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Sun-Tracking Millimeter Wave Radiometer




OBJECTIVE: Design and implement a sun-tracking radiometer system to measure millimeter wave attenuation with high dynamic range and temporal resolution. Threshold values are 30 dB dynamic range and 5 second resolution. 


DESCRIPTION: Development of new satellite communications capabilities in the allocated V and W frequency bands of 71-76 GHz and 81-86 GHz require the measurement of the atmospheric attenuation characteristics at these frequencies. This includes measurement of the fade dynamics and attenuation statistics. There is a dearth of relevant data at millimeter wave frequencies available to test or develop predictive models and fade mitigation techniques. The usual approach to collecting attenuation data utilizes beacons from satellites in geo-stationary orbits, which is expensive and can take many years to implement. On the other hand, the quiet sun is a source of millimeter waves that can be exploited to provide much needed data at a low cost and flexibility in site location. Sun-tracking techniques employing radiometers to measure atmospheric attenuation were developed and utilized by a few researchers in the 1960s and 1970s. However, there has been little if any use of the sun-tracking approach since and there is currently little familiarity with this technique. Radiometer systems have improved significantly in recent years, but there are no commercially available systems designed to provide sun-tracking measurements. Recently the radiometric sun-tracking technique has been re-introduced (see refs 3-5). But those measurements were made with a modification of a commercial radiometer and not optimized for sun-tracking measurements. The topic seeks the design and implementation of a stand-alone sun-tracking based system that can measure millimeter wave attenuation over a dynamic range greater than 30 dB with a 3 second minimum temporal resolution. The system should be capable of measuring at least two frequencies simultaneously (nominally 73 and 83 GHz) under most atmospheric and weather conditions including rain and snow. The system should include all sensors (such as meteorological instruments) and algorithms needed for stand-alone operation. It should be designed to operate over a broad range of elevation angles; from at least 10° to 90°. The sensor should be designed to operate with minimal direct operator control. These radiometer systems will provide key data needed to define V and W band satellite communication system architectures. Multiple units will be required to collect the attenuation characteristics at a variety of geographic locations. While this topic addresses specific frequencies, the sun-tracking radiometer system may be easily adapted for use with other frequencies of interest. It would for example be useful in the commercial development of Q and V band (40 and 50 GHz) satellite communication systems for which there is growing interest but little data. This type of measurement system can be utilized as a research tool for radio astronomy to provide valuable sun brightness temperature estimates which is almost unexplored beyond Ku band. 


PHASE I: The Phase I effort will conduct analysis to determine the an optimal design sensing strategy and expected performance. Critical engineering challenges will be identified. 


PHASE II: The Phase II effort should demonstrate the expected system performance. It should build and deliver a complete prototype system. 


PHASE III: Commercialize production based on Phase II prototype to provide additional features and capabilities of general interest. Produce a multitude of units in order to perform measurements at a variety of geographic locations. 



1: Croom D. (1973), "Sun as a broadband source for tropospheric attenuation measurements at millimetre wavelengths", Proc. IEE, vol 120, 1200-1206.

2:  Hogg, D.C. and T. Chu (1975): "The role of rain in satellite communications", Proc. IEEE, 63, 1308-1331.

3:   Mattioli V., F.S. Marzano, A.V. Bosisio, G.A. Brost, K.M. Magde, "High-frequency prediction of rain attenuation from ground-based microwave radiometric measurements through a sun-tracking technique", 14th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), Espoo (Finland), April 11-14, 2016.

4:  Marzano F.S., L. Milani, V. Mattioli, K. Magde, G. Brost, "Retrieval of precipitation extinction using ground-based Sun-tracking millimeter-wave radiometry", IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Beijing (China), July 10-15, 2016.

5:  Brost, G and K.M. Magde, "On the Use of the Radiometer Formula for Atmospheric Attenuation Measurements At GHz Frequencies", European Conference on Antennas and Propagation (EuCAP), Davos, April 11-14, 2016.



KEYWORDS: Sun-tracking, Radiometer, Propagation 


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