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This paper reports on a novel solution for a transimpedance amplifier (TIA) specifically designed as an analog conditioning circuit for low-voltage, low-power, wearable, portable and implantable optoelectronic integrated sensor systems in biomedical applications. The growing use of sensors in all fields of industry, biomedicine, agriculture, environment analysis, workplace security and safety, needs the development of small sensors with a reduced number of electronic components to be easily integrated in the standard CMOS technology. Especially in biomedicine applications, reduced size sensor systems with small power consumption are of paramount importance to make them non-invasive, comfortable tools for patients to be continuously monitored even with personalized therapeutics and/or that can find autonomous level of life using prosthetics. The proposed new TIA architecture has been designed at transistor level in TSMC 0.18 μm standard CMOS technology with the aim to operate with nanoampere input pulsed currents that can be generated, for example, by Si photodiodes in optical sensor systems. The designed solution operates at 1.8 V single supply voltage with a maximum power consumption of about 36.1 μW and provides a high variable gain up to about 124 dBΩ (with fine- and coarse-tuning capabilities) showing wide bandwidth up to about 1.15 MHz and low-noise characteristics with a minimum noise floor level down to about 0.39 pA/Hz. The overall circuit is described in detail, and its main characteristics and performances have been analyzed by performing accurate post-layout simulations.

In this paper, we propose and validate a tactile sensory feedback system for prosthetic applications based on an optical communication link. The optical link features a low power and wide transmission bandwidth, which makes the feedback system suitable for a large number and variety of tactile sensors. The low-power transmission is derived from the employed UWB-based optical modulation technique. A system prototype, consisting of digital transmitter and receiver boards and acquisition circuits to interface 32 piezoelectric sensors, was implemented and experimentally tested. The system functionality was demonstrated by processing and transmitting data from the piezoelectric sensor at a 100 Mbps data rate through the optical link, measuring a communication energy consumption of 50 pJ/bit. The reported experimental results validate the functionality of the proposed sensory feedback system and demonstrate its real-time operation capabilities.

This paper reports on a CMOS fully integrated optoelectronic sensing system composed of a Si photodiode and a transimpedance amplifier acting as the electronic analog front-end for the conditioning of the photocurrent generated by the photodiode. The proposed device has been specifically designed and fabricated for wearable/portable/implantable biomedical applications. The massive employment of sensor systems in different industrial and medical fields requires the development of small sensing devices that, together with suitable electronic analog front ends, must be designed to be integrated into proper standard CMOS technologies. Concerning biomedical applications, these devices must be as small as possible, making them non-invasive, comfortable tools for patients and operating with a reduced supply voltage and power consumption. In this sense, optoelectronic solutions composed of a semiconductor light source and a photodiode fulfill these requirements while also ensuring high compatibility with biological tissues. The reported optoelectronic sensing system is implemented and fabricated in TSMC 180 nm integrated CMOS technology and combines a Si photodiode based on a PNP junction with a Si area of 0.01 mm2 and a transimpedance amplifier designed at a transistor level requiring a Si area of 0.002 mm2 capable to manage up to nanoampere input currents generated by the photodiode. The transimpedance amplifier is powered at a 1.8 V single supply showing a maximum power consumption of about 54 μW, providing a high transimpedance gain that is tunable up to 123 dBΩ with an associated bandwidth of about 500 kHz. The paper reports on both the working principle of the developed ASIC and the experimental measurements for its full electrical and optoelectronic characterizations. Moreover, as case-examples of biomedical applications, the proposed integrated sensing system has also been validated through the optical detection of emulated standard electrocardiography and photoplethysmography signal patterns.

This paper reports on the design, realization and characterization of a True Random Number Generator (TRNG) that operates using as seeds of entropy, the jitter and the metastability introduced by primitives of a Field Programmable Gate Arrays (FPGA) board. In particular, the TRNG architecture has been implemented on a Xilinx Ultrascale XCKU040 FPGA board. Generally, the implementations on FPGA of fully-digital TRNGs make use of ring oscillators employing a large number of Look-Up-Table (LUT) blocks. Differently from this approach, this paper demonstrates that a reliable FPGA-based TRNG architecture can be realized mainly employing only a single PLL and three on-board primitives together with other few basic logic elements (i.e., 8 D-type Flip-Flop, 17 LUT and 2 Counters) used only for the initial overall system synchronization and post-processing operations. In this way, the proposed solution largely reduces the employed number of the FPGA Configurable Logic Blocks (CLB), the circuitry complexity and the overall power consumption without affecting the achievable output bit rate so resulting suitable for full-custom VLSI implementations. The random and statistical properties of the generated 100 Mbps output bitstreams have been validated by passing all the National Institute of Standards and Technology (NIST) tests as well as the Anderson-Darling and the Kolmogorov-Smirnov tests so demonstrating that the proposed TRNG architecture can be suitably employed in security/cybersecurity network systems as well as, once integrated, in Internet-of-Things (IoT) and Industrial-Internet-of-Things (IIoT) applications.

Size and absolute concentration of suspensions of nanoparticles are important information for the study and development of new materials and products in different industrial applications spanning from biotechnology and pharmaceutics to food preparation and conservation. Laser Transmission Spectroscopy (LTS) is the only methodology able to measure nanoparticle size and concentration by performing a single measurement. In this paper we report on a new variable gain calibration procedure for LTS-based instruments allowing to decrease of an order of magnitude the experimental indetermination of the particle size respect to the conventional LTS based on the double ratio technique. The variable gain calibration procedure makes use of a specifically designed tunable-gain, dual-channel, dual-phase Lock-In Amplifier (LIA) whose input voltage signals are those ones generated by two Si photodiodes that measure the laser beam intensities passing through the sample containing the nanoparticles and a reference optical path. The LTS variable gain calibration procedure has been validated by firstly using a suspension of NIST standard polystyrene nanoparticles even 36 hours after the calibration procedure was accomplished. The paper reports in detail the LIA implementation describing the design methodologies and the electronic circuits. As a case example of the characterization of biological nanostructures, we demonstrate that a single LTS measurement allowed to determine size density distribution of a population of extracellular vesicles extracted from orange juice (25 nm in size) with the presence of their aggregates having a size of 340 nm and a concentration smaller than 3 orders of magnitude.

Here we report on a novel optoelectronic architecture capable to add in-phase the current pulses generated by each one of the fast Si photodiodes forming an array illuminated by laser pulses. The aim is to increase the total photodiode sensitive area to achieve higher output pulsed current values by maintaining unaltered the response time, the bandwidth and the reverse bias voltage proper of each single photodiode. This result is important for many modern applications in biophysics and biomedicine like the brain machine interfaces, that require real time evaluation of environmental/sample changes through the acquisition of signals at high data rates under high signal-to-noise ratio conditions. As a consequence, these applications use sub-nanosecond laser pulses that are revealed by large bandwidth photodiodes having small sensitive area to attain low values of the internal junction capacitance. Thus, any small optical misalignment between the laser beam and the photodiode sensitive area in transcutaneous optical biotelemetry strongly decreases the system detection efficiency and performances. The proposed optoelectronic system resolves this problem being capable to sum in-phase the current pulses generated by each one of the photodiodes forming the array into a single current pulse maintaining the condition of fast response in terms of rise and fall times and bandwidth. This solution employs a Kirchhoff node to sum the different photocurrents, a decoupling current buffer and a transimpedance amplifier to amplify the current pulses summed at the node. We investigated the performances of the optoelectronic system by using photodiodes with different sensitive areas and junction capacitances (i.e., different bandwidths and rise and fall times) for laser pulses repetition rates up to 200 MHz. We also experimentally characterized the circuitry composed by an array of 4 fast photodiodes by using 800 ps laser pulses at a repetition rate of 200 MHz proving that the achieved response times and bandwidth remain the same of those ones of each single photodiode. Moreover, we demonstrated that the maximum value (i.e., the peak) of the obtained output current pulses is multiplied by a factor 4, i.e., equal to the number of the photodiodes forming the array having an overall sensitive area enhanced by the same factor.

This demonstration presents the first implementation of “event-driven” serial asynchronous communication on optical fiber. “event-driven” communication is used by neuromorphic sensors, that sample the sensory signal when the signal itself changes of a given amount. This type of sensing adapts to the dynamics of the input itself, achieving at the same time extremely high temporal resolution (when needed), low latency and signal compression. To apply this technology in robotics, optical communication will greatly improve the resilience to electric disturbances.

In this paper we report on the fabrication, implementation and experimental characterization of an integrated bidirectional communication System-on-Chip (SoC) for transcutaneous bidirectional optical biotelemetry links. The proposed architecture implements a UWB-inspired pulsed coding technique and contains a transmitter and a receiver to achieve a simultaneous bidirectional link. The transmitter generates sub-nanosecond current pulses to directly drive off-chip pulsed vertical cavity semiconductor lasers by means of a digital data coding subsystem and all the needed bias and driving circuits. On the other hand, the receiver manages off-chip fast Si photodiodes and includes signal conditioning, detection and digital data decoding circuits to support high bit rate and energy efficient communication links. The entire solution designed at transistor level has been fabricated in AMS 0.35µm standard CMOS technology into a compact silicon footprint lower than 0.13mm2 employing only 113 transistors and 1 resistor. A specific PCB has been developed together with a suitable test bench implemented on Xilinx Virtex-6 XC6VLX240T FPGA board to properly evaluate the performances and the main characteristics of the ASIC. Furthermore, a 6 GHz, 20 GS/s LeCroy WaveMaster 8600A digital oscilloscope has been employed to investigate the system time response. Preliminary experimental results validated the correct functionality of the overall integrated system demonstrating also its capability to operate, also in a bidirectional mode, at bit rates up to 250 Mbps with pulse widths up to 1.2ns and a minimum total power efficiency of about 160 pJ/bit in the conditions for which the transmitter and the receiver work simultaneously onto the same chip. These results make the developed solution suitable for high performances bidirectional optical biotelemetry links to be applied, e.g., to implantable neural recording/stimulation transcutaneous platforms that generally require communication channels with high up- e down-link bit rates at extremely low energy levels.

In this paper we present an optoelectronic architecture based on a current-mode photodiode bridge readout circuit that performs differential measurements of the energy variations of nanosecond laser pulses. This operation is achieved by differentially detecting the currents photogenerated by two Si photodiodes one of which is used as the reference signal and the other measures the signal coming from variations of the laser pulse energy. The circuit has been designed for high-speed operations (i.e., large bandwidth) and its features can be simply optimised as a function of the laser pulse-width (e.g., in the nanosecond and subnanosecond regime) and of its repetition rate from few Hz up to few MHz. Moreover, the electronic circuitry allows to achieve the initial photodiode bridge balancing condition by variable control voltages so zeroing the overall interface offsets due to optical and electronic device mismatches and initial bridge unbalance conditions. The readout circuit has been fully characterised by performing both electrical and optical measurements and by varying its gain, detection sensitivity and energy-per-pulse changes between the signal and the reference employing 10ns laser pulses at a repetition rate of 20Hz. These measurements have been compared with those ones obtained using a standard commercial lock-in amplifier as the conditioning circuit under the same experimental conditions. The proposed optoelectronic architecture is able to reach a maximum detection sensitivity of 7m V/ fJ corresponding to a detection resolution of the laser pulse energy variations equal to 0.14×10−3 fJ. These results prove an increase of 1225 in the detection sensitivity and resolution obtained by employing a lock-in amplifier in a differential measurement configuration.

This paper describes an integrated communication system, implementing a UWB-inspired pulsed coding technique, for an optical transcutaneous biotelemetry. The system consists of both a transmitter and a receiver facilitating a bidirectional link. The transmitter includes a digital data coding circuit and is capable of generating sub-nanosecond current pulses and directly driving an off-chip semiconductor laser diode including all bias and drive circuits. The receiver includes an integrated compact PN-junction photodiode together with signal conditioning, de- tection and digital data decoding circuits to enable a high bit rate, energy efficient communication. The proposed solution has been implemented in a commercially available 0.35 μ m CMOS technology provided by AMS. The circuit core occupies a compact silicon footprint of less than 0.13 mm 2 (only 113 transistors and 1 resistor). Post-layout simulations have validated the overall system operation demonstrating the ability to operate at bit rates up to 500 Mbps with pulse widths of 300 ps with a total power efficiency (transmitter + receiver) lower than 74 pJ/bit. This makes the system ideally suited for demanding applications that require high bit rates at extremely low energy levels. One such application is implantable brain machine interfaces requiring high uplink bitrates to transmit recorded data externally through a transcutaneous communication channel.

This paper presents an optical communication system, implementing a UWB-inspired pulsed coding technique, for emerging high throughput bio-applications such as brain machine interfaces. The proposed solution employs sub-nanosecond laser pulses that, compared to the state-of-the-art, allows for high bit rate transmissions and reduced power consumption. The overall architecture consist of a transmitter and receiver that employ a pulsed semiconductor laser and a small sensitive area photodiode. This can allow for CMOS integration into a compact silicon footprint (estimated lower than 1 mm2 in a 0.18 μm technology). The analogue circuits presented herein have been implemented using discrete off-the-shelf components. These provide the bias and drive signals for laser pulse generation, photodiode signal detection and conditioning. Moreover, the digital sub-system for data coding and decoding processes have been implemented on a FPGA board through VHDL description language. Experimental results validate the overall functionality of the proposed system using a diffuser between transmitter and receiver to emulate skin/tissue. This shows the capability of operating at bit rates up to 250 Mbps achieving BER less than 10−9 and power efficiency as low as 24pJ/bit. These results enable, for example, the transmission of a 1000-channel neural recording system sampled at 16kHz with 16-bit resolution.

This article reports an implantable transcutaneous telemetry for a brain machine interface that uses a novel optical communication system to achieve a highly energy-efficient link. Based on an pulse-based coding scheme, the system uses sub-nanosecond laser pulses to achieve data rates up to 300 Mbps with relatively low power levels when compared to other methods of wireless communication. This has been implemented using a combination of discrete components (semiconductor laser and driver, fast-response Si photodiode and interface) integrated at board level together with reconfigurable logic (encoder, decoder and processing circuits implemented using Xilinx KCU105 board with Kintex UltraScale FPGA). Experimental validation has been performed using a tissue sample that achieves representative level of attenuation/scattering (porcine skin) in the optical path. Results reveal that the system can operate at data rates up to 300 Mbps with a bit error rate (BER) of less than 10 $^{-10}$ , and an energy efficiency of 37 pJ/bit. This can communicate, for example, 1,024 channels of broadband neural data sampled at 18 kHz, 16-bit with only 11 mW power consumption.

This paper reports on a pulsed coding technique based on optical Ultra-wideband (UWB) modulation for wireless implantable biotelemetry systems allowing for high data rate link whilst enabling significant power reduction compared to the state-of-the-art. This optical data coding approach is suitable for emerging biomedical applications like transcutaneous neural wireless communication systems. The overall architecture implementing this optical modulation technique employs sub-nanosecond pulsed laser as the data transmitter and small sensitive area photodiode as the data receiver. Moreover, it includes coding and decoding digital systems, biasing and driving analogue circuits for laser pulse generation and photodiode signal conditioning. The complete system has been implemented on Field-Programmable Gate Array (FPGA) and prototype Printed Circuit Board (PCB) with discrete off-the-shelf components. By inserting a diffuser between the transmitter and the receiver to emulate skin/tissue, the system is capable to achieve a 128 Mbps data rate with a bit error rate less than 10−9 and an estimated total power consumption of about 5 mW corresponding to a power efficiency of 35.9 pJ/bit. These results could allow, for example, the transmission of an 800-channel neural recording interface sampled at 16 kHz with 10-bit resolution.

We propose an optical UWB modulation based on a new pulsed coding technique for wireless implantable biotelemetry. The solution employs sub-nanosecond laser pulses allowing for both high data rates and reduction of the power consumption compared to the state-of-the-art. Thus, the proposed approach is suitable for upcoming biomedical systems like autonomous implantable neural devices. The developed architecture consists of a transmitter and a receiver employing a pulsed semiconductor laser and a small sensitive area photodiode, respectively, and includes coding and decoding digital systems, biasing and driving analogue circuits for laser pulse generation and photodiode signal conditioning. Experimental findings, obtained by employing discrete components prototype PCBs and FPGA implementations, validate the novel technique showing the capabilities to achieve a BER less than 10 -9 with data rates up to 250Mbps and an estimated power consumption lower than 5mW. These results enable, for example, the transmission of a 1000-channel neural recording system sampled at 16 kHz with 16-bit resolution.