A demodulator is a circuit that separates the signals of Amplitude Modulation (AM), Frequency Modulation (FM), and Quadrature Amplitude Modulation (QAM) from the numerous radio waves in our environment and decodes the information from the carrier. The most common form of demodulator used by consumers today is the superheterodyne receiver.
The superheterodyne receiver uses a combination of two circuits: a low-frequency amplifier called a first stage or baseband amplifier, and a high-frequency amplifier called a second stage or tuner amplifier. The first stage amplifies both the modulated signal and any adjacent channel interference. It then feeds its output into the input of the second stage, which has much higher gain than the first stage. The second stage amplifies only the signal from the first stage, which carries no energy at high frequencies. It then delivers this signal to an intermediate frequency (IF) stage, which filters out all but the modulated signal at the first stage's output. This final step is necessary because at first the modulated signal will be present at the same time as the unwanted sidebands, which must be separated out before decoding can begin.
The superheterodyne design allows for easy separation and amplification of different frequency bands, which is useful for separating out television channels from each other as well as interfering sources such as car engines.
Demodulation Separation of the original information, or SIGNAL, from the modulated carrier. In the case of amplitude or frequency modulation, a device known as a demodulator or detector generates a signal that corresponds to instantaneous changes in amplitude or frequency, respectively. These signals can then be further processed through electronic circuitry.
In radio technology, a demodulator is used to extract the original information from a modulated signal. The term "demodulate" has the same meaning in telecommunications as it does in radio technology: to remove modulation and return the signal to its original form.
An example would be if a radio transmitter broadcasts data by changing the amplitude of its waveform. This signal is then transmitted into the air where it is picked up by an antenna attached to a receiver. Inside the receiver, the demodulator uses electronics to remove the modulation (in this case, amplitude modulation) and give us back the original data signal: 0's and 1's. It does this by comparing the voltage of each pulse with a reference voltage and determining which peaks are higher than the reference level. If more pulses have peak values greater than the reference, the receiver will output a 1; otherwise, it will output a 0.
The demodulator also contains one or more oscillators that produce signals at precise frequencies depending on the type of modulation used by the sender.
Demodulation is the process of retrieving information from a carrier wave at the receiver, and the electrical circuit utilized for it is known as a demodulator. It is a type of electric circuit designed to recover information from a modulated carrier wave. The term "demodulator" has become generic for such a circuit.
In radio communication, modulation is used to transmit information from a sender (transmitter) to a receiver. The most common form of modulation is amplitude modulation (AM). In AM, the amplitude of an alternating current (AC) signal is varied to represent data. Amplitude modulation can be either positive or negative. If +10 volts is used as the maximum positive voltage and -10 volts as the maximum negative voltage, then a signal with a value of +5 volts would be represented by a line equal to +10 volts minus 5 volts or 55 volts. Lines of different lengths are used to separate different values of the signal.
The original form of modulation was frequency modulation (FM). In this case, the frequency of an oscillator is varied instead of its amplitude. Thus, the same signal can be transmitted over a wide range of frequencies. Modern FM uses heterodyning to combine two signals together: one from an oscillator and the other from a radio station. This creates a third signal at the difference frequency between these two sources.
Modulation is the process of changing data information on a carrier, whereas demodulation is the process of recovering original information at the far end of the carrier. A modem is a piece of equipment that can modulate and demodulate data. Modern communication systems often include both functions in one device called a demodulator/decoder (or simply decoder). For example, a modem used with digital cellular phones demodulates radio-frequency signals to recover data and provides an audio signal to the user while using energy from a battery instead of electricity from the public utility company.
Modems convert digital data into electrical signals which can be transmitted across a communications channel, and then converted back into digital form at the receiving station. The two main types of modems are analog modems and digital modems. An analog modem uses voltage levels to represent 0's and 1's while a digital modem uses electric pulses representing 0's and 1's.
Analog modems use various techniques for translating digital data into voltage levels suitable for transmission over telephone lines. These techniques include frequency modulation (FM), voice band modulation (VBM), amplitude modulation (AM), and hybrid modulation (e.g., AM/FM). Digital modems use electrical pulses to represent 0's and 1's. They convert received analog signals into digital form and transmit them to the other side of the connection.