Continuous Wave Generator Research Articles

A BLE 5.0 Extended Advertising Backscatter with Commodity Devices in Passive IoT Scenarios

BLE-based (Bluetooth Low Energy-based) backscatter has received considerable attention, as it aims to communicate with everyday smart devices such as smartphones, smartwatches, and tablets in passive IoT. The state-of-the-art BLE backscatter systems enable communication using a specialized continuous wave (CW) generator or entirely using commodity BLE 4.0 radios as an RF source. However, the existing BLE communication systems suffer from several key issues, including a short carrier length and a large frequency shift. This paper presents a passive BLE (PBLE) backscatter communication system that utilizes commodity BLE 5.0 radios. The system uses a BLE 5.0 extended advertising packet with partial single tones as excitations transmitting on the secondary advertising channel of BLE 5.0, and the BLE backscatter tag produces bandpass frequency-shift keying modulation at 1 Mb/s, which enables compatibility with BLE advertising channels. The prototype is implemented using an NRF52832 BLE 5.0 commodity chip, smart devices, and tags with FPGAS and chips. In FPGA board-level verification, when the downlink distance is 0.5 m, the uplink distance can reach 10 m. In chip testing, the uplink distance can reach 7 m when the downlink distance is 1 m. The baseband power consumption is 2 μW, with a total power consumption of 10 μW. This system eliminates the need for expensive and costly specialized RF sources, unlike the BLE backscatter communication system that uses a specialized CW generator. Compared to the BLE backscatter communication system that uses commodity BLE 4.0 radios, this system reduces the minimum frequency shift from 24 MHz to 2 MHz and increases the length of the single tones as a CW by a factor of about seven, from 31 bytes to 254 bytes.

Photonic-Assisted Programmable Ultra-Wideband Frequency-Modulated Continuous-Wave Generator

Photonic-Assisted Programmable Ultra-Wideband Frequency-Modulated Continuous-Wave Generator

Study on boundary reflection mechanism of continuous wave mud pulse in the flow loop

Continuous wave (CW) mud pulse is one of the essential ways of high speed data transmission while drilling. The boundary reflection process and mechanism need to be clarified, which seriously affects the analog interpretation of pressure waves in flow loops and drilling conditions. In this paper, the boundary reflection of mass inlet and pressure outlet is studied by using traditional acoustic theory and numerical simulation methods, and mutual verification is carried out with flow loop. The results show that the pressure wave generated by the CW generator can be divided into compression wave and expansion wave and transmitted to the upstream and downstream pipelines. The inlet boundary reflection is the hard boundary reflection in acoustics. The phase of reflected wave is the same as that of the incident wave. The outlet boundary is the soft boundary, the reflected wave phase is 180° opposite to the incident wave. In particular, the process and mechanism of secondary reflection of stator and rotor structure on pressure wave are analyzed for the first time, which provides a theoretical basis for pressure wave amplitude. Finally, due to the possibility of cavitation phenomenon in the flow loop, it is different from the pressure environment of the bottom under drilling conditions and should to study further.

Microwave-sensor-node integrated into a short-range wireless sensor network

This paper presents the first microwave-sensor-node integrated into a short-range wireless sensor network based on ZigBee technology. The node includes an analog front-end circuit, a Frequency Modulated Continuous Wave generator, an Analog-to-Digital-Converter module, a transceiver, a power unit, a processing unit and a new one-port dielectric permittivity sensor which is able to measuring the separation of structural cracks by the reflection coefficient measured in microwave frequencies. The analog front-end is composed of a pair of power dividers, an isolator and a mixer. The dielectric permittivity sensor is based on a patch antenna of variable length. The processing unit and transceiver are implemented with an Arduino UNO and an XBee module respectively. Additionally, the methodology for data processing is presented and the results of the measurement of a synthetic crack are presented. The results show that the system was successfully implemented with a sensitivity of 0.07 GHz/mm, for an opening range of between 0 and 5 mm and for a frequency range ranging from 2.782 GHz to 3.131 GHz. It is important to mention that the measurement was done remotely, placing the sensor 3 m from the client PC.

A continuous phase-frequency modulation technique and adaptive pump noise cancellation method of continuous-wave signal over mud telemetry channel

Continuous wave telemetry is one of the critical downhole-to-surface transmission techniques of downhole information for logging while drilling (LWD). This paper aims to present a highly effective modulation technique for a continuous wave telemetry called Continuous Phase-Frequency Keying (CPFK) and an adaptive coherent detection method for the CPFK signal. The modulation equation of the CPFK signal is established according to the acceleration/deceleration time of the motor in a continuous wave generator, the coherent detection method is given for the demodulation of CPFK signal, and then the adaptive mud pump noise cancellation algorithm is proposed for identifying CPFK signals based on probability analysis and PSO (Particle Swarm Optimization) algorithm. The results of simulation analysis show that the proposed CPFK modulation mode is feasible and the adaptive mud pump noise cancellation algorithm can realize the demodulation and decoding of CPFK signals. It has been found from the analysis that pump noise is the main noise affecting the demodulation of CPFK signals, accurate removal of pump noise can effectively improve the frequency band utilization of CPFK signal and reduce the bit error probability of the adaptive mud pump noise cancellation algorithm.

Load torque analysis and compensation device design for low power drilling fluid continuous wave generator

As an advanced downhole instrument in drilling engineering, drilling fluid continuous wave generator (DFCWG) has great application prospects. The large load torque is one of the key problems that hinder the development of DFCWG. In this paper, based on the design theory of rotary valve and finite element method, the structure of rotary valve is designed and the load torque characteristics is analyzed and points out that the load torque has strong alternating characteristics. It is pointed out that the load torque has the characteristics of strong alternating. According to the characteristics of the load torque, the "fluid-magnetic" collaborative compensation method is proposed. The load compensation turbine and magnetic compensation device are used to compensate the DC and AC components of the load torque respectively, and the load compensation device is designed. The rationality of the design of the load compensation device is verified by simulation. Finally, the comprehensive compensation effect is analyzed by the finite element method. According to the analysis results, the "fluid-magnetic" collaborative compensation method can effectively reduce the load torque. The research results can provide technical support for DFCWG design.

Modeling and Analysis of the Load Torque Acting on the Drilling Fluid Continuous Wave Generator

Drilling fluid continuous wave(DFCW) generator is an advanced downhole instrument and has broad application prospects. The load torque acting on the DFCW generator has a great impact on the performance on the DFCW generator, and there is a lack of theory describing the load torque because of the irregularity of the rotary valve. In this paper, the drilling fluid flow area is divided into the curve flow area, the radial flow area and the axial flow area. The flow area of each part is divided into several meshes based on finite element theory, then the load torque acting on each part is calculated based on the fluid momentum conservation theory. The theoretical model is verified by combining the simulation and the experiment, and the effects of the discharge and the axial gap on the load torque are analyzed. The research results show that:(1) the theoretical model can be used to determine the load torque, (2) the amplitude of the load torque reduces as the gap decreases and increases rapidly as the discharge increases. The results can provide the theoretical guidance for the structure design of the rotary valve and the control system design of the drilling fluid continuous wave generator.

A 77-GHz Mixed-Mode FMCW Generator Based on a Vernier TDC With Dual Rising-Edge Fractional-Phase Detector

A 77-GHz frequency-modulated continuous-wave (FMCW) generator is presented for millimeter-wave (mm-wave) radar applications. The FMCW chirp is provided by a mixed-mode phase-locked loop (PLL). A dual rising-edge fractional-phase detector based on time-to-digital converter (TDC) is proposed to overcome the problem caused by the rising and falling time mismatch. A 2.3 ns detection range, 10 ps resolution Vernier TDC is employed in the detector to cover the two consecutive rising edges with less power consumption. A self-calibrated delay chain is employed in the Vernier TDC to overcome process, voltage and temperature (PVT) variations. Furthermore, sampling-edge selection technique is utilized to avoid the glitch during phase detection. A divider-less frequency error estimator is presented to save area and power. By employing a coarse-fine segmented digital-to-analog converter (DAC), the generator supports triangular and sawtooth-like FMCW chirp with reconfigurable period and bandwidth. An LC voltage- controlled oscillator (VCO) with split varactor is proposed to improve the linear tuning range. Implemented in 65 nm CMOS, the FMCW generator consumes 99 mW power and 0.7 mm $\times $ 0.8 mm chip area. The measurement results show that the phase noise from 78.7 GHz carrier is −87.4-dBc/Hz at 1 MHz offset. The measured root-mean-square (RMS) frequency error of a sawtooth-like FMCW chirp with 4 GHz bandwidth and 0.1 ms period is 205 kHz.

Simulation study of rotor erosion for a continuous-wave pulse generator by computational fluid dynamics

Continuous-wave pulse generator plays an important role in generating high-quality pulse signals in measurement while drilling systems. However, the generator affects the quality of pressure wave signals due to erosion on the continuous wave generator rotary valve caused by drilling fluid during operation. In this paper, the computational fluid dynamics (CFD) model of a rotary valve was established by ANSYS finite element method, and a series of three dimensional flow field simulation experiments were conducted to analyze the influence of factors, such as drilling fluid density, viscosity, inclusion particle diameter, and particle mass flow on the erosion of the rotary valve. Experiments show that the rotor erosion increases with increasing drilling fluid density, viscosity, diameter, and mass flow of particles in the drilling fluid. Moreover, the rotor erosion exponentially increases with increasing viscosity of the drilling fluid. The results provide necessary data for drilling fluid system improvement, rotor material selection, and surface structure treatment.

A highly linear and fully-integrated FMCW synthesizer for 60 GHz radar applications with 7 GHz bandwidth

A highly linear and fully-integrated frequency-modulated continuous-wave (FMCW) generator based on a fractional-N phase-locked loop (PLL) that is able to synthesize modulation schemes in 57---64 GH...

A Cost-effective Sub-terahertz Continuous Wave Generation Scheme Using a Broadband Optical Source and An Optical Feedback Loop

We have proposed a cost-effective sub-terahertz (THz) continuous wave (CW) generation scheme based on a usual double sideband-suppressed carrier (DSB-SC) scheme. The usual DSB-SC scheme, which consists of a discrete optical source, an optical intensity modulator (OIM), a local oscillator (LO), an optical notch filter, and an erbium doped fiber amplifier (EDFA), is one of well-known photonic-based sub-THz CW generation schemes. As the discrete optical source of the usual DSB-SC scheme is eliminated and an optical feedback loop is incorporated with the usual DSB-SC scheme, our proposed scheme is constructed to decrease implementation costs. Without an optical input, the output of the pump laser of the DC-biased EDFA is inserted to the optical notch filter. Reflected lightwaves with fiber bragg grating wavelengths of the optical notch filter is fed back to the input of the OIM through the optical feedback loop, which is composed of a circulator and a 90:10-coupler. DSB-SC lightwaves have been made by modulating feedbacked lightwaves on the OIM with the frequency of the LO. A sub-THz CW is generated by photomixing them. To verify feasibility of our proposed scheme, we generated and characterized a 120 GHz CW. The measurement results were also compared to those of the usual DSB-SC scheme. Based on our measurement results, we found that characteristics of the generated 120 GHz CW using our proposed scheme are comparable to those using the usual DSB-SC scheme. Consequently, our proposed scheme can be helpful to make a cost-effective sub-THz CW generator based on photonics.

Comparative Analysis on OQPSK and QDPSK of Continuous Pressure Wave System in Drilling Fluid Channel

Based on the urgent needs for high transmission speed and high reliability of wireless MWD, the OQPSK modulation of the drilling fluid continuous wave signal is proposed in this article. The Principle of delay orthogonal modulation and coherent demodulation of OQPSK are studied, and the changes in the phase vector of the inputted bit sequence are analyzed; according to the principle of continuous wave generation, the phase adjustment mechanism of rotary value are analyzed and the relationship between the signal waveform, as well as the rotational speed when adjusting the phase, is studied; the information transmission rate, band efficiency and bit error rate of the OQPSK and QDPSK continuous wave communication systems are comparatively analyzed and simulated. The results show that OQPSK eliminates the phase transition of π, which belongs to constant envelope modulation, is suitable for the transmission under low SNR drilling fluid channel, meanwhile simplifies the phase adjustment and reduces generator design. QDPSK can simplify the computational complexity of phase adjustment, and reduces the design difficulty of the continuous-wave generator’s control circuit. The rotary valve forms of "slow down - speed up" and " speed up - slow down " are suitable for π / 2 and 3π / 2 phase jump respectively; the motor control modes which combine closed loop position and closed loop velocity can achieve phase stable signal and reduce the dynamic torque of the motor; in the same carrier frequency and SNR, the information rate and bandwidth efficiency of both OQPSK’s and QDPSK’s are twice as those of the two-phase shift keying system’s, and they can improve the wireless transmission performance of MWD system.

The dynamic performance analysis of the reciprocating continuous wave generator based on the fluid–structure interaction

Using computational fluid dynamics method, dynamic mesh technology, and the dynamic equation of the moving elements, the performance of the reciprocating continuous wave generator is simulated. The influence of the non-Newtonian property of the drilling fluid on the pressure signal is analysed, and the results show that the influence of the non-Newtonian property on the pressure loss at the orifice is small due to the high Reynolds number. The influence of the motion pattern and the exciting frequency of the pilot valve on the dynamic performance of the generator is also analysed, and the results show that: the signal generated from the sinusoidal motion pattern of the pilot valve changes mildly, which is beneficial to the continuous wave generation; during the main poppet opening, the relief valve is at the position of minimum lift, which results in the slowly decreasing pressure, and the rate of signal generation is decreased.

Comprehensive Survey for the Frontier Disciplines Latest advances in THz coherent light source pumped by 600—2000 nm waveband pumped source

Recently, due to the potential applications, the developing of compact, portable, low cost, and tunable THz wave became a research focus of THz technology. The light source with a wavelength range from 600—2000 nm frequently serves as a pumped source of THz wave due to its property of compact size, low cost, tunable frequency and stable operation. In this paper, tunable dual-wavelength continuous-wave pumping source and THz generator with an internal-cavity optical parameter oscillator are overviewed and analyzed in detail. It is shown that pumping source in the near-infrared wave band is more advantageous than those in the mid-infrared wave band for compactness in size. It is also shown that the difference frequency and nonlinear cascade processes have become an important way to generate THz radiation for wide tuning merit in such a system.

편광 및 위상 부정합을 이용한 광혼합을 통하여 발생된 서브 밀리미터파 대역 연속파의 위상 잡음 특성 개선

본 논문에서는 광혼합 방식으로 서브 밀리미터 및 테라헤츠 대역 연속파 신호를 발생시키는 기법 중 가장 널리 사용되는 광반송파가 억제된 양측 대역 발생 방식(Double Sideband-Suppressed Carrier: DSB-SC)을 이용하여 발생된 연속파(Continuous Wave: CW) 신호의 위상 잡음 개선을 위하여 광신호의 편광과 위상 제어 기법을 제안하고 실험적으로 증명하였다. 광신호의 편광 및 위상 제어 기법은 일반적인 DSB-SC 신호와 DSB-SC 신호에 포함된 광반송파와 동일한 파장과 위상차를 가지며, 광반송파의 편광 성분 중 하나의 편광 성분만을 갖도록 편광제어된 광신호를 결합하여 광혼합하는 방법이다. 실험 및 측정 결과, 서브 밀리미터파 대역 CW 신호의 크기는 1.5 dB 증가하였으며, 위상 잡음 특성은 약 3 dB@10 kHz offset frequency 개선됨을 확인하였다. 따라서 본 논문의 결과는 광신호의 위상 및 편광 성분 제어만으로 광반송파를 효과적으로 억제하여 서브 밀리미터 및 테라헤르츠 대역 CW 신호의 특성을 개선함으로써 광혼합 방법을 이용한 밀리미터파 및 테라헤르츠파 대역 CW 신호 발생기의 저가화를 위한 기본적인 데이터로서 활용 가치가 높다. In this paper, we have proposed and experimentally performed a polarization and phase control method of an optical signal which has same wavelength with the optical carrier to improve phase characteristics of a continuous wave(CW) generated by the double sideband-suppressed carrier(DSB-SC) as one of the famous photomixing technique for making sub-millimeter and terahertz waves. A polarization and phase controlled optical signal has been coupled with the general DSB-SC on an optical coupler. The output of the optical coupler is then photomixed by a photomixer. From our analysis and measurement results, we have found that the amplitude of the generated sub-mm and terahertz CW signal is higher 1.5 dB and the phase noise is lower about 3 dB@10 kHz offset frequency than the general DSBSC. Consequently, since our proposed method has improved the amplitude and phase noise of CW signals in the sub-mm and terahertz bands, it can be helpful results to make low cost CW generator in sub-millimeter and subterahertz bands.

TWO-FREQUENCY CONTINUOUS WAVE ULTRASONIC SYSTEM FOR TEMPERATURE MEASUREMENT IN AN INFANT INCUBATOR

In this paper, we develop a new ultrasonic measurement method based on the speed of sound to measure the temperature. The average temperature of the air between the pair of ultrasonic T/R transducers is positively associated with the speed of sound. The method presented here is based upon the comparative phase shifts generated by two continuous ultrasonic waves with different but closely spaced frequencies. In the infant incubator, two low cost 40 kHz ultrasonic transducers are set face to face and used to transmit and receive ultrasound. Two frequencies are transmitted serially, each generating its own phase shift. Comparison of the phase shifts allows a highly accurate evaluation of the ultrasonic velocity when the distance between the transmitter and receiver is fixed. Ultrasonic velocity measurement system can provide a quick and precise monitoring of the temperature in an infant incubator. A single-chip microcomputer-based two-frequency continuous wave generator and phase detector was designed to record and compute the phase shift information and the resulting temperature, which is then sent to PC. The PC is used for calibrating the system and recording or controlling the temperature in an infant incubator. Experimentally, the accuracy of temperature measurement was found to be within ±0.02 °C when the distance between the transmitter and receiver is 1 m. The main advantages of this ultrasonic temperature measurement system are high resolution, low cost, and ease of implementation.

Multiple-frequency continuous wave ultrasonic system for accurate distance measurement

A highly accurate multiple-frequency continuous wave ultrasonic range-measuring system for use in air is described. The proposed system uses a method heretofore applied to radio frequency distance measurement but not to air-based ultrasonic systems. The method presented here is based upon the comparative phase shifts generated by three continuous ultrasonic waves of different but closely spaced frequencies. In the test embodiment to confirm concept feasibility, two low cost 40 kHz ultrasonic transducers are set face to face and used to transmit and receive ultrasound. Individual frequencies are transmitted serially, each generating its own phase shift. For any given frequency, the transmitter/receiver distance modulates the phase shift between the transmitted and received signals. Comparison of the phase shifts allows a highly accurate evaluation of target distance. A single-chip microcomputer-based multiple-frequency continuous wave generator and phase detector was designed to record and compute the phase shift information and the resulting distance, which is then sent to either a LCD or a PC. The PC is necessary only for calibration of the system, which can be run independently after calibration. Experiments were conducted to test the performance of the whole system. Experimentally, ranging accuracy was found to be within ±0.05 mm, with a range of over 1.5 m. The main advantages of this ultrasonic range measurement system are high resolution, low cost, narrow bandwidth requirements, and ease of implementation.