The scattering of high frequency electromagnetic radiation from deterministic targets on the ocean surface
Notice bibliographique
Résumé
An analysis of the electromagnetic scattering from deterministic targets embedded in time-varying random rough surfaces is presented. The approach combines and extends previous works addressing high frequency (HF) electromagnetic scattering from the ocean and stationary surface targets separately. The analysis begins with first- and second-order expressions for the normal component of the scattered electric field from a conducting surface that is small in height and slope and described by a time-varying Fourier series. A vertical pulsed-dipole transmitting source is assumed while the observation point of the scattered field remains general. These expressions are modified to introduce a finite, deterministic target with arbitrary motion via a Fourier transform of the surface target’s profile. The Fourier integrals in the resulting expressions are evaluated through asymptotic methods. The analysis produces two bistatic scattered field expressions involving the surface target. These are attributed to (1) first- and second-order scatters solely from the target and (2) a double scatter involving the target and nearby surrounding ocean. The two components are added to existing expressions for the first- and second-order scattered fields from the ocean surface to model the total scattered field from an ocean patch containing a surface target. It is shown that the HF Doppler cross section of the ocean patch and target may be found as the sum of the cross sections obtained in treating each field component independently. The target-only and target-ocean cross sections are formally evaluated, while the ocean-only components are obtained from existing models. The target-only component is shown to agree with existing monostatic, zero-velocity results when appropriate substitutions are made. The target-ocean ii cross section represents a new expression not seen in previous work, but its general form is seen to agree with existing bistatic ocean cross section models. Both cross section components involving target scatter contain a motion-related Fourier factor similar to one that arises in ocean cross section models for a radar installed on a floating platform. The HF Doppler cross sections are simplified for the case of a surface target moving with constant velocity. It is shown that the target-only cross section contains a Dirac delta function with an argument restricting the response to an impulse at the bistatic Doppler frequency shift predicted for uniform linear motion. The oceantarget component also contains a Dirac delta function with an argument containing the constant-velocity bistatic Doppler shift in addition to terms related to ocean dispersion and the change in target location between radar acquisitions. A system model of an HF radar suitable for predicting the received Doppler power spectral density from an ocean patch containing a surface target is presented. The system model is used to predict the received signal strength for a variety of target, environmental, and radar operating parameters. The results of the computations show, that under certain conditions, a constant velocity target whose first-order cross section is masked by ocean clutter may be detected through a secondary scatter from the ocean surface. The models derived in this work enable the establishment of suitable design specifications and operating parameters when developing new or utilizing existing HF surface wave radar systems for the purposes of monitoring targets on the ocean surface. In addition, the physical interpretation of the scattering process and simple computation provided by the models should prove relevant in developing and testing novel signal processing techniques for both target identification and clutter rejection.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».