Abstract: A filter device includes a super-conducting type filters connected in series with each other and is accommodated in a vacuum chamber. Operating temperatures of the filters are controlled to different temperatures from the outside of the vacuum chamber independently of each other. Each filter varies its filtering characteristics, particularly its central frequency of pass-band, in correspondence with the operating temperature, while maintaining the same pass-band width. As the filters operated at the different operating temperatures provide different filtering characteristics, the combined or resulting filtering characteristics of the filtering device can be adjusted as desired even after the filtering device is installed at a mobile telecommunication base station.

Abstract: A linear compressor, comprises a fixed member formed with a hermetically sealed compression chamber, a movable member axially movably received in the compression chamber of the fixed member, a plurality of resilient members each intervening between the fixed member and the movable member, driving means for driving the movable member, damping means for damping vibrations of the fixed member, the damping means including a retaining member fixedly connected to the fixed member and a weight member axially movably supported by the retaining member, first detecting means for detecting a displacement of the movable member, second detecting means for detecting a displacement of the weight member, and controlling means for controlling the driving means to have the movable member perform a reciprocally linear motion to ensure that the vibrations of the fixed member are damped by the damping means.

Abstract: A linear compressor, comprises a retaining member, a fixed member supported by said retaining member and formed with a hermetically sealed compression chamber to receive a working fluid therein, a pair of pistons axially movably received in said compression chamber to assume respective compression positions, a pair of piston rods each having an outer peripheral portion and slidably movably supported by said fixed member, said piston rods respectively connected to said pistons to have said pistons axially move in said compression chamber, a plurality of magnet units mounted on each of said outer peripheral portions of said piston rods, each of said magnet units having a plurality of magnet segments each made of a permanent magnet and circumferentially arranged with neighboring two magnet segments different in magnetic pole, a plurality of electromagnet units supported by said retaining member to be axially spaced apart from each other in predetermined relationship with said magnet units, respectively, and resi

Abstract: A filter for filtering electrical signals comprises a substrate and a plurality of resonators formed circularly to surround the center of the substrate. Each resonator has an arcuate part at a radially outermost part and a pair of linear parts extending from ends of the arcuate part in a radially inward direction. The arcuate part is located at the same distance from the center of the substrate. The linear parts of each resonator have different lengths from each other thereby to provide a sharp decrease of gain at ends of the frequency passband in a filtering response.

Abstract: A filter has a plurality of resonators formed regularly on a substrate and made of a superconducting material. In measuring resonance frequency of the resonators, the filter and a conductive metal plate having an opening are placed in a vacuum chamber so that all the resonators other than one resonator which faces the opening are covered with the metal plate. The metal plate has an input probe and an output probe at the opening of the metal plate. The resonance frequency of each resonator is measured in sequence while rotating the metal plate. Each resonator is adjusted in shape by a laser trimming or providing a dielectric film in correspondence with the measured resonance frequency so that all the resonators have a fixed resonance frequency.