Abstract: Providing a radio communications medium processing unit which suppresses variations in potential at the grounding end and variations in ground potential used for signal processing, thereby performing accurate signal processing. The invention comprises an antenna, a read/write section for reading or writing data, or reading and writing data from/to a radio communications medium via the antenna, a conductive line having an electric distance below the quarter wavelength of a frequency in use, the conductive line connected to the extremity of at least one grounding end present on the read/write section and the antenna, and a variable lumped constant unit for changing the lumped constant of the impedance connected at some midpoint in the conductive line, characterized in that the extremity of the conductive line is an open end.

Abstract: The invention is aimed at providing a gate antenna device which expands the distance and range of communication with an IC-integrated medium and improves the accuracy of communication while suppressing power consumption and leakage electric fields. A gate antenna device having a plurality of loop antennas which supplies power and transmission data to an IC-integrated medium through electromagnetic induction and acquires reception data in the form of a fluctuation of a load from the IC-integrated medium. The plurality of loop antennas include a power-fed loop antenna to which a signal current is supplied and a non-power-fed loop antenna to which no signal current is supplied.

Abstract: The object of the invention is to provide a small-sized noncontact IC card reader/writer that can enhance the efficiency of an amplifier at a low cost.

Abstract: It is an object of the invention to provide an electromagnetic wave shield for attenuating a electric far field while suppressing the attenuation of the vicinal magnetic flux of an electromagnetic wave discharged from a high frequency electromagnetic wave generator. An electromagnetic wave shield according to the invention comprises a plurality of electric conductors, a ground contact for carrying out a connection to a ground, and a lead wire for connecting the electric conductors to the ground contact, the electric conductors being electrically connected to the ground contact through the lead wire, wherein the electric conductors are provided in such a manner that a path reaching the ground contact through the lead wire from an optional point of each of the electric conductors is uniquely determined.

Abstract: To provide a loop antenna capable of attenuating the distant electric field with the attenuation of the magnetic flux in the vicinity of an electromagnetic wave restrained, and a contactless IC card read/write apparatus. A loop antenna 10 has an electromagnetic wave shield 1 over at least one side of the loop antenna, the electromagnetic wave shield 1 comprising a plurality of electric conductors 2, a ground contact 3 for grounding the plurality of electric conductors and a lead wire 4 for connecting the plurality of electric conductors 2 to the ground contact 3. The plurality of electric conductors 2 are electrically connected via the lead wire 4 to the ground contact 3 and the plurality of electric conductors 2 are arranged so that the paths of the respective electric conductors 2 from any of their given points to the ground contact 3 via the lead wire 4 are determined uniformly.

Abstract: The object of the invention is to provide a noncontact IC card reader/writer integrated with an antenna that does not require the limitation of an installation location and the adjustment of a resonance frequency of the antenna, is convenient in installation, is provided with a stable characteristic, is small-sized and low-priced. To achieve the object, the invention is provided with a loop antenna that supplies electric power and send data to a noncontact IC card by electromagnetic induction and acquires receive data from the noncontact IC card by load fluctuation, a magnetic body arranged closely at the back of the loop antenna, a first metallic plate arranged on the back side of the magnetic body and a second metallic plate arranged on the back side of the first metallic plate and larger than the first metallic plate in size.

Abstract: It is an object of the present invention to provide a small thin integrated antenna type non-contact IC card reader/writer, the characteristic of which is stable, characterized in that: the device is seldom affected by the restriction of a place in which the device is installed; the device is seldom affected even when the coaxial cable is laid round the device; and it is unnecessary to adjust the resonance frequency of the antenna, so that the device can be easily installed.

Abstract: An object of the present invention is to provide a non-contact IC card reading/writing apparatus having a superior reception characteristic.

Abstract: An antenna device includes: a radiator having a meander portion; and a conductor shorter than the radiator which is disposed opposite to the radiator. A coaxial cable is connected to the radiator and conductor. Respective line lengths of the radiator and conductor satisfy a predetermined relation with respect to a wavelength of a signal to be transmitted and received. The antenna device achieves at least one of improved antenna characteristics, downsizing, and improved mechanical strength.

Abstract: An antenna device includes: a radiator having a meander portion; and a conductor shorter than the radiator which is disposed opposite to the radiator. A coaxial cable is connected to the radiator and conductor. Respective line lengths of the radiator and conductor satisfy a predetermined relation with respect to a wavelength of a signal to be transmitted and received. The antenna device achieves at least one of improved antenna characteristics, downsizing, and improved mechanical strength.

Abstract: An antenna includes a grounding plate and a plurality of radiator elements in rectangular shape. The elements are disposed on the grounding plate with its one end being electrically coupled to the grounding plate. Longitudinal lengths of the elements are set within a range of &lgr;/8-3&lgr;/8 so that working frequencies are adjusted at given frequencies. Accordingly, this one antenna can transmit and receive frequencies in a desired frequency band. A coupler is disposed between the plurality of elements, and only one element is fed with power, while the other elements are fed indirectly, so that numbers of feeding points and feed lines are reduced. Further, a distance between the grounding plate and the elements is adjusted to a 0.5-3 inch range, whereby a thin and low antenna is obtainable.

Abstract: An antenna device includes radiation elements formed on a common antenna board, a feeding unit for feeding the radiation elements, and a ground plate provided in electrically-spaced relation to the radiation elements. The ground plate is mounted on a box-like metal body to form a short-circuit therewith. The radiation elements may have different line lengths for transmitting and receiving a plurality of wavelengths. The feeding unit may include a first radiation element having a different electrical length than a second radiation element, a first feed point for feeding electric power to the first radiation element, and a second feed point for feeding radiation elements are grounded to the ground plate at respective first and second ground points. The difference from the first and second feed points to their respective ground points are different from one another.