30results about How to "Adjustable center frequency" patented technology

The invention discloses a distributed optical fiber sensing device based on a chaotic laser coherence method, and a measurement method of the distributed optical fiber sensing device. Chaotic laser light which is emitted from a chaotic laser is divided into detection light and reference light; the detection light is amplified by a light amplifier and then emitted into a sending optical fiber through an optical circulator, and a backward Brillouin scattering light signal is generated in the optical fiber; the Brillouin scattering light signal is amplified by the light amplifier, de-noised by a tunable light filter and then emitted into an optical fiber coupler; the optical length of the reference light is regulated by a variable light delay line, and interferes with the backward Brillouin scattering light signal which is generated by the detection light at different positions in the sensing optical fiber in the optical fiber coupler; an interference beat frequency signal is detected by a photoelectrical detector; and Brillouin gain spectra at different lengths are obtained through a data acquisition device and a signal processing device and then output to a display device, so strain or temperature sensing detection is realized.

The invention discloses an optical bandpass filter based on a double microring-Mach Zehnder interference structure. The optical bandpass filter is composed of a first multi-mode interference coupler, a second multi-mode interference coupler, a third multi-mode interference coupler, a first coupling grating, a second coupling grating, a first heating electrode, a second heating electrode, a third heating electrode, a fourth heating electrode, a first upload-download type micro ring, and a second upload-download type micro ring. According to the invention, on the basis of the design of the coupling states of two upload-download type micro rings, fully destructive interference is introduced based on a cascaded adjustable Mach Zehnder interference (MZI) structure; amplitude regulation is realized by adjusting the bias voltage on the heating electrode of the MZI1, so that amplitudes of passband external light signals of an upper arm and a lower arm becomes identical; and phase regulation is realized by adjusting the bias voltage on the heating electrode of the MZI2, so that phases of passband external light signals of the upper arm and the lower arm are opposite. Therefore, the extinction ratio of the filter increases under the circumstance that the passband insertion loss is not increased. The provided optical bandpass filter has advantages of narrow bandwidth, high extinction ratio, and low insertion loss.

An ultrahigh Q-value single-passband microwave photon filter comprises a tunable filter, an optical coupler, a single-sideband modulation module, a single-sideband suppression carrier modulation module, a microwave signal source, an optical isolator, an optical amplifier, a single-mode optical fiber, an optical circulator, an optical fiber circulation cavity, a photoelectric detector and a vectornetwork analyzer, wherein the tunable filter is connected with the optical coupler, the optical coupler is connected with the single-sideband modulation module and the single-sideband suppression carrier modulation module, the optical isolator is connected with the single-sideband modulation module, the single-mode optical fiber is connected with the optical isolator, the microwave signal source is connected with the single-sideband suppression carrier modulation module, the single-sideband suppression carrier modulation module is connected with the optical fiber amplifier, the optical fiber amplifier is connected with the optical circulator, the optical fiber circulation cavity is connected with the optical circulator and is connected with the photoelectric detector, the photoelectric detector is connected with the vector network analyzer, and the vector network analyzer is connected with a microwave of the single-sideband modulation module.

The invention discloses an adjustable transformer. A circuit structure is composed of a port 1 (Port 1), a port 2 (Port 2), resistors, capacitors and inductors, wherein coupling is existed between two inductors, two circuit units are connected through a coupling capacitor, and the central frequency and out-of-band transmission zero point of the transformer can be regulated through changing values of a resonant capacitor and a coupling capacitor. The adjustable transformer can realize wide band width and can be broadly used for 5G mobile communication power dividers and the like which are strict in signal performance; the adjustable transformer is capable of reducing the out-of-band noise and improving the electronic circuit stability.

The invention provides a three-notch ultra-wideband filter based on defected microstrip structures, which comprises a microstrip substrate, and a first input/output port, a second input/output port, a first uniform line transmission unit, a second uniform line transmission unit, a first parallel coupled feeder, a second parallel coupled feeder and an E-type multimode resonant structure arranged on the microstrip substrate, wherein a first defected microstrip structure, a second defected microstrip structure and a third defected microstrip structure are arranged on the E-type multimode resonant structure; and each defected microstrip structure is formed by three linear grooves connected in sequence and with the same width in the E-type multimode resonant structure. Three-notch features are provided, the central frequency of the notch is adjustable through adjusting the length of the defected microstrip structure, and product debugging and batch production are facilitated.

The invention discloses a bandwidth and center frequency adjustable three-passband filter based on a single multimode SIW cavity. The three-passband filter comprises a polygonal dielectric substrate,a metal layer is arranged on the upper surface of the dielectric substrate, and the lower surface of the dielectric substrate is provided with a metal grounding plate. The dielectric substrate is respectively provided with an input port feeder line and an output port feeder line, a central metal perturbation through hole, a first metal perturbation through hole group, a second metal perturbation through hole group, a first side metal perturbation through hole and a second side metal perturbation through hole are formed in the dielectric substrate, and a first rectangular perturbation groove and a second rectangular perturbation groove are etched in the upper surface metal layer.

The invention discloses a plane low-pass band-pass dual-frequency filter which is manufactured on a dielectric substrate in a printed circuit board manner. An input end feeder line port 1 for inputting an electromagnetic wave signal, an output end feeder line port 2 for outputting an electromagnetic wave signal, a first transmission line (1), a second transmission line (2), a third transmission line (3), a fourth transmission line (4), a fifth transmission line (5), a six transmission line (6) and a seventh transmission line (7) are manufactured on the same surface of the dielectric substrate; an earth plate is arranged on the other surface of the dielectric substrate. On the premise that the low-pass characteristic is not changed, the band-pass center frequency can be adjusted in a large range; the filter comprises an open circuit transmission line and a high impedance line, enables the band-pass center frequency to be independently adjusted within a larger range by adjusting the electrical length and characteristic impedance of the transmission lines, and has the advantages of adjustable frequency, good selectivity, low loss and simple structure.

The invention provides an antenna matching circuit. The circuit comprises an adjustable matching circuit connected with an antenna, and a control unit connected with the adjustable matching circuit; the adjustable matching circuit comprises a dielectric substrate, a 50-omega microstrip connecting line, a microstrip transmission line, a microstrip open-circuit branch, an adjustable varactor diode and a capacitor bias circuit; the control unit is used for obtaining the real-time load of the antenna and adjusting the capacitance value of the adjustable varactor diode; the 50-omega microstrip connecting line is an input microstrip connecting line; the microstrip transmission line comprises a first microstrip transmission line, a second microstrip transmission line and a third microstrip transmission line; and the microstrip open-circuit branch envelops the first microstrip open-circuit branch, the second microstrip open-circuit branch and the third microstrip open-circuit branch. Accordingto the invention, when the antenna load changes, the center frequency of the matching circuit can be adjusted, the real part change of the antenna load impedance is 50 omega, the imaginary part change is 50 omega, the output port can be matched in real time, and the antenna matching circuit has the advantages of being flexible in design and easy to tune.

The invention discloses a reconfigurable optical all-pass filter. The reconfigurable optical all-pass filter comprises three optical couplers, N+2 optical phase shifters and N micro-rings, wherein the output end of the first optical coupler, the input end of the second optical coupler and the first optical phase shifter form an MZI1 structure, and the output end of the second optical coupler, the input end of the third optical coupler, the second optical phase shifter, the third optical phase shifter and the first micro-ring form an MZI2 structure. The interference characteristic of a Mach-Zehnder interferometer and the resonance characteristic of a micro-ring are utilized, a signal is input into a chip and is divided into two paths through an MZI1 structure to be input into an MZI2 structure, one path of signal is filtered by the micro-ring, and the other path of signal passes through the phase shifters and a waveguide, the two paths of signals are interfered by the third optical coupler, are processed by the plurality of cascaded all-pass micro-rings, and are finally output from the second coupling grating. By changing the amplitude ratio and the phase difference of the two paths of signals and adjusting the coupling coefficient of the micro-ring, flat amplitude-frequency response is realized, so that the all-pass filter is realized.

The invention provides a system for generating a center-frequency-variable high-speed linear frequency modulation signal based on a phase-locked loop, and belongs to the field of radio frequency. Thesystem comprises an operational amplifier, a single-chip microcomputer, a phase-locked loop, a crystal oscillator, a loop filter, an adder, a voltage-controlled oscillator and a directional coupler. The operational amplifier is connected with the adder, the single-chip microcomputer and the crystal oscillator are both connected with the phase-locked loop, the phase-locked loop is connected with the adder through the loop filter, the adder is connected with the directional coupler through the voltage-controlled oscillator, and the directional coupler is connected with the phase-locked loop. According to the invention, the phase-locked loop is used to accurately lock the center frequency of the output chirp signal; the modulation signal and the direct current signal output by the phase-locked loop are superposed through the adder; the size of the linear frequency modulation signal and the sweep frequency bandwidth are controlled, the single-chip microcomputer is used to control the switching of the center frequency, the purposes of ultra wide band and adjustable center frequency are achieved, the response speed of the sweep frequency signal is ensured by using a direct driving mode,and higher and higher performance requirements can be satisfied.

The invention discloses a compact electrically tunable balanced band pass filter. The filter comprises an upper layer of a microstrip line structure, a middle layer of a dielectric substrate and a lower layer of a grounding metal patch and metal through holes. The microstrip line structure comprises a multimode resonator and two pairs of input/output feeders. The multimode resonator comprises a first microstrip line and a second microstrip line which are symmetrical up and down; the first microstrip line and the second microstrip line are all E-shaped; the first microstrip line faces downwards; the second microstrip line faces upwards; the microstrip branch lines at the left and right two sides of the first microstrip line are connected with the microstrip branch lines at the left and right two sides of the second microstrip line respectively through two variable capacitance diodes which are connected in series; the central microstrip branch line of the first microstrip line is connected with the central microstrip branch line of the second microstrip line through two variable capacitance diodes which are connected in series; and a section of short microstrip branch line is loaded at the center of the two variable capacitance diodes which are connected in series. According to the filter provided by the invention, the central frequency of a passband is tunable; and the bandwidth is tunable.

The invention belongs to the technical field of radar signal generation, in particular to a multi-frequency signal generation method. The invention utilizes the DDS chip, supplemented by FPGA control, uses tools such as matlab to calculate the phase waveform data in a cycle, and writes the data into the DDS chip RAM through hardware logic. The curve and the preset playback rate will play the signal to complete the multi-frequency signal modulation.

The invention provides an active filtering device adjustable to fit various specifications. A first filter has a first quality factor to define the frequency width and the center frequency of the filtering device; a second filter is connected to the first filter and has a second quality factor, and the frequency spectrums of the first filter and the second filter are used for defining the frequency of the filter at low frequency in frequency width and the sharpness of the frequency width at low frequency in the frequency width; a third filter is connected to the second filter and has a third quality factor, and the frequency spectrums of the first filter and the third filter are used for defining the frequency of the filter at high frequency in the frequency width and the sharpness of the frequency width at high frequency in the frequency width; the value of the first quality factor is adjustable, and the adjustment range is between 5 and 15; and the value of the second quality factor and the third quality factor is adjustable, and the adjustment range is above 15.