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Optimised Performance of Non-Dispersive Infrared Gas Sensors Using Multilayer Thin Film Bandpass Filters
摘要： In this work, performance improvements are described for a low-power consumption non-dispersive infrared (NDIR) methane (CH4) gas sensor using customised optical thin film bandpass filters (BPFs) centered at 3300 nm. BPFs shape the spectral characteristics of the combined mid-infrared III–V based light emitting diode (LED)/photodiode (PD) light source/detector optopair, enhancing the NDIR CH4 sensor performance. The BPFs, deposited using a novel microwave plasma-assisted pulsed DC sputter deposition process, provide room temperature deposition directly onto the temperature-sensitive PD heterostructure. BPFs comprise germanium (Ge) and niobium pentoxide (Nb2O5) alternating high and low refractive index layers, respectively. Two different optical filter designs are progressed with BPF bandwidths (BWs) of 160 and 300 nm. A comparison of the modelled and measured NDIR sensor performance is described, highlighting the maximised signal-to-noise ratio (SNR) and the minimised cross-talk performance benefits. The BPF spectral stability for various environmental temperature and humidity conditions is demonstrated.
关键词： III–V,sensor,methane,thin film,MBE,NDIR,microwave,bandpass,sputter,heterostructure,infrared
更新于2025-09-23 15:23:52
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[IEEE 2018 International Carnahan Conference on Security Technology (ICCST) - Montreal, QC, Canada (2018.10.22-2018.10.25)] 2018 International Carnahan Conference on Security Technology (ICCST) - Microwave Quantum Radar: An Experimental Validation
摘要： We describe an experiment which comes very close to implementing a quantum radar based on entangled microwaves. A pair of entangled microwave beams are generated using a Josephson parametric amplifier (JPA) and measured by a pair of digitizers after amplification. We present a receiver operating characteristic (ROC) curve for the case where the signal power at the digitizers is ?83.84 dBm (corresponding to a JPA power output, before amplification, of ?148.26 dBm), as well as for a classically correlated source which attempts to approximate the covariance structure of the entangled JPA signals. The entangled signals are seen to be clearly superior to the classically correlated signals. Although the latter is still interesting from a noise radar perspective, this demonstrates that attempting to simulate entanglement with classical signals causes a measurable decrease in correlation. Our experiment validates the feasibility and desirability of a microwave quantum radar.
关键词： entanglement,Quantum radar,microwave,noise radar,correlation
更新于2025-09-23 15:23:52
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[IEEE 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Amsterdam (2018.8.27-2018.8.30)] 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - High-Resolution Near-Field Imaging and Far-Field Antenna Measurements with Atomic Sensors
摘要： Measurements of radio-frequency (RF) electric fields using atomic sensors based on quantum-optical spectroscopy of Rydberg states in vapors has garnered significant interest in recent years for the establishment of atomic standards for RF electric fields and towards the development of novel RF sensing instrumentation. Here we describe recent work employing atomic sensors for sub-wavelength near-field imaging of a Ku-band horn antenna. We demonstrate near-field imaging capability at a spatial resolution of λ/10 and measurements over a 72 to 240 V/m field range using off-resonance AC-Stark shifts of a Rydberg-atom resonance. A fiber-coupled atomic-sensor probe is also employed in far-field measurements of a WR-90 standard gain horn.
关键词： electromagnetic compatibility,Rydberg,atom,quantum sensing,RF,metrology,antenna characterization,microwave,Atomic sensors,electric field,antenna,radio-frequency
更新于2025-09-23 15:23:52
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Frequency Extension of Atomic Measurement of Microwave Strength Using Zeeman Effect
摘要： Measuring the field strength of an electromagnetic wave based on atomic quantum mechanics is expected to be an innovative method to realize stable and reliable measurements. However, the major issue of atomic measurements is that the measurable frequency is limited to the resonant frequency of atoms. Therefore, in this paper, we demonstrate the measurement at arbitrary frequencies using the Zeeman effect in a static magnetic field. A cesium vapor cell is placed in a static magnetic field of approximately 40 mT, which causes the resonant frequency of the cesium atom to shift from 9.2 to 8.2 GHz. In addition, the Rabi frequency due to the interaction between cesium atoms and microwaves is measured at the frequency of 8.2 GHz in this experiment.
关键词： frequency measurement,microwave measurements,metrology,microwave spectroscopy,electromagnetic measurements,Atom optics,atomic measurements,measurement standards
更新于2025-09-23 15:22:29
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Ultrathin Microwave Devices for Polarization-Dependent Wavefront Shaping Based on an Anisotropic Metasurface
摘要： Metasurfaces have recently become a promising material, offering new degrees of freedom in molding electromagnetic wave properties. In this work, we propose and numerically investigate ultrathin microwave devices for polarization-dependent wavefront shaping based on an anisotropic metasurface, which consists of a square metal ring with a cross, a dielectric substrate, and a metal ground plane. It is demonstrated the proposed metasurface can independently manipulate reflective x- and y-polarized wavefronts at frequency of 15 GHz via engineering of the metal cross. Furthermore, the reflective efficient is extremely high, reaching a near-unity value of 0.98. Based on this anisotropic metasurface, a polarization beam splitter is achieved by artificially arranging the spatial distribution of metasurfaces with prescribed geometries. In addition, we successfully design a focusing metasurface to separate the x- and y-polarized beams via focusing them at different positions. The proposed approach paves a way toward the applications of the metasurface in a microwave band.
关键词： electromagnetic metamaterials,microwave propagation,beam steering,microwave antennas
更新于2025-09-23 15:22:29
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Photonic approach for microwave frequency measurement using a silicon microring resonator
摘要： We propose and experimentally demonstrate a photonic measurement approach of microwave frequency with adjustable measurement ranges and low errors based on a silicon microring resonator (MRR). The key factor is that microwave photonic filters (MPFs) with high rejection ratios could be realized by a phase modulator, an optical filter and a silicon MRR. In the experiment, by adjusting the wavelength of the laser diode, tunable MPFs with rejection ratios beyond 60 dB are realized in order to construct different amplitude comparison functions (ACFs) with high frequency resolutions (30dB/GHz). According to the mapping relationships between the microwave frequency and power ratio of the ACF, the unknown microwave frequency could be measured. The experimental results show that microwave frequency could be measured from 10 GHz to 19 GHz with a measurement resolution of 0.08 GHz. In the future, the measurement ranges and frequency resolutions could be manipulated according to practical requirements. The photonic measurement method and compact device are significant in microwave systems.
关键词： on-chip microwave system,Microwave frequency measurement,adjustable measurement range
更新于2025-09-23 15:22:29
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Novel Three-Dimensional SiC/Melamine-Derived Carbon Foam-Reinforced SiO <sub/>2</sub> Aerogel Composite with Low Dielectric Loss and High Impedance Matching Ratio
摘要： Novel three-dimensional SiC/melamine-derived carbon foam composite filled by silica aerogel (SiC/MDCF?Aerogel) was first fabricated by the pyrolysis process of commercial melamine foam, chemical vapor deposition of ultrathin SiC films, and the sol?gel method of silica aerogel. The results indicated that the SiC/MDCF?Aerogel composite consisted of the SiC three-dimensional open-celled network structure and the pregnant silica aerogel in the pores. Tiny cracks on the interface of skeletons and clumps were induced during the aging process, which was drastically beneficial to the microwave-absorbing properties. A minimum reflection loss could be obtained as low as ?18.41 dB at the measured frequency of 16.92 GHz when the thickness of the absorber was 3.65 mm, and the reflection loss could drop below ?10 dB when the selected frequencies ranged from 15.80 to 17.52 GHz, along with the thickness ranging from 2.75 to 5.0 mm, which possessed a relatively better microwave absorption performance especially at a higher frequency. Furthermore, the absorption mechanism was also investigated in detail to discuss the influence of the dielectric loss and the impedance matching ratio on the microwave-absorbing performance of SiC/MDCF?Aerogel, which provided certain scientific directions for evaluating the absorbing materials.
关键词： Minimum reflection loss,Tiny cracks,Microwave-absorbing properties,Impedance matching ratio,Dielectric loss,SiC/MDCF?Aerogel
更新于2025-09-23 15:22:29
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Generation of mmWave 5G Signals Using Microwave Photonics
摘要： Bandwidth constraints is, nowadays, a mayor problem in the implementation of next generation 5G networks. In order to cope with increasing bandwidth demands, the use of the millimeter-wave (mmWave) spectrum, together with Radio over Fiber (RoF) technology has been proposed. In this work, we will present our recent advances in the generation of mmWave signals for 5G using Microwave Photonics.
关键词： microwave photonics,mobile optical communications,radio over fiber
更新于2025-09-23 15:22:29
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Tunable Phase Shifter Based on Few-Layer Graphene Flakes
摘要： This letter presents a voltage-controlled tunable phase shifter based on few-layer graphene. The phase shifter consists of a stub-loaded line, composed of a microstrip line with a stub attached to it through a taper and graphene pad. The bias voltage applied to the graphene pad determines a variation of graphene resistance, which eventually causes the phase change. Without any voltage bias, graphene exhibits high resistance, thus isolating the stub and leading to a low phase shift. As the bias voltage is increased, graphene resistance is lowered, the effect of the stub is more pronounced, and the phase shift is increased. A prototype operating in the frequency range from 5 to 6 GHz has been designed and tested. The measured maximum phase shift obtained is 40°, and the corresponding degradation of the insertion loss is 3 dB.
关键词： tunable microwave devices,graphene,phase shifter,Few-layer graphene
更新于2025-09-23 15:22:29
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DESIGN OF DUAL- AND QUAD-BAND E-CRLH-TLS WITH ARBITRARY PHASE CHARACTERISTICS
摘要： In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component.
关键词： microwave component,metamaterial,phase shift,dual-band,E-CRLH,quad-band,transmission line
更新于2025-09-23 15:22:29