Broadband beamforming of dense aperture array (DAA) and focal plane array (FPA) signals using 3D spatio-temporal filters for applications in aperture synthesis radio astronomy

摘要

It is shown that 3D spatio-temporal filters have potential applications in aperture synthesis radio astronomy for the broadband-beamforming of the array of signals that is received from dense aperture arrays (DAAs) and also from focal plane arrays (FPAs). In particular, we consider possible applications for the planned Square Kilometer Array (SKA) project where broadband beamforming is required at the front-end of the signal processing system for some experiments such as pulsar timing. In the case of a synthesized aperture that is composed of DAAs, the required 3D magnitude frequency response has a non-separable narrow-cone-shaped (or narrow-frustum-shaped) passband whereas, for FPAs, the required 3D magnitude frequency response has a non-separable wide-cone-shaped (or wide-frustum-shaped) passband. The corresponding 3D passbands are designed to faithfully transmit the celestial signals of interest (SOIs), whereas the 3D stopbands are designed to significantly attenuate such undesired signal components such as natural and artificial sources of radio frequency interference (RFI) and the dominant part of the 3D electronic broadband noise that is contributed by millions of low noise amplifiers (LNAs), each of which amplifies the signal received in each elemental antenna of the DAAs or FPAs. The criteria for designing both narrow- and wide-cone/frustal filters, in order to achieve optimal sensitivity, are presented in terms of the power of the recovered signal and the power of the contaminating noise.