This article presents a center‐feed parasitic circular patch antenna with continuously tuning linear polarization performance. Eutectic gallium‐indium liquid metal alloy is employed to tune the angle of linear polarization continuously. The antenna is feed at the center of a circular patch with a ring slot. The rotational symmetry of the antenna helps maintain the impedance and radiation pattern at different polarization angles. The liquid metal is contained in a 1 × 1 mm channel etched in a polymethyl methacrylate cylinder. The polarization angle is tuned by controlling the location of a short bar of EGaln. The center resonant frequency of the demonstrated antenna is 5.19 GHz with a −10 dB impedance bandwidth of 0.24 GHz.
Prsented is a Yagi antenna with improved out-of-band gain suppression to reduced the demands on the front end band filter. Two parasitics close to the fed element are used to increase the Q-factor of that element, and the length and position of the other directors and reflectors are optimised to suppress the out-of-band gain. Simulated and measured results show that the proposed antenna has the characteristics of a conventional Yagi antenna in the passband, albeit with a narrower bandwidth, whilst providing more than 10 dB of gain suppression to interference signals located outside the band.
Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar.
The effects of the Faraday rotation mirror on the all-fiber optic current sensor (AFOCS) are studied in this paper. The reflectivity degradation of FRM with the long-term operation, the misalignment of the optical axis between FRM and the sensing fiber, and the influence of temperature fluctuation on FRM are modeled and simulated in this paper. The effect of temperature is the biggest obstacle to the application of the Faraday rotation mirror, while other factors can be easy to overcome by the data processing method. The experiments are designed and realized for verification. The temperature fluctuation range is related to the measured electric current to satisfy the required accuracy for IEC 60044-8 class 0.2S.
Acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the all-fiber current sensor with a pulsed light source. The pulsed light is realized by amplitude modulation with AOM. The reflected interferometer current sensor is constructed by the mirror and phase modulation with EOM to improve the anti-interference ability. A correlation demodulation algorithm is applied for data processing. The influence of the modulation frequency and duty cycle of AOM on the optical system is determined by modeling and experiment. The duty cycle is the main factor affecting the normalized scale factor of the system. The modulation frequency mainly affects the output amplitude of the correlation demodulation and the system signal-to-noise ratio. The frequency multiplication factor links AOM and EOM, primarily affecting the ratio error. When the frequency multiplication factor is equal to the duty cycle of AOM and it is an integer multiple of 0.1, the ratio error of the system is less than 1.8% and the sensitivity and the resolution of AFOCS are 0.01063 mV/mA and 3 mA, respectively. The measurement range of AFOCS is from 11 mA to 196.62 A, which is excellent enough to meet the practical requirements for microcurrent measurement.
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