Rectifying antennas

Rectifying Antennas Appiied to Solar Power Conversion... 

Work on the rectenna portion of a power beaming system produced significant improvements to power systems, and a number of milestones that make the concept interesting from a satellite power system point of view. Development work during this time period resulted in an 85% efficient rectifying antenna utilizing linearly polarized radiation at 2.45 GHz with the efficiency... 

A rectenna (rectifying antenna) at the target can convert the microwave energy back into electricity. Conversion efficiencies of more than 95 percent have been achieved with rectennae. 

A classical setup for microwave conductivity measurements is based on the utilization of the waveguides. A simple installation consists of a microwave generator (typically a gun diode) which, when the Ka-band is used, can be operated in the frequency region of 28-40 Gc/s this is protected by an isolator against back-reflections from the rest of the microwave circuit. The microwave power is conducted by an attenuator across a circulator into the microwave conductor branch at the end of which the electrochemical cell is mounted. The microwave power reflected from the electrochemical sample is conducted via the circulator into the microwave detector. It typically consists of a diode that acts as an antenna, receiving the electrical alternating field, rectifying it, and con-... 

The most general method of encoding a chemical library is based on a small device which, upon activation, emits a given radiofrequency (rf). This device needs to be attached to the synthetic platform (beads, resins, tubes, etc.) on/in which the synthesis of products takes place. The device (which is 8 mm x 1 mm in size) contains three components first, a memory for alphanumeric codes second, a rectifying circuit which absorbs radiofrequency energy and converts this energy into electrical energy. The latter is used by the third component, an antenna, to transmit the code to an external receiver that is linked to a computer. 

A transceiver controlled by a computer is used to interrogate and receive the ID code of each RF tag. The transceiver antenna transmits a specially modulated, 125 kHz electromagnetic field. This field is of very low energy and not harmful. When an RF tag is held within about 1 cm from the transceiver s antenna, energy is picked up by the RF tag s antenna. A rectifier in the chip converts this energy to microwatt levels of DC power, which is enough to power-up the logic circuitry on the chip. In a very real sense, the RF tag is similar to a crystal radio (which does not require an external power source), except that the device serves as both receiver and transmitter. It is self-contained , in that the chip uses no internal batteries and has no external metallic connections. 

These MIM diodes can be used as mixing elements at optical frequencies. When illuminating the contact point with a focused CO2 laser, a response time of 10 s or better has been demonstrated by the measurement of the 88-THz emission from the third harmonic of the CO2 laser. If the beams of two lasers with the frequencies f and /2 are focused onto the junction between the nickel oxide layer and the sharp tip of a tungsten wire, the MIM diode acts as a rectifier and the wire as an antenna, and a signal with the difference frequency f — f2 is generated. Difference frequencies up into the terahertz range can be monitored [4.111] (see Sect. 5.8.7). The basic processes in these MIM diodes represent very interesting phenomena of solid-state physics. They could be clarified only recently [4.111]. 

These MIM diodes can also be used as mixing elements at optical frequencies. If the beams of two lasers with the frequencies f and f2 are focussed onto the junction between a nickel surface and the sharp tip of a tungsten wire the MIM diode acts as rectifier and antenna, and generates a signal with the difference frequency Difference frequencies up into... 

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