An aspect includes a direct digital synthesis system including a waveform generator with a waveform memory operable to store a plurality of waveform vectors and output a selected waveform vector. The direct digital synthesis system also includes a digital-to-analog converter operable to convert the selected waveform vector from a digital value to an analog signal responsive to a reference clock. The direct digital synthesis system further includes a controller operable to maintain phase continuity of the analog signal when an output of the analog signal is interrupted and restored.

The present invention relates to a design technology of a phase locked loop (PLL) for generating an accurate clock frequency in a clock synchronization system. The present invention suggests a new structure based on a hardware description language (HDL), and thus reduces a chip area of a frequency synthesizer while obtaining a wide frequency operation range. Furthermore, since only the HDL is used, the entire frequency synthesizer becomes all-synthesizable, and auto layout (auto P&R) can be achieved through a tool, which makes it possible to reduce a design cost of a designer.

An aspect includes a direct digital synthesis system including a waveform generator with a waveform memory operable to store a plurality of waveform vectors and output a selected waveform vector. The direct digital synthesis system also includes a digital-to-analog converter operable to convert the selected waveform vector from a digital value to an analog signal responsive to a reference clock. The direct digital synthesis system further includes a controller operable to maintain phase continuity of the analog signal when an output of the analog signal is interrupted and restored.

A test and measurement instrument including a digital-to-analog converter having an output sample rate configured to receive a digital sample waveform and a reference clock and output an analog waveform at the sample rate, a waveform synthesizer configured to receive an input waveform having a baud rate and output a digital sample waveform having a baud rate less than the sample rate of the digital-to-analog converter, and a port configured to output the analog waveform.

An apparatus includes a digital frequency synthesizer (DFS). The DFS includes a time-to-digital converter (TDC) to provide an output signal that represents a phase difference between a reference signal and a feedback signal. The DFS further includes a scaling circuit, which has an adaptively changed gain, to provide a scaled residue signal used to cancel an effect of the residue signal in the DFS.

A frequency synthesis system includes a memory to store first and second digital control word pairs that each include a first and second control word. A first DAC system generates an analog sampling signal having a first sampling frequency based on a fixed clock signal and the first control word of the first pair during a first time duration having a second sampling frequency based on the first control word of the second pair during a second time duration. A second DAC system generates an analog output signal based on the second control word of the first pair and the first sampling frequency at the first time duration and based on the second control word of the second pair and the second sampling frequency at the second time duration. The analog output signal has a same predetermined output frequency at both the first and second time durations.

A direct digital synthesizer (DDS) is controlled by a suitably configured programmable logic device (PLD). The DDS includes a digital analog converter (DAC), and a coupled driver/buffer configured to drive relatively high capacitive loads with substantially rail to rail sinusoidal driver output signals and with little to no waveform distortion. The DAC includes a PMOS and NMOS DACs, and a switch configured to select the PMOS DAC for negative portions and the NMOS DAC for positive portions of an output analog signal generated by the DAC. The driver includes a pair of input differential amplifiers, PMOS and NMOS structures, which may be variable, and a pair of variable current sources. The PLD controls variable elements of the DDS to adjust the achievable positive and negative slew rates of the DDS, independently of one another, to reduce or eliminate risk of signal distortion while maintaining substantially stable rail to rail output.

The present invention relates to a design technology of a phase locked loop (PLL) for generating an accurate clock frequency in a clock synchronization system.

The present invention suggests a new structure based on a hardware description language (HDL), and thus reduces a chip area of a frequency synthesizer while obtaining a wide frequency operation range.

Furthermore, since only the HDL is used, the entire frequency synthesizer becomes all-synthesizable, and auto layout (auto P&R) can be achieved through a tool, which makes it possible to reduce a design cost of a designer.

One embodiment includes a clock distribution system. The system includes a standing-wave resonator configured to receive and to resonate a sinusoidal clock signal. The standing-wave resonator includes at least one anti-node portion associated with a peak current amplitude of the sinusoidal clock signal. The system also includes at least one clock line interconnecting each of the at least one anti-node portion and an associated circuit. The at least one clock line can be configured to propagate the sinusoidal clock signal for timing functions associated with the associated circuit.

An FM-CW radar includes a high frequency circuit that receives a reflected wave from a target, and a signal processing unit that converts an analog signal generated by the high frequency circuit into a digital signal and detects at least a distance to the target and velocity of the target. The high frequency circuit includes a VCO that receives a modulation voltage from the signal processing unit and generates a frequency-modulated high frequency signal. The signal processing unit includes an LUT that stores default modulation control data. The signal processing unit calculates frequency information from phase information of output of the VCO, and updates the data stored in the LUT with correction data that is generated by using a result of the calculation.