Abstract: An example system includes: interleaving circuitry including a data input, a plurality of data outputs, and a plurality of clock inputs, the data input coupled to the received data input and each of the plurality of clock inputs coupled to one of the plurality of receiver clock outputs; and handoff circuitry coupled to the interleaving circuitry, the handoff circuitry including: comparison circuitry coupled to the clock generation circuitry and configured to compare the plurality of receiver clocks to the transmission clock; clock configuration circuitry coupled to the comparison circuitry and configured to select one of the plurality of receiver clocks based on the comparison circuitry; and a plurality of flip-flops coupled to the clock configuration circuitry and configured to convert the plurality of data outputs from the plurality of receiver clocks to the transmission clock to generate a plurality of transmission data streams based on the one of the plurality of receiver clocks selected by the clock conf

Abstract: A phase detection circuit includes an edge trigger circuit and a duty detection circuit. The edge trigger circuit generates a reference pulse signal and a comparison pulse signal based on a target clock signal and at least two clock signals having phases adjacent to the phase of the target clock signal. The duty detection circuit generates a phase detection signal by detecting the duty ratio of the reference pulse signal and the comparison pulse signal.

Abstract: A virtual time control apparatus, method, and non-transitory computer readable storage medium thereof are provided. The virtual time control apparatus includes a system timer, a real time clock, and a processing unit, wherein the processing unit is electrically connected to the system timer and the real time clock. The system timer has an original timer period, while the real time clock has an original tick period. The processing unit executes a hypervisor. The hypervisor generates a virtual timer period according to an adjustment ratio and the original timer period. The hypervisor generates a virtual tick period according to the adjustment ratio and the original tick period.

Abstract: A phase-frequency detector (PFD) circuit that includes a binary phase detector and a ternary phase detector coupled to the binary phase detector. The binary phase detector is configured to, based on the PFD circuit being in a frequency acquisition state, compare a clock signal with a data signal and output up and down signals based on the comparison. The binary phase detector is also configured to be disabled based on the PFD circuit being in a frequency locked state. The ternary phase detector is configured to compare the clock signal with the data signal and output up, down, and hold signals based on the comparison.

Abstract: A timing signal generation circuit includes: a phase comparison circuit to detect a phase difference between an input signal and a recovery clock; a control voltage signal generation unit to generate two phase differential control voltage signals, based on the detected phase difference; a timing detection circuit to detect timing in which the control voltage signals are inverted, and generate quadrant information of the phase difference of the control voltage signals and an inverted timing signal; a synthesized phase selection circuit to select clocks of two phases which are used for phase interpolation for each predetermined angle, from clocks of a plurality of phases, and generate a phase control signal for the phase interpolation, based on the control voltage signals and the quadrant information; and a phase synthesis circuit to generate the recovery clock by synthesizing the selected clocks of two phases, based on the phase control signal.

Abstract: An apparatus for synchronizing an incoming signal with a clock signal comprises two or more synchronizer circuits, wherein each synchronizer circuit receives the incoming signal and the clock signal. Each synchronizer circuit generates a synchronized signal, wherein the state of each synchronized signal changes on a different phase of said clock signal in response to a change of the state of said incoming signal. A decision mechanism circuit receives the synchronized signals generated by each synchronizer circuit, wherein the decision mechanism circuit determines the output signal in response to the change of the state of the incoming signal. The decision mechanism circuit further comprises a memory element having a state which is set according to a previously detected state of said signal, wherein the output signal is determined according to the state of the memory element.

Abstract: The present invention discloses a phase interpolating apparatus comprising: a first signal generation circuit, configured for generating a first signal having a first phase; an optional second signal generation circuit, configured for generating a second signal having the first phase; a third signal generation circuit, configured for generating a third signal having a second phase; a fourth/fifth signal generation circuit, configured for generating a fourth signal having a third phase when operating in a first mode and for generating a fifth signal having the second phase instead of the fourth signal when operating in a second mode; and a phase interpolator, configured for generating an interpolated signal without utilizing the fourth signal when operating in the first mode and for generating the interpolated signal according to the first signal, the third signal, and the fifth signal when operating in the second mode.

Abstract: A signal transmission circuit includes a first selection driver configured to generate a first drive signal in response to an input signal and a first selection signal and drive a transmission signal in response to the first drive signal, and a second selection driver configured to delay the input signal by a first delay time to generate a first delay signal. The second selection driver generates a second drive signal in response to the first delay signal and a second selection signal, generates a first code signal in response to the input signal and the second selection signal, and drives the transmission signal in response to the second drive signal and the first code signal.

Abstract: A method for signal phase calibration includes providing multiple periodic clock signals, including a reference signal and multiple phase shifted versions of the reference signal. The signals have a common frequency and are shifted from one another by multiples of a phase offset. An edge of a first signal is detected. The first signal is one of multiple phase shifted versions of the reference signal. The edge is a transition from a first logic value to a second logic value. The second logic value of the first signal is compared, upon detection of the edge, to a logic value of a second signal that is one of the first plurality of periodic clock signals other than the first signal. An inversion of the first signal is selectively provided based on an outcome of the comparison.

Abstract: A clock synchronization system and method avoids output clock jitter at high frequencies and also achieves a smooth phase transition at the boundary of the coarse and fine delays. The system may use a delay line configured to generate two intermediate clocks from the input reference clock and having a fixed phase difference therebetween. A phase mixer receives these two intermediate clocks and generates the final output clock having a phase between the phases of the intermediate clocks. The shifting in the delay line at high clock frequencies does not affect the phase relationship between the intermediate clocks fed into the phase mixer. The output clock from the phase mixer is time synchronized with the input reference clock and does not exhibit any jitter or noise even at high clock frequency inputs.

Abstract: A data receiver identifies an alignment symbol in a parallel data stream including encoded symbols, generates a bit order indicator indicating a bit order of the alignment symbol identified in the parallel data stream, and generates a symbol stream including the encoded symbols. Further, the data receiver decodes symbols in the symbol stream and generates a bit polarity indicator indicating a bit polarity of the parallel data stream based on the decoded symbols. Additionally, the data receiver generates a formatted symbol stream having a predetermined bit order and a predetermined bit polarity, based on the symbol stream, the bit order indicator, and the bit polarity indicator. In some embodiments, the data receives a serial data stream and generates the parallel data stream by deserializing data in the serial data stream.

Abstract: A phase rotator includes a phase selector stage operative to receive a clock signal and output a first phase and a second phase of the clock signal, a slew rate control stage including a first pass gate circuit operative to control a slew rate of the first phase of the clock signal and a second pass gate circuit operative to control a slew rate of the second phase of the clock signal, and a phase blending stage operative to combine the first phase with the second phase of the clock signal and output a phase rotated signal.

Abstract: A dynamic phase alignment circuit includes a phase generator circuit having delay-locked loop circuits that generate periodic output signals. Each of the delay-locked loop circuits generates one of the periodic output signals in response to at least two periodic input signals. A multiplexer circuit selects a selected periodic signal from among the periodic input signals and the periodic output signals based on select signals. A phase detection circuit compares a phase of the selected periodic signal to a data signal to generate a phase detection signal. A control logic circuit generates the select signals. The control logic circuit adjusts the select signals based on changes in the phase detection signal to cause the multiplexer circuit to adjust the phase of the selected periodic signal.

Abstract: An AC-coupling phase interpolator and a DLL using the same are provided. The AC-coupling phase interpolator includes a coupling capacitor generating and outputting a coupling signal by AC-coupling to an interpolation signal obtained by phase-interpolating an input signal. Thereby, it is possible to correct duty of an input signal and adjust the level of an output signal.

Abstract: A linear phase detector includes an up/down pulse generator operating in response to received data signals and a recovered clock signal. The phase detector generates up and down pulses that have pulse widths proportional to the phase differences between transitions of the received data signals and edges of the recovered clock signal. By generating up and down pulses using a linear phase detector in proportion to a phase error, data signals are effectively recovered, even data signals with significant jitter.

Abstract: A bicycle control system is provided with a switch device and a cycle computer. The switch device includes a switch operation member, a sensor arranged relative to the switch operation member to detect operation of the switch operation member, a processing unit operatively coupled to the sensor and a transmitter arranged to transmit an output signal. The processing unit of the switch device includes an identification code generating member, an operating signal generating member and an output member. The identification code generating member generates identification code related to identification of the switch device. The operating signal generating member generates an operation code indicative of operation of the switch operation member. The output member combines the identification code and the operation code as the output signal to be transmitted by the transmitter of the switch device.

Abstract: A method of generating an output signal from an input signal includes a step of generating a set of n signals, n being an integer greater than or equal to 3, by generating a signal for each integer i such that 0?i?(n?1), each signal within the set having the same frequency and approximately equal amplitude and a phase equal to (360/n)i degrees. The method also includes a step of inputting each of the set of n signals to a gate terminal of a corresponding one of a set of n transistors. Each of the transistors has a source terminal electrically connected to a common voltage drain and each of the transistors has a drain terminal electrically connected to a coupling. The coupling is electrically connected to a common voltage source. The output signal at the coupling has a frequency equal to the frequency of the input signal multiplied by n.

Abstract: A technique includes providing transmitters that are each associated with a data bit line of a bus, and each transmitter is clocked by an associated transmit clock signal. The technique includes determining a baseline offset to apply to a base clock signal to synchronize the base clock signal to a source clock signal of a source that supplies data to the transmitters. For each transmitter, an associated phase offset is determined to compensate for an associated skew. The phase of each transmit clock signal is controlled based on the associated phase offset and the baseline offset.

Abstract: A time delay circuit is disclosed and includes a delay line with a first delay circuit and at least a second delay circuit connected downstream. An interpolation circuit is used to generate intermediate signals derived by delayed successive signals in the delay line.

Abstract: Various embodiments provide a Phase Interpolator (PI) that receives input clocks, and outputs intersymbol interference-equalized, phase-shifted output clocks. In one embodiment, the Phase Interpolator comprises two PI Conditioners and a PI Mixer. In one embodiment, a PI Conditioner receives input clocks and is controlled by a different phase-shifted input clock by using a suitable circuit element, such as a flip-flop. Collectively, the input clock-controlled PI Conditioner and Mixer act in concert to control the band limiting effect of the PI Conditioner which, in turn, equalizes intersymbol interference.

Abstract: A time delay circuit is disclosed and includes a delay line with a first delay circuit and at least a second delay circuit connected downstream. An interpolation circuit is used to generate intermediate signals derived by delayed successive signals in the delay line.

Abstract: A phase interpolation circuit and method are provided that are capable of operating in a low voltage and capable of generating a substantially exact phase-interpolation signal, where the phase interpolation circuit is configured to output a phase interpolation signal having a phase between phases of at least two input signals and comprises an interpolation unit configured to discharge an output node by a first interpolation control signal in case a first input signal of two input signals having different phases is inputted to the interpolation unit when the output node has been precharged to a power supply voltage level, the interpolation unit additionally discharging the output node by a second interpolation control signal in case of input of a second input signal of the two input signals; a comparison unit for comparing a reference voltage level and a voltage level of the output node of the interpolation unit to output a signal corresponding to the comparison; and a short pulse generation unit for generatin

Abstract: A phase interpolator circuit may comprise a multiplexer circuit (MUX) to receive a plurality of clock signals at MUX inputs and to output a first clock signal and a second clock signal that are out of phase with each other, a digital to analog converter circuit (DAC) to convert a digital input to first and second DAC output currents such that a sum of the first and second DAC output currents comprises a substantially constant current value, and a weighted averager circuit coupled to the MUX and the DAC. The weighted averager circuit may operate to sum weighted first and second clock signals and to output a phase interpolated clock signal. The first clock signal may be weighted according to the first DAC output current and the second clock signal may be weighted according to the second DAC output current. Other apparatus, systems, and methods are disclosed.

Abstract: A phase shift circuit includes a 45° phase corrector that performs vector synthesis of signals supposed to have a 45° phase difference, out of a plurality of sets of orthogonal phase signals having an about 45° phase difference and an equal amplitude, the orthogonal phase signals in each set having undergone 90° phase correction, and outputs signals resulting from the vector synthesis, whereby a phase error between the orthogonal phase signals in the different sets is eliminated by the vector synthesis to make it possible to correct their phase difference to accurately 45°.

Abstract: A phase interpolator circuit may comprise a multiplexer circuit (MUX) coupled to a plurality of clock signals at MUX inputs and may provide a first clock signal and a second clock signal at MUX outputs that are out of phase with each other, a digital to analog converter circuit (DAC) to convert a digital input to first and second DAC current outputs such that a sum of the first and second DAC output currents comprises a substantially constant current value, a weighted averager circuit coupled to the MUX and the DAC, and a variable capacitive load circuit coupled to the first and second DAC current outputs. The weighted averager circuit may operate to sum weighted first and second clock signals and to output a phase interpolated clock signal, wherein the first clock signal is weighted according to a first DAC output current and the second clock signal is weighted according to a second DAC output current. Other apparatus, systems, and methods are disclosed.

Abstract: Circuits, methods, and apparatus for training a phase shift circuit to provide a phase shift for improved data recovery. A specific embodiment of the present invention provides a variable delay cell. A delay through the variable delay cell is changed while training patterns are received. The presence of errors in the received data pattern is tracked, and from the presence or absence of errors a preferred delay is selected and used for receiving data.

Abstract: A steering current generator for a phase interpolator has a multiplicity of fine phase adjustment current sources, each of which is switchable to direct its current to one or other of two summing nodes. The current of each of those two summing nodes is supplemented by respective fixed always-on current sources. The steering current generator has four current outputs and a switching matrix is provided to switch the current from the summing nodes to first and second selected ones of those outputs. The switching matrix is also connected to switch bleed currents to the other two of the current outputs.

Abstract: Methods and apparatus are provided for improving phase switching and linearity in an analog phase interpolator. A phase interpolator in accordance with the present invention comprises (i) a plurality of tail current sources that are activated for substantially all times when the phase interpolator is operational; (ii) at least two pairs of input transistor devices, wherein one pair of the input transistor devices is associated with a minimum phase of the phase interpolator and another pair of the input transistor devices is associated with a maximum phase of the phase interpolator; and (iii) a plurality of current steering switches that provide currents generated by the plurality of tail current sources to one or more of the at least two pairs of input transistor devices, based on an applied interpolation control signal.

Abstract: Circuits, methods, and apparatus for training a phase shift circuit to provide a phase shift for improved data recovery. A specific embodiment of the present invention provides a variable delay cell. A delay through the variable delay cell is changed while training patterns are received. The presence of errors in the received data pattern is tracked, and from the presence or absence of errors a preferred delay is selected and used for receiving data.

Abstract: An improved interpolator includes a replica delay line and an interpolated delay edge generator. The replica delay line provides two replica delay edges to the interpolated delay edge generator. The interpolated delay edge generator selectively generates an interpolated delay edge while maintaining a substantially constant capacitive loading on the two replica delay edges. The replica delay line may comprise a delay cell of four current-starved inverter delay stages or four capacitor-loaded inverter delay stages.

Abstract: A method and circuit for synchronizing an input clock signal with a plurality of internal clock signals in a multiple phase Pulse Width Modulation (PWM) switching power supply without using a Phase Locked Loop (PLL). A period of the input clock signal is measured by using a frequency to voltage converter. A reference capacitor charged by a constant current source is arranged to generate a reference voltage with a slope based on the period of the input clock signal. A change in the reference voltage across the reference capacitor is substantially inversely proportional to a frequency of the input clock. By providing the reference voltage to a sample-and-hold circuit and using an output of the sample-and-hold circuit to feed a comparator, synchronization may be accomplished. Each internal clock signal is generated by different reference capacitor and current source circuit.

Abstract: A delay circuit includes a phase vernier having a plurality of logic components. Each logic component includes a selectable injection input capable of adjusting a phase of an input to the phase vernier.

Abstract: Fine tuned signal phase adjustments are provided by multiple cascaded phase mixers. Each phase mixer outputs a signal having a phase between the phases of its two input signals. With each subsequent stage of phase mixers, the signals generated by the phase mixers have a smaller phase difference, thereby providing finer delay adjustments. Multiple stages of phase mixers can be provided in digital delay-locked loop circuitry to provide additional hierarchical delay adjustment.

Abstract: Phase locked loop circuitry operates digitally, to at least a large extent, to select from a plurality of phase-distributed candidate clock signals the signal that is closest in phase to transitions in another signal such as a clock data recovery (“CDR”) signal. The circuitry is constructed and operated to avoid glitches in the output clock signal that might otherwise result from changes in selection of the candidate clock signal.

Abstract: An apparatus comprising a quadrature network, an RF combining circuit and a weighting network. The quadrature network may be configured to generate a first and a second signal in response to an input signal. The RF combining circuit may be configured to generate an output signal comprising the input signal variably phase shifted from a selectable fixed phase starting point in response to the first signal, the second signal and one or more weighting signals. The weighting network may be configured to generate the weighting signals in response to a voltage control signal and one of four possible output selections. The voltage control signal may be configured to control the variable phase shift.

Abstract: A clock divider circuit and methods of operating same includes a standard integral clock divider circuit and a phase slip non-integral divider circuit for high granularity non-integral clock division. A multi-phase frequency synthesizer produces a plurality of phases of a clock frequency and applies the multiple phases to the divider circuit of the present invention. In a first embodiment, each phase is applied to a phase slip divider circuit which includes a integral divider portion and a programmable phase slip divider portion which receives the output of the integral division portion. Each phase of the input clock may therefore be divided by a wide variety of integral and non-integral divisors. In a second, simpler embodiment, a multi-phase frequency synthesizer produces a plurality of phases and applies the phases to a single phase slip divider.

Abstract: An oscillator generates an oscillation signal, and a phase shifter outputs a phase shift oscillation signal corresponding to a difference between a frequency of the oscillation signal and a target frequency. A multiplier outputs a multiplied signal corresponding to a multiplied value of the phase shift signal and the oscillation signal, and an error signal generator outputs an error signal according to the multiplied signal. The output frequency of the oscillator is controlled according to the error signal.

Abstract: A delay-locked loop (DLL) and a method of performing clock and data recovery. In one embodiment, the DLL includes: (1) a phase detector that generates a phase difference signal based on a phase comparison between a data signal and a mixer output signal of the DLL and (2) a quadrant controller, coupled to the phase detector, that generates first and second voltage control signals based on the phase difference signal and first and second voltage control signals of the DLL.

Abstract: A method for dividing a high frequency clock signal for analysis of all clock edges has been developed. The method includes receiving a high frequency clock signal and dividing it up into multiple phases that represent respective edges of the clock signal. The initial phases are generated by the divider with each subsequent phase lagging its preceding phase by one clock cycle. Additional subsequent phases are generated by inverting corresponding initial phases.

Abstract: The delay signal generating apparatus according to the present invention for outputting a delay signal obtained by delaying a reference signal includes: a phase shift device capable of outputting a plurality of shift signals having phases shifted from a phase of the reference signal by different shift amounts, respectively; and a shift signal selector capable of selecting one of the shift signals that has a phase shifted by a predetermined shift amount and outputting the selected shift signal.

Abstract: A clock control circuit includes a multiphase clock generating circuit receiving an output signal of a input buffer for generating multiphase clocks; a selector circuit receiving multiphase clocks output from the multiphase clock generating circuit for selecting one of the multiphase clocks; a first variable delay circuit for delaying the output of the selector circuit; a clock buffer dummy receiving the output signal of the variable delay circuit ; a phase comparator circuit for detecting a phase difference between an output from the multiphase clock generating circuit and an output of the clock buffer dummy; and a filter for smoothing the output of the phase comparator circuit. The first variable delay circuit has its delay time varied by the output of the filter.

Abstract: A source (20) provides an input signal (S1) to be phase shifted and a combining circuit (24) concurrently combines first (A), second (B) and third (C) intermediate signals derived from the input signal (S1), and having differing phase shifts (0, −45, +135 deg), to form a phase shifted output signal (S2). A first amplitude controller (34, 38, 30, 32), responsive to a phase control signal (S3) supplied thereto, varies the amplitudes of the second (B) and third (C) intermediate signals in opposite directions (38) for controlling the phase of the phase shifted output signal. Additionally, a further amplitude controller (40, 42) is provided for reducing a tendency for variations in the phase shift control signal (S3) to alter the amplitude of alternating current (FIG. 5) and direct current (FIG. 6) components of the phase shifted output signal (S2).

Abstract: An apparatus and method for an improved hardware implementation of a digital phase shifter which provides a simplified process for phase correction of digital signals and eliminates the use of a lookup ROM and complex digital Multipliers. The digital phase shifter operates by applying a phase correction to complex digital I/Q samples in separate stages, where each stage performs a phase rotation by an amount specified directly by the binary values of an integer input phase. In one aspect, an apparatus for applying a phase shift to a complex digital signal comprises a plurality of phase shift stages each having a phase shift value associated therewith, whereby each of the plurality of phase shift stages selectively applies the corresponding phase shift value to the complex digital signal.

Abstract: A phase interpolator that receives input clock phase and selection inputs that are distinct from the input clock phases. The phase interpolator generates an output clock phase based on the selection inputs. The phase interpolator includes selector devices which receive the input clock phases and receive the selection inputs, and includes cross-coupled switches which are connected to the selector devices and receive input clock phases therefrom. The selector devices select which input clock phases to provide to the cross-coupled switches based upon the selection inputs. The cross-coupled switches generate the output clock phase based upon the input clock phases which are received from the selector devices.

Abstract: A skew adjusting circuit can carry out optimum correction of skew by automatically reading skew amounts of transmission paths with a receiving-side IC, without setting particular skew amounts externally. The skew adjusting circuit includes delay generating circuits, a plurality sets of flip-flops, decoders and selectors. Each delay generating circuit is provided to one of channels, and includes delay elements, each of which has a same delay amount. Each set of the flip-flops is provided to one of the delay generating circuits except for a first delay generating circuit corresponding to a reference channel signal. The flip-flops of each set receive an output of a final delay element of the first delay generating circuit as a clock signal, and receive tap outputs of the associated one of the delay generating circuits. Each decoder receives outputs of the flip-flops of one of the sets of flip-flops.

Abstract: A data extracting circuit extracts data much more accurately at a much higher response speed. A clock transfer section propagates an input clock signal through unit delay devices thereof. An edge detecting section locates an edge of the clock signal, which edge is being propagated through the clock transfer section, for a time represented by a given edge of an input data signal. In response to an edge detection signal indicating the clock signal edge located, a clock selecting section selects one of outputs of the delay devices, and presents the output as a clock input to a latch.

Abstract: The present invention relates to, more specifically, an electronic circuit apparatus having a main system portion and a subsystem portion connected to the main system portion. In the electronic circuit apparatus, at least either the main system or the subsystem comprises a clock source, a clock wire having an outgoing path and an incoming path, wherein a clock signal from the clock source is inputted from one end of the outgoing path, and at least one receiver connected to an optional position of the outgoing path, further connected to a position of the outgoing path adjacent to the optional position, for supplying a clock signal having an optional delay level relative to the clock signal from the clock source according to a delay level between each clock signal at the positions.

Abstract: A circuit for generating a signal that is proportional to the phase difference between a reference signal and a variable frequency signal. The circuit includes a reference generating circuit for generating N phase shifted reference signals from the reference signal. Each of the phase shifted reference signals has the same frequency and a different phase. The phase of the n.sup.th one of the phase shifted reference signals is equal to 360n/N degrees, where N>1 and n runs from 0 to N-1. A phase detection circuit generates a phase output signal proportional to the phase difference between the variable frequency signal and the phase shifted reference signal currently being outputted by the reference generating circuit. The phase output signal has value of I when the output signal corresponds to a phase difference of 360/N degrees.

Abstract: A discrete phase shifter and a method for discrete phase shifting in which an input signal is split into two signals. One of the split signals is phase shifted by a first fixed amount by a first fixed phase shifter cell, and the other split signal is phase shifted by a second fixed amount by a second fixed phase shifter cell. A selector is utilized to select at least one of the two split phase shifted signals and to input these to a vector summer. The vector summer synthesizes an output signal that is phase shifted with respect to the input signal. In this manner, the output signal is discretely phase shifted either by the first fixed amount, the second fixed amount, or, by selecting both of the split signals prior to vector summing, the sum of these amounts.

Abstract: The present invention relates to a digital phase correcting apparatus, including a phase comparator (100), a loop filter (110), and a digital controlled oscillator (120). The digital controlled oscillator (120) includes a phase clock signal generator (400), a multiplexer (410), an up/down counter (430), and a frequency divider (420). The phase clock signal generator (400) receives the master clock signal as an input and generates therefrom a plurality of clock signals having a phase difference of half a period of the master clock signal. The multiplexer (410) selects and outputs one of the clock signals generated in the phase clock signal generator (400). The up/down counter (430) receiving a phase lead/lag signal of the loop filter (110) and provides an output select signal for the multiplexer (410). The frequency divider divides the frequency of the clock signal output from the multiplexer and outputting the phase locked clock signal to the phase comparator.