KR102730479B1 - The Oscillator System That Corrects Frequency by Varying The Capacitor Bank Value - Google Patents

Abstract

The present invention relates to an oscillator system for compensating the frequency by varying a cap bank value, wherein the system derives an optimal cap bank control value based on a lookup table including a difference between an output frequency output from an oscillator with respect to a target frequency desired by a user and a preset constant voltage, and a compensable frequency for each cap bank control value with respect to the preset constant voltage, and primarily compensates the frequency by varying the cap bank value of the oscillator according to the optimal cap bank control value, and finally compensates the frequency output from the oscillator through the compensation voltage by changing the operation mode of a multiplexer which inputs an input control voltage to the oscillator.
In addition, this patent is a research supported by the Industrial Technology Evaluation and Planning Institute (1/1) research expenses for 2023-2024. (20026544)

Description

{The Oscillator System That Corrects Frequency by Varying The Capacitor Bank Value}

The present invention relates to an oscillator system for compensating the frequency by varying a cap bank value, wherein the system derives an optimal cap bank control value based on a lookup table including a difference between an output frequency output from an oscillator with respect to a target frequency desired by a user and a preset constant voltage, and a compensable frequency for each cap bank control value with respect to the preset constant voltage, and primarily compensates the frequency by varying the cap bank value of the oscillator according to the optimal cap bank control value, and finally compensates the frequency output from the oscillator through the compensation voltage by changing the operation mode of a multiplexer which inputs an input control voltage to the oscillator.

A voltage controlled oscillator (VCO) is a type of oscillator that controls the output oscillation frequency by varying the input control voltage. Specifically, a voltage controlled oscillator can control the output oscillation frequency by using a capacitor bank in which multiple capacitors of common specifications are connected in series or parallel to store electric energy, and more specifically, a voltage controlled oscillator can correct the output oscillation frequency to a desired frequency value by adjusting the capacity or the charging and discharging speed of the capacitors that make up the capacitor bank.

Meanwhile, with the rapid development of wireless communication systems and precision measurement systems, high accuracy for the frequencies used in the relevant systems is required due to performance or stability issues in the relevant systems. In particular, PLL (Phase-Locked Loop) is used in many fields as a circuit used for frequency synchronization, but in some circuits where PLL is used, the frequency range that can be compensated is limited to a certain range, so the demand for a wide frequency range required in specific applications is not met.

In addition, as a conventional voltage-controlled oscillator for correcting the frequency, there is a phase-locked loop and method for stably adjusting the frequency band of a voltage-controlled oscillator, such as Korean Patent No. 10-0817286. A conventional voltage-controlled oscillator changes a digital value that changes the band of a VCO according to an input clock and an LPF output signal by utilizing the characteristic of a frequency that is linearly proportional to an input control voltage. However, since a conventional voltage-controlled oscillator must repeatedly change a digital value until the output frequency band of the oscillator reaches a target band, a lot of time is required for frequency correction, and computational resources are wasted.

Therefore, there is a need to develop a technology that can compensate for a wide frequency range and compensate for the frequency in a short period of time, thereby reducing the amount of computation required for frequency compensation.

Republic of Korea Patent No. 10-0817286 (2008.03.20.)

The present invention relates to an oscillator system for compensating frequency by varying a cap bank value, wherein the system derives an optimal cap bank control value based on a lookup table including a difference between an output frequency output from an oscillator for a target frequency desired by a user and a preset constant voltage, and a compensable frequency for each cap bank control value for the preset constant voltage, and primarily compensates the frequency by varying the cap bank value of the oscillator according to the optimal cap bank control value, and finally compensates the frequency output from the oscillator through the compensation voltage by changing the operation mode of a multiplexer which inputs an input control voltage to the oscillator.

In order to solve the above-mentioned problem, in one embodiment of the present invention, an oscillator system for compensating a frequency by varying a Capacitor Bank value is provided, comprising: a frequency compensation circuit unit for deriving an optimal Capacitor Bank control value that enables the oscillator to output a target frequency corresponding to the frequency of an input signal based on a lookup table, transmitting the optimal Capacitor Bank control value to the oscillator, and controlling an operation mode of a Multiplexer unit depending on whether the optimal Capacitor Bank control value is derived; a Multiplexer unit for transmitting a preset constant voltage input from the frequency compensation circuit unit or a compensation voltage input from a PLL circuit unit as an input control voltage to the oscillator depending on the operation mode controlled by the frequency compensation circuit unit; a PLL circuit unit including a phase frequency detector, a charge pump, a low-pass filter, and a divider, and inputting a compensation voltage that controls the voltage of the input signal to the Multiplexer unit; And an oscillator including a cap bank, and varying an initial cap bank value based on the optimal cap bank control value, and correcting a frequency based on the input control voltage; wherein the lookup table includes a compensable frequency for each cap bank control value for a frequency output from the oscillator through the initial cap bank value for the preset constant voltage.

In one embodiment of the present invention, the MUX unit may operate in a first mode in which the preset constant voltage is inputted and transmitted to the oscillator at a time point before the optimal cap bank control value is derived from the frequency correction circuit unit; or in a second mode in which the correction voltage is inputted and transmitted to the oscillator at a time point after the optimal cap bank control value is derived from the frequency correction circuit unit.

In one embodiment of the present invention, the frequency correction circuit unit may include a constant voltage source which inputs the preset constant voltage to the MUX unit; a frequency counter including a first counter which measures the target frequency and a second counter which measures an output frequency output based on an initial cap bank value of the oscillator; a frequency comparator which derives a difference between the output frequency and the target frequency; and a cap bank derivation unit which derives the optimal cap bank control value based on the lookup table through the difference between the output frequency and the target frequency, transmits the optimal cap bank control value to the oscillator, and controls the operation mode of the MUX unit depending on whether the optimal cap bank control value is derived.

In one embodiment of the present invention, the cap bank derivation unit may perform a cap bank control value derivation step of deriving, based on the lookup table, a cap bank control value having the smallest absolute value of a compensable frequency for each of a plurality of cap bank control values and a difference between the output frequency and the target frequency, as the optimal cap bank control value; and a cap bank control value transmission step of transmitting the optimal cap bank control value to the oscillator.

In one embodiment of the present invention, if a frequency output from the oscillator is different from the target frequency based on the optimal cap bank control value, the PLL circuit unit may perform a frequency input step of receiving the frequency output from the oscillator through the divider and transmitting the frequency to the phase frequency detector; and a correction voltage input step of generating a correction voltage through the phase frequency detector, the charge pump, and the low-pass filter and inputting the correction voltage to the multiplexer so that the oscillator can output a signal having the target frequency through a variable cap bank value based on the optimal cap bank control value.

In one embodiment of the present invention, the oscillator system comprises: a frequency measuring unit which measures, for the preset constant voltage, an output frequency output from an oscillator into which an initial capbank value is input; a minimum capbank frequency of a minimum capbank output signal output from the oscillator into which a minimum capbank control value applicable to the oscillator is input; and a maximum capbank frequency of a maximum capbank output signal output from the oscillator into which a maximum capbank control value applicable to the oscillator is input; and calculates a minimum compensable frequency based on a difference between the output frequency and the minimum capbank frequency, and calculates a maximum compensable frequency based on a difference between the output frequency and the maximum capbank frequency; And it may further include a lookup table generation unit which derives a plurality of cap bank control values based on the minimum cap bank control value and the maximum cap bank control value as a preset number, calculates a plurality of compensable frequencies having an equal interval based on the minimum compensable frequency and the maximum compensable frequency, and generates the lookup table by matching each of the plurality of cap bank control values with each of the plurality of compensable frequencies.

In one embodiment of the present invention, by quickly deriving an optimal cap bank control value that configures the inside of an oscillator based on a lookup table including a compensable frequency for each cap bank control value, the time required for frequency compensation of the oscillator can be minimized.

In one embodiment of the present invention, by deriving a difference between a target frequency and an output frequency of an oscillator, and deriving a cap bank control value for a compensable frequency included in the lookup table that is closest to the difference as an optimal cap bank control value, the effect of maintaining the time required for frequency compensation constant regardless of the range of cap bank values constituting the inside of the oscillator can be exerted.

In one embodiment of the present invention, a multiplexer section, which operates in one of two operation modes depending on whether an optimal cap bank control value is derived, controls an input control voltage input to an oscillator according to the operation mode, thereby allowing the oscillator to easily achieve the effect of correcting the frequency.

In one embodiment of the present invention, the time or cost required for constructing the oscillator system of the present invention can be minimized by adding only a frequency correction circuit and a multiplexer unit to the configuration of a conventional frequency correction device.

In one embodiment of the present invention, by generating a lookup table based on values between the minimum compensable frequency and the maximum compensable frequency output for each of the minimum cap bank control value and the maximum cap bank control value applicable to the generator before frequency compensation, the reliability of frequency compensation can be increased.

FIG. 1 schematically illustrates the connection structure of an oscillator system that compensates the frequency by varying the cap bank value according to one embodiment of the present invention.
FIG. 2 schematically illustrates components of an oscillator system that compensates frequency by varying a cap bank value according to one embodiment of the present invention.
Figure 3 schematically illustrates the operation mode of the MUX unit according to one embodiment of the present invention.
FIG. 4 schematically illustrates an execution process for deriving a difference between a target frequency and an output frequency according to one embodiment of the present invention.
FIG. 5 schematically illustrates a lookup table including variable frequencies for each cap bank control value according to one embodiment of the present invention.
Figure 6 schematically illustrates the execution process of a cap bank control value derivation step according to one embodiment of the present invention.
Figure 7 schematically illustrates an execution process for deriving an optimal cap bank control value according to another embodiment of the present invention.
Figure 8 schematically illustrates a process of performing frequency compensation by varying the compensation voltage according to one embodiment of the present invention.
Figure 9 schematically illustrates a process for generating a lookup table according to one embodiment of the present invention.
FIG. 10 schematically illustrates a lookup table generated based on a minimum cap bank control value and a maximum cap bank control value according to one embodiment of the present invention.

Hereinafter, various embodiments and/or aspects are now disclosed with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a general understanding of one or more aspects. It will be recognized, however, by one skilled in the art that such aspect(s) may be practiced without these specific details. The following description and the annexed drawings set forth specific exemplary aspects of one or more aspects in detail. It should be understood, however, that these aspects are exemplary and that any of the various methods of the principles of the various aspects may be utilized, and the description is intended to encompass all such aspects and their equivalents.

Additionally, various aspects and features will be presented by means of systems that may include a number of devices, components, and/or modules, etc. It is also to be understood and appreciated that various systems may include additional devices, components, and/or modules, etc., and/or may not include all of the devices, components, modules, etc. discussed in connection with the drawings.

The terms "embodiment," "example," "aspect," and "example" as used herein are not to be construed as implying that any aspect or design described is better or advantageous over other aspects or designs. The terms "part," "component," "module," "system," and "interface," as used below, generally refer to computer-related entities, and can refer to, for example, hardware, a combination of hardware and software, or software.

Additionally, it should be understood that the terms "comprises" and/or "comprising" imply the presence of the features and/or components, but do not preclude the presence or addition of one or more other features, components and/or groups thereof.

Also, terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are only used to distinguish one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and/or includes a combination of a plurality of related described items or any item among a plurality of related described items.

In addition, in the embodiments of the present invention, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant technology, and shall not be interpreted in an ideal or overly formal meaning unless explicitly defined in the embodiments of the present invention.

FIG. 1 schematically illustrates the connection structure of an oscillator system that compensates the frequency by varying the cap bank value according to one embodiment of the present invention.

The present invention aims to minimize the time and operations required for frequency correction and feedback for frequency correction in an oscillator system, and to perform frequency correction over a wide frequency range. To this end, the oscillator system according to the present invention has a configuration that further includes a frequency correction circuit unit (1000) and a multiplexer unit (2000) in addition to the configuration of a conventional PLL (Phase Locked Loop), as shown in FIG. 1.

Specifically, depending on the characteristics of the capacitor bank (hereinafter referred to as Cap Bank) configured in the oscillator (4000), the frequency range that the oscillator (4000) can output changes differently depending on the Cap Bank value, and the Cap Bank value can be preset according to the capacity or the charge and discharge speed of the capacitor that configures the Cap Bank. That is, if it is determined that a frequency correction of A is necessary based on the frequency output result of the oscillator (4000) configured with the initial Cap Bank, it means that a Cap Bank control value can be derived regarding how much the Cap Bank value should be varied based on the initial Cap Bank value in order to perform the frequency correction of A based on the frequency range output by Cap Bank value of the oscillator (4000).

The frequency correction circuit (1000) uses these characteristics to derive a value required for frequency correction through the difference between the target frequency of an input signal input from an input power supply and the output frequency input from an oscillator (4000), and the present invention is characterized by deriving an optimal cap bank control value that allows the oscillator (4000) to output the target frequency through a lookup table that includes cap bank control values for each value that can be subject to frequency correction.

Meanwhile, in the present invention, the first method of correcting the frequency to the target frequency is a method of correcting the frequency by varying the cap bank value of the oscillator (4000) as described above. However, since there is a frequency range that can be output depending on the cap bank value, and the frequency output from the oscillator (4000) is determined depending on the voltage input to the oscillator (4000) within the corresponding frequency range, the present invention needs to fix the voltage input to the oscillator (4000) in order to first derive the optimal cap bank control value.

In addition, the second method of correcting the frequency to the target frequency in the present invention is a method of correcting the frequency by controlling the voltage input to the oscillator (4000), which is used in a conventional PLL. That is, the present invention is characterized by including a multiplexer (2000) capable of inputting the voltage required for the oscillator (4000) depending on the situation in the oscillator system.

Meanwhile, as an embodiment of the present invention illustrated in FIG. 1, the oscillator (4000) may be adopted as a general voltage-controlled oscillator (VCO) that outputs a frequency determined through charging and discharging of a capacitor including a cap bank and can perform frequency synchronization through a PLL circuit, and as an oscillator (4000) in another embodiment of the present invention, an oscillator (4000) of another form to which the technology of the present invention can be applied may be adopted, but for the convenience of explanation of the present invention, the oscillator (4000) of the present invention described below is based on a voltage-controlled oscillator.

FIG. 2 schematically illustrates components of an oscillator system that compensates frequency by varying a cap bank value according to one embodiment of the present invention.

As illustrated in FIG. 2, an oscillator system for compensating a frequency by varying a Capacitor Bank value, the system comprising: a frequency compensation circuit unit (1000) for deriving an optimal Capacitor Bank control value that enables an oscillator (4000) to output a target frequency corresponding to the frequency of an input signal based on a lookup table, transmitting the optimal Capacitor Bank control value to the oscillator (4000), and controlling an operation mode of a MUX unit (2000) depending on whether the optimal Capacitor Bank control value is derived; a MUX unit (2000) for transmitting a preset constant voltage input from the frequency compensation circuit unit (1000) or a compensation voltage input from the PLL circuit unit (3000) as an input control voltage to the oscillator (4000) depending on the operation mode controlled by the frequency compensation circuit unit (1000); A PLL circuit unit (3000) including a phase frequency detector (3100), a charge pump (3200), a low-pass filter (3300), and a divider (3400), and inputting a correction voltage that controls the voltage of the input signal to the multiplexer unit (2000); and an oscillator (4000) including a cap bank and varying an initial cap bank value based on the optimal cap bank control value and correcting a frequency based on the input control voltage; wherein the lookup table includes a compensable frequency for each cap bank control value with respect to a frequency output from the oscillator (4000) through the initial cap bank value for the preset constant voltage.

In general, since the frequency band output from the oscillator (4000) is preset for each cap bank value that can be configured in the oscillator (4000), in order to compensate for the frequency over a wide frequency band, the present invention varies the cap bank value of the oscillator (4000) as needed, and first of all, it is preferable to derive a cap bank control value in order to vary the initial cap bank value of the oscillator (4000) to a cap bank value that handles a frequency band that includes a target frequency.

That is, the present invention primarily corrects the frequency output from the oscillator (4000) by varying the cap bank value based on the optimal cap bank control value, and then controls the input control voltage input to the oscillator (4000) through a phase frequency detector (3100), a charge pump (3200), a low-pass filter (3300), and a divider (3400) so that the primarily corrected frequency can be finally corrected to a target frequency.

Specifically, the frequency correction circuit unit (1000) includes a frequency counter (1100), a frequency comparator (1200), a cap bank derivation unit (1300), and a constant voltage source (1400). Initially, since the optimal cap bank control value is not derived from the frequency correction circuit unit (1000), the frequency correction circuit unit (1000) transmits a control command to the multiplexer unit (2000) so that the multiplexer unit (2000) operates in a first mode in which the multiplexer unit (2000) receives a preset constant voltage from the constant voltage source (1400).

Under the control of the frequency compensation circuit unit (1000), the MUX unit (2000) operating in the first mode transmits the preset constant voltage to the oscillator (4000), and the oscillator (4000) outputs an output frequency based on an input signal input from the input power supply unit, the preset constant voltage, and an initial cap bank value of an initial cap bank configured internally. However, when the output frequency is different from the target frequency of the input signal, the first counter (1110) included in the frequency counter (1100) measures the target frequency through the input signal, and the second counter (1120) included in the frequency counter (1100) receives the output frequency from the divider (3400), and the frequency comparator (1200) derives the difference between the target frequency and the output frequency and transmits the difference to the cap bank derivation unit (1300).

The cap bank derivation unit (1300) derives a cap bank control value that matches a compensable frequency that is closest to the difference between a target frequency and an output frequency based on a lookup table that includes compensable frequencies for each cap bank control value as an optimal cap bank control value, and transmits the optimal cap bank control value to the oscillator (4000). Meanwhile, the compensable frequency corresponds to a frequency that can be compensated for based on the output frequency when the oscillator (4000) varies the initial cap bank value according to the cap bank control value.

The oscillator (4000) can output a frequency having the same value as the target frequency according to the input control voltage through the varied cap bank by varying the cap bank value based on the optimal cap bank control value, and when the frequency output after varying the cap bank value based on the optimal cap bank control value is different from the target frequency, the multiplexer (2000) operates in the second mode according to the control of the frequency correction circuit (1000), so that a correction voltage for frequency correction is input to the oscillator (4000) through the multiplexer (2000) as the input control voltage by the operation of the PPL circuit. The oscillator (4000) finally corrects the frequency through the input control voltage and outputs an output signal having the target frequency.

Figure 3 schematically illustrates the operation mode of the MUX unit (2000) according to one embodiment of the present invention.

As illustrated in FIG. 3, the MUX unit (2000) operates in a first mode in which the preset constant voltage is inputted at a time point before the optimal cap bank control value is derived from the frequency correction circuit unit (1000) and is transmitted to the oscillator (4000); or in a second mode in which the correction voltage is inputted at a time point after the optimal cap bank control value is derived from the frequency correction circuit unit (1000) and is transmitted to the oscillator (4000).

In addition, the frequency correction circuit unit (1000) includes a cap bank derivation unit (1300) that derives the optimal cap bank control value based on the lookup table through the difference between the output frequency and the target frequency, transmits the optimal cap bank control value to the oscillator (4000), and controls the operation mode of the multiplexer unit (2000) depending on whether the optimal cap bank control value is derived.

Schematically, Fig. 3 (a) illustrates a MUX unit (2000) operating in the first mode, and Fig. 3 (b) illustrates a MUX unit (2000) operating in the second mode.

Specifically, when the frequency compensation circuit unit (1000) does not derive the optimal cap bank control value, as illustrated in (a) of FIG. 3, the cap bank derivation unit (1300) transmits a control command for the operation mode for the first mode to the multiplexer unit (2000), and the multiplexer unit (2000) operates in the first mode by receiving a preset constant voltage from a constant voltage source (1400) and transmitting it as an input control voltage to the oscillator (4000). The oscillator (4000) outputs an output signal based on the initial cap bank value for the preset constant voltage received from the multiplexer unit (2000) as the input control voltage, and the frequency compensation circuit unit (1000) can derive the optimal cap bank control value based on the difference between the output frequency of the corresponding output signal and the target frequency.

In addition, at the point in time when the frequency compensation circuit unit (1000) derives the optimal cap bank control value, as illustrated in (b) of FIG. 3, the cap bank derivation unit (1300) transmits a control command for the operation mode for the second mode to the multiplexer unit (2000), and the multiplexer unit (2000) operates in the second mode by receiving a compensation voltage controlled from the PLL circuit unit (3000) (preferably, a low-pass filter (3300)) and transmitting it to the oscillator (4000) as an input control voltage.

Meanwhile, as an embodiment of the present invention illustrated in (a) to (b) of FIG. 3, the MUX unit (2000) may be configured as a 2X1 MUX, and the MUX may include two input terminals, one output terminal, and one selection signal input terminal. The MUX receives a control command for an operation mode from the cap bank derivation unit (1300) through the selection signal input terminal, receives a preset constant voltage through one input terminal, or receives a compensation voltage controlled by the PLL circuit unit (3000) through the remaining input terminal, and outputs one of the preset constant voltage or compensation voltage as an input control voltage to the oscillator (4000) through the output terminal.

FIG. 4 schematically illustrates an execution process for deriving a difference between a target frequency and an output frequency according to one embodiment of the present invention.

As illustrated in FIG. 4, the frequency compensation circuit unit (1000) includes a constant voltage source (1400) that inputs the preset constant voltage to the MUX unit (2000); a frequency counter (1100) that includes a first counter (1110) that measures the target frequency and a second counter (1120) that measures the output frequency output based on the initial cap bank value of the oscillator (4000); and a frequency comparator (1200) that derives the difference between the output frequency and the target frequency.

Specifically, the frequency of the input signal input from the input power supply to the first counter (1110) corresponds to the target frequency, and the frequency of the output signal of the oscillator (4000) input from the divider (3400) to the second counter (1120) corresponds to the output frequency. Preferably, in order to minimize the difference between the two frequencies in order to meet the purpose of the oscillator system corresponding to frequency synchronization, the first counter (1110) measures the target frequency, the second counter (1120) measures the output frequency, and the frequency comparator (1200) receives the target frequency value measured from the first counter (1110) and the output frequency value measured from the second counter (1120), derives the difference between the two frequencies, and transmits the result to the cap bank derivation unit (1300).

FIG. 5 schematically illustrates a lookup table including variable frequencies for each cap bank control value according to one embodiment of the present invention.

As illustrated in FIG. 5, the lookup table includes a compensable frequency for each cap bank control value for the frequency output from the oscillator (4000) through the initial cap bank value for the preset constant voltage.

Specifically, in order to correct the output frequency based on the preset constant voltage, a lookup table is also generated based on the preset constant voltage (V _fix ). The difference between the target frequency derived from the frequency comparator (1200) and the output frequency means a value that requires compensation in order for the output frequency to be corrected to the target frequency, and the lookup table includes a compensable frequency for each cap bank control value as a value by which the frequency is corrected as the oscillator (4000) varies the cap bank value.

The table illustrated in FIG. 5 is an embodiment of the present invention, where the cap bank control value '0' means that the cap bank value is not varied, preferably, the cap bank value of the oscillator (4000) has not varied from the initial cap bank value, so the compensable frequency is 0. In addition, in the case of the cap bank control value '2', the cap bank control value corresponding to '2' is applied to the initial cap bank of the oscillator (4000), so that the cap bank value varies, which means that the varied cap bank value compensates for the difference between the output frequency corresponding to 20 kHz and the target frequency, so that the oscillator (4000) can output the target frequency. Meanwhile, the cap bank control value in another embodiment of the present invention may be included in the lookup table as a value of a different form, and the unit of the compensable frequency is not limited to kHz and may be included in the lookup table as a different unit depending on the embodiment.

The conventional technology for correcting the frequency by varying the cap bank value requires varying each of a plurality of cap banks one by one and comparing the output frequency output from the oscillator (4000) with the target frequency, so it takes a long time and requires many calculations to correct the frequency. However, the present invention quickly derives a value for which the cap bank must be varied through a lookup table including a compensable frequency for each cap bank control value based on the difference derived once between the output frequency and the target frequency, thereby minimizing the time and calculations required for correcting the frequency.

Fig. 6 schematically illustrates an execution process of a cap bank control value derivation step according to one embodiment of the present invention. In addition, Fig. 7 schematically illustrates an execution process of deriving an optimal cap bank control value according to another embodiment of the present invention.

As illustrated in FIG. 6, the cap bank derivation unit (1300) performs a cap bank control value derivation step of deriving, based on the lookup table, a cap bank control value having the smallest absolute value of a compensable frequency for each of a plurality of cap bank control values and a difference between the output frequency and the target frequency as the optimal cap bank control value; and a cap bank control value transmission step of transmitting the optimal cap bank control value to the oscillator (4000).

Specifically, as an embodiment of the present invention, the x-axis of the graph illustrated in FIG. 6 represents an input control voltage input to the oscillator (4000), which corresponds to a preset constant voltage input from a constant voltage source (1400) or a compensation voltage controlled through the PLL circuit (3000) depending on the operation mode of the MUX unit (2000). In addition, the frequency corresponding to the y-axis represents the frequency of an output signal that the oscillator (4000) can output through the variable cap bank by applying each of the cap bank control values '0' to '6' applicable to the oscillator (4000). More specifically, in the embodiment illustrated in FIG. 6, the difference between the output frequency output from the oscillator (4000) constituting the initial cap bank corresponding to the cap bank control value '0' and the target frequency is derived from the frequency comparator (1200), and the difference corresponds to the value of 'd ₁ '.

Preferably, for a preset constant voltage (V _fix ), the difference between the frequency according to the input control voltage of the cap bank varied according to the cap bank control value '2' and the output frequency output from the oscillator (4000) constituting the initial cap bank is 'd ₂ ', which corresponds to the same value as the compensable frequency matched to the cap bank control value '2' included in the lookup table. Similarly, for a preset constant voltage (V _fix ), the difference between the frequency according to the input control voltage of the cap bank varied according to the cap bank control value '3' and the output frequency output from the oscillator (4000) constituting the initial cap bank is 'd ₃ ', which corresponds to the same value as the compensable frequency matched to the cap bank control value '3' included in the lookup table.

For a preset constant voltage (V _fix ), after the frequency comparator (1200) derives the difference (d ₁ ) between the output frequency and the target frequency, the cap bank derivation unit (1300) can derive the cap bank control value '3', which is matched to the compensable frequency (d ₃ ) corresponding to the value having the smallest difference from the value of the difference (d ₁ ) between the output frequency and the target frequency among the compensable frequencies matched to the cap bank control values '0' to '6' based on the lookup table, as the optimal cap bank control value.

Meanwhile, in another embodiment of the present invention, the lookup table may include an outputtable frequency for each capbank value for a preset constant voltage, and the graph illustrated in FIG. 7 shows the frequency for each capbank value for the input control voltage. When the capbank value is '2', the difference between the output frequency output by the oscillator (4000) and the target frequency is 'd ₄ ', and when the capbank value is '3', the difference between the output frequency output by the oscillator (4000) and the target frequency is 'd ₅ ', for each of the outputtable frequencies for a plurality of capbank values, the capbank value '3' matching the lookup table with respect to 'd ₅ ', which has the smallest difference from the target frequency, may be derived as the optimal capbank value and input to the oscillator (4000). Thereafter, the oscillator (4000) primarily corrects the frequency by changing the initial capbank value to the optimal capbank value.

Figure 8 schematically illustrates a process of performing frequency compensation by varying the compensation voltage according to one embodiment of the present invention.

As illustrated in FIG. 8, when the frequency output from the oscillator (4000) is different from the target frequency based on the optimal cap bank control value, the PLL circuit unit (3000) performs a frequency input step of receiving the frequency output from the oscillator (4000) through the divider (3400) and transmitting it to the phase frequency detector (3100); and a correction voltage input step of generating a correction voltage through the phase frequency detector (3100), the charge pump (3200), and the low-pass filter (3300) and inputting the correction voltage to the multiplexer (2000) so that the oscillator (4000) can output a signal having the target frequency through a variable cap bank value based on the optimal cap bank control value.

Specifically, since the optimal cap bank control value is a cap bank control value that enables a frequency adjacent to the target frequency to be output from the oscillator (4000) within a frequency band where output is possible for a preset constant voltage, even after the oscillator (4000) that receives the preset constant voltage as an input control voltage receives the optimal cap bank control value and varies the cap bank value, there may be a slight difference between the output frequency and the target frequency.

In this case, as shown in the graph in Fig. 8, as the MUX unit (2000) performs from the first mode to the second mode and varies the input control voltage input to the oscillator (4000), the oscillator (4000) can output an output signal having a target frequency based on the frequency characteristic that varies according to the voltage.

Meanwhile, as another embodiment of the present invention, when the oscillator (4000) cannot vary the cap bank value according to the optimal cap bank control value due to an error in the internal circuit of the oscillator (4000), the oscillator (4000) varies the cap bank value based on a cap bank control value that is adjacent to the optimal cap bank control value and handles a frequency band including the target frequency regardless of a preset constant voltage. Thereafter, based on the frequency characteristic that varies according to the voltage for the corresponding cap bank value, the input control voltage input to the oscillator (4000) through the PLL circuit unit (3000) can be varied so that the oscillator (4000) can output an output signal having the target frequency.

Figure 9 schematically illustrates a process for generating a lookup table according to one embodiment of the present invention.

As illustrated in FIG. 9, the oscillator system comprises: a frequency measuring unit which measures, for the preset constant voltage, an output frequency output from an oscillator (4000) into which an initial cap bank value is input; a minimum cap bank frequency of a minimum cap bank output signal output from the oscillator (4000) into which a minimum cap bank control value applicable to the oscillator (4000) is input; and a maximum cap bank frequency of a maximum cap bank output signal output from the oscillator (4000) into which a maximum cap bank control value applicable to the oscillator (4000) is input; and calculates a minimum compensable frequency based on a difference between the output frequency and the minimum cap bank frequency, and calculates a maximum compensable frequency based on a difference between the output frequency and the maximum cap bank frequency; And it further includes a lookup table generation unit which derives a plurality of cap bank control values as a preset number based on the minimum cap bank control value and the maximum cap bank control value, calculates a plurality of compensable frequencies having an equal interval based on the minimum compensable frequency and the maximum compensable frequency, and generates the lookup table by matching each of the plurality of cap bank control values with each of the plurality of compensable frequencies.

In outline, Fig. 9 (a) illustrates an execution process for calculating a minimum compensable frequency for a minimum cap bank control value, and Fig. 9 (b) illustrates an execution process for calculating a maximum compensable frequency for a maximum cap bank control value.

Preferably, the cap bank value of the oscillator (4000) is determined according to the internal configuration of the oscillator (4000), and may be configured as a minimum cap bank value at which the oscillator (4000) can output a minimum frequency or a maximum cap bank value at which the oscillator (4000) can output a maximum frequency, depending on the embodiment. As an embodiment of the present invention, a minimum cap bank control value for the minimum cap bank value based on an initial cap bank value configured in the oscillator (4000); and a maximum cap bank control value for the maximum cap bank value based on the initial cap bank value; may be preset according to the internal configuration of the oscillator (4000), and thus the present invention may generate a lookup table using this. Preferably, the lookup table should include a compensable frequency for each cap bank control value for a preset constant voltage, and therefore, the oscillator (4000) described below in FIGS. 9 and 10 corresponds to an oscillator (4000) that receives a preset constant voltage and outputs a frequency.

As illustrated in (a) of FIG. 9, the cap bank derivation unit (1300) inputs (①) a minimum cap bank control value to the oscillator (4000), the oscillator (4000) varies the cap bank value according to the minimum cap bank control value and outputs (②) a minimum cap bank output signal, and the frequency measurement unit measures each of the output frequency output by the oscillator (4000) as the initial cap bank value and the minimum cap bank frequency of the minimum cap bank output signal, calculates a minimum compensable frequency corresponding to the difference between the output frequency and the minimum cap bank frequency, and transmits it to the lookup table generation unit (③).

In addition, as illustrated in (b) of FIG. 9, the cap bank derivation unit (1300) inputs (①) a maximum cap bank control value to the oscillator (4000), the oscillator (4000) varies the cap bank value according to the maximum cap bank control value and outputs (②) a maximum cap bank output signal, and the frequency measurement unit measures each of the output frequency output by the oscillator (4000) as the initial cap bank value and the maximum cap bank frequency of the maximum cap bank output signal, calculates a maximum compensable frequency corresponding to the difference between the output frequency and the maximum cap bank frequency, and transmits it to the lookup table generation unit (③).

FIG. 10 schematically illustrates a lookup table generated based on a minimum cap bank control value and a maximum cap bank control value according to one embodiment of the present invention.

Figure 10 schematically illustrates a lookup table generated by a lookup table generation unit based on the minimum cap bank control value, maximum cap bank control value received from the cap bank derivation unit (1300), the minimum compensable frequency received from the frequency measurement unit, and the maximum compensable frequency.

Specifically, the lookup table illustrated in FIG. 10 is an embodiment of the present invention, in which the minimum compensable frequency is 0 kHz and the maximum compensable frequency is calculated as 1000 kHz. Since the minimum compensable frequency is calculated based on the minimum cap bank control value, it is preferable that it matches the minimum cap bank control value, and since the maximum compensable frequency is calculated based on the maximum cap bank control value, it is preferable that it matches the maximum cap bank control value.

In addition, the lookup table generation unit generates a preset number of a plurality of cap bank control values included in the lookup table, and the preset number can be determined according to the configuration of the cap bank configured in the oscillator (4000) of the present invention, and since the lookup table includes a compensable frequency for each cap bank control value, a preset number of compensable frequencies included in the lookup table are also generated. More specifically, the plurality of compensable frequencies are generated based on the minimum compensable frequency and the maximum compensable frequency in the preset number, and it is preferable that each of the plurality of compensable frequencies is generated with a constant difference in the form of equal intervals.

Meanwhile, in another embodiment of the present invention, the lookup table generation unit may generate the lookup table through a different execution process, rather than generating the lookup table through the execution process of the above-described embodiment. For example, by generating the lookup table based on the ground truth that measures all output frequencies in each of a plurality of cap bank values applicable to the oscillator (4000), the lookup table may be utilized for an oscillator system including an oscillator (4000) configured with the same cap bank as the cap bank of the oscillator (4000).

In one embodiment of the present invention, by quickly deriving an optimal cap bank control value that configures the inside of an oscillator based on a lookup table including a compensable frequency for each cap bank control value, the time required for frequency compensation of the oscillator can be minimized.

In one embodiment of the present invention, by deriving a difference between a target frequency and an output frequency of an oscillator, and deriving a cap bank control value for a compensable frequency included in the lookup table that is closest to the difference as an optimal cap bank control value, the effect of maintaining the time required for frequency compensation constant regardless of the range of cap bank values constituting the inside of the oscillator can be exerted.

In one embodiment of the present invention, a multiplexer section, which operates in one of two operation modes depending on whether an optimal cap bank control value is derived, controls an input control voltage input to an oscillator according to the operation mode, thereby allowing the oscillator to easily achieve the effect of correcting the frequency.

In one embodiment of the present invention, the time or cost required for constructing the oscillator system of the present invention can be minimized by adding only a frequency correction circuit and a multiplexer unit to the configuration of a conventional frequency correction device.

In one embodiment of the present invention, by generating a lookup table based on values between the minimum compensable frequency and the maximum compensable frequency output for each of the minimum cap bank control value and the maximum cap bank control value applicable to the generator before frequency compensation, the reliability of frequency compensation can be increased.

Although the embodiments have been described above by way of limited examples and drawings, those skilled in the art can make various modifications and variations from the above description. For example, appropriate results can be achieved even if the described techniques are performed in a different order from the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form from the described method, or are replaced or substituted by other components or equivalents. Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

Claims (6)

As an oscillator system that compensates the frequency by varying the capacitor bank value,
A frequency correction circuit section which derives an optimal cap bank control value for the oscillator to output a target frequency corresponding to the frequency of an input signal based on a lookup table, transmits the optimal cap bank control value to the oscillator, and controls the operation mode of the multiplexer section depending on whether the optimal cap bank control value is derived;
A MUX unit that transmits a preset constant voltage input from the frequency correction circuit unit or a correction voltage input from the PLL circuit unit as an input control voltage to the oscillator according to an operation mode controlled by the frequency correction circuit unit;
A PLL circuit section including a phase frequency detector, a charge pump, a low-pass filter, and a divider, and inputting a compensation voltage that controls the voltage of the input signal to the multiplexer section; and
An oscillator including a cap bank, varying an initial cap bank value based on the optimal cap bank control value, and correcting a frequency based on the input control voltage;
The above frequency compensation circuit unit includes a constant voltage source that inputs the preset constant voltage to the MUX unit;
The above lookup table includes the preset constant voltage, and for the preset constant voltage, includes a compensable frequency for each cap bank control value for the frequency output from the oscillator through the initial cap bank value,
The above max part is,
A first mode in which the preset constant voltage is input as the input control voltage and transmitted to the oscillator at a time before the optimal cap bank control value is derived from the frequency compensation circuit; and
An oscillator system that operates in a second mode in which the compensation voltage controlled by the PLL circuit is input as the input control voltage and transmitted to the oscillator at a point in time after the optimal cap bank control value is derived from the frequency compensation circuit.
delete In claim 1,
The above frequency correction circuit part,
A frequency counter including a first counter for measuring the target frequency and a second counter for measuring the output frequency output based on the initial cap bank value of the oscillator;
A frequency comparator for deriving the difference between the output frequency and the target frequency; and
An oscillator system further comprising a cap bank derivation unit that derives the optimal cap bank control value based on the lookup table through the difference between the output frequency and the target frequency, transmits the optimal cap bank control value to the oscillator, and controls the operation mode of the multiplexer unit depending on whether the optimal cap bank control value is derived.
In claim 3,
The above cap bank derivation part is,
Based on the above lookup table, a cap bank control value derivation step for deriving a cap bank control value having the smallest absolute value of a compensable frequency for each of a plurality of cap bank control values; and a difference between the output frequency and the target frequency; as the optimal cap bank control value; and
An oscillator system that performs a cap bank control value transmission step of transmitting the above optimal cap bank control value to the oscillator.
In claim 1,
If the frequency output from the oscillator is different from the target frequency based on the above optimal cap bank control value,
The above PLL circuit part,
A frequency input step for receiving a frequency output from the oscillator through the above divider and transmitting it to the phase frequency detector; and
An oscillator system, which performs a compensation voltage input step of generating a compensation voltage through the phase frequency detector, charge pump, and low-pass filter and inputting the compensation voltage to the MUX unit so that the oscillator can output a signal having the target frequency through a variable cap bank value based on the optimal cap bank control value.
In claim 1,
The above generator system is,
A frequency measuring unit which measures an output frequency output from an oscillator into which an initial cap bank value is input for the above preset constant voltage; a minimum cap bank frequency of a minimum cap bank output signal output from the oscillator into which a minimum cap bank control value applicable to the oscillator is input; and a maximum cap bank frequency of a maximum cap bank output signal output from the oscillator into which a maximum cap bank control value applicable to the oscillator is input; and calculates a minimum compensable frequency based on a difference between the output frequency and the minimum cap bank frequency, and calculates a maximum compensable frequency based on a difference between the output frequency and the maximum cap bank frequency; and
An oscillator system further comprising a lookup table generation unit which derives a plurality of cap bank control values based on the minimum cap bank control value and the maximum cap bank control value as a preset number, calculates a plurality of compensable frequencies having an equal interval based on the minimum compensable frequency and the maximum compensable frequency, and generates the lookup table by matching each of the plurality of cap bank control values with each of the plurality of compensable frequencies.