Abstract: An external solenoid positioned external to a tire, and an internal solenoid provided inside a valve of the tire, which transmits and receives power by an alternating magnetic field in a predetermined high frequency band that generates an induced alternating current in the internal solenoid, is used as a new source of power for a tire pressure/temperature detection device instead of a battery. If the alternating magnetic field in a predetermined high frequency band is well matched to the physical structure and electrical structure of the tire, then, in the space between the tire and a wheel, an induced alternating magnetic field component is distributed that is substantially parallel to the axis of rotation of the tire. If the internal solenoid is matched to the direction of maximum magnetic field reception, when the tire rotates, and when the position of the wheel is stopped, substantially stable power may be received.

Abstract: A low-cost, compact circular waveguide array antenna which improves an antenna reflection loss characteristic and enables an improvement in radiation characteristics, particularly radiation gain. The circular waveguide array antenna includes feeding portions which feed electromagnetic waves to one ends of circular waveguides and radiation apertures which radiate the electromagnetic waves at the opposite ends. Each circular waveguide includes a conical horn, with a diameter of a feeding side aperture at the feeding portion end being a, a diameter of the radiation aperture being d, which is larger than the diameter a of the feeding side aperture, and an opening angle being 2?. If a wavelength of a central frequency of an employed frequency band is ?, then a value of ?, which is half of the opening angle 2?, is set between 0.8×Arcsin(0.1349114/(d/?)) and 1.2×Arcsin(0.1349114/(d/?)).

Abstract: A low-cost, compact circular waveguide array antenna which improves an antenna reflection loss characteristic and enables an improvement in radiation characteristics, particularly radiation gain. The circular waveguide array antenna includes feeding portions which feed electromagnetic waves to one ends of circular waveguides and radiation apertures which radiate the electromagnetic waves at the opposite ends. Each circular waveguide includes a conical horn, with a diameter of a feeding side aperture at the feeding portion end being a, a diameter of the radiation aperture being d, which is larger than the diameter a of the feeding side aperture, and an opening angle being 2?. If a wavelength of a central frequency of an employed frequency band is ?, then a value of ?, which is half of the opening angle 2?, is set between 0.8×Arcsin(0.1349114/(d/?)) and 1.2×Arcsin(0.1349114/(d/?)).

Abstract: A slot array antenna includes a feed waveguide plate, a radiating waveguide plate and a slot plate adhered or connected together. The feed waveguide plate is formed with a first feed port and a feed waveguide to which an electromagnetic wave is fed via the feed port. The radiating waveguide plate is formed with second feed ports communicated to the feed waveguide, and radiating waveguides communicated to the second feed ports. The slot plate is formed with slots for radiating electromagnetic waves fed via the radiating waveguides. The first feed port is positioned substantially at the center of the length of the feed waveguide. The slot array antenna allows a polarization direction of the antenna to be freely adjusted while minimizing a wasteful space otherwise allotted to peripheral circuits and is therefore miniaturized.

Abstract: In a multiple stage ladder type SAW filter constructed by cascade-connecting several SAW resonators in the form of a multiple-stage ladder, the electrode pitches of the first stage series-arm SAW resonator through the last stage series-arm SAW resonator, respectively, are gradually decreased. In this case, each stage has a series-arm SAW resonator and a shunt-arm SAW resonator. As a result, the resonance frequencies of the first stage series-arm SAW resonator through the last stage series-arm SAW resonator are increased monotonically from the first stage to the last stage. As a consequence, the frequencies of the upper poles of attenuation generated by the series-arm SAW resonators differ from each other. Therefore, a desired amount of attenuation can be obtained over a wide band.

Abstract: A SAW filter has SAW resonators coupled in a ladder network with at least one .pi.-type section. Besides having a series-arm SAW resonator and two shunt-art SAW resonators, the .pi.-type section has an inter-stage matching SAW resonator coupled in series with the series-arm SAW resonator. The inter-stage matching SAW resonator has an interdigital transducer with an electrode finger pitch substantially equal to the pitch in the series-arm SAW resonator. The inter-stage matching SAW resonator reduces impedance mismatching between the left half and the right half of the .pi.-type section.