Changing the radio waves traveling between the reader and the transponder in ways that enable the transmission of information.

Waves be changed in a variety of ways that can be picked up by the reader and turned into the ones and zeroes of binary code.

Waves can be made higher or lower (amplitude modulation) or shifted forward (phase modulation).

The frequency can be varied (frequency modulation), or data can be contained in the duration of pulses (pulse-width modulation).

1. The transmission of a signal by using it to vary a carrier wave; changing the carrier's amplitude or frequency or phase.
2. The fact of changing in some characteristic way the amplitude, frequency, or phase of a wave, or the velocity of the electrons in an electron beam.
3. A manner of speaking in which the loudness or pitch or tone of the voice is modified.
4. The rise and fall of the voice pitch.
5. A musical passage moving from one key to another.
6. Etymology: "act of singing" or "making music", from Old French modulation, "act of making music"; from Latin modulationem, modulatio, "rhythmical measure, singing and playing, melody"; from modulatus, modulari, "to regulate, to measure off properly"; from Latin modulus, "small measure".

In acoustical engineering, a type of amplitude modulation that couples a variable-impedance device; such as, a microphone, to the output stage of a radio transmitter.

Energy is thus absorbed from the transmitter according to the information captured by the microphone.

The deliberate processing of a carrier signal which is used in ordinary radio and TV broadcasting: The amplitude modulation varies in accordance with the level of the modulating signal while transmitting the video portion of a television signal.

Variation of the amplitude modulation of a carrier wave, commonly a radio wave, presents fluctuations in the audio or video signals that are being transmitted.

A higher amplitude modulation wave is interpreted as a "1" and a normal wave is interpreted as a zero.

The method of changing an amplitude modulation is known as "amplitude shift keying", or ASK.

The modulation (variation of amplitude or frequency) of the phase of a light wave; such as, by changing the index of refraction and the velocity of propagation and hence the phase at a point in the medium in which the wave is propagating, in accordance with an applied field serving as the modulating signal.

1. The instantaneous variation of the frequency of a carrier wave in response to changes in the amplitude of a modulating signal, which provides a more static-free transmission of radio waves than AM (amplitude modulation) broadcasting.
2. Variation of the frequency of a carrier wave (commonly a radio wave) in accordance with variations in the audio signal being sent.

Developed by American electrical engineer Edwin H. Armstrong in the early 1930's, FM is less susceptible to outside interference and noise; such as, thunderstorms, nearby machinery, etc. than is AM.

Such noise generally affects the amplitude of a radio wave but not its frequency, so an FM signal remains virtually unchanged.

FM is also better able to transmit sounds in stereo than AM and commercial FM broadcasting stations transmit their signals in the frequency range of 88 megahertz (MHz) to 108 MHz.

A measure of the efficiency of an imaging system in transferring the details of an object to those of the image.

1. A type of electronic modulation in which the phase of a carrier wave is varied in order to transmit the information contained in the signal.
2. Varying the angle of a wave in a carrier in order to transmit analog or digital data.

For digital signals, phase modulation (PM) is widely used in conjunction with amplitude modulation (AM); for example, quadrature amplitude modulation (QAM) uses both phase and amplitude modulation to create different binary states for transmission.