21. In 1938, George Brown et al . patented a loop antenna with rhombic shape and quarterwave sides. 22. Furthermore, the loop antenna was somewhat directional. 23. The " sense coil ", another loop antenna , is placed in the area between the field coils. 24. Simple half-wave dipole antenna for VHF or UHF loop antennas that are made to be placed receiver. 25. Loop antennas are often used for reception.26. Loop antennas are relatively easy to build.27. This provides a considerable advantage for loop antennas which are relatively insensitive to the main interference sources encountered. 28. For reception, long wire antennas are used, or more often ferrite loop antennas because of their small size. 29. It can be as well a dipole antenna, a loop antenna , a parabolic antenna, or an antenna array. 30. WiTricity is based on weakly coupled electromagnetic resonant objects to magnetic loop antennas critically tuned to the same frequency.
