351 results about "Low jitter" patented technology

A method for allocating a processing resource among multiple inputs includes defining a sequence of multiplexing iterations, each such iteration including a first plurality of windows, each such window containing a second plurality of time slots. A respective weight is assigned to each of the inputs, and each of the inputs is allotted one of the time slots in each of a respective number of the windows in each of the iterations, the respective number being determined by the respective weight. Each of the inputs is then provided with access to the processing resource during the time slots allotted thereto.

A clock generator has a clock generating circuit, a phase difference detection circuit, and a control signal generating circuit. The clock generating circuit has a function for varying a clock phase in accordance with a control signal, the phase difference detection circuit compars the clock phase output from the clock generating circuit with a phase of a reference waveform, and detecting a phase difference therebetween, and the control signal generating circuit generates a control signal for controlling the clock phase of the clock generating circuit, based on phase difference information obtained from the phase difference detection circuit. The phase difference detection circuit has a plurality of phase detection units, at least one of the plurality of phase detection units carries out a direct phase detection in which a phase of the clock is directly compared with the phase of the reference waveform, and at least the other one of the plurality of phase detection units carries out an indirect phase detection using a phase-synchronized waveform generating circuit generating a waveform synchronized in phase with the reference waveform or an output of the clock generating circuit and a phase information extracting circuit extracting phase information from the phase-synchronized waveform.

A clock recovery circuit includes a first phase detector for measuring the phase difference between a first clock signal from a voltage controlled oscillator (VCO) and a data signal. A phase shifter responsive to a control signal based on this phase difference adjusts the phase of an incoming clock signal to yield a second clock signal. The phase difference between the first clock signal and the second clock signal is measured and the resulting signal is low-pass filtered to derive a control signal for controlling the VCO. The phase locked loop including the VCO filters out jitter.

A system and method of transmitting a data stream from a data source over a baseband wireless communication system to one or more receivers. The receivers simultaneously recover the data and clock signals of the original data stream from the wireless transmitted data so that the data stream can be provided by the receivers to a data sink at the same rate as the original data stream, with low jitter performance.

The invention discloses a high-precision time interval measurement method based on phase modulation. Under the control of digital clock phase-shift, a path of high-frequency and low-jitter clock is transformed to N paths of clock signals having same frequency and fixed phase difference, and is taken as a counter reference clock; a counter is driven to count respectively in N paths of clock periods; two paths of clock signals, which have the smallest error, are extracted by utilizing the clock phase information; through the combination with the clock period and the counted values, the measurement valve of the time interval is worked out. Compared with the method using a single clock for counting, the high-precision time interval measurement method effectively reduces the measurement principle error, and can improve the measurement resolution ratio to 1/n of the reference clock. A measurement device is connected with a signal conditioning module, an FPGA module, a singlechip module and a display circuit module sequentially according to the signal processing order, and realizes high measurement precision, high measurement resolution ratio, high measurement speed, real time display, and stable and reliable work under a certain crystal oscillation frequency; and the integration in the FPGA is easy, and the expansion is flexible. The high-precision time interval measurement method can be used for measuring the speed in a high-speed motion.

The influence of a jitter of a sampling clock of an analog-to-digital converter is digitally corrected at low power consumption.

The sampling clock of the analog-to-digital converter is generated by a phase locked loop (PLL) using a reference clock, which has a lower frequency and lower jitter than the sampling clock, as a source oscillation. A time-to-digital converter (TDC) converts a timing error at a timing where the sampling clock and the reference clock are synchronized with each other into a digital value. Incidentally, a timing error at a sampling timing where the reference clock is not present is generated by interpolating a detected timing error. Thus, a jitter value of the sampling clock at each sampling timing is obtained. A sampling voltage error is calculated from the jitter value and the output of the analog-to-digital converter is digitally corrected.

A cascaded phase-locked loop (PLL) clock generation technique reduces frequency drift of a low-jitter clock signal in a holdover mode. An apparatus includes a first PLL circuit configured to generate a control signal based on a first clock signal and a first divider value. The apparatus includes a second PLL circuit configured to generate the first clock signal based on a low-jitter clock signal and a second divider value. The apparatus includes a third PLL circuit configured to generate the second divider value based on the first clock signal, a third divider value, and a second clock signal. The low-jitter clock signal may have a greater temperature dependence than the second clock signal and the second clock signal may have a higher jitter than the low-jitter clock signal.

The clock generating portion of a communication system includes a low-power, high-jitter phase locked loop (PLL) and a high-power, low-jitter PLL. Control logic within the chip allows for selective switching between the low-power and high-power PLL for receiving the broadcast signals, such as mobile TV signals. The switching may occur in a manner that is dependent on the conditions of the wireless channel and/or the complexity of the modulation scheme being used. The switching may be used to provide an oscillating signal from one or both of the PLLs to a receiver to be used to receive communication signals. The control logic may power off one of the PLLs to save power when not in use.

A multi-Gigahertz, low jitter phase locked loop (PLL) with adjustable gain is disclosed. In one embodiment, properties of a f_VCO signal of a PLL can be acquired. Properties can include the occurrences of different types of jitter on the f_VCO signal and the lock status of the PLL. A gain control module can control at least a portion of the PLL based on an analysis of the acquired properties. For example, when the loop is locked or when there is loop filter leakage, the gain of a charge pump in the PLL can be reduced. When a charge pump mismatch is detected based on the acquired properties, additional control signals can be provided to the charge pump to correct the mismatch.

At a first step, in a synchronous clock generation circuit, the number of delay stages serving as a digital PLL circuit is increased/decreased, and an oscillation circuit performs an oscillation operation when an optimal number of delay stages is set. Thereafter, in an operation at a second step, a control voltage is controlled with the optimal number of delay stages being set for serving as an analog PLL circuit, thereby attaining a lock-in state. As the lock-in state is finally maintained under analog control, an excellent jitter characteristic can be obtained. Thus, ensuring a lock-in range that has been a problem in the analog PLL circuit is solved by varying the number of delay stages in the operation at the first step, and a high jitter characteristic that has been a problem in a digital PLL circuit can be solved by analog control in the operation at the second step.

The invention relates to a field programmable gate array (FPGA) based high-speed analog-digital converter (ADC) synchronous acquisition system, comprising an FPGA based signal processing platform and a high-speed ADC synchronous acquisition daughter board. A clock signal for ADC acquisition, a control signal and date collected by the ADC on the high-speed ADC synchronous acquisition daughter board are transmitted to the FPGA based signal processing platform, and the FPGA based signal processing platform performs subsequent signal processing; the high-speed ADC synchronous acquisition daughter board comprises an ultralow jitter synchronous clock generation circuit, a power supply module, and a plurality of high-speed ADC acquisition circuits; and the front end of each high-speed ADC acquisition circuit is connected with a broadband signal conditioning circuit. Synchronous sampling is performed on the ADC between different channels through a multichannel ADC synchronization technology; the ultralow jitter synchronous clock generation circuit generates multichannel low jitter clocks meeting high-speed ADC signal to noise ratio and synchronism requirements; due to adoption of the two-stage alternating current coupling broadband signal conditioning circuit, the high-speed ADC acquisition circuit can collect middle frequency signals with input frequency between 10kHz and 700MHz; and the power supply module adopts a low noise power supply design.

An adjustable level shifter with native and kicker transistors is provided. The level shifter provides high switching speeds, adjustable output voltage levels, and low jitter. The level shifter has first and second thick-oxide p-channel metal-oxide-semiconductor (PMOS) transistors, first and second thick-oxide native n-channel metal-oxide-semiconductor (NMOS) transistors, and first and second thin-oxide NMOS transistors. The first PMOS transistor, first native transistor, and first NMOS transistor are connected in series and the second PMOS transistor, second native transistor, and second NMOS transistor are connected in series. An input data signal and an inverted version of the input data signal drive the gates of the thin-oxide NMOS transistors. A node located between the first PMOS transistor and first native transistor is connected to an output data terminal. The kicker transistor is connected in parallel with the first PMOS transistor.

A low jitter digital frequency synthesizer includes a first counter module, a second counter module, a snapshot module, an error value generation module, and a tapped delay line. The first counter module counts intervals of M cycles of an input clock to produce a first count. The second counter module count intervals of D cycles of an output clock to produce a second count, wherein a rate of the output clock corresponds to M/D times a rate of the input clock. The snapshot module periodically takes a snapshot of the first and second counts to produce snapshots. The error value generation module generates an error value based on the snapshots. The tapped delay line module produces the output clock based on the error value.

Techniques for enabling broadband data rates at mobile terminals in a beyond-line-of-sight communication system are disclosed. Forward link time-diversity transmission methods and a time-diversity transmitter based upon blockage characteristics are provided. The transmitter optionally supports selective time-diversity and can operate at Ku-band or higher frequencies. A forward link time-diversity receiver and methods for receiving a forward link time-diversity signal are also disclosed. The forward link time-diversity receiver optionally provides low-jitter or low-delay characteristics. A return link transmitter and return link transmit methods which avoid blockages are also disclosed. The return link transmitter can include a signal presence detector and blockage prediction filter.

The present invention is a remote input analog-to-digital conversion (ADC) system. The system may generate low jitter, short duration optical pulses to allow for high performance sampling of an antenna signal at a remote end of the system. The system may utilize phase modulation and IQ demodulation (with a reference optical pulse stream) using separate analog-to-digital converters for I and Q to overcome linearity limitations. Low sampling rate analog-to-digital converters may be utilized by the system by using parallel, low optical pulse repetition rate paths and/or optical demultiplexer switching trees. The system is an optical fiber system.

The invention discloses an ultrahigh-speed low-jitter multi-phase clock circuit. The circuit comprises an input clock recovery and duty ratio adjustment module, a phase discriminator module, a charge pump and loop filter module, a variable delay line module, a clock offset error calibration module and a frequency division module, wherein the phase discriminator module is used for detecting a phase relationship between a reference clock and a feedback clock, and correspondingly outputting an 'UP' or 'Down' pulse level to the charge pump; and the charge pump and a loop filter are used for converting pulses output by a phase discriminator into a low-frequency direct-current control level, and controlling the delay amount of a delay chain to adjust a phase difference between the two clocks; when the two clocks are synchronized, the phase discriminator outputs a locking signal; a variable delay line is constructed by serial connection of a plurality of same sub-delay units in order to obtain a multi-phase clock; and the clock offset error calibration module is used for reducing a clock offset error by adopting a multi-phase clock circuit matching calibration technology. The clock signal can meet strict requirements on clock signals in high-frequency applications.

A circuit for generating an output oscillation signal with low jitter includes an oscillator to generate an oscillation signal at an initial frequency based upon a control input to vary an amplitude of the oscillation signal. A first frequency multiplier multiplies the oscillation signal to result in a first signal with first frequency and first undesired frequency components. A filter minimizes the first undesired frequency components of the first signal. A second frequency multiplier multiplies the first signal to result in the output oscillation signal with second frequency and second undesired frequency components. A second feedback circuit compares a predetermined range and at least one of the first signal and the output oscillation signal to result in a reference value. A first feedback circuit varies the control input based upon a comparison between the reference value and the amplitude of the oscillation signal to minimize the second undesired frequency components.