A broadband antenna array for sea scatter measurements

Ma, Mingyang; Tveten, L. H.

doi:10.1109/tap.1976.1141340

Cited by 1 publication

(3 citation statements)

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“…Because of the relatively slow angular speed of the aircraft, antenna patterns were traced on a single pass for all beam positions, so that relative gain measurements that were made were meaningful. These were made for several radar frequencies, and the results compared favorably with those predicted by theory [3]. Hence, theoretical values for absolute antenna gain were used in the analysis reported here.…”

Section: Trizna Bogle Moore and Howementioning

confidence: 98%

“…3 changes again, which may be evidence for yet another coupling of wind to waves, or perhaps the onset of a wave-wave interaction which redistributes energy within the spectrum as a function of frequency and angle.…”

Section: I'mentioning

confidence: 98%

“…In the first mode, the radar can be operated from 2 to 25 MHz, with no degradation in sidelobes; in the second mode, the upper limit in operating frequency is of the order of 11.5 MHz at the most extreme viewing angles, where sidelobes are generated which curtail meaningful operation. The antenna has been described in greater detail in another publication, which can be referenced for more information [3].…”

Section: A Description Of Radar Operation and Data Processingmentioning

confidence: 99%

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Observation by HF radar of the Phillips resonance mechanism for generation of wind waves

Trizna¹,

Bogle²,

Moore³

et al. 1980

J. Geophys. Res.

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Measurements are reported of directional ocean wave spectra made over 80° of viewing angle by an HF radar, operating in the surface wave mode in an area 22.5 km north of San Clemente Island, California. Ten azimuths from 280° to 360° true bearing were simultaneously measured for 10 wave frequencies ranging from 0.14 Hz (75 m waves) to 0.35 Hz (13 m waves). A Waverider buoy was used to measure omnidirectional energy in the region, and first‐order radar Bragg lines were used to determine the spreading of wave energy with angle. Data are presented in which a bimodal spectrum was present: an attenuated spectrum with wave components to 0.10 Hz from a storm at sea at 270° bearing; plus a transient local wind spectrum, stronger in amplitude at the higher frequencies, with wave cutoff near 0.14 Hz, and running from 315° bearing. Just after the onset of local winds, the westerly spectrum fitted a cosine squared spread at the lowest measured frequencies. With the development of local wind, which blew at a 12–14 kn (6–7 m s−1) speed for a period of 12 hours, the wave spectrum spread about the wind direction as cosine thirty‐second at the lowest frequencies measured, 0.14 Hz, and cosine sixty‐fourth at the highest frequencies measured, 0.35 Hz. For 0.28 Hz waves the Phillips resonance mechanism for wave generation is proposed to explain the twin peaks in amplitude observed, equally spaced either side of the wind direction. These were dominant for the earliest measurement period and still were major contributions for later measurement periods. This mechanism was found to contribute also at the higher wave frequencies, as predicted by theory. Coherence times are derived from the angular widths of the Phillips resonances based on predictions of Stewart and Manton and are found to agree quite well with theory.

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Section: Trizna Bogle Moore and Howementioning

confidence: 98%

Section: I'mentioning

confidence: 98%

Section: A Description Of Radar Operation and Data Processingmentioning

confidence: 99%

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