Noise broadband

The Markov approximation, in which we assume that the correlation time of the EM field is much shorter than the timescale of radiation processes of the bare systems. This approximation is equivalent to the white-noise (broadband) description of the EM field modes, and allows us to replace p(f - x) by p(f). 

Pink noise broadband noise whose energy content is inversely proportional to frequency (-3dB per octave or -10 dB per decade). 

White noise broadband noise having constant energy per unit of frequency. 

J. L. Engle, "Low-noise broadband transmit/receive circuit for NMR," J. Magn. Resonance 37, pp. 547-549 (1980). 

Equipment modifications are needed for a white light bias (see optional equipment in Fig. 7.1). The experiment requires a low noise broadband DC illumination, while simultaneously illuminating the sample with chopped ( AC) monochromatic light. The waveform of the chopped monochromic light must be monitored to verify that the chopping speed is low enough for the sample response to reach steady state. The bias level should be set to 37 % of the expected j c [2-4]. 

Mori A., Kobayashi K., Yamada M., Kanamori T., Oikawa K., Nishida Y., and Ohishi Y, Low noise broadband tellurite-based Er -doped fibre amplifiers. Electron. Lett, 34,887-888 (1998). 

The noise levels of strong-motion accelerometers make estimating the self-noise of such sensors easier than typical low-noise broadband sensors (Fig. 2). Since the user community is generally only interested in strong motions with frequencies from a few Hz to a few tens of seconds period, it is often possible to resolve the selfnoise using relatively short testing intervals. 

Composite transducers will replace conventional transducers in applications where the improvement of test sensitivity, signal to noise ratio and axial resolution are mandatory. It must nevertheless also be noted in connection with the broadband feature that though composite probes have a specified nominal frequency, the echo signals allow no echo amplitude... 

Fig. 5, also an A-scan, shows the possibility of the echo-technique for concrete. The interface and backwall-echo of a 20 cm thick concrete specimen are displayed (RF-display). A HILL-SCAN 3041NF board and a broadband transducer (40mm element 0) are used which enable optimal pulse parameters in a range of 50 to 150 kHz. Remarkable for concrete inspections is the high signal-to-noise ratio of about 18 dB. 

Finding the values of G allows the determination of the frequency-domain spectrum. The power-spectrum function, which may be closely approximated by a constant times the square of G f), is used to determine the amount of power in each frequency spectrum component. The function that results is a positive real quantity and has units of volts squared. From the power spectra, broadband noise may be attenuated so that primary spectral components may be identified. This attenuation is done by a digital process of ensemble averaging, which is a point-by-point average of a squared-spectra set. 

Landstrom, U, Kjellberg, L., Soderberg, L., and Nord.strbm, B. (1991). The effects ot broadband, tonal and masked ventilation noise on performance, wakefulness and annoyance. /. Low Frequency Noise and Vibration 10(4). 

Broadband The wavefront sensor should be able to operate across a wide range of wavelengths. Often light is limited and it is important to use every available photon to minimize the noise. 

The noise-modulated broadband decoupled 13C NMR spectrum of (/)/.)-penicilla-mine is shown in Fig. 5. Two methyl carbons were found to resonate at chemical shifts of 27.7 and 30.2 ppm, in addition to a CH carbon at 64.6 ppm. Two quaternary... 

The basic components of the solid state spectrometer are the same as the solution-phase instrument data system, pulse programmer, observe and decoupler transmitters, magnetic system, and probes. In addition, high-power amplifiers are required for the two transmitters and a pneumatic spinning unit to achieve the necessary spin rates for MAS. Normally, the observe transmitter for 13C work requires broadband amplification of approximately 400 W of power for a 5.87-T, 250-MHz instrument. The amplifier should have triggering capabilities so that only the radiofrequency (rf) pulse is amplified. This will minimize noise contributions to the measured spectrum. So that the Hartmann-Hahn condition may be achieved, the decoupler amplifier must produce an rf signal at one-fourth the power level of the observe channel for carbon work. 

A Deconvolving Spectra with Broadband White Noise Added 195... 

Fig. 3 Effects of noise on deconvolution. Trace (a) is the original spectrum o(x), trace (b) the convolved spectrum i(x) displayed with no noise added. Traces (c)-(g) are the deconvolution results for broadband white-noise signal-to-noise ratios of oo 1, 580 1, 115 1, 60 1, 30 1, respectively.

For a broadband r.f. amplifier of bandwidth Afi sending a signal to a square-law diode detector and thence to a low-frequency video amplifier of bandwidth A/j the noise power is (Dicke 1946 Robinson 1974)... 

One of the more challenging unsolved problems is the representation of transient events, such as attacks in musical percussive sounds and plosives in speech, which are neither quasi-periodic nor random. The residual which results from the deterministic/stochastic model generally contains everything which is not deterministic, i.e., everything that is not sine-wave-like. Treating this residual as stochastic when it contains transient events, however, can alter the timbre of the sound, as for example in time-scale expansion. A possible approach to improve the quality of such transformed sounds is to introduce a second layer of decomposition where transient events are separated and transformed with appropriate phase coherence as developed in section 4.4. One recent method performs a wavelet analysis on the residual to estimate and remove transients in the signal [Hamdy et al., 1996] the remainder is a broadband noise-like component. 

Niedzwiecki and Cisowski, 1996] Niedzwiecki, M. and Cisowski, K. (1996). Adaptive scheme for elimination of broadband noise and impulsive disturbances from AR and ARMA signals. IEEE Trans, on Signal Processing, pages 528-537. 

All broadband spectra were amplified by a low-noise preamplifier with a dynamic range > 1,000, and a broadband main amplifier. The amplified time-domain signal is digitized by a 20 MHz, 9 bit Bruker ADC with 128 K words of buffer memory, and Fourier transformed by a Bruker array processor (128 K word FFT in 8 sec). 

In the broadband (low mass resolution) mode the only ion detected was the [M+H]+ ion, and in the narrowband mode a mass resolution of ca. 90,000 (resolution specified at FWHM) was obtained. Note also that the signal-to-noise ratio in the broadband mode is > 100 1 for a sample size of 100 pmol, and in the narrowband (high resolution) mode the signal-to-noise ratio is greater than 500 1. Owing to the pulsed ionization used for FTMS, the total ionization time required to produce this spectrum was approximately 80 ms. That is, the Cs+ ion beam was turned on for 4 ms to produce each mass spectrum and 20 individual ionization events were signal-averaged. 

The nep is usually expressed in units of WHz-1/2 (being specified for a particular frequency and unit bandwidth), or occasionally in W (being the ratio of broadband noise to responsiv-ity at a specified frequency). A figure-of-merit frequently used in the discussion of detector performance is the specific detectivity D, which is defined as ... 

In UV and visible vapor, bubbles cannot be tolerated in the sample, because they will generate noise in the optical reading, and if a pressurized cell is used, the cell pressure must be kept constant. Nitrogen or water is used to purge the cell, and interference or broadband filters are used for checking calibration. Photometers are normally used for single-component mea-... 

Coaxial cable is less sensitive to noise and is suited for higher transmission speeds than twisted-pair cable. Baseband techniques (serial bit-by-bit transmission) as well as (frequency modulated) broadband techniques are possible. Types of possible communication techniques in coaxial cables are listed in Table 9.2. 

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