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The use of multiple radar configurations can overcome some of the geometrical limitations that exist when obtaining radar images of a target using inverse synthetic aperture radar (ISAR) techniques. It is shown here how a particular bistatic configuration call produce three view angles and three ISAR images simultaneously. A new ISAR signal model is proposed and the applicability of employing existing monostatic ISAR techniques to bistatic configurations is analytically demonstrated. An analysis of the distortion introduced by the bistatic geometry to the ISAR image point spread function (PSF) is then carried out and the limits of the applicability of ISAR techniques (without the introduction of additional signal processing) are found and discussed. Simulations and proof of concept experimental data are also provided that support the theory.

In various signal-channel-estimation problems, the channel being estimated may be well approximated by a discrete finite impulse response (FIR) model with sparsely separated active or nonzero taps. A common approach to estimating such channels involves a discrete normalized least-mean-square (NLMS) adaptive FIR filter, every tap of which is adapted at each sample interval. Such an approach suffers from slow convergence rates and poor tracking when the required FIR filter is 'long.' Recently, NLMS-based algorithms have been proposed that employ least-squares-based structural detection techniques to exploit possible sparse channel structure and subsequently provide improved estimation performance. However, these algorithms perform poorly when there is a large dynamic range amongst the active taps. In this paper, we propose two modifications to the previous algorithms, which essentially remove this limitation. The modifications also significantly improve the applicability of the detection technique to structurally time varying channels. Importantly, for sparse channels, the computational cost of the newly proposed detection-guided NLMS estimator is only marginally greater than that of the standard NLMS estimator. Simulations demonstrate the favourable performance of the newly proposed algorithm. Index Terms--Tap selection, partial update, least squares, structurally consistent.

A modified least-mean-square (LMS) estimation that LMS-estimates the coefficients only of the active taps of the unknown channel is proposed. The algorithm is shown to have performance advantages over the standard LMS algorithm and the structural detection-based LMS/NLMS algorithms. It was prompted by results of analyses which indicated that performance improvements over the standard LMS estimation for white input signals can be achieved by estimating only the nonzero or 'active' taps.

The convergence rate of an LMS adaptive FIR filter to a stationary FIR-modeled unknown channel depends on the unknown channel vector of the adaptive filter system. This was gleaned from an analysis of the influence of filter parameter dimension and input signal characteristics on the convergence rate of the LMS adaptive FIR estimator. Results indicate that the expected convergence rate decreases as dimension increases, unless the input signal is white.

The central 4-wire loop telephone system, with an adaptive echo canceller at either end of the loop, typically achieves good echo suppression. However, poorly cancelled echoes and/or signal bursting have been observed. Such undesirable behavior has been linked to the presence of cross correlation between and autocorrelation of the signals transmitted by the subscribers. The primary aim of this paper is to quantify the relationship between the correlation levels of the subscriber signals and echo canceller performance in the double echo canceller (DEC) 4-wire loop system. This is achieved by carrying out dynamical analyses of the DEC system. The analyses lead to the determination of conditions on the subscriber signals' correlation levels, satisfaction of which result in guaranteed stable behavior. Furthermore, the analyses indicate that good echo cancellation requires the subscriber signals to have minimal cross correlation and narrow autocorrelation functions. These results lead to the investigation of the whitening and orthogonalizing capabilities of scramblers. A line coding scheme, based on these devices, is identified, which, for essentially all subscriber signals, leads to good echo cancellation.

In various adaptive estimation applications, such as acoustic echo cancellation within teleconferencing systems, the input signal is a highly correlated speech. This, in general, leads to extremely slow convergence of the NLMS adaptive FIR estimator. As a result, for such applications, the affine projection algorithm (APA) or the low-complexity version, the fast affine projection (FAP) algorithm, is commonly employed instead of the NLMS algorithm. In such applications, the signal propagation channel may have a relatively low-dimensional impulse response structure, that is, the number m of active or significant taps within the (discrete-time modelled) channel impulse response is much less than the overall tap length n of the channel impulse response. For such cases, we investigate the inclusion of an active-parameter detection-guided concept within the fast affine projection FIR channel estimator. Simulation results indicate that the proposed detection-guided fast affine projection channel estimator has improved convergence speed and has lead to better steady-state performance than the standard fast affine projection channel estimator, especially in the important case of highly correlated speech input signals.

A blind nonlinear interference cancellation receiver for code-division multiple-access- (CDMA-) based communication systems operating over Rayleigh flat-fading channels is proposed. The receiver which assumes knowledge of the signature waveforms of all the users is implemented in an asynchronous CDMA environment. Unlike the conventional MMSE receiver, the proposed blind ICA multiuser detector is shown to be robust without training sequences and with only knowledge of the signature waveforms. It has achieved nearly the same performance of the conventional training-based MMSE receiver. Several comparisons and experiments are performed based on examining BER performance in AWGN and Rayleigh fading in order to verify the validity of the proposed blind ICA multiuser detector.

Civil engineering firms are expected to face changing management issues in the 21st century. Analysts predict that construction projects in the future would have vastly shorter completion times. Cellular modes of construction would most likely be widely practiced. Engineering plans might also provide wider flexibility margins to give fast-tracked decisions allowance for refinements during plan implementation. Specific aspects of projects may be assigned to specialized teams which would be coordinated and overseen by a qualified engineering leader.

Proposes a method for reducing the nuclear polarization times in nuclear magnetic resonance studies of slowly relaxing dipolar nuclei. Reliance of the method on the magnetic field dependence of the spin-lattice relaxation times for dipolar nuclei.

We consider the normalized least mean square (NLMS) estimation of a channel, which may be well approximated by a finite impulse response model with sparsely separated active or nonzero taps. Previously reported analyses imply that the convergence rate of the NLMS estimator should be greatly enhanced if only the active taps are estimated. We propose an NLMS estimator, which incorporates a least squares based active tap detection method. Simulations demonstrate that the NLMS estimator has significantly faster convergence than the standard NLMS estimator for colored as well as white input signals. Furthermore, for sparse channels, this improved convergence speed is accompanied by a lower computational cost. Index Terms--Adaptive filters, least mean square methods, least squares methods, echo suppression, transient analysis.