Projeto de um posicionador para caracterização de diagramas de irradiação de antenas

Abstract

Systems for antenna radiation pattern measurement are fundamental for the characterization and validation of prototypes designed by electromagnetic simulators. As part of this system, a commercial positioner has very high cost, a fact that resulted in the elaboration of the project described here. Such a design implements a positioner with one axis, automated, efficient, low cost and that allows interfacing with other devices that include this system, besides the user. The development of the positioner includes an interface in Matlab, used for the control of the positioner and to read and store the measured data from a spectrum analyzer. The communication between the interface and control of hardware is performed via Ethernet TCP/IP (Transfer Control Protocol/Internet Protocol), unlike other modes of communication, such as USB, serial and parallel, which have distance limitations between two connection points. The control is made through an Arduino, which is responsible for activating the transistors of the stepper motor driver. For each motor step, the signal as received by the antenna under test is performed by the spectrum analyzer which is connected to the interface and transmits the measured data storage and plotting. Communication with the Arduino is performed through a Shield Ethernet, which receives commands from an HTML page (HyperText Markup Language) hosted on the own Shield and made available for external access. After receiving a command from any HTML or TCP/IP client, Shield passes this command to the Arduino, which in turn is responsible to perform the desired function. The Driver power is needed, since the pin I/O (Input/Output) a Arduino does not provide enough current to drive the coils of a motor. The project described here can be used for measurement systems in anechoic chambers and in free space.