GPS Antenna Research Articles

Using dual‐polarization GPS antenna with optimized adaptive neuro‐fuzzy inference system to improve single point positioning accuracy in urban canyons

<h3>Abstract</h3> This paper builds on the machine learning research to propose two new algorithms based on optimizing the Adaptive Neuro Fuzzy Inference System (ANFIS) with a dual-polarization antenna to predict pseudorange errors by considering multiple variables including the right-hand circular polarized (RHCP) signal strength, signal strength difference between the left-hand circular polarized (LHCP) and RHCP outputs, satellites’ elevation angle, and pseudorange residuals. The final antenna position is calculated following the application of the predicted pseudorange errors to correct for the effects of non-line-of-sight (NLOS) and multipath signal reception. The results show that the proposed algorithm results in a 30% improvement in the root mean square error (RMSE) in the 2D (horizontal) component for static applications when the training and testing data are collected at the same location. This corresponds to 13% to 20% when the testing data is from locations away from that of the training dataset.

Зенитная тропосферная задержка по данным GPS наблюдений и измерений радиометром водяного пара в пункте Badg (Бадары, Республика Бурятия)

A comparison was carried out of the values of the total zenith tropospheric delay (ZTD) revealed from the observations of the GPS satellite navigation system and measurements by a microwave radiometer of water vapor (MRWV) at the BADG permanent measurement point located on the territory of the “Badary” Observatory of the Institute of Applied Astronomy of the Russian Academy of Sciences. GPS antenna, MRWV device and meteorological station are located in close proximity to each other. This significantly affected the accuracy of the processed data. The differences in the values of the total zenith tropospheric delay obtained from GPS observations and measurements with a microwave radiometer of water vapor are analyzed in terms of mean and standard deviations and the coefficient of cross-correlation. Comparison of the results for 2020 year showed very good agreement. In summer, the BIAS of the difference between the ZTD data from GPS and MRWV observations is about 0.63% of the average summer ZTD value, the cross-correlation coefficient between the data is K = 0.85. In winter, the BIAS of the difference was about 0.21% of the average winter value of ZTD, the cross-correlation coefficient between the data is about K = 0.93. A high degree of reliability of data on ZTD and tropospheric moisture content obtained by continuous GPS measurements is shown.

Development and Improvement of Real-Time Navigation System for Laparoscopic Hepatectomy

Introduction: We are going to try development of real-time navigation system for laparoscopic hepatectomy, which resembles a car navigation system. We report our real-time navigation system and surgical procedure. Methods: Virtual images are reconstructed using “New-VES” system developed by Nagoya University Graduate School of Information Science. These images correspond to maps of car navigation system. Some of patient's body parts are registered in virtual images using a magnetic position sensor. Patient's body after registration corresponds to The Earth. A transmitter for magnetic position sensor, which corresponds to an artificial satellite, is placed about 30cm above patient's body. A micro magnetic sensor, which corresponds to GPS antenna, fixes on the handling part of laparoscope.Fiducial registration error (FRE) is utilized to evaluate accuracy of real-time navigation system. Results: We performed laparoscopic hepatectomy using this system in 21 patients. Mean FRE of initial 5 patients was 17.7mm. First improvement was that MDCT were taken using radiological markers for registration of body parts. Mean FRE of the 8 patients who utilized first improvement was 10.2mm and decreased (p = 0.014). Second improvement was that a micro magnetic sensor as an intraoperative body position sensor was fixed on the right-sided chest wall and meant that pre- and post- operative FRE was similar due to an intraoperatively automatic correction of gap of body position. Preoperative and postoperative mean FRE of the 8 patients who utilized second improvement were 11.1mm and 10.1mm (p = 0.250). Conclusions: Our real-time navigation system can assist laparoscopic hepatectomy.

Spider Spike Compact Fractal Antenna for GPS, ISM and Medical band Applications

Spider Spike Compact Fractal Antenna for GPS, ISM and Medical band Applications

Pilot Tests of FasTR Method for Locating Transient Faults in Medium Voltage Underground Power Networks

This paper presents the results of pilot tests performed on a real medium voltage (MV) underground network in Switzerland with the aim of assessing the performance of a fault location system. The deployed fault location platform is based on a very sensitive and precise acquisition system which is capable of capturing perturbations or events on a dedicated portion of a given MV network. Thanks to a post processing algorithm based on the tenets of time reversal theory, FasTR method, an accurate localization of relevant events can be worked. Due to the fact that each acquisition system shares a clock reference based on a GPS antenna, the localization accuracy is within tens of meters. To the best of the Authors knowledge, this is the first time that the FasTR-based fault location technique is validated through live tests. The pilot network is a three branch system part of live radial MV distribution feeder consisting of a total of 2.6 km long underground three-phase cables. The branched lines are composed of coaxial cables of different types. The tests involve solid- and resistive-type single-phase-to-ground fault occurrences triggered along one of the laterals when the network is operational. The obtained results demonstrated the capacity of an on-deck portable system to make an on-line accurate detection of transient faults in a complex network.

Gesture controlled quadcopter for defense search operations

This paper is representing an idea on the use of the quadcopter for the sake of the pivotal issues like defense tasks or climate calamities/changes which threaten the world to plunge into hazards. So, we need efficient ways to identify areas of potential hazard risks and monitor them closely in an easier manner. Due to these hazardous and risky challenges it is not always optimal for humans to take up this task rather use a quadcopter for the search and rescue operation to save the lives of the people from risks. The base idea for our drone is to use a DJI NAZA-M Lite Flight controller with GPS antenna, a low latency camera with a 0.33-inch CMOS sensor with a 1.2 mm wide angle (150degree) lens and a transmitter with 2.4 GHz bandwidth makes it suitable at the time of search and rescue. By using an arduino and an MPU6050 sensor, we can map its gyro and accelerometer values to the control sticks of the quadcopter. We have also added a small 5 V speaker along with a couple of other sensors like temperature, rain/humidity sensor, gas sensors etc. The use of these components along with gesture control features can be used at the time of surveillance by defense or at the time of natural calamities for the search and rescue operations making it advantageous to use by any sort of person in these risky situations.

Conformal Anti Jamming GPS Antenna with Directive Elements

در این مقاله آنتنی با هفت عنصر برای دریافت سیگنال GPS روی ساختاری غیر مسطح طراحی شده است که در برابر جمینگ مقاوم بوده و با قطع و وصل کردن تغذیه‌ی عنصر‌ها در زوایای فراز4 و سمت5 مشخصی ایجاد صفر در الگوی تشعشعی می‌کند. در این ساختار از هفت آنتن پچ استفاده شده است که هر کدام روی یک وجه ساختار قرار می‌گیرند و هر عنصر به کمک یک تغذیه قطبش دایروی قابل قبول برای دریافت سیگنال GPS را ایجاد می‌کند. هرچه آنتن‌های به کار رفته در این ساختار جهتدارتر باشد، صفر الگوی تشعشعی عمیقتری ایجاد خواهد شد و در نتیجه مقاومت بیشتری در برابر سیگنال جمینگ به دست خواهد آمد. به دلیل ساختار ساده، وزن کم، ابعاد فشرده، قطبش دایروی، بهره بالا و مقاومت در برابر جمینگ، این ساختار برای به کارگیری در گیرنده‌هایGPS مناسب ‌است.

Field Completion of the GIS database of Cameroon base map using the couple: tablet/GPS antenna

The National Institute of Cartography of Cameroon (NIC) is currently establishing a 1:10,000-scale National GIS data base, from which digital maps are being produced. A new methodology for field completion, which is one of the key phases for the production of a base map, has been implemented in other to meet the requirements of the new database. This method is mainly based on the use of the couple tablet/GPS antenna for surveying, combined with android GIS software used for embedding the first drafts of map sheets. This mapping application consists of buttons which allow executing involved tasks on the field: survey a point, a line, polygon, cancelling a feature or filling an attribute table. The purpose of this paper was to demonstrate the added value of the suggested methodology in terms of accuracy, rapidity and data integration. The results of this case study showed that the achieved accuracy of data collected is around 1 m or sometimes less. The orientation on the field was very fast, and the integration of data collected in the GIS database of NIC was very easy. Keywords: Accuracy, Data integration GPS antenna, Mapping application, Tablet.

Robust 60-GHz Beamforming for UAVs: Experimental Analysis of Hovering, Blockage, and Beam Selection

Unmanned aerial vehicle (UAV) mounted millimeter-wave (mmWave) base stations as well as aerial backhaul links will enable on-demand deployment of network resources. However, prior work has shown aerial links are prone to the frequent disruption caused by: 1) constant hovering due to GPS inaccuracies that impact narrow beamwidths; 2) blockages in the direct line of sight; and 3) suboptimal beam selection, especially if reduced angular sectors are searched in a highly dynamic environment. This article characterizes the impact of each of these phenomena for aerial mmWave links and proposes methods to distinctly identify when they occur in isolation or in combination during deployment. Furthermore, it also proposes corrective actions at the UAV, appropriate for the specific type(s) of impacting events: physical displacement from its earlier location, angular rotation around its vertical axis, or beamwidth adjustment. Our approach relies on exploiting the information contained in the angular domain of a large data set of experimentally collected beam-selection outcomes, under the above practical scenarios. We incorporate GPS accuracy models and antenna radiation patterns to create a robust model of potential outages. We then propose device-agnostic algorithms that jointly optimize UAVs' physical movement and the beamforming procedure. The experimental results obtained by mounting a pair of 60-GHz channel sounders on M600 DJI UAVs reveal loss reduction of up to 74.7%, translated into 260% physical layer bit-rate improvement compared to the classical 802.11ad standards-defined approach.

Performance analysis of IRNSS using compact microstrip patch antenna for S band application

The Indian Regional Navigation Satellite System (IRNSS) is a newly functional regional satellite navigation system around Indian subcontinent. It is also known as its functioning name of NaVIC, Navigation with Indian Constellation, working on L5 and S band. In this paper a compact and low cost circularly polarized microstrip patch antenna is proposed for IRNSS S band application, to provide single frequency navigation solution. Fabrication of proposed antenna is performed using substrate of RT Duroid 5880 with the dimensions of 0.66λ × 0.5λ. The performance of IRNSS is investigated by prototype antenna and Accord made triband antenna with IRNSS/GPS/SBAS receiver which is enable to receive L1, L5 and S band data. The comparison of proposed S band antenna, triband accord system antenna and GPS antenna is presented in terms of carrier to noise ratio and positioning error. Results show that proposed antenna is suitable for S band application of IRNSS receiver.

Precise vehicle dynamic heading and pitch angle estimation using time-differenced measurements from a single GNSS antenna

The attitude information of ground vehicles, i.e., heading and pitch information, can be used for many transport applications. This information can be determined through various solutions of onboard sensors, including magnetic sensors, inertial sensors, GNSS equipment, and their combinations. In order to find a cost-effective solution, we propose here a new toolbox named Vehicle Attitude Determination toolbox from the Intelligent Transportation And Geomatics group (iTAG_VAD) that determines vehicle dynamic heading and pitch using only one single-frequency GPS antenna, reducing costs while retaining an acceptable heading and pitch accuracy. In this toolbox, by using the constraints of the vehicle motion and road geometry, two variations in a time-differenced measurement model, i.e., Time-Differenced Carrier Phase (TDCP) and Time-Differenced Pseudorange (TDPR), are developed for heading and pitch determination. The results show that both proposed TDCP- and TDPR-based models are able to provide an accurate heading and pitch estimation with a root mean square error below the one-degree level, which is sufficient for many land-based applications. We describe the toolbox and its implementation in MATLAB in detail.

Precise topographic mapping using direct georeferencing in UAV

Mapping using UAV has become very popular today due to the rapid development of electronic technology. UAVs are needed to support rapid mapping activities, such as natural disaster management, SAR applications, agricultural applications and forest fire monitoring. In addition to spatial resolution, it is also needed the accuracy of position accuracy. In general, the georeferenced process of aerial photo processing uses Ground Control Points (GCP) from GPS measurements. The disadvantage of using GCP is that GPS measurement takes a long time and the costs incurred are relatively more expensive. For this reason, certain techniques are needed to produce topographic maps with more efficient times. Direct Georeferencing on UAV is an aerial triangulation technique without the use of ground control points (GCP). Direct Georeferencing techniques will cut field surveys and produce high accuracy topographic maps. The hope is that by using this technique, the measurement of tie points can be as minimal as possible and do not even need to use a control point. This study is to evaluate Direct Georeferencing techniques in UAVs to produce accurate topographic map. Aerial photo using multi rotor UAV DJI Phantom 4 RTK/PPK. This multi rotor is equipped with a high accuracy GPS antenna and that is capable to storing GPS observation data. Photo coordinate processing using the Post Processing Kinematic (PPK) method. Accuracy of ortho rectification results of aerial photo geometry compared to check point coordinates (CP). The test results of horizontal accuracy indicate the value of 0.040 m using Circular Error 90% (CE90). Based on BIG standard the accuracy of the base map, these results can be entered on a scale of 1: 1,000 class 1. Direct Georeferencing techniques in UAVs produce high accuracy maps for relatively not extensive mapping areas.

Characterization of on‐orbit GPS transmit antenna patterns for space users

The GPS Antenna Characterization Experiment (GPS ACE) has made extensive observations of GPS L1 signals received at geosynchronous (GEO) altitude, with the objective of developing comprehensive models of the signal levels and signal performance in the GPS transmit antenna side lobes. The experiment was originally motivated by the fact that data on the characteristics and performance of the GPS signals available in GEO and other high Earth orbits was limited. The lack of knowledge of the power and accuracy of the side lobe signals on-orbit added risk to missions seeking to employ the side lobes to meet navigation requirements or improve performance. The GPS ACE Project lled that knowledge gap through a collaboration between The Aerospace Corporation and NASA Goddard Space Fight Center to collect and analyze observations from GPS side lobe transmissions to a satellite at GEO using a highly-sensitive GPS receiver installed at the ground station. The GPS ACE architecture has been in place collecting observations of the GPS constellation with extreme sensitivity for several years. This sensitivity combined with around-the-clock, all-in-view processing enabled full azimuthal coverage of the GPS transmit gain patterns over time to angles beyond 90 degrees o -boresight. Results discussed in this paper include the reconstructed transmit gain patterns, with comparisons to available pre-fight gain measurements from the GPS vehicle contractors. For GPS blocks with extensive ground measurements, the GPS ACE results show remarkable agreement with ground based measurements. For blocks without extensive ground measurements, the GPS ACE results provide the only existing assessments of the full transmit gain patterns. The paper also includes results of pseudorange deviation analysis to assess systematic errors associated with GPS side lobe signals.

IoT based Speed Monitoring System based on Location of the Vehicle

Nowadays there is an increasing amount of road accidents happening around the world. The amount of road accidents is especially high in metropolitan cities. The main reason for road accidents is almost always due to the negligence on part of the driver. Maximum number of Road Accidents occur due to over-speeding and drunk driving. This system helps detect over-speeding vehicles by directly implementing the particular hardware inside the vehicle itself and depending on the GPS position of the car and regional speed limits alert the authorities based on the violation. This technique helps us to reduce costs which need to be incurred to install speed cameras at roads at regular intervals. The system will detect the speed of the car, and in case of a violation the license plate number along with the registration details and the photo of the driver will be directly sent to the concerned authorities. This system aims to decrease the amount of accidents that happen across the globe and help conserve human lives. Road accident still remain one of the highest contributors to the loss of human life. For experimental results, we used raspberry pi and the GPS antenna for detection of over speed and alert the authorities on violation.

Copernicus Sentinel-1 satellites: sensitivity of antenna offset estimation to orbit and observation modelling

Abstract. The SAR (Synthetic Aperture Radar) Copernicus Sentinel-1 satellites require a high orbit accuracy of 5 cm in 3D in comparison to external processing facilities. The official orbit products delivered by the Copernicus POD (Precise Orbit Determination) Service fulfil this requirement. Nevertheless, analyses have shown discrepancies in the orbit results for the two satellites Sentinel-1A and Sentinel-1B. Since the satellites are identical in construction estimated orbit parameters like the scale factor for the radiation pressure are expected to be at the same magnitude, which is not the case. Estimation of GPS antenna offsets leads to differences between the two satellites, which might explain the discrepancies in the estimated orbit parameters. Such offset estimations are, however, very sensitive to orbit and observation modelling. It has to be assured that the results are not biased by insufficient models. First of all, stabilisation of the antenna offset estimation is achieved by improving the observation modelling by applying single receiver ambiguity resolution. The Copernicus Sentinel-1 satellites have a very complex shape with the long SAR antenna and the two large solar arrays. Antenna offset estimation based on different satellite models may give results which differ by up to 1.5 cm. The dispersion of the estimates is quite large depending also on eclipse and non-eclipse periods. Consideration of simple assumptions on satellite self-shadowing effects improves the satellite model and also the results of the antenna offset estimation. Finally, more consistent results for the two Sentinel-1 satellites are achieved by applying the antenna offset estimates.

Satellite based Navigational System Errors

When two or more signals of the satellite signals arrives through a GPS antenna with different tracks it leads to multipath phenomenon. The two main classifications of multipath phenomenon are specular and diffuse multipath. In the multipath pertaining to specular phenomenon the signals of GPS are reverberated through relatively sleek surfaces resulting in unsystematic errors within both pseudorange and carrier phase measurements. In contrast, diffuse phenomenal multipath is considered when the signal of GPS is incidental along a rough exterior where the reverberated signals are dispersed in various directions and generally they are unrelated in time period domain and it is noisy in activity. The stated unsystematic in-accurateness tin to be significant and leads to misconceptions of meters in the range in regard of pseudo range and for phase measurements at a range of a few centimeters . As the positioning mechanism needs to be be precised needs the straight path betwixt the satellites and a receiver, as the phenomenon of multipath doesn’t exist. The phenomenal multipath occurrences for the associated misconceptions in a GPS apparents eventually evidences for navigational misconceptions. Topical studies on GPS and its applications stimulate the necessitate for an improved multipath characterization techniques, to have an increased admiration for the spatial complexity and sequential of specific- position multipath environments.

Co-Design of a GPS Antenna Low-Noise Amplifier Front-End Circuit

This paper presents a clear and fast design procedure for directly matched low noise active integrated microstrip antenna front end circuits. Initially, a theoretical analysis is given for the overall gain equivalence between traditional and directly matched antennas. Then, a detailed procedure is presented for the design and construction of a fully integrated GPS antenna. To validate the proposed procedure, a prototype was built and characterized by measuring the reflection coefficient, radiation pattern, noise figure and the active antenna overall gain. Additionally, a field test comparison was made between the manufactured prototype and a commercially available active antenna using the u-blox NEO-6M GPS receiver module. The prototype experimental and field test results showed excellent performance, thus validating the proposed co-design approach.

A Simplified Model for Predicting the Installed Performance of Circularly Polarized Antennas

We propose a simplified equivalent model for predicting the installed performance of circularly polarized (CP) antennas. We use a set of infinitesimal sources to represent the irradiated fields of an antenna of interest; however, instead of using infinitesimal dipoles, our source is composed of a set of infinitesimal crossed dipoles, the most basic radiator that generates CP waves. This choice facilitates the optimization process and still maintains the analytical aspect of the model; the irradiated fields can be described analytically. We achieve a reduction in computational cost when comparing to direct modeling, without impairing the accuracy of the model during the antenna placement task, and a reduction of optimization time when comparing to classical dipole models. Also, the equivalent model building step has reduced a computational cost for CP antennas. In order to validate our model, we construct a scaled model of a circular cylinder with a top-mounted GPS antenna, and we measure its radiation pattern in an anechoic chamber. The experimental results are in remarkable agreement with those simulated using the proposed equivalent model.

Snow Depth Estimation on Slopes Using GPS-Interferometric Reflectometry.

Snow is one of the most critical sources of freshwater, which influences the global water cycle and climate change. However, it is difficult to monitor global snow variations with high spatial–temporal resolution using traditional techniques due to their costly and labor-intensive nature. Nowadays, the Global Positioning System Interferometric Reflectometry (GPS-IR) technique can measure the average snow depth around a GPS antenna using its signal-to-noise ratio (SNR) data. Previous studies focused on the use of GPS data at sites located in flat areas or on very gentle slopes. In this contribution, we propose a strategy called the Tilted Surface Strategy (TSS), which uses the SNR data reflected only from the flat quadrants to estimate the snow depth instead of the conventional strategy, which employs all the SNR data reflected from the whole area around a GPS antenna. Three geodetic GPS sites from the Plate Boundary Observatory (PBO) project were chosen in this experimental study, of which GPS sites p683 and p101 were located on slopes with their gradients up to 18% and the site p025 was located on a flat area. Comparing the snow depths derived with the GPS-IR TSS method with the snow depth results provided with the GPS-PBO, i.e., GPS-IR with the conventional strategy, the Snowpack Telemetry (SNOTEL) network measurements and gridded Snow Data Assimilation System (SNODAS) estimates, it was found that the snow depths derived with the four methods had a good agreement, but the snow depth time series with the GPS-IR TSS method were closer to the SNOTEL measurements and the SNODAS estimates than those with GPS-PBO method. Similar observations were also obtained from the cumulative snowfall time series. Results generally indicated that for those GPS sites located on slopes, the TSS strategy works better.

Circularly Polarized Array with Enhanced Isolation Using Magnetic Metamaterials

This article proposes a 2 × 2 circularly polarized array with enhanced isolation that could be used in the adaptive anti-jamming system for China’s Beidou Navigation Satellite System (BDS), and a compact dual-band microstrip antenna for GPS and GLONASS is designed at the center part of the array for multiple modes operation. The substrate integrated split ring resonators with negative effective permeability are used as the magnetic metamaterials. Four groups of the magnetic metamaterials are placed between the BDS antenna elements, which could constrain the EM filed in the area of the active element, and then significantly reduce the mutual coupling among the elements. The results tell that the isolation among the BDS elements are improved by more than 10 dB, and the performance of radiation patterns and the axial ratio of each BDS elements are also apparently improved compared to the array without magnetic metamaterials.