Abstract: Apparatus to measure signal-to-thermal noise ratio (SNR) and signal-to-pulse noise ratio (SPNR) includes a pulse noise reduction unit, an SNR estimation unit and an offset compensation unit; a pulse noise separation unit, and an SPNR estimation unit. Pulse noise separation unit includes (i) a first low pass filter (LPF), an impulse noise separator and a high pass filter (HPF), connected in series; and (ii) a second LPF, a pulse noise detection unit and an inverter. Pulse noise detection unit includes two channels, each with a high pass filter, an absolute value calculation unit, a low pass filter, a comparator, a pulse generator. The channels connect to OR gate, which outputs a pulse detection signal. Pulse noise reduction unit and pulse noise separation unit input in-phase and quadrature components. The SPNR estimation unit inputs a filtered in-phase component. The offset compensation unit outputs SNR, and the SPNR estimation unit outputs SPNR.

Abstract: A quadrifilar helix antenna includes a cylindrical support extending along an antenna axis; a plurality of spiral conductors wrapped helically on the cylindrical support and along the antenna axis from a feed end to a remote end; a circular ground plane perpendicular to the antenna axis; and each of the spiral conductors including a plurality of gaps, with the gaps having capacitors between conducting portions of the spiral conductors. The capacitors are positioned higher than 60 mm above the ground plane, and capacitance value varies inversely with height. The antenna exhibits a DU(10°)=?20 dB or better at an operating frequency f0=1575 MHz. The diameter of the cylindrical support is 30+/?5 mm. A total height of the cylindrical support is 300+/?50 mm. A winding angle of the helix is variable.

Abstract: An antenna includes a planar ground plane, a planar exciter, and a plurality of passive elements. The planar ground plane and the planar exciter are disposed orthogonal to a longitudinal axis of the antenna. The planar exciter is spaced apart from the ground plane. The planar exciter is configured to excite right-hand circularly-polarized electromagnetic radiation. The planar exciter is configured to excite first currents orthogonal to the longitudinal axis and substantially no current parallel to the longitudinal axis. The plurality of passive elements is symmetrically disposed azimuthally about the longitudinal axis and spaced apart from the planar exciter. The plurality of passive elements is electromagnetically coupled to the planar exciter. The plurality of passive elements is configured to excite second currents parallel to the longitudinal axis and third currents orthogonal to the longitudinal axis.

Abstract: A global navigation system includes a first navigation receiver located in a rover and a second navigation receiver located in a base station. Single differences of measurements of satellite signals received at the two receivers are calculated and compared to single differences derived from an observation model. Anomalous measurements are detected and removed prior to performing computations for determining the output position of the rover and resolving integer ambiguities. Detection criteria are based on the residuals between the calculated and the derived single differences. For resolving integer ambiguities, computations based on Cholesky information Kalman filters and Householder transformations are advantageously applied. Changes in the state of the satellite constellation from one epoch to another are included in the computations.

Abstract: A positioning system that combines the use of real-time location system and a robotic total station into a single, transparent hybrid positioning system to locate one or multiple targets by one or multiple users.

Abstract: A broadband quadruple helical circularly-polarized antenna for receiving GNSS signals comprises an excitation circuit and a set of quadruple spiral elements. Each quadruple spiral element consists of four conductors. Each conductor is a one spiral turn of the quadruple spiral element. Said conductors have equal winding angle. The winding angle of all conductors does not change in the same quadruple spiral element. Conductors of neighboring (longitudinally) quadruple spiral elements have different winding angles. The antenna provides a sharp drop in AP at angles near the horizon and a small AP level in the lower hemisphere.

Abstract: A method and system utilizing one or more agricultural drones in combination with agricultural equipment, e.g., an agricultural boom sprayer, to evaluate the crops being farmed, and to improve the real-time delivery and dispensing of liquid from the sprayer including monitoring and verifying that the liquid is being dispensed correctly and/or in accordance with a desired distribution pattern or level.

Abstract: Multipath reception by an antenna is reduced by mounting the antenna on a semi-transparent ground plane that has a controlled distribution of layer impedance over a central region and a peripheral region. The central region includes a continuous conductive segment on which the ground element of the antenna is disposed. The distribution of the layer impedance over the peripheral region is configured by multiple conductive segments electromagnetically coupled by lumped circuit elements. A semi-transparent ground plane can be fabricated by depositing a metal film on a dielectric substrate and etching grooves into the metal film to form a desired pattern of conductive segments. Lumped circuit elements can be fabricated as discrete devices, surface mount devices, and integrated circuit devices. Various semi-transparent ground planes can be configured for linearly-polarized and circularly-polarized radiation.

Abstract: A first plurality of differences (first differences or second differences) of carrier phase measurements of global navigation satellite system (GNSS) signals corresponding to a first measurement epoch is received. A plurality of differences of carrier phase ambiguities of the first plurality of differences of carrier phase measurements is resolved. A first fixed position of the rover is computed. A first plurality of sub-corrections is computed based at least in part on the first fixed position of the rover, a position of the base, a position of each specific GNSS satellite, and the first plurality of differences of carrier phase measurements. The first plurality of sub-corrections is then used to reduce the processing time for ambiguity resolution of carrier phase measurements in subsequent measurement epochs. The sub-corrections can be smoothed, aged, or smoothed and aged.

Abstract: A method for measuring a signal-to-noise ratio when decoding Low Density Parity Check (LDPC) codes is provided. The method includes receiving from an input of a demodulator an input code word with “strong” or “weak” solutions, decoding the input code word in a LDPC decoder using a predetermined dependence of a mean number of iterations on the signal-to-noise ratio, recording a number of iterations performed during the decoding of the input code word, averaging derived values of the number of iterations for a specified time interval, estimating a signal-to-noise ratio based on averaged derived values of the number of iterations and based on the predetermined dependence of the mean number of iterations on the signal-to-noise ratio, and generating an output decoded code word.

Abstract: A laser measuring system is provided by combining N-beams, angle based modulation and a laser receiver and laser transmitter configured with corner reflectors for signal shift measuring to facilitate full three dimensional positioning.

Abstract: A quadrifilar helix antenna includes a cylindrical support extending along an antenna axis; a plurality of spiral antenna elements wrapped helically on the cylindrical support and along the antenna axis from a feed end to a remote end; a ground plane having a diameter of about 300 mm and perpendicular to the antenna axis; and each of the antenna elements including a plurality of breaks, with the breaks having capacitors between conducting portions of the antenna elements. All capacitors a positioned higher than 60 mm above the ground plane, and capacitance value varies inversely with height. The antenna exhibits a DU(10°)=?20 dB or better at an operating frequency f0=1575 MHz. The diameter of the cylindrical support is 30 +/?5 mm. A total height of the cylindrical support is 300 +/?50 mm. A winding angle of the helix is variable.

Abstract: System for digital sweep type spectrum analysis with up/down frequency provides measurements of frequency spectrum of complex analog baseband input signal. The signal is quantized into three levels with fs based on the bandwidth of the input signal. Four multiplexers, a first block of registers and a block of adders perform operations equivalent to complex multiplication of the quadrature components. Two complex signals with up and down shifted spectrum are produced by the adders. The quadrature components are inputted to the accumulators with reset, which act as low-pass filters and accumulate several samples at a constant frequency fLO of the local oscillator. Levels of two accumulated complex samples are estimates of input signal spectrum in two frequency points +fLO and ?fLO. A sweep controller changes a frequency of the local oscillator from zero up to fs/2. Estimates of the input signal spectrum are generated sequentially in range ?fs/2 to +fs/2.

Abstract: A system and method for providing guidance to a user of a construction machine include computing kinematic behavior of a construction machine based on data received from the construction machine while performing a task. The kinematic behavior is compared with a model for operating the construction machine for performing the task. Feedback data is sent to the construction machine based on the comparing to provide guidance to the user of the construction machine for performing the task.

Abstract: A method and system utilizing one or more agricultural drones in combination with agricultural equipment, e.g., an agricultural boom sprayer, to evaluate the crops being farmed, and to improve the real-time delivery and dispensing of liquid from the sprayer including monitoring and verifying that the liquid is being dispensed correctly and/or in accordance with a desired distribution pattern or level.

Abstract: An antenna system for a global navigation satellite system reference base station is disclosed. The antenna system includes an antenna positioned above a high capacitive impedance surface (HCIS) ground plane. Over a specific range of the lateral dimension of the HCIS ground plane and the height of the antenna above the HCIS ground plane, a high level of multipath suppression and high sensitivity for low-elevated satellites can be simultaneously maintained. The HCIS ground plane can be fabricated as a flat conducting plate with an array of conducting elements such as pins, pins with expanded tips, or mushroom structures. Alternatively, the HCIS can be fabricated as a flat conducting plate with a concentric series of choke rings. The antenna system can provide a positioning accuracy of +/?1 mm, an order of magnitude improvement over previous designs.

Abstract: A digital system of measuring parameters of the signal (phase, frequency and frequency derivative) received in additive mixture with Gaussian noise. The system is based on the use of variables of a PLL for calculating preliminary estimates of parameters and calculating the corrections for these estimates when there is a spurt frequency caused by a receiver motion with a jerk. A jerk is determined if the low pass filtered signal of the discriminator exceeds a certain threshold. The jerk-correction decreases the dynamic errors. Another embodiment includes a tracking filter for obtaining preliminary estimates of parameters to reduce the fluctuation errors. Estimates are taken from the tracking filter when there is no jerk and from the block of jerk-corrections when there is a jerk.

Abstract: A test installation for simulating multiple reflections of GNSS signals, the installation including a top screen that is semitransparent in a radio frequency portion of the electromagnetic spectrum, wherein the top screen is substantially dome-shaped; a bottom screen that is reflective in the radio frequency portion of the electromagnetic spectrum; the top semitransparent screen over the bottom reflecting screen; and a GNSS antenna connected to a receiver and located between the top screen and the bottom screen.

Abstract: An antenna system for a global navigation satellite system reference base station is disclosed. The antenna system includes an antenna positioned above a high capacitive impedance surface (HCIS) ground plane. Over a specific range of the lateral dimension of the HCIS ground plane and the height of the antenna above the HCIS ground plane, a high level of multipath suppression and high sensitivity for low-elevated satellites can be simultaneously maintained. The HCIS ground plane can be fabricated as a flat conducting plate with an array of conducting elements such as pins, pins with expanded tips, or mushroom structures. Alternatively, the HCIS can be fabricated as a flat conducting plate with a concentric series of choke rings. The antenna system can provide a positioning accuracy of +/?1 mm, an order of magnitude improvement over previous designs.

Abstract: A navigation receiver operating in a differential navigation mode can change from one solution type to another. At each epoch, primary estimates of coordinates and the solution type are received. Each solution type has a corresponding accuracy. To improve the positioning quality when the solution type changes, smoothed estimates of coordinates are generated according to a two-branch algorithm. Two conditions are evaluated. If both conditions are satisfied, the current-epoch smoothed estimates of coordinates are set equal to the current-epoch extended estimates of coordinates calculated from the sum of the previous smoothed estimates of coordinates and coordinate increments calculated from carrier phases. If at least one of the conditions is not satisfied, updated smoothed estimates of coordinates are generated based on the sum of the current-epoch extended estimates of coordinates and a correction signal.