Features of application of the sampling theorem when processing narrow-band radio signals with known center frequency of the spectrum
Keywords:processing of radar signals, synchronous detection, analog-to-digital conversion, signal sampling, Doppler shift.
AbstractAn option is presented for sampling narrow-band radio signals with a known center frequency of the spectrum, which can significantly reduce the amount of computational operations when processing such signals without significant loss of information about their parameters. In this case, narrowband is determined by the ratio of the spectrum width of the received radar signal and the operating frequency of the intermediate frequency amplifier, from the output of which the signal is fed to an analog-to-digital converter (ADC). A study of the proposed method of discretization is carried out, in which the repetition rate of the ADC interrogation pulses is determined by the frequency of the reference signal of the master system of a coherent radar and is selected multiple times lower than the operating frequency of the intermediate frequency amplifier. The synchronization of the ADC interrogation pulses is organized in such a way that any two adjacent samples are quadrature connected. This procedure allows you to determine the amplitude and phase of the received signal corresponding to each sample. This creates the conditions for determining the Doppler shift and envelope parameters of the signal. The results of calculating the relative error in determining the amplitude of the signal, which appears as a result of a mismatch in the frequency of the received signal with the frequency of the reference signal, are presented. For real cases, it does not exceed 1% and depends on the radar characteristics (sounding wavelength, multiplicity between the value of the intermediate frequency at which the processing is carried out, and the value of the sampling frequency), as well as on the magnitude of the object radial velocity and the initial phase difference between the output signal of the intermediate frequency amplifier and the reference signal. It is shown that this approach to converting the signal into a digital format is also applicable to signals with phase (0, π) manipulation if the duration of the code elements is significantly longer than the period of the reference signal.
Skolnik M.I. Introduction to RADAR Systems. Seсond Ed. Singapore : McGraw Hill Publications, 1981.
Ziomek C., Corredoura P. Digital I/Q demodulator // Proceedings Particle Accelerator Conference 1-5 May 1995 USA, IEEE 2002. DOI: 10.1109/PAC.1995.505652.
Niranjan R.K., Rajendra Naik B. Approach of Pulse Parameters Measurement Using Digital IQ Method // International Journal of Information and Electronics Engineering. 2014. Vol. 4, No. 1. P. 31-35. DOI: 10.7763/IJIEE.2014.
Taran V.I., Rogozhkin E.V., Grigorenko E.I, Gridin A.N., Golobin V.I., Liokumovich V.I., Chernyaev S.V. Specialized measurement system of the Khar'kov Polytechnic Institute for investigating the ionosphere by the incoherent-scattering method // Radiophysics and Quantum Electronics. 1975. Vol. 18, Iss. 9, P. 1026-1027. DOI: 10.1007/BF01038201.
Рогожкин Е.В., Маенко Ф.А. Цифровой коррелометр для исследований сигналов с известной центральной частотой спектра // Вестник ХПИ. Сер. “Автоматика и приборостроение”. Харьков, 1975. №103 (2). С. 70-74.
Рогожкин Е.В., Белозеров Д.П., Еремин А.Н. Информационные возможности цифровой обработки радиосигналов при известной несущей частоте // Вестник Нац. техн. ун-та “ХПИ”: сб. науч. тр. темат. вып. : Радиофизика и ионосфера. Харьков : НТУ “ХПИ”, 2003. № 7, т. 4. С. 81-88.
Емельянов Л.Я., Лялюк А.И., Рогожкин Е.В. Особенности обработки сигналов некогерентного рассеяния на радаре Института ионосферы // Радиотехника. 2015. Вып. 182. C. 29-33.
Рогожкин Е.В., Подъячий Ю.И., Емельянов Л.Я. Модификация цифрового представления радиолокационных сигналов // Радиотехника. 2019. Вып. 196. С. 69-75.
How to Cite
Authors who publish with this journal agree to the following terms:
1. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
2. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.3. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).