Abstract: A multiple quantum well (MQW) radiation sensor eliminates tunneling current from the photoactivated current that provides an indication of incident radiation, and yet preserves a substantial bias voltage across the superlattice, by fabricating an intermediate contact layer between the superlattice and a tunneling blocking layer. Using the intermediate contact layer to apply a bias voltage across the superlattice but not the blocking layer, the photoexcited current flow through the intermediate contact and blocking layers is taken as an indication of the incident radiation. The width of the intermediate contact layer and the barrier energy height of the blocking layer relative to that of the superlattice barrier layers are selected to enable a substantial photoexcited current flow across the blocking layer.

Abstract: A multiple quantum well (MQW) radiation sensor distinguishes radiation within a desired bandwidth, particularly long wavelength infrared radiation (LWIR), from background high intensity noise radiation that excites majority-minority charge carrier pairs. A minority charge carrier collector is provided at one end of the MQW, and the flow of minority charge carriers to the collector is sensed. The minority charge carrier flow provides an indication of the majority charge carrier flow that is attributable to the noise radiation rather than to radiation within the desired bandwidth, and can thus be used to provide a corrected indication of the desired bandwidth radiation.

Abstract: A microwave monolithic integrated circuit (MMIC) (40), includes a substrate (60), and an input bus (62), output bus (64), ground bus (66) and bias bus (68) formed as striplines of a four-line coplanar waveguide on the substrate (60) with the input bus (62) and output bus (64) disposed between the ground bus (66) and bias bus (68). A plurality of spatially distributed cascode amplifier units (43) are formed on the substrate (60), each including an input heterojunction bipolar transistor (HBT) (42) connected in a common-emitter configuration, and an output HBT (44) connected in a common-base configuration. The input HBT (42) has an emitter (E.sub.1) connected to the ground bus (66), a base (B.sub.1) connected to the input bus (62) and a collector (C.sub.1). The output HBT (44) has an emitter (E.sub.2) connected to the collector (C.sub.1) of the input HBT (42), a base (B.sub.2) connected to the bias bus (68) and a collector (C.sub.2) connected to the output bus (64).

Abstract: A multiple quantum well (MQW) superlattice photodetector, is surmounted by a slab of transparent material having an angled surface that extends upward and away from the photodetector, such that incident radiation which is initially normal to the superlattice undergoes total internal reflection at the angled surface and is reflected onto the detector at a substantially non-normal angle. This off-normal angle allows the radiation to be partially absorbed by the detector. A reflection grating is preferably formed on the opposite side of the detector to redirect received radiation back through the MQW superlattice at an altered angle, such that remaining radiation can be absorbed by the detector during the second pass. The detector is formed upon a substrate, with the slab, substrate and quantum wells all preferably formed from the same type of material. Multiple detectors may be formed in an array upon a common substrate, with a slab providing a common reflective surface for the overall array.

Abstract: The base-collector capacitance in a heterojunction bipolar transistor (HBT) (50) is reduced, thereby providing increased cutoff frequency and power gain, by eliminating a portion of a collector contact layer (54) which normally underlies a base electrode (66). A similar effect may be produced by forming the collector contact layer (54) such that it initially extends into the area (54c) under the base electrode (66), and subsequently rendering the collector contact layer (54) in this area (54c) semiinsulative by proton bombardment. A ballast resistor layer (70) is formed between an emitter layer (62) and an overlying emitter electrode (68) to prevent thermal runaway and hot spot formation. A plurality of the HBTs (50) may be arranged in a distributed amplifier configuration (80) including contact electrode bus lines (84,88) having a geometry designed to provide high thermal efficiency, and input and output circuit matching characteristics.

Abstract: A multiple quantum well superlattice radiation detector is compositionally graded to establish an internal electric field within the superlattice that allows the device to operate with a reduced or zero externally applied bias voltage. The compositional grading can be implemented by grading the doping levels of successive quantum wells or the relative proportions of elements in successive barrier layers of the superlattice, or by a combination of the two. If a tunneling current blocking layer is employed, it can also be compositionally graded to inhibit a substantial increase in the blocking layer's barrier energy level near a charge carrier collector on the other side of the blocking layer from the superlattice. The charge carrier collector can itself be provided with a graded dopant concentration near the blocking layer to inhibit reverse bias voltage breakdown in the blocking layer.

Abstract: A digital phase shift apparatus having a pair of single gate FETs which are connected in a common source configuration. Transmission line segments which respectively connect the sources and drains of the FET pair, provides a phase shift to an applied RF signal. The operating FET provides signal gain as well as switch the signal path length.

Abstract: A microwave radar transceiver assembly (30) includes a monolithic microwave integrated circuit (MMIC) chip (58) having a coplanar waveguide transmssion lines (100, 102, 104) formed on the same surface (58a) as the electronic elements thereof. Coplanar waveguide transmission lines (68, 70, 72) are also formed on a surface (62a) of a substrate (62). The transceiver chip (58), in addition to other chips (56, 60), are mounted on the substrate (62) in a flip-chip arrangement, with the respective surfaces (58a, 62a) on which the transmission lines (100, 102, 104; 68, 70, 72) are formed facing each other.

Abstract: A coplanar waveguide directional coupler (116,134) may be formed on a surface (102a,106a) of a substrate (102) and/or a microwave monolithic integrated circuit (MMIC) chip (106), with the MMIC chip (106) being flip-chip mounted on the substrate (102). The directional coupler (116,134) includes an input port (114,136), a coupled port (126,154), a direct port (122,152) and an isolation port (1118,150) formed on the surface (102a,106a). At least two parallel first striplines (24,26) are formed on the surface (102a,106a), having first ends connected to the input port (114,136) and second ends connected to the direct port (122,152). At least two parallel second striplines (36,38) are formed on the surface (102a,106a), having first ends connected to the coupled port (126,154) and second ends connected to the isolation port (118,150). The second striplines (36,38) are interdigitated with the first striplines (24,26) to provide tight signal coupling therebetween.

Abstract: A coplanar waveguide based microwave monolithic integrated circuit (MMIC) oscillator chip (14) having an active oscillator element (16) and a resonant capacitor (18) formed thereon is flip-chip mounted on a dielectric substrate (12). A resonant inductor (22) is formed on the substrate (12) and interconnected with the resonant capacitor (18) to form a high Q-factor resonant circuit for the oscillator (10). The resonant inductor (22) includes a shorted coplanar waveguide section (24) consisting of first and second ground strips (24b,24c), and a conductor strip (24a) extending between the first and second ground strips (24b,24c) in parallel relation thereto and being separated therefrom by first and second spaces (26a,26b) respectively. A shorting strip (24d) electrically interconnects adjacent ends of the conductor strip (24a) and first and second ground strips (24b,24c) respectively.

Abstract: A multiquantum well superlattice photodetector for detecting long wavelength infrared radiation in which dark current is reduced by a blocking layer. The tunneling component of the dark current in a multiquantum well photodetector is substantially eliminated by placing a blocking layer at one end of the superlattice. The blocking layer has a potential energy barrier having a height at the same level of the barrier layers of the superlattice. The thickness of the blocking layer is substantially greater than the barrier layers of the superlattice to prevent charge carriers which tunnel through the superlattice from reaching the ohmic contact.

Abstract: Three active FET baluns, using resonant, reactive and resistive/reactive compensation are disclosed suitable for monolithic implementation. A single balanced mixer configuration including a resistive/reactive active FET balun coupled with a pair of single ended FET mixers in a push pull configuration is disclosed which is also suitable for monolithic implementation.

Abstract: A multiple quantum well photodetector structure has superlattice which absorbs radiation polarized non-parallel to the superlattice during a first pass. Non-absorbed radiation polarized parallel to the superlattice is reflected back into the superlattice at a cross-angle to its incident angle, with its polarization shifted to a substantially non-parallel angle to the superlattice. At least part of this radiation is absorbed during its second pass through the superlattice, thereby increasing the efficiency of the device. An optical back grating is used to perform the cross-angle reflection, and a front grating may also be used to shift an incoming beam which is initially normal to the superlattice to an angle at which part of the beam is absorbed. The front grating is at a cross-angle to the back grating to enable a cross-angular shift by the back grating.

Abstract: A field effect transistor FMCW radar transceiver for short-range target detection, employs a varactor-tuned, gallium arsenide field effect transistor, voltage-controlled oscillator in the dual role of the transmitter signal source and the local oscillator. The radar transceiver is capable of operating at low IF frequencies for short range, which can be less than 30 feet, target detection.

Abstract: In a radar system, an RF signal is transmitted at a frequency modulated by a sawtooth signal. The transmitted RF signal is mixed with the transmitted signal reflected from an object. The resulting IF signal is analyzed into a Fourier series having a DC coefficient and harmonic frequency coefficients. The range to the object is determined from the harmonic frequency coefficients in multiples of the range resolution determined by the RF bandwidth of the system when the DC coefficient is less than each of the harmonic frequency coefficients. The range to the object is determined to be within 1/2 the range resolution determined by the RF bandwidth when the DC coefficient is greater than each of the harmonic frequency coefficients.

Abstract: A beam lead diode configuration is described, employing a planar proton bombarded conversion region and a low-permittivity dielectric separator. The diode enjoys the mechanical ruggedness of the conventional planar diodes and the electrical performance of conventional mesa-type diodes. The diode structure results in the absence of N-type mesa structures on the substrate, allowing fabrication by relatively low-cost, high-yield photolithographic processes.

Abstract: A radar transceiver is disclosed which operates with circularly polarized waveforms. A single circularly polarized antenna is used to transmit and receive circularly polarized waveforms. A 3-dB directional coupler splits the signal to be transmitted into two signals 90.degree. out-of-phase for transmission by the antenna and also combines the horizontal and vertical components of any return signal.

Abstract: A double drift IMPATT diode is formed from two semiconductors having different band gaps and carrier mobilities. The avalanche portion of the diode is created in the semiconductor having the lower band gap. The electron drift portion is created in the semiconductor having the higher electron mobility and the hole drift portion is created in the semiconductor having the higher hole mobility. This decreases the voltage required across the avalanche portion, decreases the series resistance, and thus increases the efficiency of the diode.