A φ-OTDR using Direct Digital Synthesis of Chirps and Sidelobe Suppression with Nonlinear Frequency Modulation

2021 ◽  
Author(s):  
Yonas Muanenda ◽  
Stefano Faralli ◽  
Claudio J. Oton ◽  
Philippe Velha ◽  
Fabrizio Di Pasquale
Keyword(s):  
Frequency Modulation ◽  
Nonlinear Frequency ◽  
Sidelobe Suppression ◽  
Direct Digital Synthesis ◽  
Digital Synthesis

scholarly journals Research of metrological capabilities of digital (DDS- and Trueform-) generators

2021 ◽  
pp. 3-9
Author(s):  
Yurii Pavlenko ◽  
Sergii Kirienko ◽  
Valeriy Ogar ◽  
Olena Vаsileva
Keyword(s):  
Amplitude Modulation ◽  
Frequency Modulation ◽  
Nonlinear Distortion ◽  
Modulation Frequency ◽  
Frequency Deviation ◽  
Frequency Noise ◽  
Direct Digital Synthesis ◽  
Modulation Mode ◽  
Nonlinear Distortions ◽  
Digital Synthesis

Abstract One of the fundamental improvements of the measurement standard of frequency deviation of frequency-modulated oscillations was the replacement of analog frequency-modulated generators used in DETU 09-03-95 with digital ones based on the principle of direct digital synthesis (DDS) and its next version of Trueform technology. These generators have wider ranges of frequency deviation and modulation frequencies than analog ones, but nonlinear distortion laws of the frequency modulation are not standardized. The subject of the article is the development of methods and research of these generators and frequency-modulated signals generated by them for nonlinear distortions, accompanying amplitude modulation, frequency noise. Three methods were used in the study: direct measurement; “combination frequencies” and “frequency shift”. The experiment was performed using several measurement methods, which allowed to estimate very small values of nonlinear distortion. Methods were developed and experimental estimations of concomitant amplitude modulation of DDS-generators (in frequency modulation mode), as well as their frequency noise level, were performed. An experimental evaluation of the capabilities of the analog-digital demodulator of the R&S FSL6 spectrum analyzer with the K7 option was performed, its high linearity was shown, its capabilities with respect to the frequency ranges of carrier oscillations and frequency deviation were evaluated. The research results provide a basis for the method of calibration of DDS-generators and demodulator of spectrum analyzers with the K7 option in those ranges where their parameters are not normalized (at direct current up to 8 MHz and F up to 500 kHz).

An Improved Doppler Shift Simulation Method Based on Third-Order DDS

2014 ◽  
Vol 614 ◽  
pp. 356-362 ◽  
Author(s):  
Rui Li ◽  
Yuan Long Cai ◽  
Xin Bei Bai ◽  
Ming Quan Lu
Keyword(s):  
Doppler Shift ◽  
Dynamic Range ◽  
Doppler Frequency ◽  
Simulation Method ◽  
Global Navigation Satellite Systems ◽  
Direct Digital Synthesis ◽  
Third Order ◽  
Satellite Systems ◽  
Digital Synthesis ◽  
Global Navigation Satellite

A method to simulate the Doppler frequency shift of high dynamic signals of Global Navigation Satellite Systems (GNSS) is provided in this paper. The methodology of the method based on third-order Direct Digital Synthesis (DDS) is introduced and the efficient implementation architecture is proposed. The design criteria of the DDS are investigated according to the precision and dynamic range of the Doppler shift. The simulation results are also demonstrated, which indicate that the method is available for the high precision Doppler shift simulation of GNSS signals.

Simulation of Stepped-Frequency LFM Radar Echo Based on FPGA

2012 ◽  
Vol 198-199 ◽  
pp. 948-953
Author(s):  
Jian Ping Ou ◽  
Sheng Qi Liu ◽  
Wei Niu
Keyword(s):  
Moving Target ◽  
Direct Digital Synthesis ◽  
Implementation Framework ◽  
Radar Echoes ◽  
Radar Echo ◽  
Digital Synthesis ◽  
Physical Simulations ◽  
Stepped Frequency ◽  
Logic Resource

An implementation framework of stepped-frequency LFM (SF-LFM) radar echoes simulator is presented in the paper based on the decomposition and calculation of SF-LFM radar echoes of a moving target. The proposed method can be implemented conveniently with direct digital synthesis (DDS) logic resource. The feasibility of this resolution is verified with computer and semi-physical simulations experiments.

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