tailieunhanh - Fourier Transforms in Radar And Signal Processing_2

cân bằng, và phản ứng rải rác đối với trường hợp bồi thường chậm trễ số nguyên (trong đơn vị của khoảng thời gian lấy mẫu). [Hình (a), đường cong này là giống hệt với đường cong tiêu tan, như tất cả các sự chậm trễ trong vòng ± 0,5 khoảng thời gian lấy mẫu, vì vậy không có bồi thường số nguyên là khả thi. | Introduction 9 spond to the samples that would have been obtained by sampling the waveform with the time offset. The ability to do this when the waveform is no longer available is important as it provides a sampled form of the delayed waveform. If the waveform is sampled at the minimum rate to retain all the waveform information accurate interpolation requires combining a substantial number of input samples for each output value. It is shown that oversampling sampling at a higher rate than actually necessary can reduce this number very considerably to quite a low value. The user can compare the disadvantage if any of sampling slightly faster with the saving on the amount of computation needed for the interpolation. One example from a simulation of a radar moving target indication MTI system is given where the reduction in computation can be very great indeed. The problem of compensating for spectral distortion is considered in Chapter 6. Compensation for delay a phase error that is linear with frequency is achieved by a technique similar to interpolation but amplitude compensation is interesting in that it requires a new set of transform pairs including functions derived by differentiation of the sinc function. The compensation is seen to be very effective for the problems chosen and again oversampling can greatly reduce the complexity of the implementation. The problem of equalizing the response of a wideband antenna array used for a radar application is used as an illustration giving some impressive results. Finally in Chapter 7 we take advantage of the fact that there is a Fourier transform relationship between the illumination of a linear aperture and its beam pattern. In fact rather than a continuous aperture we concentrate on the regular linear array which is a sampled aperture and mathematically has a correspondence with the sampled waveforms considered in earlier chapters. Two forms of the problem are considered the low side-lobe directional beam and a much