The Research On Design Method Of Guided Wave Radar Level Gauge Echo Signal Processing Module

Compared to other conventional level measurement instruments, guided wave radar level gauge as a rangefinder has a lot of advantages, such as high accuracy and reliability, good real-time, capable of measuring in harsh environments, etc., so it is widely used petroleum industry、chemical industry and other industrial fields. With the quantity demanded of guided wave radar level gauge on the market is gradually increasing, major companies have a growing attention on the design and development of guided wave radar level gauge.This paper introduces the guided wave radar level gauge distance based core technology—the principle of time domain reflectometry, then proposes design specifications and performance requirements of guided wave radar level gauge demand. Guided wave radar level gauge in this paper is analyzed and designed from four separate modules: machine design circuit, pulse transmitting and receiving circuit, echo signal processing circuit and the communication display circuit. Finally this paper gives the overall design scheme of guided wave radar level gauge system. The main contents ars listed as follows:(1) The generation method of narrow-pulse signal: avalanche transistor is used in the design of narrow pulse generator in this paper, the circuit structure is simple, less requirements on the PCB board, low-cost. Then in ADS software establish an equivalent circuit model, we can get the best parameter values for each component after optimized, the width of measured pulse is 8ns and the amplitude of measured pulse is 1.5V.(2)The processing method of echo signal: Focuses on the methods to achieve equivalent time sampling. In this paper we select the sampling gate bridge to achieve signal broadening on the timeline. The design key of sampling gate circuit is to generate symmetric sampling pulse and delayed pulse. After analyzed and compared, we select the AD company’s delay chip AD9500 to achieve pulse delay 8Hz, select a transformer to achieve symmetric sampling pulse. Finally signal is stretched on the time axis to facilitate subsequent signal processing.The design core of hardware circuit is on the basis of medium-capacity enhanced microprocessor STM32F103 VF, then this paper display a detailed analysis and design of hardware circuit of power module、signal processing module and communication module. The main part of the software includes circuit design processes, the echo signal processing algorithms, keys and LCD screen display, serial communication modules and system auxiliary program and so on. This paper studies mainly the design of hardware circuit.Finally, this paper processes a guided wave radar level gauge that meets the design specifications according to the design scheme, after field testing, we analyze and summarize the test results. Measured results are consistent with the design requirements,guided wave radar level gauge has a lot of advantages of low loss, strong anti-interference, high accuracy.