Abstract: A calibration procedure for reducing frequency-dependent bias effects in a fixed satellite-based ground-positioning receiver is disclosed, the receiver having the capability to receive both GPS and GLONASS satellite signals. The calibration procedure removes satellite dynamics by utilizing the respective satellite ephemeris data, estimates the change in receiver clock offset by means of GPS measurements, and acquires a set of two or more GLONASS pseudorange measurements while cycling a local oscillator in the receiver through a predetermined sequence of different frequencies.

Abstract: A method and apparatus is provided for reducing or eliminating the transmitter signal leakage, i.e., transmitter noise, in the receiver path of an RF communications system operating in full duplex mode. In an embodiment of the present invention, a noise cancellation loop produces an estimated transmitter signal leakage and cancels it from the receiver path to produce a received signal with little or no transmitter noise. Some of the advantages are that there is significant improvement in the isolation between the transmitter/receiver circuits, the size of the RF communications circuitry may be reduced, and the RF transmit module along with the RF receive module may be incorporated into a single RF IC chip.

Abstract: The invention is a multipath meter that analyses estimates of parameters associated with a direct signal component and one or more multipath signal components of a signal received by an antenna. The meter analyses the parameter estimates in order to facilitate the select of a location for an antenna, monitor signal quality at an existing antenna site, and/or to determine if satellite failure or some other type of signal failure has occurred. The multipath meter makes available to a user or for analysis information related to the contributions of the direct signal and the multipath signals to the received signal. The information includes estimates of various parameters such as delay, relative amplitude and phase of the direct and multipath signals. The meter calculates a ratio of the amplitudes of the direct and the multipath signals, to determine the severity of the multipath signals and, thus, the signal quality.

Abstract: A multi-mode mobile station performs an inter-system handoff between systems, qualified by the presence or absence of a preferred wireless communication network in a roaming lookup table stored and maintained in either mobile station memory or with the network controller. In one embodiment the accurate location of the mobile unit is determined by a global position fix, after which a coverage map is consulted to verify the availability of a preferred network before initiating a background scan. In other embodiments, a learning function creates habit profiles of a subscriber's regular behavior upon which the system intelligently initiates scanning for a preferred network.

Abstract: A planar, controlled radiation pattern array antenna using spiral slot antenna arrays is disclosed. The CRPA antenna includes a nonconductive planar substrate with a plurality of transmission lines disposed on one surface. A conductive layer on the other surface of the substrate includes a plurality of slotted openings that form spiral slot array antennas such that each spiral slot array antenna opposed to a transmission line on the opposite side of the substrate.

Abstract: A slot-array antenna includes a nonconductive substantially planar substrate and a transmission line disposed on a rear substrate surface where one end of the transmission line is connected to an amplifier, a connector, or an impedance load. A conductive layer on the front substrate surface includes a plurality of slotted openings arrayed about an antenna axis. A surface-wave suppression region encloses the array of slotted openings and a plurality of peripheral openings are disposed between the surface-wave suppression region and the peripheral edge of the antenna.

Abstract: A planar, phased-array antenna including a nonconductive substantially planar substrate and a transmission line disposed on one surface is disclosed, a segment of the transmission line forming an arc of radius R centered on the antenna axis. A conductive layer on the other antenna surface includes two or more slotted openings, each slotted opening having one end located within a distance R of the antenna axis, such that, when an electromagnetic signal is fed into one end of the transmission line, electromagnetic energy is sequentially coupled into the slotted openings, and a circularly-polarized signal is radiated from the antenna substantially in the direction of the antenna axis. An amplifier or a connector may be electrically connected to one or both ends of the transmission line, or one end of the transmission line may be terminated in an impedance load to form a leaky-wave antenna. The slotted openings may comprise either or both straight and curved segments, and may be of the same or unequal lengths.

Abstract: A time signal generation system produces a reference time signal based on the signals transmitted by geostationary satellites, such as the satellites in the Wide Area Augmentation System (WAAS). A receiver in the system includes a directional antenna that is focused on the signals transmitted by the geostationary satellite. The antenna rejects multipath signals, and the receiver thus tracks the satellite signal directly, without having to compensate for multipath distortion. Once the receiver is tracking the code and carrier, the receiver decodes the transmitted data to recover timing information, as well as satellite orbital correction information and an ionospheric model, or table, transmitted by the satellite. The receiver then uses the decoded information and timing pulses provided in synchronism with the transmitted PRN code to produce a corrected timing signal.

Abstract: According to the invention, a system utilizing satellites of known locations produces a sky map containing quality values relating locations in the sky to the quality of signals received from those locations. The sky map reflects known variability in signals received from satellites at selected areas of azimuth and elevation based upon historical data collected at a fixed or known GPS receiver location. The system uses the quality values to assign a weight to each set of measurements for that area in the sky. The invention thus improves the accuracy of GPS positioning by providing a good indicator of the quality of the measurements.

Abstract: A multi-position antenna assembly for use in portable wireless communication devices is disclosed. The assembly includes an antenna, a printed circuit board operative to electrically couple the antenna to a host device, a disk joint assembly, coupled to the antenna, operative to rotate the antenna about two axes of rotation, and an assembly housing which at least partially contains the printed circuit board and the disk joint assembly, and is adapted to be removably coupled to the host device. The disk joint assembly includes a joint housing having a projection piece which passes through the joint housing that enables the antenna to be positioned between alternating operating and storage positions within a PC card.

Abstract: GNSS receiver includes a subsystem that reduces the adverse effects of multipath signals on punctual and early-minus-late correlation measurements by making the correlation measurements using a “blanked-PRN code.” The blanked-PRN code is all zeros except for adjacent positive and negative short pulses that occur at every code bit transition in a locally-generated PRN code. Using the blanked-PRN code, the receiver makes non-zero correlation measurements only near the code bit transitions in the local PRN code. If the local PRN code and the PRN code in the received GNSS satellite signal are closely aligned, the non-zero correlation measurements are made at the times of the bit transitions in the received PRN code.

Abstract: A navigational apparatus includes a receiver, two antennas, and a computational unit to receive satellite positional signals and provides corrected position, azimuth, and pitch readings. The computational unit: determines differences in the signal carrier measurements output by the receiver; rejects or accepts carrier ambiguity candidates based on predefined criteria; and estimates multipath on successive pairs of carrier observations to obtain the corrected readings.