Abstract: A waveguide switch operable at microwave frequencies is formed of two waveguides of rectangular cross section with a longer wall and a shorter wall, the two waveguides sharing a common shorter wall. Two coupling windows are disposed within the common wall for coupling electromagnetic energy between the two waveguides, each coupling window introducing a 90.degree. phase shift. Each window couples one-half the power of an electromagnetic wave from a first of the guides to a second of the guides. The common wall is parallel to the electric field of the coupled wave, with each wave being a TE wave. A 90.degree. phase shift is introduced by each coupling with the result that utilization of both windows produces a summation of the two waves in the second of the waveguides and a cancellation of the two waves in the first of the waveguides.

Abstract: A process and apparatus for controlling the charging of pressurized gas-metal cells such as nickel-hydrogen cells, to prevent detrimental overcharging, wherein the time rate of change of a battery gas pressure index is monitored as a control parameter. When the time rate of change of the index falls below a preselected value, charging is discontinued. The cell gas pressure index can be gas pressure itself, or a quantity which is responsive to, and depends upon gas pressure, such as the deformation of a cell component.

Abstract: A receiver is disclosed for acquiring and tracking a data signal in a highly stressed environment. The receiver comprises first and second I.F. sections, a mixer for translation from the first I.F. frequency to the second I.F. frequency, a 3 KHz bandpass filter at the second I.F. frequency, signal translator for synchronous translation of the signal at the second I.F. frequency to baseband, a digitizer for complex sampling operation on the baseband signal, a microprocessor for processing the digital samples, and a numerically controlled oscillator coupled to the mixer and controlled by the microprocessor. The microprocessor formulates matched digital discrete Fourier Transform filters which drive frequency, phase and symbol lock loops at the symbol rate. Each of the loop filters is formed by symbol-rate recursive, first-order equations.

Abstract: A waveguide hybrid coupler is formed with a pair of waveguides of rectangular cross section and sharing a common sidewall. An aperture in the sidewall provides for the coupling of electromagnetic energy between a first of the waveguides and a second of the waveguides. An input terminal is located at an end of the first waveguide. A pair of stepped, multi-tiered abutments are disposed on the outer sidewalls of the waveguides opposite the coupling aperture. The dimensions of the abutment steps are selected to stagger-tune the frequency response of the coupler to achieve wideband operation.

Abstract: A process for preventing electrical capacity loss during storage of a pressurized nickel-hydrogen electrical storage cell. An electrical precharge is applied to the positive electrode of the cell, so that discharge of the cell is negative electrode limited. In one approach, the cell is charged, while sealed, to a state of charge corresponding to a first gas pressure, and then the hydrogen pressure is reduced to a lower value, preferably about atmospheric. In another approach, a current is passed through the cell while the cell is unsealed and maintained at atmospheric gas pressure, until the cell reaches the desired state of charge.

Abstract: Apparatus for use in gyroscopically ejecting a spacecraft supported in the open end of a spacecraft supporting cradle. The invention comprises a separable ejection restraint mechanism attached between the cradle and the spacecraft. The mechanism restrains the thrust force applied to the spacecraft for a predetermined time period in order to dissipate undetermined forces acting upon the spacecraft prior to the ejection thereof. The mechanism comprises a separable resilient portion and a releasable clamp portion coupled thereto. The resilient portion comprises a spring loaded anchor rod arrangement while the releasable clamp portion comprises a spring loaded split ball clamp arrangement. The invention also contemplates the use of a flexible carrier coupled between the spacecraft and the cradle. The invention acts as a tether connected between the cradle and spacecraft which acts to establish a determinant state of force on the cargo and eliminate unwanted ejection-related problems prior to cargo deployment.

Abstract: A system for surveying features of a planet includes a novel attitude determination subsystem. A satellite includes an earth imaging sensor (106). The sensor is alternately directed at the earth and a predetermined star field. The optical detections are converted to electronic signals by a sensor electronics module (332). The outputs of the sensor electronics module corresponding to the times when the sensor is directed toward earth are processed by a signal processor (336), the output of which is a data stream which permits image reconstruction by a ground station computer. The outputs of the sensor electronics module corresponding to the times when the sensor is directed toward the star field are directed through onboard star detection thresholding electronics. A programmable threshold device (342) selects detections of target stars within the star field. A star data buffer (344) stores these target star detections for transmission to earth at a convenient time.

Abstract: An overlapping frequency sweep system (10) includes a complex multiplier (15) located between two reflective array compressors (RACs 13 and 21). The complex multiplier compensates for the distortions due to both RACs by modifying the phase and amplitude of the sweep at an intermediate point in its dispersion. This permits precise calibration of the individual sweeps between the time when they are in the form of pulses and when successive sweeps overlap.A pulse source (11) provides a series of pulse inputs to the first RAC (13), the series having a predetermined period between successive pulses. The first RAC introduces differential delays as a function of frequency, the maximum differential delay introduced in a given sweep being equal to or less than the period of the pulse series. The remainder of the desired dispersion is applied by the second RAC (21). A limiter (23) provides a constant amplitude function of frequency input to the complex multiplier.

Abstract: A direction-finding interferometer (100) includes a novel autocalibration subsystem using bi-directional transmissions at a common frequency. The interferometer determines direction using a primary phase comparator (15) to assess the phase differences in signals transmitted by signal channels (13) from multiple antennas (11). The signal channels may include RF amplifiers (17), mixers (19) coupled to a local oscillator (23), IF amplifiers (21), and transmission lines.The autocalibration subsystem employs a frequency synthesizer (25) as a calibration signal source. The calibration signal path is directed between reversing switches (40) and couplers (33) in alternating directions via transmission lines (57 and 59). In either direction, the calibration is split so that part of the signals are coupled into the signal channels, and the remaining part is directed to a secondary phase comparator (131). The outputs of the primary and secondary comparators provide the data necessary for autocalibration.

Abstract: A frequency sweep system (10) operating in the radio frequency range includes a pulse source, a reflective array compresser (RAC) (13) and a complex multiplier (15). The RAC is designed to apply a time dispersion as a monotonic function of frequency to a pulse generated by the pulse source. Since RACs are difficult to manufacture precisely, the complex multiplier is included to compensate for the imperfections in the RAC. The complex multiplier is designed to multiply its analog input by a sequence of complex digital words, including a sign bit, so that the phase and amplitude of the analog signal can be calibrated as required. The sequence of digital words is determined by comparing the desired and actual phase dispersions of the frequency sweep system. The sequence so determined is stored in a read-only memory (ROM) (17). A timing generator (19) coordinates the firing of the pulse and the introduction of the sequence of digital words into the complex multiplier.

Abstract: A passive imaging system (400) includes a frequency scanning array (412) for receiving radiation emissions from a scene with a flat or known spectrum of emissions over the operating frequency of the array. Different beam directions are addressed by a spectrum analyzer (404). An image coordinate generator (410) may be used where necessary to normalize the image which may be stored or displayed by an appropriate device (406).In one embodiment, the array is planar so as to generate pencil beams. The planar array comprises parallel line-source antenna elements (402), with a common feed (414). The feed has a large "wrap-up" so that frequency-frequency scanning is employed.Alternatively, one-dimensional images can be effected with a single line-source frequency scanning antenna element. Also, one-dimensional frequency scanning may be supplemented by a different scanning approach for resolution orthogonal to that provided by the frequency scanning. In one embodiment, phase gradient scanning is employed.

Abstract: A phase shifter for microwave electromagnetic energy propagating through a waveguide has a composite structure of a series of capacitive phase shifting posts positioned within the waveguide diametrically across from a symmetrically tapered ridge. The series of posts introduce a nominal value of phase shift with an incremental value which increases with increasing frequency of the electromagnetic energy. The tapered ridge introduces a nominal value of phase shift plus an incremental value which decreases with increasing frequency of the electromagnetic energy. The rates of increase and decrease of the incremental values of phase shift cancel so as to provide a resultant phase shift which is substantially invariant with frequency.

Abstract: An analog radio frequency spectrum analyzer (10) includes a calibration section (30) for compensating distortions. The spectrum analyzer includes a first reflective array compressor or "RAC" (12), a frequency sweep section (20), and a second RAC (14). Frequency domain compensations introduced at the signal input by the calibration section compensate distortions in the time domain at the output of the spectrum analyzer. This system corrects, for example, nonlinearities in the second RAC. The calibration function is determined by a network analysis of the spectrum analyzer and is specific to the RAC included. The function is stored in a ROM or other memory as a sequence of complex digital words. An address generator (36) directs the words to a complex multiplier (32) so that each input symbol period is multiplied by the sequence. Each complex digital word corresponds to an amplitude and phase modulation of the incoming signal over a fraction of a symbol period.

Abstract: A switch (11) for a square coaxial network includes a lower housing (13), a rotor assembly (21), alternative transmission lines (19), and an upper housing (15) with a main transmission line (17). The rotor assembly includes a rotor (23) for selectively coupling the main transmission line to a selected alternative transmission line. The rotor is coadapted with each transmission line for resonant coupling therewith. A conductive shield (29) rotates with the rotor and isolates it from the unselected alternative transmission lines. A low-friction dielectric guide (25) helps provide proper spacing and coupling of the rotor and the square center conductor (35) of the selected alternative transmission line. A low-friction dielectric bushing (27) serves a similar function for the rotor and the center conductor of the main transmission line.

Abstract: A two-dimensional, long baseline (D) direction finding interferometer (12) is provided for obtaining unambiguous spatial position of an object. The interferometer comprises four antenna receiving means, (A1, A2, A3, A4) which are arranged in a two-dimensional, planar fashion. Three of the antenna means (A1, A2, A3) are positioned on two orthogonal axes (D, D.sub.2). The remaining antenna (A4) means is positioned on a third axis (D.sup.1) which is arranged asymmetrically and nonorthogonally to the orthogonal axes, whereby the unambiguous spatial position of the object is determined.

Abstract: An adaptive antenna 10 embodying the present invention includes an array of sensors 12. Each sensor 12 has associated therewith a main channel 14, a feedthrough path 16 and a feedback path 18. Correlators 20 coprocess signals in the feedthrough path 16 and the feedback path 18; the result is transformed according to an algorithm by a computer 22 which controls a weighting circuit 24. The weighting circuit 24 thus progressively modifies the signal in the main channel 14 to minimize interference with a desired signal. Placement of a limiter 26 along the feedback path 18 simplifies correlator design relative to adaptive antennas without such limiters and improves performance relative to adaptive antennas with limiters in the feedthrough path.

Abstract: An optical logic device wherein two light beams are launched into an optical nonlinear resonator, the phase shift characteristics of the resonator cavity being dependent on the intensities of the light beams traveling therethrough. The beams are launched in a manner such that each beam propagates in linearly independent modes whereby the relative phase of the beams does not affect the manner in which the light beams interact within said cavity.

Abstract: An ejection mechanism for imparting an ejection force to substantially constant locus of points on a payload ejected from a spacecraft is disclosed. The ejection mechanism includes a rod having a contact end for abutting contact with the locus of points. The rod is slideably mounted within a housing defining a first aperture from which the rod is driven toward the locus of points. Means are provided for driving the rod toward the payload to eject the payload, and means are provided for securing the housing to the spacecraft. The ejection mechanism also includes means for permitting the contact end of the rod to substantially maintain abutting contact with the locus of points as the rod is driven toward the locus and the payload is ejected from the spacecraft.

Abstract: A receiver is disclosed for acquiring and tracking a data signal in a highly stressed environment. The receiver comprises first and second I.F. sections, a mixer for translation from the first I.F. frequency to the second I.F. frequency, a 2 KHz bandpass filter at the second I.F. frequency, signal translator for synchronous translation of the signal at the second I.F. frequency to baseband, a digitizer for complex sampling operation on the baseband signal, a microprocessor for processing the digital samples, and a numerically controlled oscillator coupled to the mixer and controlled by the microprocessor. The microprocessor formulates matched digital discrete Fourier Transform filters which drive frequency, phase and symbol lock loops at the symbol rate. Each of the loop filters is formed by symbol-rate recursive, first-order equations.

Abstract: A switch (10) of the type comprising a rectangular arrangement of ports (21, 22, 23 and 24) includes a diagonally extending connector bar (35) disposed on one side of the rectangular arrangement opposite four laterally extending connector bars (31, 32, 33 and 34). The diagonally disposed connector bar is actuatable independently of the other bars. Electromagnetically driven rockers (79) or other means are provided to actuate the rods. In one realization of the switch, the ports are coaxial connectors for a microwave network. Each connector bar resides within a corresponding groove (51, 61) in a conductive housing and is independently actuatable. When actuated, a bar contacts the center conductors of two ports. The actuated bar cooperates with the walls of the containing groove to form an air-line microwave connection between the contacted ports. When the contained bar is unactuated, the groove becomes a waveguide-beyond-cutoff to isolate the respective ports.