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Pulsed radiofrequency is the technique whereby radio frequency (RF) oscillations are gated at a rate of pulses (cycles) per second (one cycle per second is known as a hertz (Hz)). Radio frequency energies occupy 1.0 × 104 Hz to 3.0 × 1011 Hz of the electromagnetic spectrum. Radio frequency electromagnetic energy is routinely produced by RF ...
This gives a net polarization that is parallel to the external field. Application of an RF pulse can tip this net polarization vector sideways (with, i.e., a so-called 90° pulse), or even reverse it (with a so-called 180° pulse). The protons will come into phase with the RF pulse and therefore each other. [citation needed]
A chirp is a signal in which the frequency increases ( up-chirp) or decreases ( down-chirp) with time. In some sources, the term chirp is used interchangeably with sweep signal. [1] It is commonly applied to sonar, radar, and laser systems, and to other applications, such as in spread-spectrum communications (see chirp spread spectrum ).
A radar system uses a radio frequency electromagnetic signal reflected from a target to determine information about that target. PRF is required for radar operation. This is the rate at which transmitter pulses are sent into air or space. Range ambiguity A real target in 100 km or a second-sweep echo in a distance of 400 km
Adiabatic radio frequency (RF) pulses are used in magnetic resonance imaging (MRI) to achieve excitation that is insensitive to spatial inhomogeneities in the excitation field or off-resonances in the sampled object. Nuclear magnetic resonance (NMR) experiments are often performed with surface transceiver coils that have desirable sensitivity ...
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz ). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio ...
Radiofrequency coil. Radiofrequency coils (RF coils) are the receivers, and sometimes also the transmitters, of radiofrequency (RF) signals in equipment used in magnetic resonance imaging (MRI). The MR signal in MRI is produced by the process of resonance, which is the result of radiofrequency pulses. They consist of two electromagnetic coils ...
Amplitude modulation ( AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in ...