Circularly Polarized Dual-Band LoRa/GPS Antenna for a UAV-Assisted Hazardous Gas and Aerosol Sensor

UAV assisted wireless sensor networks play a key role in the detection of toxic gases and aerosols. UAVs can be used to remotely deploy sensor nodes and then collect gas concentration readings and GPS positioning from them to delimit an affected area. For such purpose, a dual-band communication system is required, supporting GPS reception, and sensor reading data transfer, which is chosen to be at 2.4 GHz using LoRa physical layer. In this work we propose a switched-beam antenna subsystem for the sensor nodes capable not only of satisfying the dual band requirements but also of maximizing communication range or energy consumption through a good antenna polarization match and improved antenna gain. This antenna subsystem is built using dual-port, dual-band, circularly polarized antenna elements, whose design and experimental validation is carefully detailed. A low profile microstrip stacked structure has been used to obtain return loss in both bands better than 15 dB, axial ratios below 1.5 dB, and wide −3 dB beamwidths around 90° and 75° for GPS and 2.4 GHz bands, respectively, thus limiting the gain reduction of the switched-beam system in critical sensor orientations. Special attention has been paid to reduce the coupling between both ports through the optimization of the relative placement of both patches and their feeding points. The measured coupling is below −30 dB.

Optimization of Wireless Communication Coverage in Underground Tunnels Based on Zone Division

In order to reduce the path loss of the wireless communication signal in the underground tunnel, a scheme for configuring the antenna polarization of wireless systems based on a zone-division method is proposed. A multimodal method is used to estimate the effect of antenna polarization on the wireless propagation. When the optimal polarization of the antenna leading to low path loss is different in the zones near and far from the transmitting antenna, a dividing point is used to separate the zones. Experiments are conducted in an underground mine. It shows that the results by the multimodal method are consistent with the real data. Compared with the existing coverage schemes, the proposed scheme can obtain better coverage. Meanwhile, zone division has an important influence on the optimized performance of the wireless coverage. The zones divided based on Fresnel zone clearance and system identification are too small or too large, which result in incorrect polarization switching and high path loss.

Shielding Elektromagnetik Tembaga dari Proses Elektrolisis Air Limbah Industri Printed Circuit Board

Some electronic products have high electromagnetic interference so that it gives a negative impact on the electronic devices around it. The use of electromagnetic shielding is a solution to reduce the value of electromagnetic radiation interference from electronic products. The research conducted includes the manufacture of electromagnetic shielding from copper material resulting from the electrolysis process of PCB (Printed Circuit Board) industrial wastewater and analyzing the effect of electromagnetic shielding from copper waste on the value of radiation emission. Electromagnetic shielding is made of vinyl which is coated with copper as a result of the electrolysis of PCB industrial wastewater. The measurement results show that electromagnetic shielding from copper waste can reduce radiation emissions. The use of electromagnetic shielding from copper waste is effective at frequencies from 250 to 350 MHz with a decrease in the quasi-peak value of 38.02 dB. The measurements with horizontal antenna polarization show that the margin of radiation emission value is higher comparated to vertical antenna polarization.Sebagian produk elektronika memiliki gangguan interferensi elektromagnetik yang tinggi, sehingga berdampak kurang baik terhadap perangkat elektronika di sekitarnya. Pemanfaatan shielding elektromagnetik menjadi solusi untuk mengurangi nilai gangguan radiasi elektromagnetik yang dimiliki oleh produk elektronika. Penelitian yang dilakukan meliputi pembuatan shielding elektromagnetik dari bahan tembaga hasil dari proses elektrolisis limbah industri PCB (Printed Circuit Board) dan melakukan analisa pengaruh shielding elektromagnetik dari limbah tembaga terhadap nilai emisi radiasi. Shielding elektromagnetik terbuat dari bahan vinyl yang dilapisi dengan tembaga hasil elektrolisis limbah cair industri PCB. Hasil pengukuran menunjukkan bahwa shielding elektromagnetik dari limbah tembaga dapat menurunkan emisi radiasi. Penggunaan shielding elektromagnetik dari limbah tembaga efektif di frekuensi 250 – 350 MHz dengan penurunan nilai quasi-peak sebesar 38,02 dB. Pada pengukuran dengan polarisasi antena horisontal, margin nilai emisi radiasi lebih tinggi jika dibandingkan dengan polarisasi antena vertikal. Kata Kunci: Shielding elektromagnetik, Emisi radiasi, Tembaga, PCB

High-efficiency antenna-to-antenna polarization converters for customized polarization angle deflection

In this paper, an antenna-to-antenna method to design high-efficiency polarization converters was proposed. Two in-linked split ring resonators (SRRs) were used as the fundamental unit cell, which can effectively make the original linear polarization angle deflected into a customized one (include but not limited to 90°). The same as the process of energy reception and transmitting of microstrip symmetric dipole antennas, the top SRR plays the role of a receiving antenna and the bottom one acts as a transmitting antenna. Under normal illumination, the strong coupling between electric resonance and magnetic resonance can result in high transmission and broad bandwidth. Since the two SRRs act as two independently polarization selective components, the polarization angle of transmitted waves can be easily controlled by rotating the transmitting SRRs around the center. The proposed concept and the design method are validated using numerical simulations, as well as experimental results of three examples for 45, 60 and 90° polarization angle rotation, the polarization conversion ratio of which is about 92.2, 88.9 and 91.9% from 7.5 to 10 GHz.