Direct Digital Frequency Synthesis Technology Research Articles

Development of a high-voltage radio frequency power supply for quadrupole mass spectrometers with a wide dynamic measurement range

The core component of a quadrupole mass spectrometer is the quadrupole mass filter, serving a crucial role in ion analysis. It operates by applying two sets of high-voltage, high-frequency signals with equal amplitude and opposing phases through the radio frequency power supply, capitalizing on variations in the electric field and differences in mass-to-charge ratios to separate incoming ions. This study leverages direct digital frequency synthesis technology and multi-stage voltage amplification techniques to design a tailored radio frequency power supply for quadrupole mass spectrometers with a broad mass range. Practical testing demonstrates that this power supply generates radio frequency high-voltage signals with a peak-to-peak voltage ranging from 2.210 V to 4.220 kV at a resonant frequency of 1.240 MHz, facilitating the separation of ions with distinct m/z values. Furthermore, the radio frequency power supply is integrated into a Self-developed quadrupole mass spectrometer, enabling an assessment of the mass range, resolution, stability of the spectrometer. The results of these assessments confirm that the developed power supply accommodates scanning of m/z value ions in the range of 1 to 1067 while maintaining an absolute resolution of less than m/z = 1 units and an instrument stability of 2.00% over four hours.and keywords.

Self-Sustainable Long-Range Backscattering Communication Using RF Energy Harvesting

Radio-frequency (RF)-powered backscattering communication (BC) has many advantages, such as low-power consumption, battery-free, small size, low cost, full sealing, manual maintenance-free, and easy mass deployment. However, the weak RF energy harvested and the short BC distance have become the two critical obstacles in the real-world implementation of this potential technology. In this article, we propose a high-sensitivity RF energy harvesting (RFEH) and long-distance BC method, and for the first time, we demonstrate the RF-powered self-sustainable long-distance BC device named RFEH LoRa. In order to improve RFEH sensitivity, an ultralow-power (ULP) consumption voltage monitoring and startup control circuit topology is designed to reduce the power consumption to 245 nanowatt (nW) during the accumulation of RF energy. While in order to increase the BC distance, a direct digital frequency synthesis technology is used to generate a linear frequency modulation square wave sequence conforming to the LoRa specifications based on the ULP microcontroller unit, and the square wave is used to drive an RF switch to achieve long-distance BC of hundreds of meters. Test results show that the instantaneous BC current is as low as 130 microampere ( μA), and the standby current is only 52 nanoampere (nA). RFEH LoRa is implemented with commercial off-the-shelf components. It can self-startup by harvesting RF energy as low as -22.5 dBm, and send its sensing data to the receiver of 381-m away.

Development of on-line nondestructive testing device for welding cracks based on piezoelectric ceramic excitation

Perform real-time non-destructive testing of weld damage in various welded structures of steel to determine the degree of weld damage in order to make timely safety warnings to protect human life and property safety. In this paper, piezoelectric ceramics are arranged on both sides of the weld to find the best frequency of the excitation system. The sine signal of this frequency excites the piezoelectric ceramics on one side, and receives and analyzes the response signals of the piezoelectric ceramics on the other side. This paper uses direct digital frequency synthesis technology (DDS), power management circuit, differential amplifier circuit, band-pass filter circuit, phase detection circuit, amplitude detection circuit, etc. to design a system that can perform real-time nondestructive testing. The whole system can measure the changes of these signals in real time, and send the signals to the upper computer remotely. Analysis of these signals can initially determine the size and location of weld damage. The research results show that when the weld in the steel is damaged, the amplitude of the sinusoidal signal propagating through the weld will be attenuated, and the phase difference between the transmitted signal and the received signal will increase. This change is positively correlated with the degree of damage.

Controlling the light wavefront through a scattering medium based on direct digital frequency synthesis technology* *Project supported by the National Key Research and Development Program of China (Grant Nos. 2016YFB0401902 and 2016YFB0402001) and Key-Area Research and Development Program of GuangDong Province, China (Grant No. 2019B010926001).

Phase modulation is a crucial step when the frequency-based wavefront optimization technique is exploited to measure the optical transmission matrix (TM) of a scattering medium. We report a simple but powerful method, direct digital frequency synthesis (DDS) technology to modulate the phase front of the laser and measure the TM. By judiciously modulating the phase front of a He–Ne laser beam, we experimentally generate a high quality focus at any targeted location through a 2 mm thick 120 grit ground glass diffuser, which is commercially used in laser display and laser holographic display for improving brightness uniformity and reducing speckle. The signal to noise ratio (SNR) of the clear round focus is ∼ 50 and the size is about 44 μm. Our study will open up new avenues for enhancing light energy delivery to the optical engine in laser TV to lower the power consumption, phase compensation to reduce the speckle noise, and controlling the lasing threshold in random lasers.

Amplitude stability analysis and experimental investigation of an AC excitation signal for capacitive sensors

Low-noise capacitive sensor is widely used in electrostatic accelerometers and inertial sensors. An AC excitation signal is necessary to realize the amplitude modulation of the slow differential capacitance. But the amplitude stability of this AC excitation signal will directly influence low-frequency performance and dynamic range of capacitive sensors which results in the deviation of scientific requirements. In this paper, a stable AC excitation signal is realized based on the classical direct digital frequency synthesis technology. The mathematical model of amplitude stability is systematically set up, and there are four main influencing factors including transition time stability of the digital-to-analog converter (DAC), frequency stability of the crystal oscillator, voltage stability of the reference and gain stability of the band-pass filter (BPF). Each contribution of these four sources is theoretically analyzed. Finally, an evaluation prototype board is achieved to investigate the stability experimentally. Performance testing results show that the amplitude stability could reach approximately 16 ppm/Hz1/2 at 1 mHz under present optimal components selection, and transition stability of the DAC is the primary factor for further improvement.

Design of Function Signal Generator Based on DDFS

The system is designed to construct a Function Signal Generator based on Direct Digital Frequency Synthesis Technology (DDFS), in which MCU and FPGA are the key components and necessary peripheral circuits are provided. Its main modules are responsible for the formation of oscillogram, the frequency synthesis, the digital-to-analog transformation, the control of range, and back-stage treatment, the user interface and other necessary modules. MCU controls FPGA to generate the oscillogram and other control words, and the FPGA controls output waveform and frequency synthesis. Amplitude control is realized by 2 DA. Low-pass filter and Transistor push-pull power amplification circuit are used to increase the quality of the output waveform and its loading capacity, and display the signal on the LCD. The system constitutes of 2 DAC and the FPGA, so that realizes the expanded requirements of 1 Hz-1MHz of the four waveform output.

Research and Design of DDS Low Frequency Signal Generator Based on FPGA

Signal generator is the most widely used basic instrument in the field of electronic technology. The research and development of DDS low frequency signal generator based on FPGA has certain practical significance. With the core of EP2C8Q208C8N and the necessary peripheral analog circuit, a low frequency signal generator based on direct digital frequency synthesis technology is designed and its output performance is tested under the control of Verilog program.

Design of Charge Signal Generator Based on DDS Technology

The charge signal generator was designed by using Field Programmable Logic Gate Array(FPGA), Digital to Analog Conversion (DAC) circuit and charge conversion circuit. The Direct Digital Frequency Synthesis (DDS) was used to realize the frequency modulation, amplitude modulation and phase modulation of the signal. At the same time, the operating principle of the DDS technology and the design ideas of the analog circuit were described in detail. Under the Modelsim software platform, the function simulation of the program was carried out, and the real-time signal was captured and displayed by the SignalTap II logic analyzer. The correctness of the program was proved by the simulation results and the actual waveform. The voltage signal was converted into the charge signal, and joint debugging with the charge converter and the conditioning amplifier. Tests showed that the output waveform can meet the design specification and this proves the validity and reliability of the charge signal generator. The charge signal generator can be used as a standard signal source for the installation and commissioning of loose parts and vibration monitoring system, and it can be used for overhaul inspection of nuclear power stations.

Broad band direct modulation for chirp AM lidar

Compared with single-pulse detecting laser radar, the Chirp AM lidar with high range resolution, high accuracy, and high ability to counter jamming, has a broad application in the future, such as laser terminal guidance, topographical mapping etc. Based on direct digital frequency synthesis technology, we design and implement a broad band linear modulation signal generator, with output frequency of 4.8GHz, bandwidth of 600MHz. Adopting a high-frequency modulation circuit with specially designed, we realize broad band direct modulation on an 8W single laser diode with modulation bandwidth of 450MHz for the first time. It has established a base for development and application of compact chirp AM lidar.

Design of Dual High Precision High Resolution Frequency Synthesizer Based on AD9854

To obtain dual high-precision and high-resolution numerical control signal source, and accurately adjust the signal frequency, the paper proposed a method based on AD9854 direct digital frequency synthesis technology, design and implementation the dual high-precision and high-resolution frequency synthesizer. FPGA controlled AD9854 registers to achieve frequency modulation, and after amplification processing output by THS3001, increasing the output signal drive capability. Comprehensive consideration the anti-jamming measures, the system is stable and reliable, the output signal frequency range from 500Hz to 30MHz relative error is less than 10ppm, and can numerical adjust the sine and square wave frequency and has a sweep output mode. Compared with previous equipment, it reduces the system power consumption and volume.

Study on Ultrasonic Generator for Ultrasonically Assisted Machining

Ultrasonic vibration cutting can be widely used in lathe, planer, milling machine, grinding machine, thread processing and gear processing, etc. Ultrasonic vibration cutting system is composed mainly of ultrasonic generator, ultrasonic transducer, luffing rod, cutting tool, etc. Here, ultrasonic generator is the most important. The stand or fall of signal, which is produced by ultrasonic generator, has direct influence on anticipated effect and ability of ultrasonic machining. In order to generate a signal, which can be suitable for ultrasonic machining, ultrasonic vibration cutting system is studied, and ultrasonic signal generator based on direct digital frequency synthesis (DDS) is designed and conducted a cutting test with this ultrasonic machining system. The results show that the signal generator, which is made up by DDS technology, can generate the signal with stability, reliability and greater flexibility, and can be fully applicable to the ultrasonic machining.

Arbitrary Waveform Generator Based on Improved DDS Technology

This article describes an arbitrary waveform generator based on DDS (Direct Digital frequency Synthesis) technology. The arbitrary waveform generator can easily generate DC, square wave, sine wave or any other arbitrary waveform in mill volt or even microvolt level. The generator uses ARM and 51MCU dual-processor system framework. In the system design, we use multiple reference frequency source and dynamically generated waveform data method to generate waveform, which can effectively improve the stability and reduce the distortion of the output waveform.

Design of Phase-Shift Signal Generator with High Precision Used for Particulate Detection

Particulate detection, which is based on lock-in amplifier technology, requires a phase-shift signal generator with wide frequency range and high phase shift precision. Since the current phase-shift signal generator has a deficiency of low precision in high frequency range, the author designed a phase-shift generator which adopts direct digital frequency synthesis technology, and expresses hardware design principles of the system. This paper focuses on the design of hardware and software concerning high precision phase shift and amplitude closed-loop control. The experimental results indicate that the output signals have a high accuracy in phase difference, frequency and amplitude under a wide frequency range and this system achieves the requirements of particulate detection.