Abstract: An interface module for an electronic system that permits signals to pass between a high frequency main circuit board area such as used for central processing units, memories, or other relatively high clock rate components and a low frequency circuit area such as used for standard peripheral circuit modules used for disk drives, video interfaces and the like. The interconnect module is positioned near an opening in a sheet metal bulkhead used as an electromagnetic interference (EMI) barrier around the main circuit area. The interface module uses a connector that is surrounded by one or more conductive shields that contain metal fingers on inboard and outboard sides to provide a ground connection between the interface module and the EMI barrier.

Abstract: A wireless communication system basestation making use of a wideband, multichannel digital transceiver having incorporated therein a time division multiple-access (TDM) bus for providing digital samples of a plurality of wireless communication channels, wherein the time slot duration and frame rate of the TDM bus may be reconfigured. The invention allows various air interface standards, even those having different channel bandwidths, to be serviced by the same basestation, without having to install additional or different equipment, and by automatically redistributing signal processing resources, eliminating the need to reconfigure the basestation when different types of wireless signaling must be accommodated.

Abstract: A technique for extending the instantaneous dynamic range available in a wideband digital basestation for use in a wireless communication network. The basestation processes the bandwidth allocated to it in two or more sub-bands. The sub-bands are each processed by a digital tuner section consisting of an amplifier, analog-to-digital (A/D) converter, and digital filter bank. The digital filter bank may make use of multirate digital signal recovery techniques for efficient implementation. In operation, a received signal strength indication (RSSI) is first determined for each subscriber unit requesting access to the basestation. A channel assignment controller then assigns a transmit frequency to the subscriber unit depending upon this RSSI. In particular, subscriber units exhibiting a relatively stronger RSSI are to transmit on a frequency assigned to a first digital tuner section, while subscriber units having a relatively weak RSSI are assigned to a second digital tuner section.

Abstract: A technique which enables the use of a low cost non-linear power amplifier to generate a wideband composite signal, such as in cellular mobile telephones (CMTs), personal communication systems (PCSs), and other multi-channel wireless system. A constant envelope signal is generated from a wideband composite signal comprised of a combination of many narrowband modulated signals. The technique involves adding one or more out-of-band artifact signals that accurately offset the amplitude variations of the wideband composite signal. The constant envelope signal is then fed to a high power amplifier, and, prior to radio transmission the amplified signal is filtered to remove the out-of-band artifact signals. As a result, only the desired composite signal having any required envelope variations is provided to the antenna, while at the same time, only a constant envelope signal is fed through the power amplifier.

Abstract: A novel radio receiver capable of simultaneously and instantaneously determining the frequency and azimuthal and elevational position of many radio signal sources is disclosed. The invention makes use of an antenna array and associated beamforming networks capable of producing an omnidirectional reference signal, and a directional signal in which amplitude depends upon the relative elevational position of the radio frequency source and complex phase depends upon the relative azimuthal position of a radio frequency source.The use of a two-dimensional compressive receiver in one embodiment provides a way for instantaneously and reliably producing the Fourier transform of these signals, allowing accurate and continuous measurement of phase and amplitude difference. The antenna geometries disclosed additionally provide such signals for a wide input bandwidth.

Abstract: A power supply is provided with a predetermined nonlinear temperature coefficient for float charging sealed lead-acid batteries and providing power to a load. A temperature compensation network in the power supply provides the predetermined nonlinear temperature coefficient by using a linear temperature coefficient element (forward biased silicon diode) and a nonlinear temperature coefficient element (thermistor) in combination. Additionally, an over-voltage protection circuit, to disable the power supply should the output voltage exceed a predetermined value, is disclosed having a second temperature compensation network to compensate for the output voltage variation with temperature of the power supply.

Abstract: An RF power amplifier for delivering power to a load including a first quadrature hybrid coupler driving two class C amplifiers operating with high input compression, a second quadrature hybrid coupler coupled to the outputs of the amplifiers, an attenuator, and a phase shifter. An impedance mismatch by the load causes phase-pulling of the amplifiers which reduces output to the load. This is compensated for by feeding an error signal, indicating the magnitude and phase of the phase-pulling of the two amplifiers, from the second quadrature hybrid coupler through the attenuator and the phase shifter back to the first quadrature hybrid coupler. The attenuated and phase shifted error signal adds to or is subtracted from the input signals to the two amplifiers. Therefore, one of the two amplifiers is driven with more signal and the other amplifier is driven with less signal to phase-push the two amplifiers to compensate for the phase-pulling to thereby increase the output to the load.

Abstract: A precision microwave delay line fabricated using stripline techniques, but having features of a coaxial transmission line. The delay line is assembled from three pieces: a center board, an upper housing, and a lower housing. The center board is a nonconductive substrate with a stripline conductor. The stripline conductor defines a transmission path. The housings are made of conductive material. A channel is formed on the inner surface of each of the housings. The channels are arranged such that when the center board is sandwiched between the housings, the transmission path is contained within a uniform cross-section cavity formed by the channels. The housings are electrically connected to each other through the center board with plated-through holes at locations along the sides of the transmission path.

Abstract: A phase-angle circuit (24) processes the outputs of an antenna array (12) to apply to a compressive receiver (20) an ensemble of signals having components whose spatial frequencies are proportional to the bearing angle of the electromagnetic plane waves that give rise to them. A signal whose phase angle is equal to twice the bearing angle is generated by interconnecting the antenna elements as two quadrupoles offset by 45.degree.. The output of one of the quadrupoles is shifted in phase by 90.degree. and added to the output of the other quadrupole to generate the desired signal, which is applied as an input to the compressive receiver. Other inputs to the compressive receiver are generated in similar ways. The position of the compressive-receiver output port (22) at which a maximum occurs indicates the bearing angle of the electromagnetic plane wave that gave rise to the maximum.

Abstract: A circular frequency-independent antenna array (10) includes a plurality of radially extending log-periodic subarrays (12, 14, 16, 18, 20, and 22) of slot radiators (26) provided in a ground-plane conductor (28). Associated with each slot is a cavity (34) into which the slot opens. A traveling-wave element in the form of a wire (30) cooperates with a ground-plane conductor (28) in which the slots are provided to support propagation of an electromagnetic signal. The signal is radiated upon encountering a slot that resonates at a frequency near that of the signal, and the depths of the cavities are adjusted so that the phase relationships between the radiation from the slots and the signal propagated along the traveling-wave element results in an antenna pattern that launches radiation in a direction away from the center of the array. Direction-finding errors are reduced because interference between the several subarrays is kept to a minimum.

Abstract: Apparatus for sorting two input numbers including a memory that iteratively receives a digit from both of the numbers and transmits output signals corresponding to the input digits, the digits of the larger number being transmitted on one output line and the digits of the smaller number being transmitted onto another output line. The apparatus includes a memory that receives, as address signals, the state signal and signals corresponding to the input digits. The state signal determines the output lines onto which the next pair of input digits are to be transmitted.

Abstract: A new method and apparatus for generating an analog output signal as a function of a digital input in the form of digital words over a specified range. The range is divided into a plurality of intervals, and the function is approximated by a linear segment in each interval. Each linear segment is defined by a step value, which is the value of the linear segment at the beginning the interval, and a slope value, which is the slope of the linear segment in the interval. The function is then approximated for any desired digital word in the range by determining the step and slope values for the interval into which the digital input signal falls, determining an incremental value by multiplying the slope value by the difference between the digital input signal and the value of the digital input signal at the beginning of the interval, and adding the incremental value to the step value.