Wideband Dual Circularly Polarized Antenna for Intelligent Transport Systems

A wideband dual circularly polarized (DCP) antenna is presented for intelligent transport system (ITS) applications, which can be used to improve the receiver sensitivity and communication quality of ITS. The presented DCP antenna is composed of an orthogonal power divider (OPD) with two orthogonal input ports, four phase shifters for quadrature phase output, and four crossed dipoles for DCP radiation. Detailed equivalent circuit analysis shows that the OPD has two orthogonal inputs and four equal magnitude in-phase and out-of-phase outputs. To achieve two sets of orthogonal quadrature output signals for DCP radiation, the lumped element based differential right-hand transmission line unit cell and left-hand transmission line unit cell are elaborately introduced as the ±45° phase shifters, and incorporated into the OPD. Eventually, orthogonal quadrature signals are successfully obtained and fed to the crossed dipoles for DCP radiation. The proposed antenna was then designed, fabricated, and measured for ITS applications. The measured results show that the overlapped impedance bandwidth of both two input ports is 1.07–1.85 GHz (53.4%), and the isolation is higher than 15.2 dB. Moreover, low axial ratio (<1.7 dB) and symmetrical radiation patterns are achieved for unidirectional DCP radiation

Measurement-based Geometrical Characterization of the Vehicle-to-Vulnerable-Road-User Communication Channel

Vehicle-to-vulnerable road user (V2VRU) communications have the ability to provide 360 degrees of awareness to both vehicles and vulnerable road users (VRUs) to prevent accidents. An accurate V2VRU channel model in critical accident scenarios is essential to develop a reliable communications system. Therefore, extensive wideband single-input and single-output (SISO) channel measurement campaigns at 5.2 GHz were carried out in open-field and urban environments. Accident prone scenarios between a vehicle and a cyclist as well as between a vehicle and a pedestrian are considered. In this paper, locations of the scatterers in the propagation environment are estimated. We propose a method to extract specular MPCs from the estimated time variant channel impulse response (CIR) based on the density of neighboring MPCs. The specular MPCs are then tracked using a novel tracking algorithm based on the multipath component distance (MCD) approach. Each path is then related to a physical scatterer in the propagation environment by employing a joint delay-Doppler estimation. According to the results, single and double bounce reflections from buildings and parked vehicles are identified in line-of-sight (LoS) situation. In non-LoS (NLoS) situation, scattering from nearby trees as well as reflections from traffic signs and lampposts beneath the trees canopy are identified

Dual-Band Full-Duplex Tx/Rx Antennas for Vehicular Communications

This paper proposes a novel dual-band full-duplex antenna/array for intelligent transport systems (ITS) applications. Different from traditional single-port single-band antennas, the two ports of the antenna are highly isolated and designed to operate at different frequency bands simultaneously. Such a property could support the full-duplex operation-mode, which significantly simplifies the complexity of the RF frontend subsystem. The other contribution of this work is that multiple functions such as filtering, duplexing and radiation are combined into one single device, resulting in a simplified RF frontend. This co-design multifunctional device could also remove the separate filters, duplexers and interfaces between them, resulting in the reduction of the size, weight and cost. In addition, cross-coupling is investigated and employed to generate additional transmission zeros so as to improve the channel isolation and out-of-band interference. To verify the concept, an antenna element and two 2 × 2 arrays at C-band are designed, prototyped and tested. All the measurements agree well with the simulations, showing two full-duplex channels of 4.58 - 4.83 GHz and 5.86 - 6.2 GHz for transmitting and receiving, respectively. The proposed antennas also exhibit excellent performance in terms of channel isolations, frequency selectivity, out-of-band rejections and gains

Tracking of Wideband Multipath Components in a Vehicular Communication Scenario

A detailed understanding of the dynamic processes of vehicular radio channels is crucial for its realistic modeling. In this paper, we present multipath components (MPCs) tracking results from a channel sounder measurement with 1-GHz bandwidth at a carrier frequency of 5.7 GHz. We describe in detail the applied algorithms and perform a tracking performance evaluation based on artificial channels and on measurement data from a tunnel scenario. The tracking performance of the proposed algorithm is comparable to the tracking performance of the state-of-the-art Gaussian mixture probability hypothesis density filter but with a significantly lower complexity. The fluctuation of the measured channel gain is followed very well by the proposed tracking algorithm, with a power loss of only 2.5 dB. We present statistical distributions for the number of MPCs and the birth/death rate. The applied algorithms and tracking results can be used to enhance the development of geometry-based channel models