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The Q factor is a parameter that describes the resonance behavior of an underdamped harmonic oscillator (resonator). Sinusoidally driven resonators having higher Q factors resonate with greater amplitudes (at the resonant frequency) but have a smaller range of frequencies around that frequency for which they resonate; the range of frequencies for which the oscillator resonates is called the ...
Q-meter E9-4. Internally, a minimal Q meter consists of a tuneable RF generator with a very low (pass) impedance output and a detector with a very high impedance input. There is usually provision to add a calibrated amount of high Q capacitance across the component under test to allow inductors to be measured in isolation.
The higher the Q factor of the inductor, the closer it approaches the behavior of an ideal inductor. High Q inductors are used with capacitors to make resonant circuits in radio transmitters and receivers. The higher the Q is, the narrower the bandwidth of the resonant circuit. The Q factor of an inductor is defined as
Series RL, parallel C circuit with resistance in series with the inductor is the standard model for a self-resonant inductor. A series resistor with the inductor in a parallel LC circuit as shown in Figure 4 is a topology commonly encountered where there is a need to take into account the resistance of the coil winding and its self-capacitance.
The quality of the resonance (how long it will ring when excited) is determined by its Q factor, which is a function of resistance: =. An idealized, lossless LC circuit has infinite Q , but all actual circuits have some resistance and finite Q , and are usually approximated more realistically by an RLC circuit .
The ultra-low electrical resistivity of a superconducting material allows an RF resonator to obtain an extremely high quality factor, Q. For example, it is commonplace for a 1.3 GHz niobium SRF resonant cavity at 1.8 kelvins to obtain a quality factor of Q=5×10 10. Such a very high Q resonator stores energy with very low loss and narrow bandwidth.
Radio transmitters use low-pass ... A resistor–inductor circuit or RL ... is the frequency scaling factor, and is the quality factor. Equation 1 describes three ...
These have the advantage of being very compact, but the low quality factor of the resonators leads to relatively poor performance. Lumped-Element LC filters have both an upper and lower frequency range. As the frequency gets very low, into the low kHz to Hz range the size of the inductors used in the tank circuit becomes prohibitively large.