Effects Of Modulation Depth Research Articles

Analytical research on optical phase shift modulation scheme with maximum modulation efficiency for analog and digital signals

This paper presents the analytical research and characterization of optical Binary Phase Shift Keying (BPSK) for single-tone sinusoidal and digital signals. The mathematical analysis and simulation for optimal modulation depth are proposed in this paper for maximum efficiency of the output modulated signal. The modulation depth is analysed with suitable Radio Frequency (RF) drive voltage for message signal and the effect of modulation depth on carrier suppression and higher order harmonics over fundamental tone is analysed theoretically and with simulation. To achieve phase modulation in this work, an external modulation technique via the Mach-Zehnder Modulator (MZM) is used, and an optical source using a narrow line width Distributed Feed Back (DFB) laser is used to minimise phase noise. The simulation and characterization results strongly support the mathematical analysis of the proposed criteria for suitable RF drive over half wave voltage for optimal detection and maximum message signal efficiency.

Effect of modulation depth, frequency, and intermittence on wind turbine noise annoyance.

Amplitude modulation (AM) may be an important factor for the perceived annoyance of wind turbine noise (WTN). Two AM types, typically referred to as "normal AM" (NAM) and "other AM" (OAM), characterize WTN AM, OAM corresponding to having intermittent periods with larger AM depth in lower frequency regions than NAM. The extent to which AM depth, frequency, and type affect WTN annoyance remains uncertain. Moreover, the temporal variations of WTN AM have often not been considered. Here, realistic stimuli accounting for such temporal variations were synthesized such that AM depth, frequency, and type, while determined from real on-site recordings, could be varied systematically. Listening tests with both original and synthesized stimuli showed that a reduction in mean AM depth across the spectrum led to a significant decrease in annoyance. When the spectrotemporal characteristics of the original far-field stimuli and the temporal AM variations were taken into account, the effect of AM frequency remained limited and the presence of intermittent OAM periods did not affect annoyance. These findings suggest that, at a given overall level, the AM depth of NAM periods is the most crucial AM parameter for WTN annoyance.

Photonic generation of frequency quadrupling signal for millimeter-wave communication

We propose and demonstrate a photonic method of generating frequency quadrupling signal for millimeter-wave (mm-wave) wireless communication system. The frequency quadrupling scheme is based on carriers cancellation within an integrated dual-parallel Mach–Zehnder modulator (DPMZM), thus avoiding the use of an optical filter or an electrical phase shifter. The effects of modulation-depth on the power level of generated mm-wave signal as well as on the system performance of wireless transmission are analyzed theoretically and measured experimentally. In the experiment, transmission of 155Mbps OOK baseband data on a photonic-generated 40GHz mm-wave over a length of 25km standard single-mode fiber (SMF) and 20m wireless distance with error free is successfully demonstrated.

Mode-locked, continuous-wave, singly resonant optical parametric oscillator

We report an actively mode-locked continuous-wave (cw) optical parametric oscillator in singly resonant oscillator (SRO) configuration, generating stable 230 ps pulses at 80 MHz repetition rate. The idler-resonant cw SRO, configured in standing-wave cavity, is based on MgO:sPPLT as the nonlinear gain material and pumped at 532 nm. Mode-locking is achieved by direct deployment of an intracavity phase modulator close to one of the SRO cavity end mirrors. The effects of modulation depth and modulation frequency on mode-locked pulse duration and repetition rate are investigated for both idler and signal pulses. Mode-locking is further confirmed by enhancement of single-pass second-harmonic generation of SRO output in the crystal of β-BaB(2)O(4).

Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier

In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.

Dynamic behavior and complexity of modulated optical micro ring resonator

The dynamic behavior of an optical micro ring resonator (OMRR) with an amplitude modulator positioned in the micro ring is investigated quantitatively by adopting a recently introduced quantifier, the permutation entropy (PE). The effects of modulation depth are focused on, and the roles of input power are considered. The two-dimensional (2D) maps of PE showing dependence on both modulation depth and input power are presented as well. PE values nearly increase with modulation depth. On the other hand, the optimal value of input power is achieved when the PE reaches its maximum. Thus, PE can successfully quantify the dynamics of modulated OMRR. Selecting the parameters in the region with high PE values would contribute to the complexity-enhanced OMRR-based chaotic communication systems.

Modulation detection interference in listeners with cochlear hearing loss: Effect of modulation depth and onset delay.

Modulation detection interference (MDI) was measured for listeners with normal hearing (NH) and cochlear hearing loss (HI). The signal was 1 kHz, and the interferer was 2 kHz. The stimuli level was 50 or 22 dB SL. The interferer was modulated with 8 Hz at various modulation depths (25, 50, 75, or 100%). The onset of signal was delayed by 0, 125, 250, 375, 500 or 625 ms relative to onset of the interferer. For NH subjects, MDI increased systematically with increasing modulation depth of the interferer. MDI almost disappeared with 375 or 500 ms onset delay except a condition with the interferer of 25% modulation depth where there was no MDI at all across different onset delay conditions. In contrast, for HI subjects, there was quite an amount of MDI even with the interferer of 25% modulation depth, and MDI was greater than NH for all modulation depths at 0 and 125 ms onset delays, suggesting that the perceived modulation depth of the interferer might be exaggerated for HI than for NH.

Theoretical study on coupling effect of modulation depth between two photorefractive phase gratings

In this paper, we have applied a perturbation expanding method to the hopping model, and studied the coupling effect of modulation depth between two photorefractive phase gratings stored in one point. The coupling equations of modulation depth and their steady solutions have been derived. It has been found that the modulation depth of one of the two gratings seriously affects the spatial-charge field of the other grating.

Comodulation masking release using SAM tonal complex maskers: Effects of modulation depth and signal position

The purpose of this investigation was to examine two stimulus parameters that were reasoned to be of importance to comodulation masking release (CMR). The first was the degree of fluctuation, or depth of modulation, in the masker bands, and the second was the temporal position of the signal with respect to the modulations of the masker. The investigation began by demonstrating the efficacy of sinusoidally amplitude-modulated (SAM) tonal complex maskers in eliciting CMR. "Nine-band" maskers, 650 ms in duration, were constructed by adding together nine SAM tones spaced at 100-Hz intervals from 300 to 1100 Hz. The rate of modulation for each SAM tone was 10 Hz, and the depth of modulation was 100%. Using such maskers, it was shown that when the on-frequency SAM tone had a modulation depth of 100%, the threshold for a 250-ms, 700-Hz tone improved monotonically as the modulation depths of the flanking SAM tones increased from 0% to 100%. When the on-frequency SAM tone had a modulation depth of 63%, some listeners performed optimally when the flanking SAM tones also exhibited a modulation depth of 63%, whereas others performed best when the flankers had modulation depths of 100%. With regard to signal position, a typical CMR effect was observed when the signal, consisting of a train of three 50-ms, 700-Hz tone bursts, was placed in the dips of the on-frequency masker. However, when the signal was placed at the peaks of the envelope, an increase in masking was observed for a comodulated masker.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient pulse evolution of active mode locking in an intracavity frequency-doubled laser

The theory of transient mode locking for an active modulator in an intracavity frequency-doubled laser is presented. The theory is applied to mode-locked and intracavity frequency-doubled Nd:YAG laser and the mode-locked pulse width is plotted as a function of number of round trips inside the cavity. It is found that the pulse compression is faster and the system takes a very short time to approach the steady state in the presence of a second harmonic generating crystal inside the laser cavity. The effect of modulation depth and the second harmonic conversion efficiency on the temporal behavior of the pulse width is discussed.