1. MAPS : Microwave Antenna Plotting System Abstract Objects are visible because they scatter incident light. The work of Professor Nader Engheta suggests that man-made metamaterials can be manufactured to minimize scattering for certain frequencies of light, making them essentially invisible. The wavelengths for which a metamaterial becomes “invisible” depend on its structural dimensions. A metamaterial that reduces scattering in the optical regime requires features on a nanometer scale, making fabrication prohibitively expensive. To test Dr. Engheta's theories, experiments must instead be performed in the microwave regime, where larger wavelengths allow practical fabrication. However, since microwave radiation cannot be observed by eye, detection of scattering effects is nontrivial. MAPS is a microwave scanning system designed to solve this problem. It consists of a transmitting and receiving antenna, both operating in the microwave range. A two- dimensional representation of the transmitted field is produced as the machine moves the transmitter along a plane and measures the field at the receiver. By placing an object within the field and measuring the resulting differences in amplitude and phase, the object’s microwave scattering effect can be observed. These scattering results will allow empirical testing of Dr. Engheta’s invisibility theories. Authors Matthew Brendzel EE ‘10 Jason Joo EE ‘10 Alfred Wang EE ’10 Advisors Professor Nader Engheta Dr. Brian Edwards Team 12 Demo in GRW 379 10:30-11:30, 1:30-2:30 System Design VNA SoftwareHardware The Agilent E5071C VNA (below) is used to perform two-port measurements of the amplitude and phase of EM waves across multiple frequencies. MAPS consists of three major systems: the LabVIEW software, the physical hardware system, and the Vector Network Analyzer (VNA). The antennas occupy the same plane, which is enclosed by two parallel aluminum plates and sealed off at the edges with insulating foam. The machine is controlled by software coded in NI LabVIEW. The front panel interface (above) controls all functionality. The LabVIEW program communicates with the motor controller, which in turn sends pulse-width modulated (PWM) signals to the stepper motors. The scanner is supported by an aluminum frame (model at right). The frame includes channels for low-friction bearings, allowing two-dimensional motion of the mobile plate. Lin Engineering Silverpak 23D stepper motors were chosen for precision position control. A pulley system is used to change rotational motion from the motors to translational motion of the plate. Generated Path Object Antenna Results The path planning algorithm generates an appropriate path for the scanner to take (right). Using the collected data points from the VNA, LabVIEW generates a plot of the microwave field. Mathematica Plot of Empty Field LabVIEW Plot of Empty Field The transmitter and experimental object are fixed to the mobile plate, and the receiver is fixed to the stationary plate. The motors move the transmitter around the receiver in a grid-like pattern. The VNA measures microwave field data at appropriate points and a plot is generated in real time. LabVIEW Plot of Field With Object Mathematica Plot of Field With Object