Flexible loop filter design for spacecraft phase-locked receivers

A flexible loop filter design for spacecraft phase-locked receivers is proposed. The loop filter is implemented as digital hardware with coefficients that are set by registers. Either a perfect or an imperfect integrating loop filter can be effected. This flexibility is important since not one type of loop filter is preferred for all circumstances. An imperfect integrator is preferred when, as is often the case for spacecraft receivers, it is important to minimize the best-lock frequency drift of an idling loop. A perfect integrator is preferred when the tracking performance of the loop is the most important consideration     

Measurements, visualization and interpretation of 3-D flowsapplication within base flows

Experimental investigations of the flow field in the near-wake of axisymmetric afterbodies at an angle of attack of 5° are reported. Models consists of a cylindrical afterbody and a conical boat tail. Measurements were performed by means of a 3-D frequency-shifted laser Doppler velocimeter at a free stream Mach number of 0.5. The tremendous increase of quantitative information obtained with this diagnostic technique raises the problem of reducing and displaying the data in a way that avoids large amounts of numbers and curves that are not easy to interpret. An attempt is made to visualize and to describe velocity characteristics in the form of a 3-D graphic representation