Mobile radars

NOXP radar for Durango 2009 and Gunnison 2010


Rapid-scan Doppler radar for TOM: Teaching flow Over Mountains 2011

The following text is taken from the Center for Severe Weather Research Website:

Rapid evolution and small-scales are tightly linked, and since data from the DOWs suggested that observations of phenomena associated with tornadogenesis, microbursts and hurricane boundary layer wind streaks are poorly resolved by conventional scanning radars and even conventional mobile radars (due to spatial and temporal limitations, respectively), rapid-scan and mobility go hand in hand.

Although historically, phased array rapid-scan technologies have been prohibitively expensive, in 2001, CSWR began developing an experimental rapid-DOW, capable of scanning with a multiple beam system to collect partial volumetric data in approximately 10 seconds. Operating, the rapid-DOW incorporates a slotted waveguide array antenna, designed to produce frequency dependent beam steering. Energy from a single transmitter produces six pencil-beams, each with a distinct frequency and elevation angle, nearly simultaneously (see Figure 3 below.) The rapid mechanical azimuthal scanning results in a six-beam sweep of the sky in six seconds. company Fig 3. Beam dispersion from nearly simultaneously transmitted beams and simultaneously received beams. In operation, the antenna is quickly scanned manually in asimuth and stepped through a coarse elevation pattern.

The antenna array, approximately 2.4 m on a side, consists of individual slotted waveguide elements (See Figure 4 below.) At any given frequency, the array produces a 0.9°-1.0° beam. All returned signals pass through single rotarysjoints, circulator, and amplifier and initial IF downconversion, before being split and sent to individual frequency modules (channels). company Fig. 4. Rapid-DOW slotted waveguide array, producing multiple pencil beams. Waveguides are fed by a sinuous feed oriented vertically.

Steering is approximately .03° (MHz)-1, producing approximately 15° steering across the X-band spectrum (9.3-9.8 GHz). Pulse lengths as short as 125 ns result in negligible dispersion (8MHz effective bandwidth results in just .24°dispersion) within individual beams. Minimum frequency separations can be adjusted depending on pulselengths in order to provide channel isolation.

Returned energy from all of the beam is received simultaneously, then split and processed by individual frequency modules, and the frequency of each individual beam is independently controlled by individual synthesizers in each frequency module. By changing the frequencies of the transmitted energy, the elevation angle offsets of the individual beams can be modified, allowing elevation angle offset sets to be tailored for boundary layer or deep convective studies. The elevation angle of any beam can be changed on a integration-time-by-integrationtime basis, permitting saw-toothed or dithered scans. This permits a better matching of horizontal and vertical observation scales.