161results about How to "Reduce thermal noise" patented technology

The invention provides a capacitive distance sensor. The capacitive distance sensor is on the basis of the physical principle that the value of a capacitor is inversely proportional to the distance between capacitor plates; and once a coupling capacitor is generated between the surface of a detected conductor and a capacitance measuring plate on the single side of the surface of a sensor, the distance from the capacitance measuring plate to the surface of the detected conductor can be calculated by measuring the value of the coupling capacitor. The capacitive distance sensor provided by the invention has a circuit structure, and comprises the capacitance measuring plate, a reference capacitor, a capacitor coupling plate, a reference capacitor charging circuit, a capacitance measuring plate discharging circuit, a charge neutralization circuit, a programmable level generator 1, a programmable level generator 2 and a voltage comparator. The capacitive distance sensor has the characteristics of linearization, resistance to shifting, and low noise.

A multi-bit continuous-time sigma-delta analog-to-digital converter (ADC) has a differential input stage which receives an analog input signal current. A multi-bit feedback current digital-to-analog converter (IDAC) generates a multi-level feedback current depending on a digital feedback signal from a flash ADC. An integrator has a differential input that integrates the difference of the generated current by the multi-bit IDAC and the input signal current on a continuous-time basis. The input stage further comprises a first biasing current source and a second biasing current source which bias the input stage in a mid-scale condition. A first summing node connects to the first differential input line, a first differential input of the integrator and the first output branch. A second summing node connects to the second differential input line, a second differential input of the integrator and the second output branch. A set of chopping switches alternately connect the biasing current sources to the summing nodes in a first configuration and a second, reversed, configuration. The converter receives a modulator clock signal at a frequency F_S and the chopping switches can operate at F_S or a binary subdivision thereof. The integrator amplifier can also be chopper-stabilized.

A differential voltage controlled oscillator (VCO) employed in a frequency synthesizer used as a local oscillator of a wireless communication on-chip transmitter/receiver is provided. More particularly, a differential current negative feedback VCO equipped with a current-current negative feedback circuit that suppresses low- and high-frequency noise is provided.

A differential current negative feedback VCO includes a resonator determining oscillation frequency, and an oscillator generating negative resistance. In the oscillator of the differential current negative feedback VCO, transistors Q1 and Q2 form a cross-coupled pair, and negative resistance is generated by positive feedback of the cross-coupled pair. And, transistors Q1 and Q3 together with an emitter resistor and a capacitor form a current negative feedback part, and transistors Q2 and Q4 together with an emitter resistor and a capacitor form another current negative feedback part which is disposed opposite to a resonator. Thus, the VCO operates differentially.

In the oscillator of the differential current negative feedback VCO, emitter noise currents generated by base noise voltages of Q1 and Q2 induced by low- and high-frequency noise sources in the bases of Q1 and Q2 are sampled by emitter resistors, amplified through bases of Q3 and Q4, and thus return to the bases of the Q1 and Q2 and suppress the base noise voltages. Measurement of the phase noise of the differential current negative feedback VCO reveals a phase noise reduction of approximately 25 dB compared to a conventional differential VCO.

The invention discloses a high-reliability constant voltage mode semiconductor laser driver with continuously adjustable output light power, and relates to a semiconductor laser driver. The driver solves the problems of serious amplifier heating and slow current limiting protection response in the high power of a conventional semiconductor laser. A voltage sampling circuit of the driver is used for acquiring the voltage of a laser diode. A current sampling circuit of the driver is used for acquiring the current of the laser diode. Constant current control circuit is used for controlling the intensity of the current flowing through the laser diode. The sampling signal output end of the voltage sampling circuit is connected with the sampling signal input end of a micro control unit (MCU). The sampling signal output end of the current sampling circuit is connected with the sampling signal input end of the constant current control circuit. The control signal input end of the constant current control circuit is connected with the constant current control signal output end of the MCU. A thermal resistor is used for acquiring the temperature of the laser diode. A thermoelectric cooler (TEC) is used for cooling the laser diode. The driver is suitable for use as a novel high-reliability constant voltage mode light source with the continuously adjustable output light power.

A multi-bit continuous-time sigma-delta analog-to-digital converter (ADC) has an input stage which receives an analog input signal current. A multi-bit feedback current digital-to-analog converter (IDAC) generates a multi-level feedback current depending on a feedback signal. An integrator integrates a sum of the generated current and input signal current on a continuous-time basis. The IDAC has a first output branch including a first biasing current source and a second output branch including a second biasing current source. The biasing current sources supply a bias current to a respective branch of the IDAC to bias the input stage in a mid-scale condition. The biasing current sources are connected to the branches via chopping switches which connect the biasing current sources to the branches in a first configuration and a second, reversed, configuration. The integrator amplifier can also be chopper-stabilized, although preferably only the first stage is chopper-stabilized.

A headset driver circuit is described which comprises a connector interface. The connector interface comprises a first terminal, a second terminal and a third terminal for establishing respective electrical connections to a first speaker, a microphone and a common ground node of a headphone, earphone or headset, respectively. A first power amplifier is coupled to the first terminal to supply a first audio output signal to the first speaker of the headset. A first switch arrangement comprises a first ground switch is configured for selectively connecting and disconnecting the second terminal and a ground node of the headset driver circuit. The headset driver circuit further comprises a second ground switch configured for selectively connecting and disconnecting the third terminal and the ground node. The headset driver circuit also comprises a differential preamplifier, e.g. a microphone preamplifier, configured to generate a microphone output voltage where the differential preamplifier comprises a first signal input coupled to the second terminal and a second signal input coupled to the third terminal of the connector interface. An error suppression circuit is configured to sense or sample a noise or error voltage at the second terminal when ground connected or the third terminal when ground connected. The error suppression circuit is further configured to add the sensed or sampled noise or error voltage to a predetermined DC bias voltage and generate an error compensated DC bias voltage for the ungrounded one of the second and third terminals of the connector interface.

A capacitance type vibration sensor has a substrate including a hollow portion, a vibration electrode plate, which is arranged facing the hollow portion at an upper surface side of the substrate and which performs film vibration upon receiving vibration, and a fixed electrode plate which is arranged facing the vibration electrode plate and which is opened with a plurality of acoustic perforations passing therethrough in a thickness direction. The capacitance type vibration sensor has an air path, which communicates a space between the vibration electrode plate and the fixed electrode plate to the hollow portion, between an upper surface of the substrate and a lower surface of the vibration electrode plate in at least one part of a periphery of the hollow portion.

The invention discloses a GPS weak signal tracking system based on I/Q branch correlation integral observation filtering. A receiver is used for receiving a satellite signal which is converted into an intermediate frequency signal through down conversion and transmitted to a frequency mixer. The frequency mixer is also used for receiving local sine and cosine reproduction carrier signals outputted by a local carrier digital-controlled oscillator, and outputting a I-branch output signal and a II-branch output signal to a correlation arithmetic unit. The correlation arithmetic unit also receives a local advanced C/A code, an instant reproduction C/A code and a lagged reproduction C/A code, wherein the local advanced C/A code, the instant reproduction C/A code and the lagged reproduction C/A code are generated by a code generator. Results are outputted to an integral eraser, and six-way relevant integral values are generated and outputted to a Kalman filter. The Kalman filter obtains an estimated carrier phase difference, an estimated carrier frequency difference and an estimated code phase difference, and the estimated carrier phase difference, the estimated carrier frequency difference and the estimated code phase difference are transmitted to the local carrier digital-controlled oscillator and the code generator. The system effectively reduces the noise intensity of the satellite signal, can trace the satellite signal better in a weak-signal environment, and improves the tracing precision.

A analog to digital converter, comprising: an input for receiving an input signal to be digitised; a first converter core for performing a first part of an analog to digital conversion, and for outputting a first digital result; a first residue calculator for calculating a first residue as a difference between the input signal and the first digital result; a second converter core for performing a second part of the analog to digital conversion by converting the first residue; wherein at least one of the first and second converter cores comprises at least three analog to digital conversion engines and a controller for controlling the operation of the engines such that the engines collaborate to perform a successive approximation search, and wherein a plurality of bits can be determined during a single trial step of the successive approximation search.

A 2 [mu]m band low-noise narrow-linewidth single-frequency fiber laser is provided, which comprises a single-frequency laser resonant short cavity, a resonant cavity temperature control module, a wavelength division multiplexer, a co-band pumping source, a pumping source intensity noise suppression module and an optical isolator. The invention uses a laser with small difference between the workingwavelength and the laser signal wavelength as a co-band pumping source, uses an intensity noise suppression module to suppress the noise of the pumping source, and then uses a low-noise pumping source to pump the 2 [mu]m single-frequency laser resonant short cavity. Finally, single frequency fiber laser with low noise, narrow linewidth, and the working band of 2 [mu]m is output from the cavity. The laser provided by the invention has the advantages of all-optical fiber structure, excellent noise performance, extremely narrow laser linewidth, high conversion efficiency, simple structure, etc.,and can be used for atmospheric measurement, laser radar, biomedical, and realizing laser output in 3-5 [mu]m band as a pump source of an optical parametric oscillator (OPO) and the like.

The invention discloses a laser fuse reception system, which comprises a reception optical unit, a photoelectric detector connected to the reception optical unit, a preposition amplification circuit connected to the photoelectric detector, and a distance gain control circuit connected to an output terminal of the preposition amplification circuit. According to the invention, the photoelectric detector and the preposition amplification circuit arranged in the reception system, a photoelectric crosstalk problem can be solved; the distance gain control circuit is arranged, so that signal filtering and distance gaining functions can be increased, problems of large laser fuse view field and long effect distance can be solved, and reception rate is increased.

The invention discloses a balanced type photoelectric detector in a 2mu m coherent laser wind-finding radar system, which aims at solving the problems that in the 2mu m coherent laser wind-finding radar system, analog devices of the balanced type heterodyne photoelectric detector are multiple, so that no only is the cost high, but also heat noise is caused. Two PIN photoelectric diodes with almost completely same parameters are manufactured on one detection unit simultaneously. Incident signal light and local light are divided into two beams respectively through a beam splitter, are respectively guided into two reverse PIN tubes with matched parameters so as to carry out optical frequency mixing on light sensitive surfaces of two PIN photoelectric detectors, then generating heterodyne signals respectively, and outputting the balanced heterodyne intermediate-frequency signal by a two-stage amplifier after passing through a differentiator, wherein a capacitor C1, a capacitor C2 and a capacitor C3 play a role in filtering. The balanced type photoelectric detector disclosed by the invention is used for converting optical signals into electric signals.

The invention provides a non-refrigeration infrared polarization detector pixel structure and a preparation method. The non-refrigeration infrared polarization detector pixel structure comprises a bottom layer, a middle layer and an upper layer, wherein the bottom layer comprises a reading circuit substrate, a first metal electrode layer, a metal reflection layer and a first medium protection layer, and the first metal electrode layer, the metal reflection layer and the first medium protection layer are arranged on the reading circuit substrate; the middle layer comprises a first supporting layer, a thermosensitive layer, a second medium protection layer, a second metal electrode layer and a third medium protection layer; and the upper layer comprises a second supporting layer and an optical grating layer, wherein the second supporting layer is arranged above the third medium protection layer, and the optical grating layer is arranged on the second supporting layer and comprises a plurality of optical gratings arranged in sequence. By use of the non-refrigeration infrared polarization detector pixel structure and the preparation method, volume is greatly reduced, thermal noise introduced by the optical grating layer is lowered, and polarization detection sensitivity is improved so as to be favorable for increasing the extinction ratio of the optical grating layer.

A signal processing circuit has a sample/hold circuit for sampling an input signal comprised of a first signal and a second signal and for holding the first signal. The first signal comprises an optical signal obtained due to storage of electric charges generated due to light incident upon a photoelectric converter, and the second signal comprises a reference signal obtained due to resetting of the photoelectric converter. A subtracter receives an output signal of the sample/hold circuit and the input signal and obtains a difference between the output signal of the sample/hold circuit and the input signal. A voltage clamp circuit clamps a part or all of an output signal from the subtracter.

A microphone circuit includes a capacitor capsule and first and second impedance converters connected differentially to the capacitor capsule. The microphone circuit includes first and second output buffer amplifiers connected differentially to the first and second impedance converters.

The invention discloses a methane sensor based on a single heating element, a preparation method and application. The methane sensor is suitable for industrial and mining enterprises and comprises a heating element, a measuring element, and an environment temperature measuring element, wherein a heater of the heating element of the methane sensor and a measuring component of the measuring element are suspended in air through supporting arms; the heating element independently heats to the high-temperature working state; the measuring element is independently used for detecting gas concentration; the temperature on a detecting sheet of the environment temperature measuring element detects is used for temperature compensation. The processing technology of the methane sensor is compatible with the CMOS (Complementary Metal Oxide Semiconductor) technology. The sensor has the advantages that the sensor is simple in structure, low in power dissipation, high in sensitivity, good in anti-jamming performance, and low in cost.