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Journal articles on the topic 'Antenna phase centre variation'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Araszkiewicz, Andrzej, Damian Kiliszek, and Anna Podkowa. "Height Variation Depending on the Source of Antenna Phase Centre Corrections: LEIAR25.R3 Case Study." Sensors 19, no. 18 (September 17, 2019): 4010. http://dx.doi.org/10.3390/s19184010.

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In this study, we compared two sets of antenna phase center corrections for groups of the same type of antenna mounted at the continuously operating global navigation satellite system (GNSS) reference stations. The first set involved type mean models provided by the International GNSS Service (release igs08), while the second set involved individual models developed by Geo++. Our goal was to check which set gave better results in the case of height estimation. The paper presents the differences between models and their impact on resulting height. Analyses showed that, in terms of the stability of the determined height, as well as its variability caused by increasing the facade mask, both models gave very similar results. Finally, we present a method for how to estimate the impact of differences in phase center corrections on height changes.

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2

Dawidowicz, Karol, Rafal Kazmierczak, and Krzysztof Swiatek. "SHORT STATIC GPS/GLONASS OBSERVATION PROCESSING IN THE CONTEXT OF ANTENNA PHASE CENTER VARIATION PROBLEM." Boletim de Ciências Geodésicas 21, no. 1 (March 2015): 213–30. http://dx.doi.org/10.1590/s1982-217020150001000014.

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So far, three methods have been developed to determine GNSS antenna phase center variations (PCV). For this reason, and because of some problems in introducing absolute models, there are presently three models of PCV receiver antennas (relative, absolute converted and absolute) and two satellite antennas (standard and absolute). Additionally, when simultaneously processing observations from different positioning systems (e.g. GPS and GLONASS), we can expect a further complication resulting from the different structure of signals and differences in satellite constellations. This paper aims at studying the height differences in short static GPS/GLONASS observation processing when different calibration models are used. The analysis was done using 3 days of GNSS data, collected with three different receivers and antennas, divided by half hour observation sessions. The results show that switching between relative and absolute PCV models may have a visible effect on height determination, particularly in high accuracy applications. The problem is especially important when mixed GPS/GLONASS observations are processed. The update of receiver antenna calibrations model from relative to absolute in our study (using LEIAT504GG, JAV_GRANT-G3T and TPSHIPER_PLUS antennas) induces a jump (depending on the measurement session) in the vertical component within to 1.3 cm (GPS-only solutions) or within 1.9 cm (GPS/GLONASS solutions).

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3

EL-Hattab, Ahmed I. "Influence of GPS antenna phase center variation on precise positioning." NRIAG Journal of Astronomy and Geophysics 2, no. 2 (December 2013): 272–77. http://dx.doi.org/10.1016/j.nrjag.2013.11.002.

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4

Krietemeyer, Andreas, Hans van der Marel, Nick van de Giesen, and Marie-Claire ten Veldhuis. "High Quality Zenith Tropospheric Delay Estimation Using a Low-Cost Dual-Frequency Receiver and Relative Antenna Calibration." Remote Sensing 12, no. 9 (April 28, 2020): 1393. http://dx.doi.org/10.3390/rs12091393.

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The recent release of consumer-grade dual-frequency receivers sparked scientific interest into use of these cost-efficient devices for high precision positioning and tropospheric delay estimations. Previous analyses with low-cost single-frequency receivers showed promising results for the estimation of Zenith Tropospheric Delays (ZTDs). However, their application is limited by the need to account for the ionospheric delay. In this paper we investigate the potential of a low-cost dual-frequency receiver (U-blox ZED-F9P) in combination with a range of different quality antennas. We show that the receiver itself is very well capable of achieving high-quality ZTD estimations. The limiting factor is the quality of the receiving antenna. To improve the applicability of mass-market antennas, a relative antenna calibration is performed, and new absolute Antenna Exchange Format (ANTEX) entries are created using a geodetic antenna as base. The performance of ZTD estimation with the tested antennas is evaluated, with and without antenna Phase Center Variation (PCV) corrections, using Precise Point Positioning (PPP). Without applying PCVs for the low-cost antennas, the Root Mean Square Errors (RMSE) of the estimated ZTDs are between 15 mm and 24 mm. Using the newly generated PCVs, the RMSE is reduced significantly to about 4 mm, a level that is excellent for meteorological applications. The standard U-blox ANN-MB-00 patch antenna, with a circular ground plane, after correcting the phase pattern yields comparable results (0.47 mm bias and 4.02 mm RMSE) to those from geodetic quality antennas, providing an all-round low-cost solution. The relative antenna calibration method presented in this paper opens the way for wide-spread application of low-cost receiver and antennas.

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5

Wang, Chaochao, Gérard Lachapelle, and M. Elizabeth Cannon. "Development of an Integrated Low-Cost GPS/Rate Gyro System for Attitude Determination." Journal of Navigation 57, no. 1 (January 2004): 85–101. http://dx.doi.org/10.1017/s0373463303002583.

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The use of low-cost GPS receivers and antennas for attitude determination can significantly reduce the overall hardware system cost. Compared to the use of high performance GPS receivers, the carrier phase measurements from low-cost equipment are subject to additional carrier phase measurement errors, such as multipath, antenna phase centre variation and noise. These error sources, together with more frequent cycle slip occurrences, severely deteriorate attitude determination availability, reliability and accuracy performance. This paper presents the investigation of a low-cost GPS/gyro integration system for attitude determination. By employing the dead reckoning sensor type, the ambiguity search region can be specifically defined as a small cube to enhance the ambiguity resolution process. A Kalman filter is implemented to fuse the rate gyro data with GPS carrier phase measurements. The quality control system based on innovation sequences is used to identify cycle slip occurrences and incorrect inter-antenna vector solutions. The availability of the integrated system also improves with respect to the GPS standalone system since the attitude parameters can be estimated using the angular rate measurements from rate gyros during GPS outages. The low-cost hardware used to design and test the integrated system consists of CMC Allstar receivers with the OEM AT575-70 antennas and Murata ENV-05D-52 piezoelectric vibrating rate gyroscopes. Tests in the urban area demonstrated that the introduction of rate gyros in a GPS-based attitude determination system not only effectively decreased the noise level in the estimated attitude parameters but coasted the attitude output during GPS outages and also significantly improved the system reliability.

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6

Baghel, Amit Kumar, Shashank Kulkarni, and Sisir Kumar Nayak. "Parabolic profile pyramidal horn antenna with lower phase centre variation and 3 dB beamwidth in S‐band." IET Microwaves, Antennas & Propagation 13, no. 10 (June 5, 2019): 1626–36. http://dx.doi.org/10.1049/iet-map.2018.5824.

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7

Willi, Daniel, Michael Meindl, Hui Xu, and Markus Rothacher. "GNSS antenna phase center variation calibration for attitude determination on short baselines." Navigation 65, no. 4 (December 2018): 643–54. http://dx.doi.org/10.1002/navi.273.

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8

Stępniak, Katarzyna, Paweł Wielgosz, and Radosław Baryła. "Field tests of L1 phase centre variation models of surveying-grade GPS antennas." Studia Geophysica et Geodaetica 59, no. 3 (March 23, 2015): 394–408. http://dx.doi.org/10.1007/s11200-014-0250-6.

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9

Gu, Defeng, Yuwang Lai, Junhong Liu, Bing Ju, and Jia Tu. "Spaceborne GPS receiver antenna phase center offset and variation estimation for the Shiyan 3 satellite." Chinese Journal of Aeronautics 29, no. 5 (October 2016): 1335–44. http://dx.doi.org/10.1016/j.cja.2016.08.016.

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10

Li, Bin, Yong Luo, Xu Tan, Xiao Ning Zhang, and Jian Jun Wu. "Phase Distribution Analysis of Radiation Pattern of Multi-Beam Satellite Antenna Based on Offset Parabolic Reflector." Advanced Materials Research 846-847 (November 2013): 663–66. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.663.

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This paper focuses on GEO multi-beam satellite offset parabolic reflector antenna. In this paper, radiation fields generated by different feeds are derived, and phase radiation pattern is mainly discussed. It can be seen from the numerical results that when the feed is at the focal point of parabolic reflector, the beam has equal phase within beam service area. In addition, for offset feeds, phase changes slowly from beam center to beam boundary, and the variation is about 0.1 radian.

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11

Shrestha, Sujan, Affan A. Baba, Syed Muzahir Abbas, Mohsen Asadnia, and Raheel M. Hashmi. "A Horn Antenna Covered with a 3D-Printed Metasurface for Gain Enhancement." Electronics 10, no. 2 (January 8, 2021): 119. http://dx.doi.org/10.3390/electronics10020119.

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A simple metasurface integrated with horn antenna exhibiting wide bandwidth, covering full Ku-band using 3D printing is presented. It consists of a 3D-printed horn and a 3D-printed phase transformation surface placed at the horn aperture. Considering the non-uniform wavefront of 3D printed horn, the proposed 3D-printed phase transformation surface is configured by unit cells, consisting of a cube in the centre which is supported by perpendicular cylindrical rods from its sides. Placement of proposed surface helps to improve the field over the horn aperture, resulting in lower phase variations. Both simulated and measured results show good radiation characteristics with lower side lobe levels in both E- and H-planes. Additionally, there is an overall increment in directivity with peak measured directivity up to 24.8 dBi and improvement in aperture efficiency of about 35% to 72% in the frequency range from 10–18 GHz. The total weight of the proposed antenna is about 345.37 g, which is significantly light weight. Moreover, it is a low cost and raid manufacturing solution using 3D printing technology.

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Shrestha, Sujan, Affan A. Baba, Syed Muzahir Abbas, Mohsen Asadnia, and Raheel M. Hashmi. "A Horn Antenna Covered with a 3D-Printed Metasurface for Gain Enhancement." Electronics 10, no. 2 (January 8, 2021): 119. http://dx.doi.org/10.3390/electronics10020119.

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A simple metasurface integrated with horn antenna exhibiting wide bandwidth, covering full Ku-band using 3D printing is presented. It consists of a 3D-printed horn and a 3D-printed phase transformation surface placed at the horn aperture. Considering the non-uniform wavefront of 3D printed horn, the proposed 3D-printed phase transformation surface is configured by unit cells, consisting of a cube in the centre which is supported by perpendicular cylindrical rods from its sides. Placement of proposed surface helps to improve the field over the horn aperture, resulting in lower phase variations. Both simulated and measured results show good radiation characteristics with lower side lobe levels in both E- and H-planes. Additionally, there is an overall increment in directivity with peak measured directivity up to 24.8 dBi and improvement in aperture efficiency of about 35% to 72% in the frequency range from 10–18 GHz. The total weight of the proposed antenna is about 345.37 g, which is significantly light weight. Moreover, it is a low cost and raid manufacturing solution using 3D printing technology.

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13

Yan, Xingyuan, Guanwen Huang, Qin Zhang, Le Wang, Zhiwei Qin, and Shichao Xie. "Estimation of the Antenna Phase Center Correction Model for the BeiDou-3 MEO Satellites." Remote Sensing 11, no. 23 (November 30, 2019): 2850. http://dx.doi.org/10.3390/rs11232850.

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Satellite antenna phase center offsets (PCOs) and phase variations (PVs) for BeiDou-3 satellites are estimated based on the tracking data of the Multi-GNSS Experiment (MGEX) and the international GNSS Monitoring and Assessment System (iGMAS) network. However, when estimating the (PCOs) of BeiDou-3 medium Earth orbit (MEO) satellites by pure Extending the CODE Orbit Model (ECOM1), the x-offset estimations of the PCOs have a systematic variation of about 0.4 m with the elevation of the Sun above the orbital plane (β-angle). Thus, a priori box-wing solar radiation pressure (SRP) model of BeiDou-3 MEO was assisted with ECOM1. Then, the satellite type-specific PCOs and common PVs were obtained. The estimations of PCOs and PVs were compared with the MGEX PCOs from the precise orbit and clock offset. When the MGEX PCOs were used, the root mean square (RMS) of 24 h overlap was 6.76, 4.36, 1.46 cm, in along-track, cross-track, and radial directions, respectively; the RMS and standard deviations (STD) of the 24 h clock offset overlap were 0.28 and 0.15 ns; the fitting RMS of the 72 h clock offset of the quadratic polynomial was 0.243 ns. After comparing this with the estimated PCOs and PVs, the RMS of the 24 h orbit overlap was decreased by 6.5 mm (10.54%), 1.8 mm (4.4%), and 1.1 mm (8.03%) in the along-track, cross-track, and radial directions, respectively; the RMS and STD of the 24 h clock offset overlap were decreased by 0.024 ns (8.6%) and 0.020 ns (13.1%), respectively; the fitting RMS of the 72 h clock offset of the quadratic polynomial was reduced by about 0.016 ns (6.5%).

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14

Qiao, Zhaolong, Zhengpeng Wang, and Jungang Miao. "A High Channel Consistency Subarray of Plane-Wave Generators for 5G Base Station OTA Testing." Electronics 8, no. 10 (October 11, 2019): 1148. http://dx.doi.org/10.3390/electronics8101148.

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A high channel consistency subarray of plane-wave generators (PWG) is described for fifth-generation (5G) base station (BS) over-the-air (OTA) testing. Firstly, the variation of the near field radiation characteristics of the subarray based on the feed amplitude and phase errors of the traditional power divider network is analyzed. The recommended amplitude and phase errors between channels are given. After that, a novel subarray which combines four pyramidal horn antennas and a compact 1:4 waveguide power divider is designed. The optimized perfectly symmetrical zigzag waveguide transmission lines are used to realize consistent power allocation among antenna elements. No intermediate pins are employed, which avoids the significant deterioration of channel consistency caused by assembly errors. The size of the subarray is 4.89 λ0 × 4.97 λ0 × 1.23 λ0 (λ0 is the working wavelength corresponding to the subarray center frequency at 3.5 GHz). The VSWR < 1.5 impedance bandwidth covers 3.4 GHz to 3.6 GHz. The amplitude difference between the four elements of the subarray is less than 0.5 dB, and the phase difference is less than 3°. The simulated and measured results agree well in this design.

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15

Mao, X., P. N. A. M. Visser, and J. van den IJssel. "Impact of GPS antenna phase center and code residual variation maps on orbit and baseline determination of GRACE." Advances in Space Research 59, no. 12 (June 2017): 2987–3002. http://dx.doi.org/10.1016/j.asr.2017.03.019.

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16

Ullah, Shahid, Cunjun Ruan, Muhammad Shahzad Sadiq, Tanveer Ul Haq, and Wenlong He. "High Efficient and Ultra Wide Band Monopole Antenna for Microwave Imaging and Communication Applications." Sensors 20, no. 1 (December 23, 2019): 115. http://dx.doi.org/10.3390/s20010115.

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The paper presents a highly efficient, low cost, ultra-wideband, microstrip monopole antenna for microwave imaging and wireless communications applications. A new structure (z-shape, ultra-wideband (UWB) monopole) is designed, which consists of stepped meander lines to achieve super-wide bandwidth and high efficiency. Three steps are used to design the proposed structure for the purpose to achieve high efficiency and wide bandwidth. The antenna bandwidth is enhanced by varying the length of meander line slots, optimization of the feeding line and with the miniaturization of the ground width. The simulated and measured frequency bands are 2.7–22.5 GHz and 2.8–22.7 GHz (156% fractional bandwidth), respectively. The dimensions of the antenna are 38 mm × 35 mm × 1.57 mm, and its corresponding electrical size is 2.41 λg × 2.22 λg × 0.09 λg, where guided wavelength λg is at the center frequency (12.75 GHz). This antenna achieved a high bandwidth ratio (8.33:1). The realized gain is varying from 1.6–6.4 dBi, while that of efficiency is 70% to 93% for the whole band. Radiation patterns are measured at four operating frequencies. It has an acceptable group delay, fidelity factor, and phase variation results that satisfy the limit of ultra-wideband in the form of the time domain.

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17

Liu, Mingming, Yunbin Yuan, Jikun Ou, and Yanju Chai. "Research on Attitude Models and Antenna Phase Center Correction for Jason-3 Satellite Orbit Determination." Sensors 19, no. 10 (May 27, 2019): 2408. http://dx.doi.org/10.3390/s19102408.

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We focused on the researches of two models used for Jason-3 precise orbit determination (POD)—Jason-3 attitude modes and receiver phase center variation (PCV) model. A combined attitude mode for the Jason-3 satellite is designed based on experimental analysis used in some special cases, such as in the absence of quaternions or when inconvenient to use. We researched the linking of satellite attitude with antenna phase center. Specially, to verify the validity of the combined attitude, we analyzed the effects of different attitude modes on receiver phase center offset (PCO) estimation, PCO correction and POD. Meanwhile, the difference analysis of PCO correction based on attitude modes also contains the combined attitude modeling processes. The POD results showed that the orbital accuracies with the combined attitude are slightly more stable than those with attitude event file. By introducing receiver PCVs into POD, the mean residuals root-mean-square (RMS) is reduced by 1.9 mm and orbital 3D-RMS position difference is improved by 5.7 mm. The eight schemes were designed to integratedly verify the effectiveness of different attitude modes and receiver PCVs model. The results conclude that the accuracy using the combined attitude is higher than that of event file, which also prove the feasibility of the combined attitude in integrated POD and it can be as a revision of attitude event file. Using all mentioned attitude modes, the orbital accuracy by introducing PCVs can be improved by the millimeter level. The integrated effects of attitude modes and receiver PCVs on POD are almost consistent with the effects of a single variable. The optimal results of Jason-3 POD indicate that orbital mean radial RMS is close to 1 cm, and the 3D-RMS position difference is within 3 cm.

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Araszkiewicz, Andrzej, and Damian Kiliszek. "Impact of Using GPS L2 Receiver Antenna Corrections for the Galileo E5a Frequency on Position Estimates." Sensors 20, no. 19 (September 27, 2020): 5536. http://dx.doi.org/10.3390/s20195536.

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Knowledge of Global Navigation Satellite System (GNSS) antenna phase center variations plays a key role in precise positioning. Proper modeling is achieved by accessing antenna phase center corrections, which are determined in the calibration process. For most receiver antenna types, the International GNSS Service provides such corrections for two GPS and GLONASS carrier signals. In the case of Galileo, access to phase center corrections is difficult; only antennas calibrated in the anechoic chambers have available corrections for Galileo frequencies. Hence, in many of the studies, GPS-dedicated corrections are used for these Galileo frequencies. Differential analysis was conducted in this study to evaluate the impact of such change. In total, 25 stations belonging to the EUREF Permanent Network and equipped with individual calibrated antennas were the subject of this research. The results for both the absolute and relative positioning methods are clear: using GPS L2 corrections for Galileo E5a frequency causes a bias in the estimated height of almost 8 mm. For the horizontal component, a significant difference can be noticed for only one type of antenna.

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19

Jang, Jaegyu, and Changdon Kee. "Flight Test of Attitude Determination System using Multiple GPS Antennae." Journal of Navigation 59, no. 1 (December 15, 2005): 119–33. http://dx.doi.org/10.1017/s0373463305003498.

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Small Unmanned Aerial Vehicles (UAVs) or inexpensive airplanes, such as a Cessna single engine aircraft, require a navigation system with a cheap, compact and precise sensor. Over the past ten years, GPS receivers have begun to be used as primary or alternative navigation sensors, because their use can significantly reduce the overall system cost. This paper describes a navigation system incorporating a velocity-based attitude estimation system with an attitude determination system using multiple antennae, which was implemented and tested using a UAV. The main objective was to obtain precise attitude information using low cost GPS OEM boards and antennae. Attitude boundaries are derived from the relationship between the body frame and the wind coordinates, which are used to validate the resolved cycle ambiguity in an Euler angle domain. Angular rate based on Doppler measurements was used to exclude the degenerate pseudo-roll angle information during severe uncoordinated flight. Searching for cycle ambiguity at every epoch of the flight showed that the developed system gave reliable cycle integer solutions, although the carrier phase measurement was subject to additional errors, such as multipath, external interference, and phase centre variation. A flight test was performed using a 1/4-scale Piper J3 Cub model, CMC Allstar OEM boards, OEM AT575-70 antennae, and 700 MHz PC104 board.

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20

Werlich, Renata Magda Cavalcante, Claudia Pereira Krueger, and Günter Schmitt. "A INFLUÊNCIA DOS PARÂMETROS DE CALIBRAÇÃO DE ANTENAS GPS NAS ALTITUDES ELIPSOIDAIS NO POSICIONAMENTO RELATIVO ESTÁTICO." Boletim de Ciências Geodésicas 21, no. 3 (September 2015): 532–47. http://dx.doi.org/10.1590/s1982-21702015000300030.

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Resumo:Alta acurácia em posicionamento GPS (Global Positioning System) é obtida através da eliminação parcial ou total dos erros presentes nas observações, particularmente os sistemáticos. Um deles é o erro de centro de fase da antena GPS. Ele é diretamente dependente da antena utilizada, visto que cada uma delas tem suas características próprias de construção e recepção do sinal GPS. Portanto, é de extrema importância o conhecimento individual do centro de fase da antena (Phase Center Offset- Phase Center Variation). Entre outros, existem parâmetros fornecidos pelo NGS (National Geodetic Survey), no entanto, esses valores são médios e não são valores próprios das antenas usadas nos posicionamentos GPS. Os parâmetros individuais das antenas, neste trabalho, foram fornecidos pela BCAL/UFPR (Base de Calibração de Antenas GNSS na UFPR). Realizaram-se posicionamentos GPS em 9 (nove) pontos. Estes foram distribuidos em 3 (três) grupos de linhas de base (9km, 45km e 105km). Para cada comprimento de linha de base os rastreios GPS seguiram simultâneos aplicando o Método de Posicionamento Relativo Estático, com um intervalo de gravação de dados de 15 segundos e máscara de elevação de 15°. Foram encontradas diferenças na comparação das altitudes elipsoidais e no comprimento das linhas de bases, quando não se utilizou parâmetros, na ordem do centímetro. De fato, os valores obtidos da BCAL/UFPR são provenientes da utilização dos próprios equipamentos, desta forma, fiéis às antenas utilizadas, enquanto que os fornecidos pelo NGS são valores médios. Destaca-se que a BCAL/UFPR é a primeira base de calibração de antenas GPS/GLONASS no Brasil e na América Latina

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Hsu, Bandar, and Yaulee Lee. "The Photosystem II Heterogeneity of Chlorophyll b-Deficient Mutants of Rice: a Fluorescence Induction Study." Functional Plant Biology 22, no. 2 (1995): 195. http://dx.doi.org/10.1071/pp9950195.

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It has been shown that the fluorescence induction curve of DCMU-poisoned spinach thylakoids can be resolved into three kinetically different phases, a rapid sigmoidal phase (�) followed by two slower exponential phases (β and γ), by using a mathematical analysis method previously described (Hsu, B. D., Lee, Y. S. and Jang, Y. R. (1989). Biochimica et Biophysica Acta 975, 44-49). There is evidence suggesting that the a-phase originates from the major 'normal' photosystem II (PSII) centres, while the β and γphases arise from the two minor groups of 'abnormal' PSII centres with low quantum efficiencies due to their slow electron donation systems (Hsu, B. D. and Lee, J. Y. (1991). Biochimica et Biophysica Acta 1056, 285-292). The same kinetic analysis was made on several chlorophyll �-deficient mutants of rice. PSIIα was identified by its responses to the variation in excitation light intensity, the addition of ferricyanide and the depletion of Mg2+, whereas the slower PSIIβ and PSIIγ were identified by their reaction to the addition of electron donors like hydroxylamine. It was found that the three types of PSII were present in all the mutants studied, irrespective of the amounts of chlorophyll b and the light-harvesting complexes associated with PSII (LHCII). The results suggest that the PSII heterogeneity cannot be attributed to a difference in the antenna size. The variable content of LHCII in mutants mainly affects a single type of PSII, PSIIα. They also suggest that the presence of sigmoidicity in the a-phase (i.e. cooperation between PSIIα units) does not require LHCII, but the effects brought about by Mg2+-depletion (e.g. lowering of fluorescence yield and slowing down of fluorescence rise) are LHCII-dependent.

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Chen, Jenn-Shyong, Jian-Wu Lai, Hwa Chien, Chien-Ya Wang, Ching-Lun Su, Kun-I. Lin, Meng-Yuan Chen, and Yen-Hsyang Chu. "VHF Radar Observations of Sea Surface in the Northern Taiwan Strait." Journal of Atmospheric and Oceanic Technology 36, no. 2 (February 1, 2019): 297–315. http://dx.doi.org/10.1175/jtech-d-18-0110.1.

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Abstract 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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Bortolas, Elisa, Pedro R. Capelo, Tommaso Zana, Lucio Mayer, Matteo Bonetti, Massimo Dotti, Melvyn B. Davies, and Piero Madau. "Global torques and stochasticity as the drivers of massive black hole pairing in the young Universe." Monthly Notices of the Royal Astronomical Society 498, no. 3 (August 29, 2020): 3601–15. http://dx.doi.org/10.1093/mnras/staa2628.

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ABSTRACT The forthcoming Laser Interferometer Space Antenna (LISA) will probe the population of coalescing massive black hole (MBH) binaries up to the onset of structure formation. Here, we simulate the galactic-scale pairing of ∼106 M⊙ MBHs in a typical, non-clumpy main-sequence galaxy embedded in a cosmological environment at z = 7–6. In order to increase our statistical sample, we adopt a strategy that allows us to follow the evolution of six secondary MBHs concomitantly. We find that the magnitude of the dynamical-friction-induced torques is significantly smaller than that of the large-scale, stochastic gravitational torques arising from the perturbed and morphologically evolving galactic disc, suggesting that the standard dynamical friction treatment is inadequate for realistic galaxies at high redshift. The dynamical evolution of MBHs is very stochastic, and a variation in the initial orbital phase can lead to a drastically different time-scale for the inspiral. Most remarkably, the development of a galactic bar in the host system either significantly accelerates the inspiral by dragging a secondary MBH into the centre, or ultimately hinders the orbital decay by scattering the MBH in the galaxy outskirts. The latter occurs more rarely, suggesting that galactic bars overall promote MBH inspiral and binary coalescence. The orbital decay time can be an order of magnitude shorter than what would be predicted relying on dynamical friction alone. The stochasticity and the important role of global torques have crucial implications for the rates of MBH coalescences in the early Universe: both have to be accounted for when making predictions for the upcoming LISA observatory.

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Rothacher, Markus. "Comparison of Absolute and Relative Antenna Phase Center Variations." GPS Solutions 4, no. 4 (April 2001): 55–60. http://dx.doi.org/10.1007/pl00012867.

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Pradipta, Dhota, Dudy D. Wijaya, Heri Andreas, and Dina A. Sarsito. "The Effect of TLS Radome on GNSS Precise Positioning." E3S Web of Conferences 94 (2019): 03012. http://dx.doi.org/10.1051/e3sconf/20199403012.

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This article presents the results of a test carried out to check the usability of spherical TLS targets as GNSS antenna radomes (herein called TLS radomes). On different days, the survey was conducted using two GNSS antennas, one of them with a TLS radome. Measurements were made using 2 roof pillars on the rooftop as base-rover pillars with little obstruction. The measurements were carried out for approximately 1 hour in every scenario. The software used for data processing is MATLAB-based software and the raw data were processed using the double difference (DD) strategy to obtain optimal results. The results of the data processing indicated that the TLS radome has no significant influence on availability and accuracy of estimated position. The signals are slightly attenuated by the radome (1-2 dBHz) and the noise level is slightly increased but both effects are negligible for practical purposes. However, we found that the antenna should be calibrated with the TLS radome to clarify apparent minor phase center eccentricities (1-2 mm) and to reduce systematic effects with long periods (few minutes) and amplitudes up to about 5 mm which are likely due to phase center variations.

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Li, Lixun, Baiyu Li, Huaming Chen, and Feixue Wang. "Phase Errors Simulation Analysis for GNSS Antenna in Multipath Environment." International Journal of Antennas and Propagation 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/962627.

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High-precision GNSS application requires the exact phase center calibration of antenna. Various methods are published to determine the locations of the phase center. In the outfield, when the phase errors that arose by multipath exceed the phase center variations (PCV) tolerance, the calibration values may be not useful. The objective of this paper is thus to evaluate the phase errors that arose by multipath signals. An improved model of antenna receiving signal is presented. The model consists of three main components: (1) an antenna model created by combination of right hand circular polarization (RHCP) and left hand circular polarization (LHCP), (2) a multipath signals model including amplitude, phase, and polarization, and (3) a ground reflection model applying to circular polarization signals. Based on the model, two kinds of novel up-to-down(U/D)ratios are presented. The performance of the model is assessed against the impact of up-to-down ratio of antenna on phase errors.

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Morescki Junior, Luiz Fernando Macedo, and Luiz Danilo Damasceno Ferreira. "Determinação dos coeficientes dos harmônicos esféricos para o cálculo dos parâmetros pcv e pco utilizando dados de programas comerciais de calibração." Boletim de Ciências Geodésicas 20, no. 2 (June 2014): 444–66. http://dx.doi.org/10.1590/s1982-21702014000200026.

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Erros provenientes do centro de fase da antena, conhecidos como PCV - Phase Center Variations - são considerados agentes limitadores da acurácia do posicionamento relativo GNSS e do Posicionamento por Ponto Preciso (PPP). As PCVs dependem da direção do sinal do satélite e podem ser modeladas por parâmetros determinados por calibração de antenas em que são utilizados programas específicos, como por exemplo Wasoft/Kalib. Alguns autores afirmam que os programas aplicam funções harmônicas esféricas para a modelagem dos parâmetros PCV, mas não informam quais coeficientes são adotados para que a modelagem seja alcançada. Nesta pesquisa, são utilizados os parâmetros PCV de calibração determinados pelo programa comercial WaSoft/Kalib para a antena LEIAX 1202GG. O objetivo principal é calcular os coeficientes a nm e b nm da expansão em funções harmônicas esféricas. Os coeficientes são utilizados para determinar novos parâmetros PCV e PCO que são comparados aos parâmetros obtidos pelo programa comercial Wasoft/Kalib. Os novos parâmetros e os parâmetros calibrados são utilizados para determinar as coordenadas geodésicas de dois pontos com o objetivo de serem comparadas. Foram realizados testes para duas linhas de base diferentes e os resultados confirmam diferenças submilimétricas para as PCVs e milimétricas para a componente vertical do vetor PCO.

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Li, Jilu, Jose A. Vélez González, Carl Leuschen, Ayyangar Harish, Prasad Gogineni, Maurine Montagnat, Ilka Weikusat, Fernando Rodriguez-Morales, and John Paden. "Multi-channel and multi-polarization radar measurements around the NEEM site." Cryosphere 12, no. 8 (August 16, 2018): 2689–705. http://dx.doi.org/10.5194/tc-12-2689-2018.

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Abstract. Ice properties inferred from multi-polarization measurements, such as birefringence and crystal orientation fabric (COF), can provide insight into ice strain, viscosity, and ice flow. In 2008, the Center for Remote Sensing of Ice Sheets (CReSIS) used a ground-based VHF (very high frequency) radar to take multi-channel and multi-polarization measurements around the NEEM (North Greenland Eemian Ice Drilling) site. The system operated with 30 MHz bandwidth at a center frequency of 150 MHz. This paper describes the radar system, antenna configurations, data collection, and processing and analysis of this data set. Within the framework derived from uniaxial ice crystal model, we found that ice birefringence dominates the power variation patterns of co-polarization and cross-polarization measurements in the area of 100 km2 around the ice core site. The phase shift between ordinary and extraordinary waves increases nonlinearly with depth. The ice optic axis lies in planes that are close to the vertical plane and perpendicular or parallel to the ice divide depending on depth. The ice optic axis has an average tilt angle of about 11.6° vertically, and its plane may rotate either clockwise or counterclockwise by about 10° across the 100 km2 area, and at a specific location the plane may rotate slightly counterclockwise as depth increases. Comparisons between the radar observations, simulations, and ice core fabric data are in very good agreement. We calculated the effective colatitude at different depths by using azimuth and colatitude measurements of the c axis of ice crystals. We obtained an average effective c axis tilt angle of 9.6° from the vertical axis, very comparable to the average optic axis tilt angle estimated from radar polarization measurements. The comparisons give us confidence in applying this polarimetric radio echo sounding technique to infer profiles of ice fabric in locations where there are no ice core measurements.

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29

Schmid, R., and M. Rothacher. "Estimation of elevation-dependent satellite antenna phase center variations of GPS satellites." Journal of Geodesy 77, no. 7-8 (October 1, 2003): 440–46. http://dx.doi.org/10.1007/s00190-003-0339-0.

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30

WÜBBENA, GERHARD, MARTIN SCHMITZ, FALKO MENGE, GÜNTER SEEBER, and CHRISTOF VÖLKSEN. "A New Approach for Field Calibration of Absolute GPS Antenna Phase Center Variations." Navigation 44, no. 2 (June 1997): 247–55. http://dx.doi.org/10.1002/j.2161-4296.1997.tb02346.x.

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31

W�bbena, Gerhard, Gerald Boettcher, and Martin Schmitz. "Tests of phase center variations of various GPS antennas, and some results." GPS Solutions 6, no. 1-2 (November 1, 2002): 18–27. http://dx.doi.org/10.1007/s10291-002-0008-4.

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32

Kačmařík, Michal, Jan Douša, Florian Zus, Pavel Václavovic, Kyriakos Balidakis, Galina Dick, and Jens Wickert. "Sensitivity of GNSS tropospheric gradients to processing options." Annales Geophysicae 37, no. 3 (June 18, 2019): 429–46. http://dx.doi.org/10.5194/angeo-37-429-2019.

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Abstract. An analysis of processing settings impacts on estimated tropospheric gradients is presented. The study is based on the benchmark data set collected within the COST GNSS4SWEC action with observations from 430 Global Navigation Satellite Systems (GNSS) reference stations in central Europe for May and June 2013. Tropospheric gradients were estimated in eight different variants of GNSS data processing using precise point positioning (PPP) with the G-Nut/Tefnut software. The impacts of the gradient mapping function, elevation cut-off angle, GNSS constellation, observation elevation-dependent weighting and real-time versus post-processing mode were assessed by comparing the variants by each to other and by evaluating them with respect to tropospheric gradients derived from two numerical weather models (NWMs). Tropospheric gradients estimated in post-processing GNSS solutions using final products were in good agreement with NWM outputs. The quality of high-resolution gradients estimated in (near-)real-time PPP analysis still remains a challenging task due to the quality of the real-time orbit and clock corrections. Comparisons of GNSS and NWM gradients suggest the 3∘ elevation angle cut-off and GPS+GLONASS constellation for obtaining optimal gradient estimates provided precise models for antenna-phase centre offsets and variations, and tropospheric mapping functions are applied for low-elevation observations. Finally, systematic errors can affect the gradient components solely due to the use of different gradient mapping functions, and still depending on observation elevation-dependent weighting. A latitudinal tilting of the troposphere in a global scale causes a systematic difference of up to 0.3 mm in the north-gradient component, while large local gradients, usually pointing in a direction of increasing humidity, can cause differences of up to 1.0 mm (or even more in extreme cases) in any component depending on the actual direction of the gradient. Although the Bar-Sever gradient mapping function provided slightly better results in some aspects, it is not possible to give any strong recommendation on the gradient mapping function selection.

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33

Tranquilla, J. M., and S. R. Best. "Antenna phase centre movement in UHF radio positioning systems." Canadian Electrical Engineering Journal 12, no. 1 (January 1987): 11–18. http://dx.doi.org/10.1109/ceej.1987.6593619.

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34

Damini, A., B. Balaji, L. Shafai, and G. Haslam. "Novel multiple phase centre reflector antenna for GMTI radar." IEE Proceedings - Microwaves, Antennas and Propagation 151, no. 3 (2004): 199. http://dx.doi.org/10.1049/ip-map:20040339.

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35

Bock, H., A. Jäggi, U. Meyer, R. Dach, and G. Beutler. "Impact of GPS antenna phase center variations on precise orbits of the GOCE satellite." Advances in Space Research 47, no. 11 (June 2011): 1885–93. http://dx.doi.org/10.1016/j.asr.2011.01.017.

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36

Zhalilo, A. A., A. A. Zhelanov, D. A. Shelkovenkov, and V. M. Shokalo. "The accuracy estimation of GPS/GNSS antennas calibration of phase centre and its variations." Kosmìčna nauka ì tehnologìâ 14, no. 4 (July 30, 2008): 39–52. http://dx.doi.org/10.15407/knit2008.04.039.

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37

Cao, Kejin, Lei Wang, Bao Li, and Hengchao Ma. "A Real-Time Phase Center Variation Compensation Algorithm for the Anti-Jamming GNSS Antennas." IEEE Access 8 (2020): 128705–15. http://dx.doi.org/10.1109/access.2020.3006627.

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38

Dawidowicz, Karol. "Antenna Phase Center Variations Corrections in Processing of Gps Observations with Use of Commercial Software." Technical Sciences 13, no. -1 (November 1, 2010): 120–32. http://dx.doi.org/10.2478/v10022-010-0012-9.

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39

Qu, Ziyang, Jing Guo, and Qile Zhao. "Phase Center Corrections for BDS IGSO and MEO Satellites in IGb14 and IGSR3 Frame." Remote Sensing 13, no. 4 (February 18, 2021): 745. http://dx.doi.org/10.3390/rs13040745.

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As pre-launch antenna calibrations are not available for GPS and GLONASS satellites, the high correlation between the terrestrial scale and phase center offset (PCO) prevents a reliable estimation of the terrestrial scale with GNSS (Global Navigation Satellite System) technology. Fortunately, the ground calibrated PCO values for Galileo, BeiDou navigation satellite system (BDS), and QZSS have been released, making a reliable estimation of the terrestrial scale with GNSS possible. In the third reprocess (repro3) of International GNSS Service (IGS), the terrestrial scale derived with Galileo, has been used. To evaluate the consistency of the terrestrial scale derived from the BDS-released PCOs as well as Galileo-released ones, and to incorporate BDS into IGS repro3 as well as operational legacy analysis, the phase center variations (PCV) and PCO for BDS medium earth orbit (MEO) and inclined geostationary orbit (IGSO) satellites are estimated to be consistent with GPS/GLONASS antenna offsets in two frames, i.e., IGb14 and IGS R3, considering robot calibrations of the ground receiver antenna models for BDS released by Geo++. We observe that the average offset of Z-PCOs achieves +98.8 mm between BDS official released and the estimated PCOs in IGb14 frame for BDS-3 MEO satellites, whereas the average offset for Z-PCO is about +174.1 mm (about −1.27 ppb at the height of BDS MEO satellites) between the solutions in IGSR3 and IGb14 frame. The phase center solutions are evaluated with orbit boundary disclosures (OBD) as well as the global station coordinates. The orbit consistency benefits from the PCO/PCV estimates, particularly for BDS-2 MEO satellites, of which the 3D RMS (root mean square) OBD is reduced by 50%, whereas 3D OBD achieves about 90.0 mm for BDS-3 MEO satellites. Moreover, the scale bias between BDS-derived station coordinates and IGS legacy solutions in IGb14 frame is reduced from +0.446 ± 0.153 ppb to +0.012 ± 0.112 ppb using PCO/PCV estimates in IGb14, instead of the BDS official released values. Additionally, the residuals of the BDS-derived station heights (after the Helmert transformation) are slightly reduced from 9.65 to 8.62 mm. On the other hand, about +0.226 ± 0.175 ppb is observed between BDS-only coordinate solutions derived from PCO/PCV estimates in IGSR3 frame and the IGS repro3 initial combination. These results demonstrate that the scale inconsistency derived from BDS and Galileo released PCOs is about +1.854 ± 0.191 ppb, and a good consistency of PCO/PCC estimates for BDS in IGb14 and IGSR3 frame with other systems of GPS/ GLONASS antenna offsets is achieved.

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40

Jäger, Marc, Rolf Scheiber, and Andreas Reigber. "Robust, Model-Based External Calibration of Multi-Channel Airborne SAR Sensors Using Range Compressed Raw Data." Remote Sensing 11, no. 22 (November 15, 2019): 2674. http://dx.doi.org/10.3390/rs11222674.

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The paper describes a method for the accurate calibration of multi-channel SAR instruments, such as those required to support SAR polarimetry, single-pass interferometry and digital beam-forming (DBF), on the basis of dedicated SAR acquisitions containing reference targets with known properties. Unlike conventional approaches, the method is based entirely on the analysis of range-compressed raw data. It leverages the pulse-by-pulse analysis of amplitude, phase and delay variations observed within the range histories of reference targets to fully characterize and correct propagation direction dependent calibration issues such as those related to antenna pointing or antenna phase center positions. The fact that the approach does not require SAR image focusing in azimuth is especially relevant in the context of DBF, where individual channels need to be calibrated but are, by themselves, under-sampled. The calibration techniques presented are illustrated and validated using multi-channel polarimetric and single-pass interferometric SAR data acquired by DLR’s airborne F-SAR and DBFSAR instruments.

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41

Jarlemark, Per, Ragne Emardson, Jan Johansson, and Gunnar Elgered. "Ground-Based GPS for Validation of Climate Models: The Impact of Satellite Antenna Phase Center Variations." IEEE Transactions on Geoscience and Remote Sensing 48, no. 10 (October 2010): 3847–54. http://dx.doi.org/10.1109/tgrs.2010.2049114.

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42

Ortiz de Galisteo, J. P., C. Toledano, V. Cachorro, and B. Torres. "Improvement in PWV estimation from GPS due to the absolute calibration of antenna phase center variations." GPS Solutions 14, no. 4 (March 13, 2010): 389–95. http://dx.doi.org/10.1007/s10291-010-0163-y.

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43

Arezoomand, Afsaneh Saee, Mohammad Naser‐ Moghadasi, Iraj Arghand, Payam Jahangiri, and Ferdows B. Zarrabi. "Photonic band gap implementation for phase centre controlling in Vivaldi antenna." IET Microwaves, Antennas & Propagation 11, no. 13 (September 12, 2017): 1880–86. http://dx.doi.org/10.1049/iet-map.2017.0010.

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44

Beeckman, P. A. "Analysis of phase errors in antenna-measurements applications to phase-pattern corrections and phase-centre determination." IEE Proceedings H Microwaves, Antennas and Propagation 132, no. 6 (1985): 391. http://dx.doi.org/10.1049/ip-h-2.1985.0069.

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45

Lawrence, Daniel E. "Antenna Insertion Phase Variation With Polarization and Methods for Compensation." IEEE Transactions on Antennas and Propagation 62, no. 11 (November 2014): 5715–22. http://dx.doi.org/10.1109/tap.2014.2355853.

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46

Takacs, Alexandru, Hervé Aubert, Daniel Belot, and Hubert Diez. "Miniaturisation of quadrifilar helical antenna: impact on efficiency and phase centre position." IET Microwaves, Antennas & Propagation 7, no. 3 (February 2013): 202–7. http://dx.doi.org/10.1049/iet-map.2012.0416.

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47

Milijić, Marija R., Aleksandar D. Nešić, Bratislav D. Milovanović, and Dušan A. Nešić. "Printed Antenna Array with Flat-Top Radiation Pattern." Frequenz 72, no. 5-6 (April 25, 2018): 173–80. http://dx.doi.org/10.1515/freq-2016-0249.

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AbstractA printed antenna array consisting of 10 wideband symmetrical pentagonal dipoles is presented. The feed network of impedance transformers is employed to provide appropriate amplitude and phase distribution necessary to obtain flat top beam pattern. The measured results demonstrate excellent radiation characteristics including 38° flat gain region with maximum ripple of 3.5 dB at the centre frequency. Furthermore, the proposed antenna that is placed in corner reflector with angle of 60° has good gain (17 dBi) and side lobe suppression (18.9 dB). Although it is designed at the centre frequencyfc=12 GHz, it was shown to be capable of shaping a good flat top radiation pattern within a fractional bandwidth at least 6 % of centre frequency. Also, proposed antenna features cheap, simple and easy fabrication that makes it suitable for mass production.

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48

Inam, M., and M. Y. Ismail. "Analytical Model and Practicle Validation of Phase Variation of Reflect Array Antenna." Procedia Engineering 53 (2013): 225–32. http://dx.doi.org/10.1016/j.proeng.2013.02.030.

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49

Liu, Zejun, Lan Du, Yongxing Zhu, Zhihan Qian, Jinqing Wang, and Shiguang Liang. "Investigation on GEO satellite orbit determination based on CEI measurements of short baselines." Journal of Navigation 72, no. 06 (May 2, 2019): 1585–601. http://dx.doi.org/10.1017/s0373463319000249.

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Connected-Element Interferometry (CEI) is a technique for measuring the phase delay of difference of Time Of Arrival (TOA) of a downlink radio signal to two antennae on a short baseline. This technique can use an atomic clock for time-frequency transmission and achieve intermediate accuracy angular tracking. Owing to the relatively short length of the baseline, the passive reception mode, and near real-time operation, CEI can be used to continuously monitor the orbit variations of both cooperative and non-cooperative satellites. In this paper, a small-scale CEI system of two orthogonal baselines (75 m × 35 m) is investigated to track a Geostationary Earth Orbit (GEO) Television (TV) satellite at 110·5°E. The phases are extracted from correlation results. The results show that the Root Mean Square (RMS) of the phase fitting residuals, if not calibrated, is within 2° at night and up to 10° in the daytime. After applying the calibration signal, the RMS of the phase fitting residuals in the daytime decreases to the same level at night. Comparing the phase delay with the a priori phase delay using Two-Line-Element (TLE) data, the integer ambiguity is successfully resolved. Finally, a batch algorithm is used to estimate the orbit of the GEO satellite, and the orbit determination accuracy is evaluated using the precise orbits provided by the China National Time Service Centre (NTSC). The results show that the accuracies in the radial direction and the cross-track direction are less than 1 km, and the Three-Dimensional (3D) position accuracy reaches the 2 km order of magnitude.

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50

Barès, C., C. Brousseau, L. Le Coq, and A. Bourdillon. "Effect of antenna phase centre displacement on FM-CW measurements: application to radar system." Electronics Letters 39, no. 11 (2003): 867. http://dx.doi.org/10.1049/el:20030556.

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