A fully photonics-based coherent radar system

The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion. Until now, the photonics-based generation and detection of radio-frequency signals have been studied separately and have not been tested in a radar system. Here we present the development and the field trial results of a fully photonics-based coherent radar demonstrator carried out within the project PHODIR. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Fully coherent S- and X-band photonics-aided radar system demonstration

A fully coherent dual band radar system based on a single photonic-assisted transceiver is presented. Photonic technologies have been used for simultaneous generation and detection of radar signals in the S- and X-band. The sharing of a single transceiver for both the frequency bands allows for a perfect coherence among the generated waveforms. The system has been tested in an operative aerial scenario, and the presented target detections demonstrate the effectiveness of the proposed architecture

Stability and desolvatation of droperidol isostructural solvates

Darba ietvaros tika iegūti droperidola metanola, etanola, dihlormetāna, hloroforma, acetonitrila un nitrometāna izostrukturālie solvāti. Neizotermiskās desolvatācijas kinētikas pētījumiem tika veikta termogravimetriska minēto solvātu desolvatācija dažādos karsēšanas ātrumos, konstantā inertas gāzes plūsmā. Visiem solvātiem noteikta aktivācijas enerģija un pēc desolvatācijas kinētiskajiem parametriem eksperimentālie dati salīdzināti un skaidroti ar literatūrā pieejamajiem kinētiskajiem modeļiem. Izostrukturālie solvāti un desolvāti tika identidficēti, izmantojot pulvera rentgendifraktometriju.Droperidol methanol, ethanol, dichloromethane, chloroform, acetonitrile and nitromethane isostructural solvates were synthesized. For investigating desolvation kinetics non-isothermal thermogravimetric analysis was applied at various heating rates, maintaining inert gas flow. Desolvation activation energy was determined. Experimental data from thermogravimetry were compared with several possible kinetic models found in literature. Powder X-ray diffractometry was used for identifying isostructural solvates and desolvates

A 0-40 GHz RF tunable receiver based on photonic direct conversion and digital feed-forward lasers noise cancellation

This paper presents the architecture of a compact, robust, and broadly tunable RF receiver based on photonic direct conversion and digital feed-forward lasers noise cancellation. In the proposed solution, the incoming RF signal is filtered and down converted to baseband by means of an optical direct conversion (i.e., I/Q) receiving scheme (named here as signal receiver) fed by two free-running semiconductor lasers. At the same time, the beat noise of the free-running lasers is acquired by a second down-converter (reference sensor) fed by the same lasers. Then, the noise information is used by the digital feed-forward noise cancelling algorithm to enhance the frequency resolution provided by the signal receiver. The proposed strategy avoids complex lasers feedback-locking mechanisms, such as electrical/optical phased-locked loop or optical injection locking, as well as bulky RF components such as filters banks and synthesizers. An experimental validation shows an RF input range of 0-40 GHz, instantaneous bandwidth of 2 GHz, carrier noise of ∼-120 dBc/Hz (@ 4 kHz), out-of-band rejection >80 dB, and tuning response <10 μs. Implementing the scheme through integrated photonics technologies should enable increased environmental stability and a chip-scale form factor