Rf Power Measurement Methods And Circuit Design

Measurement technique is important and necessary for science development. Even we can say that there would be no science if there were no measurement technique. Voltage, current and impedance are basic measured parameters in DC circuit or low-frequency circuit, but in radio frequency (RF) system, power-measuring is as important as voltage-measuring. The accuracy requirement of RF power-measuring is more and more high with the rapid development of communication and broadcast television industry.A new RF power-measuring method and the measuring circuit are introduced in this paper. Based on the formula P=1/2UI cosφ(U and I are peak value of voltageand current), analog multiplier, low-pass filter, are used in the design of RF power-measuring circuit, and this method is called multiplication style RF power-measuring method. Compared with feed-through style RF power-measuring method, this design reduces error of reading out power value. The power value on the load can be read out directly by using only one current meter (feed-through style using two current meters). The current through the current meter is direct proportion with measuring power.The principles of multiplication style RF power-measuring method and feed-through style RF power-measuring method are introduced in this paper. Design parameters of current transformer , bleeder, analog multiplier ,low-pass filter, operational amplifier are given for the RF power-measuring circuit. The same and different points of two kinds of measurement method are analyzed. Analysis shows that the measurement accuracy of multiplication style RF power-measuring method is higher than that of the feed-through style RF power-measuring method.In order to verify the feasibility of design circuit, multiplication style RF power-measuring circuit was simulated using PROTEL99se software. The simulation result justifies that the current through electric current meter is direct proportion with measuring power. Experiment was carried out to verify the RF power-measuring circuit. The result of analysis improves the feasibility of circuit design.