Jean Raphaël Olivier Fernández

Delay Spread and Electromagnetic Reverberation in Subway Tunnels and Stations

This letter presents an extensive campaign of wideband propagation measurements conducted in a modern subway environment in Madrid, Spain, at 980 and 2450 MHz. Measurements have been made using a channel sounder in a realistic environment of tunnel and station. Based on the measurement results, the principal parameters, such as mean power and delay spread, have been extracted for wideband propagation modeling. Furthermore, the results have been used to model electromagnetic reverberation, quality factor, and transition region between tunnel and station. The quantitative results provide a detailed wideband model of subway environment, as well as determine the design tradeoffs inside real tunnels and stations, in terms of optimal frequency band, antenna position, and expected multipath.

Planar Ultrawideband Antenna with Photonically Controlled Notched Bands

A design of a planar microstrip-fed ultrawideband (UWB) printed circular monopole antenna with optically controlled notched bands is presented. The proposed antenna is composed of a circular ultrawideband patch, with an etched T-shaped slot controlled by an integrated silicon switch. The slot modifies the frequency response of the antenna suppressing 3.5–5 GHz band when the switch is in open state. The optical switch is controlled by a low-power near-infrared (808 nm) laser diode, which causes the change in the frequency response of the antenna generating a frequency notch. This solution could be expanded to include several notches in the antenna frequency response achieving a fully reconfigurable UWB antenna. The antenna could be remotely controlled at large distances using optical fiber. The prototype antenna has been fully characterized to verify these design concepts.

A high isolation series-shunt photoconductive switching circuit

This paper presents a wide band compact high isolation silicon switching circuit, which is based on the series-shunt switch design with three silicon switches made of diced high resistivity silicon wafer placed over a microstrip gap and activated by 808nm near-infrared laser diodes. The switch shows an insertion loss of 1.2 dB and an isolation of 44.8 dB at 2 GHz.

A planar ultrawideband antenna with photonically controlled notched bands

In this paper a design of a planar ultrawideband antenna with photonically controlled notched bands is presented. The design is based on the patch with a partial ground plane, with an etched T-shaped slot and integrated silicon switch. The switch is activated by a near-infrared laser diode, which causes the change in a band notch of the antenna.

Gbps data transmission in biomedical and communications instruments

The paper proposes a distribution network for Gbps data transmission over. The study is based on a real design made for data communications of an aerospace instrument. This type of transmissions presents problems based principally on crosstalk and attenuation, therefore a careful design of distribution network and an adjustment of terminal loads are very important. A frequency scaled prototype at 20Mbps has been designed and tested, obtaining models of the complete circuit, crosstalk and interferences between near buses. Then a new design has been proposed to be used up to 8Gbps. On this design, the wired distribution network is based on the use of broadband couplers and low-loss transmission lines. Finally, possible aspects will be analyzed, as it was done in the Transmission/Reception System, such as the crosstalk or interferences between near buses and the possible introduction of some mechanism of protection.

High-resolution radar calibration system

In this work, we present a study of the frequency calibration system used to characterize the precision of the current and future radars. First, a general vision of the system is given. Moreover, basic procedures are explained to calibrate Doppler radars. Later, different architectures are presented, depending on the estimated parameters: speed and distance. Finally, a practical calibration system is presented, where the system precision is the most important factor. This system is able to simulate objects that move away at high speed (targets reach several Mach numbers).