Abstract: An isolation structure for high frequency integrated circuits is a conductive material disposed over a region of active gallium arsenide substrate. The conductive material over the active region creates a lossy RF path to reduce undesired coupling between adjacent conductors. In one case, two RF signal lines (1,2) terminated at the same via pad (3) have weaker coupling than in prior art via structures due to the lossy RF structure disposed on isolating fractional portions (10,11) of the via pad (3). The isolating fractional portion (10,11) are intermediate terminating fractional portions (8,9) of the via pad (3) to which the signal lines (1,2) are connected. In another case, two parallel bias lines (12,13) are disposed over an active layer region (6) increasing the RF loss between them and advantageously reducing the RF coupling. The reduced RF coupling improves RF isolation and permits increased miniaturization.

Abstract: A system for switching radio frequency signals from an input side (5, FIG. 1 ) to an output side (6) can be used to combine multiple input signals to form a single output and to distribute a single input signal to form multiple outputs. Gain correction amplifiers (20, 25) are employed to adjust the overall gain of a particular column and row of the switch matrix which minimizes the effect of variations in the gain of the amplified switching elements (30) which perform the switching function. Resistive matching units (70, FIG. 2) provide coupling to and from the amplified switching elements (30) without substantially changing the characteristic impedance of the input and output paths.

Abstract: An K-band amplifier circuit (10) with two samplers (12, 18) coupled to detectors (22, 26) that detect an input and an output RF signal level. These two reference signals are provided to a differential gain control circuit (24) which is coupled to one or more variable gain amplifier (VGA) (14) stages. The VGAs compensate for the gain of an entire chain of amplifiers (16). When the individual amplifier gains vary for any reason, (i.e., process, temperature effects or end of life degradation) the variation in gain causes higher or lower levels of detected output reference signals for a given RF input signal. The gain control circuit (24) drives the VGA (14) up or down as appropriate. By maintaining a constant offset in input and output reference control signals, the gain control circuit (24) drives the amplifier chain (16) to a constant gain.

Abstract: An antenna subsystem (120) which comprises an electronic scanning reflector antenna (400) is used for the formation of single and multiple beams. Reflecting surface (420) is covered with at least one dielectric layer (430) which is used to simultaneously and independently steer multiple beams. Electronic scanning reflector antenna (400) operates similar to a phased array antenna. ESRA (400) comprises a number of independent controllable reflecting surfaces (450) which are combined together in close proximity. Each one of the individual regions is covered by a dielectric layer, and the dielectric constant for each can be independently controlled. Electronic scanning reflector antennas (400, 600) are used in both space-based and terrestrial-based applications. Electronic scanning reflector antennas (400, 600) are used for both transmission and reception of electromagnetic signals.

Abstract: A dual quadrature branchline in-phase power combiner and power splitter provides a low cost and symmetrical structure for combining power from two signal ports (20, 30, FIG. 1) to an output signal port (10). When used as a power splitter, the structure accepts power from a signal port and divides the power equally and in-phase between the output signal ports (20, 30). The structure can be fabricated using microstrip, stripline, or similar technology such as suspended stripline. The structure is well matched over a large bandwidth and provides high isolation between the splitter output signal ports (20, 30).

Abstract: A user terminal (110) which comprises an electrically-controllable back-fed antenna (300, FIG. 3) is used for the formation of single and multiple beams. The electrically-controllable back-fed antenna comprises an RF power distribution/combination network (310), electrically-controllable phase-shifting elements (320), a control network (440, FIG. 4) and radiating/receiving elements (360). The control network is coupled to the electrically-controllable phase-shifting elements and is used for controlling the dielectric constant of dielectric material contained within the electrically-controllable phase-shifting elements. In a preferred embodiment, phase-shifting elements comprise waveguide sections containing at least one dielectric material, and the dielectric material includes a ferroelectric material, preferably comprising Barium Strontium Titanate (BST).

Abstract: A space-based communication system (30), includes a transmission terminal having a transmission antenna (42) and a power amplifier (40) to power the transmission antenna, the power amplifier to generate a power output sufficient to generate an RF signal through the transmission antenna (42), a receive terminal including a receive antenna (45) to receive the RF signal from the transmission terminal and a low noise amplifier (43) to amplify the RF signal channeled through the receive antenna, and a thermoelectric cooler (62) for cooling the low noise amplifier (43) to a predetermined temperature for increasing the sensitivity of the low noise amplifier to minimize the power output generated by the power amplifier required to generate the RF signal thereby minimizing the overall power requirements of the spaced-based communication system (30).

Abstract: An amplifier system (100) for transmitting wideband multicarrier communication signals in a satellite communication system uses wideband envelope elimination and restoration amplifiers (200). The system upconverts channelized IF signals to provide a wideband multicarrier RF output signal between 20 and 30 GHz having a bandwidth between 100 and 200 MHz.

Abstract: A method and apparatus for efficiently interconnecting a large number of high frequency high bandwidth signals includes two interface plates (100, 200), each having two substantially coplanar faces, a mating face (110, 210) and a non-mating face (120, 220). Each interface plate has waveguides (116, 216) disposed between the coplanar faces such that when the mating faces of the interface plates are brought together, a plurality of waveguide connections are made. An energy absorbing gasket (300) having a hole pattern matching the waveguide pattern is disposed between the mating faces of the interface plates so that reflections caused by misalignment and non-coplanarity of faces can be reduced.

Abstract: A harmonic generator (20) converts an input signal (24) at a fundamental frequency (28) into an output signal (32) at a harmonic frequency (34). A non-linear device (22) converts the input signal (24) into an intermediate signal (38) in which the harmonic frequency (34) has a maximized amplitude (40) determined by a conduction angle (26). A harmonic filter (68) produces a filtered signal (70) proportional to the amplitude (40) of the harmonic frequency (34) within the intermediate signal (38). A detector (80) produces a control signal (82) proportional to the amplitude of the filtered signal (70). A control circuit (84) produces a variable bias signal (50) for non-linear device (22), bias signal (50) being proportional to the amplitude of the control signal (82) and determining the conduction angle (26). An output filter (88) converts the intermediate signal (38) into an output signal (32) at the harmonic frequency (34).

Abstract: A MMIC power amplifier (100) uses MMIC FET cells (104, 112) and provides high gain at microwave and millimeter-wave frequencies. The power amplifier includes an input matching network (102), a first plurality of unit FET cells (104) for amplifying in-phase signals provided by the input matching network, a second plurality of unit FET cells (112), an interstage matching network (106) for combining output signals provided by the first plurality of unit FET cells, and providing in-phase signals to the second plurality of unit FET cells; and a combiner (113) for combining output signals of the second plurality of unit FET cells to provide an output signal. The FET cells are designed to be unconditionally stable without the use of an external series gate resistance. The FET cells are combined to provide total device periphery suitable for output power levels exceeding 0.8 watt at frequencies ranging from 19 to 23.5 GHz. The FET cells are designed using device scaling and device modeling techniques.

Abstract: A MMIC for providing a suspended transmission medium, comprising a MMIC chip, an upper ground plane overlying and spaced from critical circuitry and a lower ground plane underlying and spaced from the critical circuitry. The upper and lower ground planes are spaced from the critical circuitry at electrically similar distances. The portion of the MMIC chip that has the critical circuitry is suspended over a recess in the housing floor.

Abstract: A method and apparatus for efficient power amplification of a high dynamic range signal includes an envelope detector (220), a multi-range modulator (270), and a power amplifier (260). The multi-range modulator (270) efficiently amplifies the envelope of the input signal by selecting a power source as a function of the amplitude of the input signal. Multi-range modulator (200) produces a pulsewidth modulated signal with a duty cycle and an amplitude. When the amplitude of the input signal rises above a reference, the duty cycle and the amplitude are modified so as to keep the multi-range modulator in an operating region of high efficiency.

Abstract: A modular phased array antenna for the formation of simultaneous independently steerable multiple beams, the modular phased array antenna comprising a modular array including a plurality of sub-array modules combined together in close proximity, each one of the plurality of sub-array modules including a plurality of input modules, a layer of a plurality of radiating antenna elements, a plurality of stacked beamformers arranged in series and each connected to one of the plurality of input modules and to the plurality of radiating antenna elements in beam communication.

Abstract: An RF power detector (10) includes an RF detector circuit (12), a nonlinear feedback amplifier (14), a temperature compensation circuit (16) and a linear feedback amplifier circuit (18). The RF detector circuit converts an RF signal to a voltage representative of the RF signals power level. Nonlinear feedback amplifier (14) nonlinearly amplifies the voltage and compensates for the nonlinearities of the RF detector circuits detector elements. Temperature compensation element provides a temperature compensation signal to compensate for the temperature effects of the detector elements of RF detector circuit (12). The output signal of RF power detector (10) is a substantially linearly representation of the RF input signals power level. Nonlinear feedback amplifier (14) includes a nonlinear feedback circuit (30) with a nonlinear feedback element (32) in the feedback path of op-amp (42).

Abstract: An integrated microstrip (14) to suspended stripline (24) transition structure and method for fabricating the same provide a transition from microstrip (14) to suspended stripline (24) transmission line with minimal electrical discontinuity and insensitivity due to misalignment. A conductor (10) has a constant width, while gradually tapering voids (44,42) in ground planes (36, 38) provide a suspended stripline (24) transmission medium. The gradually tapering voids (44, 42) provide impedance transformation and minimize discontinuities during transition due to fabrication tolerances.

Abstract: An extremely broad band high power termination (10) for microwave and millimeter frequency amplifiers combines a standard resistive low frequency termination (15) with a broad band high frequency absorptive element (13) using an absorptive material such as Eccosorb. A mid-band matching network (14) is provided between the resistive termination (15) and the Eccosorb absorptive element (13). The Eccosorb absorbs the energy of the higher microwave frequencies while the resistor absorbs energy at low frequencies. Accordingly, a much higher power handling capability in a compact planer environment is achieved. This termination (10) is suitable use for use in K-band power amplifier combiners (30) that require high isolation and high power handling capability of the isolated ports (35).

Abstract: A method (140) for tuning millimeter-wave FET amplifiers (20) during manufacture, through the application (144) of a gate bias voltage (52) so as to tune the FET (22) of the amplifier (20) to match an input circuit (24), and through the application (146) of a drain bias voltage (74) so as to tune the FET (22) of the amplifier (20) to match an output circuit (26), then measuring (150) the frequency response of the amplifier (20). This tuning method (140) is repeated (152) until a predetermined frequency response has been achieved. Once achieved, the predetermined frequency response is realized (154) by permanently fixing the gate bias voltage (52) and the drain bias voltage (74) at the determined values. This iterative method (140) of tuning amplifiers (20) is then repeated for all amplifiers (20) to be tuned.

Abstract: A power amplifier (10) suitable for satellite cellular communication systems provides highly efficient linear amplification of noise-like RF signals that have multiple carriers spread over a large instantaneous bandwidth. The amount of distortion present in the output is detected (14, 16, 18) and a feedback signal is provided to control the bias point of the active devices. As drive levels increase, the increased harmonic distortion power detected causes the power amplifier bias to increase thus reducing distortion. The control circuit (20) continually re-biases the power amplifier (12) for maximum efficiency for a predetermined level of distortion. The control circuit (20) may be adjusted to maximize efficiency while maintaining an allowable distortion level over the entire dynamic range of the devices.

Abstract: A MMIC power amplifier (100) uses MMIC FET cells (104, 112) and provides high gain at microwave and millimeter-wave frequencies. The power amplifier includes an input matching network (102), a first plurality of unit FET cells (104) for amplifying in-phase signals provided by the input matching network, a second plurality of unit FET cells (112), an interstage matching network (106) for combining output signals provided by the first plurality of unit FET cells, and providing in-phase signals to the second plurality of unit FET cells; and a combiner (113) for combining output signals of the second plurality of unit FET cells to provide an output signal. The FET cells are designed to be unconditionally stable without the use of an external series gate resistance. The FET cells are combined to provide total device periphery suitable for output power levels exceeding 0.8 watt at frequencies ranging from 19 to 23.5 GHz. The FET cells are designed using device scaling and device modeling techniques.