Modulated Signal Source Research Articles

Research on Modulation Method and Characteristic Analysis of Faraday DC Optical Measurement System

The optical current transformer is an important content in smart grid research field. When the Faraday DC optical measurement system was used in DC current measurement, the low frequency noise caused by photo detector and measured signal were overlapped, which makes the measuring accuracy decrease. To solve this problem, the noise of photo detector is analyzed. Then, the frequency modulation is proposed for spectrum shifting. Furthermore, the principle of modulation method is deduced in formula, and the characteristics of deferent frequency are also analyzed. On this base, modulation signal source is designed. With LabVIEW program, the signal from modulation source is acquainted and analyzed. The results show that this modulation method can realize spectrum shifting and the designed signal source is able to generate waveform needed.

Design and Study on Analog Modulation Signal Source Based on AT89C51 Microcontroller

At present, the analog signal source in a traditional sense is far away from being sufficient to meet the needs of the modern development. Besides, the emergence of the direct digital synthesis (DDS) technology brings about a new vitality to the electronics technology of the modern times. However, because of the characteristics of the digitization, the direct digital synthesis still has the problems (the limited the output frequency range and the large spurious output). For this reason, it is particularly important to solve these problems currently. In this paper, the author carries out an analysis on the circuit characteristics of the DDS system and the analog modulation signal source system, studies their performances and characteristics, and also makes a design on both software and hardware that are based on the analog circuit and AT89C51 microcontroller system. This system is mainly composed of the microcontroller control module, the frequency synthesis module and the multiplier module. The DDS frequency synthesizer can work stably and is easy to realize. Also, the high resolution of its output frequency can meet the requirements of people in the modern times.

RF Peak Power Calibration of Modulated Signals

A new calibration method of a power sensor for measuring the peak power of digitally modulated signals is introduced. This method uses an amplitude-modulated sine-wave source and is relatively simple to the currently available method that uses a digitally modulated signal source and an oscilloscope. Basic theory and calibration procedures for measuring the correction factor for peak power are described. Using a commercial peak power sensor that is calibrated with the proposed method, the peak power of a Global System for Mobile Communications at 900 MHz modulated signal is measured and compared with that measured by an oscilloscope. Various examples of choosing the calibration parameters are also discussed. The best uncertainty in the calibration of a peak power sensor is estimated to be 0.34% (k = 2).

Optimization of electro-optical parameter of optical frequency standard system based on modulation transfer spectroscopy technique

According to the mechanism of nearly degeneration four-wave mixing that occurs in a sufficiently nonlinear resonant gaseous medium caused by phase-modulated laser beam, the electromagnetism excitation and dynamic evolvement of modulation transfer spectroscopy(MTS) technique is studied theoretically, and then mathematic models of dispersion spectrum and absorption spectrum of MTS are established too. The results show that when the frequency of modulation signal source is equal to 0.72 times the linewidth of absorption line approximatively, the intensity of dispersion signal reaches a maximum value; it can obtain a better frequency-stabilization result when modulation factor is set to be nearly 0.3; the instability of demodulation phase has a big effect on the absorption spectrum, but on dispersion spectrum, the effect is tiny when the demodulation phase fluctuates near 90.

Timing Jitter Measurement of Intrinsic Random Jitter and Sinusoidal Jitter Using Frequency Division

This paper presents a new method for measuring random timing jitter or sinusoidal timing jitter in signals of telecommunication devices. The method uses a divide-by-M circuit to reduce the frequency and the number of clock samples, and applies the Hilbert transform to measure the timing jitter. This new frequency division method is validated with experimental data from a serializer-deserializer device and a modulated signal source generating a 2.5 GHz FM signal.