Review Article

Comparative Study of Antenna Designs for RF Energy Harvesting

Table 3

Various antenna shapes and their reconfigurability.

FigureAntenna shapeFreq.Reconfigurable featureCause of reconfigurabilityApplication

5(a)Square patch with orthogonal slots and two pin diodes on the slots4.64 GHzPolarization diversity (LHCP or RHCP)By turning the diodes on or off, either RHCP or LHCP can be obtained with the same feeding probe, which is located on the diagonal line of the patchWLANs, satellite links, and space robots
5(b)Square patch consisting of two orthogonal L-shaped slots with two pin diodes on the slots4.44 GHz and 4.49 GHzPolarization diversity (LHCP or RHCP)Reconfigurability is achieved by switching two pin diodes. In RHCP antenna, diode a is turned ON, and diode b is turned OFF; in LHCP antenna, diode b is turned ON, and diode a is turned OFF.Unlicensed and licensed WiMax (IEEE 802.16a), future planetary missions, and satellite links
5(c)Square patch coupled to a microstrip line by an aperture in the ground plane2.45 GHzPolarization diversity (LHCP or RHCP)Reconfigurability is obtained by selecting one of two excitation points and terminating the other with a 50-resistive load. RHCP is obtained if the excitation point is located on Port 1, and LHCP is obtained if the antenna is fed at Port 2Not available
5(d)A circular patch rotates to feed different shapes. The rotating circular part includes three circular patches and one slotted triangleCovers five different bands 
(from 2 GHz up to 7 GHz)
Frequency diversityReconfigurability is achieved by rotational motion of part of the antenna patch. With every rotation, a different antenna structure is fed in order to produce a different set of resonant frequenciesCognitive radio systems
5(e)Short-circuited triangular patch antenna with truncated corner having two shorting walls and a V-shaped slot patch2.5–2.55 GHz 
and 3.4–3.7 GHz WiMax bands
Frequency diversityBy placing two shorting walls with a V-shaped slot patch, two resonant modes can be excited simultaneously, yielding frequency diversityCovers 2.5–2.55 GHz 
and 3.4 to 3.7 GHz WiMax bands
5(f)Two rectangular slots properly positioned along the diagonal of a square patch antenna5.15–5.35 GHz and 5.5 GHzFrequency diversity and polarization diversity (LHCP or RHCP)Positioning the slots along the left diagonal and right diagonal generates RHCP and LHCP, respectivelyCan function as a rectenna for wireless battery charging at 5.5 GHz and data telemetry in the 5.15–5.35 GHz WLAN band
5(g)Square patch with two pin diodes on a U-slot along with two diodes on the truncated corners2.415 GHz 
and 2.650 GHz
Frequency diversity and polarization diversity (LP, LHCP, or RHCP)The switching of the PIN diode on the U-slot realizes frequency diversity and polarization diversity among LP, RHCP, and LHCP is obtained by switching three PIN diodes on the slot and the truncating corners of a square patch on and offWLAN/digital multimedia broadcasting applications