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WERA History


The WERA system is a new development carried out in 1995 at the University of Hamburg by Klaus-Werner Gurgel et al and the hardware development was completed in 2000 at Helzel Messtechnik GmbH.

The WERA system (WavE RAdar) is a shore based remote sensing system using the over the horizon radar technology to monitor ocean surface currents, waves and wind direction. This long range, high resolution monitoring system operates with radio frequencies between 5 and 50 MHz. A vertical polarised electromagnetic wave is coupled to the conductive ocean surface and will follow the curvature of the earth. The rough ocean surface interacts with the radio wave and due to the Bragg Effect back-scattered signals can be detected from ranges of more than 200 km.

The Bragg effect describes the coupling of the electromagnetic wave with the ocean wave field. Reflections from waves that fulfil this Bragg conditions will generate a dominant signature in the received signal spectrum due to in-phase summation of amplitudes. The expected signature is a Doppler shifted signal with a specific Doppler Shift given by the velocity of the according gravity wave.These Doppler shifted signals will be symmetrical around the normalised centre frequency, as long as the ocean surface does not move. An ocean current will shift these Bragg peaks up or down in frequency. This additional frequency shift contains the information used to calculate the velocity of the ocean current. This effect was first described in 1955 by Crombie and the first radar system using that effect was developed at NOAA in 1977 by Don Barrick et al.

The WERA system is a
new development carried out in 1995 at the University of Hamburg by Klaus-Werner Gurgel et al and the hardware development was completed in 2000 at Helzel Messtechnik GmbH.

The WERA system is operating in a frequency modulated continuous wave mode (FMcw). A continuously swept rf-signal is transmitted. The reflected signal has a frequency offset compared to the actual transmitted signal, thus the range is frequency encoded.

The radar is continuously transmitting very low rf power, no gating or pulsing sequences are used. The required de-coupling between transmitter (Tx) and receiver (Rx) has to be achieved by means of using separate locations for Rx and Tx antennae. These systems provide best signal to noise performance due to the extreme low noise FMcw transmission mode.

 



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