Abstract: A high frequency coax via structure is configured with a stripped semi-rigid cable (no shield), and an inductive compensation loop to mitigate transition discontinuity between that via structure's center conductor and the pad to which the center conductor is connected. The performance of top-to-bottom microwave transitions at high frequencies (e.g., 1 to 12 GHz) for such boards is enhanced. A non-metallized via hole embodiment that is configured with surrounding ground vias provides a greater degree of compensation for connection pads associated with greater capacitance (such as those coupled to a component).

Abstract: A compact antenna includes a disk-type radiating element normal to a ground plane section. Each face of the radiating element may have a third-dimensional characteristic (e.g., a convex outer surface.) Dielectric material may be positioned on the ground plane forward of each face of the radiating element. In other configurations, the third-dimensional characteristic and dielectric material features may be used separately in antennas arranged to provide omnidirectional performance over a wide frequency bandwidth. An input/output port may be provided by a coaxial-type connector coupled to the radiating element.

Abstract: A high-speed serial interface for focal plane arrays (FPAs), such as microbolometer and cooled FPAs, is disclosed. The interface uses a serial low-voltage differential signal that is substantially unsusceptible to digital crosstalk and EMI, and provides power dissipation that is signal-independent.

Abstract: A high frequency coax transmission line structure is configured with a stripped semi-rigid cable (no shield). The stripped cable is inserted lengthwise into a metallized grounded slot formed in a printed wiring board. The dielectric barrel of the stripped cable contacts each of the elongated side and bottom walls of the slot. An exposed portion of center conductor at each end of the cable lays tangent on a corresponding one of connection points (at each end of the slot). The structure reduces loss for long transmission line lengths, and fixes the mounting depth and routing for a consistent transition. Inductive compensation can be provided at the connections point at each end of the slot to mitigate transition discontinuity.

Abstract: A multiuser detector system with correlation based pruning including a parameter estimation module adapted to receive complex signals, and to produce estimated signature waveforms for each of K co-channel interfering signals. Pre-processing the estimated signature waveforms using an S-matrix module and producing a more valid set of hypotheses, wherein the S-matrix module uses apriori knowledge of an unnormalized cross correlation matrix, and processing the more valid set of hypotheses for pruning with an M-algorithm a multiuser detector module. An improvement to the M-algorithm in which the interference structure based on the signal correlation matrix used during the optimization process aids in selecting a better subset of hypotheses to test.

Abstract: A method of producing an antenna coupler for placement on an antenna under test (AUT) having an aperture. This method includes the steps of constructing a probe from a section of RF hard-line stock having a center conductor and an outer conductor. The outer conductor is removed to expose a portion of the center conductor having a length equal to or less than ¼ wavelength of the AUT. The probe is embedded within a fiberglass shell and has an exposed RF connector for connection to equipment for performing tests on the AUT. The probe is then positioned across the aperture of the Antenna Under Test (AUT).

Abstract: An algorithm is provided for a frequency domain reflectometer which takes into account both attenuation per unit length of transmission line and phase shift per unit length of transmission line in a modified Inverse Fourier Transform that converts a frequency domain complex reflection coefficient into a more accurate time domain reflection coefficient so that the distance to a fault can be readily determined.

Abstract: A directly pumped, un-sensitized, holmium, quasi-two level fiber laser is disclosed that is doped with Holmium active ions between 0.1 and 2.0 percent by atomic weight. This yields greater energy efficiency from the laser because up-conversion losses are minimized, mismatches created by sensitizer ions are eliminated by having no sensitizer ions, and thermal loading of the fiber medium of the laser is thereby reduced. In addition, the pump ratio of the fiber laser is 0.9 which yields a very low quantum defect. The low doping percentage of holmium active ions also eliminates any absorption of its own energy because the power of the diode pumping source is sufficient to cause the laser to reach transparency.

Abstract: Techniques that enable the transitioning of high frequency signals on a printed wiring board processed in accordance with industry standards (such as the IPC specifications) are disclosed. One embodiment provides a high frequency via structure for a printed wiring board, where the via structure includes a via pad configured in accordance with IPC standards. A printed microwave transmission line having an inductive section is connected to the via pad, wherein the inductive section has dimensions to compensate for transition discontinuity.

Abstract: A collapsible discone antenna is provided with an ultra wide band width by providing a collapsible conical skeleton cone, with the rods of the skeleton being provided with meander lines so as to effectively reduce the overall dimensions of the antenna by a factor of 2, with the antenna rods being electrically interconnected at their distal ends so as to eliminate performance degradation due to varying ground conductivities. A specialized feed configuration is used in one embodiment to feed multiple antennas stacked above a low band disc through the utilization of one or more coaxial lines which are wrapped around a ferrite toroid so that they may be passed up through the low-band disc without detuning the low band discone antenna. The use of the toroid inductor between the low-band cone and the low-band disc further reduces the low frequency cutoff of the antenna by markedly decreasing the VSWR at frequencies as low as 20 megahertz.

Abstract: A filter wherein the poles and zeroes are programmable in a high speed control loop to form a particular desired filter profile. The control loop retrains the filter's poles and zeroes during the “off” time between the reception or transmission time slots. Desired pole and zero frequencies are injected and peak values are stored in sample and hold circuits. This eliminates variations from voltage supplies, component tolerance, temperature, aging, etc.

Abstract: A method and apparatus is provided for correcting the phase difference estimate derived from a two-tone CW radar to correct velocity-induced range estimate phase errors by offsetting the phase difference estimate with a phase correction equal to either of the Doppler frequencies associated with returns from an object multiplied by the time interval between the samplings of the returned waveforms. The correction effectively eliminates the velocity-induced slippage between the phases of the retuned waveforms so that a comparison between the phases of the waveforms can be made to reduce or substantially eliminate range estimate bias.

Abstract: An amplifier circuit controls the output current through an inductive load. A signal is amplified by one or more op amps, and sourced into a back to back coupling of an NPN transistor and a PNP transistor. In a positive circuit segment, current is sourced to an inductive load, and in a negative segment, current is sunk from the inductive load. The current at the output of the inductive load flows through a resistor, and the resultant voltage drop is negatively fed back to the op amp.

Abstract: A robust, easily deployable, covert, passive intrusion detection system uses one or more E-field sensors to detect the presence of a moving individual and to provide an indication of the presence of the individual adjacent the sensor based on E-field distortion produced by the individual. Single-ended and differential E-field sensors with noise canceling and a guarding circuit provide sufficient sensitivity, with filtering from 0.5 Hz to 8.0 Hz selecting only human intruders. Either visible or invisible flashing light sources at the sensor indicate the presence of a moving individual at the sensor, thus to provide intruder location without the necessity of providing a geolocation system.

Abstract: In one embodiment, a method that includes creating a filter structure using a parameter of a periodic pulse train, the filter structure having a plurality of time slots, each time slot being associated with a memory value; receiving a pulse at a time; incrementing the memory value associated with the time slot corresponding to the time the pulse was received; filtering the pulse if the memory value exceeds a threshold; and transmitting the pulse to a processor if the memory value does not exceed the threshold. In another embodiment, an apparatus that includes an input filter; a pulse detection circuit coupled to the input filter; a periodic pulse filter coupled to the pulse detection circuit; and a pulse queuing and transmission circuit coupled to the periodic pulse filter.

Abstract: Algorithmic approaches that can be implemented in software/firmware/hardware that filters out stable PRI patterns detected within a system that is prosecuting against radar based transmissions are disclosed. The algorithms allow downstream computing assets to concentrate their limited resources on the more complex emitter PRI pattern types. Thus, a portion (e.g., stable signals) of the pulse deinterleave and PRI identification problem is solved without requiring the more computationally expensive processing. The disclosed algorithms can be employed, for example, in electronic support measures (ESM) systems, electronic intelligence (ELINT) systems, and/or electronic countermeasures (ECM) systems. The algorithms employ linear detection, linear regression, or a combination of linear detection and linear regression, thereby providing a “dual voting” scheme that decreases the occurrence of false positives.

Abstract: Described techniques extend (e.g., by a factor of 2) the dynamic range of voltage swing for amplifiers and other integrated circuits (e.g., buffers) that are fabricated using lower voltage rated semiconductor processes. Such processes include, for instance, thin gate oxide MOS, and other semiconductor processes that provide desirable features that are typically not associated with high voltage processes, such as increased radiation hardness, higher speed logic, and compactness. Thus, relatively large dynamic range is enabled for integrated circuits fabricated using feature-rich lower voltage rated semiconductor processes.

Abstract: The invention provides a method and apparatus for correcting for gain changes in detectors in a guided vehicle. In one version of the invention, an on board light source is used to generate a reference set of detector gains, which are stored in computer memory. The on board light source is then pulsed at subsequent times and the signals generated by the detectors are compared to the reference set of detector gains to determine whether any gains have changed.

Abstract: A reconfigurable digital processing system for space includes the utilization of field programmable gate arrays utilizing a hardware centric approach to reconfigure software processors in a space vehicle through the reprogramming of multiple FPGAs such that one obtains a power/performance characteristic for signal processing tasks that cannot be achieved simply through the use of off-the-shelf processors. In one embodiment, for damaged or otherwise inoperable signal processors located on a spacecraft, the remaining processors which are undamaged can be reconfigured through changing the machine language and binary to the field programmable gate arrays to change the core processor while at the same time maintaining undamaged components so that the signal processing functions can be restored utilizing a RAM-based FPGA as a signal processor.

Abstract: Methods and apparatuses for a low EMI power supply. The power supply may include a control circuit, a power switch connected to the control circuit, an anti-parallel diode connected to the power switch, an inductor coupled to the anti-parallel diode, an output diode coupled to the inductor, and an output capacitor connected to the output diode. The power supply may include a series diode and no anti-parallel diode. The power supply provides a controllable and variable high voltage power supply from a small number of devices while, at the same time, producing low EMI. Power conversion is achieved at high efficiencies due to the recycling of energy in parasitic capacitance. Due to its low EMI, the power supply is particularly well suited for driving electronic devices such as avalanche photodiodes.