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US 5,627,502 AGranted
Resonator filter with variable tuning
AssigneeLK-Products Oy
InventorKimmo Ervasti
Life of this patent
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AssigneeLK-Products Oy
InventorKimmo Ervasti
Estimating the term…
An advantageous embodiment of the invention is the filter of the receiver branch of the duplex filter in a multi-channel radio transmitter/receiver having reception and transmission bands composed of plural radio-frequency channels. In the first state of the filter, when the radio transmitter/receiver is only receiving radio signals, the width of the pass band of the filter corresponds to said reception band. In the second state, in which the radio transmitter/receiver additionally transmits radio signals, the pass band of the filter is switched by current control to cover only part of the reception band. By constructing the filter in the manner proposed it is possible to use current control in the first resonator in the filter of the receiver branch. Because of its power consumption current control is otherwise unsuitable for use in e.g. the duplex filter of a portable radio-telephone.
A duplex filter formed by a plurality of resonators electromagnetically coupled together, wherein a first of the resonators, positioned first in the direction of travel of an input signal, is a resonant frequency-adjustable resonator controlled by separate first and second control signals, the filter being controllable between a first state effected by the first control signal in which its passband is narrowed to a first bandwidth in a first frequency range and a second state effected by the second control signal in which its narrowed passband is moved to a second frequency range.
A duplex filter with a receiver branch and a transmitter branch for a frequency division duplex telephone transceiver, the duplex filter including a variable filter in its receiver branch, the variable filter comprising:
A method of tuning a duplex filter having a transmitter branch and a receiver branch with first and second resonators whose electromagnetic coupling to each other is controlled by control signals to form a variable receiver bandpass filter arrangement, the method comprising the steps of:
Dependencies are inferred from the claim text.