Contemporary signal processing combined with phased array technology using digital beamforming enables development of an important new radar system class that provides continuous and uninterrupted multifunction capability within a coverage volume. The central idea of Ubiquitous Radar is to ?look everywhere all of the time.? The concept requires illuminating a wide coverage volume while continuously receiving signals from a ?pincushion? of narrow beams filling the volume. There are no gaps either in coverage space or in time, so that all targets can be detected at the earliest time and tracks initiated. Conceptually this technology can combine surveillance, tracking and weapon control. Continuous coverage from close-in ?pop-up? targets in clutter to long-range targets impacts selection of waveform parameters. The CPI (coherent processing interval) must be long enough to achieve a signal-to-noise ratio significantly above 0 dB in order to efficiently perform non-coherent integration. The approach, sometimes termed ?track-before-detect? then accounts for range-walk and Doppler-slide to achieve a specified detection probability. The current state-of-the-art in digital processing technology, particularly the use of field programmable gate arrays (FPGAs), makes the concept feasible. The paper highlights the design of a surveillance and tracking system operating in L-band using a transmit array with 209 transmit elements each radiating 1 kW and a 1590 element receive array. The concept incorporates a digital receiver behind every element, a full digital beamformer producing 192 simultaneous receive beams and signal processing for every beam. Details concerning beamforming, waveform design, approaches to resolve range and Doppler ambiguities, effects of necessary long-time non-coherent integration, signal processing and false target rejection in the tracker are presented in detail.

It has been recently shown that multiple-input multiple-output (MIMO) antenna systems have the potential to dramatically improve the performance of communication systems over single antenna systems. Unlike beamforming, which presumes a high correlation between signals either transmitted or received by an array, the MIMO concept exploits the independence between signals at the array elements. In conventional radar, target scintillations are regarded as a nuisance parameter that degrades radar performance. The novelty of MIMO radar is that it takes the opposite view, namely, it capitalizes on target scintillations to improve the radar?s performance. In this paper, we introduce the MIMO concept for radar. The MIMO radar system under consideration consists of a transmit array with widely-spaced elements such that each views a different aspect of the target. The array at the receiver is a conventional array used for direction finding (DF). The system performance analysis is carried out in terms of the Cramer-Rao bound of the meansquare error in estimating the target direction. It is shown that MIMO radar leads to significant performance improvement in DF accuracy.

Scheduling is an important sub-problem of radar resource management as there is a strong correlation between how tasks should be carried out and the time available to perform them. In this paper, two scheduling algorithms presented in the literature are compared to investigate whether there are significant differences in their performance related to the allocation of radar time resources. We developed a radar model applying a modular architecture to use the same operating and environment conditions in the analysis. The results suggest that both algorithms provide similar performance, apart from minor differences explained here.

Future array-based RF transmit systems will require linear amplification to preserve the spectral integrity of simultaneously transmitted signals. Classical delta-sigma modulation, paired with an emerging class of high-power switches, can provide this linearity by using a high-speed, low-resolution quantizer and shaping the resulting quantization errors out of the signal band. The drawback is that high clock rates are required to achieve high SNR. Recently we have proposed jointly shaping quantization errors in temporal and spatial frequency, pushing quantization errors both out of band and to nonpropagating spatial frequencies. This provides greater SNR for a given clock rate or the same SNR at a reduced clock rate relative to conventional delta-sigma modulation, while retaining its characteristic high linearity. In this paper we present an overview of the spatio-temporal delta-sigma array architecture and present the results of some preliminary hardware experiments with a small linear array.

Here, we give an overview of some of the results of our analysis on anomalous scattering phenomena for structures involving metamaterial layers, and we provide some physical insights and ideas for potential applications.