Therefore, we attempted to gather energy using a parasitic radiator directly from the main antennas of base stations and repeaters, which radiate RF signals.
As shown in Figure 1(a), the proposed antenna is mainly composed of two individual radiators, the main radiator and the parasitic radiator. The main radiator has the role of signal transmission for the communications service and thus can be thought of as the main antenna of a base station or repeater.
In this design, the printed rectangular loop element encloses the main radiator, the printed dipole, which is inserted in the rectangular slit of the parasitic radiator's substrate, as shown in the lower diagram of Figure 1(a).
The parasitic radiator is designed with FR4 substrate ([[epsilon].sub.r] = 4.3, tan[delta] = 0.02, t = 1 mm).
Figure 3 shows the performance variation of the main radiator according to the height of the parasitic radiator in the simulation.
The antenna is composed of two main parts, the main radiator and the parasitic radiator. As shown in the figure, the main radiator is vertically placed in the center of the ground and is inserted into the rectangular slit of the parasitic radiator.
The measured reflection coefficient of the main and the parasitic radiator according to the height of the parasitic radiator is presented in Figure 5.
Figure 6(a) shows the measured coupling coefficient (S21) between the main and the parasitic radiator. The coupling coefficient improves as the height of the parasitic radiator increases, and the coupling coefficient is about -12 dB when [h.sub.2] = 2 mm.
For the next step, the horn connected to the signal generator was exchanged with the main radiator without the parasitic radiator. In this test, the test setup is identical to the former test using two horns, while the receiving power is -37.45 dB.