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A modulator is a device or circuit that performs modulation. A demodulator (sometimes detector ) is a circuit that performs demodulation , the inverse of modulation. A modem (from mod ulator– dem odulator), used in bidirectional communication, can perform both operations.
In the Armstrong method, the audio signal and the radio frequency carrier signal are applied to the balanced modulator to generate a double sideband suppressed carrier signal. The phase of this output signal is then shifted 90 degrees with respect to the original carrier. The balanced modulator output can either lead or lag the carrier's phase.
The tank circuit (LC), connected to the collector via a capacitor, contains a pair of varicap diodes. As the voltage applied to the varicaps is changed, the phase shift of the output will change. Phase modulation is mathematically equivalent to direct Frequency modulation with a 6 dB/octave high-pass filter applied to the modulating signal ...
Balanced, symmetrical circuit. A balanced circuit will normally show a symmetry of its components about a horizontal line midway between the two conductors (example in figure 3). This is different from what is normally meant by a symmetrical circuit, which is a circuit showing symmetry of its components about a vertical line at its midpoint. An ...
For example, for a signal modulated with a linear modulation like amplitude modulation (AM), we can use a synchronous detector. On the other hand, for a signal modulated with an angular modulation, we must use a frequency modulation (FM) demodulator or a phase modulation (PM) demodulator. Different kinds of circuits perform these functions.
The mixer circuit can be used not only to shift the frequency of an input signal as in a receiver, but also as a product detector, modulator, phase detector or frequency multiplier. [6] For example, a communications receiver might contain two mixer stages for conversion of the input signal to an intermediate frequency and another mixer employed ...
Circuit diagram of an autotransformer balun using three taps on a single winding on a ferrite rod.. An ideal balun consists of two wires (primary and secondary) and a core: the current in the primary wire generates a magnetic field in the core, which in turn induces an electric field in the secondary wire.
Phase modulation (PM) is a modulation pattern for conditioning communication signals for transmission. It encodes a message signal as variations in the instantaneous phase of a carrier wave . Phase modulation is one of the two principal forms of angle modulation , together with frequency modulation .