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Detailed circuit schematic of the 2.4 GHz radio transmitter with integrated wireless energy receiver. High- switches are shown in green, and signals operating from the charge pump supply are shown in red with dash-dot lines.
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This paper presents the design of a narrowband transmitter and antenna system that achieves an average power consumption of 78 pW when operating at a duty-cycled data rate of 1 bps. Fabricated in a 0.18 µm CMOS process, the transmitter employs a direct-RF power oscillator topology where a loop antenna acts as a both a radiative and resonant element...
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... 13 mm of tissue was found to be 15.5 dB at an optimal frequency of 1.45 GHz, which is in line with previous work in this area [13]. At 2.4 GHz, the gain falls to 17.5 dB, an acceptable trade-off for not requiring re-tuning. IV. CIRCUIT DESIGN A transistor-level schematic of the transmitter and wireless energy receiver architecture is shown in Fig. 4. The following subsections describe the system operation, including details of each individual ...
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... simple fully-integrated testing, or can accept externally driven serial data (labeled as data in Fig. 7) for benchtop testing or eventual system integration with a sep- arate sensor. Depending on if OOK or FSK modulation modes are enabled (via enOOK and enFSK signals, respectively), ei- ther the power-oscillator biasing transistors (Mf [5:0] in Fig. 4), or the capacitive DAC transistors (Ms1-3) are activated, re- spectively. FSK is achieved by switching between two different programming codes (i.e., frequencies), set by [7:0] and [7:0]. A inverter-transmission gate circuit [6] is used to create phase-matched differential signals to drive a multiplexor selecting one of or at a time. ...
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... wireless energy receiver circuit design is already in- cluded in Fig. 4. In fact, since the antenna can be modeled as an inductor that has a center tap, creating a full bridge rectifier is as simple as placing two diodes between the two ends of the inductor, connected to ground (diodes D1 and D2 in Fig. 4). Interestingly, these diodes are in fact already required for ESD protection. Thus, adding wireless ...
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... wireless energy receiver circuit design is already in- cluded in Fig. 4. In fact, since the antenna can be modeled as an inductor that has a center tap, creating a full bridge rectifier is as simple as placing two diodes between the two ends of the inductor, connected to ground (diodes D1 and D2 in Fig. 4). Interestingly, these diodes are in fact already required for ESD protection. Thus, adding wireless power transfer functionality does not add any additional complexity and, more importantly, does not add any additional parasitic capacitance on the sen- sitive antenna interface nodes. As described in Section III, reduced parasitics on ...
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... To avoid such an event, a reliable POR is required. Fortunately, cre- ating a POR signal can be achieved in a very low-complexity, low-leakage manner. Since the charge pump supply, , requires 600 ms to initialize following initialization [9], [10], a simple inverter structure can be used to generate the req- uisite POR signal, as illustrated in Fig. 4. Specifically, an in- verter powered from the supply with at the input will nominally output a logic high value until crosses the inverter threshold (nominally several hundred milliseconds after initialization). The inverter is designed with high- transistors, since there is no opportunity to power-gate the ini- tialization logic. The ...
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... Designers and researchers have therefore innovated numerous ways to create transmitters (TXs) and receivers (RXs) that achieve sub-mW power consumption. Sub-mW transmitters have generally used binary modulations such as on-off keying (OOK), binary phase-shift keying (BPSK) and binary frequency-shift keying (BFSK) [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. These simple modulation schemes enable the use of low-complexity low-power transmitter architectures. ...
... These simple modulation schemes enable the use of low-complexity low-power transmitter architectures. Therefore, some of the transmitters in [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], and [13] have achieved power consumptions even lower than 100 μW and consumed down to 16.5 pJ of energy per transmitted bit. ...
In this paper, we compare in a new way the energy efficiencies of modulations that have been popular in ultra-low power (ULP) transmitters. The comparison considers how the choice of modulation affects the combined energy consumed per bit (EPB) by the carrier synthesizer and power amplifier (PA). The comparison includes on-off keying (OOK), binary phase-shift keying (BPSK), binary frequency-shift keying (BFSK), pulse-position modulation (PPM) and differential PPM (DPPM). The results suggest that using OOK, BPSK or BFSK can consume tens to hundreds of percents more energy per bit compared to PPM and DPPM. Furthermore, a new energy efficiency figure of merit (FOM) is derived for transmitters. It accounts for consumed power, output power, data rate, signal bandwidth and signal-to-noise ratio required by the utilized modulation. The FOM can be applied to various types of transmitters with numerous modulations. We also present a sub-100
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... Thus, some low energy-demanding electronics can be powered by the TECs via the utilization of low-grade heat. For example, the wireless sensor nodes only consumed a small power of 295 pW [57], and the novel sub-nW data transmitter only consumed an average power of 78 pW [58]. In our previous work, we also reported a self-powered strain sensor initiated by a gel-based TEC through the harvesting of human body heat [59]. ...
The design of power supply systems for wearable applications requires both flexibility and durability. Thermoelectrochemical cells (TECs) with large Seebeck coefficient can efficiently convert low-grade heat into electricity, thus having attracted considerable attention in recent years. Utilizing hydrogel electrolyte essentially addresses the electrolyte leakage and complicated packaging issues existing in conventional liquid-based TECs, which well satisfies the need for flexibility. Whereas, the concern of mechanical robustness to ensure stable energy output remains yet to be addressed. Herein, a flexible quasi-solid-state TEC is proposed based on the rational design of a hydrogel electrolyte, of which the thermogalvanic effect and mechanical robustness are simultaneously regulated via the multivalent ions of a redox couple. The introduced redox ions not only endow the hydrogel with excellent heat-to-electricity conversion capability, but also act as ionic crosslinks to afford a dual-crosslinked structure, resulting in reversible bonds for effective energy dissipation. The optimized TEC exhibits a high Seebeck coefficient of 1.43 mV K ⁻¹ and a significantly improved fracture toughness of 3555 J m ⁻² , thereby can maintain a stable thermoelectrochemical performance against various harsh mechanical stimuli. This study reveals the high potential of the quasi-solid-state TEC as a flexible and durable energy supply system for wearable applications.
... Fig. 7(a) compares the proposed RC+ANN with direct transmission of all digitized sensor data, and digital baseline which performs insensor classification with digital ANN before transmission of prediction scores. Transmission energy is assumed to be state-of-the-art 38pJ/bit [15], and the ADC for digitizing ECG segment is assumed to consume 5fJ/conversion-step at 1kHz and 12-bit resolution [16]. RC+ANN reduces energy/inference by 13× compared to digital baseline at 3% loss in accuracy, and by 155× compared to conventional technique. ...
... After separating the system power into two parts, i.e., wireless communication and signal conversion with timing management, the required BFC area can be determined by only considering the power of the supply voltage monitor, whose power consumption can potentially reduce to become the pW region. Therefore, the tens-of-mm 2 BFC is no longer necessary, and the submm 2 BFC [14] with the sub-mm 2 IC with on-chip solar cells can be integrated on CGM contact lenses. Fig. 3 shows the operation principle of the proposed system. ...
... Fig. 4 shows the direct-RF power oscillator architecture of the TX. The direct-RF power oscillator architecture is selected for short active time operation in reference to [2], [14] with the on-chip center-tapped loop antenna. The 4-turn top-metal-based antenna, with a size of 385 μm×385 μm, features an inductance of 4 nH at each half side confirmed by simulation, which is the same as the antenna in [3]. ...
This brief proposes a solar-cell-assisted wireless biosensing system that operates using a biofuel cell (BFC). To facilitate BFC area reduction for the use of this system in area-constrained continuous glucose monitoring contact lenses, an energy harvester combined with an on-chip solar cell is introduced as a dedicated power source for the transmitter. A dual-oscillator-based supply voltage monitor is employed to convert the BFC output into digital codes. From measurements of the test chip fabricated in 65-nm CMOS technology, the proposed system can achieve 99% BFC area reduction.
... They can potentially harvest human body heat in an ambient environment to drive micro-TE devices for low-power applications. [1][2][3][4][5] For practical utilization of exible TE devices, TE materials should possess high TE performance. Thus, a high gure of merit (ZT, which is expressed as S 2 sT/k, where S, s, k and T are the Seebeck coefficient, electrical conductivity, thermal conductivity and absolute temperature, respectively) is usually desired. ...
Organic polymer thermoelectrics (TEs) that can realize direct heat-to-electricity conversion hold great potential in flexible and wearable applications and thus are receiving tremendous attention. Constructing polymer-based nanocomposites represents an effective approach in achieving high TE performance, while current studies on the underlying mechanisms for the improvement of TE properties in aspects of interfacial nanostructures are insufficient. In this work, flexible ternary nanocomposite films with unique interfacial architectures are developed by sequential electrochemical polymerization of conducting polymers and subsequent anion treatment. The optimized interfacial architectures contribute to enhanced π electron conjugation, which facilitates interfacial charge transfer and favours large-area charge transport. The anion treatment further enables the molecular chains to arrange in a more ordered configuration, leading to improved carrier mobility. As a result, the nanocomposites exhibit high power factors of more than 500 μW m⁻¹K⁻²that outperform most of the literature-reported peer composites. The feasible interfacial architecting and anion treatment methods proposed in this study demonstrate high potential in designing high-performance TE nanocomposites.
... For example, the wireless sensor nodes with dynamic leakage-suppression logic can be well operated under the small power of 295 pW [4]. The novel sub-nW radio transmitter only consumed an average power of 78 pW to complete data transmission [5]. Moreover, various functional sensors that powered by specifically-designed TEDs can realize continuous and distributed remote data transmission [6][7][8]. ...
Despite the rapid development for thermoelectrics (TEs) and aerogels, elastic aerogel TE generators (TEGs) with vertical-type architectures have not been found to harvest heat utilizing vertical temperature difference. Herein, an elastic poly(3,4-ethylenedioxytiophene)-tosylate(PEDOT-Tos)/single-walled carbon nanotube (SWCNT) TE aerogel was fabricated via convenient chemical oxidative polymerization, physical mixing and subsequent freeze-drying process. Then, we report the first elastic TEGs consisting of vertical-type aerogel legs, which not only inherit the advantages of ultralight weight and compressibility of aerogels, but also display high TE performance. The output performance can be conveniently adjusted by the number of legs, the temperature difference and compressive strain. An optimum output power of 1967 nW (output power density of 30.73 mW m⁻²) is achieved for the TE generator using 10 unipolar aerogel legs at 50% strain and temperature difference of 50 K. Furthermore, the ultralight and compressible TEG displays excellent capability of harvesting heat under vertical temperature difference and mechanical deformation, such as on hot oil/plate or compression by human body. The results will greatly facilitate the development of TE aerogels and TEGs, and widen the versatile application scenarios.
... 6,7 Harvesting energy from human body via TEGs thus represents a promising direction in designing self-powered wearable electronics, especially when the cutting-edge technologies have significantly reduced their power requirement, suggesting a bright future for the practical applications of thermoelectric energy harvesting. [8][9][10] Whereas, existing TEGs are primarily fabricated using rigid or non-stretchable components, which restrains their capability to conform to human skin or accommodate human motions. [11][12][13][14][15] To meet the requirement of wearability, TEGs must possess high mechanical flexibility and preferable stretchability, and in the meantime can provide consistent energy output even having encountered mechanical damages. ...
Thermoelectric generators (TEGs) demonstrate great potential for flexible and wearable electronics due to the direct electrical energy harvested from waste heat. Good wearability requires high mechanical flexibility and preferable stretchability, while current TEGs are primarily developed with rigid or non-stretchable components, which do not conform well to human skin or accommodate human motions, thus hindering further applications. Herein, a wavy architecture was proposed to fabricate stretchable TEGs, wherein a stretchable and self-healable hydrogel was employed as a device substrate, and intrinsically flexible, high-performance thermoelectric (TE) films were attached to form wavy morphologies. The wavy-structured TEG could be stretched readily to 300%; in the meantime. It could sustain a stable energy output able to retain more than 90% TE performance, thus, outperforming most of the reported state-of-the-art TE materials and TEGs. It also demonstrated a desired device-level self-rescuing capability that originated from the effective self-healing of the hydrogel and the wavy structure of TE legs, thereby providing constant energy supply upon injuries or damages. This work offers a promising approach to the design of next-generation stretchable and wearable TEGs.
... For example, the wireless sensor nodes with dynamic leakage-suppression logic can be well operated under the small power of 295 pW [4]. The novel sub-nW radio transmitter only consumed an average power of 78 pW to complete data transmission [5]. Moreover, various functional sensors that powered by specifically-designed TEDs can realize continuous and distributed remote data transmission [6][7][8]. ...
Despite the rapid advancements made for thin-film thermoelectric materials, the rational design of corresponding thermoelectric devices (TEDs) raises the urgent need for thermal optimization to meet the requirement of efficient utilization of the temperature gradient vertical to the device plane. Herein, a three-dimensional spring-like thermoelectric device (S-TED) with fundamantal dual elastomer layers and air gaps is proposed. The novel device architecture not only inherits excellent flexibility and compressibility, but also enables the capability of harvesting waste heat under vertical temperature gradient. Detailed analysis of thermal modeling indicates that optimization is considered in three aspects compared to conventional TEDs, including the strengthened contact for more efficient interfacial heat transfer, the hindered heat transfer across the device body via the construction of thermally-insulating air gaps, and the effective heat sink that facilitates the rapid heat transfer from device to the ambient. The as-fabricated S-TED delivers a high output power of 749.19 nW under a vertical gradient of 30 K with only three pairs of p-n couple, corresponding to high output power of 416.22 nW cm⁻² compared to other reported flexible TEDs. The design strategy conceived in this work will promote the development of high-performance TEDs for flexible and wearable applications.
... Since the resonant frequency changes with fabrication variations, the on-chip capacitor is digitally tunable to adjust the frequency. The transmission efficiency at higher frequencies of 2.4 GHz allows a good compromise between tissue losses and loop antenna efficiency, although the efficiency is expected to be significantly lower in a biological environment than in air [31]. The transmitter supports both on-off keying (OOK) and frequency-shift keying (FSK) modulations. ...
Objective. Clinical trials previously demonstrated the spectacular capacity to elicit visual percepts in blind patients affected with retinal diseases by electrically stimulating the remaining neurons on the retina. However, these implants restored very limited visual acuity and required transcutaneous cables traversing the eyeball, leading to reduced reliability and complex surgery with high postoperative infection risks. Approach. To overcome the limitations imposed by cables, a retinal implant architecture in which near-infrared illumination carries both power and data through the pupil is presented. A high efficiency multi-junction photovoltaic cell transduces the optical power to a CMOS stimulator capable of delivering flexible interleaved sequential stimulation through a diamond microelectrode array. To demonstrate the capacity to elicit a neural response with this approach while complying with the optical irradiance safety limit at the pupil, fluorescence imaging with a calcium indicator is used on a degenerate rat retina. Main results. The power delivered by the laser at safe irradiance of 4 mW/mm2 is shown to be sufficient to both power the stimulator ASIC and elicit a response in retinal ganglion cells (RGCs), with the ability to generate of up to 35 000 pulses per second at the average stimulation threshold. Significance. This confirms the feasibility of wirelessly generating a response in RGCs with a digital stimulation controller that can deliver complex multipolar stimulation patterns at high repetition rates.
... The uplink utilizes M-ary DPPM to reduce the EPB through decreased active time of the transmitter front-end per bit. A low-leakage direct-RF narrowband transmitter front-end [3], [6] is utilized. Due to its low standby power and fast startup, duty cycling and DPPM can be performed efficiently. ...
... Among published low-power transmitters, the EPB has been a popular metric for energy efficiency. It has often been reduced by utilizing a binary modulation with a high data rate [3]- [5], [15]. With binary modulations such as OOK, BPSK and BFSK, one bit is transmitted in one baseband clock cycle ...
... One option is a direct-modulation architecture where the major blocks are a carrier synthesizer, a modulator, and a PA [1], [5]. Another option is a direct-RF power oscillator (PO) topology that consists of two major blocks: a modulator and a PO [1], [3], [6]. These architectures have been popular in published sub-mW narrowband transmitters and have enabled low EPBs. ...
This article presents a low-power wireless narrowband (NB) transceiver consisting of a 434-MHz NB transmitter (NBTX) and a 434-MHz NB receiver (NBRX) implemented in 0.18 μm CMOS. The NBTX utilizes differential pulse-position modulation (DPPM) to decrease consumed energy per bit (EPB) by up to 67% compared to on-off keying (OOK). The packet error performance of DPPM with a soft-decision decoding scheme is analyzed. According to the results, the packet error ratio (PER) does not deteriorate compared to OOK except at very low signal-to-noise levels. The lowest power consumption of the NBTX is 8.3 μW when DPPM data is transmitted continuously. Utilizing packet-mode transmission, the average power consumption is 67 nW at a data rate of 4.8 kbps. The transmitted data was received with a PER of 0.1% by a receiver placed at a 30-meter distance from the NBTX. With a higher power consumption of 2.5 μW at the same data rate, the estimated line-of-sight (LOS) uplink range is up to 200 meters. The NBRX is a mixer-first uncertain-IF receiver. A temperature-compensated ring oscillator (TCRO) is utilized as a local oscillator. Its measured deviation of frequency is from +0.1% to -1.2% over a temperature range from -40 to +85 °C. The NBRX utilizes Manchester encoding and the sensitivity is -87 to -82 dBm over the temperature range at a data rate of 40 kbps. The NBRX consumes 85 μW.
