Mohamed Ghorbel

Fully integrated CMOS data and clock recovery for wireless biomedical implants

In order to minimize the size and improve the efficiency of power consumption, most of wireless implantable Microsystems use Amplitude Shift Keying (ASK) modulator to transmit, through a RF link, data and energy to the internal implants. In this paper, we propose a new structure of wireless data and clock recovery dedicated for biomedical implants. It consists in a fully integrated ASK demodulator unit and a digital Manchester decoder. The demodulator is based on active components instead of the passive elements, as resistance or capacitance, to extract a robust data with a low modulation index. The whole digital Manchester decoder intends to recover data and clock from the demodulated signal. The following design has been validated by CADENCE environment using Specter simulation in a standard AMS 0.35μm CMOS process. The data rate is simulated by 1Mbps speed for 10MHz carrier frequency and 20% modulation index.

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).

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 wireless data and power recovery for biomedical Microsystems implants

In this paper we present a wireless data and power recovery for biomedical Microsystems implants. Most current systems use discrete components to achieve the back telemetry data and power supply. In order to achieve efficient power consumption and a minimum size of the implant, our RF powering system and data is conceived with MOS transistors in order to have a fully integrated system. Using the signal recovered by the inductive link, the system generates a regulated 3.3V voltage. A novel wireless data and clock recovery architecture is proposed. It consists on a fully integrated noncoherent ASK demodulator unit and a digital Manchester decoder circuit. The demodulator is based on an active component instead of the passive elements, i.e. R or C. This architecture allows data extraction robustness and a low modulation index. The all digital Manchester decoder is designed to recover data and clock from the demodulator output signal. The architecture presented in this paper has been validated by CADENCE simulation software using a standard AMS 0.35μm CMOS technology. Simulations show that the demodulator can be handled at 1Mbps with 10-MHz carrier frequency and 20% modulation index.

A dual band wireless power and DPSK data telemetry for biomedical implants

A performed dual band telemetry system with a DPSK data modulation scheme is reported for inductively powered biomedical implants. The innovation of this system consists on improving data rates with a novel full digital DPSK demodulator that achieves a data-rate-to-carrier-frequency ratio of 100% and a power consumption of 136.3μW @ 3.3 V at a data transmission rate of 10 Mbps. The whole receiver was designed with the 0.35-μm CMOS technology of Austria Micro Systems.

CMOS RF powering system for cochlear implant

In this paper we present a wireless RF powering system dedicated to a cochlear implant. Most current systems use discrete components to achieve the back telemetry power supply. In order to achieve an efficient power consumption and a minimum size of the implant, our RF powering system is conceived with MOS transistors in order to have an integrated system. Using the signal recovered by the inductive link, the system generates a regulated 3.3 V voltage which is used to generate power supply for the entire implanted device. The system is designed in AMS 0.35µm standard 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.

Spatial filtering based speech enhancement for binaural hearing aid

This paper investigates a new two-microphone array processing technique specifically for the purpose of speech enhancement in binaural cochlear implant. The main objective of the proposed technique is to improve the low frequency directivity of a conventional sum and delay Beamformer without using a Generalized Lobe Canceller, as low frequency performance is critical in speech processing applications. The proposed Beamformer algorithm based speech enhancement allows receiving a speech signal radiating from a specific direction and attenuating the signals from the other direction. Indeed, the localization of the speech target is defined, especially, with two cues of the speech signal received by the both ears: The Interaural Intensity Difference (IID) and the Interaural Time Difference (ITD). Adapting these parameters allows not only better localization of the interest direction of the speech and noise component but enhancing the signal-to-noise ratio also.