Details of Grant 

EPSRC Reference:	GR/J66836/01
Title:	DIFFUSE SCREENED ROOMS USING PSEUDO RANDOM PHASE REFLECTION GRATINGS
Principal Investigator:	Marvin, Professor AC
Other Investigators:	Angus, Professor JAS Dawson, Dr JF
Researcher Co-Investigators:
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Department:	Electronics
Organisation:	University of York
Scheme:	Standard Research (Pre-FEC)
Starts:	01 April 1994	Ends:	31 March 1997	Value (£):	163,704
EPSRC Research Topic Classifications:	Electromagnetics
EPSRC Industrial Sector Classifications:
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Summary on Grant Application Form
To investigate the utility of using pseudo random reflecting surfaces in screened rooms used for EMC measurements To investigate the applicability of this technique to enhance EMC measurementsProgress:Reverberant screened rooms used for EMC measurements are required to have a high resonant mode density in order that the modes can be mechanically or electronically stirred to fully exercise the equipment under-test (EUT). This mode density requirement limits the lowest frequency of operation of a room used in this way. We have shown experimentally and by simulation that the application of binary pseudo-random phase reflection gratings to the room walls enhances the low frequency mode density. Our current work is aimed at understanding the requirements for optimum gratings and developing grating synthesis techniques. We use a scale model screened room (0.9m x 0.45m x 0.45) for our measurements and the Transmission Line Matrix (TLM) algorithm for the simulations of the rooms.To date we have concentrated on binary (two level) gratings and have developed a metric that relates the free space scattering of the grating to the mode density increase. The metric compares the variance of the free space grating scattering from that of a completely diffuse scattering surface, computed at a number of selected frequencies, with the mode density increase in the screened room when the grating is applied to a room wall. The free space scattering is fast to compute and an optimisation routine has been devised that minimises this variance and gives an optimum set of gratings. Measured and computed screened room results indicate that the technique is effective [ 1 ] . Further work will concentrate on the effects of room contents in the form of antennas and EUTs and the stirring requirements for the treated rooms. A number of publications is in press. An example already published is given below [ [1] Reference [1] A.C. Marvin, J. Clegg, J.A.S Angus & J.F. Dawson. Enhancements to stirred mode chambers by the use of pseudo-random phase reflection gratings Proceedings of the EMC94 ROMA International Symposium on EMC. Rome, 13-16 Sept 1994.
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