Alain Fabre

New high-value floating controlled resistor in CMOS technology

A new implementation of a floating controlled resistor in CMOS technology is introduced. The proposed circuit uses two second-generation current-controlled conveyors. With a supply voltage of plusmn3.3 V and a null load resistor, the simulated results show that the equivalent resistance decreases from 24.2 to 7.8 kOmega when the bias current is varied from 20 to 200 muA. Implemented in an industrial 0.8-mum CMOS process, its frequency response is up to 115 MHz for a bias current of 100 muA. For a load resistor of 10 kOmega and with the same conditions, the equivalent resistance varies from 93.3 to 60.2 kOmega

Cognitive and encrypted communications, part 2 : A new approach to active frequency-agile filters and validation results for an agile bandpass yopology in SiGe-BiCMOS

A new theory for a 2nd-order frequency-agile filter is introduced in this paper. The center frequency of the filter is proportional to the gain of a feedback amplifier and thus can be tuned over a wide frequency range. This new theory is thereafter generalized to the nth-class leading to a center frequency proportional to (A)n/2. The resulting filters make use of the minimum passive elements for 2nd-order filters: two capacitors. Simulation results of band pass agile filters in current mode and made from second-generation current controlled conveyors (CCCIIQ) in 0.25¿m SiGe BiCMOS technology are given for n=1 and n=2. These simulation results along with results of measurements carried out on the fabricated filters entirely confirm the new approach. They also highlight the improvements to be expected for cognitive and encrypted communications.

Cognitive and encrypted communications, Part 1 : State of the art for frequency-agile filters

Several communications techniques are currently being investigated: software radio, cognitive radio and encrypted communications are first of all presented in the first part of this paper. The second part makes the state of the art of research on agile and reconfigurable filters, passive as well as active, necessary for transceivers. Various tables for comparison are given.

A new 2 nd order variable-state filter: The frequency agile filter

This article presents a new second-order state variable filter including two amplifiers. The centre frequency of the resulting filter, f0, can be easily controlled using the gains of the amplifiers. This leads to a frequency-agile filter, whose centre frequency can be controlled over a wide range, without incidence on the power consumption. Simulation results given in this article confirm the new approach.

A new wideband fully-differential LNA with Matched Input And Output Impedances

The aim of this paper is to introduce a new differential LNA, based on current conveyors. This new LNA offers the following notable advantages over existent topologies: total absence of passive elements and thus it is now the smallest area differential LNA; wideband performances, with stable frequency responses from 0 to 3GHz and wideband matched input and output impedances; easy gain control over wide ranges (0 to 20dB). Comparisons with other topologies prove that the new implementation greatly advances the state of the art. This amplifier is ideally suited to todays multi-band receivers

A new class of fully active reconfigurable filters for cognitive communications

A new theory for a new class of fully active reconfigurable filters is introduced. These allow a wide tuning range for the center frequency by only modifying the gain of the feedback amplifier. Some simulation and measured results for a filter in a 0.25 μm SiGe BiCMOS technology that are given entirely confirm the validity of our new approach.