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.

High efficiency resonance-based spectrum filters with tunable transmission bandwidth fabricated using nanoimprint lithography

Abstract: We propose a nanostructured color filter based on a metallic resonant waveguide structure capable of extremely high transmission efficiency. As an experimental demonstration, a blue and a red device were fabricated over a large area using nanoimprint lithography. Achieving transmission as high as 90% with a variable transmission bandwidth, these devices exhibit desirable features for numerous color filter applications.

Acoustic (Underwater) Communications

Abstract: The need for underwater wireless communications exists in off-shore oil industry, environmental monitoring, speech transmission between divers, control of autonomous underwater vehicles, and mapping of the ocean floor for detection of objects and discovery of new resources. Wireless underwater communications can be established by transmission of acoustic waves. However, the communication channels have limited bandwidth, and often cause severe multipath dispersion and time-variability. Despite these limitations, research efforts of the 90's have culminated in the development of underwater acoustic modems that are capable of transmitting information at rates on the order of several kilobits per second systems over varying distances. The emerging scenario is that of an underwater communication network consisting of both stationary and mobile nodes. Current research is focusing on the design of efficient modulation and coding schemes, adaptive signal processing algorithms for equalization and diversity combining, multiple-access communication methods and network protocols suited for low bandwidth, long propagation delays and strict power requirements encountered in the underwater environment. Keywords: underwater communications; acoustic communications; bandwidt-efficient modulation; adaptive equalization; diversity combining; reduced-complexity receivers; phase-coherent detection; channel estimation; multipath propagation; multiuser detection; underwater networks

Gap detection as a function of frequency, bandwidth, and level.

Abstract: The threshold for detection of a temporal gap in a noiseband was measured. A notched noise masker was used to restrict listening to a limited spectral region. Threshold was measured as a function of center frequency, bandwidth, and level. For a signal bandwidth of one‐half the center frequency, the gap threshold decreased from 22.5 ms for a center frequency of 0.2 kHz to 3.2 ms at 8.0 kHz: a wideband condition provided an estimate of 2.3 ms, a value in agreement with previously published estimates. Bandwidth manipulation showed that the variation with frequency was not due to changes in absolute bandwidth alone. The effect of changes in level was determined at three frequencies, 0.4, 1.0, and 6.5 kHz, using a signal bandwidth of half the center frequency. At all frequencies gap threshold decreased as the signal spectrum level was raised from 10 to 25 dB, but a further increase to 40 dB showed no additional improvement. At frequencies up to about 1.0 kHz, the variation of gap threshold with frequency matches well the reciprocal of the bandwidth of the auditory filter, as determined from masking experiments using a notched‐noise masker. This suggests that the temporal response of the auditory filter may limit gap detection at low frequencies.

Bandwidth and power allocation for cooperative strategies in Gaussian relay networks

Abstract: In a relay network with a single source-destination pair, we examine the achievable rates with amplify-and-forward (AF) relaying strategy. Motivated by applications in sensor networks, we consider power-constrained networks with large bandwidth resources and a large number of nodes. We show that the AF strategy does not necessarily benefit from the large available bandwidth. We characterize the optimum AF bandwidth and show that transmitting in the optimum bandwidth allows the network to operate in the linear regime where the achieved rate increases linearly with the available network power. We then present the optimum power allocation among the AF relays. The solution, which can be viewed as a form of maximum ratio combining, indicates the favorable relay positions in the network. Motivated by the large bandwidth resources we further consider a network that uses orthogonal transmissions at the nodes. While the above result for the optimum bandwidth still holds, a different set of relays should optimally be employed. In this case, the relay power solution can be viewed as a form of water-filling. The optimum AF bandwidth and the relay powers can be contrasted to the decode-and-forward (DF) solution. In a network with unconstrained bandwidth, the DF strategy will operate in the wideband regime to minimize the energy cost per information bit (S. Verdu, 2002), (O. Oyman et al., 2004). The wideband DF strategy requires again a different choice of relays; in the case of orthogonal signaling, the data should be sent through only one DF relay (I. Maric et al., 2004). Thus, in general, in a large scale network, a choice of a coding strategy goes beyond determining a coding scheme at a node; it also determines the operating bandwidth as well as the best distribution of the relay power.

Optical single sideband transmission at 10 Gb/s using only electrical dispersion compensation

Abstract: A system is presented which uses optical single sideband transmission at 10 Gb/s together with electrical dispersion compensation at the receiver. Transmission with a bit error rate better than 10/sup -10/ on nondispersion shifted fiber is experimentally demonstrated over 320 km and the dispersion from 1000 km of fiber was effectively equalized in simulation. In the transmitter, driving one or two modulators with a combination of a baseband digital signal and the Hilbert transform of that signal creates an optical single sideband signal. In terms of reducing the effects of chromatic dispersion, transmitting the signal in a single sideband format has two advantages over a double sideband format. First, the optical bandwidth of the transmitted single sideband signal is approximately one half of a conventional double sideband signal. Second, an optical single sideband signal with transmitted carrier can be "self-homodyne" detected and the majority of the phase information preserved since no spectrum back folding occurs upon detection. This allows the received signal to be partially equalized in the electrical domain.