A filter algorithm for receiver tracking loops assisted by inertial information

In traditional satellite navigation receivers, the parameters of tracking loop such as loop bandwidth and integration time are usually set in the design of the receivers according to different scenarios. The signal tracking performance is limited in traditional receivers. In addition, when the tracking ability of weak signals is improved by extending the integration time, negative effect of residual frequency error becomes more and more serious with extension of the integration time. To solve these problems, this paper presents out research on receiver tracking algorithms and proposes an optimised tracking algorithm with inertial information. The receiver loop filter is designed based on Kalman filter, reducing the phase jitter caused by thermal noise in the weak signal environment and improving the signal tracking sensitivity. To confirm the feasibility of the proposed algorithm, simulation tests are conducted.

ERROR ANALYSIS OF USING AUXILIARY VERBS IN WRITING DESCRIPTIVE TEXT

Grammar is complexity in learning English it makes many students often commit errors in learning. Making errors in writing is one of the processes for learning English .The aim of this research was to describe the students’ errors and its causes in using auxiliary verbs in the sentences. In this research, the writer limited the discussion on the error made by the students in using auxiliary verbs. The design of this research was quantitative approach in a form of descriptive analysis (percentage) that included observation, collecting the data the researcher used test as the instrument. The writer conducted the research to 31 students in first semester of English Literature in academic 2021/2022. The data were analyzed by using error analysis method. The error types were classified based on linguistic category, especially surface strategy taxonomy. The writer classified the types of error into omission, addition, misformation, and misordering. Among those four types, the most frequency error was misformation that reached 102 errors or 61.44% . the other finding was the sources of error which are divided into three categories. Those are interlingual errors, intralingual errors, and communicative strategies. Communicative strategies errors is the most common source of error, there were 45.78%

Research Progress on Terahertz Quantum-Well Photodetector and Its Application

Compared with other typical terahertz (THz) detectors, the quantum-well photodetector (QWP) has the advantages of high detection sensitivity, fast response, mature fabrication, small size, and easy integration. Therefore, it is suitable for high-speed detection and imaging applications at the THz band. Researchers, both domestic and overseas, have systematically studied material design and device performance of the THz QWP. The design of the device is such that the peak frequency error is within 8%, the maximum peak responsibility is 5.5 A/W, the fastest response speed is 6.2 GHz, the best noise equivalent power is ∼10−13 W/Hz0.5, and the spectrum range is 2.5–6.5 THz. In this article, firstly the basic principles and theoretical calculations of the THz QWP are described, and then the research progress of the THz QWP in our research group at imaging and communication is reviewed, which looks forward to its future development.

Design of sweep frequency signal source in residual stress detection platform based on Zynq

The signal generator based on DDS technology has high frequency and resolution, and is widely used in many fields such as instrument technology, radar, satellite timing, remote control and telemetry, and is one of the important directions of current signal generator research. In order to achieve a cost-effective, high frequency resolution signal source to stimulate the sensors in the residual stress detection system, this paper selects the Zynq-7020 on-chip system to control the 14-bit direct digital frequency synthesis chip AD9954 to obtain a 40Hz~1MHz sinusoidal signal output. Finally, the performance and technical parameters of the system are tested experimentally. The output signal of the signal source is stable, the signal-to-noise ratio is high, and the frequency error is within 0.1%.

Comprehensive Design Method of a High-Frequency-Response Fast Tool Servo System Based on a Full-Frequency Error Control Algorithm

With the development of optoelectronic information technology, high-performance optical systems require an increasingly higher surface accuracy of optical mirrors. The fast tool servo (FTS) based on the piezoelectric actuator is widely used in the compensation machining of high-precision optical mirrors. However, with the low natural frequency of mechanical structures, hysteresis of the piezoelectric actuators, and phase delay of the control systems, conventional FTS systems face problems such as a low working frequency and a large tracking error. This study presents a method for the design of a high-performance FTS system. First, a flexure hinge servo turret with a high natural frequency was designed through multi-objective optimization and finite element simulations. Subsequently, a composite control algorithm was proposed, targeting the problems of hysteresis and phase delay. The modified Prandtl–Ishlinskii inverse hysteresis model was used to overcome the hysteresis effect and a zero-phase error tracker was designed to reduce the phase error. The experimental results reveal that the tracking error of the designed FTS system was <10% in the full frequency range (0–1000 Hz).

Distributed Multistatic Sky-Wave Over-the-Horizon Radar’s Positioning Algorithm for the Marine Target

This paper establishes a distributed multistatic sky-wave over-the-horizon radar (DMOTHR) model and proposes a semidefinite relaxation positioning (SDP) algorithm to locate marine ship targets. In the DMOTHR, it is difficult to locate the target due to the complexity of the signal path propagation. Therefore, this paper uses the ionosphere as the reflector to convert the propagation path from a polyline to a straight line for establishing the model, and then the SDP algorithm will be used to transform a highly nonlinear positioning optimization problem into a convex optimization problem. Finally, it is concluded through the simulations that the SDP algorithm can obtain better positioning accuracy under a certain Doppler frequency error and ionospheric measurement error.

Simulation and Experimental Research on the Disturbance Behavior of a Sun-Tracking Solar Array Driven by a Stepping Motor

A sun-tracking solar array is an effective solution to the increasing energy demand of spacecrafts. However, the driving torque fluctuation of the solar array driving assembly (SADA) and its oscillatory motion lead to the micro-vibration problem of the spacecraft. In this article, a disturbance torque model of the sun-tracking solar array, which takes its friction and flexibility into consideration, is established. Furthermore, a test platform was built to measure the disturbance force/torque, and a solar array simulator (SAS) was designed to replace the solar array in the ground experiments. Finally, the disturbance torque of the SADA-driven SAS is simulated, and the model is validated by comparing the simulation results with the experimental results. These results show that the frequency error of the model is less than 0.648%, and the amplitude error of the corresponding frequency is less than 22.33%, which indicates that the proposed model can effectively predict the disturbance torque generated by the sun-tracking solar array in orbit. The research provides theoretical guidance for the system optimization design and micro-vibration suppression of spacecrafts.

Analysis of FBMC Waveform for 5G Network Based Smart Hospitals

Nowadays, many prevalent frameworks for medical care have been projected, studied, and implemented. The load and challenges of traditional hospitals are increasing daily, leading to inefficient service in the health system. Smart hospitals based on advanced techniques play a crucial part in advancing the health services of rural people. It spares the time and money involved in travel, and patient medical reports can be shared instantly with the experts regardless of geographical constraints. Currently, the role of technology in hospitals is limited due to various restrictions, such as the obtainability of a high spectrum, low latency, and high-speed network. In this paper, we focused on the implementation of an advanced waveform with high spectral performance. Filer Bank Multi-Carrier (FBMC) is considered a strong contender for the upcoming 5G-centered smart hospitals due to its high data rate, no leakage of the spectrum, and less sensitivity to frequency error. In addition, a comparison of the spectral utilization of orthogonal frequency division multiplexing (OFDM) and FBMC in terms of bit error rate (BER), peak power (PP), power spectral density (PSD), noise-PSD, capacity and magnitude, and phase response is illustrated. Numerical results show that the FBMC achieved a throughput gain of 1 dB and its spectral performance is better than the OFDM; hence, it is a better choice for the proposed application compared to the current standard OFDM.