Mounir Samet

Conception of an emitter for transcutaneous power and high-speed data transmission

In this paper, we present an emitter conception for radiofrequency transmitter system dedicated to cochlear prosthesis apparatus. The main function of this system is to allow a transcutaneous power and data transmission from an external part, the digital speech processor, to an internal part, the implant. Radiofrequency transmission was assured by an inductive link including two coils that are located on either side of the skin. The operating frequency should be around 12 MHz in order to minimize power absorption (in any other case between 10 and 20 MHz). In such transmission mode used for this apparatus, speech would be processed numerically and converted to pulse train which would be transmitted until the inner ear. Hence, our purpose was the conception of a data external emitter stage located in the external part, the speech processor. Emitter module has been conceived around a numeric control unit based on DE amplifier class and using a CP/spl I.bar/FSK modulator (continuous phase frequency shift keying). Numeric control unit included a Manchester encoder operating with a VCO (voltage controller output). We optimized our conception by using CMOS 0.35/spl mu/m technology for the conception of the different modules.

The RF circuit design for magnetic power transmission dedicated to cochlear prosthesis

Wireless remote powering of implants is usually achieved with a transcutanous link. Such a link consists of two resonant circuits, an external transmitter and an implanted receiver. The inductances are realised by two coils, facing each other. The radiated power received by a small coil in implantable telemetry systems must not exceed a few ten of milliwatts to avoid the damage of the biological tissue. This requires a very efficient RF to DC converter, as well as the lowest possible power consumption for the biomedical sensor and data acquisition/transmission system. This paper describes the design of a CMOS 0.35 mu integrated circuit that includes a numeric control unit, a DE amplifier class, a voltage doubler/rectifier, as well as a low power voltage regulator. Numeric control unit included a Manchester encoder operating with a VCO (voltage controller output).

Design and optimization of CMOS OTA with gm/Id methodology using EKV model for RF frequency synthesizer application.

In this paper, we will focus exclusively in the obtention of optimum power designs, using the (gm/ID) methodology. The introduction of a simple, gain bandwidth driven, automatic design algorithm for OTA is used as a starting point for the review of more advanced design methodology. This review leads to an automatic synthesis algorithm developed in MATLAB which systematically transits from high level specifications (total settling time) to the amplifier specifications (gain-bandwidth, slew rate) and then to transistor sizing. The design obtained complies with the high level specifications with minimum power consumption. Two main lines of study are followed here. The study of architectures for input and output stages that are suitable to be used on different environmental conditions, allow us to obtain an opamp cell that can be used in an ample spectrum of low-voltage, micropower applications. The second line of study in analog design reuse focuses on the possibility of circuit performance tuning through the bias current, where preliminary results have already been obtained . The idea in this technique is to tune the power-speed trade off of the opamp cell using the bias current while keeping the performance in all other aspects.

Programmable current source dedicated to a cochlear implant

In this paper, a novel architecture of a programmable current-source based on miniaturized digital-to-analog converters (DAC) was proposed. Such new design would be dedicated to cochlear implant circuit. In this study, our main objective was to look for one model that could include, as close as possible, several criteria related to the implant functionality such as reliability, flexibility, energy efficiency and integration area. Hence, this 6-bit DAC architecture was conceived in order to be adequate for a programmable current-source. Our design was able to generate a 2mA maximum current through a 1K/spl Omega/ load, which is around the typical nerve impedance. Simulation results showed good linearity, low power consumption and a low area occupation. Resulting circuit was simulated by PSPICE tool using the 0.35/spl mu/m CMOS technology.

A 10-bit CMOS programmable current-source dedicated for a cochlear implant

This paper presents a 10-bit programmable biphasic current-source, which is based on a digital to analog converter (DAC). In order to achieve high accuracy, a current-cell matrix configuration and a switching sequence in a code thermometer have introduced. To minimise the area of the DAC, a two matrix of a same current-cell are used. In this case an only 62 same current-cell are used instead to 1023 for a 10-bit thermometer-code-based DAC architecture. The simulation results have shown that the differential and the integral linearity errors are respectively 0.21 LSB and 0.35 LSB. The biphasic current sources present a good linearity and are capable of generating a maximum current of 1.050 mA through a 1 K/spl Omega/ load, which is around the typical nerve impedance. This device is designed in a 0.35-/spl mu/m CMOS technology. The maximum power consumption is 38 mW and the chip size is 175/spl times/290 /spl mu/m/sup 2/.

Wavelet transform based strategy for cochlear implant in real time implementation

A real time implementation of the wavelet transform (WT) approach on DSP platforms for a cochlear implant (CI) stimulation strategy is presented in this paper. The cochlear implant converts sounds which are received from the outside, into electrical pulses that stimulate nerve endings in the cochlea. These electrical stimuli are interpreted by the brain as sounds. For real-time experiment, it is crucial that the speech signal be processed with minimal delay from input to output. Thanks to different optimization steps, we have been able to reduce the processing time to approximately 10.5 μs on a 720MHz TMS320C6416 DSP board. This experiment provides directive guidelines for our work to treat the speech signal sample per sample at real time operation.

A programmable 9-bit current sources design dedicated to cochlear implant

This paper presents a programmable 9-bits current source design for micro-stimulator dedicated to cochlear implant. Such architecture requires a current source permitting to generate bidirectional current multiform. Besides, thanks to a programmable module, flexibility was provided in stimulus generation. In fact, the hearing threshold could be determined, using 3-bits DAC in order to fix the maximum comfortable stimulation, then the stimulation current pulses could be controlled in amplitude, using a 6-bits thermometer DAC, as well as in width. These parameters permit to modulate the charge quantity to be injected later in the cochlea nerve endings. The current sources of the 6-bits DAC have been sized to guaranty low power consumption, a low silicon occupation and an INL of less than 0.4 LSB and a DNL of less than 0.08 LSB. The maximum output providing is about 1 mA of full scale current at each output from 3.3 V supply, when the output is terminated on 1 KOmega loads.

Electronic conception of a programmable hearing aid

Hearing is the feeling thanks to which, the external world is perceived by the intermediary of specialized sensors, sensitive to the sound vibrations of the air (sound waves). These waves must pass by a whole perception and transmission chain including the outer ear, the middle ear and the inner ear, to arrive finally at the auditive nerve. At each level of this chain, an embarrassment or a rupture generating a situation whose severity can go from light auditive deficiency to major deficiency can be produced. So in the most cases, the port of a hearing aid becomes required. In this paper we are interested in the electronic design of a programmable hearing aid in 0.35 mum MOS technology.