649 results about "Pulse-amplitude modulation" patented technology

The invention discloses an encrypting anti-counterfeiting printing technology for modulating the shapes of amplitude modulation dots of a printed work through a binary-system encrypting signal. In the anti-counterfeiting printing technology, anti-counterfeiting information is subjected to encryption and channel coding to form a binary-system modulating signal and the anti-counterfeiting information is embedded into a whole page by sequentially changing the shapes of the amplitude modulation dots in a circulating table lookup modulation way. During recognition of the printed work, the anti-counterfeiting information can be recognized from any fragment, so the anti-breakage performance is high, the illegal replication based on a camera, a scanner, an electronic document and the like can be more effectively prevented and the technology can be extensively applied to the field of printed work anti-counterfeiting.

The invention discloses a presswork encryption security printing technology based on multi-system quadrature amplitude modulation. By adopting the security printing technology, a paseudorandom modulating signal can be generated from anti-counterfeiting information through spread spectrum, encryption and channel coding, the anti-counterfeiting information can be embedded into a whole page through a multi-system quadrature amplitude modulation (QAM) mode, and the anti-counterfeiting information can be identified from any fragment in presswork identification. The invention has very strong smash-resistance, can effectively resist piracy behaviour based on cameras, scanners, electronic documents and the like, and can be widely applied to the field of presswork anti-counterfeit.

Systems (400, 500, 600) and methods (300) for generating a chaotic amplitude modulated signal absent of cyclostationary features by preserving a constant variance. The methods involve: generating a PAM signal including pulse amplitude modulation having a periodically changing amplitude; generating a first part of a constant power envelope signal (FPCPES) by dividing the PAM signal by a square root of a magnitude of the PAM signal; generating a second part of the constant power envelope signal (SPCPES) having a magnitude equal to a square root of one minus the magnitude of the PAM signal; and generating first and second spreading sequences (FSS and SSS). The methods also involve combining the FPCPES with the FSS to generate a first product signal (FPS) and combining the SPCPES with the SSS to generate a second product signal (SPS). A constant power envelope signal is generated using the FPS and SPS.

A lightning detection system for detecting and locating an initial discharge of an initial leader stroke of a lightning flash. An initial lightning discharge produces a pulse that can be used to accurately detect lightning, and more particularly, the location of the initial lightning discharge. In one embodiment, at least three sensors detect and determine the location of the first pulses from initial lightning discharges using time difference of arrival information of the pulses at each of the three sensors. In another embodiment, a single sensor is used to determine the range of an initial lightning discharge from the amplitude of a corresponding initial detected pulse, and to determine the direction from a crossed loop antenna An alternative embodiment of a single sensor system determines a distance of a lightning event from a peak amplitude value derived from a pulse amplitude distribution. In a further embodiment, a lightning detection system provides enhanced lightning location by incorporating weather data from a weather radar with detected lightning information.

An interface circuit for enabling clock and data recovery (CDR) of N-level pulse amplitude modulation (N-PAM) modulated data streams using a 2-PAM CDR circuit. The circuit comprises a number of N−1 comparators for comparing an input data stream to N−1 configurable thresholds, the input data stream is N-PAM modulated and the N−1 configurable thresholds are N−1 different voltage levels; a number of N−1 of edge detectors respectively connected to the N−1 comparators for detecting transitions from one logic value to another logic value, N is a discrete number greater than two; and a determination unit for determining if the detected transitions is any one of a major transition and a minor transition and asserting a transition signal if only a major transition or a minor transition has occurred, the transition signal is fed into a 2-PAM CDR circuit and utilized for recovering a clock signal of the input data stream.

Methods and systems for encoding multi-level pulse amplitude modulated signals using integrated optoelectronics are disclosed and may include generating a multi-level, amplitude-modulated optical signal utilizing an optical modulator driven by two or more electrical input signals. The optical modulator may include optical modulator elements coupled in series and configured into groups. The number of optical modular elements and groups may configure the number of levels in the multi-level amplitude modulated optical signal. Unit drivers may be coupled to each of the groups. The electrical input signals may be synchronized before communicating them to the unit drivers utilizing flip-flops. Phase addition may be synchronized utilizing one or more electrical delay lines. The optical modulator may be integrated on a single substrate, which may include one of: silicon, gallium arsenide, germanium, indium gallium arsenide, polymers, or indium phosphide. The optical modulator may include a Mach-Zehnder interferometer or one or more ring modulators.

The invention provides a laser imaging radar device and a distance measurement method thereof. The laser imaging radar device and the distance measurement method thereof aims at the problem that an existing distance range gate laser imaging radar is low in distance resolution. The laser imaging radar device comprises a laser device, a laser modulation unit, an optical antenna unit, a detecting unit, a data processing unit and an image processing unit, wherein the detecting unit is composed of a counter, a gate controller and an array detector, and the data processing unit is composed of an accumulator and a correlator. According to the distance measurement method, an information loading process is carried out on laser signals with constant amplitude by using a phase code pulse amplitude modulation mode. The laser imaging radar device and the distance measurement method thereof have the advantages that the equipment and the method combine the advantages of long detecting distances of the distance ranging gate layer imaging radar and the advantage of high distance measurement resolution of the pulse phase coding mode, and meanwhile the detect of low distance measurement resolution of the distance ranging gate layer imaging radar and the detect of low imaging speed of the pulse phase coding mode are avoided.

Multiple-level phase amplitude (M-PAM) clock and data recovery circuitry uses information from multiple phase detectors to generate one or more data sampling clocks that are optimized for each of the data slicers. One possible 4-PAM implementation includes 3 data slicers, 3 edge slicers, 3 phase detectors, and a single VCO. The phase detector outputs are combined (e.g., via weighted voting, weighted average, minimum error, and/or minimum variance) to determine an optimized phase estimate for the clock used to sample the data at all three data slicers. Another 4-PAM implementation similarly includes 3 data slicers, 3 edge slicers, 3 phase detectors, and a single VCO. The mid-amplitude edge slicer and phase detector are used in combination with the VCO to generate a central phase while a multiple-tap delay line provides N phase variants before and after the central phase. Information from the non-mid-amplitude edge slicers and phase detectors is used to choose a phase from among the phase variants that best suits the other data slicers. In yet another implementation, a single edge slicer, single phase detector, and single VCO is used to generate a key clock which is used by the edge slicer to track the symbol timing. A clock generator provides a single optimized clock (that is offset from the key clock) that is used by the data slicers. Bit error rates from the data slicers are used to adjust the offset until the data slicer clock is optimized with respect to all the slicers. Alternatively, multiple clocks are generated via offsets from the key clock, each being optimized to the data slicer group that it drives.

The invention relates to a multidimensional constellation mapping based coding and modulating method, demodulating and decoding method and system. The coding and modulating method comprises the following steps of: carrying out channel coding and bit interleaving on input information bits to obtain coded interleaved bits; carrying out K-dimensional pulse amplitude modulated constellation mapping on the coded and interleaved bits to obtain a constellation mapping symbol of a K-dimensional real-number vector, wherein K is a positive integer; carrying out constellation rotation on the constellation mapping symbol to obtain a multidimensional rotated constellation mapping symbol of the K-dimensional real-number vector; and carrying out dimension conversion and general real-number interleaving on the multidimensional rotated constellation mapping symbol to obtain a coded and modulated symbol, and outputting the coded and modulated symbol. The method and system in the invention can ensure that the performances of a coding and modulating system and a corresponding demodulating and decoding system approach the channel capacity at medium and low frequency spectrum efficiency under the AWGN (Added White Gaussian Noise) and fading channel conditions and meanwhile, the throughput of the system is taken into consideration.

Methods and apparatus to transmit and receive information bits encoded in duobinary, multilevel pulse-amplitude-modulated (PAM) optical signals are described. The transmitted optical signal has a narrow optical spectrum and a low symbol rate. Information bits are encoded in a M-ary PAM symbol sequence, where M>=2. The PAM symbol sequence is input to a finite-state machine, which yields an encoded sequence that changes sign between two symbol intervals when the encoded sequence takes on a nominally zero value during an odd number of intervening symbol intervals. The encoded sequence is lowpass filtered and modulated onto an optical electric field. The receiver processes a received optical electric field to obtain an electrical signal proportional to the received optical intensity, and performs M-ary symbol-by-symbol decisions to recover the transmitted information bits, without potential error propagation.

Decreasing the average transmitted power in an optical fiber communication channel using multilevel amplitude modulation in conjunction with Pulse Position Modulation (PPM). This multilevel PPM method does not entail any tradeoff between decreased power per channel and channel bandwidth, enabling a lower average transmitted power compared to On/Off Keying (OOK) with no reduction in aggregate data rate. Therefore, multilevel PPM can be used in high-speed Dense Wavelength Division Multiplexed (DWDM) systems where the maximum number of channels is traditionally limited by nonlinear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), four-wave mixing (FWM), stimulated Brillouin scattering (SBS), and stimulated Raman scattering (SRS). This modulation technique can enable an increased number of channels in DWDM systems, thereby increasing aggregate data rates within those systems.

In a coding system for asymmetric digital subscriber line (ADSL) communications, a method of encoding a sequence of information bits is provided comprising the steps of dividing the information bits into encoding bits and parallel bits; encoding the encoding bits to produce encoded bits; mapping the encoded bits and the parallel bits into first and second pulse amplitude modulation (PAM) signals; and generating a quadrature amplitude modulation (QAM) signal from these first and second PAM signals. This method overcomes the decoder complexity that would otherwise be required due to the large QAM constellations involved for ADSL communications.

A four-level pulse amplitude modulation receiver has a four-level pulse amplitude modulation mode and a non-return-to-zero modulation mode. First, second, and third four-level pulse amplitude modulation samplers are coupled to an input. Each of the samplers has a corresponding output in turn including a corresponding binary decision of the first, second, and third samplers. A four-level pulse amplitude modulation decoder circuit has inputs coupled to the outputs of the samplers. The four-level pulse amplitude modulation decoder circuit is active in the four-level pulse amplitude modulation mode. The receiver also includes a non-return-to-zero majority voting circuit coupled to the outputs of the samplers. The non-return-to-zero majority voting circuit has an output and is configured to output a majority decision of the corresponding binary decisions of the samplers, and is active in the non-return-to-zero modulation mode.

A direct synthesis transmitter. A very efficient and highly linear direct synthesis transmitter is provided that can be used to directly synthesize and transmit any type of modulated signal. The direct synthesis transmitter includes a phase-locked loop (PLL) with controls phase modulation plus an accompanying variable gain amplifier for amplitude modulation. Also included is a system to align the phase and amplitude modulation signals. A transmitter constructed in accordance with the present invention is very efficient and suitable for use in portable radio equipment.

The invention relates to a free space optical-communication APT system based on a compressive sensing receiver. The free space optical-communication APT system based on the compressive sensing receiver comprises an APT system body and the compressive sensing receiver, wherein the APT system body comprises an optical portion and a servo control portion. The optical portion of the APT system body comprises primary mirrors, secondary mirrors, a precise-tracking executing mechanism, a beam splitter, a pulse amplitude modulation, a first convergence light receiving unit, a light spot detecting device, an emitter and a beam expanding collimating lens. The servo control portion of the APT system body comprises a rough-tracking controller, a rough-tracking executing mechanism, a universal angle plate and a precise-tracking loop controller. The compressive sensing receiver comprises an emitter, an imaging lens, a space light modulator module, a convergence light receiving module, point detectors, an adder and an algorithm module.

A receiver generates log-likelihood-ratio-based soft bit metrics of precoded quaternary continuous phase modulation signals using four state-constrained trellises and a streamlined maximum likelihood sequence estimation Viterbi algorithm requiring no survivor state storage elements for a preferred error correction-coded quaternary Gaussian minimum shift keying communication system employing reduced-complexity pulse-amplitude modulation matched-filtering and soft-decision decoding.

The invention discloses a method of modulating a variable pulse amplitude position and improving an error rate for a visible light communication system, belonging to the field of visible light wireless communication technologies. According to the method, modulation of the variable pulse amplitude position is utilized in a modulation module of a signal transmitting end, a modulation method is multi-system modulation capable of combining pulse amplitude position modulation and pulse width modulation, transmission of communication data is guaranteed while a system dimming function is provided, improvement of the communication quality mainly includes that the transmission rate can be improved under the condition of the same symbol rates, the advantages of high multi-system modulation bandwidth efficiency and high pulse position modulation power efficiency are combined, the spectral efficiency can be effectively improved, and compared with the other multi-system modulation manner, the complexity is lower. In order to further improve the error rate of the visible light communication system, the method utilizes a channel balancer based on a feed-forward back propagation multilayer perceptron on a receiving end, so that the error rate is effectively improved, and the communication quality is further improved.

A method of activating at least two electrodes in a multichannel electrode array uses channel specific sampling sequences. More particularly, a channel specific sampling sequence is defined for each electrode, the sequence having a particular duration, pulse amplitude distribution, and number of pulses. A weighting factor is applied to the channel specific sampling sequence. Each electrode in the multichannel electrode array is then simultaneously activated using sign-correlated pulses. The sign-correlated pulses are based on parameters of spatial channel interaction reflecting geometric overlapping of electrical fields from each electrode, wherein calculating the amplitudes of the sign-correlated pulses includes compensating for geometric overlapping of electrical fields from each electrode. Furthermore, the sign-correlated pulses are based on each electrode's weighted channel specific sampling sequence.