34 results about "Quaternary phase shift keying" patented technology

Disclosed is a unique system and method for recognizing the type of modulation embedded in an unknown complex baseband signal, comprising a receiver section for extracting the complex baseband signal from a modulated signal having a carrier frequency, and comprising an orderly series of signal processing functions for (a) estimating the bandwidth of the unknown signal, (b) removing the out-of-band noise and correcting gross carrier frequency errors, (c) discriminating between constant envelope and irregular envelope signals, (d) estimating and correcting residual carrier frequency errors, (e) classifying a constant envelope signal into one of the following modulation formats: {Continuous Wave (CW), Frequency Modulation (FM), Frequency Shift Keying (FSK)}, and (f) classifying an irregular envelope signal into one of the following modulation formats: {Amplitude Modulation (AM), Double Sideband Suppressed Carrier (DSB-SC), Binary Shift Keying (BPSK), Quaternary Phase Shift Keying (QPSK), π / 4-shifted QPSK, M-ary PSK (MPSK), and OTHER classes}.

A method and apparatus for providing an asymmetrical backwards compatible communications signal that is capable of being decoded by QPSK and OQPSK receivers as well as PSK and QAM receivers is provided. The invention comprises a timing error accumulator coupled to a first bit stream. The first bit stream includes content that is common to the QPSK / OQPSK receiver and to the PSK / QAM receiver. A phase error accumulator is coupled to a second bit stream and adjusts the phase of symbols in the second bit stream. A phase and timing error compensator is coupled to the phase error accumulator and the timing error accumulator and adjusts the first and second bit streams received from the phase error accumulator and the timing error accumulator in order to reduce timing and phase errors. A higher order modulator coupled to the phase- and timing error compensator is also provided. The higher order modulator processes the first and second bit streams to provide the asymmetrical backwards compatible signal.

The invention discloses a method for recognizing a satellite communication signal modulation way. According to the scheme, the method comprises the following steps: 1, filtering a received signal to obtain a signal to be recognized; performing power spectrum smoothening, carrier frequency estimation and coherent demodulation on the signal to be recognized to obtain a demodulated signal; 3, estimating the code element rate of the demodulated signal; 4, determining whether the received signal is a binary phase shift keying signal or not by using a square spectrum; 5, determining whether the received signal is a quaternary phase shift keying signal or a hexadecimal quadrature amplitude modulation signal by using a signal quartic spectrum, carrier frequency and the code element rate; 6, determining whether the received signal is an octonary phase shift keying signal or not by using a signal eightfold spectrum; and 7, determining whether the received signal is a hexadecimal amplitude phase shift keying signal or not by using a signal duodenary spectrum, the carrier frequency and the code element rate. The method has high recognition accuracy, and can be applied to real-time monitoring of satellite communication signals. Through adoption of the method, totally-blind real-time recognition of the satellite communication signal modulation way can be realized.

Said invention is based on a transmitter of M-ary parallel communication mode, which is characterized by combining M-ary modulation mode with traditional binary phase shift keying, quaternary phase shift keying and quadrature amplitude modulation, dividing data stream into multiplex parallel modulation, in each path, part of data is modulated by M-ary mode and part of data is modulated by traditional modulation mode, using quasi-orthogonal code character to construct as more as possible quasi-orthogonal code character, making optimal grouping, to raise demodulation property.

The present invention is applicable to the field of optical communication, and provides a method and a device for locking a differential quadrature-phase shift keying demodulator, the method comprising: acquiring an optical differential quadrature-phase shift keying signal, and acquiring the optical differential quadrature the frequency of the shift keying signal when there is no perturbation signal; according to the frequency of the optical differential quadrature shift keying signal when there is no perturbation signal, determine whether the optical differential quadrature shift keying signal contains a polarization interference signal; if it contains , then obtain the frequency of the polarization interference signal; set the frequency of the disturbance signal to a frequency different from the frequency of the polarization interference signal; load the set disturbance signal into the optical differential four-phase shift key control signal. In the embodiment of the present invention, the frequency of the optical DPQSK when there is no disturbance signal is obtained, and the frequency of the disturbance signal is set to be different from the frequency of the polarization disturbance signal, so that the frequency of the disturbance signal avoids the frequency of the polarization disturbance signal, and the locking of the wavelength of the optical DPQSK is realized. .

The invention discloses a phase judgment method used for differential quaternary phase shift keying (DQPSK) demodulation. The method comprises the following steps: a) determining a fixed value n according to a signal frequency Fz and an AD sampling frequency Fs of a DQPSK modulation signal; b) judging a phase area in which a phase difference (DP) of each of AD sampling points and a corresponding adjacent sampling point is positioned, wherein (n-1) sampling points are between each of the AD sampling points and the corresponding adjacent sampling point; c) counting the number of continuous AD sampling points positioned in the same phase area as the DP between the AD sampling points and the corresponding adjacent sampling points; and d) judging a signal phase change corresponding to the counting according to the number of the AD sampling points counted each time and performing modification on the next phase. The phase judgment method used for the DQPSK demodulation provided by the invention has a very good effect in near instantaneous companded audio multiplex modulation, greatly reduces bit error rate, highly effectively restores the phase shift information before demodulating and ensures the fluency of near instantaneous companded audio multiplex decoding.

The invention provides a remote underwater acoustic communication method based on soft-demodulation soft-decoding joint iteration. The method comprises the following steps that: a transmitting end performs low density parity check (LDPC) coding on a binary information sequence which is sent by a signal source, performs quaternary phase shift keying (QPSK) modulation and Gray mapping, maps code elements to one of four positions in a constellation diagram by taking two code elements as a group, performs Walsh-m composite sequence spectrum spreading to obtain a signal to be transmitted, and converts a digital signal to be transmitted into an underwater acoustic signal; and an underwater acoustic transducer at a receiving end converts the received underwater acoustic signal, de-spreads by using a composite sequence which is the same as that of the transmitting end to obtain a receiving signal, performs self-adaptation decision feedback equalization to obtain an amplitude fading complex signal, performs soft-demodulation soft-decoding joint iteration on the signal, stops joint iteration after set iteration frequency is reached, performs belief propagation (BP) decoding on an LDPC decoder and outputs a bit value to a sink. By the method provided by the invention, the reliability of remote underwater acoustic communication is improved. The method is applicable to the remote underwater acoustic communication.

The present invention provides a quaternary phase shift keying signal spectrum estimation method for estimating the spectral parameter of the phase modulation signal of the quaternary phase shift keying of a complex electromagnetic space based on the mode of fast Fourier transform spectral fitting. The method comprises a step of carrying out dephasing modulation processing on a quaternary phase shift keying signal, a step of carrying out spectral line fitting weakening barrier effect on the quaternary phase shift keying signal which is subjected to the dephasing modulation processing, a step of accurately estimating the spectrum combined with the mode of spectrum complex coefficient decoherence so as to obtain a spectrum estimation result, and a step of using a threshold sliding iterative mode to optimize the spectrum estimation result, and thus ensuring the obtainment of a most effective spectrum estimation result. Accordingly, by employing the present invention, the center frequency of the QPSK signal can be accurately estimated, in a low SNR condition, and a result shows that the spectral estimation accuracy still can reach about 0.5KHz even when a signal power level is low as -110dBm.

A modulation and demodulation method of a wave form synergy signal based on a frequency domain and a fractional Fourier domain orthogonal basis function relates to a signal modulation and demodulation method, and aims at solving the problem that a modulation and demodulation method of an existing quaternary phase shift keying (QPSK) signal is low in efficiency. Modulation and demodulation are achieved by a way of wave form synergy of a chirp signal and a sine and cosine signal, and therefore the modulation and demodulation method of the wave form synergy signal based on the frequency domain and the fractional Fourier domain orthogonal basis function is a novel modulation and demodulation method. In addition, two branches of chirp signals are respectively added to an I branch and a Q branch modulated by the existing QPSK signal and are used as carrier waves to respectively modulate one branch of baseband signal, so that existing two-way modulation is added up to four-way modulation, and at the demodulation end, filter waves are combined and matched by using a frequency domain template and a fraction domain template, and eight integrators are designed, and finally filtering results are combined so as to judge the information bit. The modulation and demodulation method is appropriate for the wireless communication field.