Search results for "signal processing"
showing 10 items of 2451 documents
Shape Optimization in Contact Problems. 1. Design of an Elastic Body. 2. Design of an Elastic Perfectly Plastic Body
1986
The optimal shape design of a two dimensional body on a rigid foundation is analyzed. The problem is how to find the boundary part of the body where the unilateral boundary conditions are assumed in such a way that a certain energy integral (total potential energy, for example) will be minimized. It is assumed that the material of the body is elastic. Some remarks will be given concerning the design of an elastic perfectly plastic body. Numerical examples will be given.
Low-noise microvolt level calibrator for measurement of performance of biosignal recording systems
1997
A calibrator, the noise level of which is below the noise level generated in the preamplifier system, was needed for testing and development of a multichannel recording system. A multichannel preamplifier head assembly was used for recording cortical, subcortical, and cerebellar slow potentials and multiunit activity in freely moving cats and restrained rabbits. An inexpensive, battery-powered, lownoise voltage signal generator for calibration of the preamplifiers is described. The circuit provides a square-wave output at a frequency of 10 or 1000 Hz, and the peak-to-peak (p-p) amplitude can be selected at 10, 100, or 1000µV. The measured output noise of the calibrator is below 2µV (p-p, 0.…
Photonically assisted RF generator with incoherent sources
2008
An RF waveform generator operating with incoherent broadband light is successfully implemented. Complex RF ~10 GHz bandwidth waveforms are generated by means of incoherent wavelength-to-time mapping. Our technique can be scaled to the mm-wave range.
Reconfigurable RF waveform generation using optical incoherent sources
2008
An RF waveform generator operating with incoherent broadband light is successfully implemented. Complex RF ~10 GHz bandwidth waveforms are generated by means of incoherent wavelength-to-time mapping. Our technique can be scaled to the mm-wave range.
20 GHz arbitrary radio-frequency waveform generator based on incoherent pulse shaping
2008
We demonstrate a new approach of photonically assisted radiofrequency (RF) waveform generation using a spectrally incoherent light source. The system is based on the so-called generalized frequency-to-time mapping operation. In this work, external modulation of the source is done by concatenating two electro-optic Mach-Zehnder modulators properly biased to achieve short pulse gates which allow for broad bandwidth electrical signals. Also, the spectral shaping stage is performed prior to O/E conversion. A detailed theoretical analysis demonstrates that even in this case the frequency-to-time mapping is preserved. The key is that the noise level is greatly reduced because the amplitude filter…
PON Monitoring Technique Based on 2D Encoders and Wavelength-to-Time Mapping
2020
A PON monitoring technique is demonstrated based on an OTDR-like device and FBG-encoders having a unique combination of central wavelength and reflection bandwidth. This results in more compact and cost-efficient encoders than previous proposals.
Millimeter-wave and microwave signal generation by low-bandwidth electro-optic phase modulation
2009
We propose, analyze and numerically illustrate a photonic-based technique for waveform generation of electrical signals approaching the 50 GHz bandwidth with time apertures as large as a few nanoseconds, by low-frequency, up to 2 GHz, electro-optic phase modulation of time-stretched optical pulses. Synthesis of the electrical waveform relies on phase-to-amplitude conversion of the modulated signal by a group delay dispersion circuit designed to behave as a transversal filter with N taps. Although arbitrary waveform generation capabilities are limited, a wide variety of user-defined signals are numerically demonstrated by appropriately designing the low-frequency signal driving the electro-o…
Lossless equalization of frequency combs
2008
Frequency combs obtained by sinusoidal phase modulation of narrow-band continuous-wave lasers are widely used in the field of optical communications. However, the resulting spectral envelope of the comb is not at. In this Letter, we propose a general and eficient approach to achieve at frequency combs with tunable bandwidth. The idea is based on a two-step process. First, eficient generation of a train with temporal at-top-pulse profile is required. Second, we use large parabolic phase modulation in every train period in order to map the temporal intensity shape into the spectral domain. In this way, the resulting spectral envelope is at and the size is tunable with the chirping rate. Two d…
An evaluation procedure for scanning interferometer based wavemeters
2004
Abstract A common approach to wavelength measurement is the travelling interferometer (wavemeter). We present an evaluation procedure that allows to achieve high precision with a compact device. The zero crossings of the interference signal corresponding to the reference laser is used to sample the signal of the probe laser. Electronic noise and fluctuations of the laser frequency cancel due to the large number of sample points. The evaluation procedure has been applied to a wavemeter based on a continuously moving Mach–Zehnder interferometer. A travelling path of 10 cm was sufficient to yield 3σ-accuracy of Δ λ / λ =3.2×10 −9 , demonstrated by comparison with cesium saturation spectroscopy.
A signal processing scheme based on high-frequency electromechanical oscillations in nanostructures
2009
We explore the characteristics of a new signal processing scheme based on the high-frequency electromechanical oscillations of a nanostructure formed by an oscillating metallic nanoparticle connected to the left and right electrodes by soft links. Because this system shows resonant behavior when the frequency of the applied electric potential is close to the characteristic natural frequency of the oscillating nanoparticle, a parallel arrangement of nanostructures with different frequencies can be excited selectively by an external time-dependent electrical signal with the appropriate resonant frequencies. The highly nonlinear system response makes it possible to devise a signal processing s…