Abstract: The invention is a method of calibrating the sensor system of a wideband direction finder using a noise source. The sensor system includes at least two wideband tuners, and an analog/digital (A/D) converter connected to each wideband tuner. The calibration method involves selecting a common set of center frequencies for each of the wideband tuners. The wideband tuners receive a signal from the noise source on a per data frame basis. The passband of the received signal is then divided into a number of time-sampled data frames. For each time-sampled data frame, both a gain variation and a phase variation are calculated for the noise received at each wideband tuner. Gain and phase differences between the signal received by each wideband tuner within the same frame are compared. Based on the time-sampled data collected, the phase and gain differences for the signals received at the tuners which have not been previously mapped can be determined.

Abstract: A personal identification instrument is comprised of a substrate, and carried on the substrate: a photograph and/or a personal signature, personal information relating to the legitimate holder of the instrument, and an encrypted machine readable security code carried by the instrument, the code being comprised of a combination of digitized personal information and a digitized descriptor of the photograph and/or personal signature.

Abstract: A first terminal for use in a time division duplex communication system comprising apparatus for automatically, successively, repetitively and alternatingly transmitting and receiving compressed signals to and from another terminal via a single transmit and receive time divided channel, including apparatus for changing a transmit and receive mode of the first terminal in synchronism with an opposite transmit and receive mode of another terminal, apparatus for receiving a timing signal which is the same timing signal received by another terminal, and apparatus for changing the mode at intervals determined from reception of the timing signal.

Abstract: A system for transmitting FM signals comprised of apparatus for receiving an input data signal, apparatus for precompensating the received data signal, apparatus for applying the precompensated data signal to a constant envelope modulator to provide a modulated signal, apparatus for applying the modulated signal to a power efficient non-linear amplifier and transmitting a signal resulting therefrom, apparatus for receiving the transmitted signal in an I-Q receiver, and apparatus for filtering the received transmitted signal for the precompensation, to obtain an output data signal representative of the input data signal.

Abstract: A compact, mechanically-steered antenna especially applicable for mobile terminals for receiving signals broadcast by satellites, is adjustable in azimuth and elevation. The antenna's active element can be rotated in azimuth through 360 degrees. Rotary couplings in the signal path are avoided by means of a flexible coupling. The flexible coupling conveniently comprises a torsion spring and the feedline, typically a highly-flexible coaxial cable, passes through it. The active element is mounted upon a first support member and rotatable relative to it about the boresight of the antenna. A second support member is mounted upon a base member and rotatable relative to it in azimuth. The first second support is mounted upon the second support by means of a hinge coupling which permits pivoting of one support member relative to the other to adjust the elevation angle.

Abstract: A system for transmitting FM signals comprised of apparatus for receiving an input data signal, apparatus for precompensating the received data signal, apparatus for applying the precompensated data signal to a constant envelope modulator to provide a modulated signal, apparatus for applying the modulated signal to a power efficient non-linear amplifier and transmitting a signal resulting therefrom, apparatus for receiving the transmitted signal in an I-Q receiver, and apparatus for filtering the received transmitted signal for the precompensation, to obtain an output data signal representative of the input data signal.

Abstract: The present invention relates to a method of encoding speech comprised of processing the speech by harmonic coding to provide, a fundamental frequency signal, and a set of optimal harmonic amplitudes, processing the harmonic amplitudes, and the fundamental frequency signal to select a reduced number of bands, and to provide for the reduced number of bands a voiced and unvoiced decision signal, an optimal subset of magnitudes and a signal indicating the positions of the reduced number of bands, whereby the speech signal may be encoded and transmitted as the pitch signal and the signals provided for the reduced number of bands with a bandwidth that is a fraction of the bandwidth of the speech.

Abstract: A method of fabricating a strongly photosensitive optical waveguide is comprised of locally heating at least a portion of a weakly photosensitive optical waveguide for a period of time sufficient to increase the density of defects associated with photosensitivity in the heated portion of the waveguide core.

Abstract: An antenna suitable for mounting upon vehicles, vessels or aircraft for communication via satellites comprises a conductive ground plane and a radiator element in the form of a conductor helically wound to define a frusto-conical shape with the ground plane as its base. The conductor may be formed upon a dielectric substrate in the shape of a truncated cone. The dimensions of the antenna element are selected so that the pitch angle of the radiator element varies between a minimum of about 6 degrees and a maximum of about 8 degrees. The required pitch angle may be achieved when the cone angle of the frusto-conical shape is between 5 degrees and 20 degrees and the mean diameter of the frusto-conical shape is between 0.3 and 0.47 of a mean operational wavelength predetermined for the antenna. The length of the radiator element is selected to be the minimum needed to sustain a wave.

Abstract: A mechanically steerable antenna suitable for mobile earth stations of satellite communication systems comprises a support member mounted upon a base member and an active antenna element or array of elements mounted upon the support member. The antenna element or array of elements is rotatable about its boresight relative to the support member. The support member itself is rotatable in azimuth relative to the base member. The rotation axis of the antenna element or array of elements and the rotation axis of the support member are mutually inclined by a predetermined angle corresponding to the mean elevation angle of the satellite. The antenna includes drive means for rotating the support member relative to the base member, and a flexible coupling interconnects the base member and the antenna element.

Abstract: An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask. The phase mask is held in close proximity to the optical fiber. Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask.

Abstract: In order to reduce size and facilitate incorporation into planar multi-layer microwave integrated circuits, a microwave hybrid, specifically a Magic-Tee, is formed using microstrip circuit elements and aperture coupling. The Magic-Tee comprises a ground plane interposed between dielectric printed circuit boards. The outermost surface of one of the boards carries a Tee circuit comprising microstrip branch arm conductors with a microstrip conductor projecting transversely from its middle, the Tee junction, to form the leg of the Tee. The outermost surface of the other board comprises a line in the form of a microstrip conductor. An aperture is provided in the ground plane at a position between the Tee junction and an underlying part of the line conductor. Various Tee junction configurations, such as Y or .DELTA., may be implemented also. The magic Tee may be an integral part of an MIC or MMIC device.

Abstract: A group demodulator for FDMA/PSK input signals comprising a down-converter for the input signals to convert these signals into in-phase and quadrature-related signals which are applied through analog-to-digital converters to a digital transmultiplexer. The digital transmultiplexer converts the signals into a number of channels of PSK modulated data. The output of each analog-to-digital converter is applied to an automatic threshold controller which detects the statistical bias of the input signal amplitude. Each automatic threshold controller provides an analog reference signal which is applied to a reference input of the associated analog-to-digital converter. The reference signal corrects any DC offset error for the analog-to-digital converter and prevents degradation in energy per bit-to-noise density ratio.

Abstract: Efficient, narrow-band rocking filters have been made in polarization-maintaining monomode optical fiber by photoinducing periodic birefringent gratings along the length of the fiber. These gratings, fabricated with a period chosen to provide synchronous coupling between the two principal states of polarization of the LP.sub.01 mode at a preselected wavelength, gently rock to and fro the principal polarization axes of the fiber. To photoinduce the grating, the fiber is exposed periodically along its length to a U.V. light beam which is incident at right angles to the geometrical axis of the fiber and is directed .pi./4 radians with respect to the principal axes. Efficient polarization mode conversion at 1.3 .mu.m with the fiber gratings are obtained.

Abstract: In a magnetic compass of the kind in which a sensor derives coordinates of a sensed magnetic field, automatic correction of hard-iron and soft-iron distortions is achieved by storing a set of measured values of the magnitude of the sensed magnetic field for different discrete directions of the alignment axis of the compass relative to an estimated origin. If measured values have been accumulated for more than a predetermined number, but not all, possible directions, values are interpolated for the remaining directions to provide a set of measured and interpolated values defining a substantially elliptical locus of the sensed magnetic field vector (E.sub.T.) New coordinates for the estimated origin are derived and the measured values adjusted to take account of changes in the estimated origin. The heading is corrected for displacement of the origin due to hard-iron effect and for ellipticity of the locus due to soft-iron effects.

Abstract: A microwave polarizing lens structure having two concentric hemispherical arrays of metallic linear scattering elements (dipoles) supported by thin walled dielectric shells. It has the property of controlling the sense of polarization, the ellipticity ratio and shape of the radiation pattern of the antenna contained within it.

Abstract: A two-channel optical fiber fused coupler comprising two optical fibers, each with a core and cladding, fused together at a narrow tapered waist. The first channel is at a wavelength of .lambda..sub.1 and the second channel is at a wavelength of .lambda..sub.2 where .lambda..sub.2 is longer than .lambda..sub.1. The coupler is fabricated to have a characteristic wavelength .lambda..sub.0 such that for wavelengths .lambda..sub.2 longer than .lambda..sub.0 coupling occurs and for wavelenghts .lambda..sub.1 shorter that .lambda..sub.0 the light at .lambda..sub.1 is core guided throughout the coupler and thus does not couple across.

Abstract: This invention relates to a method of creating an index grating in an optical fiber comprising disposing a slit mask containing one or more slits over a side of an optical fiber, illuminating the fiber through the slit mask by substantially monochromatic ultraviolet light for a short interval, whereby an index grating line is created and stored in the core of the fiber.

Abstract: A fused twin biconical taper fiber optic splitter comprised of a pair of non-identical monomode or nominally monomode optical fibers having predetermined cladding diameters fused at respective narrowed waists, the cladding diameter of one fiber before coupler fabrication being greater than the other, whereby wavelength selective coupling between one and the other fiber is obtained.

Abstract: Dual polarization microstrip array antennas for high efficiency power reception or transmission of electro-magnetic waves are described. The antennas are easy to manufacture, applicable over a wide range of frequencies and angles of incidence, and permit true conformal application and high power handling. The antenna, according to an embodiment, has an array of microstrip patch antenna elements, wave filters, matching stubs and rectifier terminals, all highly symmetrically arranged to each other on one side of a dielectric layer. A common ground plane is provided on the other side of the dielectric layer. Rectifiers are connected to the terminals to produce rectified outputs of each patch antenna element.