Automatic Test Technology Based On Amplitude-Frequency Characteristics

The amplitude-frequency characteristic is a network performance is the most intuitive reflection, occupies an important position in the modern electronic measurement. This article focuses on the works of the amplitude-frequency characteristic test, after market amplitude frequency characteristics tester to analyze the situation, determine the system performance and the overall design. According to the requirements of the design, the design of an amplitude-frequency characteristics of automatic tester. This design mainly to sweep-signal generating circuit, the gain control circuit, the signal processing unit, the man-machine interface, GUI user interface composed of several parts. Sweep signal generating circuit uses low-power DDS chip AD9833, generate the sine wave of amplitude adjustable. The advantage of having a fast frequency switching time, the high frequency resolution, programmable control. Based on the ARM Cortex-MO32microcontroller lpc111x in series to achieve the measured signal detection. Plus gain control circuit, so that this amplitude-frequency characteristics tester automatically able to adapt to a variety of testing requirements. With LCD display, convenient debugging, performance is stable and reliable, able to automatically stepping measurement range of the full-band, key functions, preset measuring range and step frequency, can be more carefully observed amplitude-frequency characteristic diagram test, the amplitude-frequency tester can output the valid values for tunable sine wave, and no obvious distortion, full-band magnitude error of2%, the output sine wave frequency range to100HZ-5kHZ, and AC signal measurement accuracy of0.07%, to distinguish rate of0.01V, the output impedance of less than10Ω, the input impedance is greater than100k.