Energy detection (ED) has been of interest for various applications ranging from very low frequency biomedical signal read-out to high frequency wireless communication. The analog implementation of the ED requires circuits with a non-linear transfer characteristics which can be obtained through squaring or rectification. Comparison of these two methods is presented and implementation limitations are detailed. Interesting characteristics of rectifiers, derived from ideal transfer characteristics and from non-ideal circuit implementations, encourage rectifier's use in the ED rather than the squarer. A high speed and high precision current mode full-wave rectifier was implemented in GF 22FDX technology. Our circuit achieves a 60 dB dynamic range and 100 MHz bandwidth with an ultra-low power consumption of 4.3 mu W from 0.8V voltage supply.

We designed, fabricated and tested an in-line portable moisture sensor for industrial applications, which comprises a sensor array that can detect the moisture content in plastic granulates at real time as well as all the necessary readout electronics for signal processing and communication. Measurement results performed with plastic pellets showed that the in-line portable moisture sensor can detect the moisture content with a precision of 100 ppm thus providing a very important control input, which is used to reduce the amount of energy consumed by industrial drying systems and also to enable added production time by avoiding the additional drying time caused by utilizing the fixed drying time recommended in the datasheet of the plastic granulate.

This paper presents a novel CMOS RF-to-DC converter for ultra-low-power wireless sensor nodes powered by RF wireless power transfer. The proposed converter achieves 10% higher power conversion efficiency than a conventional rectifier, with only a 1% increase in power consumption. The system employs a reconfigurable Dickson topology, operates on the unlicensed 868 MHz ISM band, and includes a built-in power-efficient MPPT system architecture. Experimental measurements show a maximum power conversion efficiency of 55% in the power range from −22 dBm to 0 dBm, with a power sensitivity of −22 dBm for a DC output voltage of 2.4 V. The proposed converter offers a promising solution for efficient wireless power transfer and energy harvesting in ultra-low-power wireless sensor nodes.

This letter presents the design of a 13.56 MHz offset‐enhanced full‐wave active rectifier, tailored for wirelessly powered biomedical implants. The design incorporates digitally assisted, delay‐compensated active diodes and symmetrical bulk biasing in the rectifier core to enhance conduction time, thus improving the voltage conversion ratio (VCR) and power conversion efficiency (PCE). A delay improvement is achieved both in no‐load and high‐load conditions through an additional comparison path with an offset voltage that is higher than zero. The proposed rectifier is implemented and fabricated in a 180 nm CMOS technology with an area of 0.024 . The rectifier, tested and measured with inductive links, offers a maximum VCR of 96.4% and a maximum PCE of 89%.

A new structure of low-power demodulator named “separated-Vb” amplitude shift keying (ASK) demodulator is proposed. The circuit is based on the switching behavior of the core digital shaper with different bias voltages, which improves its operation at low modulation indexes and reduces power consumption. This design does not require a comparator or Schmitt trigger, and only a few elements are needed which minimizes the chip area. The design is fabricated in the 0.18 μm CMOS process. The core chip area is 0.00144mm2, and the power consumption is 45 μW at a 1.8V power supply. The data rate can be nearly 2.7 Megabits per second (Mbps) at 13.56 MHz.

A novel area and energy efficient inductorless super-regenerative receiver (SRR) is proposed for medical brain implants dedicated to epilepsy monitoring and treatment. The proposed SRR was fabricated in UMC CMOS 180nm technology. The SRR occupies only 0.072mm 2 which corresponds to an order of magnitude area reduction compared to the state-of-the-art. The SRR achieves −70dBm sensitivity and the highest data rate is 4 Mbps. 3.22 nJ/b energy efficiency is obtained with 12.9mW power consumption from a 1.8V power supply.

This paper presents a wireless power conversion system designed for biomedical implants, with integrated automatic resonance tuning. The automatic tuning mechanism improves power transfer efficiency (PTE) by finely tuning the resonant frequency of the power link and maximizing the rectified voltage. This adjustment ensures robust and reliable remote powering, even in the face of environmental changes and process variations, while also minimizing tissue exposure to power. On-chip switched array capacitors are connected in parallel with the resonant capacitor, and the system identifies the optimal switched capacitor combination for the highest rectified voltage by iterating over each of them. The proposed system is implemented and fabricated in standard 180 nm CMOS technology, with a total area of 0.339mm2, and its operation is verified. The measurement results demonstrate that this system provides tolerance up to mismatches equivalent to 75 pF capacitance variation in LC tank, ±15% LC variation in this design. The system offers a PTE enhancement from 9.1% to 30.2% in case of high LC variation, and the tuning control consumes 154.7 μW of power during resonance tuning. Moreover, the power conversion chain delivers an optimized rectified voltage along with a regulated voltage of 1.8 V.

Energy efficiency is of utmost importance in modern applications. Power consumption optimisation could be improved by a comprehensive analytical modeling of the characteristics of critical blocks in a system. Dynamic range (DR) has a strong effect on the power consumption of analog circuits, and is determined by circuit non-linearity and noise level. Noise is well modelled even in deep sub-micron technologies, yet there is a lack of analysis and modeling of the non-linearity. An analytical MOSFET differential pair non-linearity model is presented in this work. The proposed model is universal to a wide range of technologies from long to ultra-deep sub-micron devices, and is valid for all operating regions as it is based on the EKV MOSFET model. Furthermore, a model including drain-voltage-induced non-linearity is also developed, and a concise 3 dB input intercept point (IIP3) formula incorporating the drain induced non-linearity in terms of the voltage gain is presented. The proposed models are validated with DC and AC simulations and measurements.

A wirelessly powered and data communication system is presented which is implemented as a full system, designed for multisite implanted biomedical applications. The system is capable of receiving wireless power and data communication for each implant separately, using inductive links with different resonance frequencies. To achieve this, dual-band coils are presented in the system. In addition, the system provides bi-directional data communication, utilizing amplitude and load shift keying (ASK and LSK) modulation schemes over a single inductive link. The system employs a digitally assisted active rectifier and an automatic resonance tuning system, to improve the power transfer efficiency (PTE) through various coupling coefficients, while minimizing the reverse current and power dissipation. The power control unit enables closed-loop monitoring to prevent high or low power delivery, and it can detect inefficient or excessive wireless power transmission or prevent temperature elevation by limiting the voltage to a safe level. A separated-V b ASK demodulator is presented in the paper which is utilized within the data conversion chain, serving both the external and implanted units. The whole system is fabricated using a standard 180-nm 1.8/3.3 V CMOS process with a core area of 0.82 mm 2 . The system is tested with coupled multisite inductive links and offers the maximum overall PTE of 31.2%, from the Tx coil to the implant load.

This paper presents the design of a 13.56 MHz full-wave active rectifier that utilizes digitally-assisted and delay compensated comparators for wirelessly powered biomedical implants. The proposed design employs delay compensation and digital assistance techniques to maximize the conduction time, resulting in improved voltage conversion ratio (VCR) and power conversion efficiency (PCE). The comparator speed is enhanced using an added latched structure. Also, a dynamic and symmetrical bulk biasing structure is employed in the rectifier core. The proposed rectifier design is implemented and fabricated using a 180nm CMOS process, with a chip area of 0.036m$\mathrm{m}^{2}$. Experimental measurements are carried out using inductive links resonating at 13.56 MHz, and the proposed rectifier design achieves a maximum VCR of 93% and PCE of 80.8% over a wide input voltage range from 1. 5V to 4V. These results demonstrate the effectiveness of the proposed design in achieving efficient power transfer for biomedical implants.

This article presents an implantable wireless system for remote hemodynamic monitoring, which enables direct, continuous (24/7), and simultaneous measurement of pulmonary arterial pressure (PAP) and cross-sectional area (CSA) of the artery. The implantable device, which measures 3.2 mm × 2 mm × 10 mm, comprises a piezoresistive pressure sensor, an ASIC implemented in 180-nm CMOS, a piezoelectric ultrasound (US) transducer, and a nitinol anchoring loop. An energy-efficient pressure monitoring system, which employs duty-cycling and spinning excitation technique, achieves 0.44 mmHg resolution in a pressure range from -135 mmHg to +135 mmHg and consumes 1.1 nJ conversion energy. The artery diameter monitoring system utilizes the inductive characteristic of the implant's anchoring loop and achieves 0.24 mm resolution within a diameter range of 20 mm to 30 mm, four times higher than echocardiography lateral resolution. The wireless US power and data platform enables simultaneous power and data transfer employing a single piezoelectric transducer in the implant. The system is characterized with an 8.5 cm tissue phantom and achieves a US link efficiency of 1.8%. The uplink data is transmitted by using an ASK modulation scheme parallel to the power transfer and achieves a modulation index of 26%. The implantable system is tested in an in-vitro experimental setup, which emulates the arterial blood flow, and accurately detects fast pressure peaks for systolic and diastolic pressure changes at both 1.28 MHz and 1.6 MHz US powering frequencies, with corresponding uplink data rates of 40 kbps and 50 kbps.

Power consumption is of utmost importance in portable devices as they are operated from a limited energy supply. Wireless radio is one of the most power-hungry blocks in these systems and needs to be activated opportunistically. Radio frequency (RF) spectrum sensing can be performed with a dedicated low power radio to control the main wireless radio. A low power receiver architecture is proposed in this work to monitor the 2.4GHz Industrial, Scientific, and Medical (ISM) band for communication standards such as Wireless Local Area Network (WLAN), Zonal Intercommunication Global-standard (ZigBee), and Bluetooth-Low-Energy (BLE). The whole ISM band is down-converted to zero-intermediate-frequency (ZIF) and a tunable base-band complex band-pass filter (CBPF) is used to scan the spectrum. A widely tunable first order ultra-low-power transconductor-capacitor (Gm-C) CBPF architecture was designed and fabricated in GF 22FDX technology, which occupies 0.0049mm 2 area. A frequency shift of ±60MHz was achieved with 5-40MHz bandwidth range. Power consumption ranges from 6.7 $\mu \text{W}$ to 99.2 $\mu \text{W}$ with the best and the worst figure-of-merit of 0.034fJ/pole and 0.082fJ/pole that is the energy consumption per pole normalized by the spurious free dynamic range.

Effective power management is crucial in designing wirelessly powered implants that have a long operational lifetime. It ensures that the received power is optimized for efficient operation and prevents damage caused by excessive or insufficient powering. This brief presents a power feedback control unit for wirelessly powered implanted biomedical devices, which includes an implanted voltage level detector and limiter. The feedback control bits can be transmitted through the link to the external unit as uplink data communication, or used to autonomously prevent overvoltage in worst-case scenarios. This design is implemented and fabricated in a 180nm CMOS process, which can be used for the power conversion chain of wirelessly powered biomedical implanted devices. The system consumes 144 $\mu \text{W}$ at a supply voltage of 1.8V and a chip area of 0.02255 mm2.

The design, fabrication and testing of a low-cost portable medical device for the detection and quantification of exosomes is presented in this paper. The portable medical device comprises a sensor array that can detect the presence of exosomes and quantify its concentration, a micro fluidic device that handles the human serum containing the exosomes, and all the necessary readout and control electronics. Measurement results performed with exosomes showed that the portable medical device can detect exosomes with a concentration of $2.5\mathrm{x}10^{8}/\mu \mathrm{L}$ thus paving the way to a wide range of diagnostic applications.

This paper introduces a dual-band inductive link designed to operate at both 6.78 and 13.56 MHz in the industrial, scientific, and medical (ISM) bands. The primary aim is to facilitate wireless power and data transmission in multisite biomedical implants. To mitigate magnetic interference between coils and reduce the occupied area, a single-coil transmitter configuration is employed in the proposed system. The study also investigates the advantages of employing different shapes of planar coils, such as square, circular, and octagonal topologies, in a dual-band power transmission setup. The presented system provides a reliable power supply for electronic circuits and supports downlink data communication. The inductive links are practically realized on printed circuit boards (PCBs), and the power and data circuits are fabricated using a 180-nm CMOS process. The proposed inductive link achieves a maximum coupling coefficient of 0.18 at a coil distance of 5 mm, along with a maximum power transfer efficiency (PTE) of 11.6% for the transmitter and receiver coils, which have outer dimensions of 43 mm and 13.5 mm, respectively. This setup showcases the feasibility and potential of the proposed dual-band inductive link for biomedical applications, offering a promising solution for efficient multisite power and data transfer in implantable devices.

This paper presents a wireless power and data conversion unit, designed to receive power and data via a single inductive link with a focus on applications in implanted biomedical devices. The system provides a reliable power supply for electronic circuits and supports bi-directional half-duplex data communication through frequency and load shift keying (FSK and LSK) modulation schemes. The wireless power and data transfer (WPDT) system utilizes a full-wave active rectifier operating at a frequency of 13.56 MHz, a bandgap voltage reference, and a 1.8 V low-dropout (LDO) voltage regulator to optimize the power supply for the electronic circuitry. The proposed data conversion unit is capable of demodulating data at a data rate of up to 1.35 Mbps. The proposed system is fabricated using a 180-nm 1.8/3.3 V CMOS process and occupies a total area of 0.305 mm 2 at the implant site. The system was evaluated with a coupled coil inductive link in testing.

Next-generation invasive neural interfaces require fully implantable wireless systems that can record from a large number of channels simultaneously. However, transferring the recorded data from the implant to an external receiver emerges as a significant challenge due to the high throughput. To address this challenge, this article presents a neural recording system-on-chip that achieves high resource and wireless bandwidth efficiency by employing on-chip feature extraction. Energy–area-efficient 10-bit 20-kS/s front end amplifies and digitizes the neural signals within the local field potential (LFP) and action potential (AP) bands. The raw data from each channel are decomposed into spectral features using a compressed Hadamard transform (CHT) processor. The selection of the features to be computed is tailored through a machine learning algorithm such that the overall data rate is reduced by 80% without compromising classification performance. Moreover, the CHT feature extractor allows waveform reconstruction on the receiver side for monitoring or additional post-processing. The proposed approach was validated through in vivo and off-line experiments. The prototype fabricated in 65-nm CMOS also includes wireless power and data receiver blocks to demonstrate the energy and area efficiency of the complete system. The overall signal chain consumes 2.6 $\mu \text{W}$ and occupies 0.021 mm2 per channel, pointing toward its feasibility for 1000-channel single-die neural recording systems.

This paper presents an energy-efficient, duty-cycled, and spinning excitation bridge-to-digital converter (BDC) designed for implantable pressure sensing systems. The circuit provides the measure of the pulmonary artery pressure that is particularly relevant for the monitoring of heart failure and pulmonary hypertension patients. The BDC is made of a piezoresistive pressure sensor and a readout integrated circuit (IC) that comprises an instrumentation amplifier (IA) followed by an analog-to-digital converter (ADC). The proposed design spins both the bridge excitation and the ADC’s sampling input voltages simultaneously and exploits duty cycling to reduce the static power consumption of the bridge sensor and IA while cancelling the IA’s offset and 1/f noise at the same time. The readout IC has been designed and fabricated in a standard 180-nm CMOS process and achieves 8.4 effective number of bits (ENOB) at 1 kHz sampling rate while drawing 0.53 $\mu$ A current from a 1.2 V supply. The BDC, built with the readout IC and a differential pressure sensor having 5 k $\Omega$ bridge resistances, achieves 0.44 mmHg resolution in a 270 mmHg pressure range at 1 ms conversion time. The current consumption of the bridge sensor by employing duty cycling is reduced by 99.8% thus becoming 0.39 $\mu$ A from a 1.2 V supply. The total conversion energy of the pressure sensing system is 1.1 nJ, and achieves a figure-of-merit (FoM) of 3.3 pJ/conversion, which both represent the state of the art.