Cutoff frequency

Transducers twelve 375 kHz resonant transducers have been used, with a 350 kHz cutoff frequency high pass filter section and a 40 dB preamplifier. 

After the signal emerges from the lock-m amplifier it still contains a considerable amount of noise. Most of the noise contributions to the signal can be eliminated by passing the signal tlirough a low-pass filter. The filter tune constant is a measure of the cutoff frequency of the filter. If accurate linewidth and g-factor... 

When used for superresolution, the laser beam is incident on b, which hides the domains in s. During read-out, b is heated and the domains in s are copied to b. The optical system sees only the overlap area between the laser spot and the temperature profile which is lagging behind, so that the effective resolution is increased. Experimentally it is possible to double the linear read-out resolution, so that a four times higher area density of the domains can be achieved when the higher resolution is also exploited across the tracks. At a domain distance of 0.6 pm, corresponding to twice the optical cutoff frequency, a SNR of 42 dB has been reached (82). 

The frequency response or switching speed of the bipolar transistor is governed by the same processes which control the speed of thep—n junction, the capacitance associated with the movement of charge into and out of the depletion regions. To achieve high frequencies the dimensions of the active areas and parasitic circuit elements must be reduced. The two critical dimensions are the width of the emitter contact and the base thickness, W. The cutoff frequency,, is the frequency at which = 57 / - b /t > where is the emitter-to-coUector delay time and is the sum of the emitter... 

After the anticipated disturbing frequencies have been determined, it is necessary to begin the sizing of the filter system. The cutoff frequency should be set at least one cycle per second below the lowest frequency to be filtered. The base frequency is determined from compressor speed and should be determined at the lowest anticipated compressor speed for variable-speed compressors. The following equation is used to determine cut-off frequency for a low-pass filter ... 

Service Goal. A goal for line service in terms of ton-miles between cutoffs should be selected. This value can initially be determined from Figures 4-84 and 4-85 and later adjusted in accordance with experience. Figure 4-86 shows a graphical method of determining optimum cutoff frequency. 

When performing optical simulations of laser beam propagation, using either the modal representation presented before, or fast Fourier transform algorithms, the available number of modes, or complex exponentials, is not inhnite, and this imposes a frequency cutoff in the simulations. All defects with frequencies larger than this cutoff frequency are not represented in the simulations, and their effects must be represented by scalar parameters. 

A crude way to eliminate noise amplification is to use a suitable cutoff frequency UcutofT and to write the solution as ... 

Figure 3a. Restored image using a simple cutoff frequency (Wcutofi = 80) in the deconvolution.

In the case of nonrelativistic laser intensity, linear theory does not allow propagation in overdense plasmas, namely when to 1 < iop(. = e(An/rn,.) 2n,J 2. In the extreme case of ultra-relativistic laser intensity (ao 2> 1), the cutoff frequency for propagation drops from u pe down to wpe/(l Tag)1/4 [11], where ao = eA/mec is the dimensionless amplitude of the laser field. Then, in order for the propagation to occur at plasma density appreciably higher than the ordinary critical density, ao 2> 1 is needed. This is also the case of overdense thin plasma layers (as proved by simulation [12]) whose thickness exceeds the skin penetration depth of the e.m. wave. Theoretical background and basic... 

This equation only accounts for the high cutoff frequency a> c (colc = Knqjc/1)), and diverges as co— -O. When the high- (ft>() and low-frequency (ft)/) cutoffs are taken into account, one obtains for smectogens... 

Because the dispersed acoustic function 3.69, the optic continuum function 3.71, and the Einstein function 3.73 may be tabulated for the limiting values of undi-mensionalized frequencies (see tables 1, 2, 3 in Kieffer, 1979c), the evaluation of Cy reduces to the appropriate choice of lower and upper cutoff frequencies for the optic continuum (i.e., X/ and limits of integration in eq. 3.71), of the three... 

The bias observed between experimental measurements and Kieffer s model predictions is due to the relative paucity of experimental data concerning cutoff frequencies of acoustic branches, and also to the assumption that the frequencies of the lower optical branches are constant with K and equivalent to those detected by Raman and IR spectra (corresponding only to vibrational modes at K = 0). Indeed, several of these vibrational modes, and often the most important ones, are inactive under Raman and IR radiation (Gramaccioli, personal communication). The limits of the Kieffer model and other hybrid models with respect to nonempirical computational procedures based on the equation of motion of the Born-Von Karman approach have been discussed by Ghose et al. (1992). 

Even if a very careful layout design is made, a stray capacitance of Cfb = 0.5 pF is common. With = 100 Mfl, using Eq. (11.10), the -3 dB cutoff frequency is estimated to be / 3 kHz. For most applications in STM, a gain of IV/lnA is desirable. A one-stage current amplifier requires a feedback resistance of IGO. The -3 dB cutoff frequency would be about 0.3 kHz, which is too low. 

Fig. 11.2. Broad-band current amplifiers, (a) By replacing the feedback resistor in Fig. 11.1 with a resistor network, the cutoff frequency of the amplifier can be greatly increased, but the Johnson noise is increased, (b) Broad-band current amplifier with a compensation capacitor. By introducing a condensation capacitor C2, the effect of Q can be reduced. Under the condition CiRi = C2R2, the frequency range is substantially expended. The Johnson noise is not affected.

Another limiting factor is the bandwidth of the op-amp. On the factory specifications, the commonly used indicator is the gain-bandwidth product. The nominal dc gain is valid up to a cutoff frequency / which is typically 10 Hz. Above that frequency, the gain g is inversely proportional to the frequency. The product of gain and frequency, the gain-bandwidth product/a is typically 1 MHz. The input impedance of the amplifier increases with frequency ... 

In this expression 1 is the cutoff frequency above which the data contain no information about o(x) that is, I( Q. We see that the sharpness criterion is a measure of the steepness of the solution o(x). The previous criterion, expression (40), is replaced with a sum of two terms. It includes both the mean-square-error criterion and sharpness. The filter is then sought that minimizes... 

Equation (4.65) provides the maximal change of R achievable by an external perturbation, since it does not involve any averaging (smoothing) of G(m) incurred by the width of Ffa>) the modified/ can even vanish, if the shifted frequency is beyond the cutoff frequency of the coupling, where G(m) = 0 (Figure 4.6d). 

Aperiodic DD sequences such as Uhrig dynamical decoupling (UDD) [55] suppress low-frequency components (to the left of the main peak) in the system spectrum, which retain the system-bath coupling even if the main peak of the system spectrum has been shifted beyond the bath cutoff frequency (Figure 4.11). The plots indicate that this suppression of low-frequency components is achieved at the price of a smaller shift of the main peak, that is, shifting the main peak beyond a given cutoff requires more pulses in UDD than in FDD. Note that optimized DD sequences with improved asymptotics exist [91], which we will not consider here. 

The Chebyshev filter offers higher attenuation and a steeper roll-off near the cutoff frequency than the Butterworth filter. There is a tradeoff to achieve the higher attenuation. The cost of utilizing a Chebyshev filter is higher values of Q, which leads to difficulties in hardware realization, and nonlinear phase characteristics, which can result in difficulties in predicting circuit performance. 

Fig. 5.8 Black body radiative transfer signals in Na located between parallel conducting plates for 29d —> 30p (left-hand side) and 28d —> 29p (right-hand side) as a function of the absorption frequency. The cutoff frequency is vc = 1/2d = 1.48 cm-1, where d is the plate separation. The increase in the transfer rate at v = vc (left-hand side) is due to the "switching on of the radiation polarized parallel to the plates (from ref. 24).

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