Frequency, carrier negative

As long as in the presence of negative velocity values, the absolute value of Af does not exceed the carrier frequency/q, i.e., fg> A/1, the resulting frequency of the detector output signal correctly preserves the directional information (sign) of the velocity vector. In the case of a vibrating object where v(t)=v the bandwidth of the modulated hetero-... 

These results led us to analyze the relationship between carrier-wave frequency and power density. We developed a mathematical model (6) which takes into account the changes in complex permittivity of brain tissue with frequency. This model predicted that a given electric-field intensity within a brain-tissue sample occurred at different exposure levels for 50-, 147-, and 450-MHz radiation. Using the calculated electric-field intensities in the sample as the independent variable, the model demonstrated that the RF-induced calcium-ion efflux results at one carrier frequency corresponded to those at the other frequencies for both positive and negative findings. In this paper, we present two additional experiments using 147-MHz radiation which further test both negative and positive predictions of this model. 

Very few results are available to test this mathematical model. Circumstances have lead to two tests comparing a negative and a positive finding at 1A7 MHz with results at A50 MHz. One test was performed at 50 MHz (3.6A mW/cm2) to test a prediction of this model based on the result of 147 MHz (0.83 mW/cm2). All these tests have provided results that agree with the model. In this paper, we describe the results of two tests at 147 MHz which agree with the predictions, one positive and one negative, made from the 50 MHz data. Thus, all the results to date support the predictions of the theoretical analysis. Further support for the theory is the fact that no result is contradicted by a corresponding experiment at a different carrier frequency. A more complete test of the theory will be obtained when additional experiments are conducted at the untested values of P.. 

For PPY-PF6 and PAN-CSA the microwave dielectric constant remains negative in the far IR even at 10-3 K, which shows that there are free carriers even at these low temperatures. These values of the dielectric constants give small values of plasma frequency which shows that only a small fraction of conduction electrons participate in plasma response. Scattering times come out to be 2 orders of magnitude larger than the values for alkali and noble metals. It is predicted that if technology improves, the conductivity of the doped polymers may become larger than that of metals. 

Free carriers change Raman spectra, either by single particle contribution to the spectrum, or by phonon- plasmon interaction. In addition, interference of electronic transition continua with single phonon excitations may lead to Fano line shapes, as mentioned in the introduction. The Fano effect is encountered in p-doped Si crystals, as shown in Fig. 4.8-19. The shown lines correspond to the respective Raman active mode at 520 cm for crystals with 4 different carrier concentrations, excited with a red laser. The continuous line is calculated according to Eq. 4.8-6. Antiresonance on the low frequency side and line enhancement on the high frequency side are a consequence of the positive value of Q. A reverse type of behavior is possible in the case of a negative Q. 

In modern NMR spectrometers, quadrature phase-sensitive detectors make possible the delerminaiion of positive and negative differences between ihe carrier frequency and NMR frequencies. Because these de-tceiors are able lo sense Ihe sign of the frequency dif-fctcnec. folding is avoided. 

L may be chosen for convenience and we take it as where Ko = ImQolhy = Kqr + iKoi is the dimensioned complex wave number and XoR its real part. The branch cut is drawn just below the negative real axis so that for < 0 the imaginary part of Ko is negative, Xqi = Im(Xo) < 0. Defining dimensionless wave number and carrier frequency as ko = XqL and... 

The beta-rays emitted from the cathode ionize the carrier gas, thereby liberating electrons. If a pulsed voltage is applied to the electrode in the cell, these electrons are captured, so producing an electric current. If electrophilic molecules are introduced into the cell, these absorb electrons and become negatively ionized. The electron density in the detector therefore decreases, so that a smaller number of electrons are captured at each pulse. The total number of electrons captured per unit of time (i.e. the current) can be kept constant by increasing the pulse frequency when the number of electrons decreases. The pulse frequency is then proportional to the concentration of the electrophilic molecules passing through the detector [8]. 

Selecting carrier and modulator frequencies that are not related by simple integer ratios yields an inharmonic spectrum. For example, a carrier of 500 Hz, a modulator of 273 Hz, and an index of five yields frequencies of 500 (carrier), 227,46, 319, 592, 865, 1138, 1411 (negative sidebands) and 773, 1046,1319,1592,1865,2138,2411 (positive sidebands). Figure 10.13 shows a spectrogram of this FM tone, as the index of modulation is ramped from zero to five. The synthesized waveforms at 7 = 0 and 7= 5 are shown as well. 

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