Sine wave

About: Sine wave is a research topic. Over the lifetime, 12183 publications have been published within this topic receiving 93013 citations. The topic is also known as: sinusoid.

Signal processor with improved efficiency

Abstract: A signal processor arranged and constructed to provide a discrete time Fourier transform (DTFT) corresponding to a sequence of samples, including a current, preferably, last sample, of a signal, the signal processor including a recursive structure (303), coupled to the signal and operating on the sequence of samples, for providing an output (309) and a first previous output (310), the output proportional to a combination of the current sample of the signal, and the first previous output weighted by a sinusoidal function, less a second previous output (316), the sinusoidal function having an argument corresponding to an arbitrary frequency, and a combiner (330) coupled to the output and the first previous output for providing a DTFT signal proportional to a DTFT evaluated at the arbitrary frequency for the sequence of samples.

On determining polarization characteristics of ion cyclotron wave magnetic field fluctuations

Abstract: Polarization characteristics of magnetospheric proton cyclotron waves should provide definitive tests of mechanisms for wave propagation and growth. Previous studies used Fourier spectral analysis to determine the ellipticity e and the minimum variance direction e min , which gives θmin, the angle between e min and the background field B 0 . Comparison with theoretical models depends critically on accurate determination of e and θ min . However, observed fluctuations might not be sets of phase-coherent sine waves, as implicitly assumed in Fourier analysis, but may consist of series of packets whose phase and azimuthal orientation vary randomly. By constructing synthetic nonstationary signals, we find that spectral analysis of data intervals containing several wave packets systematically underestimates θ min , often by 45° or more, and overestimates |e|. The problem is caused by fluctuations in the polarization ellipse azimuth orientation. We present a minimum variance analysis technique, called wave-step analysis, which requires only a few wave cycles of data. Tests of the wave-step procedure show that it is valid for signals with bandwidths up to ∼30% full width at half maximum and is therefore applicable to the majority of proton cyclotron wave events. Comparison of the wave-step and Fourier analyses for cyclotron wave events confirms that cyclotron wave fluctuations display features characteristic of nonstationary signals. Relative to the wave-step results, the Fourier results underestimate θ min , overestimate |e|, and display the predicted variations of these parameters with each other and with azimuth angle fluctuations. The opposite relationship between Fourier and wave-step θ min should result if the signals were too broadbanded for the wave-step algorithm. Thus the θ min results provide an unambiguous indication of nonstationarity. Time windows of 30 s proved to be too long for analysis of ∼0.5 Hz signals, indicating that analysis needs to be carried out on timescales shorter than tens of wave periods. Previous analyses reported θ min ≤ 30°, but the wave-step results for one linearly polarized event analyzed here show that θ min can be larger than 70°.

Nonlinear short-wave propagation in ferrites

Abstract: In this paper we discuss the propagation of nonlinear electromagnetic short waves in ferromagnetic insulators. We show that such propagation is perpendicular to an externally applied field. In the nonlinear regime we determine various possible propagation patterns: an isolated pulse, a modulated sinusoidal wave, and an asymptotic two-peak wave. The mathematical structure underlying the existence of these solutions is that of the integrable sine-Gordon equation.

A High Resolution Multibit Sigma-delta Modulator With Individual Level Averaging

Abstract: A second-order sigma-delta modulator with a 3-b internal quantizer employing the individual level averaging technique has been designed and implemented in a 1.2 μm CMOS technology. Testing results show no observable harmonic distortion components above the noise floor. Peak S/(N + D) ratio of 91 dB and dynamic range of 96 dB have been achieved at a clock rate of 2.56 MHz for a 20 KHz baseband. No tone is observed in the baseband as the amplitude of a 10 KHz input sine wave is reduced from −0.5 dB to −107 dB below the voltage reference. The active area of the prototype chip is 3.1 mm 2 and it dissipates 67.5 mW of power from a 5 V supply

Optical single sideband transmitter

Abstract: With the normal modulation method, it is difficult to construct a Hilbert transform device because it is complicated. To solve the problem, the present invention generates a single sideband modulated optical pulse train by driving a Mach-Zehnder optical modulator for optical pulse generation with a laser source's sine wave clock signals rendered 90 degrees out of phase from each other. The generated pulse train is entered into an optical modulator, modulated with an NRZ (nonreturn-to-zero) data signal, and filtered by a narrow-band optical filter to obtain one of two sidebands.