RFexcitation

RF excitation refers to the introduction of energy at radiofrequency into a physical system to induce transitions, currents, or emissions. It is achieved by an RF source connected to a transmitter or probe, delivering a signal through an appropriate antenna, coil, or waveguide. The frequency range typically spans from kilohertz to gigahertz, with waveform parameters such as duration, amplitude, and phase shaping used to control the response of the system.

In magnetic resonance, RF excitation uses a transverse magnetic field produced by an RF coil at the Larmor frequency of the nuclei. This B1 field tips the net magnetization away from alignment with the static field. The resulting signal, detected by the same or another coil, carries information about the sample's structure and dynamics. Flip angles, bandwidth, and pulse sequences are designed to optimize sensitivity and minimize sample heating (SAR).

In electron spin resonance (ESR) or electron paramagnetic resonance (EPR), RF (often microwave) excitation drives transitions between electron spin states in a magnetic field. This enables spectroscopic information about electronic structure and local environment.

In RF engineering and telecommunications, excitation refers to applying a time-varying RF signal to an antenna, resonant circuit, or transmission line to produce electromagnetic radiation or to drive a system such as a mixer, amplifier, or sensor. Impedance matching, bandwidth, and phase stability are important considerations.

In plasma processing and material science, RF excitation powers plasmas or dielectric heating, allowing ionization or heating of gases for processes such as sputtering, etching, or coating. RF sources are chosen by frequency, power, and duty cycle to achieve the desired plasma characteristics.