Stabilization of the backward wave oscillator frequency for operation with high quality resonators

This article describes the performance of a backward wave oscillator, stabilized with phase locked loop. The backward wave oscillator is locked to the frequency of a direct digital synthesizer using an automatic phase locked loop. The direct digital synthesizer is playing the role of tuning part in the suggested frequency synthesizer. Mathematical evaluations of the stability, phase noise and locking speed of the suggested frequency synthesizer are obtained. The optimization technique of frequency synthesizers parameters is presented. This allows to get the maximum response speed and the lowest phase noise and level of spurious with fine tuning (less than 1 Hz). It was shown that the order and type of loop filter in the frequency synthesizer will affect simultaneously the response speed, phase noise and spurious level. The results of this paper shows that the frequency synthesizer can be used in small samples properties measurement using open resonators.

A Wireless Animal Robot Stimulation System Based on Neuronal Electrical Signal Characteristics

As a stimulus signal, coded electrical signals can control the motion behavior of animals, which has been widely used in the field of animal robots. In current research, most of the stimulus signals used by researchers are traditional waveforms, such as square waves. To enrich the stimulus waveform, a wireless animal robot stimulation system based on neuronal electrical signal characteristics is presented in this paper. The stimulator uses the CC1101 wireless module to control animal behavior through brain stimulation. The LabVIEW-based graphical user interface(GUI) can manipulate brain stimulation remotely while the stimulator powered by battery. Additionally, The spikes of animals have been simulated by this system through Direct Digital Synthesizer(DDS) algorithm. The GUI enable users to customize the combination of these analog spike signals. The recombined signals are sent to the stimulator through CC1101 as stimulus signals. In vivo experiments conducted on five pigeons verified the efficacy of the stimulation mechanism. The analog spike signal with an amplitude of 3-5V successfully caused the pigeon’s turning behavior. The feasibility of the analog spike signals as stimulus signals was successfully verifified. Increased the diversity of stimulus waveforms in the field of animal robots.

Implementation of the Configuration Structure of an Integrated Computational Core of a Pulsed NQR Sensor Based on FPGA

This paper presents a method for implementing the configuration structure of an integrated computational core of a pulsed nuclear quadrupole resonance (NQR) sensor based on a field-programmable gate array (FPGA), which comprises the following modules: a three-channel direct digital synthesizer (DDS), a pulse sequence shaper and a software-defined radio. Experimental studies carried out using the in-circuit analyzer SignalTap Logic Analyzer have confirmed the reliability of the correct and stable operation of the functional modules of the configuration structure at all stages of signal transformations, starting from the formation of the envelope of the excitation pulses and ending with the obtainment of low-frequency quadrature signals at the outlet of the compensating filters. The time and frequency dependences of the amplitude of the output signals generated using the DDS based on a 48 bit phase accumulator are investigated. This development can be used when creating pulsed coherent NQR sensors in the frequency range of 1 MHz–50 MHz.

SIMPLIFIED VERSION OF DIRECT DIGITAL FREQUENCY SYNTHESIZER

Рассмотрена оригинальная упрощенная схема прямого цифрового синтезатора частоты (Direct Digital Synthesizer, DDS). Упрощение состоит в отсутствии довольно громоздкой синусоидальной таблицы при сохранении основных достоинств этого метода синтеза. The original simplified scheme of a direct digital frequency synthesizer (DDS) is considered. The simplification consists in the absence of a rather cumbersome sinusoidal table while preserving the main advantages of this synthesis method.