687 results about "Differential phase" patented technology

A method and apparatus for performing time synchronization and an OFDMA receiver thereof are provided. The method preferably includes performing a differential phase correlation in a frequency domain based on one received sequence and one reference preamble and detecting an integer frequency offset based on a result of the differential phase correlation. The method and apparatus advantageously enable the use of one OFDM symbol to estimate ICFO and the use of a simple method to facilitate ICFO detection. Moreover, the performance of the integer frequency offset estimation becomes more robust in high noise and time-variant fading channels, with reduced hardware complexity.

A long baseline interferometer antenna system and method for determining the location of an emitter. The long baseline interferometer antenna system comprises a first antenna, a second antenna, an inertial navigation system, an antenna baseline measurement system, a multi-channel receiver and a processor. The first and second antenna elements are positioned on a platform and are both configured to receive signals from the emitter. The first and second antenna elements form a long baseline antenna pair. The inertial navigation system measures the platform position and attitude; and the antenna baseline measurement system measures the antenna baseline vector between the first and second antenna elements. The multi-channel receiver measures the differential phase between antenna pairs, and the processor computes the emitter location. Additional antenna elements can be included and some can be configured as squinted beam pair and make use of amplitude difference of arrival measurements.

A burst-mode differential phase shift keying (DPSK) communications system according to an embodiment of the present invention enables practical, power-efficient, multi-rate communications between an optical transmitter and receiver. An embodiment of the system utilizes a single interferometer in the receiver with a relative path delay that is matched to the DPSK symbol rate of the link. DPSK symbols are transmitted in bursts, and the data rate may be varied by changing the ratio of the burst-on time to the burst-off time. This approach offers a number of advantages over conventional DPSK implementations, including near-optimum photon efficiency over a wide range of data rates, simplified multi-rate transceiver implementation, and relaxed transmit laser line-width requirements at low data rates.

An integrated rainfall calculation method using X-band dual-polarimetric radar measurement data includes a precipitation classification step of classifying hydrometeors into four types of snow, rain/snow, rain and non-meteorological target through a fuzzy logic technique using a correlation coefficient (cross correlation coefficient, ρ_hv), features of a measured differential propagation phase (Ψ_dp(r)) or differential propagation phase (φ_dp) and a signal-to-noise ratio (SNR) as input variables (input feature vector); a specific differential phase calculation step of separately calculating a specific differential phase by applying a specific differential phase using a total difference of differential phase and signal-attenuation corrected reflectivity for the rain among the classified hydrometeors and applying a specific differential phase calculated using a filtering method for the other hydrometeors; and a rainfall calculation step of calculating rainfall by using a relation between the specific differential phase and the rainfall and using the separately calculated specific differential phase.

A line phase identification system and method identifies the phase of a power line at a remote unknown-phase line (160) in a three-phase power distribution network (100). The instantaneous phase of a known-phase line (150) is measured and saved each GPS second using a 1-pps time mark of a GPS receiver (660). The instantaneous phase at the unknown-phase line (160) is measured at a single GPS second using the 1-pps time mark of a GPS receiver (660) and compared to the phase measurement taken from the known-phase line (150) at the same GPS second. The differential phase between these simultaneously taken known and unknown instantaneous phases will be close to either 0, +120, or −120 degrees, thus identifying the line phase at the line under test (160).

The invention provides a time sequence InSAR (Interferometric Synthetic Aperture Radar) deformation monitoring method and a device based on a polynomial inversion model. The method comprises the following steps of: combining N SAR (Synthetic Aperture Radar) single look complexes of a certain region to generate M interference pictures and generate M differential phase pictures; calculating an average coherent coefficient picture and extracting high coherent points; establishing a polynomial inversion model by carrying out difference again on a differential phase of the two adjacent high coherent points; solving relative polynomial deformation and a relative elevation error of the adjacent points respectively integrating by taking a certain high coherent point provided with known deformation amount and a DEM (Dynamic Effect Model) error as a reference point to obtain the polynomial deformation and the elevation error of each high coherent point; after a phase of the polynomial inversion model is obtained, subtracting the phase of the polynomial inversion model from the differential phase of the high coherent points to obtain a residual phase; and extracting residual deformation from the differential phase to be overlapped with the polynomial deformation to obtain ground surface deformation information of the high coherent points. The method provides a solution for highly-precisely monitoring the ground surface deformation.

The invention discloses a frequency offset and phase estimation method based on differential phase in TD-SCDMA communication system receiving synchronization; the invention uses fractional step estimation strategy of two periods of initial frequency offset estimation and precise frequency offset and phase estimation, combines and uses two groups of pilot frequency identifier sequences in present adjacent two sub-frames having related frequency offset, implements TD-SCDMA communication system frequency offset and phase estimation through differential phase calculation. The method has precise frequency offset and phase estimation under middle and high signal-to-noise ratio; fluctuation range of estimated value is less.

A method and an apparatus relating to an OFDM data communications system where the sub-carriers are modulated using differential quadrature phase-shift keying (DQPSK). The multi-carrier transmitted signal is directly generated by means of summation of pre-computed sample points. As part of the multi-carrier signal generation, a signal for the guard interval is established. In an acoustic application of this approach, direct radiation of the sub-carrier approach is facilitated. Symbol synchronization in the receiver is based on signal correlation with the missed sub-carrier. Separation of the sub-carriers in the receiver by means of correlation of the received signal and reference signals that are derived from a table of pre-computed values. Optimal non-coherent processing of the sub-carriers without any phase tracking procedures is achieved.

An optical receiving apparatus sets, efficiently and optimally, a delay interferometer and a variable wavelength dispersion compensator in the apparatus. The apparatus has a variable dispersion compensation unit performing variably dispersion compensation on a received optical signal, a delay interference unit performing a delay interference process on the optical signal from the variable dispersion compensation unit, a photoelectric conversion detecting unit performing photoelectric conversion detection on the optical signal from the delay interference unit and outputting an electric signal demodulated from the differential M-ary phase modulated optical signal, a clock signal extracting unit extracting a clock signal from the demodulated electric signal fed from the photoelectric conversion detecting unit, and a dispersion compensation controlling unit controlling a dispersion compensation amount in the variable dispersion compensation unit on the basis of the clock signal extracted by the clock signal extracting unit.

An efficient system and method for modulation and demodulation to achieve a high data rate using Bit-Interleaved Coded Modulation and OFDM uses either a coherent or a non-coherent transmission scheme using differential modulation. In order to maintain a high data rate impervious to sudden phase changes, a communication system uses an efficient constellation having multiple rings with different sizes and modulation/demodulation schemes utilizing this constellation. In power line communications, the channel gain information is obtained easily at a receiver (100) while the phase information is not. Thus, the communication system uses an absolute magnitude and differential phase coding for modulation and demodulation of the signals.

An optical communication system (100; 2300) comprises at least a transmitter (110) apt to emit a differential phase shift keying (DPSK) optical signal having a bit-rate equal to R, at least a receiving system (1200) for receiving the differential phase shift keying optical signal; and an optical link (130) optically connecting the transmitter and the receiving system for transmitting the DPSK optical signal from the transmitter to the receiving system, wherein the receiving system comprises a coherent optical receiving device (1205) apt to coherently receive the propagated DPSK optical signal and to emit at least one electrical signal (I) related to the received DPSK optical signal, and wherein the receiving system further comprises at least one electrical filter (270) for filtering the at least one electrical signal and having −3 dB double-side bandwidth greater than or equal to 0.44 R and lower than or equal to 0.68 R, and at least one squarer (280) for squaring the at least one filtered electrical signal. A related method for optical communication is also disclosed.

A duo-binary optical transmitter tolerant to a chromatic dispersion includes a pre-coder for generating a first 2-level signal from input binary data and generating a second signal having a waveform obtained by inverting the first signal, a Mach-Zehnder Modulator (MZM) for generating a Differential Phase Shift Keying (DPSK) modulated optical signal by modulating an input light according to the first signal and the second signal, and a Delay Interferometer (DI) for splitting the DPSK modulated optical signal into a first split signal and a second split signal, delaying the second split signal, and generating a duo-binary optical signal by interfering the first split signal with the second delayed split signal, wherein a time required for delaying the second split signal is set to 0.5˜0.8 bit.

The invention relates to a carrier phase height measurement device based on a GNSS-R technology and a method thereof. The device comprises a GNSS-R receiving module, a direct signal processing module, a reflected signal processing module and a reflected signal carrier phase height measurement module, wherein the reflected signal carrier phase height measurement module comprises an open-loop tracking unit and a time differential phase height measurement unit; the open-loop tracking unit takes the direct signal tracking frequency as the local reference frequency so as to effectively track the GNSS reflected signal and obtain the reflected signal carrier phase observed quantity; and the time differential phase height measurement unit utilizes the single-frequency reflected signal phase observed quantity obtained by the open-loop tracking unit to invert accurate water level in a time differential phase height measurement method. The height measurement method accurately measures the water level by the GNSS water surface reflected signal carrier phase, and effective reflected signal phase observed quantity can be obtained by open-loop tracking. A time differential phase height measurement algorithm is simple and can realize high-accuracy height measurement of the water level within a short time.

The invention relates to a full duplex cat eye reverse modulation recovery free space laser communication system, belongs to the technical field of wireless communication, and solves the problem of low transmission rate of the system in the prior art. A laser I and a transmitting data source are both connected with a DPSK (differential phase shift keying) modulator, the DPSK modulator and a laser II are both connected with an optical fiber amplifier I, two communication lights are amplified and then connected with a port a of a fiber circulator, a port b of the fiber circulator is connected with an optical antenna, a port c of the fiber circulator is connected with a photoelectric detector I, the photoelectric detector I is connected with a DPSK modulator I, a cat eye optical system is coaxially arranged with the optical antenna, an optical filtering beam splitter is arranged between the cat eye optical system and a laser collimating lens and forms an angle of 45 degrees with the cat eye optical system, the laser collimating lens is connected with a port d of a fiber circulator II, a port e of the fiber circulator II, an optical fiber amplifier II and the DPSK modulator II are sequentially connected, the other end of the DPSK modulator is connected with a port f of the fiber circulator II, and a photoelectric detector II is connected with the DPSK modulator.

A buoyant wave energy device is disclosed that incorporates an open-bottomed tube of substantial length in which is partially enclosed a first body of water that oscillates in response to wave action. The device incorporates a buoy to which an upper end of the tube is connected and inside of which is trapped a second body of water of substantial mass. A differential phase in the oscillations of the water trapped in the tube, and the oscillations of the buoy of augmented mass, result in the periodic compression of a pocket of air trapped at the top of the tube, and in the subsequent expulsion of pressurized air through a turbine, thereby generating electrical power.

A method includes converting a received time domain digital signal to a corresponding frequency domain digital signal, calculating phase angles of tones of at least one symbol of the frequency domain digital signal when a symbol timing offset exists, and calculating at least one differential phase offset (DPO). A DPO is the difference between two consecutive gaps, a gap being the difference between the phase angle of a tone of the symbol of the frequency domain digital signal when the timing offset of the symbol exists and a correct phase angle of the tone of the symbol of the frequency domain digital signal. The method estimates the symbol timing offset with at least one DPO.

A system and method for data communication over a cellular communications network that allows the transmission of digital data over a voice channel using a vocoder that operates in different modes depending upon characteristics of the inputted signal it receives. To prepare the digital data for transmission, one or more carrier signals are encoded with the digital data using one of a number of modulation schemes that utilize differential phase shift keying to give the modulated carrier signal certain periodicity and energy characteristics that allow it to be transmitted by the vocoder at full rate. The modulation schemes include DPSK using either a single or multiple frequency carriers, combined FSK-DPSK modulation, combined ASK-DPSK, PSK with a phase tracker in the demodulator, as well as continuous signal modulation (ASK or FSK) with inserted discontinuities that can be independent of the digital data.

An optical device includes an interferometer for a received optical differential phase shift keying DPSK signal, and an equalizer integrated with the interferometer in a manner for reducing from optical filtering effects an interference by signal bits of the DPSK signal with signal bits of a contiguous DPSK signal. The interferometer is a Michelson delay interferometer type, but can also be a Mach-Zehnder delay interferometer type on fiber, waveguide or other optical structure. The equalizer is a Fabry-Perot type equalizer, but can be a ring resonator type or a fiber based equalizer.

Data is transmitted between a central office and customer premises by a wavelength division multiplex passive optical network. Two laser beams with separate wavelengths are transmitted from the central office to an optical network unit in the customer premises. Both laser beams carry downstream data. One laser beam is intensity modulated by on/off keying. The other laser beam is phase modulated by differential phase shift keying, which maintains a constant optical intensity. The first laser beam is received by a first optical receiver, which demodulates the first downstream data. The second laser beam is split in two. One laser beam is sent to a second optical receiver, which demodulates the second downstream data. The other laser beam is sent to a reflective semiconductor amplifier, which modulates the beam with upstream data and transmits the beam back to a receiver in the central optical system.