Frequency, carrier

In pulse version of MIA method the probes excite in tested object (TO) free attenuating pulses. Their carrier frequencies coincide with natural frequencies of transmitting probe vibrator loaded to the mechanical impedance Zg = / (Z -tZ,), where Z is elastic... 

The CCF is sensitive to variations in all the signal parameters carrier frequencies, phases, pulse forms, durations and amplitudes. Both signal amplitudes A, and J in formula (1) can factor outside the integral sign and do not define its value. Hence we let the CCF as N= MIA or in normalized form N = NIN . ... 

In equations (3) and (4) the noise was simulated by sine function 6 = bs, (2nat), where a is the ratio of noise frequency to the carrier frequency of the reference signal. 

The calculations show that for both considered types of signals the CCF are very sensitive to initial phases of current and reference pulses and difference in their carrier frequencies. The CCF is also sensitive to the g-factor of loaded vibrators of probes and number of periods in the signal. 

We will explore the effect of three parameters 2 -and < )> that is, the time delay between the pulses, the tuning or detuning of the carrier frequency from resonance with an excited-state vibrational transition and the relative phase of the two pulses. We follow closely the development of [22]. Using equation (Al.6.73). 

Figure Al.6.16. Diagram showing the directionality of the signal in coherent spectroscopy. Associated with the carrier frequency of each interaction with the light is a wavevector, k. The output signal in coherent spectroscopies is detemiined from the direction of each of the input signals via momentum conservation (after [48a]).

Figure Al.6.30. (a) Two pulse sequence used in the Tannor-Rice pump-dump scheme, (b) The Husuni time-frequency distribution corresponding to the two pump sequence in (a), constmcted by taking the overlap of the pulse sequence with a two-parameter family of Gaussians, characterized by different centres in time and carrier frequency, and plotting the overlap as a fiinction of these two parameters. Note that the Husimi distribution allows one to visualize both the time delay and the frequency offset of pump and dump simultaneously (after [52a]).

Signal-to-noise ratio measured at conditions wavelength (A) = 800 nm, carrier frequency (/) = 1 MHz, linear velocity of the disk (t ) = 5 m/s, bandwidth (BW) = 30 kHz, unless otherwise noted. 

Frequency-Modulation Spectroscopy. Frequency-modulation spectroscopy (tins) is a high sensitivity null-background infrared technique for measuring absorbances down to 10 with fast acquisition speeds. Fms involves frequency-modulating a laser source at COq to produce a carrier frequency having sidebands at cJq where is an integral multiple of the modulation frequency. Dye lasers and many other single-line sources can... 

To block carrier frequencies to travel beyond the communication network and weaken the vital signals. 

It has low impedance at power frequency and high impedance at carrier frequency... 

The early system was transmitting 1.5 bits/s (4 sine waves to identify one bit). Later systems went to 3 bits/s. Now with a 24-Hz carrier frequency, 6 bits/s can be transmitted. 

A phase modulation can also be expressed as frequency modulation. The corresponding frequency deviation is the time derivative of the modulated phase angle (Pm t). According to the basic relationships Afrequency deviation Af(f) with respect to the carrier frequency fg, commonly known as the Doppler frequency shift... 

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-... 

How must this theory be modified to describe the effect of the optical excitation The incident electric and magnetic X-ray fields are now pulses Ex(r, t) = Exo(t) exp[j(q r - Oxt)] and Hx(r, t) = Hxo(t) exp[/(q/r - Oxt)]. They still are plane waves with a carrier frequency Ctx, but their amphtudes Exo(t) and Hxo(t) vary with time. The same statement applies to the electron density n r, t), which also is time dependent. However, these variations are all slow with time scales on the order of 1/Ox, and one can neglect 5Exo(0/ 8Hxo(t)/8t as compared to iOxExo(t) and iTlxHxo(0- Detailed calculations then show that [17]... 

Figure 1.34 (a) Reduced S/N ratio resulting from noise folding. If the Rf carrier frequency is placed outside the spectral width, then the noise lying beyond the carrier frequency can fold over, (b) Better S/N ratio is achieved by quadrature detection. The Rf carrier frequency in quadrature detection is placed in the center of the spectrum. Due to the reduced spectral width, noise cannot fold back on to the spectrum. 

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

Chemical shift The difference between the nuclear precession frequency and the carrier frequency. 

Rotating frame The frame is considered to be rotating at the carrier frequency, Vq. This allows a simplified picture of the precessing nuclei to be obtained. 

The parameters and are the chirping rate and the carrier frequency, namely, the laser frequency is chirped quadratically as... 

Since the software is also home built, a number of unique functions can be added to it. An example of such is the way that the data is plotted. In addition to the conventional data plotting scheme, the parametric plot of the real and the imaginary data on the xy-plane is supported. This option enables one to "see" the precession of the transverse nuclear magnetization in the rotating reference frame with respect to the carrier frequency. 

Figure 8 Polar plots of the in-phase and quadrature components of the 79Br NMR signal in a powder sample of KBr in a magnetic field of 7 T under MAS at 5.1 kHz. The carrier frequencies were (A) 100.280545 MHz, (B) 100.281545 MHz, (C) 100.282545 MHz, and (D) 100.283545 MHz. The 79Br resonance frequency was 100.282545 MHz.

This system has been developed to acquire NMR spectra with such broad resonance lines that a single RF pulse cannot excite all the spin packets at once. In such a case, it is more convenient to vary the external field and fix the carrier frequency than to change the carrier frequencies with a constant field magnet, because the latter require probe re-tuning at every increment of the carrier frequencies. Moreover, it can alter the efficiency and phase response of the circuit, putting questions on the quantitative analyses of the data. 

Figure 15B shows a screenshot displaying the spin echoes of 195Pt in platinum powder acquired by the CPMG sequence. The experiments were performed at a carrier frequency of 50.74 MHz. The 19SPt signal... 

Fig. 11 ROCSA spectra for Val-18 of APn-25 fibrils. The C spectrum was measured at 9.39 T under a MAS frequency of 20 kHz. The other spectra were measured at 14.09 T under the frequency of 11 kHz. Upper traces are experimental spectra. Lower traces are best-fit simulations for one-spin system. The rf carrier frequency is at 0 Hz. (Figure and caption adapted from [158]. Copyright [2003], American Institute of Physics)...

Fig. 11.3 Data from an MD Class BioCD. (a) Time trace of gold spokes on an antinode dielectric disk with alternating immobilized antibody. A half harmonic sine wave is shown for comparision. (b) Power spectrum of the signal, showing the carrier frequency and the half harmonic protein pattern...

Fig. 11.5 Differential phase contrast detection of patterned protein in a 10 mm by 30 mm region, (a) Protein height signal showing ridges of protein in a checker board pattern, (b) Side band demodulated signal image in which the carrier frequency of the ridges is removed to show only the protein envelope. Reprinted from Ref. 21. with permission. 2008 Optical Society of America...

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