How Do Wireless Transmitters and Receivers Work?

By Stephen Byron Cooper

Wireless networks, surprisingly, transmit data onto a wire. The wire in question is at the heart of a Wi-Fi antenna. Both the antenna of the transmitters and receivers in wireless networks rely on the properties of wire to transmit data as a radio signal.


Radio waves are electromagnetic disturbances that radiate out in all directions. When a current passes along a wire, it generates a magnetic field around that wire. Wi-Fi transmitters exploit this factor to pulse a current out onto the copper wire inside an antenna. The wire is grounded at one end and unattached at the other end. The grounding means each signal dissipates almost immediately, but the presence of the charge on the wire momentarily creates a force field that generates a radio wave.


Metal is a conductor of both electricity and magnetism. As the radio wave signal beams out from the transmitter, it will "stick" to any metal object it encounters. It then diverts and runs along the length of that metal object. That is why large metal objects, like fridges, block Wi-Fi signal and create dead zones. The signal passes through the plastic casing of the receiving antenna and strikes the copper wire within. It then travels along the length of that wire, which leads to a wireless network adapter. The network adapter interprets the electronic pulse into data and passes it to the computer or router that it serves.


Radio waves pulse out like a series of ripples. The ripples have a pace and leave the transmitter at a regular rhythm. This is the frequency. "Frequency" means the number of waves, called "cycles," emitted per second and it is measured in hertz. Wi-Fi systems operate within the microwave band of frequencies. This range is measured in thousands of millions of cycles per second. A thousand million hertz is a gigahertz (GHz). Different Wi-Fi standards use different frequencies. The 802.11a system uses 5 GHz. The 802.11b and 802.11g systems use 2.4 GHz. The newest Wi-Fi system is called 802.11n and it uses both 2.4 GHz and 5 GHz.


Wi-Fi transmitters generate a carrier wave. This is a standard wave pulsing out at the system's frequency. The wireless network adapter converts computer data into an electronic pulse, which also has a wave form. It merges the data wave with the carrier wave for transportation. This is called "modulation." When the receiving network adapter gets the wave, it subtracts the carrier wave and converts the recovered data wave into binary data for the computer or router. This is called "demodulation."