132results about How to "High spectral purity" patented technology

Provided is a microwave-signal generating method and device based on the excited brillouin scattering effect and the optical frequency comb in high nonlinear fibers. The invention belongs to the technical field of microwave photonics. The device comprises a tunable laser, a first coupler, a second coupler, a first circulator, a second circulator, a first high nonlinear fiber, an attenuator, a fourth coupler, a first photoelectric detector, a power divider, an intensity modulator, a fourth DC voltage regulator, a first double parallel mach-zehnder modulator, a fifth DC voltage regulator, a sixth DC voltage regulator, a seventh DC voltage regulator, a third circulator, a second high nonlinear fiber, a third coupler, a second photoelectric detector, a microwave amplifier, a second double parallel mach-zehnder modulator, a first DC voltage regulator, a second DC voltage regulator, a third DC voltage regulator, an isolator, a fifth coupler, a third photoelectric detector and a frequency analyzer. Due to the advantages of mode selection and positive feedback of a photoelectric oscillator, the microwave signals which are output by the device have the advantages of good spectrum purity and low noises.

The invention discloses a photoelectric oscillator based on an optical resonant cavity, and aims to carry out photoelectric oscillation on laser so as to generate high-quality microwave signals. The photoelectric oscillator consists of a laser, a photoelectric modulator, an amplifier, a filter, a photoelectric detector and an optical resonant cavity which form a loop, wherein the loop forms the main structure of the photoelectric oscillator. The photoelectric oscillator disclosed by the invention has outstanding advantages in generating high-quality microwave signals in a light domain, and high-quality microwave signals can be formed through multiple times of oscillation; the optical resonant cavity is adopted to output the microwave signals through multiple times of oscillation, and the invention mainly aims to minimize the photoelectric oscillator; the optical resonant cavity is adopted to replace conventional long optical fibers, so that the photoelectric oscillator has the characteristics of small size, low consumption, stable performance and the like, and is applicable to the field of radio wireless communication and microwave photonics; the optical resonant cavity is realized through coupled prisms and micro disc cavities and thus is relatively stable in property when being compared with an optical resonant cavity realized through coupled waveguide and micro discs.

The invention provides a dual-mode voltage-controlled oscillator (DMVCO), a frequency synthesizer and a wireless receiving device, and pertains to the technical field of integrated circuit of radio frequency wireless receiver. The DMVCO and the frequency synthesizer can operate in a wideband mode and a quadrature mode. When operating in the quadrature mode, a quadrature signal is provided for a Single Sideband Mixer of the frequency synthesizer by a quadrature coupling of a first voltage-controlled oscillator unit and a second voltage-controlled oscillator unit in the DMVCO in the overlapped frequency band so that the frequency synthesizer can cover a higher output frequency band. Therefore, the tuning range of the DMVCO of the invention is wide, and the frequency synthesizer using the DMVCO is low in power consumption, simple in structure and has good frequency spur performance.

An optical apparatus for illuminating an object, for example an illumination system of a microlithographic exposure system, comprises a light source that generates a plurality of individual bundles that constitute an illumination bundle. A control device controls the light source in such a way that a desired form of the illumination bundle is determined by selecting an appropriate set of individual bundles.

The invention relates to a frequency synthesis source applied by a DDS short-wave transmitter based on a CPLD design. The frequency synthesis source mainly comprises a direct digital synthesis circuit, a high-speed DAC transformation circuit, a tracking filter circuit and a gain control circuit, a controller and a phase locked crystal oscillator. According to the invention, the high-speed DAC transformation circuit converts frequency data output by direct digital synthesis circuit to a sine frequency signal; and the tracking filter circuit filters components of stray and harmonic wave in the high-speed DAC transformation circuit, and the gain control circuit enables the output of the direct digital synthesis circuit to be stable in amplitude within a frequency range. In addition, the controller comprises a microprocessor and a microcomputer, wherein the microprocessor is connected with the microcomputer through an interface circuit of the microcomputer, and frequency arrangement and transition of working mode are realized by an upper computer. The phase locked crystal oscillator generates a clock source signal with ultrahigh frequency and high stability, and the clock source signal is used as a clock signal of the frequency synthesis source. The frequency synthesis source applied by a DDS short-wave transmitter based on a CPLD design provided in the invention has advantages of high frequency accuracy and high distinguishability, short switching time of frequency signals, constant output amplitude, and simple and high-reliable circuit.

An apparatus and a method provide synchronization of an output signal to a synchronization information. The synchronization is accomplished by providing coupling of a correction control information that controls a signal generator, e.g. a phase locked loop arrangement or a direct digital synthesis arrangement, to its exact frequency to a frequency conversion unit that converts an uncorrected reference frequency to a correct or exact reference frequency. Thereby, the uncorrected reference frequency for the signal generator can be provided by a simple crystal oscillator without any frequency controller. The setting of the signal generator and the frequency conversion unit can be done in a predetermined sequence which enables a user equipment to synchronize its reference frequency to the synchronization information emitted by a communication network.