32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Thursday, 7 August 2003
Status of the IfT semiconductor based 94GHz FM-CW Doppler radar profiler project
Dirk Klugmann, Institute for Tropospheric Research, Leipzig, Germany; and J. Weickert
A 94GHz FM-CW (Frequency Modulated Continuous Wave) Doppler radar cloud profiler is hosted at the Institute for Tropospheric Research (IfT) in Leipzig. The robust and durable radar front-end is a monostatic system (common antenna for transmitted and received signal) with an average transmitted power of about 350mW. The generation of transmitted power is based exclusively on semiconductor elements. The amplifier stage is composed by a power combiner featuring two power IMPATT diodes.

Semiconductor based millimeter wave radars feature a number of advantages over systems based on vacuum tube technology. The most significant is the virtual infinite life time of the applied devices. Besides, semiconductor based radars are more compact and light weight due to the lack of high power voltage supply, and can be manufactured and operated at lower costs than radars based on vacuum tube technology. These advantages - especially for airborne application - compensate the disadvantage of the lower sensitivity, which semiconductor based millimeter wave radars show up to date.

The IfT 94GHz radar profiler has not been put into operation up to now due to a technical problem. One of the amplifier stage IMPATT diodes failed the burn-in test, so it had to be replaced. Due to this the complete amplifier had to be re-adjusted and re-tuned. Recently the repair of the radar front-end was finalized and the front-end was mounted in the system's temperature stabilized housing.

The sensitivity of the cloud profiler is estimated to be sufficient to detect weak drizzle and boundary layer Stratus clouds. For verification, the radar will be calibrated with a periodically moving calibration target. This approach will be explained, and results will be presented. Furthermore, an overview over first measurements of atmospheric targets will be given.

After having been put into service, the IfT 94GHz radar profiler will be run ground based next to some accepted cloud radars for inter-comparison. It also will be applied in field measurements and in some field campaigns. If the results will be satisfying, the radar system will be mounted in a research airplane during the next year.

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