Brian D. Jeffs

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Most previously proposed statistical models for the indoor multipath channel include only time of arrival characteristics. However, in order to use statistical models in simulating or analyzing the performance of array processing or diversity combining, it also necessary to know the statistics of the angle of arrival and its correlation with time of(More)
Multiple antenna systems are a useful way of overcoming the effects of multipath interference, and can allow more efficient use of spectrum. In order to test the effectiveness of various algorithms such as diversity combining, phased array processing, and adaptive array processing in an indoor environment, a channel model is needed which models both the(More)
LOFAR is a low-frequency radio astronomical array currently under development in The Netherlands. It is designed to produce synthesis images of the most distant celestial objects yet observed. Due to high redshift levels, observations must be at unusually low frequencies (30-240 MHz), over large apertures (100 km), using thousands of antennas. At these(More)
Detailed performance assessment of space–time coding algorithms in realistic channels is critically dependent upon accurate knowledge of the wireless channel spatial characteristics. This paper presents an experimental measurement platform capable of providing the narrowband channel transfer matrix for wireless communications scenarios. The system is used(More)
Most current indoor propagation experiments measure the time of arrival of characteristics of multipath reflections without regard to angle of arrival. Because of the increasing number of systems that are used indoors and which use multiple antenna systems to combat multipath interference, a need exists for indoor propagation data which takes angle of(More)
Figure 1 depicts a block diagram of the entire system. Photographs of the actual transmit and receive systems on carts is depicted in Figure 2. Details on RF components are identical to those described in [2]. Transmit symbols for four independent data streams are generated on the embedded PC, converted into complex baseband signals, and passed via the VME(More)
The problem of removing blur from, or sharpening, astronomical star field intensity images is discussed. An approach to image restoration that recovers image detail using a constrained optimization theoretic approach is introduced. Ideal star images may be modeled as a few point sources in a uniform background. It is argued that a direct measure of image(More)
Relative to traditional waveguide feeds, phased array feeds (PAFs) for radio telescopes can increase the instrument field of view and sky survey speed. Unique challenges associated with PAF observations, including extremely low signal levels, long-term system gain stability requirements, spatially correlated noise due to mutual coupling, and tight beamshape(More)
We consider the use of spatial filtering algorithms for radio frequency interference (RFI) mitigation in conjunction with a focal plane feed array of electrically small elements. Numerical simulations are used to study the performance of 7 and 19 element hexagonal dipole arrays with a 25 meter reflector at an operating frequency of 1612MHz. Using the(More)