454 results about "Spread spectrum modulation" patented technology

Methods and apparatus are described for marine asset security and tracking (MAST). A method includes transmitting identification data, location data and environmental state sensor data from a radio frequency tag. An apparatus includes a radio frequency tag that transmits identification data, location data and environmental state sensor data. Another method includes transmitting identification data and location data from a radio frequency tag using hybrid spread-spectrum modulation. Another apparatus includes a radio frequency tag that transmits both identification data and location data using hybrid spread-spectrum modulation.

A petroleum well has an electronic module and a number of sensors which communicate with the surface using the tubing string and casing as conductors. Induction chokes at the surface and downhole electrically impede AC flow through the (tubing or casing if so configured) with the resulting voltage potential useful for power and communication. A high bandwidth, adaptable spread spectrum communications system is used to communicate between the downhole electronics module and a surface master spread spectrum modem. Downhole sensors, such as pressure, temperature, acoustic and seismic sensors accurately assess downhole physical conditions. In a preferred form, the electronics module and sensors are wireline insertable and retrievable into a side pocket mandrel in the tubing string. Permanent downhole sensors that can communicate with the surface allow such diverse applications as optimizing well and field performances, monitoring and assessing the geophysics of the fomrations around the well, assessing well and reservoir reserves, assessing reservoir conditions.

A spread spectrum detector employs a Doppler phase correction system that improves correlation of pseudo-noise (PN) codes to a received spread spectrum signal by combining phase shifts, in the time domain, to correlation values that compensate for the Doppler shift error that is inherent in the signal and that is imposed upon the signal by movement between the signal source and receiver. In architecture, the Doppler phase correction system includes a receiver to receive a spread spectrum modulated signal having the Doppler shift error, a multiplier to produce a plurality of complex first correlation values based upon the signal and a code. A phase shifter generates a plurality of complex second correlation values respectively from the first correlation values. The second correlation values being phase shifted by respective different amounts from corresponding first correlation values, so that the second correlation values exhibit less of the Doppler shift error than the first correlation values. The phase shifter can be implemented with a look-up table that stores a plurality of phase shift values, a counter that produces indices for the look-up table, and a multiplier that multiplies the phase shift values that are output from the look-up table with the first correlation values to produce the second correlation values. Finally, a combiner, such as an integrator, combines, or integrates, the second correlation values to derive a third correlation that indicates a degree of correspondence of the code with the signal.

Circuits and methods of LED dimming are disclosed. Frequency modulation using controlled modulation depth generates deterministic sidebands of both the fundamental frequency and its harmonics. Various filters including low-pass, band-pass, high-pass and combinations of those are used to selectively filter the deterministic frequency components generated by the frequency modulation to achieve LED dimming.

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station (BS), and a plurality of subscriber units. The signals transmitted between the base station and subscriber unit use spread-spectrum modulation. The improvement apparatus for adaptive forward power control (APC) from a base station (BS) to a subscriber unit (SU), includes sending from the base station, using spread-spectrum modulation, a BS-spreading code on a forward channel. The subscriber unit despreads the BS-spreading code on the forward channel as a despread signal, determines a first power level Pd which includes power of the despread signal plus noise and a second power level PN, which includes despread-noise power. The subscriber unit determines a first error signal e1, from the first power level Pd, the second power level PN, and a required signal-to-noise ratio SNRREQ for service type, and a second error signal e2, from a measure of total received power Pr and an automatic gain control (AGC) set point Po. The subscriber unit forms a combined error signal from the first error signal e1, the second error signal e2, a first weight a1 and a second weight a2, and hard limits the combined error signal to form a single APC bit. The APC bit is transmitted to the base station. In response to the APC bit, the base station adjusts transmitter power to the subscriber unit.

The present invention provides encryption techniques useful with digital watermarking payloads. In a first implementation, we encrypt one of two different cooperating watermark payloads, but the encryption and payload data structure helps to authenticate both payloads. Another implementation provides a three encryption key pair system for managing messages and watermark embedding. Still another aspect of the invention is a watermark embedding process that uses encryption to whiten, randomize or spread a message, instead of convention spread-spectrum modulation.

A system and method for the automatic establishment of a connection between a human interface device and a host transceiver unit, wherein the system includes a host transceiver unit configured to be connected with a host via a bus, and configured to wirelessly exchange data with a human interface device; a human interface device configured to wirelessly exchange data with a host transceiver; and a computer readable media having instructions thereon, wherein said instruction include routines for synchronizing the host transceiver unit and the human interface device for wirelessly exchanging data between the host transceiver unit and the human interface device at a spread spectrum modulation pattern which is determined by the host transceiver after the host transceiver unit and the human interface device have acknowledged each other's presence.

The invention refers to a method and an apparatus for determining characteristics of components of a communication channel. In order to simplify the intersystem coordination in a beginning of life test of a satellite communication channel and avoiding the interference of adjacent satellite systems the method according to the invention comprises the following steps: modulating a clean carrier signal f(t) by spread spectrum modulation to generate a spreaded clean carrier signal s(t); transmitting said spreaded clean carrier signal s(t) through said communication channel at a first predetermined level; receiving a receive signal s′(t) corresponding to said spreaded clean carrier signal s(t) after having traveled through said communication channel; demodulating said receive signal s′(t) by spread spectrum demodulation to generate a despreaded carrier signal f′(t); determining characteristics of components of the communication channel on the basis of a comparison of said clean carrier signal f(t) and said despreaded carrier signal f′(t).

A method and apparatus for physically secure communication over machine-to-machine (M2M) networks is claimed, through the use of frequency-hop and random access spread spectrum modulation formats employing using truly random spreading codes and time/frequency hopping and receiver selection strategies at the transmitters in the M2M network, blind signal detection and linear signal separation techniques at the receivers in the M2M network, completely eliminating the ability for an adversary to predict and override M2M transmissions. Additional physical security protocols are also introduced that allow the network to easily detect and identify spoofing transmissions on uplinks and downlinks, and to automatically excise those transmissions as part of the despreading procedure, even if those transmissions are received at a much higher power level than the intended transmissions. Extensions to weakly and strongly macrodiverse networks are also described, which provide additional efficiency and security improvements by exploiting the route diversity of the network.

A transponder satellite communication navigation positioning system relates to the field of space technology. The system is equipped with a high-precision atomic clock at a ground communication navigation reference station, and the satellite orbit data is given by the satellite orbit determination system; the satellite integrity is given by the monitoring system The data forms the navigation message, and the ranging code composed of pseudo-random codes forms an integrated baseband signal, which is modulated by spread spectrum to form a navigation signal carrier, which is transmitted through the antenna and forwarded by 3 to 9 satellites in a certain geometric distribution in space The device converts the frequency and forwards the downlink, and broadcasts the signal to the coverage area; the ground user terminal receiving device receives the navigation signal carrier, and despreads and demodulates it to obtain the navigation data, thereby determining the position, speed and time of the user terminal receiving device. The invention has the advantages of low investment, guaranteed accuracy, convenient and flexible system maintenance and management, and dual functions of navigation and communication, so that the navigation and positioning accuracy can reach meter-level precision or be better than meter-level precision.

The present invention relates to a method and an apparatus for spread spectrum modulation and demodulation using a special spread spectrum sequence, characterized in that Golay complementary codes are modulated onto orthogonal channels such that a corresponding complex complementary code is obtained. The signal spread by such complex complementary code has a low peak-to-average power ratio, a sound self-correlation property and cross-correlation property, which can well solve the problem of multi-access interference such that the communication performance of the entire system is improved.

The invention discloses a no-filter D-class audio amplifier based on the chaos frequency spreading modulating technology, mainly comprising a chaos frequency spreading triangle-wave generator, a comparator and a full-bridge output-stage circuit, wherein the chaos frequency spreading triangle-wave generator is used for generating chaos frequency spreading triangle-wave signals. When an audio signal is sent, the comparator is used for comparing voltage values of the audio signal and the chaos frequency spreading triangle-wave signal to output a square wave signal with changeable dutyfactor. After the power of the square signal is amplified by the full-bridge output-stage circuit, the square signal is outputted to a loudspeaker and recovered to the audio signal above the loudspeaker. The invention has the following advantages that the electromagnetic interference of the output signal of the D-class amplifier is effectively inhibited under the condition of no filter, the integration is easy, the chip area is saved, and the linearity of the chaos frequency spreading triangle wave used as the PWM carrier wave is not influenced by the modulation signal (chaos sequence) is guaranteed, thus, the distortion factor of the output audio signal is not influenced.

According to an inventive scheme for introducing a watermark into an information signal, the information signal is at first transferred from a time representation to a spectral/modulation spectral representation). The information signal is then manipulated in the spectral/modulation spectral representation in dependence on the watermark to be introduced to obtain a modified spectral/modulation spectral representation, and subsequently an information signal provided with a watermark is formed based on the modified spectral/modulation spectral representation. An advantage is that, due to the fact that the watermark is embedded and/or derived in the spectral/modulation spectral representation or range, traditional correlation attacks as are used in watermark methods based on a spread-band modulation cannot succeed easily.

A spread spectrum clock generation circuit capable of further reducing the electromagnetic wave radiation with a simple configuration has been disclosed and, particularly in a spread spectrum clock generation circuit using a current control oscillator (ICO), a differential signal to which a spread spectrum modulation signal, the period or amplitude of which changes, is added is generated, and the differential signal is applied to the ICO and a clock is generated.

The present invention is a method and system for controlling a RC device via a secure radio link. In one embodiment of the invention, spread spectrum modulation may be employed which may provide a digital radio frequency (RF) link between a controller and a RC device. A controller may be coupled with a transmitter module and a radio controlled device may be coupled with a receiver module in accordance with the present invention to provide an add-on upgrade capability. The method and system for controlling a RC device may also include error detection and correction, interpolation of lost packets, failsafe technology and force-feedback telemetric technology to further enhance the user experience with radio controlled devices.

The embodiment of the invention discloses a spread-spectrum modulation circuit, a variable frequency triangle generator and a signal processing method. The spread-spectrum modulation circuit comprises the variable frequency triangle generator, a first comparator and a second comparator; the variable frequency triangle generator is respectively connected with the first comparator and the second comparator; the first comparator and the second comparator realize the spread-spectrum of the pulse width modulation (PWM) according to the input signal and the variable frequency triangle waves input by the variable frequency triangle generator. In the embodiment of the invention, the random signal is used to control the changes of the so as to generate a triangle wave circuit with changed frequency, the spread-spectrum modulation circuit is realized, the structure realization is simple, and the high-frequency distribution is similar to the distribution of white noise, thus effectively reducing the electromagnetic interference in the existing circuit.

Circuits, methods, apparatus, and systems for recovering a clock from a spread spectrum signal having a periodic modulation profile. The circuits generally include an error detector circuit configured to compare the spread spectrum signal and a recovered clock signal, and to produce a first error signal corresponding to the periodic modulation profile and a second error signal corresponding to phase differences other than the spread spectrum modulation, a record and playback unit configured to record a value to a frequency memory, said value based on the first error signal and produce a third error signal corresponding to a predicted periodic modulation based at least in part on the recorded value, and a signal generator configured to produce the recovered clock signal in response to the second and third error signals.

An analog front-end circuit that controls an imaging device and processes an analog image signal output from the imaging device comprises: an analog processor that receives an analog image signal from the imaging device, provides the image signal with predetermined processing, and outputs a resultant signal; an A/D converter that performs A/D conversion with the image signal output from the analog processor; a holding circuit that holds digital image data output from the A/D converter; a timing generator that, based on a first reference clock, generates a plurality of clocks and outputs the clocks to at least one of the analog processor and the A/D converter; and a spread spectrum modulation circuit that performs spread spectrum modulation with the first reference clock and outputs a resultant clock that has been subject to the spread spectrum modulation as a modulated clock to the holding circuit; wherein the holding circuit holds the digital image data from the A/D converter based on the modulated clock output from the spread spectrum modulation circuit.

Various embodiments of the invention are directed to orthogonal frequency chirp multiple accessing (OFCM) systems and methods. For example, various embodiments of the OFCM transmitter may utilize an architecture comprised of a baseband modulation subsystem, a subsystem for generating multiplicity N orthogonal frequency chirp waveforms, and a bank of multiplicity N spread spectrum modulators. Various embodiments of the OFCM receiver may comprise of a subsystem for generating complex conjugates of multiplicity N orthogonal frequency chirp waveforms, a bank of multiplicity N spread spectrum demodulators, a symbol estimator, a symbol timing estimator, a frequency offset estimator, a carrier phase tracking loop, a multi channel estimator, and a baseband demodulation subsystem.