Minimum Detectable Power Research Articles

Adaptable integrated sensing and communication for UAV‐empowered 6G networks

AbstractIntegrated sensing and communication (ISAC) is a promising technique for unmanned aerial vehicle‐empowered 6G networks. This letter proposes a novel, adaptable ISAC mechanism. Firstly, both the communication and sensing channel models under the Doppler and beam‐squint effects are investigated. Then, an adaptive sensing method is proposed by the joint design of signal echo sensing and beam‐squint sensing under practical environment. Specifically, when the echo power is larger than the minimum detectable power, the proposed method could realize the effective sensing by utilizing the system model without feedback. Otherwise, the proposed method could exploit the beam‐squint for sensing with the feedback of the sub‐carrier index. Finally, various simulation results are provided to demonstrate the effectiveness of the proposed scheme.

Josephson radiation threshold detector

A Josephson radiation threshold detector (JRTD) that is based on the threshold behaviour of a current bias Josephson junction (CBJJ) is designed and fabricated for infrared radiation (IR@1550nm) detection at low temperatures. To achieve the optimal performance, we develop a binary hypothesis detection method to calibrate Josephson threshold behaviours (i.e. the switching current distributions of the CBJJ with the Al/AlOx/Al junction) in the absence and presence of radiation. In the absence of IR radiation, the junction transitioned with a measurable voltage drop across the junction, and this signal was treated as the events of hypothesis H0. The events of junction transition observed in the presence of the IR radiation served as hypothesis H1. Considering the usual Gaussian noise and based on statistical decision theory, the accumulated data of the measured switching current distributions are processed, and the threshold sensitivity of the demonstrated JRTD device is estimated. The minimum detectable IR radiation power of the proposed detector is approximately 0.74 pW, which corresponds to the photon rate of 5.692 × 106 photons/second. Further optimisation of JRTDs to implement the desired binary detection of a single photon is still a subject of argument, at least theoretically.

A Micro-Acoustic Enhanced Low-Impedance Antenna System for IoT Wake-Up Receivers

In this work, we propose a passive radio frequency (RF) front-end tailored for wake-up receivers (WuRx) to be deployed in cellular IoT devices and wearables networks, featuring a low radiation resistance antenna and a high-Q matching network implemented with microacoustic resonators integrated to obtain a systematic higher node’s sensitivity at no cost in terms of power consumption. We show how these components can be co-designed to obtain high passive voltage gain, hardwarelevel blocker immunity, and increased resilience to integration parasitics, relaxing link budget for low-power IoT nodes. We report experimental validation of a PCB antenna with 2 dBi gain measured on an 11Ω input resistance at resonance, and an in-house fabricated Micro-Electro-Mechanical System (MEMS) thin-film aluminum nitride bulk acoustic resonator with a quality factor Q = 550 and a piezoelectric coupling coefficient k2 t =7%, hybridly integrated with a commercial off-the-shelf low-power WuRx circuit to benchmark the proposed RF front-end design at 850MHz. We demonstrate a passive voltage gain of 12 dB due to the MEMS resonator, and an additional 11 dB due to the proposed antenna design (for a total of an unprecedented 23 dB passive gain in this frequency range) leading to an over the air.61dBm minimum detectable input power and 23 dB blocker rejection.

A Ka-Band Series Structure Switchable Power Detector System

In this letter, a Ka-band series structure switchable power detector (PD) system equipped with a switchable transformer is proposed for switching detected regions at different input powers. To simultaneously achieve high gain and save dc power, the main RF path is included in a four-stage limiting amplifier (LA) that relies on the double-transformer-coupling (DTC) and current re-used (CR) technique. By switching different detectable paths containing the switchable transformer and PD, the detectable region is changed to a different power region. At a log error of ±1 dB, the measured results indicate that the minimum detectable power (MDP) and dynamic range (DR) are -42 dBm and 49 dB, respectively, at 26 GHz. In the four modes, the measured peak slope values are 30/35/36/34 mV/dB, respectively. At a supply voltage of 1.2 V, the dc power of the PD system is 8.4 mW. These results indicate that, compared with amplifier-based PD systems, the proposed system has a better MDP and DR, and the lowest dc power.

High-sensitivity graphene/Cu2O hybrid photodetectors based on photo-induced quantum capacitance

Graphene/semiconductor hybrid photodetectors have attracted much attention recently for their excellent optoelectronic properties. However, high background current and 1/f noise limit their sensitivity. In this paper, the phenomenon of photo-induced quantum capacitance was found based on the transfer-free graphene/Cu2O/Cu structure. Under illumination, the Fermi level in graphene can be modulated by the photogenerated holes trapped in Cu2O nanoparticles, which causes the capacitance response phenomenon. The maximum capacitance response of 104 F/W with the minimum detectable light power of 5.3 fW was achieved at room temperature.

Monolithic Silicon-Based Photovoltaic-Nanoplasmonic Biosensor With Enhanced Limit of Detection and Minimum Detectable Power

On-chip, fully integrated electrical readout nanoplasmonic biosensors are suitable technology for the increasing demands of compact, portable, cost-efficient, and sensitive biosensors. In this paper, an ultra-compact photonic biosensor based on plasmonic nanostructure integrated with a PIN photovoltaic detector in a single chip is presented. The refractive index of different biosamples results in a shift in the surface plasmon resonance wavelength of the biosensor, and the PIN photovoltaic detector measures the intensity of transmitted light from the photonic structure at the plasmonic resonance wavelength. The biosensor shows a linear optical response of 354 nm/RIU and electrical sensitivity of about 16.9 mA/W.RIU for a wide range of biosamples. The PIN photovoltaic ultra-low dark current enables an extremely desirable limit of detection of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−8</sup> RIU and minimum detectable power of −54 dBm for the biosensor. Moreover, a simple light-emitting diode is used as the light source in the biosensor's structure, which reduces its complexity and price by eliminating any extra optical setups and beam shapers. The presented structure is an important step forward for the realization of practical and handheld lab-on-chip nanophotonic biosensors, which leads to eliminating large clinical laboratories.

Calculation model and analysis of laser echo power based on dual‐transmitter and dual‐receiver laser circumferential scanning detection mechanism

AbstractTo ensure that the laser proximity fuze can detect the ground target during the intersection between the laser detection system and the ground target, based on the dual‐transmitter dual‐receiver laser circumferential scanning detection mechanism, we established the constraint functions of scanning frequency and laser pulse frequency without missing measurement. According to the surface characteristics of the plane target, we derived the calculation models of the laser echo power and the minimum detectable echo power of the detection system to the plane target under the random intersection attitude. The calculation function of the angle between adjacent laser beams is obtained based on the minimum detectable echo power. We discussed the relation of the scanning frequency, the laser pulse frequency, the angle between adjacent laser beams and the intersection angle, focused on the influence of the intersection angle and the detection distance on the laser echo power. The simulation experiments were carried out under different laser peak powers and detection distances, the experimental results fully demonstrate that the laser echo power calculation model established in this paper is correct; the detection ability of the system is improved to a certain extent by increasing the laser peak power.

Modified Shannon’s Capacity for Wireless Communication [Speaker's Corner

In 1948, Claude Shannon published "A Mathematical Theory of Communication", which laid the foundation of modern digital communications, where the maximum channel capacity is given by the famous Shannon’s equation: C = B x log <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (1+P/N) where B is the channel bandwidth, P is the signal power transmitted, and N is the noise floor of the system (or channel). Normally, P/N is also defined as the signal-to-noise ratio (SNR). This equation is known as the Shannon limit. If the conducting losses are ignored for wired communication, then all of the power from the sender will be received by the receiver. Thus, the transmitter and the corresponding receiver will both have the same maximum channel capacity, as given above. Although the equation was given for pointto-point wired communication, this equation has been widely adopted in the literature for modern wireless and mobile communication, including the coming 5G and beyond. Now 6G is under discussion worldwide, and the equation is still being applied in the literature as the golden rule to determine the maximum channel capacity for 5G and beyond. The equation can be modified to show the maximum channel capacity for wireless communications It is argued that instead of using the normal noise floor N in Shannon's equation, received power strength P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> and the minimum detectable power level of a receiver P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> are used, which allows the inclusion of both the path-loss effect and the hardware requirements, which makes it more practical. Thus, the new definition of the channel capacity is linked with the system parameters so that the entire wireless system can be optimized from the hardware point of view. With a given required minimum SNR and the maximum power ceiling, the channel capacity can be determined. In addition, the modified Shannon's equation shows that higher-order modulations result in lower capacity if the maximum transmitting power is fixed.

Photomemory and Pulse Monitoring Featured Solution‐Processed Near‐Infrared Graphene/Organic Phototransistor with Detectivity of 2.4 × 1013 Jones

AbstractEmerging graphene/organic phototransistors are eye‐catching technologies owing to their unique merits including easy/low‐cost fabrication, temperature independent, and achieving various functions. However, their development in the near‐infrared (NIR) region is experiencing a bottleneck of inferior sensitivity due to low exciton dissociation efficiency and inefficient charge extraction rate. Here, a novel‐design solution‐processed graphene/organic NIR phototransistor is reported, that is, creatively introducing electron extraction layer of ZnO on graphene channel and employing organic ternary bulk heterojunction as photosensitive layer, successfully breaking that bottleneck. The phototransistor exhibits a high responsivity of 6.1 × 106 A W−1, a superior detectivity of 2.4 × 1013 Jones, and a remarkable minimum detection power of 1.75 nW cm−2 under 850 nm radiation. Considering its excellent NIR detection performance, a noncontact transmission‐type pulse monitoring is carried out with no external circuit support, from which human pulse signal and heart rate can be displayed in real time. The phototransistor, interestingly, can be switched into a photomemory function with a retention time of 1000 s in the atmosphere through a gate voltage of −20 V. The design takes the characteristics of graphene/organic phototransistors to a higher level, beyond the limit of sensitivity, and opens up a novel approach for developing multifunction devices.

A line laser detection screen design and projectile echo power calculation in detection screen area

A line laser with high power as the background light source for the design of a new photoelectric detection target is proposed in this paper, aiming to improve the detection ability of the traditional photoelectric detection target under low background illumination. The laser emitted pulse waveform function and the laser echo pulse response function were used to establish the mathematical model of the reflected echo power of projectile in the detection area and derive the calculation function of minimum detectable echo power in the line laser detection screen, according to information of the line laser emitted power, incident angle of projectile, duration time and detection distance of projectile passing through the line laser detection screen. Calculations and experimental results showed that the design method of line laser detection screen and calculation model of laser echo power are reasonable, and the detection ability of line laser detection screen is obviously higher than that of traditional photoelectric detection screen, especially in low background illumination; at the same time, the designed line laser detection screen was used to combine a six line laser detection screen intersection test system, based on live ammunition for shooting. The test system is stable and able to obtain the dynamic parameters of the flying projectile, verifying that the design of the line laser detection screen in new photoelectric detection target can be suitable for shooting range test applications.

Temperature-compensated multi-point refractive index sensing based on a cascaded Fabry-Perot cavity and FMCW interferometry.

We proposed a novel temperature-compensated multi-point refractive index (RI) sensing system by the combination of the cascaded Fabry-Perot (FP) sensors and the frequency modulated continuous wave (FMCW) interferometry. The former is used for simultaneous sensing of RI and temperature, and the latter is used for multiplexing a series of the cascaded FP sensors to realize multi-point sensing. By means of Fourier transform-based algorithms, the interference spectra of each sub-FP sensors can be divided and demodulated independently. Experimentally, three cascaded FP sensors are multiplexed to verify multi-point RI and temperature sensing ability. RI sensitivity up to ∼1200 nm/RIU is obtained within RI range from 1.3330 to 1.3410, and temperature sensitivity up to ∼0.17 nm/°C is obtained within temperature range from 20 °C to 80 °C. The RI precision is as high as 10-5 RIU and the temperature precision is as high as 0.05 °C. In addition, the prospective multiplexing number could reach about 4000 estimated by the minimum detectable light power. The proposed sensing system has potential advantages in the practical applications that require a large number sensing points.

Miniature Fiber-Spectrophotometer for Real-Time Biomarkers Detection

This paper presents a miniature and cost-effective cell fiber-spectrophotometer based on fluorescence emission sensing for real-time detection of biomarkers. The prototype comprises a highly sensitive spectrometer embedded in an inexpensive 3D-printed housing and a custom-designed printed circuit board to transmit the data wirelessly. Results show that this portable system can identify micro-volume samples of tubulin protein, a well-known biomarker, to study different types of cancer. Additionally, our ambulatory prototype is small in size (30 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times24$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times43$ </tex-math></inline-formula> mm), lightweight (19 g), economical, and low-power (103 mW). Fluorescence spectrophotometry measurement results obtained <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> for stained VERO E6 cells using the presented prototype are reported. A set of samples with varying concentrations of Alexa Fluor 488 were also tested, and their spectral responses were measured within the range of 340–850 nm with a resolution of 15 nm. The measured limits of quantification and detection are 20 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4~\mu \text{g}$ </tex-math></inline-formula> /mL, respectively, while the measured responsivity is 85 mV/nW with a minimum detectable power of 117 fW at 519 nm. Intra- and inter-day relative standard deviations of 1.5% and 4.7%, respectively, were measured during longitudinal sensitivity experiments.

Design of a Microwave Power Detection System in the 5G-Communication Frequency Band.

At present, the proposed microwave power detection systems cannot provide a high dynamic detection range and measurement sensitivity at the same time. Additionally, the frequency band of these detection systems cannot cover the 5G-communication frequency band. In this work, a novel microwave power detection system is proposed to measure the power of the 5G-communication frequency band. The detection system is composed of a signal receiving module, a power detection module and a data processing module. Experiments show that the detection frequency band of this system ranges from 1.4 GHz to 5.3 GHz, the dynamic measurement range is 70 dB, the minimum detection power is −68 dBm, and the sensitivity is 22.3 mV/dBm. Compared with other detection systems, the performance of this detection system in the 5G-communication frequency band is significantly improved. Therefore, this microwave power detection system has certain reference significance and application value in the microwave signal detection of 5G communication systems.

Photonics-assisted frequency-coded signal receiver with ultra low minimum detectable power.

A receiver for weak frequency-coded microwave signal reception based on microring resonators array is proposed. This setup uses the nonlinear interaction of a microwave signal and an optical pump to generate an up-conversion signal to achieve the wideband signal reception. The minimum detectable power of this method reaches -93.2 dBm, which is suitable for the detection of weak signals. The results demonstrate a huge power conversion efficiency with η = 4.37×104, a wide conversion bandwidth of 2π×200 MHz, and a large 1-dB compressed dynamic range of 70.2 dB. The receiver can directly use the microwave signal received by the antenna that greatly reduces the volume and power consumption of the detection system. It is highly competitive in microwave photonics radar fields.

Low-Frequency Nonresonant Rectification in Spin Diodes

Spin-diodes are usually resonant in nature (GHz frequency) and tuneable by magnetic field and bias current with performances, in terms of sensitivity and minimum detectable power, overcoming the semiconductor counterpart, i.e. Schottky diodes. Recently, spin diodes characterized by a low frequency detection (MHz frequency) have been proposed. Here, we show a strategy to design low frequency detectors based on magnetic tunnel junctions having the interfacial perpendicular anisotropy of the same order of the demagnetizing field out-of-plane component. Micromagnetic calculations show that to reach this detection regime a threshold input power has to be overcome and the phase shift between the oscillation magnetoresistive signal and the input radiofrequency current plays the key role in determining the value of the rectification voltage.

Method for Receiving Weak Microwave Photonics Signals Based on Electro-Optical Up-Conversion

A novel method for receiving weak microwave photonics signals based on a micro-ring resonator is proposed. This approach uses the nonlinear interaction of a microwave and an optical pump to generate an up-conversion signal to achieve the signal reception. The minimum detectable power of this method reaches −89.79 dBm, which is suitable for the detection of weak signals. The power conversion efficiency and bandwidth have a 10 times promotion compared to similar conversion methods at room temperature. The result also demonstrates that the detection sensitivity can be improved by five orders of magnitude compared to the traditional modulators, and the output signal-to-noise ratio can be improved by more than 17 dB using a micro-ring resonator.

Full-Field Terahertz Imaging at Kilohertz Frame Rates Using Atomic Vapor

Terahertz (THz) technologies, generally defined as operating in the 0.1-10THz range, bridge the gap between electronic and photonic devices. Because THz radiation passes readily through materials such as plastics, paper and cloth it can be employed in non-destructive testing, and as it is non-ionising it is considered safe for security and biomedical applications. There is significant demand for high speed THz imaging across a range of applications but, despite ongoing efforts, fast full-field imaging remains an unfulfilled goal. Here we demonstrate a THz imaging system based upon efficient THz-to-optical conversion in atomic vapour, where full-field images can be collected at ultra-high speeds using conventional optical camera technology. For a 0.55 THz field we show an effective 1 cm $^{2}$ sensor with near diffraction-limited spatial resolution and a minimum detectable power of 190 $\pm$ 30 fW s$^{-1/2}$ per 40x40${\mu}$m pixel capable of video capture at 3000 frames per second. This combination of speed and sensitivity represents a step change in the state of the art of THz imaging, and will likely lead to its uptake in wider industrial settings. With further improvements we expect that even higher frame rates of up to 1 MHz would be possible.

First results from the WISPDMX radio frequency cavity searches for hidden photon dark matter

The origin of non-baryonic Dark Matter remains elusive despite ongoing sensitive searches for heavy, thermally produced dark matter particles. Recently, it has been shown, that non-thermally produced vector bosons (sometimes called hidden photons) related to a broken U(1) gauge symmetry are among the possible WISP (weakly interacting slim particles) dark matter candidates. The WISP Dark Matter eXperiment (WISPDMX) is the first direct hidden photon dark matter search experiment probing the particle masses within the 0.8–2.07 μeV range with four resonant modes of a tunable radio frequency cavity and down to 0.4 neV outside of resonance. In this paper, we present the results from the first science run of WISPDMX comprising 22 000 broadband spectra with a 500 MHz bandwidth and a 50 Hz spectral resolution, obtained during 10-second integrations made at each individual tuning step of the measurements. No plausible dark matter candidate signal is found, both in the individual spectra reaching minimum detectable power of 8× 10−19 W and in the averaged spectrum of all the measurements with the minimum detectable power of 5× 10−22 W) attained for a total of 61 h of data taking. Using these spectra, we derive upper limits on the coupling constant of the hidden photon at the levels of 10−13 for the resonant frequency ranges and 10−12 for broadband mass range 0.2–2.07 μeV, and steadily increasing at masses below 0.2 μeV.

Graphene-Based Infrared Position-Sensitive Detector for Precise Measurements and High-Speed Trajectory Tracking.

Noncontact optical sensing plays an important role in various applications, for example, motion tracking, pilotless automobile, precision machining, and laser radars. A device with features of high resolution, fast response, and safe detection (operation wavelength at infrared (IR)) is highly desired in such applications. Here, a near IR position-sensitive detector constructed by graphene-Ge Schottky heterojunction has been demonstrated. The device shows high responsivity (minimum detectable power of ∼10 nW), excellent spatial resolution (<1 μm), fast response time (∼μs), and could operate in a wide spectral range (from visible to ∼1600 nm). Applications of precise angle (∼5 × 10-6 degree) and vibration frequency (up to 10 kHz) measurements, as well as the trajectory tracking of a high-speed infrared target (∼100 km/h), have been realized based on this device. This work therefore provides a promising route for a high-performance noncontact IR optical sensing system.

Microfabricated calorimeters for thermometric enzyme linked immunosorbent assay in one-Nanoliter droplets.

Advances in microfabrication allow for highly sensitive calorimeters with dramatically reduced volume, decreased response time and increased energy resolution. These calorimeters hold the potential for designs of ELISA platforms competitive with fluorescent and chemiluminescent technologies. We have developed a new assay platform using conventional ELISA reagents to produce a thermal signal quantifiable using calorimetry. Our optimized micromachined calorimeters have nL reaction volumes and a minimum detectable power of 375pW/Hz1/2. We demonstrate rapid quantification in a model system of trastuzumab, a humanized monoclonal antibody used in the treatment of HER2 overexpressing breast cancers, in human serum using a HER2 peptide mimetic. Trastuzumab concentration and reaction time constant correlated well (R2 = 0.954) and can be used to determine trastuzumab concentrations. The limit of detection for the ThermometricELISA (TELISA) was 10μg/ml trastuzumab in human serum. TELISA allows for a simple readout, reduction in assay time, sample and reagent volumes and has the potential to become a point of care multiplexed platform technology.