Wireless power transfer
(WPT) is the transmission of electrical power from a power source to a consuming device without
using discrete manmade conductors. Researchers have developed several
techniques for moving electricity over long distance without wires. Some exist
only as theories or prototypes but others are already in use. This paper
provides the techniques used for wireless power transmission. It is a generic
term that refers to a number of different power transmission technologies that
use time varying electromagnetic fields.
Wireless transmission is
useful to power electrical devices in case where interconnecting wires are
inconvenient, hazardous, or are not possible. For example the life of WSN is
its node which consist of several device controllers, memory, sensors, actuators,
transceivers and battery and battery. The transceiver can operate in four
states, i.e 1) Transmit 2) Receive 3) Idle and 4) Sleep. The major energy
problem of a transmitter of a node is its receiving in idle state, as in this
state it is always being ready to receive, consuming great amount of power.
However, the batter has a very short lifetime
and moreover in some developments owing to both practically and economically
infeasible or may involve significant resists to human life. That is why energy
harvesting for WSN in replacement of battery is the only and unique solution.
In wireless power transfer, a transmitter device source, such as the mains
power line, transmits power by electromagnetic fields across an intervening
space to one or more receiver devices, where it is converted back to electric
power and utilized. In communication the goal is the transmission of
information, so the amount of power reaching the receiver is unimportant as
long as it is enough that signal to noise ratio is high enough that the
information can be received intelligibly. In wireless communication
technologies, generally, only tiny amounts of power reach the receiver. By
contrast, in wireless power, the amount of power received is the important
thing, so the efficiency (fraction of transmitted power that is received) is
the more significant parameter.