United States of America As Represented by the Secretary of the Air Force

Paul H Carr

John S Derov

Kenneth R Laker

James Robert Reid

Steven D Mittleman

David Da-Wei Liu

Alan J Budreau

Jose H Silva

A reconfigurable photoconducting antenna is created on a semiconductor substrate. At equilibrium, the semiconductor is semi-insulating, and therefore appears as a dielectric. Illuminating a region of the substrate results in the generation of free carriers in the substrate and allows the creation of a conductive region (semi-metallic) in the substrate. This conductive region functions as the radiating element of the antenna. Controlling the pattern of the illuminated region directly controls the pattern of the radiating antenna. By using a digital micromirror device (DMD&trade;) to control the pattern of the light, a desired antenna design may be placed on the semiconductor substrate. The pattern can be dynamically adjusted simply by changing the position of the individual mirrors in the DMD&trade; array. The device operates through a standardized digital interface and can be switched between patterns in a period of approximately 20 microseconds. The pattern of the DMD&trade; can therefore be readily and easily controlled through the use of a digital control system.

Spatially light modulated reconfigurable photoconductive antenna

First and second tandemly positioned electrically biased semiconductor members radiate microwave energy in response to the receipt of an excitation light beam having two wavelengths related to the bandgaps of the members. The projected microwave beam may be made more narrow and directional if two of the members are electrically biased at the same time. An inefficient frequency doubler generates the two wavelength beam enabling a single light beam to excite both members in a simple, rugged photoconductive antenna element.

Three dimensional reconfigurable photoconductive antenna array element

The 19.1 propagation X-cut of berlinite (AlPO.sub.4) has been discovered to have cubic temperature compensation for surface acoustic waves (SAW). The temperature variations of frequency or time delay over a 35.degree. to 85.degree. C. temperature range are comparable to ST-quartz. However, berlinite has at least twice the piezoelectric coupling. This is essential for low insertion loss, broadband SAW devices such as filters and correlators. In addition, 19.1 propagation, X-cut berlinite has lower volume wave spurious than ST-cut quartz.

Temperature compensated berlinite for surface acoustic wave devices

The input transducers of a multichannel surface acoustic wave device are electrically connected in a series or series-parallel circuit arrangement and are connected to a single channel electromagnetic wave transmission line through an inductor. The inductance value of the inductor is chosen such that minimum transducer insertion loss is achieved at the center frequency of the midband channel. The circuit arrangement is selected which achieves optimum coupling to the midband channel subject to the constraint that the insertion losses of all the remaining channels, measured at their respective center frequencies, lie at or near the above optimum value within an acceptable prespecified margin.

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Bedford, MA, United States of America

Paul H Carr