Rektenna (from the English. Rect ifying ant enna - a straightening antenna ) is a device that is a non-linear antenna designed to convert the field energy of an electromagnetic wave incident on it into direct current energy. The simplest design option can be a half-wave vibrator , between the shoulders of which a device with one-sided conductivity is installed (for example, a diode ). In this embodiment, the antenna is combined with a detector, at the output of which, in the presence of an incident wave, an EMF appears. To increase the gain, such devices can be combined into multi-element gratings.
Rectenns can be used as receivers in channels for transmitting energy over long distances, which is especially important when transporting energy from created solar power plants from orbit to Earth and vice versa, from Earth to a lifted device, for example, to a space elevator .
In 1976, the American physicist William Brown succeeded in transmitting 30 kW power to a mile (1.6 km) with a microwave beam. The recten efficiency in this experiment was a little more than 80%  , which is still lower than the power line efficiency.
One of the largest Soviet physicists, Nobel Prize winner, Academician Pyotr Kapitsa devoted a lot of time to researching the prospects of using microwave oscillations and waves to create new and highly efficient energy transfer systems. 
- Wireless power transmission
- Energy ray
- Vanke V.A., Lopukhin V.M., Savvin V.L. Problems of solar space power plants. - Uspekhi Fizicheskikh Nauk, 1977, v. 123, no. 4, p. 633.
- Microwave Electronics - Prospects for Space Energy