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Quasi-bound states in the continuum (q-BICs) in optical metasurfaces have been found to carry special radiation polarization properties. Herein, we have studied the relationship between the radiation polarization state of a q-BIC and the polarization state of the output wave, and theoretically proposed a perfect linear polarization wave generator controlled by the q-BIC. The proposed q-BIC has an x-polarized radiation state, and the y co-polarized output wave is completely eliminated by introducing additional resonance at the q-BIC frequency. Finally, a perfect x-polarized transmission wave with very low background scattering is obtained, and the transmission polarization state is not limited by the incident polarization state. The device can be used to efficiently obtain narrowband linearly polarized waves from non-polarized waves, and can also be used for polarization-sensitive high-performance spatial filtering.

The metasurfaces based on nanostructure film play an important role in many fields. Usually, the properties and functions of metasurfaces are limited by their structure. Once the metasurface samples are processed, their functions have already been restricted. The dual-function device designed in this work utilizes the phase transition characteristic of vanadium dioxide (VO2). The entire layer of VO2 film is inserted between the double metal micro-nano structure. When VO2 film is in the metallic state after phase change, an isotropic narrow absorber is obtained in the terahertz (THz) region, which consists of a top Z-shaped meta-atom, a middle dielectric layer, and a bottom VO2 film. By adjusting structure parameters of VO2 film, perfect absorption is realized at the frequency of 0.525 THz with the overall absorption beyond 91%. When VO2 is in insulating state, the top Z-shaped meta-atom will interact with the bottom Z-shaped structure, and the resonance coupling leads to the appearance of electromagnetically induced transparency (EIT). The designed metal-VO2 hybrid metamaterial opens possible avenues for switchable functionalities in a single device.

Liquid pressure measuring is of increasingly importance to promote sustainable operation of civil and industrial equipment. In this paper, a novel approach based on distance measurement is proposed by using Radio Frequency Identification (RFID) and Hidden Markov Model (HMM). Two RFID tags, which interrogated by reader, are mainly used to build a liquid pressure sensing system (LPSS). At the same time, an ultra-high-frequency RFID chip with self-tuning capability aiming to achieve impedance matching is exploited. While HMM takes pride in its real-time processing and high efficiency so as to make a reasonable prediction of liquid pressure. The feasibility of proposed scheme is verified by double tags coupling circuit design and simulation. Through hardware construction and testing, reliable pressure measurement is achieved in an indoor scenario ( $0.5\textit {cm}\leq {d}\leq 7\textit {cm}$ ). Meanwhile, parameter evaluating model (PEM) and sequential estimation model (SEM), which are based on Maximum Likelihood Estimation (MLE) and HMM respectively, have been proposed to achieve online denoising.

Due to the high redundancy of ultra-wideband (UWB) radio frequency (RF) signal receiving channel and the channel’s non-rotation invariance, the signal-to-noise ratio (SNR) of signal transmission is increased. In order to solve this problem, a circularly symmetric algorithm for the UWB RF signal receiving channel based on spectrum compression cannot effectively reduce the redundancy of UWB RF signal receiving channel; the channel does not have rotation invariance; and the effect of noise reduction is poor. A circularly symmetric algorithm for the UWB RF signal receiving channel based on noise cancellation is proposed, and a noise cancellation structure at the input stage of the receiving channel is constructed to ensure channel noise cancellation and reduce noise in the channel. On this basis, five power zones are used to reasonably select RF devices, receive and downconvert UWB RF signal receiving channel, and convert the received UWB RF signal channel into circular symmetric Gabor transform to reduce redundancy and ensure the strict rotation invariance of the channel. The experimental results show that the proposed algorithm guarantees the quality of the signal and the stable transmission of the signal information. The SNR is 3.8672, and the root mean square error is 0.4078. The third-order cross-modulation coefficient of the signal receiving channel controlled by the algorithm meets the requirements of the index and the mirror frequency rejection requirement of the index.

A U-band phase-locked loop (PLL) with implicit distributed resonators in the voltage-controlled oscillator (VCO) and injection-locked frequency divider (ILFD) using 40 nm CMOS is investigated in this brief. While LC -based, transformer-based, and distributed resonators are typically adopted for mm-wave and sub-terahertz applications, implicit distributed resonators are proposed to enhance the oscillation frequency of the VCO and expand the locking range of the ILFD. The operating principles and the characteristics of the proposed implicit distributed resonators are discussed for intuitive insight. The presented PLL occupies 0.53 mm2 core area and has 81.8 mW power consumption. The PLL achieves a measured frequency range of 8.15 GHz (16%) from 46.75 GHz to 54.9 GHz. The measured phase noise is −91.8 dBc/Hz at 1 MHz offset frequency from a carrier of 46.75 GHz. The proposed U-band PLL can provide a clear and stable local oscillation signal for the transceivers operating at mm-wave and sub-terahertz (sub-THz) frequency band.

Optical bound states in continuum (BICs) are the special lossless electromagnetic resonance modes found in optical transmission media. Optical BICs supported by metasurfaces can bring a series of image-based applications, which can be classified into far-field image-based applications and near-field image-based applications according to imaging distance. The far field image-based applications of optical BICs supported by metasurfaces have been proved theoretically and experimentally. However, the near-field image-based applications are still in the stage of theoretical demonstration, and its practical feasibility is still questioned. In this letter, we have experimentally demonstrated the feasibility of near-field image-based applications of optical BICs. An all-silicon terahertz metasurface that supports near-field displaying based on quasi-BIC is designed. Its unit cell is based on the classic asymmetric elliptical strip structure, and one unit cell of the metasurface corresponds to one display pixel. By observing the electric field distribution of the metasurface in the near-field region, the display of the given image is successfully constructed. The near-field image-based application of BICs may be beneficial for the information encryption, the hidden item detection, matter analysis, etc.

To prepare a desired negative differential resistance (NDR) device by standard complementary-metal-oxide-semiconductor (CMOS) process, a photoelectric dual control NDR device with a PNP bipolar-junction-transistor (BJT) and an NPN BJT was designed and fabricated by using the Si-base standard 0.18 μm CMOS process without any process modification and a special substrate. In order to reduce the valley current under optical control, a metal mask was added to the NDR device. The results show that the device exhibits good NDR characteristics under either voltage-control or photo-control. Under voltage-control, a low volley current (0.23 pA) and a high peak-to-valley current ratio (1.4 × 1010) are obtained at less than 1 V. Under photo-control, the two parameters obtained at less than 0.5 V, are 37 nA and 4827, respectively. Also, the device displays fine S-type NDR characteristics and nice maintaining response function under photo-control. These superior photoelectric NDR characteristics endow the device with greatly potential application in the photoelectric logic circuits.

A G-band wideband bidirectional transceiver front-end is proposed. Coupled transmission line (CTL) and the staggered inter-stage wideband matching technique are exploited to extend the bandwidth of low noise amplifier (LNA) and power amplifier (PA). The transmit/receive (T/R) switch is realized as a single-pole-double-throw (SPDT) switch to connect the LNA and PA with good matching performance, low insertion loss, and high isolation simultaneously. The proposed G-band bidirectional transceiver front-end is implemented in 40-nm CMOS and occupies $ {870}\,\, {\mu } \textrm {m} {\times } {910}\,\, {\mu } \text{m}$ die area including the pads. The front-end in the transmitter (TX) mode achieves a measured 3-dB bandwidth of 32.8 GHz with a peak gain of 9.6 dB and a simulated saturated output power of 3.0 dBm, while the receiver (RX) mode features a measured 3-dB bandwidth of 34.8 GHz with a maximum gain of 10.5 dB and a simulated minimum noise figure (NF) of 10.8 dB. The implementation of the bidirectional transceiver front-end demonstrates the feasibility to integrate the TX and RX with a single on-chip antenna in G-band.

A forward-biased silicon-based light-emitting device (Si-LED) was designed and fabricated by standard 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology without any modification. For the Si-LED, wedge-shaped electrodes and needle-like tip were designed to enhance the intensity of electric field. When the Si-LED works at high forward current, the output optical power increases rapidly with the increase of forward current, which is a non-linear growth similar to exponential. To the best of our knowledge, such a phenomenon has never been reported before. Moreover, when the forward current is at 200 mA, the optical power density reaches 32.7 nW·μm 2, which is two or three orders higher than that of other ever reported forward-biased Si-LED fabricated by standard CMOS technology. In addition, the red shift of the main peak in the spectra of Si-LED was observed and analyzed, and also the light-emission mechanism of each peak in the spectra was given.

Direct conversion receiver (DCR) architecture is a promising candidate in the radio frequency (RF) front end because of its low power consumption, low cost and ease of integration. However, flicker noise and direct current (DC) offset are large issues. Owing to the local oscillator (LO) frequency, which is half of the RF frequency, and the absence of a DC bias current that introduces no flicker noise, the subharmonic passive mixer (SHPM) core topology front end overcomes the shortcoming effectively. When more and more receivers (RX) and transmitters (TX) are integrated into one chip, the linearity of the receiver front end becomes a very important performer that handles the TX and RX feedthrough. Another reason for the requirement of good linearity is the massive electromagnetic interference that exists in the atmosphere. This paper presents a linearity-improved RF front end with a feedforward body bias (FBB) subharmonic mixer core topology that satisfies modern RF front end demands. A novel complementary derivative superposition (DS) method is presented in low noise amplifier (LNA) design to cancel both the third- and second-order nonlinearities. To the best knowledge of the authors, this is the first time FBB technology is used in the SHPM core to improve linearity. A Volterra series is introduced to provide an analytical formula for the FBB of the SHPM core. The design was fabricated in a 0.13 &mu, m complementary metal oxide semiconductor (CMOS) process with a chip area of 750 &mu, m &times, 1270 &mu, m. At a 2.4 GHz working frequency, the measurement result shows a conversion gain of 36 dB, double side band (DSB) noise figure (NF) of 6.8 dB, third-order intermodulation intercept point (IIP3) of 2 dBm, LO&ndash, RF isolation of 90 dB and 0.8 mW DC offset with 14.4 mW power consumption at 1.2 V supply voltage. These results exhibit better LO&ndash, RF feedthrough and DC offset, good gain and NF, moderate IIP3 and the highest figure of merit compared to the state-of-the-art publications.

A 190 GHz voltage-controlled oscillator (VCO) with transformer-based push–push frequency doubler in 40 nm CMOS is presented. The layout optimization reduces the parasitics of the transistors. To achieve high output power at a target operating frequency of 190 GHz, design considerations are discussed and a transformer-based push–push frequency doubler is introduced. The digital controlled artificial dielectric transmission line is proposed in replacement of switched-capacitor arrays whose capacitance is more susceptible to process variation. The presented circuit occupies 390 × 430 µm2 die area including the pads and consumes 57.6 mW DC power from a 0.9 V power supply. The proposed VCO achieves a measured continuous tuning range from 181.9 to 195.5 GHz. The measured output power at 195.5 GHz is − 7.26 dBm which is estimated with the typical conversion loss of harmonic mixer. The measured phase noise at 10 MHz offset is − 97.18 dBc/Hz.

In the paper, a mixed-interval multi-pulse position modulation (MI-MPPM) scheme for visible light communication (VLC) system is theoretical proposed and implemented on field programmable gate array (FPGA). It has better bandwidth efficiency than PPM and MPPM. And it has better anti-jamming than MPPM. A real-time VLC link based on phosphorescent white LED is also built to measure the performance of the proposed MI-MPPM scheme. The data rate of 104 Mbps in our VLC system under the distance of 60 cm could be achieved, and bit error rate is 3 . 81 × 1 0 − 5 . As far as we know, it is the highest data rate that can be achieved in continuous real-time VLC system with phosphorescent white LED based on PPM and its derivative modulation. The performance of VLC system under different distances, advantages and the possible application scenarios of MI-MPPM are also discussed.

This paper theoretically explores photocontrolled terahertz amplified modulator in electron plasma wave optically switched resonant tunneling diode (ORTD) gate high-electron mobility transistor. We present a developed distributed circuit model based on the Khmyrova model. Photoexcitation causes ORTD operating state between negative differential conductivity and positive differential conductivity, which power gain of the device can be control by photoexcitation. Numerical and analytical results show that photoexcitation enabling amplified modulator can realize much larger modulation depth (>95%) than what has been reported in photocontrolled modulator. Our results show the potential of this device in several fields of terahertz technology, such as photocontrolled modulator, mixer, and other two port networks.

A double photodiode (PD) constructed by p+/N-well junction and N-well/p-sub junction was designed and fabricated in a UMC 0.18-μm CMOS process. Based on the device structure and mechanism of double PD, a novel small-signal equivalent circuit model considering the carrier transit effect and the parasitic RC time constant was presented. By this model with complete electronic components, the double PD can be incorporated in a commercial circuit simulator. The component values were extracted by fitting the measured S-parameters using simulated annealing algorithm, and a good agreement between the measurement and the simulation results was achieved.

A differential cross-coupled regulated cascode(RGC)transimpedance amplifier(TIA)is proposed. The theory of multi-stage common-source (CS) configuration as an auxiliary amplifier to enhance the bandwidth and output impedance of RGC topology is analyzed. Additionally, negative Miller capacitance and shunt active inductor compensation are exploited to further expand the bandwidth. The proposed RGC TIA is simulated based on UMC 0.18 µm standard CMOS process. The simulation results demonstrate that the proposed TIA has a high transimpedance of 60.5 dBΩ, and a -3 dB bandwidth of 5.4 GHz is achieved for 0.5 pF input capacitance. The average equivalent input noise current spectral density is about 20 pA/Hz1/2 in the interested frequency, and the TIA consumes 20 mW DC power under 1.8 V supply voltage. The voltage swing is 460 mVpp, and the saturation input current is 500 µA.

In this letter, the operation of continuous inverse Class-F (Class-F−1) mode with Class-AB bias conditions is modeled. The extended waveform expression of intrinsic drain current is derived for continuous Class-F−1 power amplifiers (PAs) biased above pinchoff point. Based on the modified current and voltage waveform formulas, the delivered power and efficiency performance is analyzed as a function of conduction angle. Moreover, the design space of fundamental and harmonic load admittances is generalized for any conduction angle between $\pi $ and $2\pi $ . For experimental verification, a broadband PA is implemented with a 6-W LDMOS device. Under a Class-AB bias condition, the fabricated PA exhibits more than 70% power added efficiency and 38-dBm output power with a fractional bandwidth of 62% from 500 to 950 MHz.

This letter discusses the integration of Class-J power amplifiers (PA). A set of modified design equations considering harmonic losses is derived and the inductor losses are discussed. Based on the discussion, a fully integrated Class-J PA with stacked-FET structure is designed and implemented in a $0.18~\mu \text {m}$ CMOS process. The proposed Class-J PA, powered by a 3.3 V supply, achieves a power-added efficiency (PAE) and drain efficiency (DE) of 43.7% and 45.1%, respectively, with a saturated output power of 22 dBm. Along with a maximum gain of 17.4 dB, the broadband PA exhibits a 3-dB band from 2.1 GHz to 4.8 GHz.

Nano-sized ZnSn(OH)6 crystalline particles were synthesized by co-precipitation method at room temperature, in which NaOH as precipitant and oxalic acid as organic functional reagent were used. Scanning electron microscopy and X-ray diffraction analysis suggest that the morphology, size and growth rate of the ZnSn(OH)6 particles can be changed by oxalic acid, and those particles are polycrystalline based on selected area electron diffraction (SAED) and transmission electron microscope data. After dehydration of the ZnSn(OH)6 polycrystalline precursors at high temperature, their ZnSnO3 counterparts were formed, showing an amorphous structure according to SAED analysis. In this process, the morphology, size and oxygen vacancy defects of the former are inherited by the latter except for the crystalline structure. The structural change from polycrystalline to amorphous phase is caused by newly formed oxygen vacancies, which are proved by X-ray photoelectron spectroscopy data, and reflected by ultraviolet (UV) absorption red shift. When the concentration of oxalic acid is 0.059 M in the synthesizing system, the resulting ZnSn(OH)6 precursor has a biggest particle size and average crystalline size. Furthermore, its ZnSnO3 counterpart is most sensitive to ethanol gas, achieving a gas response as high as 147 at 500 ppm under the co-effect of temperature (220 °C) and UV.

A Si-LED with high-power density p+-n junction and wedge-shaped electrodes was fabricated by standard complementary metal oxide-semiconductor (CMOS) process, and its electroluminescence (EL) spectra were measured at different forward currents. By studying the EL spectra, two interesting phenomena were found. One was that the main peak of EL spectra transited from long wavelength (1135 nm) to short wavelength (1078 nm) along with the forward current increased. The other was that two light emission peaks with energy larger than band gap (Eg) were observed. For the first time, reasonable explanations to the two phenomena were given. Here, the peak shift is attributed to that, with forward current increased, the electron-hole pair recombination of the bound excitons without assist of phonons, increases faster than that of those bound or free excitons with assist of phonons. And the existence of two energy-high light emission peaks is resulted from that, under strong electric field, hot holes absorb one or two phonons from the crystal lattice and then recombine with electrons in conduction band.

An integrated temperature control system was designed for microring resonators. It includes a high sensitive temperature sensor, a target temperature calibration circuit and a heater control circuit. It can simplify user settings and compensate process error, which may enhance the practicality of microring resonators.

This letter presents three low-operating-voltage silicon-based light-emitting devices (Si-LEDs) designed and made in a commercial standard 0.18- $\mu $ m CMOS process without any modification. The Si-LEDs with a new three-terminal and wedge-shaped forward-biased carrier-injection-type p+-n junction structure, have high optical powers. The output power increases by two orders of magnitude up to $1.78~\mu $ W without saturation when the forward current is increased from 20 mA to 200 mA. The light-emitting area is the n-type drift region between the n+ region and p+ region. When the forward current increases to 200 mA, the optical power density exceeds 30 nW $\,\cdot \,\mu $ $\mathrm{m}^{-2}$ the power conversion efficiency and external quantum efficiency are $\sim 2\times 10^{\mathrm {\mathbf {-6}}}$ and $8.3\times 10^{\mathrm {\mathbf {-6}}}$ , respectively, higher than all other forward-biased Si-LEDs previously reported to have used CMOS processes without any modification.

Using beam propagation method (BPM), key optical design parameters of InP/AlGaInAs multiple quantum well (MQW) ring laser were numerically analyzed. The influences of waveguide dimensions, curvature radius and gap size on the coupling efficiency were discussed. An InP/AlGaInAs MQW ring laser with radius of 350 μm was designed and realized. The experimental results show that the designed device, lasing at 1 563.2 nm with side mode suppression ratio higher than 20 dB, exhibited unidirectional bistability between the clockwise and counterclockwise modes.

Structure in the design of a dual band Class-J power amplifiers (PA) for obtaining high efficiency is presented in this work. A large-signal transistor model is used to estimate the device's output parasitic elements and based on this, A dedicated matching network used two section transmission line are employed to synthesize Class-J impedance in both two bands. The simulated results of the designed amplifier show an average 65% power added efficiency (PAE) across 0.6–1.0 GHz and an average 60% PAE across 2.6–3.0 GHz whilst delivering an average output power of more than 39.5 dBm. Realization of the design shows the proposed structure's potential to implement the dual band Class-J PA.

Lattice-matched InAlN/AlN/GaN high electron mobility transistors (HEMTs) grown on sapphire substrate by using low-pressure metallorganic chemical vapor deposition were prepared, and the comprehensive DC characteristics were implemented by Keithley 4200 Semiconductor Characterization System. The experimental results indicated that a maximum drain current over 400 mA/mm and a peak external transconductance of 215 mS/mm can be achieved in the initial HEMTs. However, after the devices endured a 10-h thermal aging in furnace under nitrogen condition at 300 °C, the maximum reduction of saturation drain current and external transconductance at high gate-source voltage and drain-source voltage were 30% and 35%, respectively. Additionally, an increased drain-source leakage current was observed at three-terminal off-state. It was inferred that the degradation was mainly related to electron-trapping defects in the InAlN barrier layer.

A novel superimposed photodetector (PD) is put forward. The photodetector can obtain a couple of differential photocurrent signals from one input optical signal. The light injection efficiency and the vertical work distance of this new photodetector are much higher than those of the others. The superimposed photodetctor is designed based on the standard 0.18 m CMOS process. The responsivity, bandwidth and transient response of the photodetector are simulated by a commercial simulation software of ATLAS. The responsivities of two obtained photocurrent signals are 0.035 A/W and 0.034 A/W, while the bandwidths are 3.8 GHz and 5.2 GHz, respectively. A full differential optical receiver which uses the superimposed photodetector as input is simulated. The frequency response and 4 Gbit/s eye diagram of the optical receiver are also obtained. The results show that the two output signals can be used as the differential signal.

This paper presents a detection system for high-accuracy amplitude and phase measurements on RF signals. It is typically used to set up the low-level RF system for particle accelerators. The proposed detector employs the principle of a heterodyne receiver and uses the digital IF architecture with a high oversampling rate to increase the SNR. A discrete Fourier transform-based quadrature demodulator is used to suppress the analog-to-digital converter (ADC) quantization noise and IF harmonics. The system has been evaluated at an IF of 1 MHz and in an RF range of 500-3000 MHz. A graphical user interface is developed to display and record the measured values. The detection accuracy achieved on 500-MHz signals in a 250-kHz bandwidth is better than ±0.0051% for the amplitude and better than ±0.0032 ° for the phase. Experimental results at different frequencies prove that the detection system can meet the demands of state-of-the-art RF control systems for modern particle accelerators.

The transient photoresponse of a backside-illuminated InP/InGaAs uni-traveling carrier photodetector (UTC-PD) is simulated by a 2D drift-diffusion approach utilizing a commercial numerical device simulator (ATLAS). The effects of the epitaxial layer structure and device biasing are taken into account. The simulation results indicate that the absorption region has a critical effect on the photoresponse pulse, and an optimized epitaxial layer structure is given to achieve a fast response while maintaining a reasonable response. Here, the optimized material parameters of the absorption region are 180 nm and 5×1016cm−3, respectively.

In this paper the photocurrent response of InP-based uni-traveling-carrier photodetectors (UTC-PDs) is analyzed using the drift-diffusion approach. Based on the theoretical analysis, an InP/InGaAs UTC-PD is modeled utilizing a numerical device simulator (ATLAS), and the physics of the device’s operation and its performance as a function of biasing and power level are simulated. The simulation results indicate that the linear dynamic range is up to 60 mW, the f−3 dB is about 40 GHz and the full-width at half-maximum (FWHM) of the current pulse is 28 ps with 10 mW optical power injection for an optimized structure UTC-PD.