Modulator demodulator

Shortened for the term Modulator and Demodulator, this is a paired system that has revolutionized the global communication scenario, modulator demodulator. Thus, we will study modulation and demodulation in detail here. Much of the time, we need to regulate the signal to higher recurrence bands, we modulator demodulator refer to it as the radio frequency RF bands, to suit the spread attributes of the correspondence channels.

In electronics and telecommunications , modulation is the process of varying one or more properties of a periodic waveform , called the carrier signal , with a separate signal called the modulation signal that typically contains information to be transmitted. This carrier wave usually has a much higher frequency than the message signal does. This is because it is impractical to transmit signals with low frequencies. Generally, to receive a radio wave one needs a radio antenna with length of one fourth of wavelength. In radio communication , the modulated carrier is transmitted through space as a radio wave to a radio receiver. Another purpose of modulation is to transmit multiple channels of information through a single communication medium, using frequency-division multiplexing FDM.

Modulator demodulator

Modulation is a process generally used for radiating the low frequency audio signals for longer distances. Here the low frequency audio signal is superimposed with the high frequency carrier wave. The amplitude modulation is that where the amplitude of high frequency carrier wave is changed accordance with the intensity of the signal but the frequency of the modulated wave will be the same. This simple diode modulator delivers excellent results when used for high percentage modulation at low signal levels. Constants are shown for a carrier frequency of about 10 MHz, but, with a suitable tank, the circuit will give good results at any frequency at which the diode approximates a good switch. To extend frequency above that for which the IN is suited, a hot-carrier diode HP, etc. A shunt resistor across the tank circuit can be used to reduce the circuit Q so as to permit high percentage modulation without appreciable distortion. Recovering the original message from a modulated carrier is called demodulation and this is the main purpose of communications and telecommunications receivers. The circuit that is widely used to demodulate AM signals is called an envelope detector. As you can see, the rectifier stage chops the AM signal in half letting only one of its envelopes through the upper envelope in this case but the lower envelope is just as good. Importantly, as the envelope is the same shape as the message, the RC LPF's output voltage is also the same shape as the message and so the AM signal is demodulated. Envelope detector circuit uses a diode, a capacitor and a resistor and it is just like a half wave rectifier followed by a low-pass filter. It is a linear detector which takes high frequency RF signal as input and gives an output which is the envelope of the input signal. A diode detector is a type of envelope detector and is used for the detection of AM signal.

Related topics Technical audio Audio data compression Audio signal processing. The circuit that is widely used to demodulate Modulator demodulator signals is called an envelope detector.

A modem or broadband modem is a hardware device that connects a computer or router to a broadband network. For example, a cable modem and a DSL modem are two examples of these modems. Today, a "modem" often describes a broadband modem. However, it also describes what was initially considered a modem described below to connect to the Internet. To help prevent confusion, use the terms "broadband modem" and "dial-up modem. A broadband modem is an external device that connects to your computers and other network devices using a network cable or over a wireless connection. When sending a signal, the device converts "modulates" digital data to an analog audio signal and transmits it over a telephone line.

Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit or computer program in a software-defined radio that is used to recover the information content from the modulated carrier wave. The signal output from a demodulator may represent sound an analog audio signal , images an analog video signal or binary data a digital signal. These terms are traditionally used in connection with radio receivers , but many other systems use many kinds of demodulators. Demodulation was first used in radio receivers.

Modulator demodulator

A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more carrier wave signals to encode digital information , while the receiver demodulates the signal to recreate the original digital information. The goal is to produce a signal that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio. Early modems were devices that used audible sounds suitable for transmission over traditional telephone systems and leased lines. The rise of public use of the internet during the late s led to demands for much higher performance, leading to the move away from audio-based systems to entirely new encodings on cable television lines and short-range signals in subcarriers on telephone lines.

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A shunt resistor across the tank circuit can be used to reduce the circuit Q so as to permit high percentage modulation without appreciable distortion. Note The line quality of the phone line and how many collocations it must use also affects the modem's speed. Moreover, blind recognition of modulation type is an important problem in commercial systems, especially in software-defined radio. The primary 4 categories of the mechanism of Modulations are:. Asynchronous methods do not require a receiver reference clock signal that is phase synchronized with the sender carrier signal. Internet Archive. Contents move to sidebar hide. The amplitude modulation is that where the amplitude of high frequency carrier wave is changed accordance with the intensity of the signal but the frequency of the modulated wave will be the same. Touch-tone dialing would have been possible, but touch-tone was not universally available at this time. A null modem adapter is a small device with plugs at both ends which is placed on the termination of a normal "straight-through" serial cable to convert it into a null-modem cable. Automatic digital modulation recognition in intelligent communication systems is one of the most important issues in software-defined radio and cognitive radio. Recovering the original message from a modulated carrier is called demodulation and this is the main purpose of communications and telecommunications receivers. About half of all ISPs offered 56k support by October

The frequency of a radio frequency channel can be explained best as the frequency of a carrier wave. A carrier wave is purely made up of a constant frequency, slightly similar to a sine wave.

Article Talk. Tip To help prevent confusion with a broadband modem, refer to this modem as a "dial-up modem. Coaxial cable Fiber-optic communication optical fiber Free-space optical communication Molecular communication Radio waves wireless Transmission line telecommunication circuit. This led to a price war, and by the end of the year V. For example, a cable modem and a DSL modem are two examples of these modems. The second feature is the ability to quickly connect to one's ISP, achieved by remembering the analog and digital characteristics of the telephone line and using this saved information when reconnecting. Not to be confused with Computer Modern. They never utilize RS because they require high bandwidth channels to the host computers to carry the raw audio signals generated sent or analyzed received by software. A leased line modem also uses ordinary phone wiring, like dial-up and DSL, but does not use the same network topology. The internal modem shown above is an example of a PCI modem. The modem makes these noises and tones to transmit digital information over an analog line. Some pulse modulation schemes also allow the narrowband analog signal to be transferred as a digital signal i. The opposite is synchronous modulation.