonator are in direct contact with each other, said transmission line resonator is divided at the tap point into a first lower part and a second upper part; and a coupling element in parallel with said trarismission line resonator at said tap point and being electromagnetically coupled to said transmission line resonator. - View Dependent Claims (14, 15, 16)
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Specification