Abstract: Radiation synthesizer systems provide efficient wideband operation with an antenna, such as a loop, which is small relative to operating wavelength. Energy dissipation is substantially reduced by cycling energy back and forth between a high-Q radiator and a storage capacitance. Systems using multi-segment loop antennas match antenna input impedance to switching circuit parameters. Control signal feeds employ fiber-optic cables and reduce conductive paths. Multi-voltage DC supply configurations use parallel conductor portions of antenna loop segments and reduce the need for separate DC supply conductors. Spurious conductive loops are thereby reduced and lightweight, flexible antenna constructions are enabled.

Abstract: A dipole antenna with a radiating structure comprises at least one device adapted to the conversion of analog signals into digital signals and/or digital signals into analog signals, said device being positioned in a part of the antenna that is insulated from electromagnetic waves or phenomena The antenna can be used in radiocommunications systems.

Abstract: An antenna system and method for a plurality of plasma antennas driven by means of an optical driver. In one embodiment the driver comprises one or more lasers which may be modulated by one or more electro-optical modulators to produce a modulated laser signal. The modulated laser signal may be supplied to the plasma antenna by optical fibers whereby the photons from the modulated signal impart momentum to the plasma particles. The plasma particles, which may include unbound electrons, oscillate in accord with the modulated laser signal to radiate electromagnetic energy. In one embodiment, the plasma antenna is operated at a frequency near the resonant frequency of the plasma to form a more efficient radiator requiring a smaller size than to a metallic antenna. In another embodiment a plurality of closely spaced plasma antennas are operated with different plasma resonant frequencies such that one plasma antenna is electrically invisible with respect to another plasma antenna.

Abstract: A distributed antenna array includes a plurality of antenna elements and a plurality of power amplifiers, each power amplifier being operatively coupled with one of the antenna elements and mounted closely adjacent to the associated antenna element, such that no appreciable power loss occurs between the power amplifier and the associated antenna element. Each power amplifier is a relatively low power, relatively low cost per watt linear power amplifier chip. The antenna array may be used in various installations, including cellular, PCS, MMDS, LMDS and in-building communication systems such as LANS or WLANS.

Abstract: A window glass antenna system for the reception of AM and FM radio broadcasts in an automobile includes an antenna grid applied to a window of a vehicle, that is electrically separate from a heater grid applied to the rear window. An antenna module connected to the vehicle window antenna grid is comprised of a low noise amplifier, matching, and overload protection circuits. The overload protection circuit is included between the antenna grid and the RF amplifier. When the received radio antenna signal is at the typical operating level of the amplifier, the overload protection circuit connects the output of the antenna grid to the RF amplifier. When the received signal is higher than the linear dynamic range of the amplifier the overload protection circuit provides linearity of the signal that is applied to the car radio. This process consists of two steps.

Abstract: The performance of a microwave antenna is improved by incorporating a fine wire dielectric material which has a dielectric constant ∈ of less than unity at microwave frequencies. The effect of the dielectric material is to refract microwaves so that the antenna appears to have a larger aperture than that of its physical size. Furthermore, by selecting the transmission cut off frequency of the dielectric material, two antenna elements which are intended to operate within different frequency bands can be mounted one behind the other.

Abstract: A modulator for modulating carrier wave signals with an in-phase component signal and a quadrature component signal includes a fixed frequency signal generating means for generating two fixed-frequency signals differing 90 degrees in phase, a variable frequency signal generating means for generating a signal whose frequency can be varied according to a modulated signal to be produced, an in-phase component carrier wave signal generating means for mixing one fixed-frequency signal and the variable-frequency signal to generate a carrier wave signal for an in-phase component, a quadrature component carrier wave signal generating means for mixing the other fixed-frequency signal and the variable-frequency signal to generate a carrier wave signal for a quadrature component, an in-phase component modulating means for modulating the in-phase component carrier wave signal with the in-phase component signal, and a quadrature component modulating means for modulating the quadrature component carrier wave with the quadr

Abstract: A system for information transmission having a plasma antenna, including an electrodeless plasma tube, and a power source effective to generate an electromagnetic field to cause ionization of material within the tube so as to form the antenna for one or both of either sending or receiving signals, wherein the electromagnetic field is applied to a portion only of the tube. The system preferably includes a terminal arranged about a base of the tube or establishing the electromagnetic field upon application of power from the power source, to induce surface wave ionization within the tube.

Abstract: A meter register includes a register body having a rotatable drive shaft coupled thereto. A drive gear is attached to the drive shaft and at least one follower gear is rotatably attached to the register body and coupled with the drive gear. An antenna is provided that includes a first electrically conductive sheet, a second electrically conductive sheet, and an axially extending leg electrically connected to the first electrically conductive sheet and the second electrically conductive sheet. A first electrically conductive sheet is spaced an axial distance away from the second electrically conductive sheet wherein at least a portion of the register body is sandwiched between the first electrically conductive sheet and the second electrically conductive sheet. The meter register can be attached to a meter body and, further, an auxiliary antenna can be attached to the meter register. Also disclosed is a method of operation of a utility measuring system that incorporates the above-described meter register.

Abstract: An antenna (100) includes a rectangular dielectric substrate (102); and a U-shaped conductive strip attached to a first surface of the substrate, the U-shaped conductive strip having two side members (202, 203), each about one-eighth a predetermined wavelength in length, and an end member (204) forming a substantially rectangular slot (206) extending parallel to the long edges of the substrate, the slot closed at a first end (212) by the end member, and open at a second end (208).

Abstract: A gas supplying device introduces a predetermined gas into a vacuum chamber, while an evacuation device is exhausting the gas to maintain the inside of the vacuum chamber at a predetermined pressure. A high frequency power source for an antenna is supplied to an antenna provided protrudingly into the vacuum chamber with a high frequency power to generate plasma inside the vacuum chamber, and plasma processing is applied to a substrate placed on an electrode. Providing a low pass filter whose cut-off frequency is higher than the oscillating frequency of the high frequency power source between a traveling wave output terminal of a directional coupler, and an amplifier in the high frequency power supply for an antenna precisely controls power.

Abstract: A mobile telephone uses a laser diode to indicate the presence of incoming telephone calls. The laser diode is energized by the incoming radio frequency (rf) signal by rectifying the rf signal to produce dc voltage. The antenna assembly has a transparent window for the emitted light to radiate. The emitted light passes through a patterned mask to generate artistic light rays. Using different kinds of semiconductor material for the laser diode, the laser diode can emit different colors.

Abstract: The invention provides for the reception of a L-band signals and MF-band signals using a single antenna element by employing an L-band antenna in conjunction with a connection cable that acts to receive MF-band signals, the invention further providing for the isolation of the L-band signals from an MF-band processing path and isolating the MF-band signals from an L-band processing path.

Abstract: A device for generating and radiating pulses of radio frequency/microwave energy in response to pulses of laser light in which a metal layer is ohmically bonded to each side of a substrate of semiconductior material and an antenna bowtie pattern is ohmically bonded to the metal layers to form a feed structure for a Luneburg lens type antenna. There is at least one aperture available on the substrate of the semiconductor material for permitting laser light to reach the disk to produce photoconduction. The photoconductive switch is electrically connected to the storage device to facilitate fast discharge of the stored energy through the switch. The feed structure is mounted on a motorized support stand, which is connected to a center post by an arm that can rotate 360° in the azimuthal direction and ±90° in elevation. The feed structure is located on the outermost shell of the Luneburg lens, and is concave to conform to the focal radius of curvature of the outermost shell.

Abstract: In a method of generating plasma by using a high frequency in VHF or UHF band and a magnetic field, a plasma processing apparatus has an antenna and an emitting port which are adapted to supply the high frequency in UHF or VHF band to a processing chamber and a magnetic field forming unit for forming a magnetic field in the processing chamber, wherein the ratio between the radius of the antenna and the effective length of the emitting port is 0.4 or more and 1.5 or less, whereby plasma of high density and high uniformity can be generated in a wide parameter region.

Abstract: The present invention is drawn toward a plasma antenna that is preferably reconfigurable, methods of generating plasma antennas, and a method of reconfiguring the radiation pattern of a plasma antenna. The plasma antenna is comprised of a) an enclosed chamber; b) a composition contained within the enclosed chamber capable of forming a plasma; c) at least three energizing points capable of forming electromagnetic contact with the composition; and d) an energy source coupled to the at three energizing points for developing at least one conductive path of plasma within the enclosed chamber. Preferably, a modifying mechanism may be utilized to reconfigure the conductive path.

Abstract: Electromagnetic waves induced by a partial discharge which occurs at the time of internal abnormality of a gas insulated apparatus are detected by a compact antenna having a high detection sensitivity for a board frequency band.

Abstract: A substrate is processed while plasma distribution on the substrate is controlled by a plasma trap made up of a groove-shaped space between a dielectric plate and a dielectric ring provided around the dielectric plate, and a groove-shaped space between an antenna and a conductor ring provided around the antenna.

Abstract: With a circular signal receiving antenna unit (4) constituted by combining two pieces of semicircular conductive plates on a plane in a metallic vessel (3) for the gas insulated apparatus, the electromagnetic waves due to the partial discharge can be detected with a high sensitivity for a broad frequency band. The detected signals are measured by a measuring unit (10) via a hermetical seal coaxial terminal (7) and a coaxial cable (8). The antenna portions of the semicircular plates are designed to extend over a large area. Thus, a capacitance with a potential measurement portion can be increased and a potential measurement with high sensitivity can be performed.

Abstract: An antenna adapted to apply a uniform electromagnetic field with high energy density to a volume of gas. The antenna includes an input node for receiving electrical energy and a first coil for radiating electromagnetic energy into the gas. The first coil is connected to the input node on one end thereof and is grounded on the opposite side to cause flux to flow in a first direction. A second coil is included for radiating electromagnetic energy into the gas. The second coil is also connected to the input node on one end thereof and grounded on the opposite side to flow in the first direction. Multiple number of coils can be added to form an antenna. In an illustrative application, the antenna is used in a plasma processing system comprising a vacuum chamber, a gas disposed within the vacuum chamber, and a dielectric disposed around the vacuum chamber. The inventive antenna is mounted around the dielectric tube and radiates electromagnetic energy into the gas.

Abstract: A pivotable and retractable antenna contains mechanical and electrical components for connecting to, and matching the impedance of, radio frequency circuitry within an electronic device, such as a radiotelephone. A dielectric substrate has one end movably mounted to the housing of a radiotelephone and an opposite free end. The end movably mounted to the housing is configured to move into various positions to allow the dielectric substrate to have a first extended position, a second extended position and a retracted position. In a first extended position, the dielectric substrate extends along a longitudinal direction defined by the radiotelephone housing. In a second extended position, the dielectric substrate free end is pivoted away from the radiotelephone in a direction transverse to the longitudinal direction of the housing.

Abstract: Synthesizer radiating systems provide efficient wideband operation with an antenna, such as a loop, which is small relative to operating wavelength. Energy dissipation is substantially reduced by cycling energy back and forth between a high-Q radiator and a storage capacitor. Wideband operation is achieved by actively controlling power switch devices. Dissipation is further reduced during high speed switching by use of sequential switching methods to avoid dissipation of energy capacitively stored in switch capacitances, including switch control circuit capacitance. Systems using multi-segment loop antennas are arranged to match antenna input impedance to switching circuit parameters. Personal transmit/receive systems mounted on a jacket or other clothing for field use are enabled.

Abstract: The present invention is a plasma antenna that uses an acoustic mechanism to accelerate the ions of the plasma, causing them to radiate electromagnetic energy. A resonant acoustic chamber surrounds the plasma body to produce acoustic pressure waves of very high amplitude and ion accelerations sufficient to generate significant radiation. The resonant chamber is made of a material that is relatively transparent to electromagnetic radiation. Communications information in the form of a modulated frequency is imposed on the signal generated by the plasma by adjusting the resonant frequency of the chamber by changing a parameter of the chamber such as its length or wall stiffness. Varying the acoustic driving force may be used to modulate the amplitude of the radiated signal. Phase modulation may be implemented by lining the ends of the chamber with a material that can quickly alter the position of its reflective face.

Abstract: A plasma antenna with a plasma column is provided. Lasers are disposed to transmit photon beams through the plasma in an alternating, oppositely directed fashion. When a laser is energized, its laser beam produces photon-electron collisions that impart momentum to electrons in the plasma. Alternating the operation of the lasers produces an alternating current in the plasma that radiates an electromagnetic field.

Abstract: A broadband impedance matching circuit employs active circuits featuring non-Foster reactance behavior, such as negative capacitor circuits and negative inductor circuits, to achieve extremely broadband matching of electrically small antennas. The matching circuit includes at least one non-Foster reactance circuit selected to neutralize the reactance exhibited by the antenna. The circuit further includes a dynamic dispersive impedance transformer circuit which compensates for the frequency dependent radiation resistance presented by the electrically small antenna. The dynamic dispersive impedance transformer is constructed using complementary Foster and non-Foster reactance circuits configured as an impedance transformer.

Abstract: A horizontal plasma antenna is provided. An ionizer generates an ionizing am through a horizontal tube to form a bounded plasma column extending along a horizontal axis in a gravity field. An amplitude or frequency modulating signal is applied to Helmholtz coils to control a horizontal magnetic field that is perpendicular to the horizontal axis. The resulting changes in the magnetic field produce a drift current in the plasma that, in turn, radiates an amplitude or phase modulated electromagnetic field from the plasma column.

Abstract: An electronic price label antenna which is separate from a printed circuit board and which requires only two solder points to connect it to the printed circuit board area.

Abstract: A plasma antenna with an acoustic modulator is provided. An ionizer produ a plasma in a horizontal tube to form a bounded plasma column extending along a longitudinal axis. An amplitude-, phase- or frequency-modulated signal is applied to an acoustic transducer that directs an acoustic wave along the longitudinal axis into the plasma. The acoustic wave acts as an ion acoustic wave to oscillate ions parallel to the axis. This movement radiates an amplitude-, phase- or frequency-modulated electromagnetic field from the plasma column.

Abstract: A plasma antenna is provided. An ionizer generates an ionizing beam in a nded or unbounded plasma column extending along a vertical axis. An amplitude or frequency modulating signal is applied to an electro-optical crystal that amplitude, phase, or frequency modulates the ionizing beam. The resulting changes in the ionizing beam produce gradients in the plasma that cause ions and electrons to oscillate in a vertical path that generates alternating current having the frequency of the modulator. These currents generate an amplitude- or phase-modulated electromagnetic field that radiates from the plasma column.

Abstract: An antenna comprising a plurality of negative resistance devices and a method for making same comprising employing a removable standoff layer to form the gap between the microstrip antenna metal and the bottom contact layer.

Abstract: A standing wave plasma antenna is provided. An ionizer generates an ioniz beam in a bounded plasma column extending along a vertical axis. A modulating signal is applied to an electro-optical crystal that modulates the ionizing beam. The resulting changes in the ionizing beam produce gradients in the plasma that cause ions and electrons to oscillate in a vertical path that generates alternating current having the frequency of the modulator. At a remote end the antenna terminates in a reflector. The reflector includes a chamber having a plasma with a charged particle density that is greater than the charged particle density in the plasma. The generated currents are therefore reflected as in a standing wave antenna. These currents generate an amplitude-, phase- or frequency-modulated electromagnetic field that radiates from the plasma column.

Abstract: An antenna system is described having a plurality of elements, one of which is an active element for transmitting or receiving signal, the remaining lements acting as reflectors, and wherein the elements may be comprised of a series of diodes connected in series with conductors having a length that is a fraction of the wavelength of the design frequency. When its diodes are biased for conduction, an element can radiate or receive r.f. signals or act as a reflector, and when its diodes are not conducting, the element is transparent to r.f. of the design frequency.

Abstract: A rugged telephone antenna device for transmitting a short pulse duration signal of predetermined radio frequency that eliminates a trailing antenna resonance signal. The device includes a flexible or protected gas filled tube; a voltage source for developing an electrically conductive path along a length of the tube corresponding to a resonant wavelength multiple of the predetermined radio frequency; and a signal transmission source coupled to the tube for supplying a radio frequency signal to the conductive path for antenna transmission. A method for transmitting a short pulse signal without a trailing residual signal is also provided.

Abstract: A system utilizing a number of micro-strip antenna apparatus embedded in or mounted on the surface of a structure for enabling wireless communication of sensed and actuation signals. The micro-strip antenna apparatus may include smart materials or other substrates. If only a sensed operation is desired, the micro-strip antenna apparatus may be fabricated from only passive elements or materials. Furthermore, a micro-strip antenna apparatus is provided which enables simultaneous transmission/reception of sensing and actuation signals.

Abstract: An antenna is provided in which electromagnetic signals in the High Frequy and Super High Frequency bands are propagated utilizing ionized gas, or plasma. Energized electrodes ionize the gas and the plasma is confined within non-metallic coaxial tubes contained within a non-metallic pressure vessel. Electric field gradients are used to change the shape and density of the plasma to affect the gain and directivity of the antenna. The inner plasma tube acts as the radiating source, while the outer plasma tube is used to change the radiation of the inner tube and to reflect the radiated signal. Instrumentation measures the density of the plasma providing a means to measure incoming signals as well as to regulate the radiation frequency.

Abstract: A patch antenna is provided with one or more tuning strips spaced therefrom and RF switches to connect or block RF currents therebetween. When a conducting path for RF current is connected between the tuning strips and the patch, the tuning strips increase the effective length of the patch and lower the antenna's resonant frequency, thereby allowing the antenna to be frequency tuned electrically over a relatively broadband of frequencies. If the tuning strips are connected to the patch in other than a symmetrical pattern, the antenna pattern of the antenna can be changed. A feed network couples RF to the antenna and includes two hybrid couplers, one for providing the correct amplitude and phase of excitation at the feed probes, and the second for effectively dissipating reflected power due to antenna impedance mismatch.

Abstract: An aperture coupled patch splits energy from two different polarization components to different locations to spread heat. In addition, there is no physical electrical connection between the slot, patch and circuitry. The circuitry is located under a ground plane which shields against harmonic radiation back to the RF source.

Abstract: A polarization diversity device for reducing a fading effect. The polarization diversity device for reducing a fading effect, which has a microstrip disk type of antenna for outputting a signal received from a first position, in the form of a field dipole polarized in a direction of X, and outputting a signal received from a second position perpendicular to the first position, in the form of a field dipole polarized in a direction of Y, a phase shifter for phase-shifting the signal received from the second position, thereby to set the signal having the most appropriate value to a fading environment of a corresponding channel, and a combiner for combining the signal received from the first position, with the signal outputted from the phase shifter.

Abstract: A flat panel-configured electronically steered phased array antenna includes a planar distribution of densely nested microstrip dipole sub-arrays, arranged and controlled in a manner similar to microstrip `reflect-array` antenna elements. The resultant phase of a circularly polarized wave for a reflect-array fan-out distribution of dipole antenna elements is controlled by an associated plurality of triode-configured field emission devices. Each dipole element sub-array is plated to a resistive sub-layer on an interior surface of a flat first millimeter wave transmissive panel member of an evacuated flat panel type support structure. Mounted to a similar resistive layer on the interior surface of a second, flat panel member is a microstrip conductive layer partially overlapped around its periphery by respective fan-configured microstrip dipole antenna elements plated on the first panel member.

Abstract: An active reception antenna with a coplanar waveguide having a high actual gain in the frequency band as broad as 100% or larger of the central frequency. The reception active antenna with a coplanar waveguide has: a pair of coplanar waveguide functioning as a feeder, the coplanar waveguide including a center conductor and two ground conductors printed on one surface of a dielectric film; and an antenna element conductor connected to the coplanar waveguide, the antenna element conductor being printed on the surface of the dielectric film, wherein the feed points of the antenna element conductor are disposed near the ends of the feeder, an active circuit including a field effect transistor is mounted between the feed points and the ends of the feeder, the impedance of the antenna element conductor and the feeder is matched together, and a signal received by the antenna element conductor is amplified and supplied to the feeder.

Abstract: An antenna system for a navigation satellite receiver tuned to dual-frequency transmissions from orbiting navigation satellites. Respective L1 and L2 microwave patch antennas are mounted flat and adjacent to one another on a common ceramic substrate and have their centers grounded to a groundplane on the opposite side of the substrate with vias. Each patch antenna is connected to a respective near-by low-noise amplifier. The low-noise amplifiers are both connected to a signal combiner and a final radio frequency amplifier for down feed to a navigation satellite receiver. A direct current signal from the navigation satellite receiver is used on the down-feed to selectively control which one of the two low-noise amplifiers is to operate. Thus one coaxial down-feed supplies power to the low-noise amplifiers and provides for the selection between the L1 and L2 carrier frequencies on the down-feed.

Abstract: An RF apparatus (e.g., a wireless label) provides improved backscattering of an incident RF signal by utilizing a separate modulator diode, which connects across the antenna, to modulate the backscattering of the antenna. A separate detector diode connects across the antenna through an impedance matching network to detect modulated signals received by the antenna.

Abstract: An antenna device for transmitting a short pulse duration signal of predetermined radio frequency that eliminates a trailing antenna resonance signal. The device includes a gas filled tube; a voltage source for developing an electrically conductive path along a length of the tube corresponding to a resonant wavelength multiple of the predetermined radio frequency; and a signal transmission source coupled to the tube for supplying a radio frequency signal to the conductive path for antenna transmission. A method for transmitting a short pulse signal without a trailing residual signal is also provided.

Abstract: An antenna structure (10) that includes a plurality of transmit linear elements (22a-22d) arranged parallel to one another and a plurality of receive linear elements (24a-24d) also arranged parallel to one another. Individual ones of the plurality of transmit linear elements are spaced apart from one another and have one of the plurality of receive linear elements disposed therebetween. A width of each of the plurality of transmit linear elements and the plurality of receive linear elements varies periodically along a length of the linear element, thereby also periodically impedance modulating each element. Furthermore, a narrowest width portion of a transmit linear element is disposed adjacent to a widest width portion of an adjacently disposed receive linear element, and vice versa, thereby minimizing coupling between the elements.

Abstract: A low noise dual polarization electromagnetic power reception and conversion system is disclosed. It comprises a first plurality of conducting elements performing a bandpass function on incident waves, a second plurality of antenna units, located behind the first elements, performing a power reception and conversion function, and a third plurality of conducting elements located behind the antenna units, performing a bandstop function on incident signals. A layer of lossy material is optionally disposed behind the third elements to absorb any wave passing through them. This system can be used to achieve high efficiency power reception and conversion and also reduce levels of radiation of both harmonics of the powering frequency and intermodulation products formed by nonlinear mixing of signal wavefields from other users of the radio spectrum with the powering signal wavefield.

Abstract: An antenna system includes a set of symmetrically located center-fed and segmented dipole antennas embedded on top of a frequency selective photonic bandgap crystal. A two-dimensional array of microelectromechanical (MEM) transmission line switches is incorporated into the dipole antennas to connect the segments thereof. An MEM switch is located at the intersection between any two adjacent segments of the antenna arm. The segments can be connected (disconnected) by operating the switch in the closed (open) position. Appropriate manipulation or programming of the MEM switches will change the radiation pattern, scanning properties and resonance frequency of the antenna array. In addition, an MEM switch is inserted into the crystal to occupy a lattice site in the 3-dimensional crystal lattice.

Abstract: A microwave detector, which integrates two circular patch antennas with a detector diode. The high impedance at the edge of the circular patch antenna is combined with 180.degree. out of phase electric fields at diametrically opposite points, so as to match to the RF impedance of a zero or small DC bias diode. The result is a very simple, high-sensitivity narrow-band microwave integrated detector.

Abstract: A storm monitoring apparatus and method is described wherein two H-field antennas are oriented with respect to the heading axis of an aircraft or the like at an angle of 45.degree.. The signals developed by these two antennas are picked-up by small R-F transformers which serve the inherent function of integrating the signals and extracting the H-field current component. A printed circuit board structuring of the two antennas provides for consistency of fabrication and reliability as well as compactness. The monitoring apparatus exhibits broad band frequency response to evaluate lightning strike rate to determine storm range and intensity. A computer control test utilizing diagnostic coils at the antenna carries out periodic testing of the performance of the device and a component such as a gravity switch provides an indication to the control system as to the orientation of mounting of the antenna on an aircraft.

Abstract: A detector for electromagnetic radiation includes a high Q, low loss antenna and a low noise amplifier requiring a high input impedance. In the preferred embodiment, the antenna comprises a low resistance, superconductive coil. The antenna forms a resonant circuit with a low loss capacitor, optionally a capacitor including superconductors. The output of the resonant circuit is provided as input to the semiconductor amplifier. In the preferred embodiment, junction FETs, preferably arranged in a cascode pair, are included in the semiconductor amplifier. In one aspect of the invention, feedback is provided from the output of the amplifier to its input. Effective loading of the antenna results, lowering the Q of the antenna, and broadening the bandwidth of the detector. Optimum matching of the antenna to the noise factor of the amplifier is achieved.

Abstract: A detectable device attachable to a movable item for detecting movement. Radio waves having a predetermined frequency are received by the detectable device, and radio waves having a harmonic frequency of the received waves are reradiated from the detectable device. The detectable device comprises a dipole antenna for receiving radio waves with said predetermined frequency, a diode connected in parallel to feed points of the dipole antenna for generating an electric current having a harmonic frequency of said received radio waves. A loop antenna is provided whose feed points are connected in parallel to feed points of the diode for converting the electric current having the harmonic frequency to radio waves for transmitting the radio waves at the harmonic frequency.