Cell phones utilize non-ionising radio waves to transmit electrical signals that represent voice, text and data transmissions. Their technology keeps evolving to stay current.
The basic idea remains unchanged; microphones convert soundwaves to electrical signals that travel through a phone’s transmitter antenna to reach its base station antenna (cellphone mast or base station antenna). Here is how it works.
The microphone
When talking on a cell phone, the microphone converts sound energy into electrical signals that are then transformed into radio frequencies by the transmitter and sent through to a cell tower or cellphone mast where they are passed to other base stations in the mobile phone network, connecting callers with nearby phones and people.
A microphone works by vibrating diaphragms and carbon grains according to the pitch of your voice, with loud sounds causing more diaphragm vibration, which leads to tighter compression of carbon grains; in comparison, soft sounds cause less diaphragm vibration which subsequently squeezes them more gently together.
Your mobile phone contains a microchip that converts vibrations into digital signals containing zeros and ones. Once processed, these RF signals travel down your antenna before being picked up by another cell phone’s antenna, where they’re translated into voice calls, text messages or multimedia files for transmission through airwaves.
The transmitter
Just like landlines, mobile phones transmit and receive low-power radio signals through antennas on both ends – on both the phone itself and at its base station (refer Fig 3). For best performance, line of sight must exist between these antennas – hills, trees or tall buildings may obstruct it!
Once in the phone, a microchip converts the signal into strings of numbers which are then transformed into radio waves by an antenna and transmitted out into space to reach cell towers which then relay it along networks’ telephone lines.
. Each mobile phone contains a SIM card to store subscription and phone book data securely. When Emma calls John’s number on Emma’s phone, the Mobile Switching Center sends a request to his home cell tower which checks his IMSI from his SIM and broadcasts a message identifying itself before assigning an unoccupied frequency and transferring the link.
The antenna
An antenna is what allows mobile phones to communicate wirelessly with cellular networks. It translates electrical signals coming out of your phone into radio waves that are transmitted at specific frequencies over the network.
Your phone’s microphone converts your voice into digital signals that contain 0s and 1s. Your transmitter then uses these to encode onto a sine wave (see How Radio Works for more). Finally, this signal travels out through its antenna as electromagnetic radiation.
Signals travel until they reach a cell tower or cellphone mast, where it is passed onto a base station for further transmission to other mobile and fixed telephone networks as well as individual cells within the cellphone network. A phone can only connect with its base station if its signal strength meets minimum criteria indicated by its bars on your screen.
The base station
Your mobile phone’s microphone converts sound signals into electrical ones that are then processed by a microchip into numbers that are transmitted as radio waves through its transmitter antenna and eventually reach base stations or cellphone masts that form part of the network you use.
Cellphone networks span across wide areas, divided into smaller geographical zones known as cells. Each cell uses different frequencies from those around it in order to ensure there is no interference between calls.
As mobile phones require line of sight to connect with base stations, hills and tall buildings can sometimes create obstructions that prevent communication. Engineers therefore carefully plan each base station’s placement to provide maximum coverage in each given area.
Femtocells could soon provide you with your very own base station at home. Once connected to your Internet line, these miniaturized versions allow you to make and receive calls over your mobile provider’s network without relying on its larger network infrastructure.