Rim Barrak

Optic/RF co-design for oudoor RoF System at 60 GHz

Recent works have shown that optical access network is a promising approach for providing a broadband infrastructure at mm-wave but almost researches have study optical mm-wave link and radio stage architecture separately. In this study, we consider a complete RoF System and we investigate the link budget for optical and RF stage. We also design the wireless transceiver at 60 GHz.

Generalized Bandpass Sampling Algorithm for Multiband Wireless Receivers Suitable for SDR Applications

The bandpass sampling technique is a promising solution for the architecture of software-defined radio receivers. It is possible to digitize signals directly from the radio frequency stage when properly selecting the sampling frequency. With multistandard or multiband radio receivers, system nonlinearities mainly due to low noise amplifiers and downconversion circuits can generate rich output spectra with variable amplitude component levels. Bandpass sampling of such a spectrum, without causing aliasing, is a challenging task. For a nonlinear system, the minimum sampling frequency has been derived only for single-band and dual-band input signals. In this paper, a generalized bandpass sampling algorithm is developed to determine a minimum valid bandpass sampling frequency for either linear or nonlinear systems by considering a multiband input spectrum. Our objective is reducing the complexity of the sampling frequency calculation. Implementation results demonstrate the efficiency and low complexity of the proposed algorithm.

Software Defined Networking for cognitive Radio over Fiber systems

In this paper a novel cognitive Radio over Fiber (RoF) system lined up with Software Defined Networking (SDN) requirements is presented. First, the SDN paradigm for the proposed hybrid RoF system with centralized topology is developed. Then, cognitive process enabling self-aware RoF network is outlined. The goal is to allow traffic and network supervision and enable whole system intelligent management. In particular, we have defined the optical and radio sensing parameters, the required network controllers and the adaptation parameters. To highlight the impact of cognitive processing and the ability of the control plane to enhance the RoF network performances, some test scenarios are investigated.

LMS-based digital pre-equalizer for cognitive RoF system

The development of reconfigurable and high throughput architectures is the utmost target for researchers in the field of Radio over Fiber (RoF). In this paper, we developed a cognitive radio over fiber system lined up with Software Defined Networking owing to improve the quality of transport using a pre-equalization technique. The pre-equalization technique is based on Least Mean Square (LMS) algorithm. It is used to compensate the optical link performance degradation in the RoF system. The simulation results of the overall Bit Error Rate (BER) and the Q factor attest of high system performance improvement.

Varactors nonlinear effects in tunable RF filters

Varactor-based tunable bandpass filters are challenging solutions for next generation mobile phones that allow using one RF front-end for multiple applications. However, these solutions suffer from varactors non-linear effects that may affect signal quality and may introduce important distortions. This paper presents a thorough study of varactors nonlinear effects and some solutions for their cancellation. These solutions are applied in tunable Dual Behavior Resonator (DBR) bandpass filter to reduce non-linear distortions. S-parameter and Harmonic balance simulations were conducted to study and compare the performances of the solutions reported in the literature.

A multistandard and multiservice Radio over Fiber system for Next Generation Networks

Next generation Optical Networks become a topical issue that requires much researchers interest especially the improvement of last miles of the optical networks (access network). Radio over fiber technology fulfills with heterodyne optical networks needs since it answers to wideband applications requirements and meets high capacities networks. The association of RoF systems and futuristic optical access networks provides flexible high capacities networks. In this paper, we propose a RoF system architecture able to support muli-service (WiFi, WiMAX and mm-wave), multi-band (2.4, 5.2 and 60 GHz), multi-modulation schemas (BPSK, QPSK and 16QAM) and multi-data rates up to 5 Gbps. The selected transmission technique and service will depend on cell capacities, applications requirements and mobile user concentration. To validate the RoF system performances, we have simulated mm-wave Error Vector Magnitude (EVM) and constellation for different services.

Multiband GNSS receiver design, simulation and experimental characterization

The nonlinearity is an important factor that limit the improvement of the overall performance of a GNSS receiver. In order to prove the subsampling GNSS receiver performance for a weak desired system, a simple method is to characterize the derivation in nonlinearity and to quantify the impact on the wanted signal.

Design of a triband microstrip filter for GPS receiver

Global Navigation Satellite System (GNSS) receivers provide users with positioning, velocity and time. These receivers have to work with different standards and frequency bands in order to enhance the precision and the robustness. A multiband GNSS terminal with a single RF front-end would be a beneficial and cost-effective solution that allows the combination of more than two bands. The RF filter is an important component in the radio receiver. In this paper, we focus on the design of a tri-band filter operating at the three frequency bands (L5, L2, L1) of the GPS standard. The filter schematic is based on the half-wavelength bandpass topology with crossed open stubs. S parameters simulations show good agreement between the filter response and the standard specifications in terms of center frequencies and bandwidths.

A tunable RF filter for multistandard GSM/UMTS/WiFi/LTE receiver

The tunable RF filters are considered as a promising solution which can be implemented in the front-end RF of Software Defined Radio (SDR) receivers to make them suitable for multistandard wireless applications in a cost-effective and power-efficient way. In this paper, a tunable RF filter based on Dual-Behaviour Resonators (DBR) topology and excited by varactors as tuning components is presented. This filter is designed to operate in next generation transceivers using GSM, UMTS, Wi-Fi and LTE wireless standards. Special attention will be paid to the varactor model and its impact on the filter performance. S parameters simulations show a good agreement with the standards specifications in terms of center frequencies and bandwidths.

New technique to design tunable quarter-wave lengt side coupled ring filters for multistandards operation

As an important key of Software Defined Radio (SDR) receivers, tunable filters field knows a continuous and a rapid growth to resolve some handicaps in performance like electrical specifications and physical properties, especially in weight and size. In this context, a tunable RF filter is proposed. It is based on the quarter-wave length side coupled ring topology and varactors as tuning elements. The filter is implemented on FR4 substrate. This filter covers four wireless bands: GSM, UMTS, Wi-Fi and LTE Band 7. S parameters simulations show a quite good agreement in terms of electrical specifications.