Technically speaking, it doesn’t. Radio waves don’t travel from one radio to another—they travel from a transmitter to a receiver. Devices that both transmit and receive are called transceivers.
Radio waves are part of the electromagnetic radiation spectrum. They have wavelengths longer than those of infrared, visible and ultraviolet light, as well as x-rays and gamma rays. The frequency of radio waves ranges from 3 kHz to 300 GHz. Their wavelengths, as measured from the peak of one wave to the peak of the next, range from 1 millimeter (0.4 inch) to 100 kilometers (62 miles). These waves travel at the speed of light.
There are naturally occurring radio waves within nature, but we can create artificial radio waves with a transmitter, such as an AM or FM radio or an RFID reader. The transmitter emits waves at a particular frequency, such as 13.56 MHz. An antenna is required to pick up the signal. Since all waves within the spectrum are hitting the antenna, the antenna needs to be tuned to this particular frequency. Once the antenna has been tuned, the waves reaching the antenna can then be translated into information.
In the case of radio frequency identification, the communication between the transmitter and the RFID tag is governed by the air-interface protocol. The protocol might employ frequency shift-keying or amplitude shift-keying to indicate binary data (the ones and zeros that computers understand). Increasing a wave’s amplitude, for instance, could indicate a one, while keeping the amplitude the same could denote a zero. That series of ones and zeros is then transformed into a serial number or other information that a computer can discern.
—Mark Roberti, Founder and Editor, RFID Journal
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