{
  "abstract": "High-frequency (HF) skywave radars require high gain at take-off angles of 3 degrees-30 degrees, where vertically polarized monopoles and Yagi-Uda arrays over lossy land suffer from pseudo-Brewster cancellation. This paper shows that curving the elements of HF monopoles and Yagi-Uda arrays converts radiation from this soil-limited transverse-magnetic route into a transverse-electric route that is nearly insensitive to soil conditions. Closed-form half-space bounds quantify both routes and yield design rules; a separability result extends the soil insensitivity to arrays. A hybrid design method combines Bayesian optimization on analytical and method-of-moments models with full-wave simulations of a screened site on moist soil; current extraction differs by at most 5.1% RMS, and Fresnel post-processing agrees with independent perfect-ground results within 0.16 dB in pointwise gain for four arrays. At 15 MHz, a self-matched 2-element curved Yagi-Uda array and a Bayesian-optimized 3-element array achieve realized forward-sector gains of 6.8 and 8.3 dBi over moist soil, 6.4 and 6.3 dB above straight quarter-wave Yagi-Uda arrays optimized by the same procedure, with 92%-95% efficiency. Their gain changes by about 1 dB from a perfect ground to very dry soil, whereas that of the straight arrays falls by 9 dB. Bayesian optimization, confirmed by full-wave simulation, identified a design 0.2 dB above the sweep optimum and a gain-bandwidth Pareto front that offers up to twice the matched bandwidth. The results also show that the native far field of full-wave solvers can overestimate the low-angle gain of vertical arrays over soil by more than 4 dB.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.24368",
  "author_total": 3,
  "authors": [
    {
      "name": "Masoud Salmani Arani"
    },
    {
      "name": "Reza Shahidi"
    },
    {
      "name": "Lihong Zhang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3cm46xjddagw1.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.24368",
  "fulltext_url": null,
  "id": "3cm46xjddagw1",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.24368",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "eess.SP"
    ],
    [
      "arxiv",
      "physics.app-ph"
    ],
    [
      "openalex",
      "2202|Antenna Design and Analysis"
    ]
  ],
  "openalex": "W7223060996",
  "pdf_url": "https://arxiv.org/pdf/2610.24368",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-17",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3cm46xjddagw1.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:52Z",
      "native_id": "2610.24368",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.24368"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.app-ph",
      "subfield": "applied-instrumentation"
    }
  ],
  "title": "Curved HF Monopole Antennas for Improved Low-Angle Skywave Gain Over Lossy Ground",
  "title_text": "Curved HF Monopole Antennas for Improved Low-Angle Skywave Gain Over Lossy Ground",
  "type": "preprint",
  "updated_at": "2026-11-04T15:20:50Z",
  "url": "https://research.draconitic.com/paper/3cm46xjddagw1",
  "venue": "arXiv",
  "versions": []
}