Abstract: A laser secure communications system is disclosed. The system utilizes a long laser cavity, the end reflecting members of which may be located many kilometers apart. One or more high gain laser amplifiers optically aligned within the long laser cavity provide the optical carrier energy. Laser oscillation only occurs if the remotely located end reflectors are optically aligned and if the laser gain is sufficient to overcome the round trip transmission loss. The optical carrier thus established is modulated and detected at either end of the laser cavity.

Abstract: Methods and apparatus are disclosed for substantially reducing the effect of the inherent transducer capacitance in a transducer-coupled electromechanical system which is subject to vibrational movement. First and second electromechanical transducers, mechanically coupled to the mechanical structure are interconnected by an electronic feedback network. The feedback network is characterized by very low input and output impedances thus overcoming the shunting effects of the inherent transducer capacitance. In preferred embodiments the feedback network is "electronically cooled" thereby providing low-noise damping.

Abstract: A class of two-terminal active networks which simulate low-noise-temperature resistors is disclosed. A single differential-input operational amplifier connected with a feedback resistor in an inverting amplifier configuration comprises the active element of the network. A resistive voltage divider feedback arrangement comprises the remainder of the circuit. Either positive or negative simulated resistors can be obtained with a wide range of equivalent resistance values and effective noise temperatures.

Abstract: A class of two-terminal active networks which simulate low-noise temperature resistors is disclosed. A single differential-input operational amplifier connected with a feedback resistor in an inverting amplifier configuration comprises the active element of the network. A dual-transformer feedback arrangement or a single transformer feedback arrangement comprises the remainder of the circuit. Either positive or negative simulated resistors can be obtained with a wide range of equivalent resistance values and effective noise temperatures.

Abstract: A wideband optical ring modulator is disclosed. A ring resonator containing a synchronous travelling wave electro-optic modulator is disposed external to a laser cavity. The invention provides a compact lightweight optical modulator which combines the power enhancement capabilities of a resonant cavity with the wideband capabilities of a travelling wave coupling modulator. The present invention is especially useful for, although not limited to, ultra-wideband infrared laser communication systems utilizing PCM techniques.

Abstract: An asynchronous multiplexer-demultiplexer for pulse-coded data transmission over a single communication link, such as a laser beam link, at a predetermined transmitter pulse clock rate sufficiently high to accommodate a plurality of source ports and corresponding destination ports wherein each source port includes a plurality of buffer memories for accumulation of data blocks to be transmitted, means for encoding the data source clock rate into a 20-bit word, and means for generating an interrupt signal to the transmitter. A priority interrupt system controls the transmitter to transmit blocks of data from the source ports on a predetermined order of priority giving sources of higher data rate higher priority. Each block of data transmitted is preceded by a header which includes a preamble and block sync codes, a source clock code, a source port identification (ID) code, and a source word length code.

Abstract: An antenna feed system having a very wide (multi-octave) bandwidth. The antenna feed comprises a plurality of nested annular cavities each parasitically excited by a pair of orthogonal two-point fed dipoles. The frequency selective properties of the dipoles and the annular cavities in conjunction with the focal distribution of the reflector or lens with which the feed is used results in a multiplexing of sub-bands across the total bandwidth. A modification of the end members of the two-point fed dipoles permits dual-plane and dual polarization monopulse operation of the feed system.

Abstract: A system for scrambling and descrambling the video portion of a television signal. At the transmitting end, the video is scrambled by shifting the phase angle of the carrier relative to that of the sidebands a constant amount. At each receiving site, the signal is unscrambled by locally deriving from the phase shifted carrier a carrier of the proper frequency, phase angle and amplitude. The locally generated carrier is then vector summed with the incoming phase shifted carrier to produce a carrier having proper phase angle.

Abstract: An improved seizure device for connecting coaxial cable transmission lines to electronic devices is disclosed. According to the invention, the center conductor of the coaxial cable is inserted in an opening between two tines of a conductive post which is electrically connected to the electronic circuitry. The outer conductor of the coaxial cable is inserted through a serrated ferrule. A single clamping nut provides a force which acts through the serrated ferrule, a guide clamp and a tapered seizure post holder to simultaneously clamp the inner and outer conductors for electrical and mechanical contact.

Abstract: An improved optical heterodyne receiver is disclosed. Novel control circuitry is utilized in the receiver to provide compensation and tracking for undesired phase and frequency excursions of both the received and the local oscillator signals. An optical heterodyne receiver such as that disclosed is especially useful in optical communications systems having wideband variations in the frequency of the received signal caused by Doppler shifts and angle-modulated noise components.

Abstract: An improved homodyne receiver for use in wideband optical communications systems is disclosed. The receiver utilizes dual channelization of the optical input signal in the manner of a Costas two-phase synchronous receiver. A novel beam-splitting/phase-splitting optical assembly is used to channelize the received and the local oscillator beams and insure the desired phase relationships. The receiver is capable of phase-locked operation in the presence of noise and frequency variations in the received and local oscillator signals.

Abstract: A laser oscillator circuit is disclosed which allows the operating frequency of the laser to be tuned over a wide range of frequencies in response to a wideband control signal. A laser oscillator such as that disclosed is useful in optical communications systems and especially in optical receivers utilizing a phase-locked control loop for tracking out frequency variations due to noise and the Doppler shifts.