Frédérique Deshours

New Nonlinear Electrical Modeling of High-Speed Electroabsorption Modulators for 40 Gb/s Optical Networks

A specific modeling method is investigated in order to predict the large-signal modulation behavior of integrated electroabsorption modulators (EAMs) for high-speed applications in optical networks. The equivalent dynamic model includes the main nonlinearity of the EAM and takes into account the electrical and optical characteristics of the optoelectronic device. The developed specific design process is a suitable and powerful tool for simulating over wide dc bias and frequency ranges, scattering parameters, small-signal modulation response, and large-signal eye-diagram performance. Moreover, 3-D electromagnetic simulations are associated with circuit simulations to carry out for the RF input line of the EAM. This simulation model can be easily integrated in a global optical communication system simulator to estimate the temporal behavior of the modulated output optical power and then digital performances.

Performance Assessment of IR-UWB Body Area Network (BAN) Based on IEEE 802.15.6 Standard

Performance of impulse radio-based ultrawideband (IR-UWB) communications in wireless body area networks is investigated using the dedicated IEEE 802.15.6 standard. An IR-UWB transceiver system is implemented for both on-off keying and differential binary phase-shift keying modulations. Bit error rates are determined from measurements for different on-body links with different data rates. It is shown that using a 25-dB-gain low noise amplifier (LNA) at the receiver, reaching an uncoded bit error rate BER of 10-3 was not possible for some links operating at higher data rates. Power and energy consumption issues are then addressed, and results in terms of required pJ/bit to achieve a certain quality of communication are given and discussed.

GaAs monocycle pulse generator for UWB applications

This paper reports the design and test of a wavelet generator circuit which provides ultra short monocycle pulses of about 300 ps width alternately in phase and out of phase. This generator circuit is based on the representation of the pulse as a mathematical function which is a combination of four hyperbolic tangents. The final circuit of the generator was designed and realized on a monolithic microwave integrated circuit (MMIC) GaAs technology based on a pseudomorphic heterojunction FET (PHEMT) having a gate length of 0.25 mum (PH25 of UMS foundry).

Direct and external modulation of IF over fiber systems for 60 GHz wireless applications

Wireless domestic applications involving high data rates are required to work on millimeter wave band. Signal propagation at this frequency range is affected by walls and oxygen absorption which limits communication distances to few meters in one room. Radio coverage can be extended to other rooms by optical links. Performances of such photonic systems are dependent on optoelectronic devices, electrical driving, and receiver circuits. In this paper, radio-over-fiber (RoF) links based on the intensity modulation and direct detection technique are investigated for transmission of a broadband OFDM signal. Direct and external modulations are exploited to analyze system performances according to the ultra wideband (UWB) millimeter-band standard. To avoid component tolerances at high frequencies, an intermediate frequency modulation of the optical transducers is chosen. Optoelectronic and optical components of RoF links are modeled by equivalent electrical circuits with consideration of noise and nonlinearities. These models are validated in system simulation by error vector magnitude evaluation with a measurement setup according to the UWB centimeter-band standard.

Optical Transimpedance Receiver for High Data Transmission in OFDM Modulation Format

This paper presents the design and performance of a single-ended transimpedance amplifier (TIA) for gigabit passive optical networks implementing orthogonal frequency division multiplexing modulation format. The circuit is realized using an industrial GaAs integrated technology. Low power consumption and small chip area are the main challenges in the TIA design. On-wafer characterization in terms of S-parameters, noise figure, gain compression, and intermodulation are presented and compared to simulated results showing a good agreement. The TIA is linked with a broadband PIN photodiode and introduced in a radio over fiber system. The optical link is simulated in a microwave software and characterized in terms of error vector magnitude by varying the radio frequency input power and the laser bias current.

A 40 Gbps electro-absorption modulator integrated laser modeling method for optical transmitter in ultra-wide band radio-over-fiber systems

The great interest of optical fiber links in communicating systems especially in ultra-wide band (UWB) communications has grown up in the last decade and requires co-simulation for mixed circuits design exploiting both optical and microwave domains. In this paper, we report an original modeling method of an electro-absorption modulator associated with a distributed-feedback laser to simulate an optical transmitter of an UWB over fiber system. Large signal optoelectronic device models can be developed and implemented in a high-frequency simulator, such as advanced design system-Ptolemy to analyze the performances of fiber radio links and study the impact of the transmitter characteristics. This specific simulation way, taking into account precisely electrical characteristics of both electrical and optical circuits, links two different frequency domains by coupling electrical and optical modules in the same system simulator. Therefore, a complete simulation of an UWB multi-band orthogonal frequency division multiplexing signal transmission over fiber with an external modulator is investigated.

A 60 GHz Radio-over-Fiber architecture for the transmission of UWB-OFDM signals

This paper presents an original 60 GHz architecture for ultra-wide band (UWB) radio-over-fiber (RoF) systems to increase both the transmission distance and the high data bit rate. With a central station (CS) and a base station (BS), this architecture allows to send through an optical fiber both a subcarrier microwave signal and UWB baseband data by using a wavelength multiplexer. At the BS, the carrier frequency is photodetected, modulated by data and then up-converted to millimeter-wave band. Simulation results using VPIsystems software are reported and discussed for multi-band orthogonal frequency division multiplexing (MB-OFDM) signals.

Biosensor miniaturization for non-invasive measurements of materials and biological tissues

This paper presents about non-invasive planar complementary split ring resonators (CSRRs) coupled to microstrip line to measure the dielectric properties of materials and biological tissues. The expectations of health professionals are increasingly turning to less invasive surgical procedures and treatments. In particular, the monitoring of vital parameters (sweat, water in the lungs, etc.) or the evolution of certain pathologies, such as cancer cells, could be observed regularly if suitable devices were developed and could especially replace traditional invasive method. Appropriate miniaturized RF or microwave devices could be an alternative for some medical diagnostic applications. These devices would make it possible to determine the dielectric characteristics of biological tissues, which represent their real pathological states. Thus, it would be possible that dielectric contrast measurements will be able to follow the evolution of pathology, as well as the vital parameters of a patient. The objective of this research is to investigate a prototype biosensor that is suitable for measurements on biological tissues and can be miniaturized to enhance its spatial sensitivity. This work focuses on the design, electromagnetic simulations, and characterization of a new miniaturized biosensor at 2.4 GHz. The ex-vivo experimental results will be shown by measuring the S-parameters of various materials and animal biological tissues. The extraction of the dielectric parameters of these samples is obtained by the measurements of materials.

60 GHz stepped impedance filter using Planar Goubau line technology

This paper presents a fifth order stepped impedance low-pass filter using low loss Planar Goubau Line (PGL) technology on high resistivity Silicon substrate at millimeter-wave frequencies. The filter is simulated and optimized using 3D full-wave electromagnetic field simulations performed on HFSS (High Frequency Simulator Structure). On-wafer measurements in the 50–65 GHz band are in good agreement with simulation results. At 60 GHz, the measured insertion loss is 3.6dB which includes the two coplanar waveguide-to-GPL transitions.

Coplanar-Pgl Transitions on High Resistivity Silicon Substrate in the 57-64 GHz Band and Influence of the Probe Station on the Performances

We present Coplanar-Planar Goubau Line (PGL) transitions designed on high-resistivity Silicon to characterize a PGL using microwave probing. These transitions are optimized in the 57{ 64GHz frequency band to present excellent electrical performances despite the fleld disturbance of the measurement setup. As the transitions are positioned on a probe station chuck, a glass substrate is added between the transition under test and the metallic chuck to minimize the disturbance. 3-D full- wave electromagnetic fleld simulations performed on a commercial software and on-wafer measurements show almost comparable results in term of scattering matrix parameters. Low losses are attained with a measured average transmission parameter of 2.5dB at 60GHz for a length of 8mm of a back-to-back structure with the transitions at the extremities. The measured average insertion loss and return loss per transition are better than 1.36dB and 11dB, respectively, with a bandwidth greater than 7% at 60GHz for a length of 1mm (about a half of the wavelength at 60GHz).