Quadrature amplitude modulation tutorialspoint

Modulation Applications

There are several variances between analog and digital transmission technologies and it is crucial to comprehend how conversions between the two technologies occur. An analog signal is describe as being constantly variable along amplitudes and frequencies. On the other hand, digital transmissions is very different from its analog transmissions. One difference is the signal is considerable simpler. Rather than being constantly a variable wave form, it is a series of separate pulses that represent one and zeros. As for example, each computer utilizes a coding scheme that outlines what arrangement of ones and zeros create all characters in a character set, which includes upper and lower case letters, special characters, and keyboard control functions (Goleniewski, 2015). Furthermore, there are many technologies covert the two signals on both directions, meaning analog-to-digital and digital-to-analog. This is the case of a two converters DAC and ADC technologies. An ADC is the device that coverts or transforms a continuous physical quantity (voltage) to a digital number that presents the quantity’s amplitude. ADCs covers digital data into an analog signal such as a current or voltage. These converters are found on most electronic devices that plug to the electric outlet. They are microchips integrated on the circuit board of the electronic device.

There are several types of modulation applications. These applications are amplitude, frequency, phase and QAM modulation. They all serve different but important purposes. Along with these purposes there are also advantages and disadvantages.

Amplitude modulation (AM) is used in a variety of applications. Although use of the modulation is not relied upon currently as it was used in the past, you can still find it in its basic form. When an AM modulated signal is created, the amplitude of the signal is varied in line with the variations in intensity of the sound wave. AM is the most straightforward way of modulating a signal. Some of the advantages are, it is simple to implement, an AM signal is efficient in terms of its power usage, and it can be demodulated using a circuit consisting of a very few components. Disadvantages are AM signals are prone to high levels of noise because most noise is amplitude based and AM detectors are sensitive to it.

Frequency Modulation (FM) is used in a wide variety or radio communication applications from broadcasting, two way radio communications links, and mobile radio communications. It possesses many advantages over AM. For example, it is resilient to noise. FM that has been utilized by the broadcasting industry is the reduction in noise. FM Does not require linear amplifiers in the transmitter. Disadvantages are it requires more complicated demodulator. Some other modes have higher data spectral efficiency.

Phase Modulation (PM) is a form of modulation that can be used for radio signals used in a variety of radio communications. PM and FM are closely linked together and it is often use in many transmitters and receivers used for a variety of radio communications. Pm works by modulating the phase of the signal. PM advantages are easily compared to FM. They both are used in determining velocity of moving target by extracting Doppler information. Doppler information needs stable a carrier which is possible in PM but not in FM.

Quadrature Amplitude Modulation, also known as QAM, has the advantage that increases the efficiency of transmission because it uses both amplitude and phase variations in radio communications. The disadvantages are that lower levels of noise are needed to move the signal to a different decision point. This noise can be a problem with QAM. QAM also contains an amplitude component and a linear amplifier is needed for transmission. The use of linear amplifiers consumes more power and is less desirable for mobile applications.

Many different systems are used in the process of networking to optimize communication between digital devices. Because that communication often must travel in the form of analogue signals, each of those systems have various techniques used for modulating and demodulating those signals in order to transmit the data required. Here are a few examples of common systems and the modulation techniques which they employ. A 56K modem uses a combination of two modulation techniques. The first is PCM or Pulse Code Modulation. This technique utilizes sampling processes in order to translate all signals to binary. The second technique is QAM or Quadrature Amplitude Modulation. QAM uses two AM or Amplitude Modulated signals, and combines them into one channel to double the effective wavelength. ADSL also uses QAM, intertwining two AM signals into a single channel.