Microwave couplers are used in large numbers in beamforming networks, and their miniaturization can lead to a significant size reduction in the overall phased array. While the miniaturization of 3 dB ...couplers in the transverse direction (width) has been given considerable attention in the literature, there is minimal to no information on reducing coupler length. This is because of the trade-off between aperture length, bandwidth and coupling strength. The Bethe–Hole theory requires adding multiple apertures in the longitudinal direction for wide bandwidth, thus increasing the device length. Another factor is the aperture size, which determines the coupling strength and puts additional strain on the compactness of a 3 dB coupler. Contrariwise, this paper proposes to merge two weak (and hence compact) coupling mechanisms to design a wideband 3 dB coupler. This is achieved by using a longitudinal rectangular slot and three cross-slots in the transverse direction. Because of weak coupling, the slot sizes are smaller than a conventional 3 dB coupler, hence yielding a device whose length is less than one guided wavelength (λg) without compromising the bandwidth. The presented coupler is 0.63 λg in length, which is smaller than the state-of-the-art while maintaining a fractional bandwidth of 37% that is comparable to half-mode substrate integrated waveguide (HMSIW) couplers.
The article discusses the features of training radio specialists for sea transport, taking into account international and national requirements for the qualifications of seafarers. It is emphasized ...that only persons who have diplomas and qualification certificates of the established form are allowed to occupy the positions of ship’s crew members. As part of the study, qualification documents were systematized for a GMDSS limited area operator, GMDSS operator, GMDSS second class radio electronics, radiotelephone operator and GMDSS first class radio electronics. The areas, types and tasks of the professional activity of the graduates of the educational program “Radio communication and electrical radio navigation of the marine fleet” have been determined. Among the main objects of professional activity, radio-electronic equipment on ships and coastal centers of sea and water transport is highlighted. It was emphasized that the results of training specialists are assessed by the acquired universal, general professional and professional competencies, i.e. the ability to apply knowledge, skills and personal qualities in accordance with the tasks of professional activity. The article examines modern trends in determining the quality of education by using internal and external assessments. It is concluded that the training of radio specialists for maritime transport in modern conditions is of great importance, especially taking into account the development of transportation along the Northern Sea Route and the industrial development of the Arctic. At the same time, the defining condition is the inclusion of international and national requirements in the educational process, then graduates in the field of radio communication and electric radio navigation of the marine fleet will be in demand in the Russian and foreign freight market.
The design of a radio communication system employing orbital angular momentum (OAM) mode multiplexing is described. Rotman lenses followed by circular antenna arrays are used to transmit and receive ...radio frequency beams carrying OAM. In our experiment, two 3 × 3 Rotman lenses are fabricated to feed the three-element circular arrays with certain phase gradients for OAM modes multiplexing and demultiplexing. The OAM-carrying beams of mode number l = +1, 0, and -1 are generated at 9.7 GHz, with each channel carrying an independent data stream of 40 Mbit s -1 quadrature phase shift keying signal in a bandwidth of 20 MHz. And all three channels are recovered with bit error rates below the forward error correction limit of 3.8 × 10 -3 .
Cell-free massive MIMO and symbiotic radio communication have been recently proposed as the promising beyond fifth-generation (B5G) networking architecture and transmission technology, respectively. ...To reap the benefits of both, this paper studies cell-free symbiotic radio communication systems, where a number of cell-free access points (APs) cooperatively send primary information to a receiver, and simultaneously support the passive backscattering communication of the secondary backscatter device (BD). We first derive the achievable communication rates of the active primary user and passive secondary user under the assumption of perfect channel state information (CSI), based on which the transmit beamforming of the cell-free APs is optimized to characterize the achievable rate-region of cell-free symbiotic communication systems. Furthermore, to practically acquire the CSI of the active and passive channels, we propose an efficient channel estimation method based on two-phase uplink-training, and the achievable rate-region taking into account CSI estimation errors is further characterized. Simulation results are provided to show the effectiveness of our proposed beamforming and channel estimation methods.
Recently, much attention has been focused on beams carrying orbital angular momentum (OAM) for radio communication. Here we experimentally demonstrate a planar-spiral phase plate (planar-SPP) for ...generating arbitrary mixed OAM beams. This proposed planar-SPP uses the concept of transmit array antenna having a perforated substrate to control the outputting phase for generating beams carrying OAM with arbitrary modes. As demonstrations, three planar-SPPs with a single OAM mode and two mixed OAM modes around 94 GHz have been investigated with design and experiments in this paper, respectively. The typical experimental intensity and phase patterns show that the proposed method of generating OAM beams really works.
We compare the technique of using the orbital angular momentum (OAM) of radio waves for generating multiple channels in a radio communication scenario with traditional multiple-in-multiple-out (MIMO) ...communication methods. We demonstrate that, for certain array configurations in free space, traditional MIMO theory leads to eigen-modes identical to the OAM states. From this we conclude that communicating over the sub-channels given by OAM states is a subset of the solutions offered by MIMO, and therefore does not offer any additional gains in capacity.
After years in the field and countless conversations with colleagues, I have come to appreciate that academic museums and libraries have much in common. From organizational structures to digital and ...physical collection challenges, staff in both campus departments can benefit greatly from enhanced collaboration and research sharing. Academic museum professionals can learn from the rich research base in leadership studies created by academic librarians, while academic librarians can leverage the work of visual thinking strategies and museum studies curricula to enhance student and faculty engagement. In essence, this brief opinion is all about leveraging new perspectives and the power of reframing our present situation to solve problems in new ways. To borrow from my own past experience, I once found myself trying to reframe and reinterpret a situation over twenty years ago in the small cockpit of a two-seater Cessna 152 aircraft. Like many student pilots before me, I ended up losing track of my position at some point during a solo cross-country trip from Joliet to Champaign, Illinois. Climbing to a higher altitude where I could see the landscape differently and improve radio communications made all the difference. This was particularly true in an era where stopwatches, paper maps, and plotters in the cockpit were standard navigational aids before GPS was commonplace.
Radio communication systems are very widely present in our current smart lifestyles. It consists of two ends, which can carry the transmitter's information to the receptor. Before installing any ...radio communication system, it is necessary to analyze the link resources. Hence, this analysis allows the determination of the received radio communication strength to prove if it is sufficient for the link to work correctly and assure a high quality of service. For this reason, new services and technologies are integrated. The objective of the present work is to improve the performance of the radio communication link of 4G systems. The study is based on real measurements using the drive test. The data collected by the drive test are analyzed to increase the performance of the radio communication. Based on this data analysis, recommendations and suggestions are issued for improving the radio communication link. The obtained results indicate a significant amelioration in the performance of the radio communication link.
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