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.

Orthogonal frequency division multiplexing based spread spectrum multiple access

Abstract: In an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access system the entire bandwidth is divided into orthogonal tones, and all of the orthogonal tones are reused in each cell. To reduce peak-to-average ratio at the mobile transmitter, each voice user is allocated preferably a single one, but no more than a very small number, of the orthogonal tones for use in communicating with the base station. Data users are similarly allocated tones for data communication, however, the number of tones assigned for each particular data user is a function of the data rate for that user. The tone assignment for a given user is not always the same within the available band, but instead the tones assigned to each user are hopped over time. More specifically, in the downlink, the tones assigned to each user are change relatively rapidly, e.g., from symbol to symbol, i.e., the user fast "hops" from one tone to another. However, in the uplink, preferably slow hopping is employed to allow efficient modulation of the uplink signal which necessitates the employing of additional techniques, such as interleaving, to compensate for the reduction in the intercell interference averaging effect. For data communication power control is employed in the uplink and/or downlink so that the transmission rate is increased, e.g., by increasing the number of symbols transmitted per tone per unit time or the coding rate, as a function of allocated power per tone and the corresponding channel attenuation.

Flexible baseband analog circuits for software-defined radio front-ends

Abstract: This paper presents a novel approach to design a digitally programmable low pass filter (LPF) and variable gain amplifier (VGA) intended for a software-defined radio (SDR) front-end. These flexible analog circuits are driven by a network-on-chip (NoC) that is able to set performance parameters like cut-off frequency, selectivity, noise, and gain guaranteeing at any time a near-optimal power/perfomance trade-off. A design approach is proposed to tackle the challenges imposed by flexibility in analog design. A silicon prototype is realized in 0.13-μm CMOS technology with 1.2-V supply voltage to prove the validity of the proposed solution. The LPF provides a frequency tuning range between 0.35 MHz and 23.5 MHz with an adaptive integrated noise level between 85 μVrms and 163 μVrms whereby the power consumption conveniently varies from 0.72 mW to 21.6 mW according to the required performance. The VGA is made up of two cascaded gain stages and provides a gain range from about 0 dB to 39 dB with a reconfigurable power/bandwidth.

Bandwidth, Q factor, and resonance models of antennas

Abstract: In this paper, we introduce a first order accurate resonance model based on a second order Pade approximation of the reflection coefficient of a narrowband antenna. The resonance model is characterized by its Q factor, given by the frequency derivative of the reflection coefficient. The Bode-Fano matching theory is used to determine the bandwidth of the resonance model and it is shown that it also determines the bandwidth of the antenna for sufficiently narrow bandwidths. The bandwidth is expressed in the Q factor of the resonance model and the threshold limit on the reflection coefficient. Spherical vector modes are used to illustrate the results. Finally, we demonstrate the fundamental difficulty of finding a simple relation between the Q of the resonance model, and the classical Q defined as the quotient between the stored and radiated energies, even though there is usually a close resemblance between these entities for many real antennas.

Receiver with sigma-delta analog-to-digital converter for sampling a received signal

Abstract: A receiver comprising a sigma-delta analog-to-digital converter (ΣΔ ADC) can be utilized in one of four configurations, as a subsampling bandpass receiver, a subsampling baseband receiver, a Nyquist sampling bandpass receiver, or a Nyquist sampling baseband receiver. For subsampling ΣΔ receivers, the sampling frequency is less than twice the center frequency of the input signal into the ΣΔ ADC. For Nyquist sampling ΣΔ receivers, the sampling frequency is at least twice the highest frequency of the input signal into the ΣΔ ADC. For baseband ΣΔ receivers, the center frequency of the output signal from the ΣΔ ADC is approximately zero or DC. For bandpass ΣΔ receivers, the center frequency of the output signal from the ΣΔ ADC is greater than zero. The sampling frequency can be selected based on the bandwidth of the input signal to simplify the design of the digital circuits used to process the output samples from the ΣΔ ADC. Furthermore, the center frequency of the input signal can be selected based on the sampling frequency and the bandwidth of the input signal. The ΣΔ ADC within the receiver provides many benefits.

Path Characteristic Frequency-Based Fault Locating in Radial Distribution Systems Using Wavelets and Neural Networks

Abstract: This paper proposes a new algorithm for localizing phase to ground faults in an electric power distribution system. Fault-originated traveling waves propagate along the distribution paths in both directions away from the fault point and are reflected at line terminations, junctions between feeders, laterals, and the fault location. Depending on the paths which traveling waves reciprocate through, the transient signal at each node contains certain path characteristic frequencies (PCFs). Energy spectrum of the transient signal has high density around the path characteristic frequencies. On this basis, the transient voltage is decomposed by a wavelet filter and its energy spectrum is decomposed into different levels. Depending on the bandwidth of the wavelet filter and the path characteristic frequencies, the decomposed signal in each level contains a certain percentage of energy. Then, a neural network-based methodology is proposed as a power distribution line fault locator. Energy percentage in each level is the candidate feature for training the artificial neural network. Simulations and the training process for the neural network are performed respectively using ATP/EMTP and MATLAB. It is shown that the results of the proposed algorithm are quite satisfactory.