A 1 x 8 Linear Ultra-Wideband Phased Array With Connected Dipoles and Hyperbolic Microstrip Baluns

A 1×8 linear single polarized ultra-wideband connected dipole phased array with wide angle scan range is proposed. The dipoles in the array are connected with each other in E-plane to improve the impedance matching on the low end of the frequency band. The frequency band and the scan range in E-plane is 2~9 GHz for broadside radiation, 2~8 GHz for 30° scan, 2~7 GHz for 45° scan, and 2~6.5 GHz for 60° scan. The VSWR is better than 2.0 across the frequency band from 2 to 9 GHz for broadside radiation and the cross-polarization level is below -10 dB. A hyperbolic microstrip balun is used as an impedance transformer to connect the 50 Ω SMA connector to a 150 Ω broadband dipole in an array. The structure of this antenna is totally planar and low profile, thus it is made easy to integrate with the PCB boards. To eliminate the surface wave blindness, no other dielectric layer is used in the array. The proposed balun supports common mode (CM) current and the radiation of this CM current cancels the radiation of the dipole in some frequency for a certain scan angle, this results in feed blindness. Adding H-plane PEC walls decreases the feed blindness frequency in the design

Phononic-Crystal-Based Particle Sieving in Continuous Flow: Numerical Simulations

Sieving specific particles from mixed samples is of great value in fields such as biochemistry and additive manufacturing. In this study, a particle sieving method for microfluidics was proposed based on a phononic crystal plate (PCP), the mechanism of which originates from the competition between the trapping effect of the resonant PCP-induced acoustic radiation force (ARF), disturbance effect of acoustic streaming (AS), and flushing effect of the continuous inlet flow on particles suspended in microfluidic channels. Specifically, particles with different sizes could be separated under inlet flow conditions owing to ARF and AS drag forces as functions of the particle diameter, incident acoustic pressure, and driving frequency. Furthermore, a comprehensive numerical analysis was performed to investigate the impacts of ARF, AS, and inlet flow conditions on the particle motion and sieving efficiency, and to explore proper operating parameters, including the acoustic pressure and inlet flow velocity. It was found that, for each inlet flow velocity, there was an optimal acoustic pressure allowing us to achieve the maximum sieving efficiency, but the sieving efficiency at a low flow velocity was not as good as that at a high flow velocity. Although a PCP with a high resonant frequency could weaken the AS, thereby suiting the sieving of small particles (<5 μm), a low channel height corresponding to a high frequency limits the throughput. Therefore, it is necessary to design a PCP with a suitable resonant frequency based on the size of the particles to be sieved. This investigation can provide guidance for the design of massive acoustic sorting mi-crofluidic devices based on phononic crystals or acoustic metamaterials under continuous flow

A Real-Time Monitoring Method for Civil Aircraft Take-Off and Landing Based on Synthetic Aperture Microwave Radiation Technology

It is important to monitor the take-off and landing of civil aircraft using passive detection methods. Due to the strict aircraft safety requirements and the electromagnetic environment around an airport, using too many active detection methods should be avoided. Using an aircraft’s microwave radiation signal detection is very advantageous because it does not actively emit signals and has a strong cloud penetration, suitable for all-weather observation. This paper introduces a synthetic aperture microwave radiation system for monitoring the take-off and landing of civil aircraft, which is characterized by real-time two-dimensional imaging, and the image refresh rate can reach 10 ms, which meets the high refresh rate requirements for aircraft imaging. Applicable system parameters and antenna array distribution scheme and imaging algorithm are given. Then the paper focuses on the error analysis and correction method of the system. The correction method is simple and fast, which avoids the disadvantage that the error needs to be corrected regularly in the laboratory environment, and is suitable for airport application. Finally, the simulation and experimental results show that this technology can be used for real-time monitoring of civil aircraft during take-off and landing, and it is a practical means to assisting landing