KR0174915B1 - Apparatus for controlling band width of a low pass filter - Google Patents

Abstract

The present invention provides a low-pass filtering control device for removing high-frequency components that act as noise contained in an audio signal so that an audio signal having an improved signal-to-noise ratio can always be output regardless of a playback mode. In accordance with one aspect of the present invention, a device according to the present invention receives a signal reproduced at an early stage of reproduction from a tech unit, grasps the current reproduction mode, and controls the microcomputer 40 to control low pass filtering suitable for the current reproduction mode. The first low pass filter 20 performs low pass filtering to remove the high frequency components acting on the audio signal reproduced in the reproducing mode, and is turned on by the microcomputer 40 only in the LP mode. Low-pass filtering is performed to remove high frequency components that are noisy in the audio signal reproduced with the pass filter. Low pass filtering so as to remove the high frequency components acting on the second low pass filter 60 and the audio signal reproduced together with the first low pass filter, which is turned on by the microcomputer 40 only in the EP mode. It consists of a third low pass filter (70). Therefore, it is possible to provide a VC to reproduce an audio signal having a good signal-to-noise ratio at all times regardless of the playback mode.

Description

Low Pass Filtering Control

1 is a relationship diagram between a conventional low pass filter and an audio signal processor.

2 is a block diagram of a V. C. egg equipped with a low pass filtering control device according to the present invention.

* Explanation of symbols for main parts of the drawings

10: audio signal processor 20, 60, 70: low pass filter

30: key input unit 40: micom

50: Tech Department

The present invention relates to a low pass filter for audio signals reproduced in V. C. eggs, and more particularly, by converting the pass band of the low pass filter according to the reproduction mode of V.C. The present invention relates to a low pass filtering control device capable of removing noise components.

In general, V. C. regeneration modes include SP (standard-play) mode, LP (long-play) mode, and EP (extended-play) mode. In the SP mode, the playback time is 2 hours, and the advancing speed of the cassette tape is 33.5 mm / s. In the LP mode, the playback time is 4 hours, and the moving speed of the cassette tape is 16.67 mm / s. In the EP mode, the playback time is 6 hours and the advancing speed of the tape is 11.12 mm / s.

However, when reproducing programs recorded in these three playback modes, the frequency bands of audio signals that can be reproduced are different because the tapes have different advancing speeds. That is, the general audible frequency band is 20Hz to 20KHz, whereas the general V.C system guarantees the frequency characteristics only at about 10KHz in SP mode, about 7KHz in LP mode, and about 5KHz in EP mode. Therefore, all audio signals having a frequency higher than the frequency set in the corresponding mode act as noise. For example, when operating in SP mode, audio signals higher than about 10KHz act as noise. In order to remove such noise, the signal-to-noise ratio has been improved by conventionally removing high frequency components using a low pass filter.

FIG. 1 is a diagram illustrating a relationship between a conventional low pass filter and an audio signal processing unit provided in V.C.R to improve the signal-to-noise ratio of an audio signal as described above. The audio signal output from the audio signal processing unit 10 The DC component is removed through the capacitor C1, which is a DC coupling capacitor, and transmitted to the low pass filter 20. The low pass filter 20 is composed of a resistor R1 and a capacitor C2 and outputs an audio signal from which high frequency components are removed from the audio signal transmitted through the capacitor C1. In this manner, in the conventional V.C.R, the noise component included in the audio signal output from the audio signal processor 10 is removed.

However, the conventional low pass filter provided in the V.C.R is configured to be suitable for the SP mode environment, and thus there is a problem in that a high quality audio signal cannot be output when the recorded program is played in the LP and EP modes. That is, in the conventional low pass filter, the values of the resistor R1 and the capacitor C2 are determined so as to remove frequency components higher than 10 KHz. Since there is a difference, there is a problem that the components acting as noise cannot be completely removed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to remove noise components included in an audio signal by converting a pass band of a low pass filter for the audio signal according to the reproduction mode of V.C.R. Its purpose is to provide a low pass filtering control device.

In order to achieve the above object, the apparatus according to the present invention is capable of selectively playing back a recorded program by controlling a standard playback (SP) mode, a long playback (LP) mode, and an extended playback (EP) mode. In the low-pass filtering control device for removing high-frequency components acting as noise contained in the audio signal output from the audio signal processing unit for reproducing the audio signal reproduced from the tech unit during the control of the reproduction mode through the key input unit, After the playback mode is controlled through the key input section, the first playback signal is received from the deck section to determine whether the recorded program is in standard playback mode, extended playback mode or extended playback mode. Microcomputer controlling proper lowpass filtering; resistor (R1) and capacitor (C2) First low-pass filter for low-pass filtering to eliminate high frequency components of the noise acting as listed in the audio signal output from the audio signal processing modes, if one; It is composed of a transistor controlled in the ON state by the microcomputer only when the regeneration mode is a long time regeneration mode and a capacitor connected in parallel with the capacitor only when the transistor is turned on to the audio signal output from the audio signal processor together with the first low pass filter. A second low pass filter for performing low pass filtering to remove the high frequency components having the noise action; It is composed of a transistor controlled in the ON state by the microcomputer only when the regeneration mode is in the extended regeneration mode, and a capacitor connected in parallel with the capacitor only when the transistor is turned on, and is connected to the audio signal output from the audio signal processor together with the first low pass filter. And a third low pass filter for low pass filtering to remove the high frequency components acting on the noise.

Hereinafter, with reference to the accompanying drawings will be described in detail the operation of the embodiment according to the present invention.

2 is a block diagram of a V.C.R. equipped with a low pass filtering control device according to the present invention, and includes a key input unit 30, a microcomputer 40, a deck unit 50, and a playback mode for applying a user command. When the audio signal is controlled by the microcomputer 40 and the audio signal is output from the deck unit 50, only the audio signal from which the DC component is removed from the audio signal output from the audio signal processing unit 10 and the audio signal processing unit 10 for playback processing is performed. The first low pass filter 20 performing low pass filtering on the audio signal transmitted through the capacitor C1 and the capacitor C1, which is operated only in the LP mode, together with the first low pass filter 20. A second low pass filter 60 which performs low pass filtering on the transmitted audio signal, and a third low pass which operates only in the EP mode and performs low pass filtering on the audio signal transmitted together with the first low pass filter 20. It consists of a pass filter (70).

The apparatus of FIG. 2 configured as described above operates as follows.

First, when a playback command is input to the microcomputer 40 through the key input unit 30, the microcomputer 40 outputs a control signal to reproduce the cassette tape currently loaded into the deck unit 50. Accordingly, the deck unit 50 performs a play mode and outputs the reproduced audio signal to the audio signal processor 10.

The microcomputer 40 determines the mode of the current playback by receiving the playback signal which is first outputted from the deck unit 50 and outputted first. In other words, it is determined whether to reproduce in the SP mode, the LP mode, or the EP mode. In the SP mode, the microcomputer 40 provides a low signal to both the second low pass filter 60 and the third low pass filter 70. Accordingly, the transistors Q1 and Q2 of the second and third low pass filters 60 and 70 are all turned off, and the second and third low pass filters 60 and 70 are turned off and the audio is turned off. The audio signal output from the signal processor 10 is removed from the DC component through the capacitor C1 as before, and the high frequency component is transmitted through the first low pass filter 20 composed of the resistor R1 and the capacitor C2. It is removed and output.

As a result of the determination of the microcomputer 40, when the currently reproduced program is in the LP mode, the microcomputer 40 sends a high signal to the second low pass filter 60 and a low signal to the third low pass filter 70. To provide. Accordingly, the transistor Q1 is turned on so that the second low pass filter 60 is set to an on state, the transistor Q2 is turned off, and the third low pass filter 70 is turned off. Is set. As the second low pass filter 60 is set to an on state, the capacitor C2 included in the first low pass filter 20 and the capacitor C3 provided in the second low pass filter 60 are parallel to each other. A low pass filtering condition is formed to remove high frequency components acting as noise included in the audio signal reproduced in the LP mode. At this time, the value of the capacitor C3 is set to a value capable of sufficiently removing the high frequency signal of the noise component included in the audio signal reproduced in the LP mode by being coupled in parallel with the capacitor C2. Therefore, when the currently reproduced audio signal is reproduced in the LP mode, the audio signal transmitted through the capacitor C1 is passed through the low pass filter including the first low pass filter 20 and the second low pass filter 60. The low-pass filtered audio signal is output.

When the currently reproduced program is in the EP mode, the microcomputer 40 provides a low signal to the second low pass filter 60 and a high signal to the third low pass filter 70. Accordingly, the transistor Q1 is turned off, the second low pass filter 60 is set to the off state, the transistor Q2 is turned on, and the third low pass filter 70 is set to the on state. As the third low pass filter 70 is turned on, the capacitor C2 included in the first low pass filter 20 and the capacitor C4 provided in the third low pass filter 70 are paralleled. The capacitor C4 is set to have a low pass filtering condition capable of removing a high frequency component acting as a noise component in an audio signal reproduced in EP mode by connecting the capacitors C2 and C4 in parallel. .

As described above, the present invention provides a low-pass filtering control device capable of completely removing high frequency components acting as noise included in an audio signal not only in the SP mode but also in the LP mode and the EP mode. It is effective to provide VC, which reproduces a good audio signal with an improved signal-to-noise ratio, regardless of which mode the program is played in.

Claims (1)

In V.C.R, which can selectively play recorded programs by controlling the standard play (SP) mode, long play (LP) mode, and extended play (EP) mode, A low pass filtering control device for removing high frequency components acting as noise contained in an audio signal output from an audio signal processor for reproducing an audio signal to be reproduced, wherein the playback mode is controlled through the key input unit. Receiving the first signal to be reproduced from the deck unit to determine whether the playback mode of the recorded program is the standard playback mode, long time playback mode or extended playback mode to control the low-pass filtering suitable for the current playback mode Micom; A first filter including a resistor (R1) and a capacitor (C2) for low-pass filtering to remove a high frequency component that acts as a noise contained in an audio signal output from the audio signal processor when the playback mode is the standard playback mode. Low pass filter 20; Only when the regeneration mode is the long time regeneration mode, the transistor Q1 is controlled in the ON state by the microcomputer and the capacitor C3 is connected in parallel with the capacitor C2 only when the transistor Q1 is turned on. A second low pass filter (60) which performs low pass filtering to remove high frequency components acting as noise on the audio signal output from the audio signal processor together with the first low pass filter; Only when the regeneration mode is the extended regeneration mode, the transistor Q2 controlled to be turned on by the microcomputer and the capacitor C4 connected in parallel with the capacitor C2 only when the transistor Q2 is turned on are configured. And a third low pass filter 70 which performs low pass filtering to remove a high frequency component acting as a noise contained in the audio signal output from the audio signal processor together with the first low pass filter. Pass filtering control device.