Antenna Temperature Research Articles

Analysis of Passive Millimeter Wave Detection Signal Based on Entropy Feature

It is easy to be planar metal and ground water mistakenly identified as an armored target, when the signal amplitude value was deemed as a decisive characteristic in passive millimeter wave detection system. Aiming at this problem, this paper proposes a new characteristic which named entropy. The extraction method of entropy is proposed from the point of view of the antenna temperature of typical objects in the millimeter wave passive detection. Studied a certain amount of samples detection signal’s entropy. The results showed that the entropy of the armored targets and metal plane and ground water have obvious difference, the armored target recognition research provides a new analysis method and theoretical guidance.

Model of description of the process of functioning of combined correlation-on-extremal system of navigation of the unbeiled flying apparat

The results of the development of a formalized model of the process of functioning of a combined correlation-extreme navigation system are presented. The factors that lead to the formation of a multi-extremal decision function of a combined correlation-extreme navigation system are determined. The model of the current image, which is formed by separate channels according to informative features, is made more precise, depending on the spatial position of the pilotless flying device. A block diagram of the description of the process of functionalization of a combined correlation-extreme navigation system is presented. The influence of the three-dimensional shape of the sighting surface objects on the effective antenna temperature of the radiometric channel was taken into account, which allowed the refinement of the radiometric current image description model depending on the informative signs of the images. The model of the formation process of the solving function of the combined correlation-extreme navigation system is clarified, taking into account the influence of the three-dimensional shape of the sighting objects and random changes in the spatial position of the flying apparatus. Relations are obtained for describing the current images of the sighting surface in the radiometric and television channels of a combined correlation-extreme navigation system, taking into account the three-dimensional shape of the objects of interference and random changes in the spatial position of the aircraft caused by the turbulence of the atmosphere. An expression describing the process of formation of the solving function of a combined correlation-extreme navigation system is presented. Variants of the scenario for the formation of a decisive function are presented depending on the conditions of the operational-tactical situation. The expediency of forming a single standard for television and radiometric channels of a combined correlation-extreme navigation system is substantiated.

An Efficient Gain Estimation in the Calibration of Noise-Adding Total Power Radiometers for Radiometric Resolution Improvement

Calibration of microwave radiometers is a crucial task for reliable and accurate antenna temperature measurements in remote sensing applications. This paper describes a processing procedure for data calibration of noise-adding (NA) total power (TP) radiometers, without thermal stabilization, able to improve the radiometric resolution performance and keep good accuracy. This method, easily implementable, is based on the strong dependence of the radiometric gain on the internal physical temperature of the system. It provides a calibration of the output voltage measured in the TP mode exploiting the noise source power injection only every 30 min. The quality of the proposed procedure was assessed by means of three experiments carried out in different years and environmental conditions, using a low-cost NA TP radiometer operating at 12.65 GHz. The measurements show an uncertainty better than 0.7 K and, above all, a clear improvement in radiometric resolution (below 0.1 K). The radiometric resolution benefit is particularly appreciable in applications where the aim is the detection of small radiation power increments. Two experimental tests show how this method for data calibration effectively resolves the warm target counting inside the antenna footprint, while the same data measured with the standard NA procedure do not allow the same detection capability.

Development of high quality factor microwave ceramics for application in wireless high temperature patch antenna sensor

The microwave dielectric properties of (Mg0.93Zn0.07)2SnO4 ceramics were examined with a view to their exploitation for wireless high temperature patch antenna sensor. The (Mg0.93Zn0.07)2SnO4 ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the (Mg0.93Zn0.07)2SnO4 ceramics revealed no significant variation of phase with sintering temperatures. Specimens were not single-phase, small amounts of SnO2 as the second phase were observed in all specimens. A dielectric constant ( $${\varepsilon _r}$$ ) of 8.3, a quality factor (Q × f) of 171,300 GHz (at 17.5 GHz), and a temperature coefficient of resonant frequency ( $${\tau _f}$$ ) of − 69 ppm/°C were obtained for (Mg0.93Zn0.07)2SnO4 ceramics that were sintered at 1550 °C for 4 h. The developing procedures and test results for patch antenna temperature sensor composed of (Mg0.93Zn0.07)2SnO4 ceramics were recorded. The test results included the variation of frequency over operating temperature range, sensitivity, return loss, and 3 dB bandwidth. The resonating frequency, return loss, and 3 dB bandwidth measured at 20 °C were 2.48 GHz, − 15.0 dB and 63 MHz, respectively. A sensitivity of − 0.17 MHz/°C was successfully achieved.

МОДЕЛІ ПОТОЧНИХ ЗОБРАЖЕНЬ, ЩО ФОРМУЮТЬСЯ КАНАЛАМИ КОМБІНОВАНОЇ КОРЕЛЯЦІЙНО-ЕКСТРЕМАЛЬНОЇ СИСТЕМИ НАВІГАЦІЇ БЕЗПІЛОТНОГО ЛІТАЛЬНОГО АПАРАТУ

A refinement of the current image model has been accomplished, which are formed by separate channels of the combined correlation-extreme navigation system depending on the spatial position of the unmanned aerial vehicle and its changes. The model takes into account the influence of the three-dimensional shape of complex objects of the sighting surface on the effective antenna temperature of the radiometric channel, which made it possible to refine the moles of the description of the radiometric and television current image of the sighting surface, depending on the informative features. It is determined that at small viewing altitudes the change in the spatial position of the unmanned aerial vehicle leads to significant differences in the radio brightness temperature within a single sighting object, which causes the blurring and appearance of new interfaces on the current image of the viewing surface. It is established that the discrepancy between the current image and the reference image, which arises from the appearance of new interfaces at the sight of complex three-dimensional objects from low altitudes and with a change in the spatial position and orientation of the unmanned aerial vehicle, leads to the formation of a multi-extremal decision function and a decrease in the accuracy of the location of the correlation-extreme navigation system.

TRMM MICROWAVE IMAGER (TMI) ALIGNMENT AND ALONG-SCAN BIAS CORRECTIONS.

The Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) dataset released by the Precipitation Processing System (PPS) has been updated to a final version following the decommissioning of the TRMM satellite in April 2015. The updates are based on increased knowledge of radiometer calibration and sensor performance issues. In particular, the Global Precipitation Measurement (GPM) Microwave Imager (GMI) is used as a model for many of the TMI updates. This paper discusses two aspects of the TMI data product that have been reanalyzed and updated: alignment and along-scan bias corrections. The TMI pointing accuracy is significantly improved over prior PPS versions, which used at-launch alignment values. ATMI instrument mounting offset is discovered as well as new alignment offsets for the two TMI feedhorns. The original TMI along-scan antenna temperature bias correction is found to be generally accurate over-ocean, but a scene temperature-dependent correction is needed to account for edge-of-scan obstruction. These updates are incorporated into the final TMI data version, improving the quality of the data product and ensuring accurate geophysical parameters can be derived from TMI.

Assessment and Adaptive Correction of Observations in Atmospheric Sounding Channels of the Satellite Microwave Radiometer MTVZA-GY

The microwave radiometer MTVZA-GY on board the Russian polar orbiting meteorological satellite Meteor-M N2 is briefly described. Errors and biases in antenna brightness temperatures are documented. Observation errors are found to be dependent on the solar angles. An adaptive bias correction technique for MTVZA-GY antenna temperatures is motivated and developed. The technique accounts for the solar angles and sequentially assimilates observed minus simulated radiances in a perpetual 24 h cycle in order to estimate up-to-date correction coefficients defined to be functions of the zenith and azimuth solar angles. The simulated radiances are computed by the RTTOV radiative transfer model from three-dimensional numerical weather prediction fields. The correction technique is implemented for atmospheric temperature and humidity sounding channels of MTVZA-GY. The corrected observations are shown to be significantly more accurate as compared with raw antenna temperatures and with observations that undergo simpler and more traditional corrections. The accuracy of corrected MTVZA-GY observations is compared with the accuracy of AMSU-A and MHS data.

Photothermal Heating of Plasmonic Nanoantennas: Influence on Trapped Particle Dynamics and Colloid Distribution

Plasmonic antennas are well-known and extremely powerful platforms for optical spectroscopy, sensing, and manipulation of molecules and nanoparticles. However, resistive antenna losses, resulting in highly localized photothermal heat generation, may significantly compromise their applicability. Here we investigate how the interplay between plasmon-enhanced optical and thermal forces affects the dynamics of nanocolloids diffusing in close proximity to gold bowtie nanoantennas. The study is based on an anti-Stokes thermometry technique that can measure the internal antenna temperature with an accuracy of ∼5 K over an extended temperature range. We argue that Kapitza resistances have a significant impact on the local thermal landscape, causing an interface temperature discontinuity of up to ∼20% of the total photothermal temperature increase of the antenna studied. We then use the bowties as plasmonic optical tweezers and quantify how the antenna temperature influences the motion and distribution of nearby f...

Near-field communication tag development on a paper substrate—application to cold chain monitoring

The purpose of this study was the development and testing of a near-field communication (NFC) tag for cold chain monitoring. In this paper, we validated the use of large-surface printing technologies to make a high-frequency antenna (13.56 MHz) and carbon-based temperature sensor on an Arjowiggins’ Powercoat™ paper substrate. The printed temperature sensor was connected to the output of the analog–digital converter of a commercial microprocessor. A direct temperature reading interface was developed. The main objectives were to demonstrate the potential of screen printing processes for the development of an NFC tag, and to validate the use of a printed resistive sensor for cold chain monitoring. The validation was carried out through the comparison of a reference temperature recorded by a thermocouple regarding the temperature recorded by the external printed sensor in the case of a cold chain break simulation.

Modeling of an Uncooled CMOS THz Thermal Detector With Frequency-Selective Dipole Antenna and PTAT Temperature Sensor

A thermal THz detector based on commercial CMOS technology working in room temperature is proposed. The THz electromagnetic wave is first selectively absorbed by an on-chip λ/4 dipole antenna realized in the metallization layer. The absorbed wave energy is then converted to Joule heat energy via a polysilicon resistor. The heat-generated temperature rise is finally detected by a proportional to absolute temperature sensor. The theoretical analysis and physical modeling of the detector including the mechanism of the electromagnetic energy absorption, the thermal conversion, and the electrical circuit response, are presented. The detectors at three typical THz frequencies of 1, 2.9, and 28.3 THz are designed in standard 0.18-μm CMOS technology and post-simulated to illustrate the detector's frequency-selective capability in the whole THz range. The simulated detector's voltage responsivity is 18.0 V/W at 1 THz, 18.9 V/W at 2.9 THz, and 18.6 V/W at 28.3 THz, respectively. The noise equivalent power is 1.7 μW/√Hz at the three frequencies.

Microwave dielectric properties of Nd(Ti0.5−xZrx)W0.5O4 ceramics for application in antenna temperature sensor

The microwave dielectric properties of Nd(Ti0.5−xZrx)W0.5O4 ceramics were examined with a view to their application in mobile communication. The Nd(Ti0.5−xZrx)W0.5O4 ceramics were prepared using the conventional solid-state method. Dielectric constants ( $${\varepsilon _r}$$ ) of 15.4–19.4 and quality factor (Q × f) of 3600–11,100 GHz were obtained for NdTi0.5W0.5O4 ceramics at sintering temperatures in the range 1425–1525 °C for 4 h. A maximum density of 6.68 g/cm3 was obtained for the Nd(Ti0.47Zr0.03W0.5)O4 ceramic, sintered at 1500 °C for 4 h. A Nd(Ti0.47Zr0.03W0.5)O4 ceramic that was sintered at 1500 °C for 4 h had a dielectric constant ( $${\varepsilon _r}$$ ) of 19.8, a quality factor (Q × f) of 17,300 GHz, and a temperature coefficient of resonant frequency ( $${\tau _f}$$ ) of − 54 ppm/°C. The proposed patch antenna sensor had a sensitivity of 0.112 MHz/°C.

Absolute Calibration of the MTVZA-GY Microwave Radiometer Atmospheric Sounding Channels

The microwave MTVZA-GY imager/sounder is one of the key instruments onboard the Meteor-M N2 satellite (launched in July, 2014). The MTVZA-GY data assimilation in numerical weather prediction (NWP) schemes should provide a significant positive impact. The method of absolute calibration for MTVZA-GY atmospheric sounding channels is under discussion. Absolute calibration means converting the antenna temperatures, measured by the MTVZA-GY, to the sensor brightness temperatures and is performed using accurate radiance simulations for selected regions. The NWP products are used as input to the radiance simulation code together with the data on surface emissivity. For the sea surface, emissivity is calculated with a parameterized model. For the land surface, emissivity is specified using a public database. The results of absolute calibration of the MTVZA-GY temperature (52–57 GHz) and humidity (183.3 GHz) sounding channels are presented.

Emission from Magnetized Accretion Disks around Young Stars

Abstract We calculate the emission of protoplanetary disks threaded by a poloidal magnetic field and irradiated by a central star. The radial structure of these disks was studied by Shu and collaborators and the vertical structure was studied by Lizano and collaborators. We consider disks around low-mass protostars (LMPs), T Tauri stars, and FU Ori stars with different mass-to-flux ratios . We calculate the spectral energy distribution and the antenna temperature profiles at 1 and 7 mm convolved with the Atacama Large Millimeter/submillimeter Array (ALMA) and Very Large Array (VLA) beams. We find that disks with weaker magnetization (high values of ) emit more than disks with stronger magnetization (low values of ). This happens because the former are denser, hotter, and have larger aspect ratios, receiving more irradiation from the central star. The level of magnetization also affects the optical depth at millimeter wavelengths, being larger for disks with high . In general, disks around LMP and T Tauri stars are optically thin at 7 mm, while disks around FU Ori are optically thick. A qualitative comparison of the emission of these magnetized disks, including heating by an external envelope, with the observed millimeter antenna temperature profiles of HL Tau indicates that large cm grains are required to increase the optical depth and reproduce the observed 7 mm emission at large radii.

Development and assessment of the SMAP enhanced passive soil moisture product

Launched in January 2015, the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) observatory was designed to provide frequent global mapping of high-resolution soil moisture and freeze-thaw state every two to three days using a radar and a radiometer operating at L-band frequencies. Despite a hardware mishap that rendered the radar inoperable shortly after launch, the radiometer continues to operate nominally, returning more than two years of science data that have helped to improve existing hydrological applications and foster new ones.Beginning in late 2016 the SMAP project launched a suite of new data products with the objective of recovering some high-resolution observation capability loss resulting from the radar malfunction. Among these new data products are the SMAP Enhanced Passive Soil Moisture Product that was released in December 2016, followed by the SMAP/Sentinel-1 Active-Passive Soil Moisture Product in April 2017.This article covers the development and assessment of the SMAP Level 2 Enhanced Passive Soil Moisture Product (L2_SM_P_E). The product distinguishes itself from the current SMAP Level 2 Passive Soil Moisture Product (L2_SM_P) in that the soil moisture retrieval is posted on a 9km grid instead of a 36km grid. This is made possible by first applying the Backus-Gilbert optimal interpolation technique to the antenna temperature (TA) data in the original SMAP Level 1B Brightness Temperature Product to take advantage of the overlapped radiometer footprints on orbit. The resulting interpolated TA data then go through various correction/calibration procedures to become the SMAP Level 1C Enhanced Brightness Temperature Product (L1C_TB_E). The L1C_TB_E product, posted on a 9km grid, is then used as the primary input to the current operational SMAP baseline soil moisture retrieval algorithm to produce L2_SM_P_E as the final output. Images of the new product reveal enhanced visual features that are not apparent in the standard product. Based on in situ data from core validation sites and sparse networks representing different seasons and biomes all over the world, comparisons between L2_SM_P_E and in situ data were performed for the duration of April 1, 2015–October 30, 2016. It was found that the performance of the enhanced 9km L2_SM_P_E is equivalent to that of the standard 36km L2_SM_P, attaining a retrieval uncertainty below 0.040m3/m3 unbiased root-mean-square error (ubRMSE) and a correlation coefficient above 0.800. This assessment also affirmed that the Single Channel Algorithm using the V-polarized TB channel (SCA-V) delivered the best retrieval performance among the various algorithms implemented for L2_SM_P_E, a result similar to a previous assessment for L2_SM_P.

Soil Moisture Active/Passive L-Band Microwave Radiometer Postlaunch Calibration

The Soil Moisture Active/Passive (SMAP) microwave radiometer is a fully polarimetric L-band radiometer flown on the SMAP satellite in a 6 a.m./6 p.m. sun-synchronous orbit at 685-km altitude. Since April 2015, the radiometer has been under calibration and validation to assess the quality of the radiometer L1B data product. Calibration methods, including the SMAP L1B TA2TB [from antenna temperature (TA) to the Earth’s surface brightness temperature (TB)] algorithm and TA forward models, are outlined, and validation approaches for calibration stability/quality are described in this paper, including future work. Results show that the current radiometer L1B data product (version 3) satisfies its requirements (uncertainty <1.3 K and calibration drift <0.4 K/months, and geolocation uncertainty <4 km) although there are biases in TA over cold sky and in TB comparing with the Soil Moisture and Ocean Salinity TB v620 data products.

A Novel Sensor Based on a Single-Pixel Microwave Radiometer for Warm Object Counting: Concept Validation and IoT Perspectives.

Controlled measurements by a low-cost single-pixel microwave radiometer operating at 12.65 GHz were carried out to assess the detection and counting capability for targets warmer than the surroundings. The adopted reference test targets were pre-warmed water and oil; and a hand, both naked and wearing a glove. The results showed the reliability of microwave radiometry for counting operations under controlled conditions, and its effectiveness at detecting even warm targets masked by unheated dielectric layers. An electromagnetic model describing the scenario sensed by the radiometer antenna is proposed, and comparison with the experimental observations shows a good agreement. The measurements prove that reliable counting is enabled by an antenna temperature increment, for each target sample added, of around 1 K. Starting from this value, an analysis of the antenna filling factor was performed to provide an instrument useful for evaluating real applicability in many practical situations. This study also allows the direct people counting problem to be addressed, providing preliminary operational indications, reference numbers and experimental validation.

Enabling the Extraction of Climate-Scale Temporal Salinity Variations from Aquarius: An Instrument Based Long-Term Radiometer Drift Correction

All channels of the Aquarius radiometer were observed to have calibration instability consisting of a drift in the antenna temperature during the first couple of months of the mission and pseudo-periodic oscillations of the antenna temperature over the mission life. For the version 4 Aquarius processing, both of these anomalies were corrected by removing a time variable bias in the Aquarius measurements relative to a seven-day global average from a salinity model. In order to accurately track long-term variation of salinity on climate scales it is necessary to decouple Aquarius radiometric calibration from ocean salinity models. In this paper, a new technique is used to investigate the nature of anomalies using nonocean vicarious external sources such as Antarctic ice or Amazonian rain forests. Two completely different solutions are developed to correct the pseudo-periodic oscillations as well as the drift of the Aquarius radiometers, decoupling the Aquarius measurements from salinity model.

Comments on “G/T and Noise Figure of Active Array Antennas”

The most cited paper from this journal with “array,” “antenna,” and “noise” in its metadata is <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . While the quantitative results of that paper are correct, there is an issue with its treatment of noise received by array antennas due to noise radiation from the background (external noise). Equation (1) of that paper gives noise received by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> th array element, and the text describes the noise temperature ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{i}$ </tex-math></inline-formula> ) in that equation as the “antenna (sky) temperature.” This should clearly be the temperature corresponding to the background noise received by the individual array elements, which includes all contributions from within the gain pattern of the individual element, which is typically much broader than the pattern of the array. However, later in the paper, this same symbol is used as the temperature corresponding to the background noise received by the array (into the receiver in Lee’s Fig. 1, after losses). These two temperatures can be very different. For example, small, individual elements of a large array could receive substantial contributions from the ground and other hot objects (e.g., at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T \sim 300$ </tex-math></inline-formula> K), while the array’s receiver only receives significant contributions from a very quiet region of the sky (e.g., at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T \sim 4$ </tex-math></inline-formula> K at some frequencies).

CALIBRATION OF THE EDGES HIGH-BAND RECEIVER TO OBSERVE THE GLOBAL 21 cm SIGNATURE FROM THE EPOCH OF REIONIZATION

ABSTRACT The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the 21 cm signal from the epoch of reionization in the redshift range . To probe this redshifted signal, EDGES High-Band conducts single-antenna measurements in the frequency range 90–190 MHz from the Murchison Radio-astronomy Observatory in Western Australia. In this paper, we describe the current strategy for calibration of the EDGES High-Band receiver and report calibration results for the instrument used in the 2015–2016 observational campaign. We propagate uncertainties in the receiver calibration measurements to the antenna temperature using a Monte Carlo approach. We define a performance objective of 1 mK residual rms after modeling foreground subtraction from a fiducial temperature spectrum using a five-term polynomial. Most of the calibration uncertainties yield residuals of 1 mK or less at confidence. However, current uncertainties in the antenna and receiver reflection coefficients can lead to residuals of up to 20 mK even in low-foreground sky regions. These dominant residuals could be reduced by (1) improving the accuracy in reflection measurements, especially their phase, (2) improving the impedance match at the antenna-receiver interface, and (3) decreasing the changes with frequency of the antenna reflection phase.

SMAP L-Band Microwave Radiometer: Instrument Design and First Year on Orbit.

The Soil Moisture Active-Passive (SMAP) L-band microwave radiometer is a conical scanning instrument designed to measure soil moisture with 4% volumetric accuracy at 40-km spatial resolution. SMAP is NASA's first Earth Systematic Mission developed in response to its first Earth science decadal survey. Here, the design is reviewed and the results of its first year on orbit are presented. Unique features of the radiometer include a large 6-m rotating reflector, fully polarimetric radiometer receiver with internal calibration, and radio-frequency interference detection and filtering hardware. The radiometer electronics are thermally controlled to achieve good radiometric stability. Analyses of on-orbit results indicate that the electrical and thermal characteristics of the electronics and internal calibration sources are very stable and promote excellent gain stability. Radiometer NEDT < 1 K for 17-ms samples. The gain spectrum exhibits low noise at frequencies >1 MHz and 1/f noise rising at longer time scales fully captured by the internal calibration scheme. Results from sky observations and global swath imagery of all four Stokes antenna temperatures indicate that the instrument is operating as expected.