Abstract:
Techniques for generating terahertz (THz) radiation are provided in which each nonlinear crystal in an array of such crystals is coupled to one or more corresponding waveguides such that any THz radiation generated in any single crystal is coupled into that crystal's THz waveguide structure. After the THz radiation is generated in the crystals and coupled into the waveguides, the individual THz signals may be coherently combined to form a single THz signal (non-coherent configurations are provided as well). Crystal-waveguide arrays embodying the techniques can be used to implement efficient, robust, and compact THz sources suitable for applications such as security screening, medical imaging, quality control and process monitoring in manufacturing operations, and package and container inspection.
Abstract:
Wireless medium access in a communication network having a number of terminals is controlled by defining protocol message units for transmission by a given terminal which units correspond to operational states of at least one of the terminal and the medium. A number of time slots are allocated for transmission of packets from each terminal, and a number of contention opportunities are defined at the beginning of each time slot. Priority and backoff mechanisms are defined and applied at each terminal during the contention opportunities in the slots. Packets are then transmitted by the terminal within the slots while (1) minimizing the occurrence of empty slots at times when packets are available for transmission, and (2) minimizing the number of slots during which two or more packets are detected on the medium simultaneously at the terminal.
Abstract:
A write circuit for providing distinctive write currents to a chalcogenide memory cell is disclosed. The write circuit includes a current amplitude trim module, a current amplification and distribution module, and a write current shaping module. The current amplitude trim module provides a well-compensated current across a predetermined range of temperatures, voltage supplies and process corners intended for programming a chalcogenide memory cell. The current amplification and distribution module amplifies the well-compensated current in order to meet a programming requirement of the chalcogenide memory cell. The write current shaping module supplies an appropriate amount of write "0" current or write "1" current, based on the amplified current, to program the chalcogenide memory cell accordingly.
Abstract:
A process and system for enhancing connectivity among nodes of a wireless communications network by adapting to changes in the network topology. Nodes of the network are configured to operate according to either (i) an ad hoc protocol wherein a given node assumes a role of a mesh node capable of connecting with other like-configured nodes, or (ii) a point-to-multipoint protocol wherein the given node assumes a role of a either base station, or a subscriber station being served by another node which is assuming the role of a base station. A determination is made as to whether each node should operate according to the ad hoc protocol or the point-to-multipoint protocol, in order to maintain an optimum state of connectivity among all nodes of the network. The determined operating protocol is then implemented for each node.
Abstract:
A single event upset (SEU) hardened memory cell to be utilized in static random access memories is disclosed. The SEU hardened memory cell includes a first inverter and a second inverter connected to each other in a cross-coupled manner. The SEU hardened memory cell also includes a first resistor, a second resistor and a capacitor. The first resistor is connected between the source of a first transistor and the drain of a second transistor within the first inverter. The second resistor is connected between the source of a first transistor and the drain of a second transistor within the second inverter.
Abstract:
A post-supported bolometer pixel and a process for manufacturing it comprising the steps of depositing a sacrificial layer over a substrate with readout integrated circuit pads that connect to the integrated circuit; forming vias through the sacrificial layer to the metal pads connecting to the readout integrated circuit; filling the vias with metal and polishing said metal to the surface of the sacrificial layer; forming microbolometer pixel layers over the filled vias and sacrificial layer; and removing the sacrificial layer to leave a post-supported pixel.
Abstract:
A wideband, e.g., 550 nm to 940 nm, apochromatic lens system for use with an external aperture stop, includes first, second, and third optical groups having, in order, positive, negative, and positive powers. The first group includes four optical elements having, in order, negative, positive, negative, and positive powers. The second group includes one element of negative power; and the third group includes two elements each having positive power. In another embodiment for use with an internal stop, the system includes first, second, and third optical groups having, in order, positive, positive, and negative powers. The first group includes four optical elements having, in order, positive, negative, positive, and negative powers. The second group includes one element of positive power, and the third group includes one element of negative power. In either embodiment, all of the optical elements are formed from not more than three different types of glass material.
Abstract:
A bipolar pulse generator includes two, two-conductor transmission lines coupled together with a load positioned between the two transmission lines. Each conductor of a transmission line we define as a segment. Two segments of one transmission line are charged and switchably coupled to two segments of the other transmission line to produce a bipolar pulse on the matched load. This bipolar pulse generator may be implemented in a flat or a folded design. The generator may include two transmission line structures coupled together with a load positioned between each transmission line structures. The first transmission line structure may include a stepped transmission line and an embedded transmission line segment. A switch may be coupled between the embedded transmission line segment and another segment of the transmission line structure. During operation, the first transmission line structure may be charged to a potential with the switch in the open position and, when the switch is closed, the charge on the first transmission line structure together with the second transmission line structure generates a bipolar pulse on the matched load.
Abstract:
A flat panel antenna used at a wall in a through-the-wall CW radar application is spaced from the wall by a half wavelength to eliminate the effects of energy reflected by the wall back to the antenna. In one embodiment, a ½-wavelength dielectric absorbing material insert is placed adjacent the flat panel antenna, which allows the flat panel antenna to be pressed against the wall for antenna stabilization, with the index of refraction of the material desirably being 3.
Abstract:
Antennas (50) for RFID tags are made to exhibit circular polarization to give the tag an omnidirectional charcteristic. The antennas are crossed dipoles (52,54) with respective feed points (56,58). The signal source (60) is coupled to a splitter (62) having output leads (64) directly coupled to the feed point (56) of dipole (52). The other output leads (66) from splitter (62) are coupled to a delay line (68) with the delayed output coupled to a feed point (58) of dipole (54).