A complete behavioral model of radiation-pattern characteristics of phased array using a novel digital phase shifter
A complete and behavioral model for radiation-pattern characteristic of phased array has been presented. The model has many input parameters and it has a lot of features, such as parameter simulations with results analysis, unconventional two-dimensional color graph representation capability in order to show more clearly the results. It is an optimum instrument to investigate the performance of a beam-former in relation with an analogue phase shifter, ideal digital phase shifter, simulated real phase shifter and measured real phase shifter. Measured values of three different prototype of the proposed phase shifter architecture have been used in order to study the performances of the same architecture.
Granularity of beam positions in digital phased arrays
Many phased arrays are designed to use digital or digitalized phase shifters in which the phase shift varies in discrete steps rather than continuously. In such cases, the beam can be steered only in discrete steps. Granularity, defined as the finest realizable increment between adjacent beam positions, is an important parameter in the description of the performance of a phased array antenna using digital phase shifters. Two approaches to the problem of determining granularity are developed in this paper. The first is based upon the expansion by its moments of complex aperture distribution functions; the second is based upon approximating the actual discrete phase distribution by a linear continuous one. Results of the two approaches are shown to be in excellent agreement, with a variation of less than 3.6 percent being obtained. Arrays employing binary digital phase shifters are explicitly considered, but the techniques can be generalized to other types of digital, or digitalized, phase shifters. For other than the first beam position, there are alternate phase distributions which might be used to obtain a given beam position. The selection of a specific phase distribution depends, at least in part, upon the computer logic and round-off procedures. It is shown that these alternate phase distributions do not produce large differences in the beam position. The spread in beam position is between 2 and 3 percent for the alternate distributions. The effect of an amplitude taper on granularity is also considered. It is found that when the edge elements are less intensely illuminated than those at the center, the first beam position off-broadside is nearer broadside than for an array having the same phase distribution but uniform amplitude. The average granularity of a phased array has been determined, and is plotted against the number of elements with the number of phase bits as a parameter.
Kinemamtic analysis of flying-saw vehicle
The paper analyzes the kinematic motion of the flying-saw vehicle.After the analysis,it is concluded that the ac- celerating periods and decelerating periods in both forward and backward directions will follow sin~2αcurve and,in order to increase the sawing dimensional accuracy,flying-saw vehicle must come back as soon as possible while acceleration remains constant.Based on this premise,the paper gives out the equations of kinematic motion of the flying-saw vehicle in every sta- ges and one example result in a common situation.By now this method has been used in the real situation.