Abstract: The current invention provides a second feedback loop around the existing FLL, which forces the signal on the route of N-divider (NDIV), PFD, CP, and LPF to essentially reach their desired lock conditions before the FLL is switched off and the system enters PLL mode. This loop works by comparing the output voltage of the FLL DAC to the LPF output voltage, and then using this value to modulate the divider's dividing value. After the secondary feedback loop settles, output voltage from the LPF will be equal to the value that can drive the VCO to the desired lock frequency, and the phase error at the input side of the PFD produces a zero-average current to the charge pump. When this condition is set, the loop is essentially already in phase lock and the lock transient from the FLL mode to the PLL mode will be minimal.

Abstract: Embodiments of a proportional phase comparator and method for aligning digital signals are generally described herein. In some embodiments, circuitry to align digital signals comprises a proportional phase comparator that generates triangular-shaped pulses for application to a charge pump. The triangular-shaped pulses may reduce an amount of charge injection in the charge pump close to convergence.

Abstract: An integrated circuit includes a feedback controlled clock generating circuit, such as a DLL, PLL or other suitable circuit, that is operative to provide a feedback reference frequency signal based on a generated output clock signal. The integrated circuit also includes a programmable fine lock/unlock detection circuit that includes programmable static phase error sensitivity logic that senses phase error. The programmable static phase error sensitivity logic sets a phase lock sensitivity window used to determine a fine lock/unlock condition of the generated output clock signal. The programmable fine lock/unlock detection logic is also operative to generate a fine phase lock/unlock signal based on the set phase lock sensitivity window. The integrated circuit may also include a coarse lock detection circuit that generates a coarse lock signal based on a frequency unlock condition.

Abstract: Disclosed herein is a carrier synchronizing circuit including at least frequency synchronizing means and phase synchronizing means. The phase synchronizing means includes residual frequency error detecting means for detecting a residual frequency error after a frequency synchronizing process by the frequency synchronizing means and supplying the residual frequency error to the frequency synchronizing means, and the frequency synchronizing means performs frequency pull-in for the residual frequency error supplied from the residual frequency error detecting means after first timing.

Abstract: Locked loops, bias generators, charge pumps and methods for generating control voltages are disclosed, such as a bias generator that generates bias voltages for use by a clock signal generator, such as a voltage controlled delay line, in a locked loop having a phase detector and a charge pump. The charge pump can either charge or discharge a capacitor as a function of a signal from the phase detector to generate a control voltage. The bias generator can receive the control voltage from the capacitor, and it generates bias voltages corresponding thereto. A portion of the bias generator can have a topography that is substantially the same as at least a portion of the topography of the charge pump. As a result, it can cause the charge pump to charge the capacitor at the same rate that it discharges the capacitor over a relatively wide range of control voltages. The charge pump and the bias generator can also include circuitry for limiting the charging of the capacitor when the control voltage is relatively low.

Abstract: Described is a device for receiving radio-navigation signals by satellite, said received signals being transmitted at a carrier frequency. The device includes at least means for generating a local signal at a local frequency and a tracking device including a feedback loop called carrier loop for phase-locking the local frequency on the carrier frequency. The loop includes a hardware portion and a software portion. The software portion performs the functions of discrimination of the phase of the correlated signal and filtering of said phase. The software portion also includes correlation functions mainly dependent on the linear variation coefficients between the local phases ?local delivered after each basic computation cycle. The device makes it possible to increase the loop band and the dynamic stability without changing the pre-detection band and the workload of the software.

Abstract: A circuit comprises a digital phase locked loop for generating a synchronization signal and a voltage regulator for providing regulated output voltage responsive to the synchronization signal from the digital phase locked loop.

Abstract: A phase-locked loop (PLL) having a bias generator capable of reducing noise is provided. In the PLL, a voltage controlled oscillator is driven using a regulator. The bias generator, which applies a bias voltage to the regulator, is configured to have opposite power noise characteristics to the power noise characteristics of the regulator, such that the occurrence of jitter in the PLL is reduced.

Abstract: Disclosed herein is synchronizing circuit including: a numerically controlled oscillating section; a phase rotating section; a phase error estimating section; a loop filter; and a gain controlling section; wherein the gain controlling section controls the gain so as to suppress an effect of a phase error in an immediate main signal section in a known start section from a start of the known section to a predetermined symbol.

Abstract: A charge pump includes a reference charge pump with an input interface to accept a phase detector signal and a duty-cycle feedback signal, and an output to supply a control voltage. A replica charge pump accepts the phase detector signal supplies the duty-cycle feedback signal. If the reference charge pump source current (Ip) becomes mismatched with the sinking current (In), non-equal Tn and Tp time periods may result. The phase detector accepts reference and data signals having a steady state offset error and supplies a non-50% duty cycle square wave phase detector signal. The replica charge pump supplies a duty-cycle feedback signal to the reference charge pump responsive to the non-50% duty cycle phase detector signal and the reference charge pump equalizes the source and sink currents. When the phase detector measures reference and data signals fully orthogonal in phase, it supplies s 50% duty cycle signal.

Abstract: A clock generator includes a controller, a digital phase locked loop (PLL) circuit, a charge pump phase locked loop (PLL) circuit and a divider. The controller generates a division factor and a first internal clock signal in response to a low-frequency reference clock signal and a multiplication factor. The digital PLL circuit generates a second internal clock signal in response to the reference clock signal, the division factor and the first internal clock signal. The charge pump PLL circuit generates a plurality of third internal clock signals by using the second internal clock signal. The divider generates a high-frequency clock signal in response to a phase selection signal, the division factor and the third internal clock signals.

Abstract: Locked loops, delay lines and methods for delaying signals are disclosed, such as a delay line and delay lock loop using the delay line includes a series of delay stages, each of which consists of a single inverting delay device. The inputs and outputs of a selected stage are applied to a phase inverter that inverts one of the signals and applies it to a first input of a phase mixer with the same delay that the other signal is applied to a second input of the phase inverter. The delay of the signals from the selected delay element are delayed from each other by a coarse delay interval, and the phase mixer interpolates within the coarse delay interval by fine delay intervals. A phase detector compares the timing of a signal generated by the phase interpolator to the timing of a reference clock signal applied to the delay line to determine the selected delay stage and a phase interpolation value.

Abstract: An integrated circuit device includes at least one controllable oscillator including a first control port and at least one further control port, at least one frequency control module including an output arranged to provide a frequency control signal. The at least one controllable oscillator further includes at least one compensation module including an output arranged to provide at least one compensation signal. The at least one compensation module includes an integrator component arranged to receive at an input thereof a signal that is representative of a difference between the indication of the frequency control signal and a reference signal, and to output an integrated difference signal. The at least one compensation module is arranged to generate the at least one compensation signal based at least partly on the integrated difference signal output by the integrator component.

Abstract: The present invention relates to a jitter measuring system, comprising: a delay circuit for receiving a clock signal and delaying the clock signal to generate a delay signal; a jitter amplifier for receiving the clock signal and delay signal to generate a first signal and a second signal; and a converter for converting a phase different between the first signal and the second signal into a relevant digital code; wherein the phase difference between the first signal and the second signal is an amplification of jitter.

Abstract: A phase locked loop includes a phase lock unit configured to compare a phase of a reference clock with a phase of a feedback clock and to generate an internal clock based on the comparison; a delay lock unit configured to compare the reference clock with the internal clock, and to generate the feedback clock which is delayed in response to a control voltage based on the comparison; and a start voltage enable unit configured to receive an enable signal and to apply a start voltage as the control voltage in response to the enable signal.

Abstract: A system and method for closed loop clock correction includes adjusting two or more input signals comprising at least one in-phase clock and one quadrature clock, and applying adjusted quadrature clock signals to a device capable of generating a 4-quadrant interpolated output clock phase. An interpolated output clock phase is delayed to form a clock for a measurement device. Two or more adjusted input signals are measured on a measurement device over a range of interpolated output clock phases. Errors are determined on the in-phase clock and the quadrature clock using sampled information from the measurement device. The in-phase clock and the quadrature clock are adapted using determined error information.

Abstract: A data relay apparatus according to one embodiment described herein can include a phase detection unit that can detect a phase difference between a clock output from a transmitter and a clock output from a receiver, and generate a plurality of phase detection signals, a data relay control unit that can distinguish a difference in clock timing between the clocks of the transmitter and the receiver in response to the plurality of phase detection signals, and output a relay data selection signal and a relay control clock, and a data relay unit that can transmit data output from the receiver to the transmitter in response to the relay data selection signal and the relay control clock.

Abstract: The present invention relates to a quadrature divider which may be used in a phase locked loop or frequency synthesizer or with a single side band mixer. According to a preferred embodiment the divider takes a quadrature input and has a quadrature output. The divider has four analog mixers 1, 2, 3 and 4. The first two mixers 1, 2 take the in-phase quadrature input, while the second mixers 3, 4 take the quadrature-phase quadrature input. The outputs and feedback loops of the mixers are properly arranged such that the in-phase and quadrature-phase outputs of the divider have a determinisitic phase sequence relationship based on the phase sequence relationship of the corresponding quadrature inputs. Third order harmonics may be minimized or reduced by addition or subtraction of the mixer outputs. As the divider is able to take a quadrature input, there is no need for a dummy divider in the phase locked loop, thus saving space and power.

Abstract: Microelectronics have now developed to the point where radiation within the terahertz frequency range can be generated and used. Here, an integrated circuit or IC is provided that includes a phased array radar system, which uses terahertz radiation. In order to accomplish this, several features are employed; namely, a lower frequency signal is propagated to transceivers, which multiplies the frequency up to the desired frequency range. To overcome the losses from the multiplication, an injection locked voltage controlled oscillator (ILVCO) is used, and a high frequency power amplifier (PA) can then be used to amplify the signal for transmission.

Abstract: A frequency synthesizer that utilizes locked loop circuitry, for example delay locked loop and/or phase locked loop circuits is provided with a means for minimizing static phase/delay errors. An auto-tuning circuit and technique provide a measurement of static phase error by integrating the static phase error in the DLL/PLL circuit. A correction value is determined and applied as a current at the charge pump or as a time/phase offset at the phase detector to minimize static phase error. During normal operation the DLL/PLL is operated with the correction value resulting in substantially reduced spur levels and/or improved settling time.

Abstract: A phase locked loop (PLL) which has a desired frequency characteristic even though a manufacturing process of a semiconductor integrated circuit has fluctuations. The semiconductor integrated circuit includes the PLL and a control unit. The PLL has a phase frequency detector, a loop filter, a voltage controlled oscillator (VCO) and a divider. The VCO comprises a voltage-current converter (VIC) and a ring oscillator. In response to a control voltage, the VIC generates a control current for setting each operating current of the ring oscillator. The control unit switches the PLL to a calibration operating period of its open loop and a normal operating period of its closed loop.

Abstract: In an embodiment, a circuit comprising an oscillator is provided. The oscillator is controlled based on a feedback value and an input reference value. The feedback value or the reference value or both are generated using noise shaping.

Abstract: In some embodiments, a feedback loop circuit includes a phase detector, first and second charge pumps that are each coupled to receive an output signal of the phase detector, a first low pass filter, a second low pass filter coupled to an output of the second charge pump, a clock signal generation circuit having first and second control inputs, a first switch circuit coupled between the first low pass filter and the second low pass filter, and a second switch circuit coupled to the first low pass filter and the first control input of the clock signal generation circuit.

Abstract: A circuit is provided for use with a clock having an input divider portion, a feedback divider portion, a phase detector portion, a loop compensation filter portion and a voltage controlled oscillator portion. The input divider portion receives a reference signal and outputs a divided reference signal. The feedback divider portion receives an output signal from the circuit and outputs a divided feedback signal. The phase detector portion outputs a phase detector signal based on the divided reference signal and the divided feedback signal. The loop compensation filter portion outputs a tuning signal based on the phase detector signal. The voltage controlled oscillator portion output the outputs a signal based on the tuning signal. The phase detector portion changes the phase detector signal based on the input divider portion receiving the control signal and the feedback divider portion receiving the control signal.

Abstract: Provided is a PLL circuit improving reliability while suppressing power consumption without degrading noise characteristics. The PLL circuit includes a PLL IC that divides an output frequency Fout from a VCO, compares phase with a reference signal, and feeds back a phase difference as a control voltage to the VCO. A control circuit is capable of finely setting both of a reference frequency Fref and an output frequency Fdds in a DDS circuit, and the DDS circuit generates folding signals of Fdds for Fref and an integral multiple frequency thereof based on the combination of the frequencies. A first AMP amplifies a signal, a variable filter selects a desired Fdds (desired) and a second AMP amplifies the signal and supplies the same to the PLL IC as a reference signal. The control circuit further supplies a division ratio N to the PLL IC.

Abstract: A voltage controlled crystal oscillator (VCXO) is locked to a MEMS oscillator with a variable frequency ratio that is a function of a sensed temperature. That allows the long-term stability of the MEMS oscillator and temperature compensation to be reflected in a VCXO output signal having good short-term stability.

Abstract: A circuit includes a phase detection circuit and a phase change circuit. The phase detection circuit compares a phase of a first periodic signal to an input signal to generate a gain signal. The phase change circuit provides phase shifts to the first periodic signal in first and second directions when the gain signal has a first value. The phase change circuit increases phase shifts provided to the first periodic signal in the first direction in response to the gain signal changing from the first value to a second value. The phase change circuit provides phase shifts to the first periodic signal in the second direction when the gain signal has the second value that are smaller than the phase shifts provided to the first periodic signal in the first direction when the gain signal has the second value.

Abstract: A data receiver has a clock recovery and data sampling circuit. This has a fixed local oscillator for timing the data samples. A phase interpolator adjusts the phase of the clock signal in response to an early late detector which samples the waveform at the expected position of the edges. A further correction to the sampling position is made in response to the recent history of the data received. The correction is modelled on predictable jitter, for example, that in a transmitter caused by changes in data causing the supply voltage to drop.

Abstract: A delay locked loop circuit includes a delay locked loop receiving an external clock, a frequency detector delaying an input frequency signal to generate a plurality of strobe signals and outputting a check signal indicating that the frequency of the input frequency signal is equal to or lower than a reference frequency when all of the strobe signals are positioned within a first-status section of one cycle of the input frequency signal, a delay lock reset unit generating a reset signal to reset the frequency detector and an activation signal to enable the delay locked loop to perform a delay lock process, and a direct phase detector controlling a coarse locking window on the basis of the check signal and generating a pair of phase detection signals indicating logic levels of the external clock. According to this configuration, since the coarse locking window is controlled as per a frequency band, it is possible to prevent a failure of a coarse locking and to achieve an improved circuit performance.

Abstract: A system and method are provided for frequency lock stability in a receiver using overlapping voltage controlled oscillator (VCO) bands. An input communication signal is accepted and an initial VCO is selected. Using a phase-locked loop (PLL) and the initial VCO, the frequency of the input communication signal is acquired and the acquired signal tuning voltage of the initial VCO is measured. Then, the initial VCO is disengaged and a plurality of adjacent band VCOs is sequentially engaged. The acquired signal tuning voltage of each VCO is measured and a final VCO is selected that is able to generate the input communication signal frequency using an acquired signal tuning voltage closest to a midpoint of a predetermined tuning voltage range.

Abstract: There is provided a frequency synthesizer. The frequency synthesizer includes a frequency oscillator adjusting an output frequency according to a control bit; a programmable divider having a preset minimum division ratio, the programming divider dividing the output frequency of the frequency oscillator at a variable division ratio; a counter unit receiving an output signal of the programmable divider and a reference frequency to generate a count value by counting rising edges of the output signal of the programmable divider during one cycle of the reference frequency, and outputting a first hit signal when the count value is 1, and outputting a second hit signal when the count value is 2; and a phase detection unit outputting a control bit obtained by subtracting a fractional error of the output signal of the programmable divider from a fractional error at a locked phase obtained from the count value and the reference frequency.

Abstract: Disclosed is a PLL oscillator circuit capable of examining an unlock state while being equipped with an auto retry function enabling automatic relock. In the PLL oscillator circuit, a MPU receives a lock detection signal from the PLL-IC that receives an external reference signal and an output signal from a VCXO and outputs a control voltage to the VCXO, sets data for unlock alarm test at the PLL-IC, the data turning a lock state into an unlock state, when determining an unlock state with the lock detection signal from the PLL-IC, outputs an unlock alarm output signal to the outside, determines whether the unlock state continues for a first time period, and when the unlock state continues for the first time period, executes retry to set data for relock at the PLL-IC.

Abstract: An up/down detection unit samples a received data signal and determines in which of first through third areas of the data signal the logic level of the data signal transitions, wherein the data sampling clock signal, the first edge sampling clock signal, and the second edge sampling clock signal are sequentially activated. A lower limit detection unit detects a lower limit of the first area if the logic level of the data signal transitions in the first area. An upper limit detection unit detects an upper limit of the third area if the logic level of the data signal transitions in the third area. A phase detection unit determines a delay amount indicating the amount by which the data signal is to be delayed according to the upper limit and lower limit detected. A buffer unit delays the data signal by the delay amount determined by the phase detection unit.

Abstract: There is provided an art to prevent an unstable operation due to temperature in a PLL apparatus in which a proper range of an amplitude level of an external reference frequency signal is specified and a control voltage is supplied to a voltage-controlled oscillator according to whether the amplitude level falls within the proper range or not.

Abstract: A phase controller can be part of a phase-locked loop (PLL) or a delay-locked loop (DLL). The phase controller includes first and second regulators. The first regulator provides power supply noise rejection while the second regulator provides phase and frequency lock.

Abstract: A method and apparatus for clock recovery in synchronous digital systems. The apparatus includes a phase frequency detector, a loop filter, a compressor, and a clock generator. The phase frequency detector generates a phase error signal based on a difference between an input clock signal and an output clock signal. The loop filter multiplies the phase error signal and filters the multiplied phase error signal. The compressor divides the loop filter output. Based on the compressor output, the clock generator generates an output clock signal is provided as a feedback signal to the phase error detector. The apparatus may also include a glitch cleaner for deglitching the input clock signal.

Abstract: In a phase adjustment circuit that divides the frequency of a double-frequency clock to obtain a 50% duty-cycle clock, a first ½ frequency division circuit having a phase inversion function generates an intermediate reference clock apart in phase from both a phase reference clock and a phase-adjusted clock. A first phase control circuit controls the phase of the intermediate reference clock to be in a desired phase state with respect to the phase reference clock. A second phase control circuit controls the phase of the phase-adjusted clock to be in a desired phase state with respect to the intermediate reference clock. Thus, when the phase-adjusted clock is adjusted to be close in phase to the phase reference clock, the phase difference between these clocks can be determined correctly and stably even if it varies due to clock jitter.

Abstract: To generate a highly accurate SSC while reducing the circuit area of a clock generation circuit that generates a normal clock and an SSC. A clock signal output from a voltage controlled oscillator is frequency-divided by a frequency divider, and is output as a first frequency-divided clock to a selector. The frequency divider outputs a plurality of second frequency-divided clocks each shifted in phase by 1/m of a period based on a control signal of a control circuit. The selector selects two frequency-divided clocks having the closest phase shift from among the first and second frequency-divided clocks. Based on a weighting data signal output from the control circuit, a phase interpolation circuit phase-shifts the frequency-divided clock by a phase shift obtained by dividing the phase difference between the two frequency-divided clocks, and outputs the resultant clock as an output clock.

Abstract: An adaptive digital phase locked loop comprises: a digital configurable phase detector for receiving a reference signal and a feedback signal and for generating a detection signal indicative of a phase/frequency difference between the reference signal and the feedback signal; a configurable digital loop filter for filtering the DPFD detection signal; a digital locking monitor for monitoring polarity transitions of the detection signal and adaptively switching the locking modes and DCO tuning resolution; and a DCO for generating the feedback signal as a function of the detection signal.

Abstract: A carrier recovery apparatus includes a pilot strength detector, a first lock loop, a second lock loop, and a controller. The pilot strength detector determines whether a pilot strength of an input signal is greater than a threshold value to generate a control signal. The first lock loop performs a first carrier recovery on the input signal. The second lock loop performs a second carrier recovery on the input signal. The controller selectively allows the first lock loop to perform the first carrier recovery on the input signal or the second lock loop to perform the second carrier recovery on the input signal according to the control signal. The first lock loop is a pilot-based FPLL and the second locked loop is a pilot-less PLL.

Abstract: A clock signal generator and conditioner in which dual integrated phase-locked loop (PLL) circuits use an off-chip frequency-pullable crystal resonator or voltage-controlled oscillator (VCO) module and an on-chip VCO with intra-PLL frequency doubling to provide a clock signal with reduced in-band phase noise and RMS jitter. As desired, synchronization between the input and output clocks can also be provided.

Abstract: A phase locked loop circuit in accordance with an embodiment implements a digital phase delay quantizer to replace the analog charge-pump and phase frequency detector in an analog PLL circuit. Therefore, the built-in loop filter can be a compact-sized, high order, high bandwidth, and high attenuation digital filter as well. The digital PLL circuit takes advantage of the deep sub-micron process technology which features high speed, high resolution, compact size, and low power.

Abstract: Some embodiments regard a circuit comprising: a first circuit configured to lock a frequency of an output clock to a frequency of a reference clock; a second circuit configured to align an input signal to a phase clock of the output clock; a third circuit configured to use a first set of phase clocks of the output clock and a second set of phase clocks of the output clock to improve alignment of the input signal to the phase clock of the output clock; and a lock detection circuit configured to turn on the first circuit when the frequency of the output clock is not locked to the frequency of the reference clock; and to turn off the first circuit and to turn on the second circuit and the third circuit when the frequency of the output clock is locked to the frequency of the reference clock.

Abstract: In a reception apparatus 1, a multiphase sampling clock signal is generated by a sampling clock signal generation circuit 40, based on a clock signal which has been phase-adjusted by a phase adjustment circuit 50. The data of each of the bits of a serial data signal is sampled and output by a sampler block circuit 30n, with timing indicated by the sampling clock signal. The amount of phase adjustment of the clock signal in the phase adjustment circuit 50 is set such that the delay time from generation of the multiphase sampling clock signal in the sampling clock signal generation circuit 40 until indication of the sampling timing by the sampling clock signal in the sampler block circuit 30n is canceled.

Abstract: One or two Serializer/Deserializer (SerDes) modules are used to measure the time between two pulses with high resolution. A PLL inside a SerDes block is locked to a reference clock and an input signal is passed through a storage element to create a serial data stream that is converted into a parallel data stream by a demultiplexer inside the SerDes. The parallel data is stored in a bit logic unit that compares the parallel data to a second parallel data obtained in similar fashion in another SerDes from a second input signal. The time between the two pulses is then calculated as the number of cycles in the serial data stream that corresponds to the number of bits between the positions of the two events.

Abstract: A voltage controlled oscillator (VCO) for a phase locked loop (PLL) includes a startup oscillator, the startup oscillator comprising a first plurality of inverters; a primary oscillator, the primary oscillator comprising a second plurality of inverters, wherein a number of the second plurality of inverters is fewer than the number of the first plurality of inverters; and a control module connected to the startup oscillator and the primary oscillator. A method of operating a voltage controlled oscillator (VCO) in a phase locked loop (PLL), the VCO comprising a startup oscillator and a primary oscillator includes sending an enable signal to the startup oscillator; waiting a predetermined number of startup oscillator clock cycles; and when the predetermined number of startup oscillator clock cycles has elapsed, sending a disable signal to the startup oscillator, and sending an enable signal to the primary oscillator.

Abstract: A novel solution that combines the technologies of fractional divider and phase selection is provided to implement over-clocking for CPU PLL in PC clock generator with a set resolution that is independent of the clock frequency.

Abstract: Methods and apparatus for determining at least part of the width of the eye of a high-speed serial data signal use clock and data recovery circuitry operating on that signal to produce a first clock signal having a first phase relationship to the data signal. The first clock signal is used to produce a second clock signal whose phase can be controllably shifted relative to the first phase. The second clock signal is used to sample the data signal with different amounts of phase shift, e.g., until error checking circuitry detects that data errors in the resulting sample exceed an acceptable threshold for such errors. The amount(s) of phase shift that caused exceeding the threshold can be used as a basis for a measurement of eye width.

Abstract: Provided is an electromagnetic interference (EMI) removing device for active reduction of electromagnetic interference and a semiconductor package including the same.

Abstract: A digital phase-locked loop (DPLL) supporting two-point modulation is described. In one design, the DPLL includes a phase-to-digital converter and a loop filter operating in a loop, a first processing unit for a lowpass modulation path, and a second processing unit for a highpass modulation path. The first processing unit receives an input modulating signal and provides a first modulating signal to a first point inside the loop after the phase-to-digital converter and prior to the loop filter. The second processing unit receives the input modulating signal and provides a second modulating signal to a second point inside the loop after the loop filter. The first processing unit may include an accumulator that accumulates the input modulating signal to convert frequency to phase. The second processing unit may include a scaling unit that scales the input modulating signal with a variable gain.