Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Patent
1995-11-02
1998-03-24
Blum, Theodore M.
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
342372, H01Q 322, H01Q 324, H01Q 326
Patent
active
057317909
ABSTRACT:
A compact free-space/solid optics phased array antenna/transducer optical controller is disclosed that uses the principle of in-phase (I) and quadrature (Q) vector modulation via two dimensional (2-D) spatial light modulators (SLMs). The SLMs are used as distributed optical gain/amplitude control devices. The system can be fed by four independent lasers where one pair of lasers must be mutually incoherent (or their beat frequency is not in the interested spectrum) with the other pair of lasers. These lasers are modulated (directly or externally) by separate forms (different phase shifts: 0, 90, 180, 270) of the input source signal/modulated radio frequency (rf) carrier. Each of the four different sets of light beams (each set containing N light beams; N=Total antenna/transducer elements in phased array) is independently amplitude modulated by the 4X N modulating pixels of the SLM. Depending on the phase and amplitude of the carrier required on the nth antenna/transducer element, laser beams from any two of the four sets modulated by the nth pixel location of two of the N-element sub-areas of the SLM are optically combined in intensity via a photosensor (linear summation of rf signals). In a similar fashion, this can be independently done for all N elements of the phased array. The optical combining is done in a compact fashion, via free-space/solid optics or fiber-optics. In the preferred embodiment of the invention, a grey scale nematic liquid crystal SLM is used for amplitude modulation, although other SLMs can be used such as deformable mirror devices (DMDs), magnetooptic SLMs, multiple quantum well device SLM, and ferroelectric liquid crystal SLMs. An alternative embodiment uses a single high power laser light source that is split by a 1:4 optical power splitter into four light sources which are each coupled to four external optical modulators, wherein the original signal source has four externally modulated optical beams to form four light sources that act as inputs to the optical controller.
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Blum Theodore M.
Steinberger Brian S.
University of Central Florida
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