Frequency Shift Keying Signals Research Articles

Design of Deep Learning Acoustic Sonar Receiver with Temporal/ Spatial Underwater Channel Feature Extraction Capability

In this study, deep learning network technology is employed to solve the problem of rapid changes in underwater channels. The modulation techniques employed are frequency-shift keying (FSK) and the BELLHOP module of MATLAB; they are used to create water with multipath, Doppler shifts, and additive Gaussian white noise such that underwater acoustic receiving signals simulating the actual ocean environment can be obtained. The southwest coastal area of Taiwan is simulated in the manuscript. The results reveal that optimizing the environment by using the virtual time reversal mirror (VTRM) technique can generally mitigate the bit error rates (BERs) of the deep learning network’s model receiver and traditional demodulation receiver. Lastly, seven deep learning networks are deployed to demodulate the FSK signals, and these approaches are compared with traditional demodulation techniques to determine the deep learning network techniques that are most suitable for marine environments.

Improved Frequency Sweep Keying CDMA Using Faster R-CNN for Extended Ultrasonic Crosstalk Reduction

Ultrasonic sensors are inexpensive and provide highly accurate measurements, even with simple hardware configurations, facilitating their use in various fields. When multiple ultrasonic sensors exist in the measurement space, crosstalk occurs due to other nodes, which leads to incorrect measurements. Crosstalk includes not only receiving homogeneous signals from other nodes, but also overlapping by other signals and interference by heterogeneous signals. This paper proposes using frequency sweep keying modulation to provide robustness against overlap and a faster region-based convolutional neural network (R-CNN) demodulator to reduce the interference caused by heterogeneous signals. The demodulator works by training Faster R-CNN with the spectrograms of various received signals and classifying the received signals using Faster R-CNN. Experiments implementing an ultrasonic crosstalk environment showed that, compared to on–off keying (OOK), phase-shift keying (PSK), and frequency-shift keying (FSK), the proposed method can implement CDMA even with shorter codes and is robust against overlap. Compared to correlation-based frequency sweep keying, the time-of-flight error was reduced by approximately 75%. While the existing demodulators did not consider heterogeneous signals, the proposed method ignored approximately 99% of the OOK and PSK signals and approximately 79% of the FSK signals. The proposed method performed better than the existing methods and is expected to be used in various applications.

An X-Band Multifrequency Difference Frequency-Shift Keying CMOS Radar for Range Tracking and AI-Based Human Gesture Recognition

This article presents an X-band single-chip fully integrated multi-frequency difference frequency-shift keying (FSK) I/Q direct-conversion radar transceiver implemented in a 130-nm CMOS process. Combined with the artificial intelligence (AI)-based algorithm, accurate gesture recognition are realized. The PLL-based dual-frequency difference FSK waveform and ranging algorithm are proposed to solve the trade-off between the maximum unambiguous range and the ranging accuracy. The loop bandwidth optimized integer-N phase-locked loop (PLL) is integrated to generate standard-compliant FSK signals with predictable frequency difference. The relationship between instantaneous ranging bias and PLL loop parameters is analyzed in detail. The proposed bias noise filter fully suppresses the flicker noise and improves the receiver noise figure (NF). The quadrature signal generator (QSG) adopts a fully differential amplifier buffered resistance compensation quadrature all-pass filter (QAF) to improve the I/Q balance and insertion loss. The chip consumes a current of 56-mA, and provides a conversion gain (CG) of 22-102 dB. The single-ended transmit power is 1.5-dBm. To the best of our knowledge, the implemented transceiver is the first recorded X-band FSK radar transceiver and provide a low-cost solution for indoor human detection.

A Cycle by Cycle FSK Demodulator With High Sensitivity of 1% Frequency Modulation Index for Implantable Medical Devices

This paper presents a cycle by cycle Frequency Shift Keying (FSK) demodulator, able to demodulate a FSK signal with 1% frequency modulation index (MI), in a single cycle. Based on the proposed demodulation scheme, a high rate data transmission link can be established through a high-Q inductive coupling link, breaking the basic tradeoff between the power transfer efficiency (PTE) and data rate in single carrier wireless power and data transfer systems. Designed and simulated with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18\mu m$ </tex-math></inline-formula> CMOS process, the proposed FSK demodulator, detects successfully a 5Mbps data with a carrier frequency of 5MHz. A test chip is fabricated in 180nm CMOS technology. Measurement results shows that the demodulator is able to demodulate the cycle-by-cycle modulated FSK signals with low modulation index of 2.5%, with a 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">$1.24\times 10^{-5}$ </tex-math></inline-formula> .

Evaluation of the dual-frequency transducer for controlling thermal ablation morphology using frequency shift keying signal

Purpose The catheter-based ultrasound (CBUS) can reach the target tissue directly and achieve rapid treatment. The frequency shift keying (FSK) signal is proposed to regulate and evaluate tumor ablation by a miniaturized dual-frequency transducer. Methods A dual-frequency transducer prototype (3 × 7 × 0.4 mm) was designed and fabricated for the CBUS applicator (OD: 3.8 mm) based on the fundamental frequency of 5.21 MHz and the third harmonic frequency of 16.88 MHz. Then, the acoustic fields and temperature field distributions using the FSK signals (with 0, 25, 50, 75, and 100% third harmonic frequency duty ratios) were simulated by finite element analysis. Finally, tissue ablation and temperature monitoring were performed in phantom and ex vivo tissue, respectively. Results At the same input electrical power (20 W), the output acoustic power of the fundamental frequency of the transducer was 10.03 W (electroacoustic efficiencies: 50.1%), and that of the third harmonic frequency was 6.19 W (30.6%). As the third harmonic frequency duty ratios increased, the shape of thermal lesions varied from strip to droplet in simulated and phantom experimental results. The same trend was observed in ex vivo tests. Conclusion Dual-frequency transducers excited by the FSK signal can control the morphology of lesions. Significance The acoustic power deposition of CBUS was optimized to achieve precise ablation.

Microwave photonic multiform microwave frequency shift keying signal generator.

A photonic approach to realizing multiform microwave frequency shift keying (FSK) signal generation is proposed and demonstrated. In the scheme, a commercial dual-polarization quadrature phase shift keying modulator (DP-QPSKM) is employed to generate two orthogonally-polarized signals containing specific optical sidebands, and a subsequent Sagnac loop structure govern the interference results of these two signals. From a theoretical analysis, when the modulators are properly biased, microwave FSK signal with fixed double relationship or flexibly tunable subcarrier frequencies can be obtained, and high frequency multiplication can be realized in the meantime. Furthermore, a photonic-optimized coherent demodulation structure is designed to recover the binary coding data, which can effectively avoid the electronic bottleneck. Simulation has been performed to investigate the mechanism and the discussions about the robustness to non-ideal parameters including DC bias, phase shift and polarization angle are also given. In the proof-of-concept experiment, microwave FSK signal with subcarrier frequencies of 2/4, 2.2/3.8, 2.4/3.6, 2.6/3.4, 2.8/3.2 GHz are generated, and the correct binary coding data is successfully recovered with the aid of simulation platform. The simulation and experimental results can verify the feasibility of the proposed multiform microwave FSK signal generator, which may find applications in modern radar and communication systems.

A 164-$\mu$ W 915-MHz Sub-Sampling Phase-Tracking Zero-IF Receiver With 5-Mb/s Data Rate for Short-Range Applications

This article presents a 915-MHz ultra-low-power (ULP) sub-sampling phase-tracking receiver (SSPT-RX). It is targeted for the power-constrained devices that need short range but medium high-speed data receiving, such as the multi-channel neural stimulator with arbitrary waveform generation. The zero-intermediate frequency (zero-IF) phase-tracking receiver (PT-RX) topology is adopted to simplify the sub-sampling RX architecture with direct demodulation of frequency-shift keying (FSK) signal while improving the image frequency issue. The frequency of local oscillator (LO) is reduced by ten times with the proposed architecture, which leads to greatly reduced power consumption. Fabricated in 65-nm CMOS process, the RX chip occupies an active area of 0.58 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The RX consumes one of the lowest power consumptions of 164 <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> from 0.5-/1-V supplies. It achieves an energy efficiency of 32.8 pJ/bit at a data rate of 5 Mb/s, which is improved by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 5.6\times $ </tex-math></inline-formula> compared to the state-of-the-art RXs. The measured sensitivity of 915-MHz FSK signal receiving is −69.5 dBm with an LO frequency of 91.5 MHz, which is 1/10 of the carrier frequency. The achieved RX sensitivity figure-of-merit (FoM) is 174.3 dB.

Transient analysis of dynamically switched frequency shift keyed transmitters

A dynamically switched matching network for transmitting a wideband frequency shift keyed (FSK) signal from an electrically small monopole antenna is studied. The effects of switch synchronization, frequency deviation, the antenna's impedance, and Q-factor at the two carrier frequencies are studied. It is found that the average energy per bit of the transmitted FSK waveform is maximum when the loss of reactive energy between states transition is minimised by switching it at the instant of peak voltage across the antenna's terminals. However, a switching network topology that stores more energy is shown to be less sensitive to the synchronization condition. In addition, we show that this dynamically switched system transmits more bit energy when the carriers are closely spaced due to a smaller change in stored energy levels between states. Results are presented using a detailed analytical study and full wave simulation. Near field measurements from a monopole antenna circuit model show that under proper conditions, an FSK signal can be transmitted at a rate 7 times greater than the bandwidth of the transmit antenna with minimal signal quality degradation.

Time-frequency readability enhancement of compact support kernel-based distributions using image post-processing: Application to instantaneous frequency estimation of M-ary frequency shift keying signals

Time-frequency distributions (TFDs) based on time-lag kernels with compact support (KCS) have proved their high performance in terms of resolution and crossterms suppression. However, as for all kernel-based quadratic TFDs, these distributions suffer from spreading out signal terms. This is due to the unavoidable smoothing effects of the kernel in the ambiguity domain. The main objective of this paper is to improve concentration, interference rejection and so time-frequency localization of this representation class. The latter has the advantage of being tuned using a single parameter while external windows are no longer needed. The KCS-TFDs, referred to as KCSDs, are first optimized using a selection of the most used objective performance measures in the literature. Important signal features are extracted as well through analysis of time slice plots. The obtained TF diagrams are then enhanced using a specific method that includes two-dimensional Wiener filter, automatic binarization and morphological image processing techniques. The enhanced plots are compared to those obtained from the original TFDs using several tests on real-life and multicomponent frequency modulated (FM) signals including the noise effects. Moreover, a comparative study involving a selection of the best-performing reassignment time-frequency distributions is provided. The obtained results show a significant improvement of concentration, time-frequency localization of the autoterms as well as interference and noise suppression. As viable applications, the proposed approach is used first to instantaneous frequency (IF) estimation of several synthetic and real-life M-ary frequency shift keying (MFSK) signals. It is shown that the IF estimator from the enhanced plots performs better than smoothed pseudo Wigner-Ville distribution (SPWVD) and reassignment post-processing-based TFDs in terms of mainlobe width (MLW) and variance, respectively, even at low signal-to-noise ratio (SNR). On the other hand, time-frequency characterization of continuous wave linear frequency modulation (CW-LFM) and pulse linear FM (PLFM) radar signals is also investigated.

Design and implementation of reconfigurable ASK and FSK modulation and demodulation algorithm on FPGA (Field Programmable Gate Array)

Our modern world is completely driven by our ability to communicate all over the world with great precision, accuracy, and the least amount of time possible. Communication systems are used vastly in our worlds such as radar, aerospace, naval/maritime communication, underwater communication, mobile communication, or even in outer space such as satellite communication or space missions. Different communication system needs different types of modulation techniques. Design and implementation of reconfigurable modulators on cyclone-II FPGA (Field-programmable gate array) are proposed in this paper, wherein the type of modulations and demodulation can be dynamically reconfigured on the fly based on the requirement at any particular instance. The demodulator is intelligent enough to demodulate any modulated signal. FPGA or Field Programmable Gate Array is a computing device that can be programmed like CPU (Central Processing Unit) but fasted than CPU in parallel processing and DSP (Digital Signal Processing) related tasks. Consisting method of FPGA-based modulation does not support multiple modulation techniques at the same time and is not fast as they used Simulink-based simulation. This study has proposed FPGA based alternative to that, which can embody all the modulation techniques at once, making it way more versatile, cost-effective, and easy to use and test. The process begins with designing an algorithm. Then this algorithm has to be simulated. The algorithm is designed for both modulation and demodulation. In the modulation part, it is just simple logic to create different phrases and different frequencies of sinusoidal waves. But in demodulation, based on the frequency it can detect ASK (Amplitude Shift Keying) or FSK (Frequency Shift Keying) signal all by itself. Depending on the period of the signal, the algorithm can decide whether it is an ASK or FSK signal. After deciding it is an ASK of FSK signal, it starts to demodulate the signal. The outcome is, this FPGA-based modulator and demodulator are cheap, easy to configure, and can demodulate any type of demodulated signal. As it is reconfigurable, it's easy to deploy in any situation.

Jammer avoidance for dual-function radar-communications using FSK and independent null steering

In this paper, we propose a novel method for dual-function radar-communication(DFRC) system. Our focus is on radar being used for communications in parallel to conventional target tracking and/or surveillance assignment. In the proposed setup, the main beam is directed toward the targets as primary radar function, whereas, communication is performed through the sidelobes as secondary function. In addition, the nulls are used to avoid the jammers. A sophisticated null steering feature has been incorporated to deal with the moving jammers. In this null shifting, only the proposed null will be shifted, whereas, rest of the antenna radiation pattern including main beam and the other sidelobes will remain undisturbed. We also propose a new information embedding to transmit the communication signal in the radar emission by using the frequency shift keying (FSK) as orthogonal waveforms to transmit binary information towards the communication receivers and analyzing the impact of the FSK signals on the radar range measurements. Simulations are carried out and the results indicate the validity and performance of the proposed idea in terms of interference mitigation as well as Bit Error Rate (BER).

Photonic-assisted FSK signal generation based on carrier phase-shifted double sideband modulation

An approach to generate high-speed and wideband frequency shift keying (FSK) signals based on carrier phase-shifted double sideband (CPS-DSB) modulation is proposed and experimentally validated. The core part of the scheme is a pair of cascaded polarization-sensitive LiNbO3 Mach–Zehnder modulators and phase modulators, whose polarization directions of the principal axes are mutually orthogonal to each other. A proof-of-concept experiment is carried out, where a 0.5 Gb/s FSK signal with the carrier frequencies of 4 and 8 GHz and a 1 Gb/s FSK signal with the carrier frequencies of 8 and 16 GHz are generated successfully.

Photonic Generation of Multiform Microwave Frequency Shift Keying Signal

A photonic approach to generate multiform microwave frequency shift keying (FSK) signal is proposed. In the scheme, a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator along with a polarization controller (PC) is employed to generate two orthogonally polarized signals containing specific optical sidebands, and a following tunable filtering switch (TFS) serve as optical sidebands selector. From a theoretical analysis, when the modulators in the scheme are properly biased, we can obtain microwave FSK signal with frequency multiplication factors of 2/4 or microwave FSK signal with flexible tunable subcarrier frequencies. Simulations are conducted to verify the proposed scheme. 10/20GHz and 8/12GHz microwave FSK signals are successfully generated, and the frequency tunability is also demonstrated. In addition, the impact of the non-ideal parameters is analyzed, and the results show that the scheme has good immunity to the small parameters deviation (within 3°). The distinct advantage of our scheme is that we realize multiform microwave FSK signal generation based on a single system, which may find applications in high-frequency multifunction wireless communication system or radar system.

Reconfigurable Photonic Generation of Binary Modulated Microwave Signals

A novel photonic scheme of binary modulated microwave signals generation based on a dual-polarization quadrature phase-shift keying (DP-QPSK) modulator is proposed and experimentally demonstrated. The scheme is highly reconfigurable, amplitude keying signal (ASK), phase-shift keying signal (PSK) or frequency-shift keying (FSK) signal can be generated by appropriately setting the amplitude of the binary coding signal. The coding signal and local oscillator (LO) signals are independent with each other, binary modulated microwave signals can be generated with arbitrary coding rate and carrier frequency. The frequency deviation of the FSK signal can also be adjusted flexibly. No filter is used in the scheme and the tuning range is large. A proof-of-concept experiment is carried out to verify the feasibility of the proposed system. A 1-Gbps 8-GHz microwave ASK signal, a 0.5-Gbps 6-GHz microwave PSK signal, and a 0.5-Gbps 8/12-GHz microwave FSK signal are g[enerated in the experiment.

Transmission of a broadband FSK signal from a dynamically tuned narrowband antenna

A frequency reconfigurable patch antenna is dynamically tuned to transmit frequency-shift keying (FSK) signals over a range of frequencies much broader than the static impedance bandwidth of the antenna. Experiments are conducted for two binary FSK schemes having different carrier spacing. In both cases, dynamic tuning of the antenna is shown to increase the amplitude of the radiated signal by providing a better match than the static antenna. However, the average energy of the radiated bit at each carrier frequency decreases as the symbol rate increases beyond the 3 dB bandwidth of the antenna. Therefore, the bandwidth of the antenna is found to be a limiting factor for the maximum achievable data rate in this scheme. As an alternative to shorter bit durations, the authors show that a higher level FSK scheme using dynamic tuning is able to increase throughput beyond what is possible with a static antenna.

К ВОПРОСУ ПОСТРОЕНИЯ РАДИОТЕХНИЧЕСКОЙ СИСТЕМЫ ПЕРЕДАЧИ ИНФОРМАЦИИ, ФУНКЦИОНИРУЮЩЕЙ НА ОСНОВЕ ТЕОРИИ РАЗРЕШАЮЩЕГО ВРЕМЕНИ И ИСПОЛЬЗУЮЩЕЙ ЧМН-n-СИГНАЛ С НЕПРЕРЫВНОЙ ФАЗОЙ

At present, frequency-shift keyed signals with n discrete states have found wide application in various radio-technical digital communication systems. The main factor holding back their further development is on the one hand the limited currently attainable capacity with a given level of Quality of Service and, as a consequence, the transmission rate, which is due to a complex signal-and-noise environment, intersymbol interference and intersystem interference, and on the other hand, the attainable level of technical feasibility. The main method to increase the transmission speed in such communication systems is the transition to work in the conditions of intersymbol interference. The existing approaches to solving this problem, such as optimal and suboptimal processing methods that transform a channel with memory into a channel without memory, are of little interest because of the poor practical feasibility of the receiver itself, in principle. An alternative approach that solves this problem is the development of communication systems based on the provisions developed within the Theory of resolution time. Expanding the applicability of these provisions to service communication systems, the authors set the goal of developing a numerical method for assessing the capacity of a communication channel with memory caused by the frequency selective properties of a real channel, using frequency-shift keyed signals with n discrete states and a continuous phase. To achieve this goal, within the framework of the paper, the mathematical model of a communication channel with memory for frequency-shift keyed signals with n discrete states and continuous phase was developed, taking into account the measurement errors introduced by the receiver for determining the physical envelope and instantaneous frequency. This, in particular, makes it possible to analyze the influence of the frequency instability of the synthesizer employed in real radio-technical information transmission system on the reception quality. In this case, the mathematical model allows to optimize the system taking into account the transfer characteristic of the frequency selective communication channel of the signal constellation.

Novel radar signal to efficiently utilise spectrum based on continuous‐phase frequency‐shift keying

Aiming at the problem of high side-band spectrum for a general frequency-shift keying (FSK) radar signal, this study introduces a novel radar FSK signal based on continuous-phase frequency-shift keying (CPFSK) used in communication systems. Theoretical analysis, simulation and physical application results show that the CPFSK radar signal efficiently controls the spectral containment, whose roll-off performance of the CPFSK is ∼20 dB better than that of normal FSK; meanwhile, the modified signal possesses good ambiguity and pulse compression performances for radar application.

Equivalent photonic switch for microwave frequency shift keying signal generation.

A photonic microwave frequency shift keying (FSK) signal generator is proposed and experimentally demonstrated based on an equivalent photonic switch (EPS). The EPS is constructed using a polarization-multiplexing dual-drive Mach-Zehnder modulator (PM-DMZM). By properly controlling the data sequences and RF signals applied to the PM-DMZM, microwave FSK signals with flexible frequency intervals can be obtained. The proposed FSK signal generator features the advantages of a simple structure, low loss, good stability, and great frequency tunability. In addition, the proposed setup can also be easily reconfigured to generate microwave amplitude shift keying and phase shift keying signals. The experimental results show that 2Gb/s at 5/14GHz and 1Gb/s at 6/20GHz microwave FSK signals are successfully generated, after transmission over 5km single-mode fiber. The required received optical power at 7% forward error correction threshold is only -14.48 dBm.

Photonic generation of microwave frequency shift keying signals using a dual-polarization quadrature phase shift keying modulator

A novel method to generate microwave frequency shift keying (FSK) signals based on a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator is proposed and verified by a simulation. In this simulation work, the DP-QPSK modulator is employed to produce two orthogonally polarized double-sideband modulated signals with a wavelength spacing that is four times of the radio frequency driving frequency. Then, the signals are sent into a polarization modulator driven by a binary coding signal for complementary phase modulations. After that, a microwave FSK signal with frequency multiplication factors of four for bit ‘1’ and eight for bit ‘0’ is successfully generated through photodetection. The proposed system exhibits good stability and frequency tunability. Thanks to the high frequency multiplication factors, this method can find potential applications in high-frequency communication systems.

Photonic generation of microwave binary digital modulation signal with format agility and parameter tunability

Abstract A method for photonic generation of arbitrary microwave binary digital modulation signal based on polarization switch is proposed and investigated. A polarization modulator is utilized to switch the direction of a linearly-polarized optical signal between two orthogonal axes. Then, a polarization-dependent modulation structure is employed to modulate an external RF signal to the two optical carriers with different polarization directions respectively. The modulation structure consists of a polarization beam splitter, two parallel placed dual-drive Mach–Zehnder modulators and an optical combiner. By adjusting the parameters of the two modulators, different optical sidebands can be obtained in two polarization directions. After optical-to-electrical conversion, a microwave amplitude shift keying (ASK), frequency shift keying (FSK) or phase shift keying (PSK) signal can be achieved. The modulation format, bit-rate and carrier frequency of the generated signal can be tuned independently and flexibly. A simulation is demonstrated to verify the proposed scheme, a 2-Gbit/s 40-GHz ASK signal, a 2-Gbit/s FSK signal with carrier frequencies of 20 and 40 GHz, and a 2-Gbit/s 20-GHz PSK signal are obtained. The scheme has good tunability.