Ron Brown Project

This new radar wind profiler design incorporates 3 significant improvements over existing ship-borne profilers:

1. Low Sidelobe Antenna
   • Improved sea clutter rejection.

2. Electronic Stabilization
   • Fully steerable antenna (0to 31.5 off-zenith for all azimuths)
   • 10 Hz switching frequency compensates for ship motion.
   • Smaller size (2.7 m dia. x 1.2 m tall).

3. Signal Processing System
   • Improved peak detection, sea clutter & RFI rejection, and 3-D continuity checks.

Electronic Stabilization
The radar computer determines the nominal beam direction (typically 0 to 15 off-zenith in one of 2 or more azimuthal directions) and communicates its choice to the motion control and monitor (MCM) computer which steers the phased-array antenna beam to the desired pointing angle while measuring and compensating in real time for the ship motion. The antenna beam position is updated at a 10 Hz rate to accommodate maximum ship roll rates.

In order to electronically steer the beam, the RF signal to be transmitted is split and distributed to each of the elements which shift the phase of the signal based on their position in the array and the desired beam pointing direction. Received signals are likewise phase-shifted and combined. The Motion Control and Monitor (MCM) will steer the radar through electronic phasing of 90 individual radiating elements taking into account the requested pointing angle and the ship's motion.

Click here for a short demonstration (.avi 3Mb) of the antenna pointing utilizing real ship's motion data.

The first half of the video shows compensation with static radar pointing, the second half with dynamic manual radar pointing (watch the mouse arrow to see changes in settings).The individual radiating elements are represented by the small arrayed squares, with their color representing the required phase. The pointing direction on the polar coordinates overlay is shown by a blue circle indicating the desired earth-relative direction, and a yellow circle indicating the compensated pointing direction.

This module contains the microcontroller, the RF circuitry, and the element antenna. Although the antenna elements are all physically identical, each is programmed with a unique identification address and phase control look up table appropriate for its location in the array.

Simulations indicate that, with careful control of amplitude and phase errors and losses, low-elevation (0 to 10) sidelobes may be held to -40 to -30 dB relative to the main beam for scan angles less than 15to 30, respectively.

Calculated antenna gain pattern for a beam steered 21 degs. from vertical.

Please direct any comments or questions to MJ Post or Daniel Law or Scott McLaughlin

Last update: December, 2000

RMOD Home Page