Terms used by Electrical Engineers
"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

AM Receiver

AM Receiver Functions
AM Receiver Block Diagram

An AM receiver is made up of the major elements shown in the block diagram above. The links are used to provide a more in depth definition of the terms used in the discussion. The system is set up to receive and detect an Amplitude Modulated Signal. An Amplitude Modulation system varies the amplitude of the carrier in step to the amplitude changes of a modulating signal. The variation in the amplitude of the signal is the intelligence, while the carrier is used to transmit the information.

The Antenna of course receives the AM signal over the air waves. The received AM signal is then feed to a low noise RF amplifier, which amplifies the signal. An RF amplifier is a wide-band amplifier operating in the RF frequency range.

A Local Oscillator is used within the AM receiver to generate a fixed frequency which is feed to an RF mixer along with the amplified RF signal. The Mixer combines the two signals and outputs an amplitude modulated signal at the frequency of the IF carrier.

The IF carrier frequency is the difference frequency between the RF carrier frequency and the local oscillator frequency [shown as Oscillator Wave]. The lower frequency IF signal is used to reduce the complexity of the follow-on circuitry. The IF amplifier is again used to amplify the signal, now at a lower frequency, which is then sent to the Detector.

The detector [or AM detector] is used to decode the signal envelope or amplitude modulation from the incoming IF. Other names used for the detector include envelope detector and diode detector. In the simplest form of an envelope detector only three components are required; a diode, resistor and a capacitor. The diode only allows the positive portion of the signal through, rectifying the signal. The capacitor filters signal removing the IF component or carrier. The result is the amplitude modulated portion of the signal or the audio signal.

The audio signal this then input to an AF amplifier, or audio frequency amplifier. The Audio Amplifier amplifies the signal to a point that will drive a speaker. Like any system, the Speaker will very depending on the needs of the device.

Also refer to the definition of Superheterodyne Receiver.

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