Abstract:
Techniques are provided for phase coherent frequency synthesis. An embodiment includes a first phase accumulator to accumulate a frequency control word (FCW) at a clocked rate to produce a first digital phase signal representing phase data corresponding to phase points on a first sinusoidal waveform. The embodiment also includes a second phase accumulator to produce an incrementing reference count at the clocked rate and multiply it by the FCW to produce a second digital phase signal representing phase data corresponding to phase points on a second sinusoidal waveform. The multiplication is performed in response to change in the FCW. The embodiment further includes a multiplexer to select between the first and second digital phase signals based on completion of the multiplication. The embodiment also includes a phase-to-amplitude converter to generate digital amplitude data corresponding to the phase points on a sinusoidal waveform associated with the selected digital phase signal.
Abstract:
A phase coherent fractional-N phase-locked loop synthesizer for maintaining phase coherence of a synthesized frequency includes a phase coherent delta-sigma modulator (DSM) having a plurality of feed-forward accumulator stages. The DSM is operatively coupled to a reference clock configured to generate a cyclical reference signal. The DSM configured to count a number of cycles of the reference signal, to cause, at each cycle of the reference signal, each of the stages of the DSM to accumulate a sum of a previous stage of the DSM, and to multiply each sum by a fractional divide word to produce a multiplier output, thereby causing the DSM to output a sequence of signals that tracks with the reference clock.
Abstract:
A signal routing circuit is disclosed which employs resistive combiners to reduce signal jitter. A signal routing circuit configured according to an embodiment comprises an input stage including a plurality of buffer circuits. Each of the buffer circuits is controlled by a selection signal to enable an input signal at an input port of the buffer circuit to generate an output signal at an output port of the buffer circuit. The signal routing circuit also includes a plurality of resistors to couple the output port of each of the buffer circuits of the input stage to a summing junction. The signal routing circuit further includes an output stage including an additional buffer circuit. The input port of the additional buffer circuit is coupled to the summing junction, and the output port of the additional buffer circuit is configured to provide the routed output signal based on the selection signals.
Abstract:
Frequency divider techniques are disclosed which can be used to address two problems: when an incorrect division occurs if the modulus control changes before the divide cycle is complete, and when an incorrect division occurs due to a boundary crossing (e.g., power-of-2 boundary crossing in a fractional-N PLL application). In one embodiment, a frequency divider is provided comprising a plurality of flip-flops operatively coupled to carry out division of an input frequency, and configured to generate a modulus output and receive a divided clock signal of a previous cell. An additional flip-flop is selectively clocked off one of the modulus output or the divided clock of the previous stage, depending at least in part on a Skip control signal applied to a data input of the additional flip-flop, and is further configured to selectively reset the plurality of flip-flops to a state that will result in a correct divide ratio.
Abstract:
A direct digital synthesizer (DDS) circuit. The circuit includes a first input to receive a first fixed frequency clock signal having a first frequency, a second input to receive a second fixed frequency clock signal having a second frequency lower than the first frequency, and an output to provide an output frequency that is based at least in part on a frequency control word (FCW). The DDS circuit may include a frequency correction circuit having a first input to receive the first clock signal, a second input to receive the second clock signal, and a third input to receive the FCW, and an output to provide a frequency error of the first clock signal, the frequency error determined using the second clock signal and FCW. Alternatively, or in addition to, the DDS circuit may include an all-digital phase lock loop to correct for frequency wander of the first clock signal.
Abstract:
Techniques are provided for a switched output digital to analog converter employing an N-path cascode output switch. An example system may include a plurality of cascode transistors coupled in parallel to an output stage of a current mode digital to analog converter (DAC) circuit. The system may also include a plurality of control ports, each of the control ports coupled to a gate of one of the cascode transistors. The system may further include a plurality of output ports, each output port coupled to one of the cascode transistors. The cascode transistors are configured to switch the output stage of the DAC to the output port of the transistor in response to a routing control signal applied to the control port of the transistor. The cascode transistors are High Electron Mobility Transistors (HEMT) fabricated from Gallium Nitride.
Abstract:
Techniques are provided for a switched output digital to analog converter employing an N-path cascode output switch. An example system may include a plurality of cascode transistors coupled in parallel to an output stage of a current mode digital to analog converter (DAC) circuit. The system may also include a plurality of control ports, each of the control ports coupled to a gate of one of the cascode transistors. The system may further include a plurality of output ports, each output port coupled to one of the cascode transistors. The cascode transistors are configured to switch the output stage of the DAC to the output port of the transistor in response to a routing control signal applied to the control port of the transistor. The cascode transistors are High Electron Mobility Transistors (HEMT) fabricated from Gallium Nitride.
Abstract:
A clock distribution and alignment system includes at least three clock generators, each including a clock receiver circuit to receive a first clock signal having a first frequency, and a clock divider circuit to divide the received first clock signal into a second clock signal having a second frequency lower than the first frequency, each of two or more of the clock generators further including a phase detector circuit to compare the phase of the second clock signal with the phase of the second clock signal for a next one of the clock generators, and a clock adjuster circuit to adjust the phase of the received first clock signal based on the compared phases of the second clock signals. In some cases, the clock adjuster circuit is further to align the phases of the second clock signals to within a predefined tolerance of each other.
Abstract:
A direct digital synthesizer (DDS) circuit. The circuit includes a first input to receive a first fixed frequency clock signal having a first frequency, a second input to receive a second fixed frequency clock signal having a second frequency lower than the first frequency, and an output to provide an output frequency that is based at least in part on a frequency control word (FCW). The DDS circuit may include a frequency correction circuit having a first input to receive the first clock signal, a second input to receive the second clock signal, and a third input to receive the FCW, and an output to provide a frequency error of the first clock signal, the frequency error determined using the second clock signal and FCW. Alternatively, or in addition to, the DDS circuit may include an all-digital phase lock loop to correct for frequency wander of the first clock signal.
Abstract:
Techniques are provided for phase coherent frequency synthesis. An embodiment includes a first phase accumulator to accumulate a frequency control word (FCW) at a clocked rate to produce a first digital phase signal representing phase data corresponding to phase points on a first sinusoidal waveform. The embodiment also includes a second phase accumulator to produce an incrementing reference count at the clocked rate and multiply it by the FCW to produce a second digital phase signal representing phase data corresponding to phase points on a second sinusoidal waveform. The multiplication is performed in response to change in the FCW. The embodiment further includes a multiplexer to select between the first and second digital phase signals based on completion of the multiplication. The embodiment also includes a phase-to-amplitude converter to generate digital amplitude data corresponding to the phase points on a sinusoidal waveform associated with the selected digital phase signal.