Abstract: A head mounted projection unit (16) and system (30) is disclosed. The unit includes a tapered optical relay that allows the use of a simple optical projection system. The unit further includes structure for allowing the transmission of images having both low resolution portions and high resolution portions.

Abstract: A system including coding and decoding circuits provides for resolution of the phase ambiguities in pragmatic trellis-coded PSK modulation transmissions. An error correcting coder, such as a convolutional encoder, precedes the modulator for reducing the effect of noise in inducing phase errors. A corresponding decoder appears at the reception end of the communication system. A differential encoder and decoder automatically remove the possible phase ambiguities, and operate in conjunction with the error correcting encoder and decoder. Each of the ambiguity-removal differential encoder and the decoder act as an operator upon its input signal. In order that both the error correcting encoder and the ambiguity encoder immediately precede the modulator, the ambiguity removal circuitry is placed between the error correcting encoder, and is constructed as a combination of differential encoder and inverse differential encoder.

Abstract: A symmetrical link device for linking first and second coplanar devices each movably mounted in a frame such that when one of the first and second coplanar devices is moved, a substantially equal and opposite motion is imparted to the other of the first and second coplanar devices.

Abstract: A passive microwave device combines energy from two microwave communication frequency bands into a common waveguide. Reciprocally, the device separates energy from two microwave frequency bands carried in a common waveguide into separate waveguides for each frequency band. The coupling is accomplished by means of probes that pass between the waveguides. The device can be used for the combination/separation of energy in the X-band and the Ku-band, wherein the Ku-band energy is coupled into/out of a square common waveguide by means of symmetrically positioned coaxial RF coupling probes. The coupling probes extend into both the common waveguide and also into rectangular Ku-band only waveguides. The X-band and Ku band are thus combined and/or separated passively for dual or multi-band antenna feeds in a compact, low cost package. The common waveguide is constructed to include a filter that substantially attenuates any Ku-band energy that would otherwise propagate towards the X-band input/output port.