Power active antennas

For wearable systems, including textile antennas, power efficiency represents a crucial matter, especially for the so-called autonomous systems, where the necessary power for the system operation is ideally obtained entirely by means of energy harvesting [16] from the surrounding environment, and no additional power supply is needed. Even in the case of wearable systems equipped with wearable battery units, it is very important to keep power consumption as low as possible. To this aim, several techniques were recently envisaged, by means of innovative textile antennas, such as active antennas as well as the use of multiantenna-processing techniques, such as diversity with multiple wearable antennas. 

An electrosurgery unit is a 2—300 W radio transmitter in the medium wave band around 1 MHz and connected to antenna wires of about 3 m lengths. In coagulation mode the power is strongly pulsed with peak powers of 1 kW or more. In fulguration modus, the contact between active electrode and tissue is to a large extent by electric arcs, which in themselves are powerful noise transmitters. 

The second monitored parameter is the reflected power. It provides information about the matching and the characteristics of the connection between the transmitter and the antenna. A threshold limit is defined, and any measured value above it would lead to an alarm because the balise would not receive enough energy to be activated. Therefore, the function of Balise Detection would not be accomplished. 

RFID is an automatic identification method using devices called RFID tags or transponders. An RFID tag is an object that can be attached to or incorporated into a product, animal, or person for the purpose of identification using radio waves. Chip-based RFID tags contain silicon chips and antennas. Passive tags require no internal power source, whereas active tags require a power source. 

A quality front-end with low noise figure will be required for the S-band due to the lower received power level and C/No at the antenna output. Receivers will need a good filtration system for the suppression of near-out-band interferences. AU active parts will work with a higher dynamic and a reduction of the additional processing loss wiU be necessary using multi-bit A/D converters. 

If the free-held installation is to be done on soil, the pier should have a suitable foundation to assure that it is well coupled to the ground, but not being so heavy as to modify the local soil dynamic response substantially. Free-held accelerographs must be protected with a cover or small hut from the weather. Provisions have to be made for power supply, GPS antenna, and communication, usually Ethernet via cable, satellite link, or cellular modem. And a fence around the installation would protect it from animals, human-made noises, and eventually vandalism. Accelerographs are not very sensitive to weak motions, but modem high-resolution instmments are capable of detecting human activity such as traffic or machinery working at short distance, so this kind of noise should be avoided as far as possible. 

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