149 results about "Pseudorandom noise" patented technology

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

A receiver (100) is provided for signals of different signal strengths and modulated with respective pseudorandom noise (PN) codes. The receiver (100) includes a correlator circuit (120) operable to correlate the signals with a selectable locally-issued PN code having a Doppler and a code lag to produce a peak, the correlator circuit (120) being subject to cross correlation with a distinct PN code carried by least one of the signals that can produce cross correlation; and a cross correlation circuit (370, 400) operable to generate a variable comparison value related to the cross correlation as a function of values representing a Doppler difference and a code lag difference between the locally-issued PN code and the distinct PN code, and to use the variable comparison value to reject the peak as invalid from cross correlation or to pass the peak as a valid received peak.

A dithering pattern that is generated based on a spatial operation is used for a Bit-Depth Extension (BDE) technique for preventing contouring artifacts in an image displayed by a display having a bit-depth that-is less than the bit-depth of the image. The dithering pattern can be based on achromatic visual model or a spatio-chromatic visual model. The dither pattern is formed by shaping a pseudo-random noise signal by an equivalent noise visual model that is based on an array of pixels. Alternatively, the array of pixels is based on an image, or a determinate array of pixels.

A novel technique for embedding a reversible watermark into digital media files, and then removing this watermark, in whole or in part, at some later date, without access to the original media file, which may consist of such media types as audio, image, video, 3-D and the like; such watermarks being primarily intended for, though not limited to, the introduction by a reversible mathematical operation of perceptually significant elements, including but not limited to pseudorandom noise, such that the degraded media is suitable merely for demonstration or trial purposes, and with the watermark resistant to removal without proper authorization; but with authorization, can then be removed from the media file to prepare it for its ultimate high-quality use.

A technique for allowing a first and second group of users to share access to a communication channel such as a wireless radio channel is disclosed. The first group of users can be a group of legacy users such as those that use digital CDMA cellular telephone equipment based on the IS-95 standard. The second group of users can be a group of web surfers that code their transmissions using one of multiple formats. The first group of users can share one modulation structure such as, on a reverse link, using unique phase offsets of a common pseudorandom noise (PN) code. The second group of users can share another modulation structure, but in a manner that is consistent and compatible with the users of the first group. Specifically, the users of the second group may all use the same PN code and code phase offset. Each channel used by the second group of users can be uniquely identified by a corresponding unique orthogonal code.

The present invention relates to a signal generator and signal processor for single carrier wireless communication systems with frequency domain equalizer, which are operable to use pseudorandom-noise sequences as part of a preamble and possibly as cyclic prefix. The different arrangements and examples of said pseudorandom-noise sequences could be used for coarse timing synchronization, channel estimation, carrier synchronization, signal-noise-ratio estimation and channel equalization.

An improved satellite communication system is provided comprising at least one satellite wherein each satellite provides multiple beams, a plurality of UTs, and at least one gateway connected to a PSTN and communicating with said at least one UT or with a constellation, wherein each of the UTs within a given frequency band is distinguished from another of the UTs employing a combination of TDM and NOPN codes and time slots.

The invention relates to a time-frequency synchronization joint estimation method based on a multi-carrier receiver of a digital television media broadcast (DTMB) system. The method is characterized by comprising the following steps: step 1, carrying out frame header mode recognition and frame header position coarse estimation; step 2, generating a pseudorandom noise (PN) sequence A of a zero phase matched with the frame header mode by a local PN generator, and carrying out carrier frequency offset estimation by utilizing a step-variable frequency sweeping method; step 3, correlating received data with the PN sequence A after compensation carrier is subjected to large frequency offset, so as to estimate a serial number of a frame; generating a PN sequence B of a matched phase matched with the frame header mode, and then correlating the PN sequence B with the received data so as to obtain a frame header position fine estimation value; and step 4, carrying out self-correlation on the frame header position according to the frame header position fine estimation value so as to obtain a carrier frequency offset fine estimation value, and summarizing a carrier frequency large offset estimation value and the carrier frequency offset fine estimation value so as to obtain a final carrier frequency offset estimation value. In the invention, the time-frequency synchronization joint estimation method based on the multi-carrier receiver of the DTMB system is used, thereby facilitating the realization of share of operation data and parameters and reducing the arithmetic labor.

A two-dimensional wavelength/time optical CDMA system employing balanced-modified pseudo random noise (PN) matrix codes is provided. Through an inverse-exclusive OR operation of a pair of modified PN code, the balanced codes are generated as optical CDMA codes in the form of a new matrix. When the codes are applied to an optical CDMA system to perform encoding and decoding, if the same number of channels as the number (M−1) of subgroups of the codes are connected, the system becomes an MAI-free system, and even if the number of channels connected is twice the number of the subgroups, an error-free system can be established. Accordingly, the number of channels that can be used simultaneously is doubled compared to the prior art method such that the economical efficiency of the optical CDMA system improves.

The invention provides methods and devices for estimating power amplifier nonlinearity using simple correlation techniques. Methods and devices of the invention can monitor a power amplifier that has digitally modulated inputs and an output containing more than one signal stream. A preferred method of the invention creates a test signal by forming the products of several pseudorandom noise sequences from the digitally modulated inputs to the power amplifier. Nonlinear contributions of the power amplifier output are determined by cross-correlating the test signal and the total output signal of the power amplifier. In preferred embodiments, the determined nonlinear contributions of the power amplifier are used to introduce corrective predistortion in the power amplifier.

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

The method comprises: converting the received spread spectrum signals to the digital signals, and dividing the digital signals into the in-phase and quadrature signal components. In the capturing stage, the in-phase and quadrature signal components and the local pseudo random noise code are executed with relevant calculation to get the output of several in-phase and quadrature signal components; making summation for the square of each in-phase and quadrature signal components output to get the signal power and noise power in order to figured out the signal/noise ratio of the spread spectrum signals. In the tracing stage, the in-phase and quadrature signal components and the local pseudo random noise code are executed with relevant calculation; making the summation for the square of output result; based on the in-phase and quadrature signal components, figuring out the average power of noise; based on the signal power and the average power of noise, figuring out the signal/noise ration of spread spectrum signals.

Techniques for fast-slewing of multi-sequence based PN generators are disclosed. In one aspect, LFSR states and reference counter states are loaded into their corresponding components such that consistency among the states is maintained. In another aspect, various methods for determining LFSR states and counter values in response to a desired offset in a unique code are disclosed. Among these methods are matrix-multiplication of LFSR states and generation of advanced LFSR states through masking techniques. Other methods are also presented. These aspects have the benefit of decreasing slew time in an efficient manner, which translates to increased acquisition speed, faster finger lock on multi-path signals, increased data throughput, decreased power, and improved overall system capacity.

A method for acquisition of a weak signal from a satellite in the presence of a strong interfering signal from another satellite is disclosed. The method encompasses identifying the auto-correlation peak due to the weak satellite signal from the cross correlation peaks due to the strong satellite signal. This invention presents a method and apparatus of acquiring a weak satellite signal in the presence of a strong interfering satellite signal in a receiver by two techniques, namely, the millisecond boundary correlation histogram method, and the frequency response correlation histogram method. Both the techniques distinguish between the correlation characteristics for auto-correlation and cross-correlation. The apparatus presented in the invention implements the methods of weak satellite signal acquisition in presence of a strong interfering satellite signal in a pseudorandom noise (PRN) receiver.

A power of a square matrix is determined in a time approximately proportional to the upper integer of the base-2 logarithm of the order of the matrix. A preferred embodiment uses two types of look-up tables and two multipliers for a matrix of 15×15, and is applied to a pseudorandom noise (PN) sequence phase correlation or state jumping circuit. An exact state of a PN code can be determined or calculated from applying an appropriate offset value into a control circuit. The control circuit can produce a PN sequence state from the offset value and typically does so within one system clock period regardless of the amount of the offset. Once the exact state is determined, it is loaded into a state generator or linear sequence shift register (LSSR) for generating a subsequent stream of bits or symbols of the PN code. The PN generator system may include state computing logic, a maximum length PN generator, a zero insertion circuit and a zero insertion skipping circuit.

A receiver acquires and tracks a spread spectrum navigation signal with changing subcarriers. The carrier signal changes between several subcarriers according to a hopping frequency and is modulated with data and a pseudorandom noise code signal. The receiver includes a carrier wipe off unit for down converting a received spread spectrum navigation signal from its carrier frequency to a baseband frequency, a frequency hopping wipe off unit for wiping off the hopping frequency from the received spread spectrum navigation signal, and a replica signal generation unit for generating at least one replica signal of the pseudorandom noise code signal for acquiring and tracking the received spread spectrum navigation signal after carrier wipe off. The generation of the at least one replica signal is performed depending on a sojourn time of the spread spectrum navigation signal at a subcarrier and a selected predetection integration time, and a correlation and integration unit correlates and integrates the received spread spectrum navigation signal after carrier wipe off with the at least one replica signal for the selected predetection integration time.

A direct-sequence-spread-spectrum (DSSS) optical-frequency-shift-keying (OFSK) code-division-multiple-access (CDMA) communication system is adapted with optical transmitters and receivers for preferred use fiber optical communication systems where modulated data and pseudorandom noise (PRN) codes are encoded in the optical domain and communicated over optical paths for increasing system capacity in wide area optical networks.

A method of detecting a jamming signal (304) in a wireless device (102) includes providing a plurality of channels (401), wherein each of the plurality of channels has an NCO frequency (428, 429), and receiving a channel lock indicator (430, 431) for each of the plurality of channels. A jamming signal is detected if the NCO frequency of each of the plurality of channels differs by an integer multiple of an inverse of a pseudorandom noise code period (424, 425). A wireless device includes a plurality of channels, wherein each of the plurality of channels has an NCO frequency. A frequency tracking loop for each of the plurality of channels outputs a channel lock indicator for each of the plurality of channels. A jamming detection module receives the channel lock indicator and the NCO frequency from each of the plurality of channels. The jamming detection module detects an interference condition if the NCO frequency of each of the plurality of channels differs by an integer multiple of an inverse of a pseudorandom noise code period.

The present invention relates to a system for locating non-cooperating objects by means of a random or pseudo-random noisy type waveform generator, an amplifier, of said waveforms and an antenna which radiates them towards the object, which object generates an electromagnetic echo which is detected by a passive subsystem of antennas and receivers. The time delay and Doppler shift values are determined in the latter subsystem and in turn forwarded from encoding and modulating blocks to a central processor which estimates the position and the speed of the object. The passive subsystem receives, through a transmission channel or storage element, the reference signal which represents the transmitted noisy type waveform and uses it for calculating the bi-dimensional cross correlation (ambiguity function), which permits to estimate the time delay and the Doppler shift.