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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. [ABSTRACT FROM AUTHOR]

This paper deals with passive remote sensing of fire spots in moving vehicles by a ground-based microwave radiometer mounted near a rail or a road. Images have been simulated at 30 GHz, identifying also dielectric properties of the vehicle wall able to guarantee a penetration of the microwave radiation. The 30-GHz operative frequency can be considered a trade-off between the antenna system dimensions and the penetration capability of microwave radiation through a dielectric wall. It has been seen that the radiation associated to the fire spot emerges distinctly through a dielectric wall in several cases, depending also on fire dimensions, loss tangent values of the wall, and its thickness. This study confirms that the detection of an early stage fire through a dielectric wall by microwave radiometry is promising, taking into account that the use of infrared sensor systems mainly depends on emissivity knowledge of the vehicle surface and on the heating of the monitored external wall. [ABSTRACT FROM PUBLISHER]

This letter proposes wearable electronic modules on textile, suitable for garment integration, based on antennas magnetically coupled to the active circuitry. The coupling mechanism is based on a heterogeneous transformer with the primary and secondary windings implemented in the antenna and in the circuitry substrate (hybrid or monolithic), respectively. The proposed coupling topology avoids galvanic contacts between the antenna and the active circuitry, allowing for interconnecting the antenna by a mere placing and gluing process. Bonding and soldering processes, often critical for textilematerials, are thus avoided. The proposed innovation, mitigating the industrial realization constraints posed by textile implementation of active antennas and radio frequency identification (RFID) tags, should unsurprisingly enable and foster industrial developments of garment RFID, wearable electronics and body-centric communications systems. A patch antenna with transformer based on textile materials and operating in the frequency band 2.4-2.4835 GHz is designed, realized, and measured. [ABSTRACT FROM AUTHOR]

This paper deals with a feasibility study for a System-on-Chip (SoC) mm-wave radiometer devoted to space-based observation of solar flares and operating in the Ka-band. The radiometer has been designed in 250 nm SiGe BiCMOS process. The circuit integrates a three stages differential LNA with 37.2 dB gain and 4.8 dB noise figure at 36.8GHz and a differential square-law detector based on HBTs, featuring a 96mV/µW responsivity. The full radiometer achieves, potentially, a NETD of 0.1K for 1 s integration time in Dicke mode. This work represents the first study of such an integrated instrument for Ka-band space-based observation of solar flares. [ABSTRACT FROM AUTHOR]

This paper deals with 24-GHz circuits developed by exploiting a system-in-package approach. In order to reduce the cost as much as possible, a standard multilayer printed circuit board (PCB) technology has been adopted. Such a circuit consists of a package built utilizing a 0.3-mm thick fiber-glass substrate with 3.38 relative permittivity. The contacts between the substrate and the mother board are realized along the package perimeter exploiting 0.6-mm via-hole metalization and half halo shield soldering pad. First, the developed package is simulated and optimized by means of commercial electromagnetic software. Then a prototype is fabricated and measured. The obtained results show that the whole frequency band from DC to 30 GHz can be covered. A packaged 26.5-mm straight microstrip line exhibits an |S11| value better than -12 dB and an |S21| value of about -1.4 dB at 24 GHz. This value is only 0.6-dB worse than that of the unpackaged line. A single-balanced diode mixer and a low-noise amplifier (LNA) for industrial, scientific, and medical applications are then designed. The integration of these building blocks within the PCB package is finally demonstrated and experimentally verified. The packaged mixer shows a 6.8-dB conversion loss. The packaged LNA, instead, features a 9.1-dB gain with a 3.4-dB noise figure. [ABSTRACT FROM PUBLISHER]

This work deals with the design and fabrication of antennas for radio frequency identification (RFID) tag devices operating in the low microwave frequency range. Paper substrate material and inkjet printing process have been used to guarantee mechanical flexibility and ultra-low production costs of the antenna. A new antenna design methodology has been developed with the purpose to minimise the amount of both substrate material and conductive ink. The first goal is achieved by reducing, for a given frequency, the antenna size. The second goal, instead, is pursued by studying the surface current density distribution along the antenna and removing the metal material where such a current density is negligible. The above methodology has been applied to several antennas designs ranging from a windshield sticker tag to an RFID-SAW antenna. Moreover a 3.5 GHz crossed-dipole tag, based on the frequency-doubling mechanism, is reported along with a possible modification to enable wireless sensing. The experimental characterisation of these prototypes validates the proposed design methodology opening, in the mean time, the possibility for ultra-low cost mass production of RFID tag devices based on paper materials. [ABSTRACT FROM AUTHOR]