A Newbie's Guide to Wireless Networks
How a basic radio works



 

The most common experience that most people have with RF is their AM/FM radio (or their television sets). Shown above is a diagram that briefly shows how a radio works. Try gliding your mouse over each of the components.

Transmitter Operation

Letís start with the transmitter or radio station where the RF signal originates.

Here, audio is first encoded using a modulation format Ė either AM or FM. AM stands for Amplitude Modulation. FM stands for Frequency Modulation. Modulation is the way data or audio is converted into a radio frequency signal. Actually, to save on electronic circuitry, the audio is initially converted into an intermediate radio frequency or IF signal.

 

From here, it is easily upconverted into the final RF frequency band or bands that are required.

 

Finally, the RF signal is amplified and sent to the transmitter antenna so that it can be transmitted over a broader area.

 

Receiver Operation

As for the receiver, your AM/FM radio or television set, just turn the process around.

You adjust your tuner to locate the desired RF signal (radio station or TV channel). This converts the RF signal back into a lower common IF signal. Again this saves on circuitry so you donít have to have separate circuitry for every channel or station.

 

The IF signal is then demodulated based on its modulation format (AM or FM). This decodes the radio frequency signal back into audio.

 

Finally, it is amplified, and if everything goes right you will hear music, news, or a (sometimes irritating) talk-show host.

 

Wireless Data Operation

So, how does this change for sending and receiving wireless data? Very simply, the source is a computer instead of audio. The destination is also a computer or computer network instead of a speaker. The signal is encoded and decoded using more exotic digital modulation formats like Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and others. The radio frequency bands that are used are different as determined by the FCC. And the maximum allowable transmission power is also restricted. Otherwise, it is all pretty much the same.

 

 


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