GPS Antenna Research Articles

Shipborne high-accuracy heading determination method using INS- and GPS-based heading determination system

The heading accuracy of an existing shipborne inertial navigation system (INS) is affected by the oscillatory heading error caused by the misalignment angles between the gyro case and gyro axes. The accuracy of the heading determination system (HDS), which consists of two quadruple GPS antenna arrays, an INS, a total station surveying apparatus (TSSA), and two vessels, is affected by jump errors because of the degradation of tracking performance of the TSSA servo system in high dynamic conditions. Given that only pitch and roll of the INS are utilized in the HDS, we propose a high-accuracy heading determination system that combines the heading rate of the INS and linear fit of the heading difference between INS and HDS, to compensate for jump errors of HDS and oscillatory heading error of the INS. With the designed equipment, both jump errors and the oscillatory heading error can be suppressed effectively. The standard deviations of the heading errors are reduced from ±6 to ±2 and from ±8 to ±5 arcsec in mooring and sea tests, respectively, and a high accuracy of shipborne heading determination can be achieved since the oscillatory heading error is reduced to the 1 arcsec level.

A comparative study of gravity and crustal deformation data through superconducting gravimeter and GPS observations in the North-West Himalayan region

Simultaneous observations of gravity measurements and vertical crustal deformation are carried out at the Multi-Parametric Geophysical Observatory (MPGO), Ghuttu (Location 30.53°N, 78.74°E) located in Northwestern part of Himalaya in India. The temporal variation of gravity measurements are monitored by a superconducting gravimeter while the crustal deformations are observed using a dual frequency GPS antenna and receiver system. The simultaneous data collected by both instruments during a period of ~3 years from 2007 to 2010 is evaluated. Both data sets show apparent seasonal/annual changes with a clear phase difference of few months causing negative correlation between the two time series. Loading effects on the Earth's uppermost crust due to the hydrological cycle, as measured from local water table record, are advocated as the explanation of the observed seasonal variation.

GPS SNR prediction in urban environment

The signal quality along with satellite availability & geometric dilution of precision plays a major role in GPS positional accuracy. In this study an attempt is made to develop a SNR prediction model for the urban environment. The height attribute value for 3D shapefile representing different urban environments is acquired from Cartosat-1 DEM and Total Station (which gave better accuracy in prediction). The best fit regression model correlating GPS signal SNR and satellite elevation angle in open environment for a GPS antenna was derived. The derived regression model between satellite elevation angle and signal SNR along with reflection and diffraction coefficients of surrounding urban environment was used to predict the GPS signal SNR at a given time.

Vegetation Sensing Using GPS Interferometric Reflectometry: Experimental Results With a Horizontally Polarized Antenna

Measurement of vegetation state is required both for modeling and for satellite data validation. GPS Interferometric Reflectometry (GPS-IR) is a passive microwave remote sensing technique that has been applied to several applications, such as sensing soil moisture, snow depth, ocean roughness and wind speed, and vegetation growth. Previous studies proposed that geodetic GPS data could be used to measure vegetation biophysical parameters, for example, vegetation height and vegetation water content (VWC). However, the measurement range and accuracy are limited because the geodetic GPS antenna is designed to suppress reflections. In this paper, the antenna design for vegetation sensing via GPS-IR is discussed. Then, a customized dipole antenna is developed specifically for vegetation sensing. A field experiment is conducted at Boulder, CO, USA to evaluate the performance of the proposed antenna. The GPS metric, which is the normalized signal-to-noise ratio (SNR) amplitude ${A_{{\rm{norm}}}}$ , shows a linear relationship with in situ measurements of VWC over a range of 0—6 kg/m2, which is much greater than the range from the geodetic data (0—1.0 kg/m 2). The sensitivity of ${A_{{\rm{norm}}}}$ to VWC change is −0.11 (W/W)/(kg/m2), and the average measurement error of VWC is ∼12.4%. Thus, the horizontally polarized antenna is suitable for vegetation monitoring in most environments, including agricultural settings. The effects of soil moisture on GPS SNR amplitude are also documented, but these are minor compared to the decrease in amplitude resulting from vegetation growth.

A compact circularly‐polarized GPS antenna using LTCC technology

ABSTRACTA circularly‐polarized GPS antenna for L1 (1575 MHz) is designed and fabricated using low temperature cofired ceramic (LTCC) technology. A parallel patch and high dielectric constant composite ceramic with LTCC fabrication method are employed to design a compact structure. The electrical connected parallel patch interval and size are the main parameters for achieving resonance frequency at L1‐band to support modern GPS coding schemes. The proposed electrically connected upper and lower patches are connected together with vertical via pins and therefore did not have any connection with the ground plane. By embedding a truncated corner patch and rectangular slots to this design, the right‐hand circularly‐polarized (RHCP) field property is achieved. By using these features, a compact simple CP‐GPS antenna with 2.32 dBic gain at 1575 MHz is designed and fabricated. The proposed antenna has a total compact size of 15 × 15× 4 mm3and operates over the frequency band from 1570 to 1585 MHz for VSWR < 2. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2926–2930, 2016

Microwave front-end subsystems design for ITS/GPS applications

This paper reports the design, simulation and characterization of adaptable band pass filter, planar microstrip antenna and filtenna for GPS and ITS (intelligent transportation systems) applications. The designed microstrip slotted antenna has a 300MHz of measured bandwidth and 5.7dBi of measured gain, which is sufficient to cover the ITS band (5.85–5.925GHz). On the other hand, the developed filtenna operates in dedicated ITS band at 5.9GHz and have 1.5dBi of measured antenna gain. The reduction in filtenna gain is due to the additional insertion loss introduced by the hairpin bandpass filter incorporated in the feed of the proposed filtenna. Two adaptable bandpass filters have also been designed for GPS applications. First tunable filter operates at 1575MHz (GPS L1 frequency) while rejects 1227MHz frequency (GPS L2 frequency band). The (measured) return loss of the filter is better than 20dB from 1.5GHz to 1.6GHz; while insertion loss at 1575MHz is ∼5.5dB. Second tunable filter has been designed to cover both 1575MHz (L1 frequency band) as well as 1227MHz frequency ranges (L2 frequency band). The return loss (measured) of this filter is better than 10dB from 1.15GHz to 2.15GHz, and insertion loss is ∼5.5dB. The developed sub-systems can be used to build a low cost RF transceiver system for GPS and ITS applications.

Relative positioning calibration method of phase center offsets of GPS signal antennas

Phase center offset (PCO) of GPS antenna has a considerable influence on the precision and accuracy of the resulting coordinates. As joint observation mode of various GPS receivers and antennas becomes increasingly universal, efficient determination of PCO values of multi-type dual-frequency GPS receiver antennas at the same time needs to be addressed urgently. According to the property of antenna PCO, a relative positioning calibration method, which is based on GPS relative positioning survey theory, is proposed. This method only needs two steps, each being a simultaneous observation of one consecutive sidereal day for the reference antenna and the calibrated antenna. Experimental results for several widely used GPS antennas show that this method greatly improves the calibration efficiency and can estimate horizontal PCOs for both frequencies. The proposed method can be fully applied to synchronously assess PCOs of multi-type dual-frequency GPS antennas in high precision position.

HIGH RESOLUTION AIRBORNE LASER SCANNING AND HYPERSPECTRAL IMAGING WITH A SMALL UAV PLATFORM

The capabilities of unmanned airborne systems (UAS) have become diverse with the recent development of lightweight remote sensing instruments. In this paper, we demonstrate our custom integration of the state-of-the-art technologies within an unmanned aerial platform capable of high-resolution and high-accuracy laser scanning, hyperspectral imaging, and photographic imaging. The technological solution comprises the latest development of a completely autonomous, unmanned helicopter by Aeroscout, the Scout B1-100 UAV helicopter. The helicopter is powered by a gasoline two-stroke engine and it allows for integrating 18 kg of a customized payload unit. The whole system is modular providing flexibility of payload options, which comprises the main advantage of the UAS. The UAS integrates two kinds of payloads which can be altered. Both payloads integrate a GPS/IMU with a dual GPS antenna configuration provided by OXTS for accurate navigation and position measurements during the data acquisition. The first payload comprises a VUX-1 laser scanner by RIEGL and a Sony A6000 E-Mount photo camera. The second payload for hyperspectral scanning integrates a push-broom imager AISA KESTREL 10 by SPECIM. The UAS was designed for research of various aspects of landscape dynamics (landslides, erosion, flooding, or phenology) in high spectral and spatial resolution.

HIGH RESOLUTION AIRBORNE LASER SCANNING AND HYPERSPECTRAL IMAGING WITH A SMALL UAV PLATFORM

Abstract. The capabilities of unmanned airborne systems (UAS) have become diverse with the recent development of lightweight remote sensing instruments. In this paper, we demonstrate our custom integration of the state-of-the-art technologies within an unmanned aerial platform capable of high-resolution and high-accuracy laser scanning, hyperspectral imaging, and photographic imaging. The technological solution comprises the latest development of a completely autonomous, unmanned helicopter by Aeroscout, the Scout B1-100 UAV helicopter. The helicopter is powered by a gasoline two-stroke engine and it allows for integrating 18 kg of a customized payload unit. The whole system is modular providing flexibility of payload options, which comprises the main advantage of the UAS. The UAS integrates two kinds of payloads which can be altered. Both payloads integrate a GPS/IMU with a dual GPS antenna configuration provided by OXTS for accurate navigation and position measurements during the data acquisition. The first payload comprises a VUX-1 laser scanner by RIEGL and a Sony A6000 E-Mount photo camera. The second payload for hyperspectral scanning integrates a push-broom imager AISA KESTREL 10 by SPECIM. The UAS was designed for research of various aspects of landscape dynamics (landslides, erosion, flooding, or phenology) in high spectral and spatial resolution.

Improving the Quality of Low-Cost GPS Receiver Data for Monitoring Using Spatial Correlations

Abstract The investigations on low-cost single frequency GPS receivers at the Institute of Engineering Geodesy (IIGS) show that u-blox LEA-6T GPS receivers combined with Trimble Bullet III GPS antennas containing self-constructed L1-optimized choke rings can already obtain an accuracy in the range of millimeters which meets the requirements of geodetic precise monitoring applications (see [27]). However, the quality (accuracy and reliability) of low-cost GPS receiver data, particularly in shadowing environment, should still be improved, since the multipath effects are the major error for the short baselines. For this purpose, several adjoined stations with low-cost GPS receivers and antennas were set up next to the metal wall on the roof of the IIGS building and measured statically for several days. The time series of three-dimensional coordinates of the GPS receivers were analyzed. Spatial correlations between the adjoined stations, possibly caused by multipath effect, will be taken into account. The coordinates of one station can be corrected using the spatial correlations of the adjoined stations, so that the quality of the GPS measurements is improved. The developed algorithms are based on the coordinates and the results will be delivered in near-real-time (in about 30 minutes), so that they are suitable for structural health monitoring applications.

STUDY OF LEVER-ARM EFFECT USING EMBEDDED PHOTOGRAMMETRY AND ON-BOARD GPS RECEIVER ON UAV FOR METROLOGICAL MAPPING PURPOSE AND PROPOSAL OF A FREE GROUND MEASUREMENTS CALIBRATION PROCEDURE

Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. <i>Vinci-Construction- Terrassement</i> is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3<i>d</i> modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.

STUDY OF LEVER-ARM EFFECT USING EMBEDDED PHOTOGRAMMETRY AND ON-BOARD GPS RECEIVER ON UAV FOR METROLOGICAL MAPPING PURPOSE AND PROPOSAL OF A FREE GROUND MEASUREMENTS CALIBRATION PROCEDURE

Abstract. Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. Vinci-Construction- Terrassement is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3d modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.

Fabrication and Characterization of TiO<sub>2</sub>-Doped ZnAl<sub>2</sub>O<sub>4</sub> Nanocrystals via Sol-Gel Method for GPS Antenna

The Zn(1-x)TixAl2O4 (x = 0.00, 0.05, 0.15 & 0.25) nanocrystals thin films were prepared by sol-gel method. The properties of Zn(1-x)TixAl2O4 were investigated by X-ray diffraction (XRD), Atomic Force Microscope (AFM), Fourier transform infrared spectra (FTIR) and (UV-Vis). By indexing the XRD patterns, we identified three structural types which is ZnAl2O4, anatase and rutile. The addition of TiO2 increased the crystallite size from 14.65 to 25.25 nm. The direct band gap was found to be around 3.35 to 3.84 eV. The addition of TiO2 increased the crystallite size, surface roughness, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (). The thin films were characterized in the certain frequency to determine the using LCR spectrometer. The and density value of the Zn(1-x)TixAl2O4 films increase linearly from 8.56 to 13.48 and 4.60 to 4.70 g/cm3 with the increasing of x value, respectively. Based on the material analysis and microwave antenna theory, GPS patch antennas were fabricated using the Zn(1-x)TixAl2O4 material. The fabricated GPS antenna with the highest (13.48) material exhibits the smallest size of antenna which is 7.45 cm2. The performances and the operating frequencies were measured using a PNA series network analyzer. The result showed that all patch antennas operate at frequency of 1.570 GHz. The GPS patch antenna fabricated from Zn0.25Ti0.75Al2O4 showed an excellent combination of return loss (-29.6 dB), smallest size (7.85 cm2), and wide bandwidth (195 MHz). All fabricated antennas are meets the requirements of GPS applications.

차량 정밀 측위용 이중대역 GPS 안테나 설계

The capability of accurate positioning and tracking is necessary to implement an unmanned autonomous driving system. The moving-baseline GPS Technique is a promising candidate to mitigate positioning errors of conventional GPS system. It provides accurate positioning data based on the phase difference between received signals from multiple GPS antennas mounted on the same platform. In this paper, we propose a dual-band dual-circularly-polarized antenna suitable for the moving-baseline GPS. The proposed antenna operates at GPS L1 and L2 bands, and fed by the side of the antenna instead of the bottom. The antenna is firstly designed by calculating theoretical values of key parameters, and then optimized by means of 3D full-wave simulation software. Simulation and measurement results show that the optimized antenna offers 6.1% and 3.7% bandwidth at L1 and L2, respectively, with axial ratio bandwidth of more than 1%. The size of the antenna is , which is small and low-profile.

Snow depth estimation accuracy using a dual-interface GPS-IR model with experimental results

Measuring snow depth using the GPS interferometric reflectometry is an active microwave remote sensing technique and an emerging approach because of its relatively large spatial coverage and high temporal sampling capability. The current geodetic GPS networks are capable of measuring snow depth in the vicinity of the antenna installation at no additional hardware cost. However, the performance is constrained by the geodetic GPS antenna which was originally designed to minimize the reception of the reflected signal. In our prior work, we proposed a horizontally polarized antenna which has equal gain for both direct and reflected signals and tested its performance for a single snow event. In order to comprehensively assess its performance, we set up a horizontally polarized snow monitor (HPSM) using the improved antenna at Marshall, Colorado, USA, over the 2013---2014 water year. The data from the HPSM clearly shows that the proposed design has high sensitivity to even very light snowfalls. However, some anomalies are observed from the HPSM measurements, which tend to either overestimate or underestimate the actual snow depth. We explain the observed measurement anomalies by replacing the traditional air---snow single-interface model with an air---snow---soil dual-interface model. The effectiveness of the new model is validated by comparing the simulated results to the HPSM measurements. Utilizing the dual-interface model, we simulate the error curve for snow depth estimation given various snow depths and snow permittivities. The error curve shows that the estimation biases can be observed only for shallow snow with a relatively small permittivity value.

A PROXIMITY-FED ANTENNA FOR DUAL-BAND GPS RECEIVER

A new design of dual-band L1/L2 GPS antenna is proposed. The antenna generates dual- band circularly polarized radiation by exciting a cross-slot and ring-slot of a concentric circular aperture using a proximity-coupled feed. Parametric studies show that the matching and axial ratio bandwidth of L1 (1.575 GHz) and L2 (1.227 GHz) bands can be independently tuned by alternating the ring radius and slot length. The range of frequency ratio and 3 dB center frequency can be highly adjusted by slot's parameters. The size of the antenna is 73 mm × 73 mm × 6.4 mm including the ground, corresponding to 0.29λ × 0.29λ × 0.026λ at 1.227 GHz.

Integration of a Dual GPS and ISM Antenna PIFA in a Human Body Patch for Elderly Tracking

This paper introduces the development of two Printed Inverted F Antennas (PIFA) to be integrated in a patch worn on the back of human body. This study is part of SACHA project (Search And Computerize Human Acts) whose main aim is to design a tracking device for monitoring the elderly suffering from Alzheimer disease. The first antenna frequency is 868 MHz and will be used to communicate with a specific SIGFOX communication technology. A second frequency (1575.42 MHz) is used for GPS geolocation. The proposed development is a part of research in Human Health Monitoring field, based on the monitoring of the behavior, the location and the position of the patient, and could deeply help the medical team or family to instantly respond through a warning generation.

A Design of Vehicular GPS and LTE Antenna Considering Vehicular Body Effects

In this paper, a vehicular antenna design scheme considering the vehicular body effects is proposed. A wire antenna for GPS and LTE is implemented on the plastic plate, then it is mounted on the front glass. The outputs are commonly used to share the feed. It is necessary for GPS to increase the right hand circularly polarization (RHCP) gain near the zenith and to reduce the axis ratio while for LTE to increase the horizontal and vertical polarization (HP and VP) gain in the horizontal plane. Also for LTE, multiband characteristics are required. In order to achieve the specified performance, the antenna shape is optimized by Parato genetic algorithm (PGA). When the antenna is mounted on the body, the performance is seriously changed. To evaluate performance of the antenna mounted on the body with a complex shape, a commercial electromagnetic simulator (Ansoft HFSS) is used. To apply electromagnetic results output by HFSS to PGA algorithm operating on the MATLAB, MATLAB to HFSS linking program via Visual BASIC (VB) script was used. It is difficult to carry out the electromagnetic analysis with the whole body because of limitations of the calculating load and memory size. To overcome the limitation, we consider only a predominant part where it has an influence on the performance. It is presented that degradations caused by the body are improved through a series of optimization stages. The simulation results obtained clearly show that it is well optimized at 1.575 for GPS and 766.5 MHz and 2.135 GHz for LTE, respectively.

INTEGRATED FILTERING ANTENNA BASED ON D-CRLH TRANSMISSION LINES FOR ULTRA-COMPACT WIRELESS APPLICATIONS

This paper presents an ultra-compact filtering integrated antenna for GPS (1.57 GHz) and LTE (2.65 GHz) applications. The antenna comprises integration between dual composite right/left- handed antenna and bandstop filter in one platform. The whole integrated antenna size is only 30 × 28. 5m m 2 . Compared to conventional antenna with the same dimensions, the proposed antenna is only 6.5% at GPS band and 16.5% at LTE band. The deign procedures of individual antennas, bandstop filter and the filtering integrated antennas are explained in details. The full wave simulations supporting the design procedures and experimental measurements for all introduced components are introduced with good agreement. Finally, as a consequence of the proposed antenna ultra small size and its filtering capability, the antenna is a good candidate for implanted antenna applications.

North Finding System using Multi-Position Method with a 2-Axis Rotray Table for a Mortar

North-finding techniques involve detecting and calculating the azimuth angle, thus determining north using various kinds of sensors. North identification can be accomplished through the use of a digital magnetic compass. However, the accuracy of a magnetic sensor is easily degraded by spatial and temporal distortions due to a ferrous material or electromagnetic interference. Moreover, GPS-based north-finding systems (NFSs) can accurately determine the azimuth by two separated GPS antennas. However, this still has a practical limitation in jamming or indoor environments. Therefore, an inertial NFS has been developed to replace the classic equipment used in estimating the fire direction of hand-carried projectile weapons such as with mortars. To improve the precision of seeking north with a middle grade gyro, a multi-position method is implemented. Using only a single fiber-optic gyroscope and two MEMS accelerometers on a rotary platform, the north orientation is accurately found by observing the horizontal component of the earth’s rotation vector. With a minimum number of inertial sensors on a manual rotary platform, the NFS can be compact, light-weight, low-cost, and robust enough for easily portable mortar. Using additional auxiliary information, which can be obtained by magnetic sensors, the time for locating north can be dramatically reduced. The test results compared with the navigation grade inertial navigation system show that a single digit mrad heading accuracy can be achieved. The operability of NFS mounted beside a mortar was tested in the field, in which the reference positions were acquired by differential GPS. To insure the durability in gun-fire shock, the drop-tower test was performed based on the shock profile measured in real mortar fire.