Abstract: A low cost highly integrated method of fabricating a heat sink on the backside of a power semiconductor device maintains device performance, improves thermal transfer, and enables reliable planar connections without having to dice the wafer or package the discrete device-heat sink assembly. An etch stop layer is formed between the wafer and the frontside power devices to protect them during backside processing and to reduce the contact resistance between the device and its heat sink. The heat sinks are formed by thinning, patterning and then plating the wafer in such a manner that the devices can be released without dicing. The heat sinks are preferably oversized so that a vacuum tool can grasp the heat sink from above without damaging the device and then compression bond the heat sink onto a planar microstrip circuit assembly, which is designed and packaged to facilitate easy replacement of failed devices.

Abstract: Spacecraft attitude is efficiently controlled by utilizing spatial noise and temporal noise in the calculation of gains to a Kalman filter. Spatial noise is modeled in a dynamic fashion so as to provide optimal spatial noise attenuation.

Abstract: Methods for the design and fabrication of micro-electro-mechanical switches are disclosed. Two different switch designs with three different switch fabrication techniques are presented for a total of six switch structures. Each switch has a multiple-layer armature with a suspended biasing electrode and a conducting transmission line affixed to the structural layer of the armature. A conducting dimple is connected to the conducting line to provide a reliable region of contact for the switch. The switch is fabricated using silicon nitride as the armature structural layer and silicon dioxide as the sacrificial layer supporting the armature during fabrication. Hydrofluoric acid is used to remove the silicon dioxide layer with post-processing in a critical point dryer to increase yield.

Abstract: A motor current sensing circuit using a single sensing resistor in the motor current path to sense the current from the voltage source. The circuit includes an amplifier and a unity-gain inverter that translate the current across the sensing resistor into a voltage analog of the current in the motor. At any instant in time, the magnitude of the voltage across the sensing resistor is proportional to the magnitude of the motor current. During the forward portion of the duty cycle, a high-speed switch connects the sensor output to the amplified sensed bus current analog. During the reverse portion, the sensor output is connected to the inverted bus current analog. The average value of the sensor output is the voltage analog of the average value of the motor current.

Abstract: A swept frequency communication system includes a modulator that multiplies a frequency sweep signal with one or more underlying modulated communication signals to produce a swept frequency signal having a number of headerless tracks located directly adjacent one another in the swept frequency/time domain. A demodulator receives the swept frequency signal after that signal has been passed through a wireless channel, isolates a particular track of the received swept frequency signal to prevent a near/far problem, A/D converts the isolated track, resweeps the digitized isolated track, and then equalizes the isolated track using a blind channel equalizer to eliminate time-varying amplitude/phase impairments caused by transmission of that track through the wireless channel. The demodulator then removes the sweep signal from the equalized swept frequency track and decodes or demodulates the underlying modulated communication signal.

Abstract: A microwave filter has first and second subfilters. Each subfilter has at least one single mode resonator and a preset electrical response. The second subfilter is cascaded to the first subfilter by coupling one of the at least one single mode resonator of the first subfilter to one of the at least one single mode resonator of the second subfilter. The microwave filter has an overall transfer function dependent upon the selection of the first and second subfilters from a plurality of subfilters having different preset electrical responses.

Abstract: A system for simultaneously measuring strains in a test member includes spatial-position members which are coupled to different portions of the test member and first and second displacement sensors which are spaced apart by a sensor space and coupled to the spatial-position members. Linear and bending deformations of the test member are calculated as functions of the responses of the displacement sensors and of the sensor space.

Abstract: A simple joining process for members of passive microwave structures is described which reduces passive intermodulation. The process forms an aperture in a first member and forms a second member to have dimension which exceeds the aperture dimension by a dimension differential. The members are joined by initially causing them to have a temperature differential that is sufficient to permit the second member to be positioned across the aperture. The dimension differential is selected to generate mutually-induced radial stresses in the members, after the temperature differential is removed, which enhance the metal-to-metal contact between the members and, thereby, improve passive intermodulation (PIM) performance. Preferably, the dimension differential is selected to cause the second member to elastically buckle and exert a buckling stress against the first member. Additional interface structures are provided to resist operational axial forces, e.g., vibration, that tend to dislodge the members.

Abstract: A highly uniform, planar and high speed JHEMT-HBT MMIC is fabricated using a single growth process. A multi-layer structure including a composite emitter-channel layer, a base-gate layer and a collector layer is grown on a substrate. The composite emitter-channel layer includes a sub-emitter/channel layer that reduces the access resistance to the HBT's emitter and the JHEMT's channel, thereby improving the HBT's high frequency performance and increasing the JHEMT's current gain. The multi-layer structure is then patterned and metallized to form an HBT collector contact, planar HBT base and JHEMT gate contacts, and planar HBT emitter and JHEMT source and drain contacts.

Abstract: A telemetry system for receiving data from large arrays of sensors, in which the sensors are located in an unprotected environment, is implemented using fiber optic components. Laser sources, located in a protected environment, transmit light through the boundary separating the protected environment from the unprotected one. The light is then split into a number of beams and fed to electro-optical modulators, where it is modulated in response to electrical signals received from the sensors. The modulated light signals are then wavelength-division multiplexed and transmitted back through the environment boundary, where they are amplified, demultiplexed and converted to electrical signals. Multiplexing reduces the number of boundary penetrations, and the use of highly stable electro-optical modulators eliminates the need for signal conditioning electronics at each sensor.

Abstract: A method and system for detecting collision of transmitted signals in a random-access, multiple-path communication system utilizes a packet coding arrangement where a transmitting transceiver terminal assembles a plurality of packets into a coded transmit block. Each transmit block is coded with an error detection code, or assigned time slots, so that a routing controller will discard an entire transmit block if any of the packets are not properly decoded. Each transmit block further includes a self-addressed packet, wherein receipt of the self-addressed packet by the transmitting terminal indicates that no collision has occurred. Thus, the present invention does not require any additional circuitry or control of the routing controller, nor transmission of an acknowledgement signal in order to detect collision of transmitted signals.

Abstract: A power system includes at least two battery cell modules. Each battery cell module has a lithium-ion battery cell, and a battery cell controller operably connected to the lithium-ion battery to control the charging and discharging of the lithium-ion battery cell. A central charge/discharge controller is operably connected to each of the battery cell controllers, allowing the charging and discharging of each lithium-ion battery cell to be individually controlled.

Abstract: A solar power source has a solar power converter, and a solar concentrator positioned to reflect incident light toward the solar power converter. The solar concentrator includes a support having a texture pattern formed thereon, and a reflector surface on the support. The support includes a layer of plastic, and the reflector surface is a layer of a metal, such as aluminum, deposited on the layer of plastic. The texture is formed in the layer of plastic, and is visible on a free surface of the reflector. The texture pattern may be a set of parallel linear recesses.

Abstract: Spacecraft stationkeeping and momentum-dumping methods are facilitated by the use of selected diagonal pairs of thrusters which are positioned adjacent to nadir or antinadir spacecraft faces. The methods maintain an elliptical Sun-synchronous orbit, counter triaxiality forces and facilitate momentum-dumping of momentum and/or reaction wheels. They are particularly suited for inclined orbits.

Abstract: A control circuit for a power supply for at least one Traveling Wave Tube (TWT) that uses the cathode voltage as a reference point allowing independent, variable control of each TWT. The cathode current is varied by varying the anode voltage. Therefore, it is not necessary to operate the TWT below maximum power at full cathode current. The result is improved operating efficiency for the TWT. A single power supply is capable of powering several TWT's resulting in a significant weight and cost savings for space applications.

Abstract: An approach for connection of an antenna employs an antenna including at least one antenna contact; a swivel collar slidably coupleable with the antenna and including at least one collar contact; and an antenna coupler/connector insertable into the swivel collar. The approach may also be characterized as involving moving an antenna by sliding the antenna within a swivel collar, moving an antenna contact at an end of the antenna away from a swivel contact in the swivel collar; and inserting an antenna coupler/connector into the swivel collar including contacting the collar contact with a contact pad on the antenna coupler/connector.

Abstract: A reconfigurable filter system designed using micro-elecro-mechanical (MEM) switches is disclosed. The filter comprises a transmission line with one or more filter stubs coupled to the transmission line by MEM switches. The impedance of the filter system is altered by selectively opening and closing the MEM switches, which alters the filter characteristics of the filter system. Alternatively, the characteristics of the filter system are altered by using the MEM switches to selectively alter the length of filter stubs attached to the transmission line.

Abstract: A method of growing a p-type doped Group II-VI semiconductor film includes the steps of forming a lattice comprising a Group II material and a Group VI material wherein a cation-rich condition is established at a surface of the lattice. The method further includes the steps of generating an elemental Group V flux by evaporating an elemental Group V material and providing the elemental Group V flux to a Group VI sublattice of the lattice.

Abstract: A method and system for providing global variable data rate connectivity in a satellite-based communications network includes a plurality of communications satellites for transmitting and receiving signals in a plurality of coverage areas. User terminals transmit and receive signals to and from the satellites. A set of the user terminals located in one of the coverage areas and associated with one of the communications satellites has a variable bandwidth associated therewith. The variable bandwidth is determined based on the collective bandwidth requirements of each of the user terminals in the set. Each of the user terminals may request a change in their bandwidth requirement independent of the variable bandwidth associated with the collective set of the user terminals.

Abstract: A video image indexing system includes a method for identifying categories in compressed digital data for improved retrieval of video images. An encoder receives a frame and digitizes the image data while a sub-band coder codes each digitized frame at a plurality of transform levels to derive categorized data segments. Data segments are stored and then retrieved according to minimum entropy of Eigenvalues in a first transform level. Preferably, the compression is improved by creating a residual image of each frame by subtracting a predicted frame image from the actual frame image. This compression of data enhances the recreation of lossless video images at the receiver.