Comparison of horizontal winds and turbulent eddy dissipation rates obtained by two different multi-receiver techniques – Spaced Antenna and Postset Beam Steering

Kumar, Shridhar; Rao, T. Narayana; Anandan, V. K.; Sureshbabu, V.N.; Arunamani, T.

doi:10.1016/j.jastp.2015.11.015

Cited by 3 publications

(3 citation statements)

References 34 publications

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“…The authors used an orientation that was constantly rotating four times per cycle throughout the observations and produced an average estimation after each cycle. Subsequently, the improved technique was used to estimate the turbulent eddy dissipation rate and the results were compared with another multi receiver technique, postset beam steering (Kumar et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of EAR Spaced Antenna Performance Using Multiple Receiving Antennas Orientations

2020

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Equatorial Atmosphere Radar (EAR) is a very high frequency (VHF) Doppler radar with an active phased array antenna system operating at 47 MHz. It had originally been equipped with a single receiving channel system since its establishment in 2001 at the equator in Kototabang, West Sumatra, Indonesia (0.20 • S, 100.32 • E). Recent progress has enabled the implementation of a spaced antenna (SA) method on the EAR through the development of a multichannel receiver using Universal Software Radio Peripheral (USRP) and GNU Radio. However, this approach exhibits limited height observation and horizontal wind estimation accuracy. Here, we present comparison and analysis of EAR SA performance with five different orientations, taking into consideration the size of the receiving antennas and their separation distance. Experiments with the chosen configurations were carried out between April and September 2019, and the horizontal wind profiles were estimated using full correlation analysis (FCA) and compared with the EAR standard data. In addition, FCA with the least squares method is carried out for all configurations with the aim of improving the estimation accuracy. Based on the results, the configuration with the largest aperture shows a clear advantage over the other four configurations but with limited improvement in terms of maximum observable height.

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Section: Introductionmentioning

confidence: 99%

Evaluation of EAR Spaced Antenna Performance Using Multiple Receiving Antennas Orientations

2020

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“…In this study, we estimated the echo center by means of Capon's method (Capon 1969). The Capon method is also a type of beamforming but is an optimization processing, which has been applied to the VHF atmospheric radar successfully (Palmer et al 1998;Saito et al 2006;Chen et al 2007;Yu et al 2010;Kumar et al 2016); we will show its feasibility in determining the echo center of sea echoes. The main goal of this study is to validate the VHF radar-observed sea echoes, including periodic oscillations in the time series of echo intensity, Doppler/radial velocity, spectral width, and echo center.…”

Section: Introductionmentioning

confidence: 99%

VHF Radar Observations of Sea Surface in the Northern Taiwan Strait

Chen

Lai

Chien

et al. 2019

Journal of Atmospheric and Oceanic Technology

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A VHF pulsed radar system was set up on the Taoyuan County seashore (24°57′58″N, 121°00′30″E; Taiwan) to observe the sea surface in the northern Taiwan Strait for the first time. The radar used a four-element, vertically polarized Yagi antenna to transmit the 52-MHz radar wave. The receiving linear array consists of four vertical dipole antennas that were located 3 m apart and attached with four independent and identical receivers. With the multichannel echoes, the direction of arrival (DOA) of the radar echoes were determined by using an optimization beamforming approach—the Capon method. Echo intensity was observed to vary principally in semidiurnal oscillation, which matched well the time series of tide gauge measurements and sea level simulations. In addition, the oscillatory characteristics of Doppler/radial velocity of the VHF radar were generally consistent with that of the HF coastal ocean dynamics applications radar (CODAR) nearby. Nevertheless, the contributions of various tidal modes to the parameters of DOA, echo intensity, radial velocity, and spectral width, varied with the range and time period (e.g., neap or spring tides). For example, the semidiurnal tides governed the variation in the echo center only in the range interval between ~15 and ~25 km from the seashore but dominated other parameters throughout the detectable range. Correlations and phase relationships between these parameters were diverse; they varied with time and had dramatic changes at around the distances of 3 and 10 km. Possible causes of these features were discussed, including sea surface wind, nearshore current, sea level height, and bathymetric effect.

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“…Besides multi-receiver capability, AIR is also augmented with several new features, including scalability and modularity of the antenna array, 360° beam agility in azimuthal direction, and independent Transmit/Receive (T/R) Module (TRM) unit for each antenna. The augmentation of multi-receiver capability makes it possible to apply various signal processing techniques that require spatially separated receiving antennas, such as SA (Briggs, 1984;Doviak et al, 1996;Holdsworth, 1995;Holloway et al, 1997), Radar imaging (Palmer et al, 1998(Palmer et al, , 1999, Radar interferometry (Palmer et al, 1995), Post-set beam steering (Kumar et al, 2016;Rottger & Ierkic, 1985) and Post-statistic beam steering (Kudeki & Woodman, 1990) techniques.…”

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confidence: 99%

Multi‐Receiver Augmentation to Advanced Indian MST Radar (AIR)—Implementation of Spaced Antenna Technique

Kumar

Rao

et al. 2021

Radio Science

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Newly acquired multi‐receiver capability of Advanced Indian MST radar has been utilized to implement the spaced antenna (SA) technique for profiling of winds and turbulence. Two experiments were conducted. In Experiment 1, in addition to the traditional Full Correlation Analysis (FCA), SA analysis is also performed on off‐vertical beam measurements (hereafter Oblique Spaced Antenna [OSA]) and the products are evaluated against those retrieved with Doppler Beam Swinging (DBS) and collocated GPS radiosonde. In Experiment 2, the dependence of height coverage on antenna aperture is examined. The synchronization and phase matching of receiving channels are found to be well within the designed values. The consensus averaged zonal and meridional wind velocities obtained by FCA and OSA compare very well with DBS and radiosonde measurements with correlation coefficients >0.85 and root mean square error (RMSE) < 2 ms−1. The mean value of antenna parameter, ah, extracted from correlation of different antenna pairs compare well with the theoretical estimate. The efficacy of ah in quality controlling the SA derived winds has been examined. Imposing ah condition has certainly removed several outliers and reduced the RMSE (relative to reference) considerably, but it also reduced useful data by 50%. The consensus averaging of winds is found to be more effective in removing outliers and reducing the RMSE. The wind variances estimated by DBS (after accounting the non‐turbulent contributions) and SA agree quite well with a correlation coefficient of 0.95. Utilization of a bigger array increased the height coverage from 10‐12 to 20 km.

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Comparison of horizontal winds and turbulent eddy dissipation rates obtained by two different multi-receiver techniques – Spaced Antenna and Postset Beam Steering

Cited by 3 publications

References 34 publications

Evaluation of EAR Spaced Antenna Performance Using Multiple Receiving Antennas Orientations

Evaluation of EAR Spaced Antenna Performance Using Multiple Receiving Antennas Orientations

VHF Radar Observations of Sea Surface in the Northern Taiwan Strait

Multi‐Receiver Augmentation to Advanced Indian MST Radar (AIR)—Implementation of Spaced Antenna Technique

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