First Pacific Networks

Zircon Corporation

Hybrid Networks, Inc.

James C Long

Charles E Heger

Robert P McNamara

Noel H Marshall

Eduardo J Moura

Michael J Serrone

Paul W Dodd

Chinh Q Phan

Timothy P Murphy

Long K Tran

David E Hansen

Francis M Baker

A cost-effective wideband radar system capable of locating objects, such as reinforcing steel rods, pipes, and air bubbles, objects located behind or within a volume of, e.g., concrete, soil, wood, or air. A sequence of wideband radar pulses are emitted without a carrier from each of two transmit antennas. The system includes a receiver that detects reflected pulse energy (echoes) that result when transmitted pulses encounter a change in material (e.g., an air to metal change or concrete to metal change). These amplitudes of the echoes are visually displayed along with the length of the transmit/echo path for each transmitter. The lengths of the displayed transmit/echo paths are compared to determine whether the system is centered over an object located within or behind a volume, the system being centered over the object when the transmit/echo paths for each transmitter/receiver combination are of equal length.

Dual transmitter visual display system

A pyramidal horn antenna that decreases ringing in radar systems that are placed against a solid volume of e.g. concrete or wood for finding an object in or behind the solid volume. The antenna includes a solid, pyramid-shaped dielectric, the pyramid shape including a rectangular base and four triangular sides that extend from the base to meet at the apex of the pyramid. Two conductive triangular plates overlay opposite ones of the four sides of the pyramid, each of the plates including an electrical connection for coupling the plate to a radar system. The pyramid-shaped dielectric has a dielectric constant that approximates the dielectric constant of the solid volume, and therefore provides an impedance match between the antenna and the solid volume.

Ultra wide-band radar antenna for concrete penetration

A hybrid transmission system is provided to transmit and receive high-speed digital information in the form of variable length packets using standard television practices and components. The basic building block of this hybrid digital transmission system is the device at the remote location that receives the analog broadcast TV-like signal processed by a standard vestigial sideband video modulator. This device decodes the digital information from the signal and then passes it along as digital information to any form of a data terminal equipment or computer.

Remote link adapter for use in TV broadcast data transmission system

A baseband signal is spectrally efficiently transmitted on a broadband transmission medium by inserting gaps in packets of digital data transmitted in a modulated first radio frequency carrier. The transmitted packets of data are received by demodulating the modulated first radio frequency carrier, and the gap is monitored for the presence of digital data thus indicating a collision of simultaneously transmitted packets of digital data. A seed of arbitrary digital bits are used in scrambling each packet of digital data and is transmitted with the packet of data for use in descrambling the data. In retransmitting the packet of data the seed is included. The originally transmitting node receives the retransmitted packet and compares the retransmitted seed with the originally transmitted seed for detecting an error in retransmission.

Spectrally efficient broadband transmission system

A communication network having a first broadband communications channel or transmitting bus and a second broadband communications channel or receiving bus, wherein the first broadband communications channel passes information upstream to a head end employing an offset quadrature phase shift keyed (OQPSK) modulator in bursts, and the second broadband communications channel passes information downstream from the head end to remote nodes in a continuous bit stream. All nodes of the system are coupled to both the first communications channel and the second communications channel. According to the invention, modulation of signals applied to the first communication channel is optimized for burst communication from a plurality of sources to central control at the head end, and modulation applied to the second communications channel is optimized for continuous communication from the central source to a target node. In one specific embodiment, the communication between the central unit (head end) and any one of a choice of target nodes through the second communication channel is by means of three-level class one partial response AM-PSK modulated onto a carrier, which is optimized for continuous operation.

Modulation and demodulation system employing AM-PSK and QPSK

According to the invention, value errors in a recorded digital symbol are minimized by generating, from a high-speed sampling clock, a local clock which is synchronized to a selected sample time of a sampler which substantially over samples the received data stream, and then using the locally-generated clock to reconstruct the symbol synchronously with the locally-generated clock. The specific techniques are employed during the preamble of a synchronous system to select an optimum sample time for use in generating the local clock. Several specific techniques may be employed to mimize error. In order to find the center of a data symbol, particularly a binary digital data symbol in a digital data stream, a Read Only Memory (ROM) may be provided in which is stored all combinations of addresses of taps for the center of a symbol in response to address input representing the binary value of the signal in a shift register. The tap outputs of a shift register are coupled directly to the address inputs of a ROM of appropriate address width, and the ROM produces as its data output the address of the tap representing the center of the input symbol. The ROM can examine a plurality of sample time positions simultaneously.

Method and apparatus for synchronizing digital data symbols

A method and an apparatus for demodulating M-ary PSK signals of the type wherein the modulation is limited to phase transitions between adjacent phase states. The method is operative in a demodulator which comprises a phase splitter dividing a source signal into three paths with a preselected phase relationship among phases, one of the phases being delayed by nominally one bit period, a pair of mixers or multipliers, each one of the mixers receiving as one input a representation of the delayed-phase component and each one of the mixers receiving as a second input a representation of one of the other of the phase components. Combined signals are provided by the mixers to a combiner which adds or subtracts the combined signals according to expected input signal type to produce from one to N intermediate output signals. An intermediate output signal is coupled to a corresponding two-level comparator, each of which receives and responds to the respective intermediate output signals to produce a digital output. Digital logic circuitry responds to the digital outputs of each of the comparators to map the digital outputs into a single digital bit stream of ones and zeroes.

Growing community of inventors

Sunnyvale, CA, United States of America

James C Long