Adaptive broadband beamforming with arbitrary array geometry

This paper expands on a recent polynomial matrix formulation for a minimum variance distortionless response (MVDR) broadband beamformer. Within the polynomial matrix framework, this beamformer is a straightforward extension from the narrowband case, and offers advantages in terms of complexity and robustness particularly for off-broadside constraints. Here, we focus on arbitrary 3-dimensional array configurations of no particular structure, where the straightforward formulation and incorporation of constraints is demonstrated in simulations, and the beamformer accurately maintains its look direction while nulling out interferers

MVDR broadband beamforming using polynomial matrix techniques

This paper presents initial progress on formulating minimum variance distortionless response (MVDR) broadband beamforming using a generalised sidelobe canceller (GSC) in the context of polynomial matrix techniques. The quiescent vector is defined as a broadband steering vector, and we propose a blocking matrix design obtained by paraunitary matrix completion. The polynomial approach decouples the spatial and temporal orders of the filters in the blocking matrix, and decouples the adaptive filter order from the construction of the blocking matrix. For off-broadside constraints the polynomial approach is simple, and more accurate and considerably less costly than a standard time domain broadband GSC

Butane Oxidation at Elevated Temperatures

Autoignition and oxidation of n-butane and iso-butane mixtures in air were studied in a shock tube at conditions where few data exist, namely at temperatures above 1100 K and for undiluted fuel-air mixtures. The experiments were performed in the reflected-shock region over the temperature range of 1150 - 1470 K, an average pressure of 1.45 atm, and equivalence ratios of 0.5 and 1.0. Ignition delay times were obtained for mixtures of n-C4H 10/iso-C4H10 in the ratios of 100/0, 0/100, and 50/50. Ignition was determined from the pressure trace measured at the shock-tube endwall. Effect of composition, stoichiometry and temperature were explored for the mixtures. Under all conditions, normal butane was shown to be more readily ignitable than its isomer iso-butane. The experimental results should serve as validation to chemical kinetics mechanisms containing at least C4Hx hydrocarbons that lack benchmark data, especially at elevated temperature conditions