The loop antenna is very similar to the human body and has the function of an ordinary monopole or multi-stage antenna. Coupled with the small size, high reliability and low cost of the small loop antenna, it becomes an ideal antenna for micro-small communication products. A typical loop antenna consists of an electrical loop made of copper traces on a circuit board, or it may be a length of wire made into a loop. The equivalent circuit is equivalent to a series connection of two series resistors and an inductor (as shown in Figure 1). Rrad is the resistance model of the loop antenna actually transmitting energy, and the power it consumes is the transmit power of the circuit. Assuming that the current flowing through the antenna loop is I, then the power consumption of Rrad, that is, RF power
The loop antenna is very similar to the human body and has the function of an ordinary monopole or multi-stage antenna. Coupled with the small size, high reliability
and low cost of the small loop antenna, it becomes an ideal antenna for micro-small communication products. A typical loop antenna consists of an electrical loop made of copper traces on a circuit board, or it may be a length of wire made into a loop. The equivalent circuit is equivalent to a series connection of two series resistors and an inductor (as shown in Figure 1). Rrad is the resistance model of the loop antenna actually transmitting energy, and the power it consumes is the transmit power of the circuit.
Assuming that the current flowing through the antenna loop is I, then the power consumption of Rrad, that is, the RF power is Pradiate=I2·Rrad. Resistor Rloss is the resistance model of the loop antenna that consumes energy due to heat. The power it consumes is an inevitable energy loss, and its size is Ploss=I2·Rloss. If Rlossgt;Rrad, then the power lost is greater than the power actually transmitted, so the antenna is inefficient. The power consumed by the antenna is the sum of the transmit power and the loss power. In fact, the design of a loop antenna has almost no control over Ploss and Prad, because Ploss is determined by the conductivity of the conductor used to make the antenna and the size of the wire, while Prad is determined by the size of the area enclosed by the antenna.