A THz device includes: an antenna electrode capable of transmitting and receiving a THz wave to free space; first transmission lines capable of transmitting the THz wave, the first transmission lines respectively connected to the antenna electrodes; an active element of which a main electrode is connected to each of the first transmission lines; second transmission lines capable of transmitting the THz wave, the second transmission lines connected to the first active device; pad electrodes respectively connected to the second transmission lines; and a low-pass filter with respect to the THz wave, the low-pass filter connected to the pad electrodes, wherein impedance matching of between the antenna electrode and the active element is performed by an impedance conversion of the first transmission lines. The THz device is capable of the high-efficiency matching between the active element and the antenna due to the impedance conversion effect of the transmission line.

Techniques for tuning a crossed-field antenna are provided. An example of an antenna system includes a D-plate with a D-plate feed conductor, such that the D-plate is a horizontal conductor raised above and insulated from a ground plane, an E-cylinder with an E-cylinder feed conductor, such that the E-cylinder is a vertical hollow conductive cylinder of smaller diameter than the D-plate, which is mounted concentrically above and insulated from the D-plate, a transmitter tuning circuit configured to receive a signal from a transmitter, an E-cylinder tuning circuit operably coupled to the transmitter tuning circuit and the E-cylinder feed conductor, and a D-plate tuning circuit operably coupled to the transmitter tuning circuit and the D-plate feed conductor.

Techniques for tuning a crossed-field antenna are provided. An example of an antenna system includes a D-plate with a D-plate feed conductor, such that the D-plate is a horizontal conductor raised above and insulated from a ground plane, an E-cylinder with an E-cylinder feed conductor, such that the E-cylinder is a vertical hollow conductive cylinder of smaller diameter than the D-plate, which is mounted concentrically above and insulated from the D-plate, a transmitter tuning circuit configured to receive a signal from a transmitter, an E-cylinder tuning circuit operably coupled to the transmitter tuning circuit and the E-cylinder feed conductor, and a D-plate tuning circuit operably coupled to the transmitter tuning circuit and the D-plate feed conductor.

A non-contact communication apparatus 100 includes an antenna resonant unit 110 and an antenna drive unit 130. In the antenna drive unit 130, for example, a measurement unit consisting of an differential amplifier A3 measures an output current from an oscillation unit 131. A control unit 140 detects a minimum value or maximum value of the output current. The resonant frequency is controlled by the use of an optimal control value corresponding to the minimum value or maximum value. Therefore, even if the resonant frequency fluctuates due to variations in antenna characteristics in manufacture or a usage environment or aging, satisfactory communication characteristics at a set resonant frequency can be obtained.

A non-contact communication apparatus 100 includes an antenna resonant unit 110 and an antenna drive unit 130. In the antenna drive unit 130, for example, a measurement unit consisting of an differential amplifier A3 measures an output current from an oscillation unit 131. A control unit 140 detects a minimum value or maximum value of the output current. The resonant frequency is controlled by the use of an optimal control value corresponding to the minimum value or maximum value. Therefore, even if the resonant frequency fluctuates due to variations in antenna characteristics in manufacture or a usage environment or aging, satisfactory communication characteristics at a set resonant frequency can be obtained.

A method for resonating a conductive structure as an antenna comprising: connecting a radio frequency (RF) resonator to a transceiver, wherein the RF resonator has a conductive layer; attaching the conductive layer of the resonator to the conductive structure at a given location; balancing the impedance of the transceiver with the impedance of the conductive structure at the given location; and receiving and radiating electromagnetic waves through the conductive structure at an operating frequency of the transceiver, wherein the conductive structure has a dimension of at least one-half wavelength of the operating frequency of the transceiver.

A method for resonating a conductive structure as an antenna comprising: connecting a radio frequency (RF) resonator to a transceiver, wherein the RF resonator has a conductive layer; attaching the conductive layer of the resonator to the conductive structure at a given location; balancing the impedance of the transceiver with the impedance of the conductive structure at the given location; and receiving and radiating electromagnetic waves through the conductive structure at an operating frequency of the transceiver, wherein the conductive structure has a dimension of at least one-half wavelength of the operating frequency of the transceiver.

The wireless communication device has a first radiation element, which includes a first line path being extended between a first end and a second end and performs communication at a first frequency. The device also has a second radiating element coupled to the first radiating element and resonating at a second frequency, which element has a second line path extending from a first connecting portion connected to the sheet metal to a third end portion near the first end portion, and a third path line extending from an intermediate point between the first connecting portion and the third end portion to the fourth end portion. And a power supply circuit for a third frequency is connected to the fourth end via a cutoff circuit which cuts off the second frequency. With this configuration, the wireless communication device enables the communication in more frequency bands.

An automatically tunable mobile antenna is provided with toroidal inductors connected in series between the antenna feed point and a whip and a shunt inductor to ground at the RF input, with the inductors forming an L network impedance matching circuit having values which are in a binary sequence and which are selectively added to impedance match the whip to the output impedance of a transmitter.

An automatically tunable mobile antenna is provided with toroidal inductors connected in series between the antenna feed point and a whip and a shunt inductor to ground at the RF input, with the inductors forming an L network impedance matching circuit having values which are in a binary sequence and which are selectively added to impedance match the whip to the output impedance of a transmitter.