Abstract: A method for comparing the relative phase of carrier signals received from GPS satellites to determine the roll, pitch and azimuth attitude of ships, aircraft, land vehicles, or survey instruments, accomplishes a maximum likelihood estimation (MLE) optimum solution over the full range of integers and vehicle attitudes. The problem is formulated as an MLE optimization, where vehicle attitude and integers are regarded as parameters to be adjusted to maximize probability of first-difference carrier phase measurements that are actually generated by hardware. Formulation results in weighted-fit error W as the objective criterion to minimize. A Kalman filter is introduced, having same objective criterion. Minimizing computation in Kalman filter leads to a decision tree for the integers. Two ways are shown to prune decision tree. The first is to exclude impossible combinations, such as those that produce an antenna upside down. The second is to generate a lower bound for W at each branch of the tree.

Abstract: An embodiment of the present invention is a diagonally fed electric microstrip RHP antenna having a ceramic substrate, a groundplane on one side of the substrate, a rectangularly-shaped radiator attached to the other side of the substrate, and a via that passes through the substrate and connects to a point on the radiating electrode that provides a predetermined impedance Z.sub.o, the via has an inductance L.sub.via such that an optimum impedance for a minimum noise figure .GAMMA..sub.o is presented to the opposite end of the via. A groundplane relief in the first side of the dielectric substrate allows an active device to be connected to the second end of the via and placed within the groundplane relief. An output matching network also inside the groundplane relief is used for coupling the active device to an external system, such as a Global Positioning System (GPS) receiver.

Abstract: A method for making printed circuit boards comprises using double treated copper foils for all inside conductor layers of multilayer packages with substrates of alloys of epoxy and polyphenylene oxide (PPO) resin to counteract the skin-effect encountered at high frequencies. Direct bonds between inside surfaces are then used without using an oxide step that introduces red/brown or black oxides.

Abstract: An embodiment of the present invention is a system for time multiplexing a carrier signal received by two or more GPS antennas through a single hardware path, using a single receiver's oscillator in that hardware path as a reference to compare the phase from each antenna. One of the antennas is designated as a reference antenna and a carrier signal received by it is used to phase lock in numerically controlled oscillator. The same carrier signal received by the other antennas is periodically compared in phase to the output of the numerically controlled oscillator. Each comparison results in a phase angle measurement for the respective antennas compared to the master antenna.

Abstract: A system, according to an embodiment of the present invention, comprises a coupler, a remote antenna, and a handheld GPS receiver. The remote antenna has a microstrip RHCP receiving element and a low noise amplifier (LNA) powered by the coupler over an interconnect cable. The coupler has a slotline antenna and a driver circuit. The coupler re-radiates GPS satellite signals received by the remote antenna with a slotline antenna to the GPS receiver. In a typical installation, such as a car, a user holds the GPS receiver while in the front seat. The coupler mounts to the windshield and the cable runs to remote antenna mounted on the roof of the car. The coupler can then re-radiate GPS satellite signals effectively to the GPS receiver even when the two are separated by as much as six feet. The shielding of GPS signals by the metal of the car is thereby avoided as a problem that can prevent operation of the GPS receiver.

Abstract: An electronic housing structure including an enclosure for containing at least one electronic device having a plurality of user interface switches. The electronic housing structure further has a user interface pad attached to the enclosure near the user interface switches for operating said user interface switches. The user interface pad further seals the enclosure to completely seal and protect the electronic device. The enclosure and the user interface pad are composed of a waterproof, dust-proof and mud-proof material whereby said electronic device can be operated in an outdoor condition.

Abstract: An embodiment of the present invention is a shipboard GPS positioning system having data links to outlying tailbuoys equipped with respective GPS receivers. On ship, an Intel 386-based microcomputer system collects data from various ship's equipment including the ship's GPS receiver and data from the several tailbuoy units. A computer-implemented process located in the microcomputer system controls the following processes. Periodically each GPS receiver produces updated pseudo ranges (PRs) and these are time-tagged. The time-tagged PRs for the ship are aligned according to their time tags with their counterpart PRs from the tailbuoys. The raw PRs are then passed through a Kalman mathematical filter to produce filtered pseudo-ranges (PRs). A position solution is then attempted for each GPS receiver using the PRs. The filters provide statistical data that is used to rate the quality of each PR in a weighted least squares solution process.

Abstract: Improved apparatus for generation of the P-code sequences used in global positioning by issuance and sensing of code sequences issued by a plurality of satellites. The improved apparatus generates the same P-code sequences with fewer components, or with different components, by removal or replacement of: (1) a time delay/multiplexer module that allows choice of the satellite whose P-code is being formed and issued; (2) four 12-bit counters that determine the end of an epoch and are associated with four X code registers; (3) components that produce precession of an X1 code sequence relative to an X2 code sequence; and (4) an end-of-the-period counter, used to sense occurrence of the end of a chosen period, for example, 7.0 days, for purpose of P-code re-initialization.

Abstract: An embodiment of the present invention is a voltage controlled oscillator (VCO) comprised of a differential pair of transistors that have respective positive feedback paths with phase-lead networks cross-coupled. Each positive feedback path on each side has two different phase-lead branches. The two phase-lead branches have the same phase differences on each side of the differential pair, in order to maintain a symmetry that improves common-mode noise rejection on a voltage control differential input. Current-steering is used to control the mixture of currents that arrive at the bases of the differential transistor pair from the respective two different phase-lead branches, and thereby changing the frequency of the VCO.

Abstract: An antenna comprises a base plate forming a ground plane, a coaxial feed serving as a mast connected to the base plate and extending along an axis that is normal to the ground plane, and two orthogonal dipoles each formed of two elements. Each dipole element has a first end connected to and supported by the mast at a first location spaced apart from the ground plane by a predetermined distance and a second end closer to the ground plane and exhibits a curvature in a plane containing the mast.

Abstract: A method for accurately determining the position of a roving signal receiver positioned on or above the Earth's surface, relative to the position of a reference receiver whose position is known with sufficient accuracy, using ranging information, transmitted at a pair of predetermined carrier signal frequencies and received from each of n satellites (n.gtoreq.4). Pseudorange double differences are formed, between each of the two receivers and each of a first satellite and the other three satellites, using pseudorange information obtained from either one of the two signal frequencies. Phase correction information, in the form of estimates of integer lane wavelength ambiguities, is then obtained from the pseudorange double differences and from certain measurable phase differences. This products n-1 simultaneous equations that can be solved for the roving receiver position cordinates.

Abstract: An antenna is employed to receive a (1540 f0) L1 GPS-satellite signal. In addition, a filter, an (RF) amplifier, a harmonic mixer, and a (sole) local oscillator are employed, the combination configured to mix the seventh harmonic of a 192 f0 local oscillator generated signal with the receive satellite signal to down-convert the frequency of the received GPS-satellite signal to a 196 f0 IF frequency. Further, another filter, an (IP) amplifier, and a mixer are employed, the combination configured to mix the fundamental of the 192 f0 local oscillator generated signal with the 196 f0 GPS-satellite signal to down-convert the frequency of the satellite signal to four f0. Finally, yet another filter and an amplifier are employed, the combination configured to filter and amplify the four f0 GPS-satellite signal.

Abstract: To reduce error introduced by the local oscillator in the velocity calculations, the receiver has two "tracking channels" and a microcomputer. With numbers required to, simultaneously, lock each of the "tracking channels" each to a respective satellite signal, the microcomputer employs a differential doppler technique to calculate the receiver velocity. The microcomputer calculates a number which represents the difference between the apparent doppler frequency shift of the carrier signal which is transmitted by the first "tracking channel" satellite and which is measured over a specific time period and the apparent doppler frequency shift of the carrier signal which is transmitted by the second "tracking channel" satellite and which is measured over substantially the same time period.

Abstract: Two receiver channels each driven by a common local oscillator signal are employed. The signal developed by the first receiver channel is used to drive in phase (I) and quadrature (Q) counters of a Castas-loop, which phase-locks to the signal. The signal developed by the second receiver channel is used to drive another pair of in phase (I) and quadrature (Q) counters, which develop signals from which heading information is calculated.

Abstract: A GPS satellite receiver is disclosed in which the frequency of the received satellite signal is down converted in a single step by a balanced mixer driven by a half-frequency local oscillator and the down-converted satellite signal is converted from analog-to-digital form by a hard limiter.