Bandwidth (signal processing)

About: Bandwidth (signal processing) is a research topic. Over the lifetime, 48550 publications have been published within this topic receiving 600741 citations. The topic is also known as: Bandwidth (signal processing) & bandwidth.

Ultra-wideband channel modeling on the basis of information-theoretic criteria

Abstract: We present results of two ultra-wideband (UWB) channel measurement campaigns in the 2-5 GHz frequency band, and use Akaike's Information Criterion (AIC) to determine suitable distributions for the channel impulse response taps. Despite the large bandwidth, AIC supports the complex Gaussian tap distribution, with mean depending on the measurement setting. We estimate the empirical covariance matrix of the channel impulse response, and demonstrate that the number of corresponding significant eigenvalues scales approximately linearly with bandwidth, albeit we find that channel taps are correlated

Modeling of Multisampled Pulse Width Modulators for Digitally Controlled DC–DC Converters

Abstract: This paper presents steady-state and small-signal models for digital pulsewidth modulators (DPWM) employed in multiple sampling digital control schemes for dc-dc switched mode power supplies (SMPS), and identifies the triangular modulation as intrinsically superior to other modulation schemes in multisampling applications. In conventional digital control of dc-dc converters, closed-loop bandwidth limitations are mainly set by analog-to-digital conversion times, computational delays and DPWM delays originated by the sampled nature of the PWM. While the use of hardwired logic and fast A/D converters minimizes computational and A/D delays, the DPWM small-signal phase lag strictly depends on the adopted sampling strategy. Multiple sampling techniques recently proposed in literature can achieve a strong reduction of the DPWM delay by operating the control and modulation steps at a sampling frequency strictly higher than the converter switching frequency. On the other hand, multisampled pulse width modulators (MSPWMs) exhibit nonlinear behaviors which do not have analog counterparts nor are encountered in conventional digital control, the most relevant effect being the onset of sampling induced dead bands, i.e., regions of zero modulation gain in the modulator transcharacteristic which may compromise proper closed-loop operation of the converter. The models proposed in this paper fully characterize the steady-state and small-signal behavior of DPWMs operated in multiple-sampling fashion. Multisampled triangular modulators are proven to be intrinsically superior to trailing edge or leading edge modulators in terms of linearity. Simulation and experimental results validate the proposed models and confirm the properties of triangular modulations.

Motion video signal encoder and encoding method

Abstract: A motion video signal encoder maximizes image quality without exceeding transmission bandwidth available to carry the encoded motion video signal by comparing encoded frames of the motion video signal to a desired size of frame. If the size of encoded frames differ from the desired size, encoding is adjusted to produce encoded frames closer in size to the desired size. In addition, a cumulative bandwidth error records an accumulated amount of available bandwidth. The cumulative bandwidth error is adjusted as time elapses to add to the available bandwidth and as each frame is encoded to thereby consume bandwidth. As the cumulative bandwidth error grows in magnitude above or below zero, encoding is adjusted as needed to either improve image quality to more completely consume available bandwidth or to reduce image quality to thereby consume less bandwidth and to thereby cause the cumulative bandwidth error to move toward zero. Rapid changes in the amount of change or motion in the motion video signal are detected by comparing the amount of change between two consecutive frames and filtering the amount of change with previously measured amounts of change. Encoding is pre-compensated according to the filtered measurement of rapid change.

Tailoring of the Brillouin gain for on-chip widely tunable and reconfigurable broadband microwave photonic filters

Abstract: An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters. More than a decade bandwidth reconfigurability from 30 up to 440 MHz, with a passband ripple <1.9 dB is achieved by tailoring the Brillouin pump. The filter central frequency is continuously tuned up to 30 GHz with no degradation of the passband response, which is a major improvement over electronic filters. Furthermore, we demonstrate pump tailoring to realize multiple bandpass filters with different bandwidths and central frequencies, paving the way for multiple on-chip microwave filters and channelizers.

A Fully Integrated UHF-Band CMOS Receiver With Multi-Resolution Spectrum Sensing (MRSS) Functionality for IEEE 802.22 Cognitive Radio Applications

Abstract: Fast and accurate spectrum sensing is one of the most important functions in a cognitive radio (CR) seeking to use the licensed but unoccupied spectrum segments. In this paper, we present a fully integrated CMOS receiver with a CR spectrum sensing capability in the UHF band. We propose multi-resolution spectrum sensing (MRSS), which is a digitally-assisted analog energy detection technique. Without using bulky analog filters, detection bandwidth can be flexibly controlled by correlating the received analog signals with window signal generated by built-in digital window generator. The integrated chip has been fabricated in a standard 0.18-mumm CMOS technology, and has achieved 32 dB of detection dynamic range with minimum detection sensitivity of -74 dBm by using a 100-kHz cos4 window.