Doppler Spectrum Measurement Platform for Narrowband V2V Channels

This paper describes the implementation of a Doppler spectrum measurement platform for narrowband frequency-dispersive vehicle-to-vehicle (V2V) channels. The platform is based on a continuous-wave (CW) channel sounding approach widely used for path-loss and large-scale fading measurements, but whose effectiveness to measure the Doppler spectrum of V2V channels is not equally known. This channel sounding method is implemented using general-purpose hardware in a configuration that is easy to replicate and that enables a partial characterization of frequency-dispersive V2V channels at a fraction of the cost of a dedicated channel sounder. The platform was assessed in a series of field experiments that collected empirical data of the instantaneous Doppler spectrum, the mean Doppler shift, the Doppler spread, the path-loss profile, and the large-scale fading distribution of V2V channels under realistic driving conditions. These experiments were conducted in a highway scenario near San Luis Potosí, México, at two different carrier frequencies, one at 760MHz and the other at 2,500MHz. The transmitting and receiving vehicles were moving in the same direction at varying speeds, ranging from 20 to 130km/h and dictated by the unpredictable traffic conditions. The obtained results demonstrate that the presented measurement platform enables the spectral characterization of narrowband V2V channels and the identification of their Doppler signatures in relevant road-safety scenarios, such as those involving overtaking maneuvers and rapid vehicles approaching the transmitter and receiver in the opposite direction.

*Published in the IEEE Vehicular Society Section within IEEE Access.

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Meandering Pattern 433 MHz Antennas for Ingestible Capsules

A number of design challenges are associated with in-body devices, especially ingestible capsules, including selection of operation frequency and antenna design. Operation frequency, miniaturization, gain, and interference with the environment and the internal components of ingestible capsules are all challenging factors. In this work, we design and measure the performance of miniature antennas that can be included in ingestible capsules. The meandering pattern designs are implemented with a 433 MHz center frequency which is within one of the industrial, scientific and medical (ISM) bands. The antenna patterns are rolled into cylinders to reflect their configuration inside a capsule. The effects of different antenna design features, environmental dielectric changes, and the battery locations relative to the antenna traces are explored. We show that the optimized antenna can offer acceptable performance even when the center frequency shifts due to the modulation of the dielectric constant of the media and by the insertion of batteries. Both simulations and measurements provide insight into how the meandering antenna should be designed for the desired frequency that can be expanded to other ingestible and implantable systems.

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