Abstract: Receiver circuits using nanotube-based switches and transistors. A receiver circuit includes a differential input having a first and second input link, a differential output having a first and second output link, and first and second switching elements in electrical communication with the input links and the output links. Each switching element has an input node, an output node, a nanotube channel element, and a control structure disposed in relation to the nanotube channel element to controllably form and unform an electrically conductive channel between said input node and said output node. First and second MOS transistors are each in electrical communication with a reference signal and with the output node of a corresponding one of the first and second switching elements.

Abstract: A digital waveform synthesiser (1) is implemented as a single chip integrated circuit on a single chip (2) and comprises a direct digital synthesiser (10) which produces a synthesised output signal waveform on an output terminal (4) which is substantially phase and frequency locked to the phase and frequency of an externally generated input signal applied to an input terminal (5).

Abstract: A phase interpolator receiving a first signal having an oscillation frequency Fin and providing a second signal having said oscillation frequency and having a phase shift ?? with respect to the first signal which depends on a third signal.

Abstract: Phase detector circuitry for a phase-locked loop frequency synthesizer, the phase detector circuitry comprising a reference input configured to receive a reference signal; a feedback input configured to receive a divided signal from divider circuitry in a feedback path of the phase-locked loop; and pulse generation circuitry configured to generate control pulses for controlling a charge pump in the phase-locked loop in accordance with a frequency and phase relationship between the reference signal and the divided signal; wherein the divided signal comprises a pulse having a length shorter than a half period of the divided signal, and wherein the pulse generation circuitry is configured to generate the control pulses by masking the reference signal using the pulse of the divided signal as a mask, so as to define the edges of the control pulses from the edges of the divided signal and an edge of the reference signal.

Abstract: Jitterless transition of the programmable clock waveform is generated employing a set of two coupled direct digital synthesis (DDS) circuits. The first phase accumulator in the first DDS circuit runs at least one cycle of a common reference clock for the DDS circuits ahead of the second phase accumulator in the second DDS circuit. As a phase transition through the beginning of a phase cycle is detected from the first phase accumulator, a first phase offset word and a second phase offset word for the first and second phase accumulators are calculated and loaded into the first and second DDS circuits. The programmable clock waveform is employed as a clock input for the RAM address controller. A well defined jitterless transition in frequency of the arbitrary waveform is provided which coincides with the beginning of the phase cycle of the DDS output signal from the second DDS circuit.

Abstract: A method for use in a digital frequency synthesizer, the method comprising phase to amplitude conversion of an output value of a phase accumulator in said synthesizer, said conversion being carried out as an approximation (y) of a phase value (x) which corresponds to said output amplitude value, the method being characterized in that the approximation comprises a combination of a linear interpolation value and a second order sinusoidal value, the second order sinusoidal value being used as an error term to correct for errors in the linear interpolation value.

Abstract: The present invention reduces adjacent channel interference for a wireless peripheral device. A direct digital synthesizer generates a waveform having intermediate angular changes during a transition time between symbol intervals. After the transition time, the direct digital synthesizer generates the waveform with an angular value that corresponds to the symbol being transmitted. In an exemplary embodiment, a generated waveform is characterized by one of two designated frequencies in response to a value of an input information bit. The waveform is further characterized by at least one intermediate frequency during a transition time between a change of the designated frequency. Another embodiment of the invention utilizes phase changes rather than frequency changes during reduce adjacent channel interference. With another aspect of the invention, methods are provided to determine waveform parameters for reducing adjacent channel power (ACP) to a maximum level of interference.

Abstract: A frequency synthesizer includes a digitally-controlled oscillator and an oscillation frequency control unit. The digitally-controlled oscillator includes a loop-shaped transmission line path having an odd number of parallel portions in each of which two conductors are arranged in parallel to each other with a space therebetween, and an odd number of intersection portions in each of which two conductors intersect spatially, an active circuit coupled between the two conductors, and a first variable capacitance unit and a second variable capacitance unit. The oscillation frequency control unit includes a ?? modulation circuit for subjecting to ?? modulation a first control signal for switching a high capacitance state and a low capacitance state of a first variable capacitance element included in the first variable capacitance unit.

Abstract: The present invention relates to a counter circuit and method of controlling such a counter circuit, wherein a first counting section counts in accordance with a state-cycle, and a second counting section is clocked by the first counting section. At least one invalid counting state is introduced by controlling the second counting section to change its state before the first counting section has completed the state-cycle; and the at least one invalid counting state is then detected and corrected. Thereby, some redundancy is introduced in the counter, which can be used to detect and correct incomplete switching of counter states.

Abstract: There is provided a signal generating apparatus for generating an output signal corresponding to pattern data supplied thereto. The signal generating apparatus includes a timing generating section that generates a periodic signal, a shift register section including a plurality of flip-flops in a cascade arrangement through which each piece of data of the pattern data is propagated sequentially in response to the periodic signal, a waveform generating section that generates the output signal whose value varies in accordance with a cycle of the periodic signal, based on data values output from the plurality of flip-flops, and an analog circuit that enhances a predetermined frequency component in a waveform of the output signal generated by the waveform generating section.

Abstract: A timing generator that needs no analog circuit for adding jitters and allows the circuit scale and power consumption to be reduced.

Abstract: The logic gate of the present invention is of a configuration that includes a first transistor, a second transistor, and a connection-switching unit. The first transistor receives a first voltage at its source, a first input signal at its gate, and supplies a first output signal from its drain. The second transistor receives a second voltage that is lower than the first voltage at its source, receives a second input signal at its gate, and supplies a second output signal from its drain. The connection-switching unit is connected between the drains of the first transistor and the second transistor for connecting and cutting off the first transistor and the second transistor.

Abstract: The circuits and methods of the various embodiments of the present invention enable changing the frequency of a frequency synthesizer. According to one embodiment, a method of changing a frequency of a clock signal generated by a frequency synthesizer comprises the steps of receiving a reference clock signal; receiving a command comprising a new frequency synthesizer value; locking to a new frequency based upon the new frequency synthesizer value; and dynamically outputting a generated clock signal based upon the new frequency synthesizer value. According to another embodiment, a method of changing a frequency of a clock signal comprises adaptively adjusting the digital loop bandwidth of the frequency synthesizer. A circuit for changing a frequency of a clock signal generated in an integrated circuit is also disclosed.

Abstract: Exemplary techniques for turning off the clock signal to flip flops are described, which may reduce power consumption by electronic devices. In an implementation, a clock-gating logic turns off the clock signal to a flip flop when a data input of the flip flop remains untoggled. The reduction in power consumption is envisioned to also reduce heat generation.

Abstract: A method and apparatus for reducing in-band spurs in a fractional-N synthesizer (100) includes generating a compensated current signal by a charge pump (108) coupled to a phase detector (106). The compensated current signal includes in-band spurs having frequencies within a frequency bandwidth associated with a loop filter (110). The method then includes selectively dithering the compensated current signal with a sufficient dither level to spread the frequencies of in-band spurs beyond the frequency bandwidth associated with the loop filter (110). The dithered compensated current signal is then passed through the loop filter (110) for filtering the in-band spurs having frequencies beyond the frequency bandwidth. The method then includes generating a voltage controlled oscillator (VCO) signal with reduced in-band spurs proportional to the filtered compensated current signal.

Abstract: A radio frequency generating system comprises a synchronization board that receives an external clock signal from a clock source and generates multiple copies of the external clock signal. Each of a plurality of signal generation board receives a copy of the external clock signal from the synchronization board. Each signal generation board comprises a plurality of direct digital synthesizers that are synchronized using the external clock signal.

Abstract: A frequency synthesis phase-locked loop architecture using a regenerative sampling latch is described. The frequency divider typically employed in the feedback path of a frequency synthesis phase-locked loop is replaced by a regenerative sampling latch with a binary output. The regenerative sampling latch subsamples the frequency synthesizer output to produce a low-frequency aliased signal that can be processed further or directly used to lock the phase-locked loop. This architecture is referred to as an alias-locked loop. The relaxed constraints on the regenerative sampling latch make it possible to create high-speed frequency synthesizer phase-locked loops without the suffering the limitations imposed by traditional dividers connected directly to the oscillator output.

Abstract: A frequency synthesizer and a method for constructing the same by using the architecture of digital process frequency loop (DPFL) are disclosed. The DPFL frequency synthesizer with the DPFL architecture includes a reference frequency divider counter, an output divider counter, a processor, a memory, a digital to analog converter (DAC), and a voltage Control Oscillator (VCO). The method uses the processor to perform the signal processing to correct the output frequency of the VCO in the frequency domain. The memory stores the nonlinear characteristics of the VCO such that the synthesizer is completely controlled, no uncertain frequency being captured during process, and the frequency resolution of the synthesizer is programmable.

Abstract: A method and apparatus for a structure of a flip-flop that is tolerant to the noise pulses occurring due to the presence of crosstalk faults by sampling the input data multiple times before and after the active clock edge. The final stored value at the flip-flop is determined by the resolution of a counter circuit residing in the flip-flop, which is activated at the change of the sampled input data. This counter based resolution mechanism allows for the detection and filtering of the noise pulse induced at the input of the flip-flop due to a crosstalk fault.

Abstract: A code is provided which outputs a predetermined code enable signal by executing a simple control, depending on a clock signal frequency, with an optimal circuit scale. A multiplexer receives integers which are relatively prime, and outputs either of them to an adder, depending on comparator output signal. The adder adds an integer latched by the register and an integer output by the multiplexer, and outputs the result via a multiplexer to the register. The register latches and outputs the received integer to the comparator with a sampling clock signal frequency. In accordance with a threshold set based on the integers and the number of bits of the adder or the register, the comparator outputs a signal having the High state only when the output integer of the register satisfies the threshold condition. The code outputs this as a code enable signal.

Abstract: Method and apparatus for digital frequency synthesis are described. A frequency synthesizer has an accumulator, an adder, and a predictive filter. The adder is configured to subtract a predicted error from a phase profile signal. A quantized version of the phase profile signal is separated from an error portion thereof. The predictive filter, set for a fraction of a sample frequency bandwidth, is coupled to receive the error portion for generation of a next predicted error. A storage device has digital representations of sinusoidal signals accessible responsive to the quantized version of the phase profile signal. A digital-to-analog converter is coupled to receive a digital representation of a sinusoidal signal obtained from the storage device to provide an analog sinusoidal signal. An anti-imaging filter is coupled to receive the analog sinusoidal signal and configured to filter out noise.

Abstract: A digital frequency synthesizer receiving a first signal corresponding to a periodic sequence of first pulses at a first frequency and providing a second signal corresponding to a periodic sequence of second pulses at a second frequency. The synthesizer includes a first circuit clocked by a third signal corresponding to a sequence of third pulses and obtained from the first signal, the first circuit providing a fourth digital signal which, for any set of third successive pulses, increases (decreases) on each pulse and decreases (increases) at the end of said set; and a second circuit receiving the first and fourth signals and providing, for each first pulse from among some at least of the first pulses, a second pulse which is shifted with respect to the first pulse by a duration which depends on the fourth signal.

Abstract: In accordance with described exemplary embodiments, correction is inserted into the feedback loop of a second order resonator used at the time of frequency transition. The correction is based upon parameters generated from a desired output signal frequency and a desired sampling frequency. The correction is generated to maintain i) constant amplitude, ii) continuous phase, and iii) the same sampling frequency during the frequency transition.

Abstract: A digital circuit generates very precise clock frequencies for applications that can tolerate a small degree of jitter but require exact long term frequencies, e.g. a video clock for a laser printer. Some subpixel jitter is acceptable, but the overall pixel rate remains exact and consistent. In some applications, the jitter may be desirable to smear the EMI spectrum. For example, if the high frequency input clock is modulated, the edges of the video clock will also be modulated yet remain within the jitter and frequency specification.

Abstract: A data receiver is provided which includes a front end interface circuit having an alternating current (AC) transmission receiving mode and a direct current (DC) transmission receiving mode. The front end interface circuit includes an offset compensation circuit operable to compensate a DC voltage offset between a pair of differential signals input to the data receiver. The front end interface circuit further includes an AC/DC selection unit operable to switch between (a) the DC transmission receiving mode, and (b) the AC transmission receiving mode, such that the data receiver is operable in (i) the DC transmission mode in which the offset compensation circuit is disabled, (ii) the DC transmission mode in which the offset compensation circuit is enabled, (iii) the AC transmission mode in which the offset compensation circuit is disabled, and (iv) the AC transmission receiving mode in which the offset compensation circuit is enabled.

Abstract: Circuits, methods, and apparatus for adjusting an NCO output in order to provide a signal that is phase-locked to a reference signal. This is particularly beneficial where the frequencies of the NCO output and reference signal are unrelated. One embodiment provides a circuit that corrects the phase of the NCO output in two steps in order to reduce the chance of metastability. During the first, the output of the NCO is phase shifted to the closest correct portion of a cycle of a clock signal. A second correction is then performed by steering a number of currents under the control of at least some of a number of remainder bits from the NCO. The current steering provides a die area efficient, low-noise phase correction. The decoded remainder bits are latched using a feed forward circuit that prevents the device from entering a locked state.

Abstract: A synthesizer that has a phase detector 8 and a charge pump circuit 9 for injecting an electric charge, or pulling it out that corresponded to a frequency difference of an input, a low-pass filter 11 for converting this electric charge into a voltage, a voltage control oscillator (VCO) 13 for changing an output frequency for this input voltage, a divider 14 for dividing the frequency of the input, and a voltage holding circuit 10 for holding the input voltage for a plurality of output frequencies of the VCO. A holding voltage of the voltage holding circuit 10 is switched with a switch 12, and the frequency of an output clock signal 3 is switched.

Abstract: A circuit for receiving an input signal having a first frequency and generating an output signal having a second frequency. The circuit comprises a forward branch for receiving the input signal and generating the output signal and a return branch for generating a feedback signal from the output signal. The forward branch comprises a frequency detector for receiving the input signal and the feedback signal and outputting a value based on a ratio of a frequency of the feedback signal to the first frequency; a word length reduction block for receiving a fractional component of a first division factor and generating a modulated output; an adder for forming a sum of an integer component of the first division factor and the modulated output of the word length reduction block; a subtracting element for subtracting the output value of the frequency detector from the sum; and an oscillator controlled by an output from the subtracting element.

Abstract: The present invention is related to a digital circuit for use in a mixed-signal circuit.

Abstract: Circuits for forming the inputs of a latch are provided. In some embodiments, circuits for forming inputs of a latch comprise: a first transistor having a first gate terminal, a first drain terminal, a first source terminal, a first gate length, and a first common mode level at the first gate terminal, wherein the first gate terminal provides a data input to the latch; and a second transistor having a second gate terminal, a second drain terminal, a second source terminal, a second gate length, and a second common mode level at the second gate terminal, wherein the second gate terminal provides a clock input to the latch, the second drain terminal is coupled to the first source terminal, and the first gate length and the second gate length are sized so that the first common model level and the second common mode level are substantially equal.

Abstract: A double data rate (DDR) transmitter and a clock converter circuit are provided. The clock converter circuit includes a first logic circuit and a second logic circuit. The first logic circuit receives a clock signal as a trigger signal, performs a sequential logic operation based on the clock signal, and outputs a result of the sequential logic operation. The second logic circuit is coupled to the first logic circuit. The second logic circuit performs a combinational logic operation based on the output of the first logic circuit and outputs a result of the combinational logic operation as a converted signal. The converted signal has the same waveform and frequency as those of the clock signal, and the phases of the clock signal and the converted signal are the same or only slightly different.

Abstract: A process inserts a random noise in a Time to Digital Converter (TDC) designed for calculating the phase error between a first high frequency signal FDCO with respect to a second reference signal, switching at a lower frequency.

Abstract: A frequency synthesis circuit includes a phase locked loop and an interpolator circuit. The phase locked loop circuit receives a reference clock and a feedback clock and generates an output clock with a frequency based on the reference clock and the feedback clock. An interpolator circuit is coupled in the feedback path of the phase locked loop circuit. An interpolator control circuit generates an interpolator control word that specifies a variable time delay for the interpolator circuit. The interpolator circuit receives the output clock, and generates the feedback clock by introducing a variable time delay in the output clock in accordance with the interpolator control word. The time variable delay varies the frequency of the output circuit. Embodiments for frequency synthesis circuits that include a spread spectrum frequency clock generator, frequency modulators, and a fixed frequency clock generator circuit are disclosed.

Abstract: A signal generator including a DDS-signal source that is configured to operate according to the principle of direct digital synthesis (DDS), and a PLL signal synthesizer that is configured to operate according to the principle of phase locked loop (PLL) using an output signal from the DDS-signal source as a reference signal. The DDS-signal source can be connected via a direct connection, without further frequency division or mixing, directly to an output of the signal generator or directly to a level-adjustment device of the signal generator in order to generate a portion of an overall frequency range of an output signal of the signal generator.

Abstract: A high performance phase detector includes a local digital oscillator for generating a digital reference signal of programmable frequency and phase. The phase detector accumulates a difference in phase between the digital reference signal and a sampled input signal to produce a measure of phase error. The phase detector can be advantageously used in a frequency synthesizer to produce signals with low phase noise and accurate phase control. Synthesizers of this type can further be used to as building blocks in ATE systems and other electronic systems for generating low jitter clocks and waveforms.

Abstract: The logic gate of the present invention is of a configuration that includes a first transistor, a second transistor, and a connection-switching unit. The first transistor receives a first voltage at its source, a first input signal at its gate, and supplies a first output signal from its drain. The second transistor receives a second voltage that is lower than the first voltage at its source, receives a second input signal at its gate, and supplies a second output signal from its drain. The connection-switching unit is connected between the drains of the first transistor and the second transistor for connecting and cutting off the first transistor and the second transistor.

Abstract: A radio frequency generating system comprises a synchronization board that receives an external clock signal from a clock source and generates multiple copies of the external clock signal. Each of a plurality of signal generation board receives a copy of the external clock signal from the synchronization board. Each signal generation board comprises a plurality of direct digital synthesizers that are synchronized using the external clock signal.

Abstract: A method to improve the frequency resolution and phase noise of a synthesized RF signal results in superior instantaneous frequency change and phase modulation capability, wide frequency set ability, and suitability for implementation in a digital ASIC. The RF signal synthesis is achieved from a higher reference frequency clock signal using a variable pulse stretching technique. The amount of the pulse stretch in each cycle is set by a phase increment value and is implemented using programmable delay lines. Pulse stretching can be extended beyond one cycle by pulse swallowing, allowing the generation of an RF signal with frequencies from DC up to the input reference frequency. Phase modulation is incorporated by digital control of the phase stretching with the phase modulation bits.

Abstract: Methods and apparatuses for accumulating a phase increment that comprises an overflow to a phase information signal; mapping the phase information signal to an amplitude information signal; quantizing the amplitude information signal while feeding back a quantization noise using a first filter of an nth order, so that the feedback of the quantization noise comprises zeros at least two mutually different frequencies in a transfer function of the first filter; and performing digital/analog conversion of the quantized amplitude information signal to an oscillation signal.

Abstract: A radar system having a transmit signal path and a receive signal path and an event generator which is responsive to command signals provided by a digital signal processor (DSP) is described. The DSP generates command signals and provides the command signals to the event generator. In response to the command signals, the event generator generates event signals in the radar system. The event signals include but are not limited to ramp control signals provided to a controllable signal source which provide RF signals to the transmit path of the radar.

Abstract: Testing a device under test—DUT—includes providing a test signal from the DUT to a test probe, taking from the test signal being present at the test probe analog samples at a first sampling rate, taking from the test signal being present at the test probe digital samples at a second sampling rate, providing a control signal indicative of sampling times of the analog samples, and performing an analysis of the digital samples in conjunction with the control signal.

Abstract: Circuitry for synthesizing an arbitrary clock signal with minimal jitter is provided. The circuitry of this invention selectively multiplexes a sequence of two different byte patterns into a serializer, which serializes the sequence and transmits it to receiver circuitry in the serial domain. The frequency of the synthesized clock transmitted by the serializer is a function of the serialized sequence and the frequency in which the serialized sequence is transmitted to the receiver circuitry. Thus, a desired clock frequency can be synthesized by manipulating the byte patterns and the sequence in which the bytes are serialized.

Abstract: A digital circuit generates very precise clock frequencies for applications that can tolerate a small degree of jitter but require exact long term frequencies, e.g. a video clock for a laser printer. Some subpixel jitter is acceptable, but the overall pixel rate remains exact and consistent. In some applications, the jitter may be desirable to smear the EMI spectrum. For example, if the high frequency input clock is modulated, the edges of the video clock will also be modulated yet remain within the jitter and frequency specification.

Abstract: An FPGA having a programmable frequency output is provided that achieves a (theoretical) M-times reduction in output jitter from a conventional direct digital synthesis (DDS) circuit, by running M accumulator circuits in parallel and combining the outputs in a time-staggered way. I Initially the frequency number N added into the accumulators is varied slightly for each accumulator by multiplying by a number, such as X/16 where X varies from 1 to 16 for each of 16 accumulator circuits. The accumulator circuits are further reconfigured so that the output of a register from a first accumulator provides feedback to the adder input in all of the accumulator circuits. The number of overflowing accumulator registers in a clock cycle will then indicate granularity spatially. To translate spatial granularity to time, a programmable delay circuit is connected to the output of each accumulator register.

Abstract: A frequency synthesizer according to the direct digital synthesis method is provided. The frequency synthesizer includes a phase accumulator for the cyclical incrementation of a phase signal by a phase increment M present at the input of the phase accumulator, a memory unit with a table of sine-function values stored in its memory cells for the determination of sine-function values corresponding to phase values of the phase signal, a digital-to-analog converter for the conversion of time-discrete sine-function values into a quasi-analog sinusoidal time function and an anti-aliasing low-pass filter for smoothing the quasi-analog sinusoidal time function. The frequency synthesizer additionally contains an adder, which is connected between the memory unit and the digital-to-analog converter and which superimposes a non-periodic signal over the time-discrete sine-function values.

Abstract: Circuits, methods, and apparatus for reducing the phase error in an NCO clock output to reduce the clock jitter. This is particularly beneficial where the frequencies of the NCO output and reference signal are unrelated. One embodiment provides a circuit that corrects the phase of the NCO output in two steps in order to obtain a substantially glitch-free, high-speed operation. During the first step, the output of the NCO is phase shifted to the closest quarter portion of a cycle of a clock signal. A second correction step is then performed by steering a number of currents under the control of at least some of a number of remainder bits from the NCO. The current steering provides a die area efficient, low-noise phase correction. The decoded remainder bits are latched using a feed forward circuit that prevents the device from entering a locked state.

Abstract: A synthesizer that has a phase detector 8 and a charge pump circuit 9 for injecting an electric charge, or pulling it out that corresponded to a frequency difference of an input, a low-pass filter 11 for converting this electric charge into a voltage, a voltage control oscillator (VCO) 13 for changing an output frequency for this input voltage, a divider 14 for dividing the frequency of the input, and a voltage holding circuit 10 for holding the input voltage for a plurality of output frequencies of the VCO. A holding voltage of the voltage holding circuit 10 is switched with a switch 12, and the frequency of an output clock signal 3 is switched.

Abstract: A clock synthesizer for dividing a source clock by N.R including a logic circuit, a delay line, a select circuit, an accumulator, and a clock divider circuit. The logic circuit divides N.R by 2M to get NNEW.RNEW in which NNEW is zero and RNEW is at least 0.5. The delay line receives a first clock and has multiple delay taps, where the first clock is based on the source clock. The select circuit selects the delay taps based on a tap select value and provides a delayed clock. The accumulator adds RNEW for each cycle of the delayed clock and performs a modulo function on a sum value to generate the tap select value. The clock divider circuit transitions an output clock based on selected transitions of the delayed clock, which is achieved by dividing the first clock or the delayed clock by 2M?1.

Abstract: Digital frequency synthesizer (DFS) circuits and methods use counters to define the positions of the output clock edges. A clock divider divides an input clock by a positive integer to provide a divided clock. A first counter circuit counts for one divided clock period, and the count is provided to a timing circuit that generates two or more sets of intermediate values. Each set represents a set of intermediate points within a period of the divided clock. Based on a specified multiplication value, one set of intermediate values is selected. Utilizing the divided clock, the selected set of intermediate values, and a second counter running at the same frequency as the first counter circuit, an output clock generator provides an output clock having an initial pulse at the beginning of each divided clock period, and a subsequent pulse at intermediate points represented by the selected set of intermediate values.

Abstract: A polyphase numerically controlled oscillator (PNCO) is defined to include a plurality of sub-numerically controller oscillators (SNCO's). Each SNCO is capable of receiving a clock signal at a first clock rate and an assigned phase offset signal. Each SNCO is configured to generate a digital waveform for the assigned phase offset signal. The PNCO also includes a plurality of frequency multipliers for generating a frequency multiplied representation of the digital waveform generated by each SNCO. The PNCO further includes a multiplexer configured to receive output from each of the frequency multipliers according to the first clock rate. The multiplexer is further configured to receive a select signal, wherein the select signal triggers the multiplexer at a second clock rate.