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541results about How to "Improve Noise Performance" patented technology

Residue-compensating A/D converter

An analog-to-digital converter system [50D] processing an input signal, g, which can be either a discrete-time or a continuous-time signal. A first quantizer [154] generates a first digital signal, d0(k), representing the sum of the input signal, g, and a dithering signal, y0. A digital-to-analog converter [156] generates an analog feedback signal, alpha, representing accurately the first digital signal, d0(k). The DAC [156] may be linearized by the use of mismatch-shaping techniques. A filter [158] generates the dithering signal, y0, by selectively amplifying in the signal band the residue signal, r0, defined as the difference of the input signal, g, and the analog feedback signal, alpha. Optional signal paths [166][168] are used to minimize the closed-loop signal transfer function from g to y0, which ideally will be zero. An analog compensation signal, m0, which is described by a well-controlled relationship to the residue signal, r0, is extracted from the filter [158]. Ideally, the closed-loop signal transfer function from g to m0 will be zero, or at least small in the signal band. A second quantizer [160] converts the analog compensation signal, m0, into a second digital signal, dm0(k). The two digital signals, d0(k) and dm0(k), are filtered individually and then added to form the overall output signal, dg(k). The second digital filter [164] has a low signal-band gain, which implies that the sensitivity to signal-band errors caused by the second quantizer [160] will be low. The output signal, dg(k), is a highly-accurate high-resolution representation of the input signal, g. Circuit imperfections, such as mismatch, gain errors, and nonlinearities, will cause only noise-like errors having a very low spectral power density in the signal band.The invention facilitates the implementation of uncalibrated highly-linear high-resolution wide-bandwidth A/D converters [50D], e.g., for use in digital communication systems, such as xDSL modems and other demanding consumer-market products for which low cost is of the essence.
Owner:ANALOG DEVICES BV

Differential front-end continuous-time sigma-delta ADC using chopper stabilisation

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 FS and the chopping switches can operate at FS or a binary subdivision thereof. The integrator amplifier can also be chopper-stabilized.
Owner:ANALOG DEVICES INC

Low-noise passive frequency mixer

The invention discloses a low-noise passive frequency mixer. The low-noise passive frequency mixer comprises a low-noise transconductance amplifier stage, a switch frequency mixing stage and a transimpedance amplifier stage. The low-noise transconductance amplifier stage mainly adopts a cross coupling master-slave noise cancellation technology, a main transconductance conduit adopts a cross coupled structure to double an equivalent transconductance value, an appropriate transconductance value is provided through the main transconductance conduit and the noise of the main transconductance conduit is lowered through a master-slave structure; the switch frequency mixing stage is used for modulating and filtering radiofrequency currents output from the low-noise transconductance amplifier stage and outputting intermediate frequency currents; the transimpedance amplifier stage consists of a full-differential operational transconductance amplifier and a load resistor; the operational transconductance amplifier is based on a feed-forward compensation technology, and a consequent pole point in a transfer function of the amplifier is offset by a zero point introduced to a feed-forward stage of the operational transconductance amplifier, so that a large unity-gain bandwidth is achieved; the load resistor is used for converting the intermediate frequency currents into intermediate frequency voltage signals which are then output, by virtue of a voltage-current negative-feedback connection way. The low-noise passive frequency mixer has the characteristics of low noise, high gain and low power consumption.
Owner:SOUTHEAST UNIV

Low dropout linear regulator, method for improving stability of low dropout linear regulator and phase-locked loop

The embodiment of the invention discloses a low dropout linear regulator, a method for improving the stability of the low dropout linear regulator and a phase-locked loop. The low dropout linear regulator comprises a reference voltage source, an error amplifier, an adjustment circuit, a load, a first compensating circuit and a second compensating circuit. The first compensating circuit is coupled with the adjustment circuit and used for adjusting a dominant pole and a secondary dominant pole of the low dropout linear regulator to adjust the phase margin. The second compensating circuit is used for adjusting the dominant pole of the low dropout linear regulator on the basis that the dominant pole and the secondary dominant pole of the low dropout linear regulator are adjusted by the first compensating circuit, further increasing the secondary dominant pole to adjust the phase margin and adjusting the gain bandwidth product of the low dropout linear regulator. By means of the low dropout linear regulator, the value of the gain bandwidth product and the dominant pole can be remarkably reduced, the secondary dominant pole can be increased, and therefore the error amplifier has the better noise performance.
Owner:HUAWEI TECH CO LTD

Enhanced fiber nodes with cmts capability

Enhanced Cable Modem Termination System (CMTS) functionality, including programmable digital domain modulators and demodulators for dynamic channel assignment, is incorporated into Fiber Nodes (FNs) or mini Fiber Nodes (mFNs), yielding enhanced Fiber Nodes (eFNs). These eFns distribute CMTS functionality deep into Hybrid-Fiber-Coax Networks (HFCN) rather than centralizing the CMTS functions within a single location. Moving the cable modem terminations closer to the subscribers shortens the analog RF paths required to support cable modems. Communication of both subscriber data and CMTS control data is performed over Ethernet-compatible packet networks between the field-based CMTSs and an upstream facility (e.g., the Head End), which includes an Internet gateway. Packet data for multiple subscriber cable modems is easily compressed and merged over common network paths, reducing cabling plant complexity and increasing bandwidth utilization. This approach dramatically reduces the infrastructure cost per cable modem. Distributing CMTS functionality among multiple eFNs also reduces demands on already stretched resources at the Head End for space, power, and HVAC. For HFCN channels containing signals with modulation or encoding schemes that are unknown or best processed upstream, the invention also provides for tunneling their spectrum over the same packet network as used for the cable modem data. The channels to he tunneled are isolated using digital receivers, translated to baseband, their data framed, merged with cable modem subscriber data, and transmitted over the packet network. Upstream, the framed channel data is parsed and the original channel spectrum reconstructed to permit information recovery.
Owner:JUMIPER NETWORKS INC
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