Pragmatic Methods to Decide Filter Requirements
While digital filter design – given a filter specification - is very well covered in numerous works, the essential practical question of how to arrive at the filter specification from the application is largely ignored: so the practicing engineer is faced with a well developed design methodology, but very little information to guide in specifying what to design. Similarly, there is little information available to guide decisions on the hardware platforms that are suitable to implement such a specification – including balancing issues such as numeric precision, speed, cost and power consumption – to assess whether the requirement may be met in a cost effective way: so the practicing engineer has limited guidance in deciding whether the application requirement may be met at all given practical constraints. The result is that engineers have limited ability to quickly assess whether a filtering requirement can be met: and digital filters very often under- or over-perform and are often implemented on needlessly costly or power-hungry hardware platforms. This talk addresses these twin gaps in the filter designer’s toolbox and outlines, with specific methods and examples, how the specification for a digital filter may be arrived at from consideration of the application aim and requirement. It also describes, again with specific methods and examples, how to arrive at a specification for the hardware platform necessary to implement such a filter. It does not address the issue of designing such a filter, which is very well covered in numerous texts elsewhere.
DSP in Phased Array 3D Imaging
Phase is often the poor relation to magnitude in Fourier Transform analysis but can be the crucial measurement in some applications. Such is the case with phased array methods for imaging: in radar, security and medical imaging applications. The key to such applications is physics modelling and measurement of phase to reconstruct wave propagation and hence reconstruct 3D or 4D images of reflecting, refracting or scattering objects. This talk offers an overview of phased array imaging from the viewpoint of DSP, modelled as a 3D Fourier or Laplace Transform problem.