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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.
Frequency modulation and phase modulation are the two complementary principal methods of angle modulation; phase modulation is often used as an intermediate step to achieve frequency modulation. These methods contrast with amplitude modulation , in which the amplitude of the carrier wave varies, while the frequency and phase remain constant.
Edwin Howard Armstrong (December 18, 1890 [2] – February 1, 1954 [3]) was an American electrical engineer and inventor who developed FM (frequency modulation) radio and the superheterodyne receiver system.
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 .
The Armstrong oscillator [1] (also known as the Meissner oscillator [2]) is an electronic oscillator circuit which uses an inductor and capacitor to generate an oscillation. The Meissner patent from 1913 describes a device for generating electrical vibrations, a radio transmitter used for on–off keying .
The phase modulation (φ(t), not shown) is a non-linearly increasing function from 0 to π /2 over the interval 0 < t < 16. The two amplitude-modulated components are known as the in-phase component (I, thin blue, decreasing) and the quadrature component (Q, thin red, increasing).
A 'signal space diagram' is an ideal constellation diagram showing the correct position of the point representing each symbol. After passing through a communication channel, due to electronic noise or distortion added to the signal, the amplitude and phase received by the demodulator may differ from the correct value for the symbol. When ...
DSB-SC is basically an amplitude modulation wave without the carrier, therefore reducing power waste, giving it a 50% efficiency. This is an increase compared to normal AM transmission (DSB) that has a maximum efficiency of 33.333%, since 2/3 of the power is in the carrier which conveys no useful information and both sidebands containing identical copies of the same information.
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