KR101662563B1 - Gaussian filter array using a variable component and method for tunning the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Gaussian filter array using a variable element and a tuning method thereof, and more particularly, to a Gaussian filter array using a variable element for adjusting a value of a variable element to attenuate ringing noise, .
To this end, the present invention includes a plurality of variable inductors connected in series and a plurality of variable capacitors connected in parallel to each of the variable inductors, thereby varying the values of the variable inductors and the variable capacitors, thereby attenuating the ringing noise.

Description

[0001] The present invention relates to a Gaussian filter array using a variable element and a tuning method using the variable element.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Gaussian filter array using a variable element and a tuning method thereof, and more particularly, to a Gaussian filter array using a variable element for adjusting a value of a variable element to attenuate ringing noise, .

2. Description of the Related Art In recent years, rapid technological development of semiconductors, electronics, and computers has made it possible to make lighter, smaller, faster, and wider electric and electronic devices. Such electronic devices can be operated with a small driving energy, but they also react sensitively to minute electromagnetic waves generated due to artificial control (natural phenomenon), resulting in malfunction.

In addition, as many electrical and electronic devices have become popular in various fields of society, the density of electromagnetic waves increases, and the electromagnetic wave environment becomes worse. In this way, there are many problems such as equipment that is installed in a poor radio wave environment does not operate as originally intended, causing confusion in the society or suggesting the cause of human disorder. Therefore, in recent years, there is an increasing demand for an effective filter for attenuating noise.

Among such noise, ringing noise means that there is an undesired oscillation in the generated signal and it occurs mainly in the circuit. There are various reasons for generating ringing noise, but it is known that parasitic oscillation occurs mainly due to inductance and capacitance in the circuit other than the design, and resonance frequency signals of the oscillation are mixed.

On the other hand, the transfer function distortion in the Gaussian filter composed of the inductor and the capacitor (LC component) means that an error occurs in the expected LC value. However, when ringing occurs in a multi-order, for example, a 10 < th > order Gaussian filter, there is a problem in that it can not be known exactly in which region or which element occurred. In addition, since the transfer function of the 10th order Gaussian filter is very complicated, there is a problem that it takes a lot of time and effort to find an error-correcting device by directly calculating the transfer function.

The paper described in the following prior art documents cascaded four sallen-key lowpass filters. Each of the second order sallen-key lowpass filters is negatively fed with a second order sallen-key lowpass filter connected to the output of the second order sallen-key lowpass filter. Is not changed.

When constructed as described above, the multiplication of all four transfer functions becomes the same as the transfer function of the connected whole filter. Since the RC component deviation of each filter does not affect the other filters because the Selenium key low pass filter is designed according to the quality factor of each filter and then it is connected in a circuit, Distortion can be prevented.

However, the prior art document has a problem in that an external voltage must be supplied to an op-amp, which is an active element, and it is difficult to correct in real time.

Also, the prior art document has a problem that it is difficult to apply to various bandwidths because the system is complicated and the band width is limited by the gain dependency of the operational amplifier.

delete

Paper 1: Jian, G. & Jie, Z. in Information Technology and Computer Science (ITCS), 2010 Second International Conference on. 247-249 (IEEE).

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the conventional art as described above, and it is an object of the present invention to provide a variable array device capable of effectively removing ringing noise without an external voltage by constituting a filter array only by passive variable elements. And a method of tuning the same.

It is still another object of the present invention to provide a Gaussian filter array using a variable element that can easily obtain a signal close to an ideal output by effectively varying the value of the variable inductor and the variable capacitor to effectively reduce the ringing noise and a tuning method thereof .

To this end, the Gaussian filter array using the variable element according to the present invention includes a plurality of variable inductors connected in series and a plurality of variable capacitors connected in parallel to each of the variable inductors.

In the variable inductor according to the embodiment of the present invention, a signal is applied to the front end and a signal is output to the rear end. The front end of the variable capacitor is connected in parallel to the front end of the variable inductor, and the rear end is connected to the ground And the variable capacitor is connected in parallel to either one of a front end and a rear end of the variable inductor.

Also, the Gaussian filter array using the variable element according to the embodiment of the present invention may include: a first variable inductor connected in series to a rear end of a first through-hole for impedance matching; A first variable capacitor whose forward end is connected in parallel to the front end of the first variable inductor and whose rear end is connected to the ground (GND); A second variable inductor having a front end connected in series to a rear end of the first variable inductor; A second variable capacitor whose forward end is connected in parallel to the front end of the second variable inductor and whose rear end is connected to the ground; A third variable inductor whose front end is connected in series to a rear end of the second variable inductor; A third variable capacitor having a front end connected in parallel to the front end of the third variable inductor and a rear end connected to the ground; A fourth variable inductor whose front end is connected in series to the rear end of the third variable inductor; A fourth variable capacitor having a front end connected to the front end of the fourth variable inductor in parallel and a rear end connected to the ground; A fifth variable inductor having a front end connected in series to the rear end of the fourth variable inductor and a second end connected in parallel to the rear end; And a fifth variable capacitor having a front end connected to the front end of the fifth variable inductor in parallel and a rear end connected to the ground; .

The Gaussian filter array using the variable element according to an embodiment of the present invention includes: a first inductor having a front end connected in series to a rear end of a first through hole for impedance matching; A first capacitor having a front end connected to the front end of the first inductor in parallel and a rear end connected to the ground GND; A second inductor whose front end is connected in series to a rear end of the first inductor; A second capacitor having a front end connected to the front end of the second inductor in parallel and a rear end connected to the ground; A third inductor having a front end connected in series to a rear end of the second inductor; A first variable capacitor having a front end connected to the front end of the third inductor in parallel and a rear end connected to the ground; A fourth inductor having a front end connected in series to a rear end of the third inductor; A second variable capacitor whose forward end is connected in parallel to the front end of the fourth inductor and whose rear end is connected to the ground; A first variable inductor having a forward end connected in series to a rear end of the fourth inductor and a second forward connected in parallel at a rear end; A third variable capacitor having a front end connected in parallel to the front end of the first variable inductor and a rear end connected to the ground; .

In another aspect of the present invention, there is provided a method of tuning a Gaussian filter array using a variable element, comprising the steps of: A) filtering an input signal; B) determining whether or not ringing noise is included in the signal filtered in step A); C) Fourier transforming the filtered signal if ringing noise is included in step B); D) comparing the Fourier transformed signal with an ideal curve in step C); And E) tuning the Fourier transformed signal in step C) to an ideal curve of step D) by varying the value of the variable element; .

Also, according to another embodiment of the present invention, the tuning in the step E) adjusts the value of the variable inductor or the variable capacitor.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to that, terms and words used in the present specification and claims should not be construed in a conventional and dictionary sense, and the inventor may properly define the concept of the term in order to best explain its invention It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.

According to various embodiments of the present invention, the Gaussian filter array using a variable element has an effect of effectively removing ringing noise without an external voltage by configuring the filter array using passive elements only.

In addition, according to various embodiments of the present invention, the Gaussian filter array using the variable element attenuates the ringing noise by varying the value of the variable inductor and the variable capacitor, thereby easily obtaining a signal close to the ideal output.

1 is a circuit diagram showing a Gaussian filter array using a variable element according to an embodiment of the present invention;
2 is a circuit diagram showing an equivalent circuit of a 10th-order Gaussian low-pass filter array having a gain of -60 dB at 25 MHz band according to an embodiment of the present invention;
FIG. 3 is a graph showing frequency domain response characteristics of the Gaussian low-pass filter array shown in FIG. 2. FIG.
FIG. 4 is a diagram illustrating a pulse signal having a full width at half maximum (FWHM) of half a full width at half maximum according to an embodiment of the present invention. The pulse signal is input to a tenth order Gaussian low-pass filter array, A graph showing output signals.
FIG. 5 is a graph showing the comparison between the ideal Gaussian output and the actual Gaussian output before tuning.
FIG. 6 is a graph showing a result of tuning an output of an actual Gaussian low-pass filter array before tuning and adjusting it to an ideal output according to an embodiment of the present invention. FIG.
FIG. 7 is a circuit diagram showing a circuit having some elements provided at output terminals of a 10th-order Gaussian low-pass filter array as variable elements according to an embodiment of the present invention; FIG.
8 is a flowchart showing a tuning method of a Gaussian filter array using a variable element according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The objectives, specific advantages and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. It should be noted that, in the present specification, the reference numerals are added to the constituent elements of the drawings, and the same constituent elements have the same numerical numbers as much as possible even if they are displayed on different drawings. Also, the terms " first ", " second ", and the like are used to distinguish one element from another element, and the element is not limited thereto.

Also, the singular forms as used below include plural forms unless the phrases expressly have the opposite meaning. Throughout the specification, when an element is referred to as "including" an element, it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

1 to 8 are denoted by the same reference numerals.

The basic principle of the present invention is that a passive element of a Gaussian filter array is provided as a variable element so that the value of the element can be easily changed when ringing noise is generated to attenuate the ringing noise.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

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

1 is a circuit diagram showing a Gaussian filter array using a variable element according to an embodiment of the present invention.

Referring to FIG. 1, a Gaussian low-pass filter array according to an embodiment of the present invention is composed of a tenth order filter array and includes a first LC filter 110 to a fifth LC filter 150.

The 10th-order Gaussian low-pass filter array 100 constructed as shown in FIG. 1 will be described in detail below.

First, an input signal Vin generated by a source S is converted into a first input signal Vin1 via a first through-hole R1 of 50 ohms for impedance matching. It is preferable that the first through R1 is a resistor for impedance matching. The converted first input signal Vin1 is input to the previous stage of the first LC filter 110 and filtered and then output to the subsequent stage of the first LC filter 110. [

That is, the first input signal Vin1 is filtered by the first variable inductor 111 and the first variable capacitor 112. Here, the front end of the first variable capacitor 112 is connected to the front end of the first variable inductor 111, and the rear end is connected to the ground (GND). Therefore, the high frequency component (noise) of the target frequency band or more contained in the first input signal Vin1 flows to the ground GND by the first variable capacitor 112. [ The high frequency components of the target frequency band or more contained in the first input signal Vin1 filtered by the first variable capacitor 112 are attenuated and filtered by the first variable inductor 111 and the component of the target frequency band is filtered by the first variable inductor 111. [ (111).

The front end of the first variable capacitor 112 may be connected to the rear end of the first variable inductor 111.

Here, the first LC filter 110 according to the embodiment of the present invention is a low pass filter (LPF), and serves to pass a signal component in a lower frequency band than the target frequency band. To this end, the first LC filter 110 can attenuate the high frequency components in the frequency band region higher than the target frequency band because the impedance of the inductor increases at the signal of the band higher than the target frequency and at the same time the impedance of the capacitor decreases.

The second input signal Vin2 output from the subsequent stage of the first LC filter 110 is input to the second LC filter 120 as described above. Here, the second input signal Vin2 is the output signal of the first LC filter 110, but is the input signal of the second LC filter 120, and therefore, it is described as the second input signal Vin2 for convenience of explanation.

The second LC filter 120 includes a second variable inductor 121 and a second variable inductor 121. The second variable inductor 121 has a front end connected to the rear end of the first variable inductor 111 and a rear end connected to the front end of the second variable inductor 121, And a second variable capacitor 122 connected to the ground GND. Likewise, the front end of the second variable capacitor 122 may be connected to the rear end of the second variable inductor 121.

The second LC filter 120 configured as described above performs the same operation as the first LC filter 110.

In other words, the second LC filter 120 receives the second input signal Vin2 at the previous stage of the second variable inductor 121. The input second input signal Vin2 is firstly filtered by the second variable capacitor 122 connected to the front end of the second variable inductor 121 and secondarily filtered by the second variable inductor 121. Accordingly, the second LC filter 120 can filter the second input signal Vin2 and output the third input signal Vin3.

Similar to the filtering method of the first LC filter 110 and the second LC filter 120 described above, the third LC filter 130 filters the third input signal Vin3 to generate the fourth input signal Vin4 And the fourth LC filter 140 filters the fourth input signal Vin4 and outputs the fifth input signal Vin5. Finally, the fifth LC filter 150 filters the fifth input signal Vin5 and outputs the final output signal Vout.

The first to fifth variable inductors 111, 121, 131, 141, and 151 and the first to fifth variable capacitors 112, 122, 132, and 132, respectively, 142, and 152, respectively, to attenuate the ringing noise.

In the embodiment of the present invention, a 10th-order Gaussian low-pass filter array including the first LC filter 110 to the 5 < th > LC filter 150 is assumed. However, since this is only an example, the order of the Gaussian low- . Similarly, although the low-pass filter array is assumed in the embodiment of the present invention, it is applicable to various passive filters such as a band-pass filter, a band-pass filter, a high-pass filter, and a low-pass filter. In the embodiment of the present invention, it is assumed that the inductor and the capacitor are used as variable elements, but it is also possible to use a variable element such as a resistance or the like.

An experimental example of a Gaussian low-pass filter array 200 according to an embodiment of the present invention will be described below.

[Experimental Example]

2 is a circuit diagram showing an equivalent circuit of a 10th-order Gaussian low-pass filter array having a gain of -60 dB at 25 MHz according to an embodiment of the present invention. FIG. 3 is a circuit diagram showing an equivalent circuit of the Gaussian low- 4 is a graph showing a pulse signal having a full width at half maximum (FWHM) of half a full width (FWHM) according to an embodiment of the present invention, FIG. 5 is a graph showing the comparison between the ideal Gaussian output and the actual Gaussian output before tuning, and FIG. 6 is a graph showing the comparison between the ideal Gaussian output and the actual Gaussian output before tuning. As a result of tuning the output of the actual Gaussian low-pass filter array output before tuning according to an embodiment of the present invention to an ideal output FIG. 7 is a circuit diagram showing a circuit including some elements provided at output terminals of a 10th-order Gaussian low-pass filter array as variable elements according to an embodiment of the present invention.

Referring to FIG. 2, a Gaussian low-pass filter array 200 having a gain of -60 dB at 25 MHz is designed as ADS 2008 (advanced design system 2008, Agilent). The 10th-order Gaussian low-pass filter array 200 shown in FIG. 2 includes a plurality of variable inductors L1 to L5 connected in series and variable capacitors L1 to L5 connected in parallel to the front ends of the variable inductors L1 to L5, (C1 to C5).

Referring to the graph of FIG. 3, the frequency response characteristic of the 10th-order Gaussian low-pass filter array 200 constructed as shown in FIG. 2 has a gain of -60 dB at 25 MHz. Here, the frequency response characteristic curve shown in Fig. 3 assumes an ideal case curve.

Based on the results shown in FIGS. 2 and 3, the 10th order Gaussian low-pass filter array 200 was actually fabricated on a printed circuit board (PCB) using an LC kit.

Therefore, a pulse signal generated by a function generator (not shown) is input to the 10th-order Gaussian low-pass filter array 200 actually manufactured.

Referring to FIG. 4, it can be seen that ringing noise is generated in the right side area S of the output graph x axis of the 10th-order Gaussian low-pass filter array 200 actually manufactured. Here, the x-axis of the graph shown in Fig. 4 is time and the y-axis is voltage.

4 is a graph generated by plotting output data of an oscilloscope (not shown) with a matlab. In the graph, a pulse signal having a half-width of 20 ns generated by a function generator is input to a 10th-order Gaussian low-pass filter array 200 actually produced, and the filtered output value is displayed as an oscilloscope.

Referring to FIG. 4, the 10th-order Gaussian low-pass filter array 200 actually produced can generate ringing noise in the right-side region S of the x-axis, unlike the ideal output.

The reason why the above-mentioned ringing noise is generated is that a parasitic oscillation occurs due to the presence of inductance and capacitance other than the design in the circuit, and signals of the oscillation frequency of the oscillation are mixed out. In the case of inductance that can be classified as a noise component, the current flowing through all the conductors forms a magnetic field around the ampere principle. The magnetic field thus created creates an inductive current in the surrounding conductor, which creates unwanted inductance. And the lead used to actually make the circuit can also work as a capacitor.

For the above reason, it can be expected that the 10th-order Gaussian low-pass filter array 200 actually produced is distorted in the transfer function. Therefore, as shown in FIG. 5, the frequency response is confirmed by performing Fourier transform on the frequency domain using the output data of FIG.

Referring to FIG. 5, B is a graph showing a simulation result of an ideal 10th-order Gaussian low-pass filter array, and C is a graph showing an output of a 10th order Gaussian low-pass filter array 200 actually manufactured.

Referring to FIG. 5, it can be seen that the output C of the 10th-order Gaussian low-pass filter array 200 actually produced is distorted more than the output B of the ideal 10th order Gaussian low-pass filter array.

When the x-axis right side region (S, distortion region) in which the actual ringing noise shown in Fig. 4 is generated is Fourier transformed, the signal distortion is converted to a form in which signal distortion occurs at about 10 MHz as shown in the graph of Fig. It can be inferred that the substantial cause of the ringing noise shown in FIG. 5 is that the additional noise signal passes much more than an ideal Gaussian signal at around 10 MHz. That is, in the vicinity of the 10 MHz band, not only the Gaussian signal but also the noise near 10 MHz are mixed and the ringing noise is generated. Therefore, it can be seen that the transfer function is distorted near the 10 MHz band.

In order to compensate for the distortion caused by the above-mentioned reason, the inductors L1 to L5 and the capacitors C1 to C5 of the 10th-order Gaussian low-pass filter array 200, which are actually manufactured, are variable and tuned.

FIG. 6 shows the output of the 10th-order Gaussian low-pass filter array 200 actually tuned by varying the inductance and capacitance values of the graph distortion caused by the ringing noise in FIG. 5, similar to the ideal simulation output. In FIG. 6, C 'is a graph tuned to the output of the 10th-order Gaussian low-pass filter array 200 actually manufactured.

By designing the inductor and capacitor of the 10th-order Gaussian low-pass filter array 200 in a variable shape, it is possible to easily change the inductance value and the capacitance value while monitoring using a monitoring device such as an oscilloscope, thereby making the ringing noise similar to the ideal output Can be attenuated.

[Table 1] is a table summarizing the inductor and capacitor values required in each frequency band in the circuit diagram of the tenth order Gaussian low-pass filter array 300 shown in FIG. 7, The table summarizes the relative values of the summarized values.

Referring to [Table 2] and FIG. 7, L1 to L4, C1, and C2 are elements whose relative values differ by more than two times based on the maximum values L5 and C5. Therefore, it can be seen that the device provided at the output end has more influence on the output characteristic than the device provided at the input end. Therefore, by tuning the elements provided at the output terminal by varying, the ringing noise can be attenuated more effectively. In this way, it is possible to design a more efficient ringingless low-pass filter by designing L5 and C3 to C5, which have a relatively large influence, as variable elements.

On the other hand, although the difference between the relative values is less than 2 times, it is neglected. However, it is preferable that the device value can be adjusted even in the case of the device which is less than 2 times according to the experimental purpose.

8 is a flowchart illustrating a tuning method of a Gauss filter array using a variable element according to another embodiment of the present invention.

Referring to FIG. 8, a tuning method (S400) of a Gaussian filter array using a variable element according to another embodiment of the present invention includes filtering (S410) an input signal, determining whether the filtered signal includes ringing noise S420), comparing the filtered signal with an ideal curve (S422), and comparing the filtered signal with an ideal curve (S422), and comparing the Fourier transformed signal to an ideal curve And tuning (S430).

In the description of FIG. 8, the description overlapping with FIGS. 1 to 7 will be omitted.

Referring to FIG. 8, the input signal of the 10th-order Gaussian low-pass filter array 200 is filtered (S410). In operation S420, it is determined whether the filtered signal includes ringing noise (S420). Here, the ringing noise can be determined using a monitoring device such as an oscilloscope.

If the signal filtered in step S420 includes ringing noise, the filtered signal is subjected to Fourier Transform (S421) and is compared with an ideal output curve (S422).

The values of the variable elements affecting the region distorted by the ringing noise are varied and tuned to an ideal curve (S423) (S430).

In particular, in step S423, the variable inductor or the variable capacitor is tuned by varying the value, while the variable inductor and the variable capacitor provided in the output stage having a relatively large influence on the output graph are tuned.

As described above, by using the tuning method (S400) of the Gauss filter array using the variable element according to another embodiment of the present invention, by varying the element values of the variable inductor and the variable capacitor to attenuate the ringing noise, .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

100, 200, 300: 10th order Gaussian low-pass filter array
110: first LC filter 120: second LC filter
130: third LC filter 140: fourth LC filter
150: fifth LC filter 111: first variable inductor
121: second variable inductor 131: third variable inductor
141: fourth variable inductor 151: fifth variable inductor
112: first variable capacitor 122: second variable capacitor
132: third variable capacitor 142: fourth variable capacitor
152: fifth variable capacitor

Claims (7)

In the filter array,
A plurality of variable inductors connected in series; And
And a plurality of variable capacitors connected in parallel to each of the variable inductors,
And a plurality of variable inductors are connected to the front end and the rear end of the plurality of variable inductors through a resistance formed of resistors for impedance matching.
A Gaussian filter array using variable elements.
The method according to claim 1,
The variable inductor
A signal is applied to the front end, a signal is output to the rear end,
The variable capacitor
Wherein a front end is connected in parallel to the front end of the variable inductor and a rear end is connected to the ground
A Gaussian filter array using variable elements.
The method according to claim 1,
The variable capacitor
And the variable inductor is connected in parallel to either one of a front end and a rear end of the variable inductor
A Gaussian filter array using variable elements.
The method according to claim 1,
The Gaussian filter array using the variable element
A first variable inductor connected in series to a rear end of a first through for impedance matching;
A first variable capacitor whose forward end is connected in parallel to the front end of the first variable inductor and whose rear end is connected to the ground (GND);
A second variable inductor having a front end connected in series to a rear end of the first variable inductor;
A second variable capacitor whose forward end is connected in parallel to the front end of the second variable inductor and whose rear end is connected to the ground;
A third variable inductor whose front end is connected in series to the rear end of the second variable inductor;
A third variable capacitor having a front end connected in parallel to the front end of the third variable inductor and a rear end connected to the ground;
A fourth variable inductor whose front end is connected in series to the rear end of the third variable inductor;
A fourth variable capacitor having a front end connected to the front end of the fourth variable inductor in parallel and a rear end connected to the ground;
A fifth variable inductor having a front end connected in series to the rear end of the fourth variable inductor and a second end connected in parallel to the rear end; And
A fifth variable capacitor having a front end connected to the front end of the fifth variable inductor in parallel and a rear end connected to the ground; Containing
A Gaussian filter array using variable elements.
The method according to claim 1,
The Gaussian filter array using the variable element
A first inductor having a front end connected in series to a rear end of a first through for impedance matching;
A first capacitor having a front end connected to the front end of the first inductor in parallel and a rear end connected to the ground GND;
A second inductor whose front end is connected in series to a rear end of the first inductor;
A second capacitor having a front end connected to the front end of the second inductor in parallel and a rear end connected to the ground;
A third inductor whose front end is connected in series to a rear end of the second inductor;
A first variable capacitor having a front end connected to the front end of the third inductor in parallel and a rear end connected to the ground;
A fourth inductor having a front end connected in series to a rear end of the third inductor;
A second variable capacitor whose forward end is connected in parallel to the front end of the fourth inductor and whose rear end is connected to the ground;
A first variable inductor having a front end connected in series to a rear end of the fourth inductor and a second end connected in parallel at a rear end; And
A third variable capacitor having a front end connected to the front end of the first variable inductor in parallel and a rear end connected to the ground; Containing
A Gaussian filter array using variable elements.
The method according to claim 1,
The input signal input to the filter array is filtered to adjust the value of the variable inductor or the variable capacitor according to a signal obtained by Fourier transforming the filtered signal to tune to an ideal curve Characterized by
A Gaussian filter array using variable elements.


delete

Images