Multi-channel active noise cancellation using the DSP56001 (digital signal processor)

The authors report on the performance of a portable active noise cancellation (ANC) system based around a PC hosted 20-MHz Motorola DSP56001 processor with a four-channel analog input/output (I/O) board connected to the real world via standard consumer audio components. The system will perform active noise cancellation over the frequency range of 65-500 Hz. Quantitative results are presented for the cancellation of single tone noise and of narrowband noise, and a measure of the ANC power spectrum is calculated for various parameters of the filtered-X LMS algorithm in different acoustic environments. Qualitative results based on human hearing perception of the attenuation of various narrowband and real world noise sources are also discussed

On the optimality of subband adaptive filters

In this paper, we derive a polyphase analysis to determine the optimum filters in a subband adaptive filter (SAF) system. The structure of this optimum solution deviates from the standard SAF approach and presents its best possible solution only as an approximation. Besides this new insight into SAF error sources, the discussed analysis allows to calculate the optimum subband responses and the standard SAF approximation. Examples demonstrating the validity of our analysis and its use for determining SAF errors are presented

A theoretical study of elastic X-ray scattering

Bragg X-ray scattering intensities are defined as scattering by the thermodynamic average electron-charge density. Purely elastic, kinematic X-ray scattering by a target in thermal equilibrium is always larger than Bragg scattering. At low temperatures, the elastic scattering becomes Bragg scattering. For large molecules, such as a crystal, at ordinary temperatures the elastic and Bragg scattering differ in a relative sense by O(N-1), where N is the number of vibrational degrees of freedom. For most practical cases the Bragg scattering is essentially the same as purely elastic scattering of X-rays

A generalised sidelobe canceller architecture based on oversampled subband decompositions

Adaptive broadband beamforming can be performed in oversampled subband signals, whereby an independent beamformer is operated in each frequency band. This has been shown to result in a considerably reduced computational complexity. In this paper, we primarily investigate the convergence behaviour of the generalised sidelobe canceller (GSC) based on normalised least mean squares algorithm (NLMS) when operated in subbands. The minimum mean squared error can be limited, amongst other factors, by the aliasing present in the subbands. With regard to convergence speed, there is strong indication that the subband-GSC converges faster than a fullband counterpart of similar modelling capabilities. Simulations are presented

Robust transceiver design for MIMO relay systems with tomlinson harashima precoding

In this paper we consider a robust transceiver design for two hop non-regenerative multiple-input multiple-output (MIMO) relay networks with imperfect channel state information (CSI). The transceiver consists of Tomlinson Harashima Pre-coding (THP) at the source with a linear precoder at the relay and linear equalisation at the destination. Under the assumption that each node in the network can acquire statistical knowledge of the channel in the form of a channel mean and estimation error covariance, we optimise the processors to minimise the expected arithmetic mean square error (MSE) subject to transmission power constraints at the source and relay. Simulation results demonstrate the robustness of the proposed transceiver design to channel estimation errors

ZF DFE transceiver design for MIMO relay systems with direct source-destination link

In this paper we consider a non-linear transceiver design for non-regenerative multiple-input multiple-output (MIMO) relay networks where a direct link exists between the source and destination. Our system utilises linear processors at the source and relay as well as a zero-forcing (ZF) decision feedback equaliser (DFE) at the receiver. Under the assumption that full channel state information (CSI) is available the precoding and equaliser matrices are designed to minimise the arithmetic mean square error (MSE) whilst meeting transmit power constraints at the source and destination. The source, relay, and destination processors are provided in closed form solution. In the absence of the direct link our design particularises to a previous ZF DFE solution and as such can be viewed as a generalisation of an existing work. We demonstrate the effectiveness of the proposed solution through simulation and show that it outperforms existing techniques in terms of bit error ratio (BER)

Inversion of Parahermitian matrices

Parahermitian matrices arise in broadband multiple-input multiple-output (MIMO) systems or array processing, and require inversion in some instances. In this paper, we apply a polynomial eigenvalue decomposition obtained by the sequential best rotation algorithm to decompose a parahermitian matrix into a product of two paraunitary, i.e.lossless and easily invertible matrices, and a diagonal polynomial matrix. The inversion of the overall parahermitian matrix therefore reduces to the inversion of auto-correlation sequences in this diagonal matrix. We investigate a number of different approaches to obtain this inversion, and and assessment of the numerical stability and complexity of the inversion process

Dynamic reconfiguration technologies based on FPGA in software defined radio system

Partial Reconfiguration (PR) is a method for Field Programmable Gate Array (FPGA) designs which allows multiple applications to time-share a portion of an FPGA while the rest of the device continues to operate unaffected. Using this strategy, the physical layer processing architecture in Software Defined Radio (SDR) systems can benefit from reduced complexity and increased design flexibility, as different waveform applications can be grouped into one part of a single FPGA. Waveform switching often means not only changing functionality, but also changing the FPGA clock frequency. However, that is beyond the current functionality of PR processes as the clock components (such as Digital Clock Managers (DCMs)) are excluded from the process of partial reconfiguration. In this paper, we present a novel architecture that combines another reconfigurable technology, Dynamic Reconfigurable Port (DRP), with PR based on a single FPGA in order to dynamically change both functionality and also the clock frequency. The architecture is demonstrated to reduce hardware utilization significantly compared with standard, static FPGA design

Dividend taxation and Corporate investment: A comparative study between the classical system and imputation system of dividend taxation in the United States and Australia.

In recent times a number of countries initiated some important tax reforms to eliminate the distortions of double taxation. In this context, Australia adopted a dividend imputation system in 1987, while the US employed the 1986 Tax Reform Act (TRA). The analysis examines the effect on the level of corporate capital investment on proxies for corporate tax rates, financial leverage, liquidity, capital intensity and firm size after controlling for the tax reforms. The empirical results provide evidence that: (1) dividend imputation as introduced in Australia is an effective way to reduce the distortions caused by the traditional system of taxation. (2) Compared with the TRA, dividend imputation has been better able to positively stimulate corporate capital investment. (3) TRA effect on corporate investment is more pronounced in the US for firms having a net operating loss. (4) Corporate tax rates play a role in corporate investment decision in Australiadividend taxation, imputation system, classical system, corporate investments