KR20020086789A - A Filter Auto-Controlling System and Methods - Google Patents

Abstract

PURPOSE: A system and a method for controlling automatically a filter are provided to control a characteristic of a filter by using an automatic filter control circuit for controlling automatically impedance and capacitance according to voltage or current. CONSTITUTION: A filter portion(20) is used for filtering inputted RF signals. An RF signal of broadband is inputted into the filter portion(20). A filter measuring portion(30) is used for measuring a characteristic of the filter portion(20) by using a signal outputted from the filter portion(20). A calculation portion(40) is used for comparing a measured value of the filter measuring portion(30) with a setup value of the filter portion(20), calculating a deviation according to a compared value, and generating a control signal. A control portion(50) controls the filter portion(20) by controlling an input signal of the filter portion(20) according to the control signal generated from the calculation portion(40). The control portion(50) is formed with a CPU(51), a memory portion(52), and a converter portion(53).

Description

A filter auto-controlling system and methods

The present invention relates to a filter automatic adjustment system and a method thereof. In particular, a circuit and an algorithm for automatically adjusting a center frequency by using an element whose capacitance or resistance is changed by adjusting voltage or current are provided. A system and method thereof are provided.

The configuration of a conventional bandpass filter composed of a basic RLC parallel resonant circuit is shown in FIG. That is, one end is connected in parallel to an input terminal to which a signal is input, and the other end thereof is a grounded inductor I1, and the other end thereof is connected in parallel with the inductor I1 and the other end thereof is a grounded variable resistor R1. The variable resistor R1 and one end are connected in parallel, and the other end thereof is composed of a grounded variable capacitor C1.

Here, the bandwidth selection circuit according to the band pass filter is configured as shown in FIG. That is, the inductor (I10) connected in parallel to the input terminal, the variable resistor unit (R10) in parallel with the inductor, and the variable capacitor unit (C10) having a variable capacitance connected in parallel with the variable resistor unit (R10), the user As required, the impedance and capacitance of the variable resistor unit R10 and the capacitor unit C10 are changed to allow the center frequency and bandwidth to be selected. Here, the variable resistor unit C10 includes a switch S10 that is switched according to a signal of a controller input from the outside to change the resistance value.

Here, the variable resistor portion R10 is composed of a plurality of resistors R11 to R1n to change its impedance under the control of the controller.

In addition, in the conventional bandpass filter configured as described above, the center frequency Fc and the 3kHz-passband bandwidth BW are represented by the following first and second equations.

Fc = 1 / (2 * π {(L * C)} ^ {1/2})

BW (3㏈) = 1 / (2 * π * R * C)

Herein, L, R, and C represent total inductance, impedance, and capacitance of the circuit shown in FIG. 1, respectively.

However, in the conventional circuit configured as described above, the variable capacitance of the capacitor is adjusted to adjust the center frequency, and the impedance of the variable resistor is manually adjusted by using a adjusting rod to adjust the bandwidth. There is a problem that can not do.

In addition, when implementing multiple bandwidths with the same filter, there is a problem that a separate bandwidth selection circuit is required for each bandwidth. In the case of the variable resistor or the variable capacitor, the component size is large and occupies a large area on the PCB. In the case of the bandwidth selection circuit, a large number of components are used, resulting in a cost increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide a filter automatic adjustment circuit which automatically adjusts impedance and capacitance according to a voltage or a current. The present invention provides a filter automatic adjustment system and a method for measuring and adjusting characteristics.

1 is a circuit diagram showing the configuration of a conventional band pass filter,

2 is a circuit diagram showing a configuration of a conventional bandwidth selection circuit;

3 is a block diagram showing the configuration of a filter automatic adjustment system according to the present invention;

4 is a circuit diagram showing a circuit of the automatic adjustment filter according to the present invention;

5 is a flowchart showing an operation procedure of the filter automatic adjustment system according to the present invention performed to set a band pass filter;

6A and 6B are flowcharts illustrating an operation procedure of a method for automatically adjusting a filter according to the present invention, which is performed to measure characteristics of a band pass filter and to reset a set value of the band pass filter accordingly.

<Explanation of symbols on main parts of the drawings>

20 filter unit 21 center frequency determination unit

25: bandwidth determining unit 30: filter measuring unit

40: calculation unit 50: control unit

51: CPU52: memory section

53: converter section

According to a feature of the automatic adjustment filter according to the present invention for solving the above problems, the center frequency determination unit consisting of a variable capacitor capacitor whose capacitance changes according to the first signal input from the outside so that the center frequency is automatically adjusted, and the center It is composed of a bandwidth determination unit consisting of a variable resistance unit for changing the impedance according to the second signal input from the outside so that the bandwidth is automatically adjusted around the frequency.

In addition, according to a feature of the filter automatic adjustment system according to the present invention, a filter unit for filtering the input RF signal. A filter measuring unit measuring a characteristic of the filter unit; An operation unit for comparing a value measured by the filter measuring unit with a setting value of the filter unit and generating a control command to automatically adjust the filter unit according to the deviation thereof; And a control unit generating a signal for adjusting the filter unit according to a control command of the operation unit and controlling the filter unit to have a set value.

Further, according to a feature of the automatic filter adjustment method according to the present invention, the first step of setting the frequency band to be filtered through the filter unit, the second step of measuring the characteristics of the filter unit set in the first step, A third step of calculating a deviation between the characteristic of the filter part and the set value according to the value measured in step 2, and a fourth step of generating a signal controlling the filter part according to the deviation calculated in the third step; And a fifth step of changing the setting of the filter unit according to the signal generated in the fourth step.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the filter automatic adjustment system according to the present invention includes a filter unit 20 for filtering an input RF signal, and a wideband RF signal input to the filter unit 20, and accordingly, at the filter unit. Filter measurement unit 30 for measuring the characteristics of the filter unit through the output signal and the value measured by the filter measurement unit 30 is compared with the set value of the filter unit 20 and calculates the deviation accordingly An operation unit 40 for generating a control signal such that the setting of the filter unit 20 is controlled; The controller 50 adjusts and controls the signal input to the filter unit 20 according to the control signal generated by the operation unit 40.

Here, the controller 50 may include a CPU 51 receiving a control signal from the calculator, a memory 52 storing the characteristic setting values of the filter unit 20, and converting the setting values into an analog direct current. The converter unit 53 converts the voltage and outputs the voltage to the filter unit 20.

In addition, as shown in FIG. 4, the filter unit 20 is formed of a variable capacitance capacitor unit whose capacitance varies according to the first signal VC1 input through the converter unit 53 so that the center frequency is automatically adjusted. A bandwidth determining unit 25 including a frequency determining unit 21 and a variable resistance unit whose impedance is changed according to the second signal VC2 input from the converter unit 53 so that the bandwidth is automatically adjusted around the center frequency; The inductor unit 29 is connected to the bandwidth determiner 25 in parallel.

In more detail, the center frequency determiner 21 includes an inductor L21 to which the first signal VC1 is input from the converter 53 and the first signal to be input through the inductor L21. A variable capacitance capacitor part C21 connected in parallel with the inductor part L21 and a terminal of the inductor part L21 in parallel with each other so as to change a capacitance according to VC1 to receive a DC component of the first signal VC1. It consists of a capacitor portion (C22) for blocking.

In addition, the bandwidth determining unit 25 is connected to the inductor unit L25 to which the second signal VC2 is input from the converter unit 53 and the inductor unit L25 in one end in parallel to the second signal. And a variable resistor portion R25 whose impedance is changed in accordance with VC2. One end of the inductor part L25 is connected in parallel to the capacitor part C25 that blocks the DC component of the second signal VC2.

When the wideband RF signal output from the filter measuring unit 30 is input through the input terminal 20a, the filter unit 20 filters the wideband RF signal according to its characteristics and outputs the filtered signal to the output terminal 20b. Output to the filter measuring unit 30 to allow the filter measuring unit 30 to measure the characteristics of the filter.

Looking at the operation of the present invention configured as described above are as follows.

Fig. 5 shows the operation procedure of the present filter automatic adjustment system performed to set the band pass filter.

First, a set value of a filter to be selected in the first step, that is, a set value of the center frequency and the bandwidth of the filter is input to the calculator. (S1)

In a second step, the CPU reads a DAC code value from the memory unit, which is a signal for controlling the setting of the selected filter according to the specification of the filter input to the calculating unit in the first step. (S2)

In the third step, the CPU transmits the DAC code value read from the memory unit to the converter unit. (S3)

In the fourth step, the converter unit applies the first signal and the second signal in the form of DC voltage to adjust the setting of the filter unit according to the DAC code value transmitted in the third step to the filter unit. (S4)

FIG. 6 shows an operation procedure of the filter automatic adjustment method according to the present invention, which is performed to measure the characteristics of the band pass filter and to reset the set value of the band pass filter.

First, in the eleventh step, the filtering center frequency Fc of the filter is set to 10.7 MHz ± 1.5 kHz and the bandwidth BW is set to 10 kHz ± 1.5 kHz. (S11)

In a twelfth step, a center frequency, a span, and an output level of the filter measuring unit are set. (S12)

In a thirteenth step, the CPU transmits a DAC code as set in the eleventh step to the converter unit. (S13)

In the fourteenth step, the filter measuring unit finds the frequency F1 at the peak value as the filter characteristic set in accordance with the DAC code transmitted to the converter unit is output in the thirteenth step. (S14)

In the fifteenth step, the calculating unit reads the peak-to-peak frequency F1 of the filter measuring unit. (S15)

In the sixteenth step, the calculator calculates a frequency deviation FΔ according to the frequency F1 read in the fifteenth step. (S16)

In the seventeenth step, the calculating unit checks whether an absolute value of the frequency deviation FΔ is less than 1.5 Hz and satisfies a specification. (S17)

If the frequency deviation FΔ does not satisfy the specification in the seventeenth step, the operation unit checks whether the frequency deviation FΔ is positive in the eighteenth step. (S18)

If the frequency deviation FΔ is not positive in the eighteenth step, in operation 19, the operation unit generates a control command for changing a DAC code value so that the first signal VC1 input to the filter unit becomes high. do. (S19)

On the other hand, when the frequency deviation FΔ is positive in the eighteenth step, in operation 20, the calculator generates a control command for changing the DAC code value such that the first signal VC1 input to the filter unit is lowered. (S20)

In the twenty-first step, the calculator transmits the changed DAC code to the CPU according to the control command generated in the nineteenth or twenty steps according to the frequency deviation FΔ. (S21)

Meanwhile, when the frequency deviation FΔ satisfies the specification in step 17, the DAC code value for bandwidth adjustment is extracted. (S22)

In a twenty-third step, the filter measuring unit sets the frequency width according to the selected bandwidth. (S23)

In a twenty-fourth step, the filter measuring unit measures the bandwidth BW1 between two points which are 3 dB lower than the peak value. (S24)

In operation 25, the calculator reads the bandwidth BW1 measured by the filter measurer. (S25)

In operation 26, the calculator calculates a bandwidth deviation BWΔ of the bandwidth. (S26)

In the twenty-seventh step, the calculating unit checks whether the absolute value of the bandwidth deviation (BWΔ) obtained in the twenty-sixth satisfies the specification as 1.5 dB or less. (S27)

If the bandwidth deviation BWΔ does not satisfy the specification in step 27, the operation unit checks whether the bandwidth deviation BWΔ is positive in step 28. (S28)

If the bandwidth deviation BWΔ is not positive in the 28th step, in operation 29, the operation unit generates a control command for changing a DAC code value such that the second signal VC2 input to the filter unit becomes high. do. (S29)

On the other hand, if the bandwidth deviation BWΔ is positive in the twenty-eighth step, in operation 30, the calculator generates a control command for changing the DAC code value so that the second signal VC2 input to the filter unit is lowered. (S30)

In operation 31, the calculator transmits the DAC code changed in operation 29 or operation 30 to the CPU according to the bandwidth deviation BWΔ. (S31)

In a thirty-second step, the bandwidth is changed to the next bandwidth to be set (e.g., BW = 3 ms, 1 ms, 300 ms). Here, if the bandwidth deviation BWΔ satisfies the specification in step 27, the procedure proceeds to step 32. (S32)

In step 33, it is checked whether the bandwidth setting is completed. (S33)

If the bandwidth setting is completed in the thirty-third step, all procedures are terminated. If the bandwidth is not completed, the subsequent procedure is repeated from the twenty-third step.

In the present invention configured and operated as described above, the variable capacitor and the variable resistor may be constituted by a varactor and a PIN diode, respectively. That is, the variable capacitance for determining the center frequency may be implemented by adjusting the voltage applied to the varactor, and the variable resistor for determining the bandwidth is a resistance according to the current flowing through the PIN diode by adjusting the voltage applied to the PIN diode. This can be achieved by adjusting the value.

In addition, the filter measuring unit may be a spectrum analyzer equipped with a network analyzer or a tracking generator as a measuring instrument capable of measuring the characteristics of the filter. The computing unit may be configured as a PC, where the PC controls the filter measuring unit and the CPU. Finally, as the filter is finished, the memory unit stores the DAC code values corresponding to the first and second signals. The converter unit converts the DAC code value received from the CPU into a DC voltage and applies the first and second signals, which are voltage adjustment signals, to the filter unit.

According to the filter automatic adjustment system and method thereof of the present invention configured as described above, an RLC parallel resonant circuit is constructed using a capacitor having a variable capacitance and a PIN diode having a variable resistance, and the variable capacitance and the variable resistor are automatically By making adjustments, the process time is shortened during filter manufacturing, and even if you are not an experienced user, you can always obtain the same filter output, and it is easy to correct the characteristics of the filter according to the change of ambient temperature of the circuit. This reduction has the effect of reducing the size of the implemented circuit.

Claims (11)

A filter unit for filtering an input RF signal; A filter measuring unit measuring a characteristic of the filter unit; An operation unit for comparing the value measured by the filter measuring unit with a set characteristic value of the filter unit and generating a control command to automatically adjust the filter unit according to the deviation; And a control unit generating a signal for adjusting the filter unit according to a control command of the calculating unit and controlling the filter unit to have a set value. The method of claim 1, The control unit includes a CPU to which a control command is input from the operation unit; A memory unit for storing characteristic setting values of the filter unit; And a converter configured to convert the set value into an analog DC voltage and output the converted value to the filter unit. A center frequency determining unit including a variable capacitance capacitor unit whose capacitance varies according to a first signal input from the outside so that the center frequency is automatically adjusted; A bandwidth determining unit including a variable resistance unit whose impedance is changed according to a second signal input from the outside so that the bandwidth is automatically adjusted around the center frequency; And an inductor unit connected in parallel to the bandwidth determination unit. The method of claim 3, wherein The automatic adjustment filter may include a wideband signal input unit to which a wideband RF signal is input to the center frequency determiner and the bandwidth determiner so as to measure characteristics of the center frequency and the bandwidth of the filter determined by the center frequency determiner and the bandwidth determiner; And a filter characteristic output unit for outputting the filtered signal accordingly. The method of claim 3, wherein The center frequency determiner and the inductor unit to which the first signal is input from the outside; A variable capacitor capacitor connected in parallel with the inductor to change the capacitance according to the first signal input through the inductor; And an inductor unit and one end connected in parallel to each other to include a capacitor unit to block a DC component of the first signal. The method of claim 3, wherein The bandwidth determining unit includes an inductor unit to which the second signal is input from the outside; A variable resistor unit having one end connected to the inductor unit in parallel to change an impedance according to the second signal; And a capacitor unit having one end connected in parallel with the inductor unit to block a DC component of the second signal. A first step of setting a frequency band to be filtered through the filter unit; A second step of measuring characteristics of the filter unit set in the first step; A third step of calculating a deviation between the characteristic of the filter part and the set value according to the value measured in the second step; A fourth step of generating a signal for controlling the filter part according to the deviation calculated in the third step; And a fifth step of changing the setting of the filter unit according to the signal generated in the fourth step. The method of claim 7, wherein And in the second step, the filter unit measures the center frequency of filtering and the bandwidth thereof. The method of claim 7, wherein And in the third step, the measured center frequency and the bandwidth of the filter unit and a deviation between the set center frequency and the bandwidth are calculated. The method of claim 7, wherein And automatically generating a signal such that the magnitude of the voltage input to the filter unit varies according to the calculated deviation of the third step. The method of claim 7, wherein In the fifth step, as the voltage of different magnitude is inputted according to the signal of the fourth step, capacitance and impedance are changed so that the center frequency and bandwidth of the signal filtered by the filter are changed and set. .