Aims. We describe a 6–12 GHz analogue correlator that has been developed for use in radio interferometers. Methods. We use a lag-correlator technique to synthesis eight complex spectral channels. Two schemes were considered for sampling the cross-correlation function, using either real or complex correlations, and we developed prototypes for both of them. We opted for the “add and square” detec...

In time delay estimation the correlator or, equivalently, matched filter estimator is widely used. Examples of its usage can be found in the global positioning system (GPS), radars and code division multiple access (CDMA) communication systems. Although widely used its performance is not studied in general case until recently. Partially this study is done in this thesis. If interfering signals ...

A bstract Conformal field theory (CFT) dispersion relations reconstruct correlators in terms of their double discontinuity. When applied to the crossing equation, such dispersive transforms lead sum rules that suppress double-twist sector spectrum and enjoy positivity properties at large twist. In this paper, we construct CFT functionals for unequal scalar operators position- Mellin-space. We t...

Of all the anticipated imaging problems to be undertaken by the EVLA, the most demanding, both in terms of data rate, data storage and post-processing, will likely be that of wide-band, wide-field imaging imaging the entire antenna primary beam with the full bandwidth. In this memo, I summarize the correlator requirements for various observing scenarios with the EVLA: distortion-free imaging of...

Our previously reported survey of the Low Earth Orbit (LEO) environment using Murchison Widefield Array (MWA) detected over 70 unique Resident Space Objects (RSOs) multiple passes, from 20 h observations in passive radar mode. In this paper, we extend work by demonstrating two methods that improve detection sensitivity system. The first method, called shift-stacking, increases statistical signi...

We consider the persistence probability, the occupation-time distribution, and the distribution of the number of zero crossings for discrete or (equivalently) discretely sampled Gaussian stationary processes (GSPs) of zero mean. We first consider the Ornstein-Uhlenbeck process, finding expressions for the mean and variance of the number of crossings and the "partial survival" probability. We th...

It appears that string-M-theory is the only viable candidate for a complete theory of matter. It must therefore contain both gravity and QCD. What is particularly surprising is the recent conjecture that strongly coupled QCD matrix elements can be evaluated though a duality with weakly coupled gravity. To date there has been no direct verification of this conjecture by Maldacena because of the ...

Modern graphics processing units (GPUs) are inexpensive commodity hardware that offer Tflop/s theoretical computing capacity. GPUs are well suited to many compute-intensive tasks including digital signal processing. We describe the implementation and performance of a GPU-based digital correlator for radio astronomy. The correlator is implemented using the NVIDIA CUDA development environment. We...