Band-pass filtering

Secondly, y/mariefi) is analytic, that is the corresponding band pass filter has no negative frequencies. This feature is of great help because it avoids interference in the analysis between positive and negative frequencies of the signal, which alters the representation understandability. 

Finally, the band pass filters corresponding to the Morlet wavelet have a "quicker" decrease towards null frequencies than filters obtained with the first derivative of gaussian wavelet (fig. 9). As a result, they... 

A hexapole assembly of rods (poles) is built similarly to the quadrupole, but now there are three sets of opposed rods evenly spaced around a central axis. The hexapole cannot act as a mass filter by applying a DC field and is used only in its all-RF mode. It is therefore a wide band-pass filter and is used to collimate an ion beam. (Like-charged particles repel each other, and an electrically charged beam will tend to spread apart because of mutual repulsion of ions unless steps are taken to reduce the effect.)... 

Fig. 4.57. Example of sensitive Raman equipment. The band pass filter, BP, cleans the laser radiation. The high NA objective lens LI focuses the laser on the sample and collects the Raman scattered radiation within a large solid angle. The band-rejection filter, BR, blocks elasti-...

In the gas correlation techniques, gas-filled cells mounted on a rotating disk cross the analyzing infrared beam in turn. One correlation cell is filled with a gas that will not absorb infrared light, such as nitrogen (N2). The other cell (or cells) are filled with a high concentration of the gas to be measured. The wavelength range is selected at the absorption band of the gas to be measured by an optical band-pass filter. 

Equation (3-307) also leads to a very important physical interpretation of the function Sx(f) namely, that Sx(f) describes the way in which the total power of X(t) is distributed in frequency. This comes about if we accept the physically reasonable definition that the power in X(t) contained in the frequency band /x < / < f2 is equal to the total power output of the ideal band-pass filter H(f) shown in Fig. 3-11, when X(t) is the input. Equation (3-307) now yields the result,... 

Band-pass filter A filter used for selecting the desired coherence order, p. Carrier frequency The transmitter frequency that consists of high-frequency pulses. 

Figure 13, Demonstrating that a narrow band pass filter will increase...

Monochromators. Replica gratings and narrow band-pass filters are used commonly, more so than quartz prisms. Computer control of the monochromator is available in some instruments, so that optimum intensity at the desired wavelength or maximum absorption by the examined substance can be obtained. 

Many other filter functions can be designed, e.g. an exponential or a trapezoidal function, or a band pass filter. As a rule exponential and trapezoidal filters perform better than cut-off filters, because an abrupt truncation of the Fourier coefficients may introduce artifacts, such as the annoying appearance of periodicities on the signal. The problem of choosing filter shapes is discussed in more detail by Lam and Isenhour [11] with references to a more thorough mathematical treatment of the subject. The expression for a band-pass filter is H v) = 1 for v j < v < else... 

Burdick and Jackson). All solutions were photolyzed to less than 5% conversion in a standard 3 ml capacity, 1-cm path length quartz cell. Samples were irradiated with a 450-Watt medium pressure, Hanovla mercury lamp focused through an appropriate band-pass filter (280 nm or 254 nm) onto the 1-cm quartz cell with the requisite solution. Test solutions could be purged with either helium or oxygen using a needle valve assembly attached to the tapered quartz cell neck. The loss of carbamate due to photolysis and the amounts of known photoproducts were determined quantitatively by GC using eicosane as an internal standard. The columns were 6 stainless steel containing Carbowax 20M on chromosorb G. 

Figure 7 (A) A circuit diagram for a 180-MHz band-pass filter used for extracting...

Fig. 1 Scheme of the OCT system. SLD—superluminescent diode FBS—fiber-optic beam splitter M—mirror L—lenses S—sample PD—photo-diode F—band-pass filter A— logarithmic amplifier AD—amplitude detector ADC—analog-to-digital converter PC— computer. 

The signal supplied by cryogenic sensors is very low (in the order of jlV). The white noise voltage is proportional to the frequency bandwidth. To reduce the bandwidth, low-pass filters (carachteristographers with 0.01 Hz cut-off) or band-pass filters (lock-in) are used. The former method is more precise, but a longer time for the measurements is required. 

Since the filter is low pass, it will attenuate all the frequencies far from the reference frequency, that is, the multiplier together with the low-pass filter acts as a band-pass filter centred at the reference frequency coR. The bandwidth of such band-pass filter is the double of the bandwidth of the low-pass filter (see Fig. 10.9). This result will be used in the evaluation of the residual noise in the output signal. 

The noise in the output signal is that present in the bandwidth (1/2r) of the band-pass filter. If the power noise spectrum at the input is white (flat) and given by wn(f)9 the lock-in output noise will be simply ... 

Note about infrared radiation (IR) filters In the bolometer just described, the optimum conductance to the heat sink is G 2 x 10-10 W/K. This means that an absorbed power of the order of 1(T10 W saturates the bolometer. Since the bolometer is a broad-band detector, it would receive, e.g., a power of the order of 10 7 W from a 30 K black body. Of course, optical filtering is needed to reduce the bandwidth of the impinging radiation. Filtering takes usually place in several steps a room temperature filter eliminates visible light an intermediate temperature filter (at about 77 K) rejects the micron wavelengths, whereas the submillimetre or millimetre filter is made up of a low-pass and an interference band-pass filter. 

Irradiations and dose measurements were performed through 254 nm band pass filters. 

The resist was exposed with an in-house i-line reduction projection aligner or a 600-W Xe-Hg lamp (Cannard Hanovia) in conjunction with a UVD2 band pass filter (Toshiba glass Co.). After removing the top layer by rinsing in water, the resist was developed with a 2. 38 wt% tetramethylammonium hydroxide aqueous solution. 

Figure 5. Dependence of rate of dissolution of 5pM Y-FeOOH in pH 4.0, 0.01M NaCl on concentration of a) tartaric acid, and b) salicylic acid. Fitted parameters obtained for rectangular hyperbolic model are given. Light source mercury arc lamp with 365nm band-pass filtering.

Table II. Measured and Fitted Parameters Obtained in Studies of the Photodissolution of f-FeOOH Suspended in pH 4, 0.01M NaCl Containing Various Organic Acids. Illumination provided by a Hg arc lamp source and 365 nm band-pass filter (total radiation output 85 pE cm-2 min- ).

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