What is a Radio Modulation : Types & Techniques

For a radio signal to carry information, it must be varied or modulated – there are various types of modulation, each best in different situations.

What is Modulation?

Modulation is the technique that involved the two signals for the modulation process.
The message is also called a baseband signal and this baseband signal is representing the original signal which is the band of frequencies.
This original signal is to be transmitted to the receiver and the frequency of the signal is usually low.
The other signal interacts with a high-frequency sinusoidal wave, this signal is known as the carrier signal.
The carrier signal frequency is always higher than that of the original signal.
The baseband signal amplitude is transferred to the high-frequency carrier.
Therefore, modulation can be defined as, the process of superimposing a low-frequency signal on a high-frequency carrier signal.

There are three types of modulation.

Amplitude modulation (AM) is a modulation technique that is used in electronic communication for transmitting messages with a radio wave.
In AM, the amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal.
The AM modulation index is a measure based on the ratio of the modulation excursions of the RF signal to the level of the unmodulated carrier.
The amplitude modulation is the peak change in the RF amplitude from its unmodulated value. The modulation index is normally expressed as a percentage and may be displayed on a meter connected to an AM transmitter.

Broadcast Transmissions: AM is used in broadcasting transmission over the short, medium, and long wavebands. Since AM is easy to demodulate radio receivers for amplitude modulation are therefore easier and cheaper to manufacture.
Air-band radio: AM is used in the VHF transmissions for many airborne applications such as ground-to-air radio communications or two-way radio links for ground staff personnel.
Single sideband: Amplitude modulation in this form is used for HF radio links or point-to-point HF links. AM uses a lower bandwidth and provides more effective use of the transmitted power.
Quadrature amplitude modulation: AM is used extensively in transmitting data in several ways including short-range wireless links such as Wi-Fi to cellular telecommunications and others.

The category of angle modulation in which the frequency of the carrier wave is changed according to the amplitude of the message signal is known as frequency modulation.
The technology is used in telecommunications, radio broadcasting, signal processing, and computing.
It is widely used in analog modulation techniques.
In frequency modulation both amplitude and phase of the carrier wave are unchanged and the only frequency can change the wave.

The above figure shows the modulating signal that has to be transmitted.
The second wave is the carrier wave and the frequency is varied according to the amplitude of the modulating signal.
The last one is the frequency modulated signal that is transmitted after modulation is done.

It is used in radio signal broadcasting.
During satellite and microwave communication, frequency modulation is widely used.
It has extensive applications in cellular radio communication and TV sound transmission.

Phase Modulation can be defined as the Phase of the carrier (Ø) signal being varied proportionally to the Amplitude of the input modulating signal.
It is the angle modulation in which the phase of the carrier wave is changed according to the amplitude of the modulating signal.
In phase modulation of an analog signal, the phase change is a continuous back-and-forth movement.
The phase modulation of the digital signal is generally known as phase shift keying.

Phase modulation is used in the transmission of radio waves. This process is also employed in wireless signal transmission like satellite and Wi-Fi transmission etc.