Abstract:
The electrical length of the parasitic antenna of a pair of 2-element Yagi antennae is varied to vary the directivity of the antenna. A radio device (12) outputs a receiving signal corresponding to the received electric field strength of a first antenna (10), a controller (15) outputs a control signal corresponding to the result of detection of the received signal to a variable impedance circuit (14), and the impedance of the variable impedance circuit (14) is varied in accordance with the control signal. The electrical length of a second antenna (13) which is parallel with the first antenna (10) with a certain spacing is varied and hence the second antenna (13) serves as a waveguide for a reflector to vary the directivity of the antenna.
Abstract:
A radio communications unit (121) that has a casing (122) includes an antenna (123) that is connected to a signal processing unit (125). A metal object (128) is placed in the casing (122) and connected to an impedance (130). The antenna (123) receives a radio signal (309) which has repeating fading moments where the signal strength C is exceedingly low. The signal processing unit (125) includes means for controlling switch means (129) and impedance unit (130). In their simplest form, these control devices are manual, although they may alternatively comprise devices (134, 135, 136) that are integrated in the signal processing unit (125) which controls the activation of the metal object (128) and the impedance (130) with control signals (S1, S2). When the antenna (123) is situated in a fading minimum, the metal object (128) is either connected to or disconnected from the impedance unit (130), resulting in new signal reflections that cause the fading minimum to be moved away from the antenna (123).
Abstract:
A radiation sensor (10) for the microwave and millimetre-wave regions incorporates a lens (12) having two parallel focal planes (26a, 36), these being defined by a polarization-selective reflecting PIN diode array (18) within the lens (12). One focal plane (26a) is occupied by a receive array of crossed dipole antennas which mixes receive signals and a local oscillator signal to produce intermediate frequency signals for subsequent processing. The second focal plane (36) is occupied by a transmit antenna array of separately activatable polarization switching antennas arranged to define a range of transmit beam directions. A second PIN diode array (20) protects the receive antenna array from the transmit beam.
Abstract:
A non-mechanical beam deflector (Figs. 21A-23B) forms and scans a beam of millimeter wave (MMW) radiation, from a MMW source (268), at a rapid rate. The beam deflector includes a semiconductor body (160, 280) in which a spatially varying density of charge carriers is selectively injected, e.g., through selective optical exposure by means of an LED array (262). The injected charge carriers - electrons and/or holes - alter the dielectric constant of the semiconductor body (160, 180) locally and thereby attenuate and reflect incident MMW radiation. The portions of the semiconductor body that do not have carriers injected therein allow the incident MMW radiation to be transmitted. The semiconductor body, modified with a spatially varying density of charge carriers, diffracts the radiation which passes through it into a beam. The beam may be scanned across space through selective control of the injected charge carriers, achieved, e.g., by appropriate control of the LED array (262) by an LED control circuit (265). The diffractive conditions can be rapidly reconfigured. The spatially varying density of charge carriers may be induced optically into the semiconductor body, or directly injected using opposing p- and n-type contacts forming a p-n junction. A dynamically variable Fresnel zone plate (FZP) represents one application of the invention.
Abstract:
An electronic device for deflecting an ultrahigh frequency beam (2) emitted by a radiant source (3) is characterised by the fact that it comprises a body of magnetostrictive ferrite (1) placed in the path of the beam and subjected to magnetic polarisation, and means (4) to generate at least one elastic wave in the body to create within it a network of stresses generating a phase network in order to divert the beam. The device can be used in all ultrahigh frequency systems needing scanning, particularly millimetric, i.e. all kinds of radar, obstacle detectors, telecommunication, microwave imaging and radiometry devices, etc.
Abstract:
An array of unit cells allows beam steering of an incident electromagnetic wave. Each unit cell has a back reflector, a conductive oxide between gate dielectrics, and an antenna. Voltage bias applied to different layers enables the accumulation or depletion of charges at the top and bottom interfaces of the conductive oxide. The charge accumulation and depletion regions control the refractive index of the material, enabling control of the reflected electromagnetic wave.