234 results about "Linear modulation" patented technology

The present invention relates to a method of detecting the presence of a transmission signal of a transmitter in a reception signal in a wireless communication system based on CR technology. The method includes generating a frequency signal vector using a Fourier transform and a reception signal vector obtained by sampling the reception signal at a certain period, finding an eigenvalue and an eigenvector regarding a matrix, obtaining by approximating a covariance matrix of the frequency signal vector using a vectorized Fourier transform result of all channel impulse responses of the transmission signal linearly modulated, calculating a sufficient statistic on a basis of the frequency signal vector, the eigenvalue, and the eigenvector, finding a threshold which is a criterion for determining signal presence detection on a basis of a preset detection probability or a preset false alarm probability and the eigenvalue, and if the sufficient statistic is determined to be greater than the threshold, determining that the transmission signal exists.

A blind spot detector system adapted to the exterior of a vehicle comprising at least one infrared light emitting diode (LED), an infrared photodetector and demodulator, and a microcontroller. The output power of the infrared transmitter is linearly modulated, enabling the blind spot detector to determine the proximity of the detected object. Furthermore, the transmitter output is frequency modulated to screen out random infrared radiation that might adversely affect the operation of the infrared photodetector. The system is calibrated to the position of the attached vehicle by linearly increasing the output power of the transmitter until the rear quadrant of the vehicle is detected when the transmitter is outputting power at a pre-determined calibration level. During normal operation, an object detected while the transmitted power is greater than a predetermined lower threshold and less than the calibration level will activate a LED indicator on the system housing.

The invention discloses a method for phase and symbol synchronization, channel estimation and frequency domain equalization of an SC-FDE system, wherein a receiver in the method performs frame synchronization, fraction multiplication channel estimation and fraction multiplication frequency domain equalization on an over-sampling signal, and eliminates influences cause by carrier phases, multipath interferences and frame synchronization errors through the fraction multiplication channel estimation and the fraction multiplication frequency domain equalization so as to achieve the timing synchronization and the frequency domain equalization of a carrier phase and a symbol of a modulated signal. The method has the characteristics of strong anti-multipath capability, capability of estimating and equalizing a multipath channel with fraction multiplication symbol period intervals, no limitation to signal demodulation mode and signal demodulation and detection method and the like, and is especially suitable for single-carrier frequency domain equalization and synchronization of modulation (such as FQPSK modulation, SOQPSK modulation, CPM modulation and other efficient linear modulations) signals with efficient power and spectrum.

A method, and a system of mitigating interference effects under a communication environment including a first spread spectrum (SS) transmission scheme and a second spread spectrum (SS) transmission scheme in the same frequency band are proposed in this present invention. Firstly, responsive to a received signal, output number of signal of the first SS transmission scheme and the second SS transmission scheme. Secondly, retrieve the timing, phase and amplitude information of signals of the first SS transmission scheme in the received signal, and the timing, phase and amplitude information of signals of the second SS transmission scheme. Generate a plurality of linearly-modulated signals based on a predetermined manner, correlate the received signal based on the plurality of linearly-modulated signals to generate a correlated outputs. Finally, selectively produce an estimated information sequence carried by the signals of the first SS transmission scheme and the signals of the second SS transmission scheme based on the correlated outputs in another predetermined manner. Such a method and a system not only extend the ability of conventional linear multi-user detection to the FH-CDMA (frequency hopping code division multiple access) and the DS-FH-CDMA (direct sequence and frequency hopping code division multiple access) multi-user communications systems, but also remove the limitations of the conventional linear multi-user detection on linearly modulated signals. In addition, the multi-user synchronizers proposed in this invention, which estimate the received timings, phases, and amplitudes of the interfering and the desired spread spectrum signals with feasible complexity, further complete the interference suppression communications system. This invention is applicable to various environments. For example: the source of DSSS signals could be derived from the IEEE 802.11b devices or perhaps the IEEE 802.15.3 devices; the source of FHSS signals could be derived from the IEEE 802.15.1 (Bluetooth) devices or the HomeRF devices. Moreover, this invention is not limited to the wireless communications as it is equally applicable to the optical communications systems (e.g. the HFC (hybrid-fiber-coax) networks) and the wired communications systems.

The invention discloses a super-surface color vector complex amplitude holographic element, which comprises a bimetallic nanorod unit structure with adjustable in-plane rotation angles and in-plane displacement, wherein an aluminum-silicon dioxide-aluminum super-structure grating structure generates a polarization-selective type diffraction efficiency enhancement effect in a visible light range; asum of in-plane displacement of two metal nanorods in the unit structure and diffraction phase information are in a linear modulation relationship, a difference between the rotation angles of the twometal nanorods and a diffraction light amplitude are in a sinusoidal modulation relationship, and a sum of the rotation angles of the two metal nanorods and a diffraction light polarization directionare in a linear modulation relationship; and a color holographic method is implemented on diffraction level by utilizing the phase displacement based on inherent dispersion of the super-structure grating. The super-surface color vector complex amplitude holographic element disclosed by the invention has the advantages of low requirements for preparation control precision, simple structure, high degree of control freedom and the like, and has powerful functions of simultaneously controlling four parameters of light wave phase, polarization, amplitude and frequency.

Certain aspects of the present disclosure relate to a method for demodulating CPM modulated signals transmitted in a wired or wireless communication system using a linear modulation model consisting of a linear superposition of time pulses modulated using pseudo-PSK pulses.

A analog / digital modulation type discrimination circuit 1 discriminates whether a reception signal is an analog modulation type, a linear modulation type or a non-linear modulation type by digital modulation type. In case where the reception signal is discriminated to be the analog modulation type, an analog modulation type discrimination circuit 2 discriminates whether it is an AM signal or an FM signal among the analog modulation type. In case where the reception signal is discriminated to be the linear modulation type by digital modulation type, a linear modulation type discrimination circuit 3 discriminates whether it is a BPSK signal, a QPSK signal, a π / 4-shift QPSK signal, an 8-PSK signal, an M-ary PSK signal of multi-level exceeding 8-levels, a 16 QAM signal or a n M-ary QAM signal of multi-level exceeding 16-levels among the linear modulation type by digital modulation type. In case where the reception signal is discriminated to be the non-linear modulation type by the digital modulation type a non-linear modulation type discrimination circuit 4 discriminates whether it is an M-ary FSK signal, a 2-FSK signal, an MSK signal or a GMSK signal among the non-linear modulation type by the digital modulation type.

A multiband and multimode transmitter circuit (200) includes two separate oscillators, such as at least a first oscillator circuit (60), a second oscillator circuit (62), a corresponding first signal processing circuit (64), and second signal processing circuit (66) to produce a first output frequency signal (78) defined within the first or second band of frequencies in response to a transmitter input signal (46). Each oscillator and corresponding signal processing circuit (64, 66) may be optimized for the lowest power consumption while meeting the noise performance criteria in each of the multiple frequency bands. The multiband and multimode transmitter circuit (200) may produce the transmitter output signal (36) with either linear modulation or nonlinear modulation and at a first band or second band frequencies.

A high frequency linear modulation radar direction measurement method, characterized by: in the radar far-field, emitting single-frequency continuous sinusoidal signal as a measurement beacon, and the beacon carrying platform uses radar for the center to move for directional scanning; processing time-frequency analysis to the echo received by each radar antenna, to obtain the transient response value of each antenna, and corresponding with the beacons of instantaneous position, which is the antenna direction map. The invention uses a simple single-frequency signal transmission to achieve the measurement and calibration of the direction map, and compared with the traditional transponders measurement method, it greatly reduces system complexity and measurement cost, with inexpensive way to improve the effectiveness of the direction map measurement.

The invention discloses a displacement coding type metasurface vector holographic element capable of realizing a novel anti-counterfeit technology. The metasurface vector holographic element comprisesultra-structure molecular structures of two mutually-perpendicular metal nanorods forming a metasurface; polarization selective diffraction efficiency enhancement effect generated by a metal-medium-metal sandwich structure is achieved; a linear modulation mode of a polarization state phase through local displacement between the two perpendicular metal nanorods in each ultra-structure molecule, alinear modulation mode of a wave-front total phase through global displacement between adjacent ultra-structure molecules and a linear modulation mode of a polarization state amplitude proportion through rotating angles of the metal nanorods are realized. The displacement coding type metasurface vector holographic element has advantages of low preparation control accuracy requirement, simple structure, wide incidence angle, wide operating frequency band, freeness of dispersion and the like, regulation of wavefront in any forms of phases and polarization state spatial distribution can be realized, and the security level of holographic anti-counterfeit and encryption technologies is raised greatly.

A modulation system and method having a high linearity. The system is a PWM modulator or a class D amplifier and includes an integrator, a low pass filter (LPF), a comparator, and an output circuit. The LPF is located before the comparator. Jitter noise produced by the comparator and / or switching noise of the output circuit are removed by feedback to the input. Thus, the linearity of the modulation system is provided.

The invention provides a modulation method applied to a cascade converter, which comprises the following steps: obtaining a linear modulation region, a first over-modulation region and a second over-modulation region according to the direct current voltage value, the control command reference voltage vector and the power unit number of each phase of a bridge voltage source type power unit; and setting Edc as the direct current voltage value of the bridge voltage source type power unit, V<*> as the control command reference voltage vector, and n as the power unit number of each phase so that the modulation ratio m is equal to (pi|V<*> / 2n|) / 2Edc, wherein the interval that m is more than or equal to 0 and less than or equal to 0.906 is the linear modulation region, the interval that m is more than or equal to 0.906 and less than or equal to 0.951 is the first over-modulation region, and the interval that m is more than or equal to 0.951 and less than or equal to 1 is the second over-modulation region. The modulation method can simplify the judgment time of the vector areas.

The invention discloses a two-level three-phase space vector pulse-width modulation device and an SVPWM optimization method thereof. Aiming at influence of dead-zone time and narrow pulse-width limit, a practical linear modulation zone is expanded, an over-modulation algorithm is optimized and linear processing of an over-modulation zone is simply realized. The two-level three-phase space vector pulse-width modulation device comprises six modules of a given reference voltage correction module, a voltage coordinate transformation module, a voltage interval calculating module, a vector time calculating module, a modulation algorithm optimization module and a PWM comparison point time calculating module. Bus voltage is fully utilized via the simplest algorithm so that linearity of output fundamental wave voltage is enhanced and total harmonic wave distortion of the output voltage is reduced.

The invention discloses a dual-mode SVPWM overmodulation method. The method comprises the steps that a modulation area is divided into a linear modulation area, a first overmodulation area and a second overmodulation area according to a modulation factor, wherein when an MI is larger than 0 and smaller than 0.9069, it is the linear modulation area, when the MI is larger than 0.9069 and smaller than or equal to 0.9517, it is the first overmodulation area, when the MI is larger than 0.9517 and smaller than or equal to 1, it is the second overmodulation area, and the MI is the modulation factor; a traditional SVPWM modulation method is used in the linear modulation area; a reference angle is used for controlling the compensation of an actual output voltage vector in the first overmodulation area; the mode that the actual output voltage vector hops at the position where a phase angle is a keep angle is used in the second overmodulation area, and the mode that an expected output voltage vector is followed by hopping is used for controlling the track of the output voltage vector. Compared with a traditional dual-mode control method, the dual-mode SVPWM overmodulation method is simple in algorithm, avoids complex operations, and is prone to engineering realization. Meanwhile, compared with a single-mode control method, the dual-mode SVPWM overmodulation method is high in control precision, and good in output voltage continuity.

The invention relates to a comprehensive vector modulation method of a three-phase diode clamping three-level converter. The comprehensive vector modulation method comprises the following steps of: judging a sector where an output vector is, then judging whether the current output vector is in a linear modulation region or an overmodulation region, and calculating the duty ratio of an IGBT (Insulated Gate Bipolar Transistor) of each phase of bridge arm according to a conventional SVPWM (Space Vector Pulse Width Modulation) method or a virtual vector synthesis SVPWM method in the linear modulation region; and in the overmodulation region, calculating the duty ratios of large vectors and medium vectors according to an overmodulation algorithm, decomposing the medium vector according to the following principles: even if the action time of one medium vector is equal to the sum of one third of respective total action time of two large vectors adjacent to the one medium vector plus one third of the total action time of the medium vector, and finally calculating the duty ratio of the IGBT of each phase of bridge arm. The comprehensive vector modulation method disclosed by the invention can not only realize overmodulation of an NPC (Neutral Point Clamping) three-level converter by virtue of three-level output and also can furthest restrict larger offset and larger fluctuation of DC neutral-point voltage caused by overmodulation.

The present invention discloses a radar interference identification method with distance and speed simultaneous pull-off. The method comprises a step of establishing a radar interference signal model with interferometer transmitting distance and speed simultaneous pull-off, wherein, a target carries the interferometer, and the real target echo signal received by a radar is obtained; a step of setting an interferometer input signal, receiving a wideband linear modulation signal by the interferometer, calculating the distance-speed simultaneous pull-off interference signal outputted by the interferometer, and calculating a distance-speed simultaneous pull-off interference signal with phase quantization, a step of setting the echo signal received by a target and an echo signal received by the radar and obtaining real target echo baseband signal or a distance-speed simultaneous pull-off baseband interference signal with phase quantization, and a step of orderly setting a characteristic interference signal error angle and the category of the echo baseband signal received by the radar and thus identifying the interference signal or a target signal.

A method and a device for compensating a data-dependency of a power measurement caused by linear modulation is described. The method comprises performing a first measurement (160) of a transmitted output power and performing a second measurement (160) of a reflected power, wherein the second measurement is performed time multiplexed from said first measurement. The method further comprises calculating (171) a first average power based on data transmitted during the first measurement, calculating a second average power based on data transmitted during the second measurement, and compensating (171) at least one of the first measurement and second measurement based on a difference between the first average power and the second average power.

The invention discloses an ultra wide band microwave photon long-distance range radar device based on chaos laser. The ultra wide band microwave photon long-distance range radar device based on chaos laser is characterized in that an ultra wide band chaos signal is used as a radar detection signal; the radar detection signal is transmitted via a long single mode fiber, is converted into a corresponding electric signal at a long-distance antenna terminal and is transmitted via an ultra wide band antenna; a detection signal is received by the ultra wide band antenna of the same model after being reflected when meeting a space target part; the laser is subjected to linear modulation, the signal is converted into a corresponding optical signal and is then transmitted via the single mode fiber to return to a center station; data processing is carried out in the data processing center to obtain and display target distance information; and therefore, the space precise positioning of the long-distance target is realized. The ultra wide band microwave photon long-distance range radar device based on the chaos laser is used for monitoring the military radar, the radar system on the mountain top and the island with severe environment and the industrial areas with severe or dangerous environment in real time.

The invention discloses a micro-crack nondestructive detection system and a detection method thereof. The micro-crack nondestructive detection system comprises a signal generator, a low frequency vibration exciter, a high frequency exciter, a detected member, a piezoelectric sensor, a preamplifier and a signal acquisition and analysis system; the signal generator is electrically connected with the detected member through the low frequency vibration exciter and the high frequency exciter, the piezoelectric sensor is fixed on the detected member through an adhesive, and the signal acquisition and analysis system is electrically connected with the piezoelectric sensor through the preamplifier; and the signal-generator can simultaneously output two paths of simple harmonic excitation signals with different frequencies. Defect detection is carried out by using the non-linear modulation effect of a crack structure under multi-frequency excitation, and whether the existence or not of the micro-crack and the micro-crack damage of the detected member are directly determined according to the quantity and amplitude of side frequencies in a response spectrum without complex signal processing, so the system and the method have the advantages of use convenience, sensitive detection and high detection efficiency.

A method is disclosed for tracking the phase of a received phase-modulated carrier carrying a sequence of symbols represented by phase jumps in a low signal-to-noise ratio environment. An input sequence of symbols stored in a delay line. The phase of a current symbol in a phase locked loop, and the phase error detected in the phase locked loop is updated to take into account phase error estimates of future symbols.

The invention provides a water sound frequency hopping communication method for linear modulation signal modulation and demodulation, and relates to a water sound frequency hopping communication. The water sound frequency hopping communication method comprises the following steps: carrying out source encoding on original information so as to obtain compressed digital signals; carrying out channel coding; using data obtained by the channel coding as a linear modulation signal control code; controlling to generate a linear modulation signal according to a frequency hopping sequence as a carrier for modulation, so as to obtain modulation signals; carrying out D / A (Digital / Analogue) conversion and power amplification on the modulation signals; converting the modulated signals into sound waves to spread in an ocean underwater acoustic channel through a transmission energy converter; receiving and converting acoustic signals spreading in the ocean underwater acoustic channel into electric signals through the receiving energy converter; obtaining stimulation signals through front amplification and band-pass filtering; carrying out A / D (Analogue / Digital) conversion on the received stimulation signals; after detecting that the digital signals after the A / D conversion are synchronous, carrying out linear modulation signal demodulation center frequency and demodulation frequency to obtain demodulation data; and carrying out channel decoding on the demodulation data; and carrying out source decoding on the digital signals to obtain information.

The invention relates to an optical generation device and method for a phase coding signal with a tunable multiplication factor. The device comprises a laser, a DP-QPSK modulator, a microwave signal generator, an electric amplifier, a coding signal generator, a direct current power, a polarization controller, a polarizer, an optical amplifier, and a photo detector. The method comprises the step ofgenerating binary phase coding signals with different multiplication factors according to needs by using a non-linear modulation characteristic of the DP-QPSK modulator, wherein the multiplication factors can be any one of one to four, and the frequencies of the generated signals are tuned by adjusting the frequency of an input microwave signal. The device is based on an integrated modulator structure, has a simple system, has stable performance, overcomes defects that a traditional manner of generating a pulse compression signal in the frequency domain is limited by the rate and bandwidth ofan electronic device, has difficulty in generating a high-frequency signal or cannot generate the high-frequency signal and the generated signal cannot be tuned flexibly in frequency, greatly improves the frequency of generating the phase coding signal, and can produce phase coding signals with very large frequency tuning range.

The invention discloses a method for inhibiting cross terms in the time-frequency distribution of multi-component linear frequency modulation (LFM) signals based on subspace decomposition, which belongs to the technical field of signal processing. In the method, a time-frequency distribution matrix comprising noises and the cross terms is decomposed into signal subspaces and noise subspaces by utilizing singular value decomposition (SVD)-based subspace decomposition. For the problem that the linear modulation signals occupy relatively more bandwidths to make singular values are reduced at relatively lower rates and cannot be separated from the noises effectively, an angle of inclination of the time-frequency distribution of the signals can be obtained by utilizing Wigner-Hough transform. The time-frequency distribution of the signals is rotated according to the obtained angle so as to be parallel to a time base. The method is characterized in that: the singular values are rapidly decreased to zero, and then the signal sub-spaces can be separated effectively. By the method, the cross terms and the noises in the time-frequency distribution of the multi-component LFM signals are inhibited without reducing time-frequency resolution; therefore, the method is vast in application prospect.

The invention discloses an overmodulation method implemented based on a carrier. The method includes determining a three-phase original modulated wave U1i according to amplitude and phase of a reference vector in an overmodulation area; superposing a zero-sequence component V0 to the original modulated wave to acquire corresponding three-phase saddle modulated waves U2i, and sorting the three-phase saddle modulated waves U2i; in the overmodulation area, judging whether or not the reference vector is positioned in a linear modulation section, a hexagonal modulation section or a six-pulse wave modulation section according to the magnitude relationship between Umax and 2-|Umid|; correcting the three-phase saddle modulated waves in different modulation sections respectively to acquire a final three-phase modulated wave Ui; comparing the Ui with the triangular carrier to generate PWM (pulse-width modulation) waves, and distributing the PWM waves to corresponding pins. The overmodulation method has the advantages that sector division and vector action time calculation are not needed, so that the overmodulation method is simple to implement, easy to apply to engineering and applicable to overmodulation of any level number converters; accuracy of the overmodulation method is proved by simulation results.

An optical duobinary transmitter. The transmitter uses a half-rate precoder, half-rate non-linear modulation drive circuits and a multiplex modulator for generating duobinary modulation on an optical signal from which full-rate data can be detected without decoding. The intensity of the optical signal is modulated to be zero between data symbols.

A transmitter includes a dual mode modulator and an amplifier coupled to the dual mode modulator. The dual mode modulator implements a linear modulation scheme during a first mode of the modulator to produce a variable envelope modulated signal. The dual mode modulator implements a non-linear modulation scheme during a second mode of the modulator to produce a constant envelope modulated signal. The amplifier is biased as a linear amplifier during the first mode of the modulator and is biased as a non-linear amplifier during the second mode of the modulator. A feed-forward connection between the dual mode modulator and the amplifier is used to indicate a change in modulation mode and to adjust the bias of the amplifier. A power of the constant envelope modulated signal is increased such that an operating point of the amplifier remains substantially constant during the first and second modes of the modulator.

A digital control apparatus for a switching DC-DC converter includes at least one power transistor and is able to provide a regulated output voltage on a load. The apparatus includes digital control having a reference digital input signal and provides a modulating signal to a PWM device to which is input the modulating signal and which provides an output square wave signal for driving the power transistor of the DC-DC converter such that there is non-linear modulation only when the value of a signal on the load is lower or higher than a prefixed value range.

A signal processing system includes a jointly non-linear delta sigma modulator. In one embodiment, the jointly non-linear delta sigma modulator includes a non-linear quantization transfer function, and the output of the delta sigma modulator is defined, at least in part, by a non-linear interrelationship of multiple noise-shaping filter state variables. A look-ahead delta-sigma modulator can be implemented as a noise shaping filter and a function generator. State variables of the noise shaping filter provide the input data from which the function generator determines a quantizer output signal. Latter state variables are more dominant in determining the quantizer output signal. Accordingly, earlier state variables can be approximated to a greater degree than latter state variables without significant compromise in quantization accuracy.