For uniform frequency stepped pulse trains, there can be undesirable peaks of the autocorrelation function, known as "grating lobes". In this paper we address this issue, using an approach which allows us to suppress grating lobes below a desired threshold level in the case of appropriately chosen stepped frequency waveforms, i.e., sequences of narrowband pulses that span the desired bandwidth. We discuss in detail how to choose relevant parameters in order to produce such waveforms with small grating lobes, and give examples of waveforms with small overlap ratio. We also discuss the issue of high sidelobes in the vicinity of the main lobe, which are inevitable in a train of LFM waveforms, and show that it is possible to suppress these, as well as the grating lobes, by means of phase modulation.
I. GLADKOVA CCNY D. CHEBANOV CUNY Frequency stepping is one of the known techniques employed by modern radars to achieve high range resolution. The main advantage of this approach is that the actual instantaneous bandwidth of a radar is quite small compared with the total processing bandwidth. This allows the transmission of waveforms with extremely wide overall bandwidth (and, as a consequence, the attainment of high range resolution) without the usage of the expensive hardware needed to support wide instantaneous bandwidth. Unfortunately, the autocorrelation function of uniform frequency stepped pulse trains can have undesirable peaks, known as "grating lobes." We address this issue, using an approach which allows us to suppress grating lobes below a desired threshold level in the case of appropriately chosen stepped frequency waveforms. We discuss in detail how to choose relevant parameters in order to produce such waveforms with small grating lobes, and give examples of waveforms with small overlap ratio. We also discuss the issue of high sidelobes in the vicinity of the mainlobe, which are inevitable in a stepped frequency train of linear frequency modulated (LFM) waveforms with small overlap ratio, and show that it is possible to suppress these, as well as the grating lobes, by means of nonlinear frequency modulation (NLFM).
In this paper we propose a new multi-strategy model for immersing students in STEM. Rooted in the current research and experiences, the new practices are being developed and implemented in a college-based hybrid STEM learning center that is geared to serve as a hub connecting high schools, higher education institutions, and industries bringing new and existing strategies together into one integral system with unique online features. The Hub model would serve as an educational research laboratory contributing to the knowledge base about STEM by investigating what strategies (or combination of what strategies) will best support student development for the STEM workforce. In addition, the model would illustrate the importance of interconnection between engineering education research and engineering education practice.
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