| EPSRC Reference: |
GR/H41607/01 |
| Title: |
MEASUREMENTS OF PHASE SCINTILLATIONS AND DYNAMICS OF AMPLITUDE FLUCTUATIONS AT 30 GHZ ( OLYMPUS ) |
| Principal Investigator: |
Vilar, Professor E |
| Other Investigators: |
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| Project Partners: |
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| Department: |
School of Systems Engineering |
| Organisation: |
University of Portsmouth |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
27 October 1992 |
Ends: |
26 October 1995 |
Value (£): |
48,050
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| EPSRC Research Topic Classifications: |
| RF & Microwave Technology |
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Summary on Grant Application Form |
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(1) To obtain experimentally and unambiguously the phase fluctuation function f(t) due to rain and scintillations in an Earth-space path in clear air and rainy conditions. Derive statistical distributions and expectations from the function f(t).(2) Analysis and modelling of fade time intervals for the purpose of fade dynamics. Parameters of particular concern include duration of exceedances and return periods.(3) In the case of rainy conditions, comparative analysis of the fade dynamics with that of point precipitation rate.Progress:The feasibility study for the design of the experimental ground station to track the 40 GHz Italsat beacon has been completed together with the calculations for the expected levels of phase noise, amplitude and phase scintillations. At 40 GHz and clear air only, the medium induced phase noise was calculated to range between 1 x f-8/3 dBc/Hz down to10-3 x f-8/3 dBc/Hz, whereas the phase noise of the Italsat 40 GHz beacon was estimated at10-1 x f-3 dBc/Hz. f represents fourier frequency away from the carrier. Therefore the phase noise of the beacon should be significantly less than that of the medium for a proportion of the time (and mainly during the Summer). These initial estimates were obtained from the early work at lower frequencies. They will be verified and amended during the 1995 Summer campaign.A compact transportable station has been built, is currently undergoing tests at Portsmouth and consists of three main stages. The first is the microwave front end, compactly wrapped-up around a 45 dBi horn antenna and converting the carrier to a first if of 70MHz. This first i.f is sent to a portable I&Q complex demodulation unit. The exact frequency beat at the base band I&Q output is calculated by the third stage (electronic interface and computer) and used to periodically steer the second local oscillator to a very low frequency beat note and keep the 10.7MHz i.f. well within the 300Hz i.f. bandwidth. The third stage of the receiver consists of a commercial electronic interface box and a laptop computer. From the moment of mains power-up, the receiver operations are menu driven. The clear sky C/No is about 40dBHz. The post detection bandwidths (I&Q) are 100 Hz. The avoidance of a phase lock system permits operating down to a few dB S/N and contemplating all kinds of advanced signal processing techniques inclusive the averaging of many samples to increase the effective S/N and the detection of the carrier level (magnitude of the beat note ) at S/Ns <1. Experimental measurements will be selective and are due to be carried out starting this Spring and to go through the Summer and Autumn period. A fast response rain gauge will be used for the dynamic studies. They are likely to be carried out later-on in the Autumn. A system article has been submitted to the September EUMIC '95 in Bologna (Italy). Some difficulties have been experienced which have led to delays. They have included fifteen months for the appointment of a bursary researcher (sponsored by the Faculty) and deliveries of the very low phase noise first local oscillator and the 10.7MHz 300Hz if filter. It is expected that the main objectives will be accomplished by the end of the grant period.
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Key Findings |
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Potential use in non-academic contexts |
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Project URL: |
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| Further Information: |
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| Organisation Website: |
http://www.port.ac.uk |