38results about How to "Reduce dispersion effect" patented technology

A system (100) for transmitting digital information includes a transmitting apparatus (102) for generating an optical signal bearing digital information, a dispersive optical channel (104), and a receiving apparatus (110) for receiving the optical signal. The dispersive optical channel (104) is disposed to convey the optical signal from the transmitting apparatus (102) to the receiving apparatus (110). The transmitting apparatus includes an encoder (114) for encoding digital information into a series of blocks, each including a plurality of data symbols corresponding with one or more bits of digital information. A signal generator (118) generates a time-varying signal corresponding with each of said blocks. An optical transmitter (136) is arranged to apply the time-varying signal to an optical source (138) to produce an optical signal which includes an optical carrier and substantially only a single information bearing optical sideband in an optical frequency domain, the sideband corresponding with the time-varying signal. The receiving apparatus (110) includes an optical detector (146) for detecting the optical signal to produce a corresponding received time-varying electrical signal. The receiver further includes means (166) for generating a series of received data blocks from the time-varying electrical signal. An equaliser (168) performs an equalisation of received data symbols included in each data block to mitigate the effect of dispersion of the optical channel, thereby enabling the transmitted data symbols to be recovered.

A fiber optic link is provided that is receptive of an AM RF input signal, includes an analog comparator for comparing the input signal with a triangle waveform to convert the input signal to a PWM signal. The PWM signal is converted into an optical signal, and transmitted over a fiber optic cable to an optical receiver. The optical receiver converts the optical signal back into a PWM signal, which is amplified via a Class D amplifier. The amplified PWM signal is passed through a low pass filter for converting it into an AM RF output signal having a predetermined power level, the output signal corresponding to the AM RF input signal.

A receiver system processes a received optical signal that carries user information. The receiver system includes a splitter, a first converter, a second converter, and a detection system. The splitter splits the received optical signal based on polarization into a first optical signal and a second optical signal. The first converter converts the first optical signal into a corresponding first electrical signal. The second converter also converts the second optical signal into a corresponding second electrical signal. The detection system applies radio frequency detection to the first electrical signal to generate a third electrical signal. The detection system applies radio frequency detection to the second electrical signal to generate a fourth electrical signal. The detection system then combines the third electrical signal and the fourth electrical signal to form a fifth electrical signal that carries the user information.

An inventive antenna comprises two antenna elements forming a planar slotline antenna. The antenna furthermore comprises absorber elements surrounding the antenna elements on two layers. The absorber elements are shaped to partially cover the antenna elements and partially not cover the antenna elements. Moreover, they are shaped to dampen at least a dipole-mode of the antenna elements and not to dampen a slotline-mode of the antenna elements.

The invention provides a forecasting method for vehicle body structure-acoustic coupling based on a smoothed finite element boundary element method. The method comprises the following steps: generating a vehicle body structure-acoustic grid model; utilizing the smoothed finite element method to perform smooth processing on the stress field in a shell unit; adopting a mixed integral method to perform separate integral of shearing items subjected to shearing strain in the shell under a natural coordinate system; building a smooth Galerkin weak form of a vehicle body shell structure kinetic equation, and obtaining a dynamic equation after the weak form is subjected to discrete processing; creating an acoustic realistic model by using the boundary element method; according to the continuous displacement and pressure of the coupling interface, obtaining a structure-acoustic coupled smoothed finite element boundary element model; performing simulation forecasting by utilizing the coupled model. When the method is used for solving the vehicle body structure-acoustic coupling problem, relatively good calculation effect can be obtained, and the band frequency width can be analyzed more effectively. Moreover, the method has relatively low quality requirements on the model to reduce the pretreatment time, and has a wide engineering application prospect.

A device for transmitting synchronized timing including a receiver, a transmitter, one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including instructions for receiving through the receiver a timing signal comprising first time information that is synchronized to a time standard, determining second time information based at least partially on the first time information, composing a message formatted in accordance with a global navigation satellite system (GNSS) standard, wherein the message comprises the second time information, and transmitting the message through the transmitter on a radio signal having a frequency in the frequency modulation (FM) radio frequency band.

The invention discloses a double balanced mixer device which comprises a mixer chamber body, a mixer circuit, and a K type joint; the mixer circuit further comprises a mixer tube, a gold belt, gold wires, 50 omega coplanar waveguide, a coupling slot line, a 60 omega slot line, a dielectric substrate, and a lambada/8 short-circuit wire. According to the double balanced mixer device, the K type joint is adopted, the 50 omega coplanar waveguide is selected as the signal end and is transited to the coupling slot line, the coupling slot line is gradually changed to the 60 omega slot line and is added to the mixer tube, the 50 omega coplanar waveguide is coupled to the slot line by the adoption of a gold belt coupling mode, and capacitive quality of mixer diodes is counteracted; the broadband barron is achieved by the adoption of a magic T network which is composed of the coplanar waveguide, the coupling slot line and the slot line, crisscross of transmission lines is not needed and strong directivity is achieved, and isolation is improved; color dispersion effect of the coplanar waveguide is relieved; a golden wire bridge joint mode is adopted, so that the occurrence of a higher order mode is inhibited, and the higher order mode of the coupling slot line stimulated by radio frequency in the coplanar waveguide is prevented.

An optical fiber for reducing modal dispersion and increasing both travel distance and transmission speed. A core center is formed in the core of the optical fiber. The core center is doped with impurities, is hollow, or is pulled at a lower temperature to increase diffraction of the core center. The core center discriminates the low order modes such that only the high order modes are present in the optical fiber. Because the low order modes are absorbed or otherwise discriminated against, the range of propagation constants is reduced and modal dispersion is likewise reduced. High order modes can be launched in the optical fiber using a lens whose center portion is obscured or by using a diffractive lens to couple a source to the optical fiber.

The invention discloses an FCT-FDM forward simulation method based on a dispersion viscosity wave equation. A propagation characteristic of a dispersion viscosity wave is researched from the perspective of the numerical simulation. Calculating steps of FCT-FDM is stated, a fluid saturation model is designed, the method is utilized to simulate propagation of the dispersion viscosity wave, and comparing and analyzing are carried out on a numerical result and a sound wave simulation result. The result indicates that relative to a sound wave, the dispersion viscosity wave is obviously attenuated on the amplitude, and the phase position is notably changed. The attenuation degree of the dispersion viscosity wave mainly depends on a dispersion attenuation coefficient and a value of the dispersion attenuation coefficient. According to the FCT-FDM forward modeling method based on the dispersion viscosity wave equation, an effective tool is provided for the numerical simulation of a seismic wave, in particular to a medium containing fluid. The FCT-FDM forward modeling method based on the dispersion viscosity wave equation can be used for describing the attenuation and the phase-shift characteristic of the seismic wave in the fluid medium. In addition, the method is easy to achieve, and the operability is high.

The invention relates to a CPW feed high-isolation two-stop-band MIMO antenna. The antenna comprises a substrate, an antenna and a grounding plate, and is characterized in that the antenna comprises two radiation units; a circular monopole UWB antenna is contained in each radiation unit; the two circular monopole UWB antennas are perpendicular to each other; and the circular monopole UWB antennascorrode an SRR groove. Compared with the prior art, the antenna adopts a coplanar waveguide feed mode, so that the dispersion effect can be reduced; the antenna is simple to manufacture and compact instructure, a winding, a via hole and a corresponding parasitic source inductor are omitted, so that radiation loss caused by surface waves is reduced, and antenna gain is increased; high isolation and notch characteristics are realized; by adopting the FR4 material with economical efficiency, the antenna is small in size; and the whole antenna is simple in structure and easy to process.

Mitigating errors caused by the dispersion of optical or electrical signals. Errors caused by dispersion in high frequency system are mitigated by passing a received signal through an adjustable linear filter that counteracts a channel response of a channel on which the received signal has traveled to produce an electrical signal. The adjustable linear filter has a number of coefficients. A figure of merit is calculated for the electrical signal, where the figure of merit includes the second and fourth moments of the electrical signal. The coefficients of the linear filter are adjusted based on the value of the figure of merit so as to minimize the figure of merit.

The invention discloses a 10G-PON application oriented cooler-free OLT optical assembly and optical module. A special 1577nm direct modulation laser (DML) is used, a dispersion effect can be reduced,and 10G-PON down transmission requirement can be satisfied. The temperature of the DML needs not to controlled via a semiconductor cooler (TEC) in packaging design. A heater is used in packaging, whenthe temperature is too low, the heater starts working, the working temperature range of the laser can be narrowed effectively, and the wavelength drift of the DMS does not go beyond the range (1575-1580nm) prescribed by 10G-PON within a wider ambient temperature change range. The semiconductor cooler is not needed, the power consumption is reduced, a packaging structure is simplified, the packaging yield rate is improved, and the cost of the 10G-PON OLT optical assembly and optical module are reduced greatly.

The invention discloses a totally-reflective femtosecond stimulated Raman spectrometer. The Raman spectrometer comprises a light source module, two beam splitters, two optical delay lines, a reflectorset, a concave mirror, a diaphragm, a spectral filtering module and a first spectrometer, wherein a femtosecond pulse laser generated by the light source module is split into two laser beams after passing through the first beam splitter, the reflected beam serves as actinic pump light and focuses on a sample after passing through a first reflector, a second reflector, a third reflector, the firstoptical delay line, a fourth reflector, a fifth reflector, a sixth reflector, a seventh reflector and the concave mirror sequentially; the transmitted beam is reflected after passing through the second beam splitter, serves as detection light and focuses on the sample after passing through an eighth reflector, a ninth reflector, a tenth reflector, an eleventh reflector, the seventh reflector andthe concave mirror sequentially, and the transmitted light is collected by the first spectrometer after passing through the diaphragm; and the second laser beam is transmitted after passing through the second beam splitter to serve as Raman pump light and focuses on the sample after passing through a twelfth reflector, a thirteenth reflector, a fourteenth reflector, the spectral filtering module,the second optical delay line, a fifteenth reflector, a sixteenth reflector, the seventh reflector and the concave mirror sequentially.