RF Signal Generator Research Articles

Tunable and Reconfigurable Fundamental, Frequency-Doubled and Dual-Frequency RF Signal Generator

Tunable and Reconfigurable Fundamental, Frequency-Doubled and Dual-Frequency RF Signal Generator

Generation of frequency-shift keying (FSK) and amplitude-shift keying (ASK) RF signals by diode-tuned Fourier domain mode-locked opto-electronic oscillator

An approach to the generation of frequency-shift keying (FSK) and amplitude-shift keying (ASK) RF signals with a diode-tuned Fourier domain mode-locked opto-electronic oscillator (FDML OEO) is proposed and demonstrated. We use a low-cost varactor diode tuned phase shifter to form a high speed tunable bandpass filter (TBF) to implement the FDML-OEO. When a square wave modulation signal is used to drive the TBF, FSK RF signals are generated, with the flexibility to easily change the center frequency and tuning bandwidth of the FSK signals. For the ASK RF signal generation, a band-pass filter (BPF) with a bandwidth less than the TBF tuning range is added to the FDML OEO RF feedback loop. When the TBF center frequency hops in and out of the BPF bandwidth within a mode locking period, the FDML OEO generates ASK RF signals. The phase noises of the FSK and ASK RF signals generated by our FDML-OEO are both measured to be −123dBc/Hz at 10 kHz offset frequency. The key significance of this approach is that no microwave source is required to generate the ASK signal and reconfigurable FSK and signals, which may find wide applications in future radar and communications systems.

Scalable stable comb-to-tone integrated RF photonic drive for superconducting qubits

The recent advent of quantum computing has the potential to overhaul security, communications, and scientific modeling. Superconducting qubits are a leading platform that is advancing noise-tolerant intermediate-scale quantum processors. The implementation requires scaling to large numbers of superconducting qubits, circuit depths, and gate speeds, wherein high-purity RF signal generation and effective cabling transport are desirable. Fiber photonic-enhanced RF signal generation has demonstrated the principle of addressing both signal generation and transport requirements, supporting intermediate qubit numbers and robust packaging efforts; however, fiber-based approaches to RF signal distribution are often bounded by their phase instability. Here, we present a silicon photonic integrated circuit-based version of a photonic-enhanced RF signal generator that demonstrates the requisite stability, as well as a path towards the necessary signal fidelity.

1.7 GHz long-term evolution radiofrequency electromagnetic field with stable power monitoring and efficient thermal control has no effect on the proliferation of various human cell types.

Long-term evolution (LTE) radiofrequency electromagnetic field (RF-EMF) is widely used in communication technologies. Thus, the influence of RF-EMF on biological systems is a major public concern and its physiological effects remain controversial. In our previous study, we showed that continuous exposure of various human cell types to 1.7 GHz LTE RF-EMF at a specific absorption rate (SAR) of 2 W/Kg for 72 h can induce cellular senescence. To understand the precise cellular effects of LTE RF-EMF, we elaborated the 1.7 GHz RF-EMF cell exposure system used in the previous study by replacing the RF signal generator and developing a software-based feedback system to improve the exposure power stability. This refinement of the 1.7 GHz LTE RF-EMF generator facilitated the automatic regulation of RF-EMF exposure, maintaining target power levels within a 3% range and a constant temperature even during the 72-h-exposure period. With the improved experimental setup, we examined the effect of continuous exposure to 1.7 GHz LTE RF-EMF at up to SAR of 8 W/Kg in human adipose tissue-derived stem cells (ASCs), Huh7, HeLa, and rat B103 cells. Surprisingly, the proliferation of all cell types, which displayed different growth rates, did not change significantly compared with that of the unexposed controls. Also, neither DNA damage nor cell cycle perturbation was observed in the 1.7 GHz LTE RF-EMF-exposed cells. However, when the thermal control system was turned off and the subsequent temperature increase induced by the RF-EMF was not controlled during continuous exposure to SAR of 8 W/Kg LTE RF-EMF, cellular proliferation increased by 35.2% at the maximum. These observations strongly suggest that the cellular effects attributed to 1.7 GHz LTE RF-EMF exposure are primarily due to the induced thermal changes rather than the RF-EMF exposure itself.

RF direct sampling and processing electronics for SHINE cavity BPM system

Cavity BPMs are crucial for achieving submicron beam alignment in X-ray Free-Electron Lasers (XFEL), particularly in undulator sections. These monitors typically generate RF signals in the S, C, or X band regions. Due to the limitations of analog-to-digital converter's (ADC) bandwidth and sampling rates, and digital signal processing capabilities, heterodyne and homodyne receivers are often employed to down-convert the RF signal to an intermediate frequency (IF) or baseband (Zero IF) respectively before digital sampling. The digitized signal is then processed by Field Programmable Gate Array (FPGA) to get the beam position and phase information. An RF direct-sampling beam signal processor has been developed using ADCs with a bandwidth of 9 GHz and a sampling rate of 2.6 GSPS, and a powerful system-on-chip FPGA. In addition, a prototype RF module without complex down conversion devices has been designed for the SHINE (Shanghai High Repetition Rate XFEL and Extreme Light Facility) cavity BPM. The processor and the RF module make a novel RF direct sampling and processing cavity BPM electronics for SHINE. This is the first attempt to use direct sampling electronics in the C band cavity BPM system. The analog signal processing chain is greatly simplified compared to the down-conversion structure. The performance of this electronics has been analyzed and evaluated in laboratory. The amplitude relative error is 2.0 × 10-4, surpassing the required accuracy of 1 × 10-3 for cavity BPM systems. The phase error is 14 femtoseconds (fs), which also meets the requirements for an RF Beam Arrival Time Monitor (BAM) system. Additionally, the paper introduces the cavity BPM signal processing algorithms and their implementation in FPGA. The processor can deliver pulse-to-pulse beam position measurement above 1 MHz. The RF direct-sampling electronics represents significant advancements in cavity BPM system, large-scale application can be carried out in accelerator facilities like SHINE.

GHz repetition rate tunable optical pulses generation using a SBS-based coupled optoelectronic oscillator

An optical pulse generator with a tunable repetition rate of GHz is proposed employing a coupled optoelectronic oscillator (COEO). The tunability is achieved with an equivalent tunable RF bandpass filter which is realized through phase modulation and stimulated Brillouin scattering (SBS) in a high nonlinear fiber. An injected seed laser is applied to stabilize the central wavelength of the mode-locked loop. The repetition rate of the generated optical pulses is the frequency difference between the Stokes wave and the seed laser. It is adjusted by changing the wavelength of the pump laser for SBS effect. In the experiments, optical pulse trains with a repetition rate of 7.3 GHz–9.3 GHz are generated, and RF oscillating signals at the corresponding frequency are simultaneously produced. The side-mode suppression ratios (SMSRs) of the generated RF signals are all higher than 50 dB, and the phase noise is lower than −80dBc/Hz @10-kHz offset frequency. The tunable range of the optical pulse rate is limited by the bandwidth of the used RF phase shifter in the oscillating loop.

Enhancing GNSS receiver performance with software-defined vector carrier tracking for rocket launching

It is well-known that the use of Vector Tracking Loops (VTL) in GNSS receivers can result in improved tracking performance and sensitivity, faster acquisition, and improved interference robustness. However, despite the availability of software-defined radio (SDR) GNSS receivers in practical applications, there is currently no open-source implementation of Vector Tracking techniques able to operate in real-time. This work introduces a VTL algorithm applied to track the Doppler shift and its rate, using the open-source GNSS-SDR framework. This leads to a novel real-time SDR GNSS VTL receiver capable to work with different COTS front-ends. The proposed implementation was tested in a challenging non-conventional, high dynamics positioning scenario to obtain the position and velocity vectors of a rotation-stabilized guided rocket. The scenario was simulated with a GNSS RF signal generator, captured with a COTS front-end and processed by GNSS-SDR. Results show that the algorithm and its proposed implementation are able to provide full tracking, even under demanding accelerations. The positioning performance is measured using standard metrics, and we provide a fully automated reproducibility path. The source code is released under the General Public License v3.0, and will contribute to GNSS-SDR's open-source code base.

Reltron Oscillator for Long Pulse and High-Power RF Generation

In this article, a new configuration of the reltron oscillator (i.e., gridless reltron configuration with annular explosive emissive cathode) was proposed for long pulse and high-power RF generation. To investigate the electromagnetic (EM) and RF behavior, the structure was modeled in the CST Studio Suite and then simulated with the help of different solver modules of the CST simulation tool. The effect of various electrical parameters of the proposed configuration on the generated pulsewidth and RF power was also studied. For the optimized structure, the proposed configuration produced an RF signal of peak microwave power of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 190 MW with a pulsewidth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> s. These simulation results were compared with the experimentally reported gridded and gridless reltron, and it was noted that: 1) the proposed configuration produced a peak RF power similar to a gridded reltron with a lower operating voltage; 2) the pulsewidth of the generated RF signal was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 10 times higher than the gridded reltron; 3) obtained <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 10 times higher peak RF power than the gridless reltron; and 4) pulsewidth was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 0.2 times lesser than the gridless reltron. Eventually, the structure was benchmarked with the experimentally reported gridded and gridless reltron for its validation.

Multi GNSS IRNSS L5 IRNSS S1 and GPS L1 Hybrid Simulator A Reconfigurable Low cost Solution for Research and Defence Applications

Satellite-based positioning field of research is growing rapidly as there is an increase in demand for precise position requirements in various civil and commercial applications. There are many errors that affect the GNSS signals while propagation from satellite to receiver, which eventually induces errors in pseudo-range measurements. In order to assess the receiver characteristics for a specific error condition, the real-time signals may not be appropriate, and it is challenging to perform repeated experiments with the same error condition. The advantage of the GNSS simulator is that users can model the different scenarios for any given location on the globe, which are repeatable at any point of time. The conventional hardware simulators are expensive and have few limitations. In this paper, a reconfigurable hybrid simulator is proposed with some advantages over traditional hardware simulators, such as low cost, reconfigurability, and controllability over fundamental parameters. It can be able to record intermediate stage data, which makes it more suitable for the GNSS research field. The proposed multi-GNSS simulator considered implementing IRNSS-L5, IRNSS-S1, and GPS-L1 band signals. A general-purpose computer can perform the necessary calculations for signal generation. The hybrid simulator can be able to generate the digital I/Q data, which can be stored as I/Q data or can be connected to a general-purpose SDR (Software Defined Radio) for RF signal generation (bladeRF in this case). The I/Q data can be used with the software receiver to analyse the receiver performance concerning the specific error. The generated GNSS signals are validated with software and hardware receivers, and the obtained position is observed as expected.

Dissipative microwave photonic solitons in spontaneous frequency-hopping optoelectronic oscillators

Dissipative solitons relying on the double balance between nonlinear and linear effects as well as cavity loss and gain have attracted increasing attention in recent years, since they give rise to novel operating states of various dissipative nonlinear systems. An optoelectronic oscillator (OEO) is a dissipative nonlinear microwave photonic system with a high quality factor that has been widely investigated for generating ultra-low noise single-frequency microwave signals. Here, we report a novel operating state of an OEO related to dissipative solitons, i.e., spontaneous frequency hopping related to the formation of dissipative microwave photonic solitons. In this operating state, dissipative microwave photonic solitons occur due to the double balance between nonlinear gain saturation and linear filtering as well as cavity loss and gain in the OEO cavity, creating spontaneous frequency-hopping microwave signals. The generation of wideband tunable frequency-hopping microwave signals with a fast frequency-hopping speed up to tens of nanoseconds is observed in the experiment, together with the corresponding soliton sequences. This work reveals a novel mechanism between the interaction of nonlinear and linear effects in an OEO cavity, extends the suitability and potential applications of solitons, and paves the way for a new class of soliton microwave photonic systems for the generation, processing, and control of microwave and RF signals.

AN OPTIMIZED DESIGN MODELLING OF A NEURAL NETWORK BASED GREEN HOUSE MANAGEMENT SYSTEM USING SOLAR AND RECTIFYING ANTENNA

The renewable energy resources are widely used in various real time applications, which utilized the solar, wind, fuel cell, etc. From this, the energy management and controlling strategy improves the results. The conventional approach uses Quantum Tunneling PSO for optimization and it is managed with various utility on power grid system. The work utilized the solar and EM waves for energy management scheme and it utilized the controlling parameter by optimization algorithm. The drawback of conventional method is that, the hybrid system utilization and switching is performed with random selection and it not capable for hybrid resources of multiple array functioning. The proposed research work performed with the solar with MPPT tracking and EM with rectenna are utilized and with the help of neural network model, the PV and RF signal generations are stored as array and based on the switching duty cycle from the function of proposed particle swarm optimization, the boost converter act to provide the supply to grid. Through the inverter control, the model fed with the grid, which uses PI controlling with PWM signal generation. Based on the demand and grid utility the LC compensation improves the boost converter performance. The PV and RF signal generation utilized on the continuous utility and obtains the demand free grid circuit. By comparing with the proposed and existing approach, the proposed greenhouse management model obtains the better result. Overall simulink model is done with MATLAB 2018a. Keywords- PV module; EM waves; Rectenna; Proposed PSO; Feed Forward neural network; PI controller and grid utility;

Simulation Investigations of High Power Overmoded Relativistic Backward Wave Oscillator with Trapezoidal Resonant Reflector

An S-band high power relativistic backward wave oscillator using a trapezoidal resonant reflector and overmoded slow-wave structure is demonstrated by finite difference time domain based Particle-In-Cell code. The trapezoidal resonant reflector and slow-wave structure are chosen to improve the RBWO power handing capability to gigawatt (GW). The Trapezoidal resonant reflector enhances the pre-modulation during electron beam propagation, thus increasing the generated RF signal overall efficiency and coherency. The particle-in-cell simulation generated an RF output power ~5.4 GW in TM01 mode at ~3.6 GHz in a 2.0 T magnetic field and developed a 13.5 kA current for a 1.2 MV DC cathode voltage. The power conversion efficiency is achieved as ~33 %. Further, the influence of different design parameters on frequency, RF output power, and efficiency are analysed through Particle-In-Cell simulations.

One‐third optical frequency divider for dual‐wavelength optical signals based on an optoelectronic oscillator

An optical frequency divider for dual-wavelength optical signals based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The Mach-Zehnder modulator in the OEO is biased at the minimum transmission point, the OEO-based frequency divided signal originates from system noise. When the oscillation phase and amplitude conditions met, it gets stabilised at an oscillation frequency which is one-third of the frequency interval of the injected dual-wavelength optical signal. A proof-of-concept experiment is verified. With the frequency interval of the dual-wavelength optical signal ranging from 101.4 to 120.6 GHz, the RF signals ranging from 33.8 to 40.2 GHz are successfully generated. The power ripple is lower than 2.92 dB and the rejection ratio of the harmonic components is larger than 39 dB for all the conditions. The phase noise values of the generated RF signals are kept to be around -105 dBc/Hz@10 kHz.

Photonic RF Phase-Encoded Signal Generation With a Microcomb Source

We demonstrate photonic RF phase encoding based on an integrated micro-comb source. By assembling single-cycle Gaussian pulse replicas using a transversal filtering structure, phase encoded waveforms can be generated by programming the weights of the wavelength channels. This approach eliminates the need for RF signal generators for RF carrier generation or arbitrary waveform generators for phase encoded signal generation. A large number of wavelengths of up to 60 were provided by the microcomb source, yielding a high pulse compression ratio of 30. Reconfigurable phase encoding rates ranging from 2 to 6 Gb/s were achieved by adjusting the length of each phase code. This work demonstrates the significant potentials of this microcomb-based approach to achieve high-speed RF photonic phase encoding with low cost and footprint.

Design of a fluorescent tube antenna with defined copper wire coupling specifications

In this paper, the performance of a fluorescent tube antenna is analyzed with respect to the dimensions of copper wire utilized in RF coupling. The fluorescent tube antenna in the study is implemented using a 58.5cm long fluorescent tube with a diameter of 2.7cm and four different copper wires with provided dimensions, wound at specific chosen lengths. RF signals are generated and output power measured using a Handheld RF Signal generator and Spectrum Analyzer respectively. The performance index used to evaluate the improved functionality of the design presented is the Received Signal Strength (RSS) and the gain. A peak RSS value of -34 dBm is obtained using a 1mm thick copper wire wound at 50cm of the fluorescent tube length and the gain of the antenna is 14.37 dBi derived with the Friis Transmission Equation. Research findings are presented and compared to previous similarly conducted studies, and seen to perform favorably better.

Raspberry PI 3 RF signal generation system

Radio frequency signal generators (RF) are instruments used to test reception equipment and RF components like filters, amplifiers, attenuators, among others. On the other hand, they reinforce the teaching-learning processes and they are widely used in research in the telecommunications field. This document provides the first stage of a low-cost signal generator design by using RaspBerry Pi 3, with the documentary exploration about this kind of applications. After that, a recognition of the RaspBerry Pi 3 is done at hardware and software level. Finally, an application of an FM signal generator with RaspBerry in a frequency of 101.3 MHz is evaluated, which does not require any additional hardware. This signal was captured using a spectrum analyzer, which determined good quality of the modulated signal in terms of power, bandwidth and SNR (Signal Noise Ratio). However, there are some unwanted harmonic components

Photonics-based multi-band/multi-mode radar signal generation

Microwave/millimeter-wave photonics is playing a prominent role in overcoming the challenges of RF signal generation and processing. This evolving technology has many advantages, such as RF carrier stability and broad operating bandwidth, and is applicable to a wide range of civil and military applications such as 5G communication networks, radar/jammer systems, and medical imaging. In this work, we leverage the multidimensional capabilities of microwave photonics in order to generate multi-band/multi-mode radar signals for multi-purpose applications. Our proposed system can generate up to five radar bands, simultaneously, with different modulation bandwidths, without hardware modifications. Additionally, various radar waveforms can be transmitted, simultaneously, over the corresponding radar bands. The RF radar signals are generated optically using a reconfigurable frequency comb source, which reduces the system cost significantly. The stability of the RF carriers is experimentally tested and compared with that of the mode-locked-loop-based laser sources, wherein a comparable performance is observed. Experimental results show the generation of four radar waveforms, including frequency modulated waveforms (pulsed linear frequency modulation and frequency modulated continuous wave) and polyphase codes (Barker-11 and Barker-13). Moreover, five carrier frequencies are used to transmit the various radar modulation schemes. These are 5.25, 9.325, 16.1, 26.4, and 28.15 GHz RF carriers. The signal quality is measured experimentally, and high signal-to-noise ratio (SNR) of 35, 30, 30, 25, and 20 dB SNR was observed in the C-, X-, Ku-, K-, and Ka-bands, respectively.

Post-surgical fall detection by exploiting the 5 G C-Band technology for eHealth paradigm

Internet of Thing (IoT) in the wireless sensing utilizing 5G C-Band is the modern technology and taking 5G C-Band wireless sensing to the higher paradigms. The healthcare sector utilizing 5G C-Band technology will increase the efficiency of monitoring the fall and other body motions with maximum capacity and extensive spectrum range. We have proposed the unique system operating at 4.8 GHz frequency for measuring the wireless channel information (WCI) of post-surgical falls and other related human activities. The overall system exploit the low cost simple wireless devices including NIC card, RF signal generator, Omni directional antenna and a desktop PC. The fall and other human activities are classified by using machine-learning algorithms like Support Vector Machine (SVM), Naïve Bayes and Decision Tree. The three main kernel functions RBF, Linear and polynomial were used for the classification along with the 10 time domain features. The performance of the classifiers increases by using the maximum number of features. We have concluded that the SVM proves to be the best classifier for our wireless data by measuring the performance metrics like accuracy (above 90 %), F-measure, Precession, Specificity, Recall, and Kappa coefficient. The error rate for SVM proved to be the less as compared with the other two classifiers. The accuracy increases with the rate of 4 to 5 %. Our approach shows more feasibility for detecting the post-surgical fall in hospitals and more reliable with maximum accuracy.

Simple method for stabilizing an optical frequency comb to an optical reference without an RF signal generator

We have experimentally demonstrated a simple and robust method for achieving a narrow-linewidth optical frequency comb (OFC) without an RF signal generator (SG). Our method requires fewer RF components than previous methods. The Allan deviation and integrated RMS phase noise with our method for the in-loop carrier-envelope-offset-frequency signal are 3.3×10−16/τ and 0.35 rad at an integration bandwidth from 1 Hz to 5 MHz, respectively, where τ is the averaging time. Our method could become very useful when RF SG stability becomes a bottleneck to improving OFC stability.

Optical Behavior Analysis of Negative Wavelength Detuning in SMFP-LD and Its Effect on Multi-RF Generation

Injection locking with positive wavelength detuning has been used for a long time for optical signal processing, signal generation, and computing. Recently a new technique, “injection locking with negative wavelength detuning,” has been introduced and has shown its potential on microwave generation. In this paper, we analyze optical behavior of negative injection locking and its impact on multi-RF generation using single-mode Fabry-Perot laser diode (SMFP-LD). SMFP-LD is composed of a commercial multi-mode FP-LD with a built-in external cavity. As compared to conventionally used positive detuning optical injection, the negative detuning optical injection (NOI) shows advantageous differences on the suppression of the dominant mode, side modes, bistability property, and the hysteresis width. The laws of free carrier motion in the laser cavity is leveraged to explain these phenomena. Based on the analysis, the NOI in the SMFP-LD has a distinct advantage for multi-RF generation and switching RF signals. In addition, the output performances of the generated RF signal such as linewidth, power-dependent frequency shifting, and signal-to-noise ratio (SNR) are investigated.