36results about How to "Avoid phase noise" patented technology

The invention discloses a method for measuring an electro-optic phase modulator modulation factor, and relates to the technical field of the photoelectronic technique. In order to solve the problems that phase modulation signals cannot be directly detected on a photoelectric detector and nonlinearity cannot be omitted in PM-IM and FM-IM conversion processes, an optical fiber interferometer is adopted as a measuring device and composed of a beam splitter, an electro-optic phase modulator to be measured, an acousto-optic frequency shifter, an auxiliary electro-optic phase modulator and a beam combiner, wherein the electro-optic phase modulator to be measured is arranged on one interference arm of the optical fiber interferometer, the acousto-optic frequency shifter and the auxiliary electro-optic phase modulator are placed on the other interference arm of the optical fiber interferometer, and sinusoidal signals with different frequencies are loaded to the electro-optic phase modulator to be measured, the acousto-optic frequency shifter and the auxiliary electro-optic phase modulator respectively. Frequency response of the photoelectric detector is eliminated by setting a frequency relation of the loaded sinusoidal signals, self-calibration measurement is achieved, measuring accuracy of the electro-optic phase modulator modulation factor is improved, and the method has good application value.

The invention provides a frequency response measuring device and method of a high-speed photoelectric detector, and the frequency response measuring device and method of the high-speed photoelectric detector are used for solving the problem that an existing frequency response test of the high-speed photoelectric detector is not accurate. The frequency response measuring device comprises a first signal source, a second signal source, a third signal source and an optical fiber interferometer. The optical fiber interferometer is composed of a beam splitter, a polarization controller, a phase modulator, an acousto-optic frequency shifter and a beam combiner. The polarization controller and the phase modulator are connected with one interference arm of the optical fiber interferometer in series. The acousto-optic frequency shifter is placed on the other interference arm of the optical fiber interferometer. The beam splitter and the beam combiner are connected to the two ends of the two interference arms respectively in series. A light path of the beam splitter is connected with a laser. A light path of the beam combiner is connected with the high-speed photoelectric detector to be detected. The high-speed photoelectric detector to be detected is in circuit connection with a sampling circuit used for recording and analyzing. The first signal source and the second signal source are in circuit connection with an electrode of the phase modulator through a combiner. The third signal source is electrically connected with the electrode of the acousto-optic frequency shifter.

The invention provides a sigma-delta PLL frequency measuring circuit and method. The circuit comprises a rectifying circuit, a phase discriminator, a loop filter, an ADC and a delay link which are sequentially arranged from the input end. The output end of the delay link is fed back and input to the phase discriminator through a counter. The frequency measuring method comprises the steps that after the rectifying circuit filters and amplifies a signal to be detected, the signal to be detected is converted into a square signal with the frequency same as that of the signal to be detected; the phase discriminator measures the zero crossing point time difference of the square signal and an output signal of the counter, and a pulse current signal with the output area and the time in a direct proportion; after the integration and the filtering are carried out on an output current of the phase discriminator through the loop filter, the output current is converted into a voltage signal; the ADC converts analog voltage output by the loop filter into a digital signal; the delay link delays the digital signal output by the ADC, and therefore the frequency of the signal to be detected is determined; a counter output signal with the clock period and the delayed digital signal in a direct proportion is generated by the counter, and is output to the phase discriminator. The anti-noise capacity is strong in the process of measuring the frequency, the resolution ratio is high, and the frequency measurement can be achieved easily.

The invention discloses an optical generation method of a dual-band phase-coded signal, and relates to the technical field of microwaves and the technical field of optical communication. The method is shown in a figure 1 in the specification, and comprises a laser device LD, a dual-polarization quadrature phase shift keying modulator DP-QPSK, a polarization controller PC, a polarization beam splitter PBS and a balanced photoelectric detector BPD. A baseband phase coded signal is modulated to an optical carrier through an X-DPMZM in the DP-QPSK, and a local oscillator signal generates positive and negative first-order optical sidebands through a Y-DPMZM in the DP-QPSK; the PC is adjusted, the included angle between the polarization state of the DP-QPSK output optical signal and the PBS main shaft is controlled, and then a phase coding signal can be obtained after photoelectric balance detection. According to the invention, dual-band phase-coded signals can be simultaneously generated. Not only is the electronic bottleneck of the electric field technology overcome, but also the working bandwidth is expanded; and due to the dual-band characteristic, the system has potential application value in a dual-band radar.

A PLL system includes: an input end; an output end; a first PFD; a first CHP connected to the first PFD; a first LPF connected to the first CHP; a first VCO connected to the first CHP and the first LPF; a second PFD connected to the first VCO; a second CHP connected to the second PFD; a second LPF connected to the second CHP; a second VCO connected to the second CHP and the second LPF; a first DIV connected to the first PFD and the second VCO; and a second DIV connected to the second PFD and the second VCO. A working method of the PLL system is also provided, which can restrain input noise as well as phase noise of the second VOC in such a manner that noise of the PLL system is well restrained.

The invention relates to a vibration monitoring system based on a double fiber grating array, which is characterized in that a narrow linewidth laser, a pulse light modulator, a pulse light amplifierand an optical filter are connected in order, an output terminal of the optical fiber is connected with a first communication terminal of a circulator, a second communication terminal of the circulator is connected with a front first communication terminal of a coupler, a back first communication terminal of the coupler is knotted and out of service, a third communication terminal of the circulator is connected with a first signal input terminal of an embedded signal processor, a front second communication terminal of the coupler is connected with a second signal input terminal of the embeddedsignal processor, a front third communication terminal of the coupler is connected with a third signal input terminal of the embedded signal processor, a back second communication terminal of the coupler is connected with a first optical fiber of the double fiber grating array, and a back third communication terminal of the coupler is connected with a second optical fiber of the double fiber grating array. The vibration monitoring system can restore vibration signals more authentically without increasing the hardware cost.

The invention discloses a multi-band linear frequency modulation signal generation method capable of flexibly selecting frequencies, and relates to the technical field of microwaves and the technical field of optical communication. The method is shown in a figure 1 in the specification, and comprises a laser device LD, a dual-polarization binary phase shift keying modulator DP-BPSK, an arbitrary waveform generator AWG, an erbium-doped fiber amplifier EDFA, a polarization controller PC, a polarizer POL and a photoelectric detector PD. Phase modulation is carried out on a local oscillator signal through the DD-MZM1 of the DP-BPSK upper arm, and carrier suppression double-sideband modulation is carried out on an IF-LFM signal through the DD-MZM2 of the DP-BPSK lower arm; the PC is adjusted, the phase difference between the two polarization states is controlled, and then a multiband linear frequency modulation signal can be obtained after POL and photoelectric detection. According to the invention, the electronic bottleneck of the electric field technology is overcome, and the characteristic of flexible frequency tuning is added; multi-band signals are generated at the same time, so that the system has potential application value in a multi-band radar and a distributed radar system.

The invention relates to a time domain direct wave suppression method for a transmitting-receiving split short-wave over-the-horizon radar. The invention relates to the time domain direct wave suppression method for the transmitting-receiving split short-wave over-the-horizon radar. The invention aims to solve the problem that the direct wave suppression effect of the existing method is poor. The method comprises the following steps: 1, obtaining an echo signal; 2, reconstructing an ideal reference signal; 3, direct waves are extracted from the multi-channel echo signals through the DBF; 4, performing short-time Fourier transform on the reconstructed ideal reference signal to form a filtering template, performing short-time Fourier transform on the direct wave signal, filtering by adopting the filtering template to obtain a filtering result, and performing short-time Fourier inverse transform reconstruction on the filtering result to obtain a time domain reference signal; and 5, taking the obtained time domain reference signal as a reference signal of an adaptive filter, and carrying out direct wave suppression on the echo signal to obtain the echo signal after direct wave suppression. The method is applied to the field of short-wave beyond-visual-range radar signal processing.