Formulation of optimum beam space processing for directional transmission phased array systems

Standard beam space processing algorithms, such as minimum variance distortionless response, normally assume that the transmitter is omni-directional, and hence are mismatched when the transmitter is directional. This paper derives a new formula for the case of directional transmission. An example shows that the new formula achieves significantly better performance than the standard beam space formula when the transmission is via directional beams. Also, the idea of adding virtual beams to reduce the response to out of sector signals is proposed. Finally, the applicability of the algorithm for non-stationary scatterers is examined.Ruiting Yang, Douglas A. Gray and Waddah A. Al-Ashwa

Low phase noise frequency synthesis for ultrastable X-band oscillators

In this letter, the design of a low phase noise frequency synthesizer is presented. The synthesizer was designed to produce four frequencies: 10 MHz, 100 MHz, 1 GHz and 10 GHz. The 1-GHz signal is produced by frequency division whereas the 100-MHz output is generated by phase-locking a low phase noise oscillator to the 1-GHz signal, hence significantly reducing its phase noise. Both residual and total phase noise measurements are presented.Waddah A. Al-Ashwal, Ashby Hilton, Andre N. Luiten, and John G. Hartnet

Preliminary analysis of monostatic and bistatic Doppler signature of small maritime target

The simultaneous bistatic and monostatic Doppler signatures of a small boat are measured and analyzed. The data was recorded using the UCL NetRAD 2.4 GHz netted radar system. Two datasets are presented: one at small bistatic angle (~ 4degree(s)) and the other at a larger angle (~ 91degree(s)). There was little difference between the monostatic and bistatic channels in the former, while there were significant differences in the latter. In addition, by using detections from both channels the true velocity of the target is estimated.Waddah A. Al-Ashwal, Hugh D. Griffith

An empirical model for bistatic sea clutter normalised radar cross section

A new model for describing bistatic sea clutter based on monostatic measurements is presented. The model is applied to both in-plane and out-of-plane bistatic geometries. The model was able to fit both data collected by University College London and that reported by other researchers.W.A. Al-Ashwal, H.D. Griffiths and K. Woodbridg

Analysis of Bistatic Sea clutter – part II: amplitude statistics

The amplitude statistics of simultaneously recorded bistatic and monostatic sea clutter are analyzed and fitted to five different commonly used distributions to model sea clutter. We find that under the measurement conditions the bistatic geometry reduced the effect of specular spikes but not those due to the modulation. It was found that the bistatic geometry could offer significant advantages in detection particularly at horizontal polarization and close to a bistatic angle of 90 °.Waddah A. Al-Ashwal, Karl Woodbridge, Hugh D. Griffith

Analysis of bistatic sea clutter - Part I: Average reflectivity

Based on two low grazing angle simultaneously recorded out-of-plane bistatic and monostatic S-band sea clutter datasets, and covering bistatic angles from 30°-120°, we analyze the average normalized radar cross section (σ°), and show that under the measurement conditions the ratio between σB° and σM° tends to a minimum around a bistatic angle of 90°, particularly at horizontal polarization. However, the cross-polarized σ° was larger for the bistatic clutter at bistatic angles close to 90°.Waddah A. Al-Ashwal, Karl Woodbridge, Hugh D. Griffith

Coherent analysis of horizontally-polarized monostatic and bistatic sea clutter

This paper compares the statistical properties of multiple simultaneous recordings of coherent monostatic and bistatic sea clutter data at two different bistatic angles. Differences in the Doppler spectra characteristics are highlighted as well as quantifiable amplitude statistics differences between the monostatic and bistatic data at each angle.M.A. Ritchie, W.A. Al-Ashwal, A.G. Stove, K. Woodbridge and H.D. Griffith