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In this letter, an energy-efficient and low complexity method for capacitive-coupled human body communication (CCHBC) systems is proposed. In the proposed method, called impedance shift keying CC-HBC (ISK-CC-HBC), the change of impedance between the transmitters signal and the ground electrode is used to map information. In particular, the transmitter changes the condition of an electrical field generated by the receiver, by changing the impedance between its signal and ground electrodes. Subsequently, by detecting the changes in the electric field, the receiver can demodulate the information sent by the transmitter. The CC-HBC channel is obtained using the transfer function method, while the performance of the proposed scheme is compared with frequency shift keying (FSK) and on-off keying (OOK) modulations.

Due to the severe impact of dynamic plasma sheath on electromagnetic (EM) waves, the communication quality of hypersonic vehicles deteriorates, even resulting in communication blackouts during the reentry process. In this article, the hypersonic vehicle downlink integrated channels that cascade the plasma sheath channel and Rice fading channel, i.e., the downlink telemetry channels, are first established, and then the demodulation method and performance of typical telemetry modulations including the M-ary phase shift keying (MPSK), M-ary amplitude shift keying (MASK), and M-ary frequency shift keying (MFSK) are studied. Considering the high dynamics of the plasma sheath, the pilot signals are used to detect the signal correctly for MPSK, and the non-coherent demodulation is adopted for MASK and MFSK. Especially, an adaptive maximum likelihood (ML) receiver for ASK is proposed based on a reduced reversible jump Markov chain Monte Carlo (RRJ-MCMC) algorithm to estimate the probability density function (pdf) of the received signal. The simulation results show that the communication performance of PSK and ASK is improved with the modulation order $M$ decreasing; the performance of non-coherent FSK is improved with the modulation order $M$ increasing. Meanwhile, the performance follows the order of NC-MFSK (M ≥ 8) > BPSK > NC-4FSK > NC-2FSK > 2ASK. For NC-8FSK, when the electron density peak value ${Ne}_{\mathrm {peak}}$ = {2, 4, 6, 8, 10} $\times 10^{18}\,\,\text{m}^{-3}$ , the signal to noise ratio (SNR) required to reduce the bit error rate (BER) to 10−6 are 17, 18, 19, 21, and 34 dB, respectively.

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- $\mu \text{W}$ 433-MHz multimode WuRx is implemented in a 0.18- $\mu \text{m}$ CMOS process. For a data rate of 200 kb/s and a bit error rate (BER) $11~\mu \text{W}$ with a sensitivity of at least −71 dBm.

This article presents an RF receiver (RX) designed to exploit the inherent SNR advantage offered by non-coherent 16-FSK modulation relative to more conventional non-coherent modulation schemes, such as FSK and OOK. Specifically, this article demonstrates that when demodulated using two-pole bandpass filters, 16-FSK offers a 4-dB sensitivity advantage compared with binary frequency shift keying (BFSK), at the cost of reduced spectral efficiency at the same data rate. This article then presents the design of a 16-FSK-compatible RX front end, which performs demodulation through 16 $N$ -path filters driven by temperature-stabilized phase-locked loops to ensure calibration-free filter center frequency control, along with augmented Miller capacitors for tight area-constrained bandwidth control. Implemented in 65-nm CMOS, the RX consumes 0.6 mW from a 0.5-V supply while achieving a sensitivity of −103.2 dBm at 100 kb/s, for a power-sensitivity-data-rate figure of merit of 185.2 dB, which represents a 3.2 dB advance over state of the art.

This brief presents a 2.4-GHz crystal-less GMSK/GFSK phase-tracking receiver (PTRX) that employs a multiphase bang-bang PLL (BBPLL) as an auxiliary loop to perform multibit oversampled demodulation. A divider-less 30-MHz BBPLL with a 16-stage ring voltage-controlled oscillator (VCO) and 15 bang-bang phase detectors (BBPDs) works as a clock-less phase-to-digital converter (PDC) and improves demodulation SNR with control polarity reversal and frequency scaling. A prototype 2.4-GHz PTRX with the reference-less BBPLL is implemented in 65 nm and performs 1-Mb/s GMSK demodulation with −84-dBm sensitivity. Experimental results show that the proposed receiver can achieve high slew-rate transient performance for increased frequency deviation with the multiphase BBPLL-based demodulation.

We propose a novel simulation approach of the Middleton Class-A model for impulsive noise generation considering symbol-wise transmission in a real Power Line Communication environment. Then, we validate the proposed approach for both single carrier binary FSK based—and multi-carrier OFDM-based communication systems. Established analytical formulations and obtained simulation results for the impulsive noise variance distribution and the communication system error probability show that in a binary FSK system, the second order of the noise variance per symbol, as well as the error floor, are closely related to the impulsive index A. The error floor decreases when A becomes large, and its asymptotic value is equal to the Bit Error Rate (BER) for an additive white Gaussian noise channel with noise variance equal to the average variance of the impulse noise. However, in an OFDM-based system, the noise variance per symbol at the output of the demodulator, as well as the error floor in the BER curves, are fixed and independent of the impulsive index A. The proposed analysis allows us to compare binary FSK and OFDM under the same theoretical noise conditions.

In this paper, we investigate a multitone simultaneous wireless information and power transfer (SWIPT) based modulation scheme for battery-less Internet of Things (IoT) nodes that works in the ultra high frequency (UHF) region. The conventional SWIPT system is assumed to have power-consuming communication modules. Having such modules on to the IoT nodes whose power is harvested from radio frequency (RF) power sources is too unrealistic. In addition, waveform design from the aspect of power harvesting through SWIPT still has room for consideration. Recent studies have explored multitone based SWIPT to increase the power conversion efficiency (PCE). In these schemes, information is modulated by changing each tone’s nature or varying the number of tones. Among these methods, we focused on modulation schemes known as frequency-shift multitone based SWIPT, which shifts frequencies among the tones for information encoding. Unlike previously proposed methods where demodulation requires some power-consuming fast Fourier transfers (FFTs), especially under small communication bandwidths, we applied a signal detection method by measuring output peak to average power ratios (PAPRs) for frequency-shift multitone based SWIPT to reduce power consumption. Based on our analysis, different tone configurations in the frequency domain would yield varieties of nonlinear outputs during the rectification process. In addition, these specific nonlinear output patterns depend on the tone configurations. With this feature, it is possible to demodulate in the time domain at the receiver side using PAPR based measurements, which could eliminate FFT operation. This paper describes how measuring PAPRs enables the detection of signals in theory and validates this through simulations and experiments. We also estimate the communication rates. Based on our results, we achieved 0.46 bits/s/Hz when the number of tones was 6 and estimated that there were $(N-1)(N-2)/2 + 1$ different PAPRs from a given multitone waveform whose number of tones was $N$ .

This letter presents a sub-6-GHz 100-Mb/s receiver that employs a fully balanced FSK, namely, a binary frequency-domain OOK (BFOOK) modulation. Demodulation is done based on a delay-line FM demodulator and a sideband energy detection (SB-ED) circuit with reduced noise bandwidth by leveraging a fully balanced BFOOK feature. A prototype 3.5-GHz receiver based on the proposed architecture is implemented in 65-nm CMOS. The receiver performs 100-Mb/s BFOOK demodulation and consumes 24.3 mW with the sensitivity of −62 dBm, achieving high energy efficiency of 243 pJ/b.

We are interested in a communication system that operates under stringent power constraints, but is flexible with bandwidth constraints. Our approach is to consider some of the key elements in a transceiver and optimize them for low power consumption, as opposed to optimizing them to minimize, say, average probability of error. An obvious consequence of this is that high complexity components of the system, such as matched filters, forward error correction that employs iterative decoders, coherent demodulators, and bandwidth-efficient modulation formats, are not feasible for this research. Rather, our system is designed using $M$ -ary FSK with non-coherent detection, optimized two-pole bandpass filters (BPF), and Reed-Solomon (RS) codes with hard-decision decoding. Among other things, we show that by properly optimizing the key parameters of the BPFs and RS codes, we can design the system to be significantly less complex than an optimal one, and only lose about 1.2 ( $M$ =16) to 1.5 ( $M$ =2) dB in terms of performance.

Digital modulation is the technique in which the discrete changes in a message signal are imposed onto parameters (amplitude, frequency, or phase) of a sinusoidal carrier wave. This chapter summarizes the essentials of digital transmission and shows how to assess the quality of a digital transmission by revisiting the mathematical foundation for calculating the probability of error, employing the bit error rate metric, and acquiring knowledge of the eye diagram. It introduces binary shift‐keying modulation in digital transmission and describes the modulation and demodulation principles of amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK) modulations. The chapter shows how to assess the transmission quality of ASK, FSK, and PSK. It also discusses the advantages, shortcomings, and applications of ASK, FSK, and PSK.

A low-power and small chip-area multi-rate human body communication (HBC) discontinuous-phase FSK (DPFSK) transceiver applied for wearable devices is presented. The transceiver is implemented in UMC $0.18~\mu \text{m}$ CMOS process with a small chip area of only 0.46 mm2. DPFSK modulation is adopted to reduce the hardware complexity of the transceiver. In the receiver, a direct-conversion front-end is adopted to eliminate polarization voltage of the electrode-skin interface. A delay line (DL)-based variable phase shifter used in the demodulator of the receiver is proposed for accomplishing of multi-rate DPFSK demodulation. In the transmitter, a digital frequency interpolator is adopted for achieving multi-rate DPFSK transmission. At a data rate of 1 Mb/s, the receiver and the transmitter consume the power of 1.79 mW and $700~{\boldsymbol{\mu }}\text{W}$ , respectively. Therefore, energy consumption per received and transmitted bit are 1.79 nJ/bit and 0.7 nJ/bit, respectively.

Frequency-hopped M-ary frequency-shift-keyed (FH-MFSK) has the ability to handle with long multipath, large Doppler spreads, high ambient noise and rapid phase fluctuation, and is proved to be a robust modulation scheme in mobile shallow underwater acoustic channels. Aiming at this topic, a convolutionally encoded FH-MFSK modulation scheme with a novel iterative multi-channel reception is proposed. To obtain the novel reception suitable for non-coherent M-ary frequency-shift-keyed, the ideas of iterative multi-channel demodulation and decoding are combined and extended. A modified multi-channel soft-input–soft-output demodulator based on maximum-a-posterior criterion is derived, and substantial gains of several decibels in power efficiency are achieved. Extra gain can be obtained by utilising time diversity with long multipath delay. Simulation shows that a non-coherent receiver equipped with five arrays obtains around 5.5 dB gain over the single non-iterative receiver. A shallow water field testing at Songhua Lake with 300 m distance confirms that the proposed receiver verifies its robustness and usability.

Noncoherent demodulation is an attractive choice for many wireless communication systems. It requires minimal protocol overhead for carrier synchronization, and it is robust to radio impairments commonly found in low-cost transceivers. Machine learning techniques, such as neural networks and deep learning, offer additional benefits for these systems. Practical communication systems often include nonlinearities, non-stationarity, and non-Gaussian noise, which complicate mathematical derivation of optimum demodulators. Learning approaches can optimize demodulator performance directly from simulated or measured radio data, which is often plentiful in the design and verification of today's integrated transceivers. This paper examines several candidate neural network topologies for use in noncoherent demodulation and provides a mathematical framework for their comparison. Each is based on a complex-valued feature detection layer, which may be characterized as coherent or noncoherent, followed by one or more real-valued classification layers. Backpropagation equations for the noncoherent feature layer include a synchronization term that facilitates training with noncoherent input data. The coherent layer does not synchronize training data, however a noncoherent demodulator can still be constructed by increasing the coherent layer capacity and adding a max pooling layer to marginalize the unknown signal phase. A frequency classification example highlights the differences between the topologies and confirms that optimum noncoherent demodulation can be learned in the presence of AWGN and random phase offsets. The topologies considered here are suitable for noncoherent demodulation of power-efficient modulations such as FSK and ASK, which are typical in today's short-range wireless communication systems. It is hoped that such topologies will lead to a future common architecture that can support the wide range of modulation formats in this space.

In the scenarios of non-cooperative wireless communications, automatic modulation recognition (AMR) is an indispensable algorithm to recognize various types of signal modulations before demodulation in many internet of things applications. Convolutional neural network (CNN)-based AMR is considered as one of the most promising methods to achieve good recognition performance. However, conventional CNN-based methods are often unstable and also lack of generalized capabilities under varying noise conditions, because these methods are merely trained on specific dataset and can only work at the corresponding noise condition. Hence, it is hard to apply these methods directly in practical systems. In this paper, we propose a CNN-based robust automatic modulation recognition (RAMR) method to recognize three types of modulation signals, i.e., frequency shift key (FSK), phase shift key (PSK), and quadrature amplitude modulation (QAM). The proposed method is trained on a mixed dataset for extracting common features under varying noise scenarios. Simulation results show that our proposed generalized CNN-based architecture can achieve higher robustness and convenience than conventional ones.

This paper presents an ultra-low-power receiver based on the injection-locked oscillator (ILO), which is compatible with multiple modulation schemes such as on-off keying (OOK), binary frequency-shift keying (BFSK), and differential binary phase-shift keying (DBPSK). The receiver has been fabricated in 0.18- $\mu \text{m}$ CMOS technology and operates in the ISM band of 2.4 GHz. A simple envelope detection can be used even for the demodulation of BFSK and DBPSK signals due to the conversion capability of the ILO from the frequency and phase to the amplitude. In the proposed receiver, a $Q$ -enhanced single-ended-to-differential amplifier is employed to provide high-gain amplification as well as narrow band-pass filtering, which improves the sensitivity and selectivity of the receiver. In addition, a gain-control loop is formed in the receiver to maintain constant lock range and hence frequency-to-amplitude conversion ratio for the varying power of the BFSK-modulated receiver input signal. The receiver achieves the sensitivity of −87, −85, and −82 dBm for the OOK, BFSK, and DBPSK signals respectively at the data rate of 50 kb/s and the BER lower than 0.1% while consuming the power of $324~\mu \text{W}$ in total.

A transmitter (TX)/receiver (RX) pair using galvanic coupling to achieve in-body to on-body body channel communication (I2O-BCC) for ultra-low power (ULP) miniaturized implanted applications is presented. The I2O-BCC enables low loss communication ( in vivo communication distance using the body as a transmission medium. Injection locking (IL)-based frequency-to-amplitude (F2A) conversion demodulator is proposed in RX. It can handle more than 20% frequency variations exhibited by the TX frequency-shift keying (FSK) signals due to the lack of accurate off-chip reference. The packaged implanted TX measures $7\,{\times }\,7\,{\times }\,2$ mm3. It contains a micro-battery, two micro-probes, and the designed SoC in 130-nm CMOS process. The in-body TX radio block consumes only 8.6 $\mu \text{W}$ at 500 kb/s with an on-chip power management unit that exhibits a 45% power efficiency, while the on-body RX consumes 591.5 $\mu \text{W}$ . The TX radio block power is 8 $\times $ lower than previous works and achieves energy efficiency at 17.2 pJ/b with minimal bill of material (BOM).

There are two main types of optical signals propagating in wired or wireless communication links: time continuously varied or analog, which corresponds to narrowband channels, and time discrete varied or pulse‐shaped, which corresponds to wideband channels. Therefore, there are different types of modulation that are usually used for such types of signals. This chapter defines the process of modulation and demodulation. It describes the main principle of both kinds of modulation, analog and digital, and provides some examples of the most useful types of modulation adapted for both kinds of channels, narrowband and wideband. There are three types of modulation, depending on what characteristic is time varied in the modulating signal – amplitude modulation, phase modulation, and frequency modulation. There are three kinds of digital modulation: amplitude shift keying, frequency shift keying, and phase shift keying.

For generating digital codes based on the frequency of input signal we need frequency shift keying demodulators. Optical demodulators are required for optical communication networks. In this paper we are going to design and propose a new structure for implementing all optical frequency shift keying demodulator. The proposed structure was designed using four resonant rings. Finite difference time domain method was used for simulating the propose structure. The simulation results show that when the frequency of input signal is 193.5 THz, 194 THz, 194.5 THz and 195 THz the proposed structure can generate 00, 01, 10 and 11 code at the output ports respectively. The maximum delay time of the proposed structure is 2 ps.

OFDM systems are challenged by the time variability of mobile acoustic channels where the Doppler effect can be high enough that the received signal experiences non-negligible residual frequency offset, as well as channel time variability, which cause intercarrier interference (ICI). To mitigate these effects, we introduce an efficient yet computationally manageable two-stage algorithm that counteracts the frequency offset as well as the time selectivity of mobile acoustic channels. In the first stage, frequency offset is compensated using a practical approach based on differentially coherent detection which keeps the receiver complexity at a minimum and requires only a small pilot overhead. In the second stage, a method referred to as partial FFT demodulation is used to tone down the time variability of the broadband acoustic channel. Towards this goal, the time interval of one OFDM block is divided into several partial intervals, giving the channel less chance to change over each shorter interval, and demodulation is performed in each interval separately. The partial demodulator outputs are then combined before applying a coherent detection algorithm where refined channel estimation and data detection take place. Using the experimental data transmitted over a 3–7 km shallow water channel in the 10.515.5 kHz acoustic band, we study the receiver performance in terms of data detection mean squared error (MSE), and show that the proposed algorithm provides excellent performance, surpassing all our previously tested approaches.

This article presents a multi-receiver cross-correlation technique for (B)FSK receivers, targeting wireless sensor network applications. Here, multiple receiver outputs are pair-wise cross-correlated and the correlated output samples are averaged to lower the noise floor at the receiver output. Compared to a two-receiver cross-correlation, multi-receiver cross-correlation generates more cross-correlated output samples in a given time. Hence it requires a shorter measurement time for a desired noise floor reduction and facilitates a higher data rate for (B)FSK operation. Compared to a single receiver, it improves the linearity and the harmonic interferer tolerance using passive splitters and different LO frequencies in the receiver paths respectively. These theoretical insights are verified with measurements for the first time using a 2- and 3-receiver cross-correlation in a BFSK receiver. Operating at 1GHz and with a data rate of 200kbps, the demonstrator, using sub-mW mixer-first receiver front-ends for power efficiency, achieves −102dBm sensitivity and >40 dB rejection for both narrow and wideband harmonic interferers without any RF filters.

This work considers the possibility of improving the noise immunity of incoherent reception of DPSK and FSK signals. The considered method of blind separation of signals, based on bringing the joint cumulants of higher orders to zero, is presented. Algorithms for incoherent modulation and demodulation of DPSK and FSK signals are described. The simulation of reception of signals with different sizes of the alphabet of the transmitted symbols is carried out. Simulation has shown the efficiency of separating the information signal from interference using the proposed algorithm for blind signal separation.

At present, most of the hopping frequency spread spectrum (HFSS) communication systems adopt the non-coherent demodulation method regarding the low complexity receiver design, whereas seldom of them adopts the coherent demodulation method. This paper explores the performance boundary of coherent frequency hopping spread spectrum system in terms of slow to fast frequency hopping. Specially, we design a coherent fast frequency hopping communication system, and build its corresponding system model. By adopting the maximum likelihood method, we achieve the coherent maximum likelihood receiver. Furthermore, the BER performance of fast frequency hopping system is analyzed theoretically, where binary phase shift keying (BPSK) is adopted. We use the frequency diversity under partial band noise jam (PBNJ) model and give the closed form solution of BER performance. Finally, the relationship between BER and the number of frequency diversity is analyzed under jamming and non-jamming conditions.

The article examines the efficiency of the blind source separation algorithm in the task of FSK signal detection. Classical algorithms of blind source separation and criterias of independence of signals are examined. The model of the second and fourth cumulants blind source separation algorithm is described. To eliminate the trivial result, additional boundaries are used on signal variance. A system of equalities is provided to find the ratios of the stirring matrix. The family of uncorrelated solutions of the unmixing matrix is presented. It is shown how to estimate solution which leads to fourth cumulants of output signals equal to zero. Examined in the paper FSK modulation and demodulation model is presented. The efficiency of using the BSS method in the task of receiving the FSK signal with the white Gaussian noise was shown.

MSK is often used in communication, but most of them are for detailed inference. In order to study the digital realization of minimum frequency shift keying (MSK) and its principle. It is analyzed according to the principle of digital up-conversion (DUC), digital down-conversion (DDC) and filtering technology, and verified by simulation with MATLAB. Finally, it is realized by Verlig HDL language on FPGA (Field-Programmable Gate Array), and the feasibility and system parameters of the scheme are determined.

Clock and data recovery system (CDR) for PAM-4 signal for a short-range 27-MHz FSK radio is reported. For conceptual demonstration purpose, both CDR and RF circuits and systems have been experimentally verified with low-cost discrete component implementation. The basic principle in performing clock recovery from PAM-4 is by converting a PAM-4 signal into an NRZ (PAM-2) before further applying it to the three well-established CDR architectures. The technique can be simply extended to recover a clock signal from any PAM-m signal. The PAM-4 signal is modulated into a 4-FSK signal using a voltage-controlled oscillator with a 27-MHz carrier frequency. The class-A BJT-based power amplifier with 40%-PE has been employed to drive a spiral FR-4 PCB antenna. The inductive-generation low-noise amplifier with a peak voltage gain of 22dB and Q of 7 is employed to amplify the incoming signal before performing FSK demodulation to recover the PAM-4 signal. The transmission and CDR symbol rates are 31-155ksymbols/s for simple and Alexander CDRs and 90-117ksymbols for a Hogge CDR at the radio transmission range of 7 meters.

The LoRa modulation scheme is becoming one of the most adopted Internet of Things wireless physical layer due to its ability to transmit data over long distances with low power requirements. Typical demodulation techniques for LoRa utilize variants of non-coherent Frequency Shift Keying demodulation. This paper aims to capitalize on the robustness of deep learning techniques, specifically by using convolutional neural networks to demodulate LoRa symbols. We achieve this by building a dataset consisting of emulated time-domain LoRa symbols across a range of channel impairments; namely, we examine additive white Gaussian noise together with carrier frequency offset and time offset. The presented results show an improvement when utilizing deep learning over typical non-coherent detection while performing very close to the optimal matched filter.

This paper presents a 4-b phase-domain analog-to-digital converter (ADC) that utilizes the time-domain reference generation scheme for low-power operation. Rather than prior arts that rely on power-hungry resistive/current combiners or the IQ-assisted binary-search algorithm with large power T&H circuits for the reference generation, this design benefits from the fully dynamic power characteristic of the time-domain operation, thus leading to an energy-efficient phase ADC design. By introducing several on-chip calibration techniques, the design achieves good robustness with the proposed time-domain operation. The prototype is fabricated in the standard 65-nm CMOS technology, achieving an ENOB of 3.42 bits at 1 MS/s with near Nyquist input, while dissipating $7~\mu \text{W}$ from a 1-V supply. It leads to a 1.36-pJ/conversion-step Walden Figure of Merit at Nyquist input (FoM@Nyquist).

This paper presents a 4-GHz FM ultra-wideband (UWB) transceiver designed for the Internet of Things and body area network applications. Robustness to interferers and low power spectral density allow FM-UWB to coexist with narrowband radios, while large signal bandwidth strongly relaxes constraints on the frequency synthesis blocks enabling the full integration of the radio at low power. The transceiver, integrated with a 65-nm standard CMOS technology, consists of a transmitter and two receivers that provide two modes of operation. The transmitter consumes 575 $\mu \text{W}$ while transmitting a 100-kb/s signal at 4 GHz at an output power of −11.4 dBm. A single RF IO pad is used and the fully integrated matching network is shared among the transmitter and the receivers. The low-power receiver consumes 267 $\mu \text{W}$ and provides a single communication channel at 100 kb/s in the 4-GHz band, with a −57-dBm sensitivity. The second receiver provides a better performance and takes full advantage of the FM-UWB features, as it implements wireless communication with up to four parallel channels sharing the same RF band. It consumes 550 $\mu \text{W}$ and provides −68-dBm sensitivity at 100 kb/s per channel. The FM-UWB architecture can tolerate a very large reference frequency offset of up to ±8000 ppm. This unique feature potentially allows for a quartz-free synthesizer, resulting in a radio with no off-chip components.

We consider a non-coherent index-modulation system, where the information is transmitted only through index selection. We first obtain a decision metric for the optimal maximum-likelihood demodulation in the Rayleigh fading channels and then analyze the system performance in terms of pair-wise error probabilities. This analysis leads to a simple quantity that can be used as both performance metric and design criterion for the system. We also derive the approximations for the error probabilities at high signal-to-noise ratio and show that the diversity order of the considered system is one. Finally, we present the simulation results to corroborate our analytical findings.

This paper describes a low-power phase-domain receiver with single-bit phase-to-digital conversion by utilizing a divider-less bang-bang phase-locked loop (BBPLL). The BBPLL performs 1-bit oversampled noise-shaping demodulation as a secondary loop in the receiver, offering a flexible gain control as well as a simple baseband interface. A prototype 2.4-GHz receiver with an auxiliary 50-MHz BBPLL is implemented in 65-nm CMOS. In the RF loop, a dual-path LC voltage-controlled oscillator (VCO) with partitioned coarse tuning is designed to have a low gain constant over temperature variation. In the BBPLL, a dual-input ring VCO provides separate gain control and low-pass filtering for the demodulation path. The receiver performs 100-kb/s Gaussian Frequency Shift Keying (GFSK) demodulation with the sensitivity of −89 dBm and the power consumption of 3.7 mW from a 0.8-V supply in which 0.15 mW is consumed by the BBPLL.

This paper proves that 2.45- and 5.8-GHz band continuous-wave magnetrons can be used to perform amplitude, phase, and frequency modulations by applying an injection-locking method. The magnetron behaved like an amplifier, and its output could follow the injection signal. In addition, we have achieved the transmission of amplitude-shift keying data at 200 kb/s as well as phase-shift keying and frequency-shift keying at 10 Mb/s. Moreover, we quantitatively discussed several demodulation performances of the injection-locked magnetrons. Finally, the transmission of audio and video information was demodulated using the injection-locked magnetrons.

This paper presents a 1.7-mW low-intermediate-frequency receiver design for Bluetooth low-energy (BLE) applications. The design exploits particular aspects of BLE, such as the relaxed in-band interference characteristics, more precisely the $C/I_{1~\textrm {MHz}}$ , and the relatively high-frequency-shift keying modulation index, to deliver a high level of energy efficiency and simplicity to the receiver baseband architecture. Reliable quadrature signals are generated in the RF signal path without consuming energy, which is supported by an inverter-based low-noise amplifier (LNA) that achieves high gain and low noise figure under low-power budgets. A small-signal analysis of low-power inverter-based LNAs is presented offering simple design equations. Seeking an affordable solution, the fabricated prototype is fully integrated into an earlier generation CMOS technology node ( $0.13~\mu \text{m}$ ), occupying a silicon area smaller than 0.7 mm2. The receiver achieves a sensitivity level of −92 dBm while consuming 1.41 mA from a 1.2-V supply.

Another scheme of a binary frequency phase shift keying (BFSK) signal demodulation has been presented in this paper. The proposed demodulated scheme utilizes an ANC-based adaptive signal processing. The adaptive algorithm which adapts the coefficients of the ANC system will be constrained in adaptation sequence corresponding to each symbol interval of the received BFSK signal. By using this scheme, the system will provide demodulated behavior similar to an integrated and dump correlator of an optimum receiver. The analytical and simulation results have shown that the proposed system can demodulate the received BFSK signal in AWGN channel. Furthermore, the system provides the same performance as the optimum receiver.

International audience; This work presents an instruction-set extension to the open-source RISC-V ISA (RV32IM) dedicated to ultra-low power (ULP) software-defined wireless IoT transceivers. The custom instructions are tailored to the needs of 8/16/32-bit integer complex arithmetic typically required by quadrature modulations. The proposed extension occupies only 2 major opcodes and most instructions are designed to come at a near-zero energy cost. Both an instruction accurate (IA) and a cycle accurate (CA) model of the new architecture are used to evaluate six IoT baseband processing test benches including FSK demodulation and LoRa preamble detection. Simulation results show cycle count improvements from 19% to 68%. Post synthesis simulations for a target 22nm FD-SOI technology show less than 1% power and 28% area overheads, respectively, relative to a baseline RV32IM design. Power simulations show a peak power consumption of 380 µW for Bluetooth LE demodulation and 225 µW for LoRa preamble detection (BW = 500 kHz, SF = 11).

In order to ensure safe and reliable data communication between modern trams and ground control equipment using wireless induction, this paper designs a communication transceiver between tram and ground based on FSK modulation technology. The hardware design of the transceiver adopts the AVR microcontroller AT90CAN128 with CAN controller as the microcontroller, and the ST7540 chip with FSK carrier signal modulation and demodulation to complete the signal adjustment and demodulation. The microcontroller and the modern chip use serial communication. Separate transmitting and receiving circuits complete the signal filtering and amplification functions, the transceiver uses CAN bus to achieve communication with the vehicle bus, and uses the on-board antenna to complete the inductive communication with the ground control equipment. Experiments show that the design has simple structure, high integration, low power consumption, stable operation, can effectively filter out noise signals, realize the modulation and demodulation of the carrier signal, and the communication function with the vehicle bus and the vehicle transceiver antenna.

International audience; This paper investigates modulation schemes for ultrasonic intra-body networks. State-of-the-art Implanted Medical Devices (IMD) are mostly based on On-Off Keying (OOK) which is the simplest type of modulation. However, MATLAB simulations depict the higher power efficiency of Binary Phase-Shift Keying (BPSK) over OOK and other binary modulation techniques. Moreover, at equal Bit Error Rate (BER) and emitted signal power, the higher power efficiency eventually results in a gain of achievable depth that is quantified in water. At last, alternatives to power-hungry Phased-Locked Loop (PLL)-based demodulation circuits are explored as their complex structure generally thwarts the use of BPSK modulation.

The cab signal, as the movement authority of train operation, plays a vital role in ensuring the safety of operation. The booming high-speed and heavy-haul railways lead to larger traction current, as well as various types of locomotive, the electromagnetic environment is getting more serious than before. The track circuit and traction current take the rails as common transmission channel. It is difficult to physically filter out mixed noise in the received signal and demodulate the information correctly since harmonic component of the interference may occupy the same frequency spectrum as useful signal. Under this background, the paper proposes a cab signal anti-interference algorithm based on PSO-optimized (Particle Swarm Optimization) DBN (Deep Belief Network) aimed at these FSK (Frequency shift keying) modulation signals which were interfered in useful band to improve the accuracy of cab signal demodulation. After verified by on-site and simulated data and compared with commonly used machine learning, this algorithm performs well in the demodulation of in-band noisy cab signals demodulation, the average accuracy of the algorithm reaches 99.87%, in addition, the average data process time is about 0.5s based on the TensorFlow platform with the GPU of GeForce MX250.

In order to improve the utilization of frequency band and reduce the effects caused by nonlinear power amplifier, satellite communication has adopted amplitude-phase shift keying (APSK) signals modulation scheme for data transmission. However, APSK is a multilevel modulation and thus complex the demodulation process. This paper provides a Hopfield neural network (HNN) based demodulator to reducing the complexities and enhance the stabilities in demodulating APSK signals. Compared with traditional methods, the HNN based demodulator is faster and more stable for most of the cases in our experiments. Meanwhile, we obtained competing accuracy when using new modulator, and then proves the effectiveness of our work.

This paper studys ASK, FSK and PSK, which are different digital modulation methods of communication system. The experiments are done under two different conditions. In the situation of no noise, the simulation results of simulink show that after modulation and demodulation, the demodulated signal is roughly the same as the original signal. In the sitution of noise, filter is needed to reconstruct the signal.

Wireless Sensor Networks (WSNs) encounters low temporal and/or spatial variation of the sensed physical parameters during a small time interval. In this work, we exploit this high spatial and/or temporal correlation of sensor data to suitably encode multiple data from different sensor nodes, leading to a reduced length of data. We propose a run-length block coding scheme, where in the encoded message, we keep the transmitter in silent mode during the presence of the most predominant symbol ‘0’ and use unique hybrid FSK - ASK based modulation/demodulation technique for the communication process with a non-coherent receiver, that leads to a significant reduction in transmitter & receiver energy. Significant savings in transceiver (CC1100, CC2420) energy is analyzed on real-life dataset by means of CO 2 footprint, leading to a low-cost and supreme sustainable energy-efficient communication model for WSN.

Underwater communication is extremely challenging for small underwater robots which typically have stringent power and size constraints. In our previous work, we developed an artificial electrocommunication system which could be an alternative for the communication of small underwater robots. This paper further presents a new electrocommunication system that utilizes Binary Frequency Shift Keying (2FSK) modulation and deep-learning-based demodulation for underwater robots. We first derive an underwater electrocommunication model that covers both the near-field area and a large transition area outside of the near-field area. 2FSK modulation is adopted to improve the anti-interference ability of the electric signal. A deep learning algorithm is used to demodulate the electric signal by the receiver. Simulations and experiments show that with the same testing condition, the new communication system outperforms the previous system in both the communication distance and the data transmitting rate. In specific, the newly developed communication system achieves stable communication within the distance of 10 m at a data transfer rate of 5 Kbps with a power consumption of less than 0.1 W. The substantial increase in communication distance further improves the possibility of electrocommunication in underwater robotics., IROS2020

The explosive increase in the number of IoT devices requires various types of communication methods. This paper presents secure personal authentication using electrostatic coupling Intra-body communication (IBC) based on frequency shift keying (FSK) and error correction. The proposed architecture uses GPIO for a transmitter and analog-to-digital conversion (ADC) for a receiver. We mplemented FSK modulation, demodulation, data protection, and error correction techniques in the MCU software without applying hardware devices. We used the characteristic that the carrier signal is 50% duty square wave for 1-bit error correction and applied a method of randomly inverting SHA1 hash data to protect user authentication data during transmission. The transmitter modulates binary data using a square wave as a carrier signal and transmits data through the human body. The receiver demodulates the signal using ADC and decrypts the demodulated binary data. To determine the carrier frequency from ADC results, we applied a zero-crossing algorithm which is used to detect edge characteristics in image processing. When calculating the threshold value within the zero-crossing algorithm, we implemented an adaptive threshold setting technique utilizing Otsu&rsquo, s binarization technique. We found that the size of the electrode pad does not affect the signal strength, but the distance between the electrode pad and the skin has a significant effect on the signal strength. Our results show that binary data modulated with a square wave can be successfully transmitted through the human body, and, when 1-bit error correction is applied, the byte error rate on the receiver side is improved around 3.5% compared to not applying it.

BACKGROUND: The frequencies that can evoke strong steady state visual evoked potentials (SSVEP) are limited, which leads to brain-computer interface (BCI) instruction limitation in the current SSVEP-BCI. To solve this problem, the visual stimulus signal modulated by trinary frequency shift keying was introduced. OBJECTIVE: The main purpose of this paper is to find a more reliable recognition algorithm for SSVEP-BCI based on trinary frequency shift keying modulated stimuli. METHODS: First, the signal modulated by trinary frequency shift keying is simulated by MATLAB. At different noise levels, the empirical mode decomposition, singular value decomposition, and synchrosqueezing with the short-time Fourier transform are used to extract the characteristic frequency and reconstruct the signal. Then, the coherent method is used to demodulate the reconstructed signal. Second, in the paradigm of BCI using trinary frequency shift keying modulated stimuli, the three methods mentioned above are used to reconstruct EEG signals, and canonical correlation analysis and coherent demodulation are used to recognize the BCI instructions. RESULTS: For simulated signals, it is found that synchrosqueezing with short-time Fourier transform has a better effect on extracting the characteristic frequencies. For the EEG signal, it is found that the method combining synchrosqueezing with short-time Fourier transform and coherent demodulation has a higher accuracy and information translate rate than other methods. CONCLUSION: The method combining synchrosqueezing with short-time Fourier transform and coherent demodulation proposed in this paper can be applied in the SSVEP system based on trinary frequency shift keying modulated stimuli.

Viterbi algorithm is a commonly used algorithm for Gaussian filtered minimum frequency shift keying (GMSK) demodulation, but there exist some problems such as large delay, high overhead, and data overflow in the hardware implementation. Aiming at the problems of delay and overhead, we propose a novel update rule to optimize the stored transfer-state information table and realize one-step backtracking in this paper. It also ensures the realization of pipeline operation, reduces demodulation delay, and saves hardware resources. Furthermore, we adopt combinational logic to perform pre-decision, which not only satisfies the timing requirements, but also achieves the anti-overflow. The hardware implementation results demonstrate the feasibility and correctness of the design.

This paper provides an alternative to digital filter based frequency detection for multi-frequency shift keying modulation (M-FSK) using field programmable gate array (FPGA) architectures, by providing a hamming space autocorrelation based detector that outperforms the use of digital filters by consuming only 4% of an equivalent filter’s logic resources and no DSP blocks at all, with a detection accuracy of 97% while being non-dependant on Hermitian symmetry, orthogonality or any other radio frequency (RF) signal condition. This detection method supports an inexpensive, reliable and accurate real time data demodulation strategy for flicker-free, high dimming range visible light communications (VLC) multi-user systems.