Modulation Recognition Method Based on High Order Cyclic Cumulants for Time-Frequency Overlapped Two-Signal in the Single-Channel

Automatic modulation recognition plays a vital role in electronic warfare. Modern electronic intelligence and electronic support measures systems are able to automatically distinguish the modulation type of an intercepted radar signal by means of real-time intra-pulse analysis. This extra information can facilitate deinterleaving process as well as be utilized in early warning systems or give better insight into the performance of hostile radars. Existing modulation recognition algorithms usually extract signal features from one of the rudimentary waveform characteristics, namely instantaneous frequency (IF). Currently, there are a small number of studies concerning IF estimation methods, specifically for radar signals, whereas estimator accuracy may adversely affect the performance of the whole classification process. In this paper, five popular methods of evaluating the IF–law of frequency modulated radar signals are compared. The considered algorithms incorporate the two most prevalent estimation techniques, i.e., phase finite differences and time-frequency representations. The novel approach based on the generalized quasi-maximum likelihood (QML) method is also proposed. The results of simulation experiments show that the proposed QML estimator is significantly more accurate than the other considered techniques. Furthermore, for the first time in the publicly available literature, multipath influence on IF estimates has been investigated.

Download Full-text

Time-Frequency Analysis Using Warped-Based High-Order Phase Modeling

EURASIP Journal on Advances in Signal Processing ◽

10.1155/asp.2005.2856 ◽

2005 ◽

Vol 2005 (17) ◽

Cited By ~ 22

Author(s):

Cornel Ioana ◽

André Quinquis

Keyword(s):

Frequency Analysis ◽

High Order ◽

Time Frequency Analysis ◽

Time Frequency

Download Full-text

Analysis of Vibration Signals in Monitoring Titanium End Milling Process Using Triaxial Accelerometer

Volume 1: Additive Manufacturing; Advanced Materials Manufacturing; Biomanufacturing; Life Cycle Engineering; Manufacturing Equipment and Automation ◽

10.1115/msec2021-64688 ◽

2021 ◽

Author(s):

John Henry Navarro-Devia ◽

Dzung Viet Dao ◽

Yun Chen ◽

Huaizhong Li

Keyword(s):

Titanium Alloys ◽

Frequency Domain ◽

Single Channel ◽

End Milling ◽

Cutting Parameters ◽

Frequency Component ◽

Spindle Speed ◽

Triaxial Accelerometer ◽

Vibration Signals ◽

Time Frequency

Abstract Vibrations during milling of hard-to-cut materials can cause low productivity, inferior quality and short tool life. It is one of the common issues in the machining of hard-to-cut materials employed in aerospace applications, such as titanium alloys. This paper presents an analysis of the vibration signals in the 3 axes of movement during titanium end milling, under diverse cutting parameters, manipulating spindle speed and feed rate. Signals were obtained using a triaxial accelerometer and processed in MATLAB. The analysis was conducted in the frequency-domain and the time-frequency domain. The results show that high-frequency vibration could occur in any direction with different amplitudes. Response on each axis depends on spindle speed, feed, and type of milling. A frequency component continually appeared in each axis regardless of cutting conditions and is located near the natural frequencies. Finally, the triaxial accelerations were compared for the milling cases with a new and a worn tool. Results highlight the importance and need for continuous monitoring of vibration in the 3 axes, instead of only using a single-channel signal, providing experimental data which could expand knowledge relating to the milling of titanium alloys.

Download Full-text