Binary Frequency Shift Keying Research Articles

Fully Breaking Entanglement of Multiple Harmonics for Space- and Frequency-Division Multiplexing Wireless Applications via Space-Time-Coding Metasurface.

Harmonic generation and utilization are significant topics in nonlinear science. Although the progress in the microwave region has been expedited by the development of time-modulated metasurfaces, one major issue of these devices is the strong entanglement of multiple harmonics, leading to criticism of their use in frequency-division multiplexing (FDM) applications. Previous studies have attempted to overcome this limitation, but they suffer from designing complexity or insufficient controlling capability. Here a new space-time-coding metasurface (STCM) is proposed to independently and precisely synthesize not only the phases but also the amplitudes of various harmonics. This promising feature is successfully demonstrated in wireless space- and frequency-division multiplexing experiments, where modulated and unmodulated signals are simultaneously transmitted via different harmonics using a shared STCM. To illustrate the advantages, binary frequency shift keying (BFSK) and quadrature phase shift keying (QPSK) modulation schemes are respectively implemented. Behind the intriguing functionality, the mechanism of the space-time coding strategy and the analytical designing method are elaborated, which are validated numerically and experimentally. It is believed that the achievements can potentially propel the time-vary metasurfaces in the next-generation wireless applications.

Performance analysis of a RIS-assisted RoFSO communication system over Malaga distribution for smart city applications.

Radio over free space optics (RoFSO) is one of the potential technologies that can satisfy the requirements of 5G services in a smart city. However, as RoFSO is line-of-sight (LOS) communication, one of its limitations is the occurrence of a skip zone in the targeted areas. In this work, a reconfigurable intelligent surface (RIS) is proposed as the solution to overcome this connection difficulty, which prevents signal blocking by generating LOS connections. These RIS modules extend the communication channel coverage, making it more intelligent and controllable. The performance analysis based on outage probability, ergodic channel capacity, and bit error rate has been performed using heterodyne detection. Malaga distribution has been used to model atmospheric turbulence. The exact closed-form expressions of the probability density function and cumulative distribution function of the end-to-end signal-to-noise ratio are derived. Exploiting these derived statistics, system performance is investigated through the ergodic channel capacity, outage probability, and average bit error rate for M-ary quadrature amplitude modulation and two binary modulation schemes: non-coherent binary frequency-shift keying and coherent binary phase-shift keying. Numerical results are compared among different turbulence conditions, link lengths, and scattering errors. The results show that the proposed RIS-assisted RoFSO technology has the potential to be effective for 5G smart city applications.

Experimental Demonstration of a Visible Light Communications System Based on Binary Frequency-Shift Keying Modulation: A New Step toward Improved Noise Resilience.

Visible light communications (VLC) are an emerging technology that is increasingly demonstrating its ability to provide wireless communications in areas where radio frequency (RF) technology might have some limitations. Therefore, VLC systems offer possible answers to various applications in outdoor conditions, such as in the road traffic safety domain, or even inside large buildings, such as in indoor positioning applications for blind people. Nevertheless, several challenges must still be addressed in order to obtain a fully reliable solution. One of the most important challenges is focused on further improving the immunity to optical noise. Different from most works, where on-off keying (OOK) modulation and Manchester coding have been the preferred choices, this article proposes a prototype based on a binary frequency-shift keying (BFSK) modulation and non-return-to-zero (NRZ) coding, for which the resilience to noise is compared to that of a standard OOK VLC system. The experimental results showed an optical noise resilience improvement of 25% in direct exposure to incandescent light sources. The VLC system using BFSK modulation was able to maintain a maximum noise irradiance of 3500 µW/cm2 as compared with 2800 µW/cm2 for the OOK modulation, and an improvement of almost 20% in indirect exposure to the incandescent light sources. The VLC system with BFSK modulation was able to maintain the active link in an equivalent maximum noise irradiance of 65,000 µW/cm2, as opposed to the equivalent 54,000 µW/cm2 for the OOK modulation. Based on these results, one can see that based on a proper system design, VLC systems are able to provide impressive resilience to optical noise.

Adaptive switching for communication profiles in underwater acoustic modems based on reinforcement learning

The underwater acoustic (UWA) channel is a complex and stochastic process with large spatial and temporal dynamics. This work studies the adaptation of the communication strategy to channel dynamics. Specifically, a set of communication strategies are considered, including Frequency-Hopped Binary Frequency Shift Keying (FH-BFSK), Single-Carrier (SC) communication, and multicarrier communication. Based on the channel condition, a reinforcement learning (RL) algorithm, the Deep Deterministic Policy Gradient (DDPG) method along with a Gumbel-softmax scheme is employed for intelligent and adaptive switching among those communication strategies. The adaptive switching is performed on a transmission block-by-block basis, with the goal of maximizing long-term system performance. The reward function is defined based on the energy efficiency (EE) and the spectral efficiency (SE) of the communication strategies. Simulation results and experimental data processing results reveal that the proposed method outperforms a random selection method and a direct feedback method in time-varying channels.

An OOK and Binary FSK Reconfigurable Dual-Band Noncoherent IR-UWB Receiver Supporting Ternary Signaling

This article presents a multiband low-power and low-complexity impulse radio ultrawideband (IR-UWB) noncoherent receiver. The proposed receiver can be digitally reconfigured in three different modes of operation, including two single-band modes and one concurrent dual-band mode. In the two single-band modes, the proposed envelope detection architecture is capable of receiving and demodulating an on–off keying (OOK) pulse stream at RF center frequencies of 2.8 or 4.8 GHz. In the concurrent dual-band mode, the proposed architecture is able to demodulate binary frequency-shift keying (FSK), in addition to OOK demodulation, at center frequencies of 3 and 5 GHz. The receiver is composed of a reconfigurable low-power differential low noise amplifier (LNA), a fully differential squarer (self-mixer circuit), low-pass filter (LPF), and variable gain baseband (BB) amplifiers. The receiver is fabricated in TSMC 130-nm CMOS process technology. The receiver can operate at up to 150 Mb/s with the ternary signaling that is enabled by the binary FSK modulation combined with the OOK modulation in concurrent dual-band mode. At its maximum gain, the receiver achieves a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 72 dBm at a bit error rate (BER) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-3}$</tex-math> </inline-formula> at a 100-Mb/s data rate. It consumes 11.9 and 13.2 mW from a 1.2-V supply in the single-band modes and concurrent dual-band mode, respectively.

Outlooks on Transmitter Energy Efficiency and FOM and a −189.7-dBJ/bit ULP DPPM Transmitter

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> DPPM transmitter (TX) and a 3.2- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> 2-axis gesture sensor interface, implemented in 0.18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS. The TX operates in the 433-MHz band, uses pulse shaping for improved spectrum and achieves a FOM of −189.7 dBJ/bit. The estimated uplink range is up to 1 kilometer.

A Rotating-Permanent-Magnet Array for ULF Through-the-Sea Magnetic Communications

To realize magnetic induction (MI) communication through seawater, a rotating-permanent-magnet array (RPMA) operating in the ultralow frequency (ULF) band is proposed. The array consists of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times $ </tex-math></inline-formula> 5 cylindrical Nd–Fe–B magnets driven by servo motors. To maximize the transmitting magnetic moment, the motors are controlled to rotate synchronously through network communication. The design of the magnet and array configuration is implemented by analyzing the torque and magnetic moment. Magnetic forces between the array magnets are analyzed by using the equivalent static magnetic dipole model. Permalloy sleeves are used to reduce the influence of magnetic force on the synchronization of magnets. The total transmitting magnetic moment of the RPMA is 360 A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot ~\text{m}^{2}$ </tex-math></inline-formula> , and its power efficiency is 14.4 times higher than the conventional transmitting system using coils. Binary frequency shift keying (BFSK) modulation is realized by switching the rotating speed of the magnets and verified by an indoor test. The equivalent orthogonal horizontal magnetic dipole (HMD) model of the array is used, and the magnetic field distribution in layered media is simulated using FEKO. The calculated MI is 100 fT in the position with a distance of 1 km and a depth of 5 m in the sea. The results of the through-the-sea experiment show that the magnetic field of the RPMA can be detected in a range of 500 m by magnetic inductive sensors immersed at a depth of 5 m in seawater and agree well with the simulated results. Transmission bit rates of 10 and 5 b/s can be achieved in the positions of 60 and 110 m.

Resistorless Memristor Emulators: Floating and Grounded Using OTA and VDBA for High-Frequency Applications

The design of the memristor emulator, which has found widespread of applications in analog computation, neuromorphic and biological systems, communications, etc., is much sought for. In this article, a resistorless electronically tunable grounded and floating memristor emulator by employing current-mode (CM) building blocks: operational transconductance amplifier (OTA) and voltage differencing buffered amplifier (VDBA) has been proposed. The proposed emulators can be configured as incremental and decremental operations. The robustness of the proposed emulator has been verified by performing various analyses: nonideal interpretations, process corner variations, temperature fluctuations, and nonvolatility behavior. The layout has been performed, and the theoretical fingerprint characteristics have been simulated and observed using 180-nm CMOS process parameters in the Cadence environment. The pinched hysteresis loop of the proposed memristor emulator maintains up to 5 MHz. The proposed memristor emulator uses less number of circuit components, but it maintains performance in terms of speed and operating range of frequency. Binary frequency shift keying (BFSK) has been performed using the proposed memristor to validate its functionality in the application. This memristor emulator with superior performance can be integrated into the communication system, analog computation, neuromorphic and biological systems, etc.

A 27-MHz frequency shift keying wireless system resilient to in-band interference for wireless sensing applications

&lt;span lang="EN-US"&gt;A 27-MHz wireless system with binary frequency shift keying (BFSK) modulation at 400-kHz is reported. The receiver has been designed to handle in-band interference corrupting the BFSK signal with the use of complex filters and amplitude comparison method. The BFSK modulation is carried out with a voltage-controlled oscillator before up-converting with a 27-MHz local oscillator. The bipolar junction transistors (BJT-based) power amplifier with 30% efficiency pumps 220 mW into a spiral antenna. The inductive-degenerated low-noise amplifier with a voltage of more than 30 dB amplifies an incoming signal before feeding into a mixer for complex direct down conversion. With deliberate Gaussian interference injection, the minimum ratios between the signal with interference and the interference only at the distance of 2.5, 10 and 15 m are 3.3, 8.5 and 11.5 dB, respectively at a maximum data rate of 20 kbps. Without any interference included, the system can achieve a data rate of 40 kbps at the maximum transmission distance of 15 m. Conceptually agreed with the presented bit-error-rate (BER) analysis, the BER measurements with Gaussian and single-tone/two-tone in-band interferences also confirm superiority offered by the amplitude comparison method where the signal-to-noise ratio is at 1 dB for BER=10&lt;sup&gt;-3&lt;/sup&gt; at 10 kbps (10 dB better than the phase detection counterpart).&lt;/span&gt;

Performance of Reconfigurable-Intelligent-Surface-Assisted Satellite Quasi-Stationary Aircraft–Terrestrial Laser Communication System

This paper proposes the use of quasi-stationary aircraft and reconfigurable intelligent surfaces (RIS) to improve the system performance in satellite–terrestrial laser communication downlink. Single-input multiple-output (SIMO) technology is applied to the relay node of a quasi-stationary aircraft. The closed expression of the bit error rate (BER) of an RIS-assisted satellite quasi-stationary aircraft–terrestrial laser communication system (RIS-SHTLC) is derived under the M-distributed atmospheric turbulence model while considering the influence of atmospheric turbulence and pointing errors caused by RIS jitter. The effects of coherent binary frequency shift keying (CBFSK), coherent binary phase-shift keying (CBPSK), non-coherent binary frequency shift keying (NBFSK), and differential binary phase-shift keying (DBPSK) on the performance of an RIS-SHTLC system are simulated and analyzed under weak turbulence. The results show that the RIS-SHTLC system with CBPSK modulation has the best communication performance. Simultaneously, the relationships between the average signal-to-noise ratio (SNR) and BER of the RIS-SHTLC system under different RIS elements are simulated and analyzed, and compared with the traditional SHTLC system. In addition, the influence of the zenith angle, receiving aperture and divergence angle on the performance of the system is studied. Finally, Monte Carlo simulations are used to validate the analytical results.

A 915 MHz IoT Transmitter Employing Frequency Tripler and Digitally Controlled Duty-Cycle/Phase Calibration

A 915 MHz binary frequency-shift keying (BFSK) transmitter (TX) for Internet-of-Things (IoT) applications is presented. The proposed TX adopts a passive frequency tripler, digital duty-cycle/phase calibration, and a low-cost on-chip power amplifier (PA) matching network (MN). The frequency tripler allows an ultralow-power (ULP) implementation of the frequency synthesizer by lowering the maximum operating frequency and relaxing the frequency tuning range requirement. The proposed frequency tripler provides 10.6 dB better 300 MHz spur reduction compared to that of the conventional frequency tripler by adding a series high-pass filter. The two-phase 20% duty-cycle and single-ended 50% duty-cycle calibration circuits drive the frequency tripler and Class-D PA, respectively, suppressing unwanted spurs significantly. The digital duty-cycle/phase calibration circuits, designed based on the quantitative analysis of the stability, offer advantage of technology scaling. The reduced spur relaxes the harmonic filtering requirement at the PA output, leading to an on-chip PA MN with low- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> . Implemented in 55 nm CMOS, the proposed TX shows the peak output power of 5.2 dBm and efficiency of 30.6% over 902–928 MHz while dissipating 210 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> in the phase-locked loop (PLL) for 0.9 V supply. All spur component levels stay below −41 dBm with the worst harmonic distortion of −48.5 dBc. The proposed TX achieves 100 kbps of data rate for the BFSK modulated signals with the corresponding FSK error of 3.2%.

FPGA Implementation of Digital Modulation Schemes Using Verilog HDL

Abstract: This paper describes the design and development of an FPGA-based digital Modulation Scheme for high-resolution Communication Application. We are focusing on implementation of Verilog based code simulation for fundamental and widely used digital modulation techniques such as Binary Amplitude-shift keying (BASK), Binary Frequency-shift keying (BFSK), Binary Phase-shift keying (BPSK) and Quadrature Phase Shift Keying(QPSK). In this work the idea of sinusoidal signals that have been generated is plain sailing in nature and based on fundamentals of signal sampling and quantization. Such concept of sinusoidal signals generation is not unfamiliar but somehow simplified using sampling and quantization in time and amplitude domain, respectively. The whole simulation is done on Modelsim and Xilinx-ISE using VERILOG Hardware descriptive language. The work has been accomplished on Thirty two bit serial data transmission with self-adjustable carrier frequency and bit duration length.

MOSFET-Based Memristor for High-Frequency Signal Processing

This research article proposes a floating memristor emulator configuration based on n-type MOSFETs only. The proposed memristor comprises three nMOS and an extra nMOS for an external grounded capacitor. Compared to the existing literature, the proposed floating MOS memristor enables a simple design without any sophisticated design complexity. The actual fingerprint of the memristor as a pinched hysteresis loop with different frequency domains and composite characteristics as incremental and decremental are well examined using computer simulation with 90-nm CMOS technology parameters for MOSFETs. The power consumed by the proposed circuit is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.6~\mu \text{W}$ </tex-math></inline-formula> . In addition, an experimental test using off-the-shelf components is investigated to verify the theoretical and simulated results. Moreover, the proposed nMOS-memristor emulator application is suitable for the modulation and demodulation of binary frequency-shift keying (BFSK) and Boolean logic gates.

Modulation Mode Recognition Method of Non-Cooperative Underwater Acoustic Communication Signal Based on Spectral Peak Feature Extraction and Random Forest

The modulation mode recognition of non-cooperative underwater acoustic (UWA) communication signal faces great challenges due to the influence of the UWA channel and the demand for efficient recognition. This work proposes a recognition method for UWA orthogonal frequency division multiplexing (OFDM), binary frequency shift keying (2FSK), four-frequency shift keying (4FSK), and eight-frequency shift keying (8FSK) by using spectral peak feature extraction combined with random forest (RF). First, a new spectral peak feature extraction method is proposed. In this method, pre-processing, waveform optimization, and feature extraction are used to ensure that the extracted feature maintains high robustness in the UWA channel. Then, we designed an RF classifier that can meet the demand for high-efficiency recognition and good performance. Finally, simulation and experimental results verified the feasibility of the recognition method.

A 0.3-to-1-GHz IoT Transmitter Employing Pseudo-Randomized Phase Switching Modulator and Single-Supply Class-G Harmonic Rejection PA

A wideband Internet of Things (IoT) transmitter (TX) employing open-loop binary frequency-shift keying (BFSK) modulator with a pseudo-randomized phase transition (PRPT) time and a single-supply Class-G harmonic rejection (HR) power amplifier (PA) is presented. The proposed open-loop phase switching modulator eliminates the data-rate limitation in a conventional phase-locked loop (PLL)-based closed-loop modulator, while the PRPT scheme increases the effective phase resolution with a better power efficiency than delta–sigma modulation (DSM)-based randomization. Thus, a low spur level below −40 dBc is achieved with only a 4-bit phase resolution. The Class-G HR PA, including a four-level supply voltage waveform generator, is proposed as a high-efficiency and low spurious PA architecture. The proposed HR PA presents the third- and fifth-harmonics cancellation over the 0.3-to-1-GHz band, while only a single supply is required for Class-G implementation of the HR PA. The proposed BFSK TX is implemented in a 55-nm CMOS process. Measured with a 0.3-to-1-GHz continuous-wave carrier, TX output power and PA drain efficiency are 2.7 ± 0.2 dB and 52% ± 3%, respectively, operating from a 0.9-V supply. The HRs of −31.4/−42.7 and −28.2/−42.4 dBc at the third/fifth harmonics are measured at the lowest (0.3 GHz) and the highest (1 GHz) carrier frequencies, respectively. With a data rate of 1 Mb/s, the measured FSK errors are 3.6% and 4.2% at both ends of the operating frequency.

Underwater Acoustic Communication With Multicarrier Binary Frequency Shift Keying

This article describes a novel approach for robust and reliable underwater acoustic communication targeting low data rate applications in very challenging channels. The well-known binary frequency shift keying (BFSK) modulation is extended with multiple pair-wise BFSK subcarriers forming a multicarrier (MC) waveform referred to as MC-BFSK. Time offsets between neighboring subcarriers combined with windowing and guard periods are employed to increase the robustness against Doppler-induced frequency spread/shift and reverberation together with novel methods for synchronization, peak-to-average-power ratio reduction, and soft-value extraction. For the design of the parameters of the waveform, a heuristic approach is utilized. A noncoherent matched filter receiver with spatial diversity is adopted. The MC-BFSK transmission scheme is evaluated by means of computer simulations as well as sea-trial measurements. The obtained results are compared with competing modulation schemes where the proposed MC-BFSK shows better performance in challenging channels. In particular, we are able to decode frames in a sea-trial scenario where the direct path between the transmitter and the receiver is blocked by an island.

Blind Separation for Wireless Communication Convolutive Mixtures Based on Denoising IVA

In wireless communication systems, signal transmission through a channel can not avoid the influence of noise. When it reaches the receiver, it is accompanied by time delay and attenuation. Therefore, the observed mixture signals at the receiver are convolutional mixed signals with noise contamination. To solve the problem of traditional frequency-domain based convolutive blind signal separation methods have poor separation performance for convolutional mixed signals with noise, this paper propose a denoise-FastIVA method to separate convolutional mixed signals with noise. The basic principle is to use a wavelet transform to denoise the observation signal, reduce the effect of noise on the separation effect of the algorithm, and enhance the robustness of the fast fixed-point independent vector analysis (FastIVA) separation algorithm to noise. Simulation experiments show the effectiveness of a denoise-FastIVA, under the condition that the baseband signal of binary phase shift keying (BPSK) and binary frequency shift keying (2FSK) signal modulation signal is 10 bits respectively,the separation accuracy of linear frequency modulization (LFM) has increased from 87% to more than 94%; BPSK has risen from 83% to over 97%; 2FSK has improved from 81% to over 95%. When the SNR is greater than 10 dB, the separation similarity of denoise-FastIVA for the communication mixed signals is more than 90%, and the demixing signal can demodulate the baseband signal completely and correctly. Baseband signals of experimental BPSK and 2FSK signal modulation signals are 100 bits respectively. When the signal-to-noise ratio is greater than 5dB, the signal separated by denoise-FastIVA method has the highest similarity coefficient with the source signal, and the bit error rate (BER) of the separated BPSK signal and the separated 2FSK signal are the lowest, compared with the traditional frequency domain demixing method and FastIVA algorithm.

Efficient ULF Transmission Utilizing Stacked Magnetic Pendulum Array

A novel stacked magnetic pendulum array (MPA) is proposed as an antenna for efficient transmission in ultralow frequencies (ULF). The MPA structure consists of an array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m\times n}$ </tex-math></inline-formula> magnets stacked in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> rows (m magnets of the same magnetization per row) and a solenoid that encompasses the array. The magnetic flux generated by the solenoid couples to the magnets through a mechanical motion and creates a strong time variant magnetic field at the resonance frequency of the array. The proposed MPA is developed utilizing bearings with extremely small damping which hold the magnets, enable efficient oscillation, and guarantees a high-quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor). A comprehensive analysis to study the performance of the MPA and a conventional solenoid will be provided and accordingly, characteristics of an arbitrary <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m\times n}$ </tex-math></inline-formula> array in terms of field strength, resonance frequency, transmission efficiency and inductance are studied. Furthermore, a figure of merit (FOM) is introduced as the ratio of efficiency to the maximum linear dimension of the antenna. The experimental results for a fabricated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5 \times 11$ </tex-math></inline-formula> array show a resonance frequency of 715 Hz and a Q-factor of 94 while the maximum linear dimension of the antenna is just 9 cm. Moreover, measurement results show 24.9 dB improvement in the transmission efficiency of the MPA compared to the efficiency of a single solenoid of the same dimensions. The MPA has the FOM of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.26\times 1}{0}^{{4}}$ </tex-math></inline-formula> which is noticeably higher than that of proposed antennas in the literature. To demonstrate broadband transmission with the MPA, a binary frequency shift keying (BFSK) signal is transmitted through the use of direct antenna modulation (DAM) at a rate of 18 bps.

Wireless-optical-communication-based cooperative IoT and IoUT system for ocean monitoring applications.

This paper proposes the idea of a new cooperative communication between the Internet of Things (IoT) and the Internet of Underwater Things (IoUT) using wireless optical connectivity for ocean monitoring applications. We considered IoT communication using a hybrid radio frequency (RF)/free space optical (FSO) link and IoUT using a underwater wireless optical communication (UWOC) link. Channel models for RF, FSO, and UWOC links are considered to be Rayleigh, Malaga with pointing errors, and hyperbolic tangent log-normal distributions, respectively. The outage probability and the bit error rate (BER) expressions for the proposed system are derived over the combined channel model, which includes the effects of attenuation, turbulence, and pointing errors. The BER results are plotted for various binary digital modulation schemes such as on-off keying, binary phase-shift keying, binary frequency-shift keying, and differential phase-shift keying over UWOC, hybrid RF/FSO and RF-UWOC, FSO-UWOC with end-to-end systems. BER results are extended for various turbulence regions and pointing errors of the FSO link. Monte Carlo simulation results authenticate the correctness of the results.

An Ultralow-Power OOK/BFSK/DBPSK Wake-Up Receiver Based on Injection-Locked Oscillator

This article presents a high-sensitivity and high energy efficiency wake-up receiver (WuRx) based on an injection-locked oscillator (ILO) and an envelope detector to provide the capabilities of reliable demodulation for ON-OFF keying (OOK), binary frequency shift keying (BFSK), and differential binary phase shift keying (DBPSK) demodulation schemes. A 54- μW 433-MHz multimode WuRx is implemented in a 0.18- μm CMOS process. For a data rate of 200 kb/s and a bit error rate (BER) <; 0.1%, the receiver achieves sensitivities of -80/-78/-77 dBm under the OOK/BFSK/DBPSK demodulation schemes, respectively. Furthermore, incorporating an external loop antenna with a reception of an ILO, the receiver features a low-power mode of just 11 μW with a sensitivity of at least -71 dBm.