Search results
Results From The WOW.Com Content Network
Figure 2 illustrates the approximation. The x-axis is the ratio τ 1 / τ 2 on a logarithmic scale. An increase in this variable means the higher pole is further above the corner frequency. The y-axis is the ratio of the OCTC (open-circuit time constant) estimate to the true time constant.
The cutoff frequency is found with the characteristic equation of the Helmholtz equation for electromagnetic waves, which is derived from the electromagnetic wave equation by setting the longitudinal wave number equal to zero and solving for the frequency. Thus, any exciting frequency lower than the cutoff frequency will attenuate, rather than ...
Roll-off enables the cut-off performance of such a filter network to be reduced to a single number. Note that roll-off can occur with decreasing frequency as well as increasing frequency, depending on the bandform of the filter being considered: for instance a low-pass filter will roll-off with increasing frequency, but a high-pass filter or ...
The cut-off frequency can be determined from the cut-off wavelength. From the sampling theorem, we know that for wavelengths smaller than 2 a {\displaystyle 2a} , or twice the sampling distance, every mode is a repeat of a mode with wavelength larger than 2 a {\displaystyle 2a} , so the cut-off wavelength should be at λ D = 2 a {\displaystyle ...
where is the wavelength expressed in millimeters and F # is the lens' focal ratio. As an example, a telescope having an f /6 objective and imaging at 0.55 micrometers has a spatial cutoff frequency of 303 cycles/millimeter. High-resolution black-and-white film is capable of resolving details on the film as small as 3 micrometers or smaller ...
Alpha cutoff frequency, or is the frequency at which the common base DC current gain drops to 0.707 of its low frequency value. The common base DC current gain is the ratio of a transistor's collector current to the transistor's emitter current , or α = i C i E {\displaystyle \alpha ={\frac {i_{C}}{i_{E}}}} .
The response value of the Gaussian filter at this cut-off frequency equals exp(−0.5) ≈ 0.607. However, it is more common to define the cut-off frequency as the half power point: where the filter response is reduced to 0.5 (−3 dB) in the power spectrum, or 1/ √ 2 ≈ 0.707 in the amplitude spectrum (see e.g. Butterworth filter).
f L is the lower cutoff frequency (-3 dB point) of the analysed system, measured in hertz. f H is higher cutoff frequency (-3 dB point) of the analysed system, measured in hertz. h(t) is the impulse response of the analysed system in the time domain. H(ω) is the frequency response of the analysed system in the frequency domain.