瞬时测频(Instantaneous Frequency Measuring, IFM)接收机因其良好的测频性能已成为国内外雷达侦察系统广泛应用的测频接收机。现有的IFM接收机理论是建立在窄带单频信号通过IFM接收机的基础上,当前关于IFM接收机在多路宽带复杂信号环...瞬时测频(Instantaneous Frequency Measuring, IFM)接收机因其良好的测频性能已成为国内外雷达侦察系统广泛应用的测频接收机。现有的IFM接收机理论是建立在窄带单频信号通过IFM接收机的基础上,当前关于IFM接收机在多路宽带复杂信号环境下独立的测频性能方面缺少研究。首先,从理论上推导了多路宽带复杂信号环境下的IFM接收机的输出,指出IFM接收机对单路宽带信号的测频精度较高,而在多路宽带复杂信号环境下IFM接收机测频结果会受到较大影响,因此,IFM接收机无法适应多路宽带复杂信号环境。展开更多
Cone penetration testing (CPT) is a widely used geotechnical engineering </span><i><span style="font-family:Verdana;">in-situ</span></i><span style="font-family:Verdana;...Cone penetration testing (CPT) is a widely used geotechnical engineering </span><i><span style="font-family:Verdana;">in-situ</span></i><span style="font-family:Verdana;"> test for mapping soil profiles and assessing soil properties. In CPT, a cone on the end of a series of rods is pushed into the ground at a constant rate and resistance to the cone tip is measured (</span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;">). The </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;"> values are utilized to characterize the soil profile. Unfortunately, the measured cone tip resistance </span></span><span style="font-family:Verdana;">is</span><span style="font-family:""><span style="font-family:Verdana;"> blurred and/or averaged which can result in the distortion of the soil profile characterization and the inability to identify thin layers. This paper outlines a novel and highly effective algorithm for obtaining cone bearing estimates </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub></i><span style="font-family:Verdana;"> from averaged or smoothed </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;"> measurements. This </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub></i><span style="font-family:Verdana;"> optimal filter estimation technique is referred to as the </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub><span style="font-family:Verdana;">HMM-IFM</span></i><span style="font-family:Verdana;"> algorithm and it implements a hybrid hidden Markov model and iterative forward modelling technique. The mathematical details of the </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub><span style="font-family:Verdana;">HMM-IFM</span></i><span style="font-family:Verdana;"> algorithm are outline</span><span style="font-family:Verdana;">d in this paper along with the results from challenging test</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">bed. The test</span><span style="font-family:""> </span><span style="font-family:Verdana;">b</span><span style="font-family:""><span style="font-family:Verdana;">ed simulations have demonstrated that the </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub><span style="font-family:Verdana;">HMM-IFM</span></i><span style="font-family:Verdana;"> algorithm can derive accurate </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub></i><span style="font-family:Verdana;"> values from challenging averaged </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;"> profiles. This allows for greater soil resolution and the identification and quantification of thin layers in a soil profile.展开更多
There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applica...There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applications demanding the rapid and precise transmission of diverse information from one point to another within a short timeframe. The ability to report a signal without tuning within the input bandwidth stands out as one of the advantages of employing a digital wideband receiver. As indicated, a digital wideband receiver plays a pivotal role in achieving high precision and accuracy. The primary distinction between Analog and Digital Instantaneous Frequency Measurement lies in the fact that analog Instantaneous Frequency Measurement (IFM) receivers have traditionally covered extensive input bandwidths, reporting one accurate frequency per short pulse. In the contemporary landscape, digital IFM systems utilize high-sampling-rate Analog-to-Digital Converters (ADC) along with Hilbert transforms to generate two output channels featuring a 90-degree phase shift. This paper explores the improvement of sensitivity in current digital IFM receivers. The optimization efforts target the Hilbert transform and autocorrelations architectures, aiming to refine the system’s ability to report fine frequencies within a noisy wide bandwidth environment, thereby elevating its overall sensitivity.展开更多
文摘瞬时测频(Instantaneous Frequency Measuring, IFM)接收机因其良好的测频性能已成为国内外雷达侦察系统广泛应用的测频接收机。现有的IFM接收机理论是建立在窄带单频信号通过IFM接收机的基础上,当前关于IFM接收机在多路宽带复杂信号环境下独立的测频性能方面缺少研究。首先,从理论上推导了多路宽带复杂信号环境下的IFM接收机的输出,指出IFM接收机对单路宽带信号的测频精度较高,而在多路宽带复杂信号环境下IFM接收机测频结果会受到较大影响,因此,IFM接收机无法适应多路宽带复杂信号环境。
文摘Cone penetration testing (CPT) is a widely used geotechnical engineering </span><i><span style="font-family:Verdana;">in-situ</span></i><span style="font-family:Verdana;"> test for mapping soil profiles and assessing soil properties. In CPT, a cone on the end of a series of rods is pushed into the ground at a constant rate and resistance to the cone tip is measured (</span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;">). The </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;"> values are utilized to characterize the soil profile. Unfortunately, the measured cone tip resistance </span></span><span style="font-family:Verdana;">is</span><span style="font-family:""><span style="font-family:Verdana;"> blurred and/or averaged which can result in the distortion of the soil profile characterization and the inability to identify thin layers. This paper outlines a novel and highly effective algorithm for obtaining cone bearing estimates </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub></i><span style="font-family:Verdana;"> from averaged or smoothed </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;"> measurements. This </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub></i><span style="font-family:Verdana;"> optimal filter estimation technique is referred to as the </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub><span style="font-family:Verdana;">HMM-IFM</span></i><span style="font-family:Verdana;"> algorithm and it implements a hybrid hidden Markov model and iterative forward modelling technique. The mathematical details of the </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub><span style="font-family:Verdana;">HMM-IFM</span></i><span style="font-family:Verdana;"> algorithm are outline</span><span style="font-family:Verdana;">d in this paper along with the results from challenging test</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">bed. The test</span><span style="font-family:""> </span><span style="font-family:Verdana;">b</span><span style="font-family:""><span style="font-family:Verdana;">ed simulations have demonstrated that the </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub><span style="font-family:Verdana;">HMM-IFM</span></i><span style="font-family:Verdana;"> algorithm can derive accurate </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">t</span></sub></i><span style="font-family:Verdana;"> values from challenging averaged </span><i><span style="font-family:Verdana;">q</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;"> profiles. This allows for greater soil resolution and the identification and quantification of thin layers in a soil profile.
文摘There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applications demanding the rapid and precise transmission of diverse information from one point to another within a short timeframe. The ability to report a signal without tuning within the input bandwidth stands out as one of the advantages of employing a digital wideband receiver. As indicated, a digital wideband receiver plays a pivotal role in achieving high precision and accuracy. The primary distinction between Analog and Digital Instantaneous Frequency Measurement lies in the fact that analog Instantaneous Frequency Measurement (IFM) receivers have traditionally covered extensive input bandwidths, reporting one accurate frequency per short pulse. In the contemporary landscape, digital IFM systems utilize high-sampling-rate Analog-to-Digital Converters (ADC) along with Hilbert transforms to generate two output channels featuring a 90-degree phase shift. This paper explores the improvement of sensitivity in current digital IFM receivers. The optimization efforts target the Hilbert transform and autocorrelations architectures, aiming to refine the system’s ability to report fine frequencies within a noisy wide bandwidth environment, thereby elevating its overall sensitivity.
