The frequency of a Radiofrequency channel can be explained best as the frequency of a carrier wave. A carrier wave is purely made up of constant frequency, slightly similar to a sine wave. It does not carry much information that we can relate to data or speech. The concepts of Amplitude Modulation, Modulation and Demodulation, along with their differences is explained below.
To involve data information or speech information, another wave has to be imposed known as input signal above the carrier wave. This process of imposing an input signal on a carrier wave is known as modulation. Put differently; modulation modifies the shape of a carrier wave to encode the data information that we intended on carrying. Modulation is similar to hiding a code in the carrier wave.
Types of Modulation
There are three types of modulation namely:
- Frequency modulation
- Amplitude modulation
- Phase modulation.
It is a kind of modulation where the amplitude of the carrier signal is changed in proportion to the message signal while the phase and frequency are kept constant.
This is the modulation where the phase of the carrier signal is altered according to the low frequency of the message signal is called phase modulation.
In this modulation the frequency of the carrier signal is altered in proportion to the message signal while the phase and amplitude are kept constant is called frequency modulation.
Modulation mechanisms can also be digital or analogue. An analogue modulation scheme has an input wave that changes like a sine wave continuously, but it is a bit more complicated when it comes to digital. The voice sample is considered at some rate and then compressed into a bit (the stream of zeros and ones). This, in turn, is made into a specific type of wave that is superimposed on the carrier.
What is Demodulation?
Demodulation is defined as extracting the original information-carrying signal from a modulated carrier wave. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. There are different types of modulation and so are demodulators. The output signal via demodulator may describe the sound, images or binary data.
Difference between Modulation and Demodulation
- Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier.
- A modem is an equipment that performs both modulation and demodulation.
- Both processes aim to achieve transfer information with the minimum distortion, minimum loss and efficient utilization of spectrum.
Even though there are different methods for modulation and demodulation processes, each has its own advantages and disadvantages. For example, AM is used in shortwave and radio wave broadcasting; FM is mostly used in high-frequency radio broadcasting, and pulse modulation is known for digital signal modulation.