The interconnectedness of the world doesn't only rely on underwater cables. It also heavily relies on radio waves. Although cables were the first solution to connect the world, radio waves were the solution that made this solution convenient. Made up of peaks and valleys, radio waves travel just like when you throw a rock so that it bounces off the surface of the water until it drowns.
Except with radio waves, you get a continuous output that ends when you cut off the signal. Radio waves take up a large portion of the electromagnetic spectrum with frequencies ranging from 1 KHz (kilo-hertz) up to 100 GHz (gigahertz). But radios aren't the only devices that have been using radio waves, our phones and Wi-Fi routers are just some of the everyday devices that rely on radio waves. But how does the exchange of radio waves actually work?
Wireless Transmitters & Receivers
What Are They?
In order for radio waves to be generated and sent out, you need a wireless transmitter. A transmitter is referred to as a telecommunications device that makes use of an antenna. A proper transmitter and receiver work together since, without even one of these components, the transfer of radio signals isn't possible. Even if you have many wireless transmitters, if you don't use wireless receivers, the signals will all be sent out for nothing.
How They Work?
Wireless transmitters work by having an alternating current flowing through a conductor. This current is what creates radio signals as it changes direction, which it does so rather quickly. This change in direction creates electromagnetic radiation in the form of sinusoidal frequency. A receiver works a lot simpler than a transmitter. Wireless receivers can be any large metal object. But that metal surface needs to be able to have the signals pass through a plastic casing and to a copper wire. This wire is what leads the signal to an adapter, which helps interpret the wave into data.
Types of Transmitters
AM
As you probably already know, there are AM and FM radio waves, with AM having a frequency range between 540 and 1700 KHz and an IF (intermediate frequency) of 455 KHz. An AM transmitter relies on amplitude modulation in order to convert audio information into a signal, hence the name. This type of transmitter has the modulating signal being the audio as well as a high-frequency signal as the carrier. This output is achieved thanks to the amplitude of the carrier signal being one that is varied by the amplitude of the modulating audio signal.
FM
The more common way of broadcasting radio waves involves an FM transmitter. This type of transmitter has a frequency range between 88 and 108 MHz and an IF of about 10.7 MHz. In order for an FM transmitter to convert audio information into a modulated signal, it relies on frequency modulation. This process involves varying the frequency of the carrier signal according to the amplitude of the modulated audio signal. A high-frequency signal is used as the carrier for an FM transmitter, just like an AM transmitter.
SSB
An SSB transmitter is similar to an AM transmitter, but it is more power-efficient as well as being able to save more bandwidth. This is because an SSB transmitter has both the upper and lower sidebands transmitted by an AM transmitter. The upper band is the sum of the carrier and modulating signal, with the lower band representing the difference between the carrier and modulating signal. A single sideband SSB transmitter broadcasts either the upper or dual sideband, it can't do both.
Direct Conversion
With a direct conversion transmitter, a signal is generated that is known as QPSK, or quadrature phase-shift keying. This process is the first part of the data transmission, which involves dividing Q and I signals, which are processed by a DAC. As a result, low pass filtering is used to send the signal from the DAC to the mixers. A direct conversion transmitter also phase-shifts a LO (local oscillator) signal by 90°. The I and Q signals are mixed and then added together, which results in a modulated QPSK signal. Before the signal is broadcast, it is amplified with a power amplifier.
Super Heterodyne
A super heterodyne transmitter is an addition to a direct conversion transmitter. The latter obtains the modulated signal and introduces one or multiple mixing components. Before and after mixing, the signal gets bandpass filtered. Before transmission, a super heterodyne transmitter like a direct conversion transmitter ruses a power amplifier. An AGC (automatic gain control) is used by a super heterodyne transmitter to change the amplitude of the signal it sends.
Conclusion
Radio waves are like a volleyball being passed from one side to another without the ball being thrown back. The opposing teams represent the transmitter and receiver. Understanding this simple analogy will help you understand how every wireless communication device operates, be it one at home or out in the open.
