Near-thumbtack ambiguity function of random frequency modulated signals

Pralon, Leandro; Beltrao, Gabriel; Pompeo, Bruno; Pralon, Mariana; Fortes, José Mauro P.

doi:10.1109/radar.2017.7944226

Cited by 16 publications

(9 citation statements)

References 5 publications

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“…It is therefore important that the expected AF has good properties. Analysis of the statistical properties of the AF has similarly been performed for noise radar systems, where the transmitted signal is obtained from a stochastic process [42]. Suppose x[m] = e −j2πφ ′ m and φ ′ m is chosen independently and randomly from a uniform distribution φ ′ m ∈ [0, 1).…”

Section: Ambiguity Function With Random Datamentioning

confidence: 99%

Joint Radar and Communications With Multicarrier Chirp-Based Waveform

Berggren

Popović

2022

IEEE Open J. Commun. Soc.

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We consider a multicarrier chirp-based waveform for joint radar and communication (JRC) systems and derive its time discrete periodic ambiguity function (AF). A set of waveform parameters (e.g., chirp rate) can together with the transmit sequence be selected to shape the AF to be thumbtack-like, or to be ridge-like, either along the delay axis or the Doppler axis. We demonstrate how these shapes are applicable for different use cases, e.g., radar target detection or time-and frequency synchronization. The results show that better signal detection performance than OFDM and DFT-s-OFDM can be achieved on channels with large Doppler shift. Furthermore, it is shown how transmit sequences can be selected in order to achieve low peak-to-average-power-ratio (PAPR) of the waveform.

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Section: Ambiguity Function With Random Datamentioning

confidence: 99%

Joint Radar and Communications With Multicarrier Chirp-Based Waveform

Berggren

Popović

2022

IEEE Open J. Commun. Soc.

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“…Assuming

to be stationary, ( 2 ) can be further simplified as

where

is the autocorrelation function of the complex stochastic process

[ 26 ]. Despite being relatively intuitive, the near thumbtack format depicted in ( 3 ) shows that that the expected range and Doppler profiles in Noise Radar systems are independent functions; therefore, no range-Doppler coupling is expected in Noise Radars [ 27 ].…”

Section: Pm/fm Noise Radar and Directional Statisticsmentioning

confidence: 99%

“…Figure 1 respectively illustrates the Doppler profile and range profile cuts (considering different values of Doppler shifts—

and

) of the Ambiguity Function for a single pulse realization of

, considering a transmit signal with a bell shaped autocorrelation function. Note that the main lobe behavior is precisely the one described by ( 23 ), vanishing for

, while the side lobes, even though exhibiting a random behavior, present their mean value according to ( 30 ), invariant with the Doppler shift [ 27 ]. In obtaining the referred images, it was considered

s and

MHz, but the same behavior is expected despite the parameters used.…”

Section: Wrapped Normal Modulating Signalsmentioning

confidence: 99%

On the Analysis of PM/FM Noise Radar Waveforms Considering Modulating Signals with Varied Stochastic Properties

Pralon

Beltrao

Barreto

et al. 2021

Sensors

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Noise Radar technology is the general term used to describe radar systems that employ realizations of a given stochastic process as transmit waveforms. Originally, carriers modulated in amplitude by a Gaussian random signal, derived from a hardware noise source, were taken into consideration, justifying the adopted nomenclature. With the advances made in hardware as well as the rise of the software defined noise radar concept, waveform design emerges as an important research area related to such systems. The possibility of generating signals with varied stochastic properties increased the potential in achieving systems with enhanced performances. The characterization of random phase and frequency modulated waveforms (more suitable for several applications) has then gained considerable notoriety within the radar community as well. Several optimization algorithms have been proposed in order to conveniently shape both the autocorrelation function of the random samples that comprise the transmit signal, as well as their power spectrum density. Nevertheless, little attention has been driven to properly characterize the stochastic properties of those signals through closed form expressions, jeopardizing the effectiveness of the aforementioned algorithms as well as their reproducibility. Within this context, this paper investigates the performance of several random phase and frequency modulated waveforms, varying the stochastic properties of their modulating signals.

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“…Many different approaches have been proposed in the literature to generate waveforms characterized by stochastic processes that better fulfill these radar system requirements [5,[14][15][16][17][18]. Still, they all suffer from low Doppler tolerance [19], an inherent characteristic of traditional noise radars that hinders their use in several applications, including surveillance. Researchers have proposed alternative approaches to bypass such a weakness while preserving the LPI and the LPE properties of random waveforms.…”

Section: Introductionmentioning

confidence: 99%

On a Closer Look of a Doppler Tolerant Noise Radar Waveform in Surveillance Applications

Barbosa,

Pralon,

Ramos

et al. 2024

Sensors

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The prevalence of Low Probability of Interception (LPI) and Low Probability of Exploitation (LPE) radars in contemporary Electronic Warfare (EW) presents an ongoing challenge to defense mechanisms, compelling constant advances in protective strategies. Noise radars are examples of LPI and LPE systems that gained substantial prominence in the past decade despite exhibiting a common drawback of limited Doppler tolerance. The Advanced Pulse Compression Noise (APCN) waveform is a stochastic radar signal proposed to amalgamate the LPI and LPE attributes of a random waveform with the Doppler tolerance feature inherent to a linear frequency modulation. In the present work, we derive closed-form expressions describing the APCN signal’s ambiguity function and spectral containment that allow for a proper analysis of its detection performance and ability to remove range ambiguities as a function of its stochastic parameters. This paper also presents a more detailed address of the LPI/LPE characteristic of APCN signals claimed in previous works. We show that sophisticated Electronic Intelligence (ELINT) systems that employ Time Frequency Analysis (TFA) and image processing methods may intercept APCN and estimate important parameters of APCN waveforms, such as bandwidth, operating frequency, time duration, and pulse repetition interval. We also present a method designed to intercept and exploit the unique characteristics of the APCN waveform. Its performance is evaluated based on the probability of such an ELINT system detecting an APCN radar signal as a function of the Signal-to-Noise Ratio (SNR) in the ELINT system. We evaluated the accuracy and precision of the random variables characterizing the proposed estimators as a function of the SNR. Results indicate a probability of detection close to 1 and show good performance, even for scenarios with a SNR slightly less than −10 dB. The contributions in this work offer enhancements to noise radar capabilities while facilitating improvements in ESM systems.

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Near-thumbtack ambiguity function of random frequency modulated signals

Cited by 16 publications

References 5 publications

Joint Radar and Communications With Multicarrier Chirp-Based Waveform

Joint Radar and Communications With Multicarrier Chirp-Based Waveform

On the Analysis of PM/FM Noise Radar Waveforms Considering Modulating Signals with Varied Stochastic Properties

On a Closer Look of a Doppler Tolerant Noise Radar Waveform in Surveillance Applications

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