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Details of Grant 

EPSRC Reference: GR/H78702/01
Principal Investigator: Sandler, Professor M
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Department: Electronic Engineering
Organisation: Kings College London
Scheme: Standard Research (Pre-FEC)
Starts: 11 March 1993 Ends: 10 August 1996 Value (£): 133,395
EPSRC Research Topic Classifications:
Digital Signal Processing
EPSRC Industrial Sector Classifications:
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Summary on Grant Application Form
To investigate novel Sigma Delta Modulation Architectures which incorporate adaptive elements and to evaluate the various approaches for improved performance (signal to noise ratio, dynamic range), improved stability and hardware feasibility. Progress:Substantial investigations have been performed into the performance improvements when the output levels from the single bit quantiser in the SDM loop are adapted in line with estimated signal statistics. Preliminary results were reported in IEE Transactions in 1992. These have been and continue to be extended. This aspect of the work also encompasses adaptation of the loop filter coefficients and new results are expected in this area before the end of 1995 - psychoacoustically relevant adaptation is also of concern here.Simulators for SDMs have been developed for PC and Sparc platforms. These include optimising design approaches and extended to include dither and pole/zero locations as optimisation parameters. They will optimise peak SNR, or average SNR over a range of input levels. The primary technique used to measure performance of SDMs in this simulator is based on the use of Maximal Length Sequences, which enable both linear and non-linear responses to be estimated. Other aspects reported in the papers mentioned below include: the use of clipping within SDMs to control quantiser overload and thus improve performance; detailed comparison of dither and 'Chaotic modulation' to control and eliminate idle tones and noise modulation. This has attracted industrial interest from the USA and Denmark. Another connected aspect of this project, is the direct adaptation of the bitstream as it is generated within the SDM loop. This gives rise to numerous alternative modulator structures, each with its own specific properties. This has led to one paper which deals with Pulse Inversion Modulation: the related technique, Pulse Group Modulation, is being written for imminent submission to a journal. A further derivative is being written as a Patents Application, so publication on this topic, a highly efficient method for injecting dither into a SDM, will be delayed. So far, there have been seven publications over the life of this grant.
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