Helical resonator filter including short circuit stub tuning
First Claim
1. A resonator filter comprising:
- a conductive element grounded at a point and having an impedance to ground that increases with distance of a position from the point; and
a wound resonator having one end adapted to be coupled to any one of a range of the positions on the conductive element, said wound resonator further having a tapping point at a distance from the one end for connection to a utilization circuit, whereby the impedance from the tapping point to ground is equal to the sum of the impedance from the tapping point to the end of the wound resonator and the impedance from the one position on the conductive element to ground.
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Accused Products
Abstract
The present invention relates to a radio frequency filter the resonators (6,7) of which are made up of a wire wound into a cylindrical coil comprising a number of turns and of a surrounding casing (41). Finger-like projections (3) of an insulating plate (1) support the conical coils from the inside, and the coupling to the resonator is from a microstrip line (8), at a tap point (21), on the insulating plate. Each cylindrical coil has, adjoining the first turn, a straight portion (2) which is parallel to the axis of the cylindrical coil and extends towards the bottom plate (44) of the filter. On the inside surface of the bottom plate (44) there is a lead (51) one end (E) of which is short-circuited and the other end open, and the tip (12) of the straight portion (2) adjoining the cylindrical coil (6) is in contact with this lead (51). In this case, in spite of any rotation of the cylindrical coil relative to its own axis at the assembling stage of the filter, the distance of the tap point from the short-circuited end (E) of the lead (51) will remain unchanged, in which case the tap impedance will not change. The lead (51) is preferably a microstrip line on the surface of the insulating plate.
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Citations
10 Claims
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1. A resonator filter comprising:
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a conductive element grounded at a point and having an impedance to ground that increases with distance of a position from the point; and a wound resonator having one end adapted to be coupled to any one of a range of the positions on the conductive element, said wound resonator further having a tapping point at a distance from the one end for connection to a utilization circuit, whereby the impedance from the tapping point to ground is equal to the sum of the impedance from the tapping point to the end of the wound resonator and the impedance from the one position on the conductive element to ground. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A resonator filter comprising:
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at least one resonator formed from a wire wound into a cylindrical coil providing a plurality of windings and which has, adjoining a first turn a straight portion substantially parallel to the axis of the coil; an insulating plate that supports the coil from within; a circuit for coupling to the resonator at a tapping point on one of the plurality of windings where the circuit and cylindrical coil are in contact; and a lead disposed on a bottom plate transverse to the axis of the coil, the lead being short-circuited at one end and open at the other end and positioned such that the tip of the straight portion contacts the lead.
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Specification