This work demonstrates a new approach – Scheimpflug lidar – for atmospheric aerosol monitoring. The atmospheric backscattering echo of a high-power continuous-wave laser diode is received by a Newtonian telescope and recorded by a tilted imaging sensor satisfying the Scheimpflug condition. The principles as well as the lidar equation are discussed in details. A Scheimpflug lidar system operating at around 808 nm is developed and employed for continuous atmospheric aerosol monitoring at daytime. Localized emission, atmospheric variation, as well as the changes of cloud height are observed from the recorded lidar signals. The extinction coefficient is retrieved according to the slope method for a homogeneous atmosphere. This work opens up new possibilities of using a compact and robust Scheimpflug lidar system for atmospheric aerosol remote sensing.

This work presents a detailed study of the theoretical aspects of the Fourier analysis method, which has been utilized for gas absorption harmonic detection in wavelength modulation spectroscopy (WMS). The lock-in detection of the harmonic signal is accomplished by studying the phase term of the inverse Fourier transform of the Fourier spectrum that corresponds to the harmonic signal. The mathematics and the corresponding simulation results are given for each procedure when applying the Fourier analysis method. The present work provides a detailed view of the WMS technique when applying the Fourier analysis method.

An 808 nm single-band Mie scattering Scheimpflug lidar system is developed in Dalian, Northern China, for real-time, large-area atmospheric aerosol/particle remote sensing. Atmospheric measurement has been performed in urban area during a typical haze weather condition, and time-range distribution of atmospheric backscattering signal is recorded from March 18th to 22nd, 2017, by employing the Scheimpflug lidar system. Atmospheric extinction coefficient is then retrieved according to the Klett-inversion algorithm, while the boundary value is obtained by the slope-method in the far end where the atmosphere is homogeneous in a subinterval region. The correlation between the extinction coefficients retrieved from the Scheimpflug lidar technique and the PM10/PM2.5 concentrations measured by a conventional air pollution monitoring station is also studied. The good agreement between the measurement results, i.e., a correlation coefficient of 0.85, successfully demonstrates the feasibility and great potential of the Scheimpflug lidar technique for atmospheric studies and applications.

In this work, wideband dual-polarized dielectric resonator antenna (DRA) arrays are designed for 5G mobile handsets and integrated with the sub-6GHz antenna. The dielectric resonators, surrounded by concentric air holes and metal vias, are excited by two orthogonal slots and fed through microstrip lines, providing a wide bandwidth from 25.3 GHz to 29.8 GHz. A high isolation of above 40 dB is obtained between the ports of the orthogonally polarized antennas. Based on the dual-polarized DRA, two 14 arrays are built and integrated with the longer metal frames of the handset, without occupying extra space on the chassis. The scanning angle for the proposed array is from 47 to 121 for the gain of above 10 dBi, and the overall handset antennas provide a large coverage efficiency of 80 % for a threshold gain of 5 dBi. User effect has also been investigated, manifesting that the horizontally polarized antennas are less influenced by the hands in both the one-hand and the two-hand data modes. Furthermore, a sub-6GHz antenna is designed with a wide operating band from 0.7 GHz to 0.94 GHz simply by making use of the shorter frames and the dual-layered DRAs, with a small ground clearance of 2mm remained. The performances of the arrays are validated by measuring the representative antennas. The proposed antenna is a good candidate for future handsets due to its high integration with the metal frames and with the LTE antenna, its large bandwidth and large coverage in free space and different user scenarios.

This paper reports a mini-resonant photoacoustic sensor for high-sensitivity trace gas sensing. The sensor primarily contains a sphere-cylinder coupled acoustic resonator, a cylindrical buffer chamber, and a fiber-optic acoustic sensor. The acoustic field distributions of this mini-resonant photoacoustic sensor and the conventional T-type resonant photoacoustic sensor have been carefully evaluated, showing that the first-order resonance frequency of the present mini-resonant photoacoustic sensor is reduced by nearly a half compared to that of the T-type resonant photoacoustic sensor. The volume of the developed photoacoustic cavity is only about 0.8 cm³. Trace methane is selected as the target analytical gas and a detection limit of 101 parts-per-billion at 100-s integration time has been achieved, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 1.04 × 10^-8 W·cm^-1·Hz^-1/2. The developed mini-resonant photoacoustic sensor provides potential for high-sensitivity trace gas sensing in narrow spaces.