Design and Implementation of High Performance PPSK demodulator in Biomedical Implant

The important challenge for the realization of hearing aids is small size, low cost, low power consumption and better performance, etc. Keeping these requirements in view this work concentrates on the VLSI (Very Large Scale Integrated) implementation of analog circuit that mimic the PPSK (Passive Phase Shift Keying) demodulator with low pass lter. This research deals with RF Cochlear implant circuits and their data transmission. A PPSK modulator is used for uplink data transmission in biomedical implants with simultaneous power, data transmission This paper deals about the implementation of PPSK demodulator with related circuits and low pass lter which are used in cochlear implants consumes low power and operates at 14MHz frequency. These circuits are designed using FINFET 20nm technology with 0.4v DC supply voltage. The performance of proposed design over the previous design is operating at low threshold voltage, reduces static leakage currents and often observed greater than 30 times of improvement in speed performance


Introduction
Many wireless medical implants [1] are speci cally used for prosthesis and diagnosis, functioned to mimic as regular body parts.In the eld of Pharmacy, designing of these implants requires miniaturization of technology & also component scaling.In general, implants are contrived from the skin, bone, tissues &materials-metal/plastic/ceramic, insertion of nanometer scaled (nm) implant and generation of ionic potential stimulus from injected electrode array inside the human body through these kinds of the implant is challenging task.The best HYPACUSIS treatment implant is COCHLEAR IMPLANT (CI) [2] helps to impetus the auditory nerve directly by stimulating hair cells of the EAR.However, VLSI advanced technologies like CNTFET, FINFET, TFET makes the scaling of channel width rather than CMOS, leading to certain parametric variations (Power, Delay & Area)  enclosed with external parts: microphone and speech processor.Highly designed CI requires 5-6 hours of surgery for stabilizing hearing sense & placing of Implant inside the ear.Fig. 4 describes the signal processing of CI from internal to external parts perfectly.As table.1 discusses contribution of inventor, especially for auditory neuro-stimulus and their functionalities [7].

Finfet Trends In Cochlear Implant
The scope of the electronics in CI, is to design the functioning circuits like speech processor, transmitter, etc., by using VLSI technology.The signal processing from the external source to the internal part of ear is perfectly prototype in Fig.5 [8].
Modern the major concern in the system design.Due to the lifetime limitation, the battery is not the optimal choice in the implanted device.In recent years, electromagnetic propagation through inductive coupling links is widely used to deliver power and information to these implantable systems.
These approaches can avoid the risk of causing infection and battery life problem.In general, implantable systems must satisfy the following requirements: 1) long-life time, 2) high reliability and 3) small size.The implanted device (bio-devices) senses the internal data (body) and converse with the external world by means of power and telemetry [15][16] Hence biotelemetry link is used as the bidirectional transmission between bio-device and external tool.
The process of data transmission between the bio-device and the tool is in the form of uplink and downlink.Sending of data from the implant to the external world is known as DOWNLINK and its inverse is termed as UPLINK.Bio-device consists of a sensor and a stimulator.The telemetry circuit implemented in CMOS technology for cochlear implant [15] is shown in Fig. 6.It is a surgical device, which senses audio signals from a hearing-impaired person.The device consists of a microphone placed outside the ear and an electrode array in the inner ear and skin act as an inductive link between the external and internal parts of the ear.Injecting the device in the exact position of the body takes 6 hours of surgery; however, it should be miniaturized and consume less power.

Proposed Telemetry Circuit for a Cochlear Implant
To achieve the desired characteristics of low cost, small size, low power implants, conventional CMOS implants are implemented with 20nm FINFET Technology [21][22][23].In this regard respect RF clock generator, Monostable multi-vibrator, PPSK demodulator are designed and implemented to meet the requirement of proposed model.

2.2.1.Monostable Multi-vibrator:
In the implant design, Monostable multi-vibrator is used as the timer to produce the data rate in user speci ed time.The proposed circuit is designed for driving large capacitive loads which are implemented using NMOS technology with less delay, number of stages, and the width value as shown in  For example from the generated output of Monostable circuit the change of number of bits from transmitted input (IN) 12Kbits to received output bits with error of 4 bits (V OUT ) is de ned as BER.So error bits are four divided by 12K transmitted bits.The error rate is 0.0000333.
The simulated waveform for M1 and M2 circuits is generated by FINFET 20 nm technology using the cadence tool by applying 0.4v.As per the transient analysis the settling time considered as 7ns for data transmission, consequently the frequency range is of 14MHz Table .1.The delay, dynamic power dissipation is calculated is shown in Table .2.From the waveform the capacitor C1 alters when FF-reset changes from 1 to 0 and Width from 0 to1, with reference to the time axis the generated output is ampli ed in accordance with the width and C1, and it is evident for the less propagation delay in signal transmission from the obtained results of Fig. 10.Modern CI Functional Block Diagram [8].
Page 14/16  Realization of monostable circuit using FINFET Technology Architecture of Active Low Pass Filter PPSK Demodulator.
Figure 10 Transient response of monostable (m1,m2) circuits accordingly.Designing of implants by incorporating mentioned technologies may enhance the productivity & performance.This research work deals with exploitation of COCHLEAR implant circuit designing in advanced VLSI technologies.Moore's law [3] sates for every couple of years, there is a doubling of transistor count on an integrated chip by scaling the technology as in Fig.1.Progressive efforts of researchers work from past decades originated a nanometer (nm) technology transistor known as FINFET; shorten the cons of CMOS technology.With FINFET [4] narrow channel dual gate structure of Fig.2.leakage current are lessen & deepen carrier mobility: without increasing doping concentration & require low operating voltage(~0.4v)subsequently condense power dissipation.In evidence to WHO recent proclamation [5] 488 million people complain of hearing disabilities for >40dB echo auditory signals, may affects more than 900 million people by 2025 because of environment conditions, noise pollution, etc., Settling to above strategy research inventors proposing certain medication facilities like arti cial implantation (CI) from early 1800 to till date by accommodating electrodes for designing purpose.CI uses 22 active platinum electrodes providing 11 channels as an array, with length of 17mm, each electrode isolation of <0.1mm & facilitates the biphasic electric stimulus to auditory nerve[6]and spiral ganglion nerve in Fig.3.Conventional CI contains internal parts: electrode array, transmitter & receiver /Stimulator (9.5 gm) 1. Speech Processor-receives acoustic signals via microphone 2. Transmitter-transmits the encoded audio signals to the internal receiver 3. Electrode array-receives transmitted impulses.4. Auditory nerve-The Electrode array electrically stimulates the auditory nerve.
Fig 7. NMOS inverters are used to amplify the speed and also reduce the transistor count.The two circuits (M1 and M2) parametric values are same, but the difference in capacitance C 1 (1:5) and the chirality value of width (2).Transistor level implementation of Monostable Circuit is shown in Fig 8.
transmitter side the PPSK demodulator is considered.Comparing with the other modulation techniques the e cient way for authorizing data is done by using PSK[24],[20].In the proposed circuit an active low pass lter in place of comparator is used to achieve good modulation by dragging su cient power to amplify the output signal with low noise as shown in Fig9.The rst order low pass lter is driven by resistor R and Capacitor C it only allows low frequency signals but attenuates the signals beyond the cut-off range.As the sine wave response is applied and it generates the triangular wave output by varying C either by charging or by discharging, hence it acts as an integrator.Chosen R, C (τ) values which are greater than the input time period.2.2.3.Calculation for Bit Error Rate (BER) of Monostable Circuit:

3. 2 .
PPSK Demodulator: PPSK demodulator is implemented with 0.4v supply voltage in 20 nm FINFET technology here V IN , V AMP , a low pass lter capacitor C are the inputs and V OUT is the output.The simulation results are shown below.It is observed in Fig 11.V OUT is dependent on the C which remains constant until capacitor charges and discharges and changes its phase for next cycle (V IN ). Figures

Figure 7 Block
Figure 7

Table 1 .
Invention Route-map of CI.
CI can be successfully progressed by applying a proper synchronized clock implemented in FINFET topology[9]that is in Radio Frequency (RF) range.All the medical devices are driven mostly in RF range for ensuring safety interconnect between internal and external parts, to transmit both power and data.Major sub block is Back telemetry pretend to monitor the internal unit, electrode unit conditions & neural responses.An ASIC chip with power ampli er [10], error frees decoder/demodulator[11]and Analog to Digital Converter (ADC) is integrated for internal feedback purpose.However, propagating the signal impulse in mv range into the body is crucial task.From the Era of Telephone by Graham Bell in the 18 th century, Electrophonic Perception of Stevens with his colleagues in the 19 th century, William's Gold Electrode implantable chip in the mid of 19 th century proven the audio-signal stimulates in deaf patient & prearranged the trail invention of hearing-aid implantable devices.Various implantable integrated analog circuits have been designed for numerous clinical applications such as cardiac pacemakers, cochlear implants , retinal prostheses, and functional neuromuscular stimulation (FNS) systems.These devices are active implants that require energy sources like solar, infrared & wireless energy transfer for functioning[12].In implanted system, the power [13] is The bio-signals are sensed by the sensor and the sensed data is transmitted to the doctors for diagnosis.Multi Stimulator [14] acts as a feedback element which tracks the status of the nerves and the implant.Taking it as a challenge the parts of implantable devices are designed the CMOS technology by considering all technical parametric issues [17].
and compared with existing technology.Based on the considerations, an analog PPSK demodulator communication module circuit is proposed in FINFET technology, because of its low doping concentration with good matching & better performance through proper voltage biasing.2.1.Conventional PPSK Demodulator

Table 2
Features Summary.
ConclusionIn this paper Monostable and RF Clock Generator are implemented for cochlear implant application in 20nm FINFET Technology.The existing comparator is replaced by an Active Low pass lter to achieve