KR0138103Y1 - Audio detection circuit of different broadcasting mode - Google Patents

Abstract

The present invention relates to an audio detection circuit for each broadcasting method for detecting various audio signals for each broadcasting method in a multi-system receiver.

This eliminates the inconvenience of selecting the FM audio signal for each broadcasting system in the existing multi-system.

To this end, the present invention includes a square wave converting means for amplifying and converting an FM audio signal into a square wave, and includes a counting means for one square wave at all times, and includes comparing means for comparing the value counted by the counting means with a reference value. And a mean value extracting means for extracting the comparison output of the mean value to determine the broadcasting method.

Description

Audio Detection Circuit for Each Broadcasting Method

1 is a circuit diagram of the present invention.

2 is a waveform diagram of the present invention.

* Explanation of symbols for main parts of the drawings

100: square wave converter 110: preamplifier

120: amplifier 200: count unit

210: flip-flop 220: counter

230: buffer 300: comparison unit

310-340: comparator 400: average value extraction unit

410-450: Counter 460: Comparator

The present invention relates to an audio detection circuit for each broadcasting method that detects various audio signals for each broadcasting method in a multi-system receiver, and detects and demodulates an audio signal regardless of the broadcasting method.

According to the broadcasting method, the FM carrier frequency is different and accordingly the duty (duty) of the FM audio signal is different. However, a multi-system capable of receiving various broadcasting methods as one set has been developed.

Therefore, the multi-system can receive the desired broadcast method only by selecting the audio signal for each broadcast method, and conventionally, the broadcast method of the FM audio signal is manually selected from the outside or only the PAL or SECAM method is automatically selected.

The method of manually selecting the broadcasting method of the FM audio signal is inconvenient to switch the switching switch to the selected broadcasting method every time according to the change of the broadcasting method.

The method of automatically switching to PAL or SECAM method is a well-known technique. The frequency component of the SECAM color is detected by a band pass filter, then envelope-detected and integrated. If the DC component is large, the SECAM method is determined. If the technology is determined by the PAL method.

This PAL / SECAM discrimination method is a well-known technique, but it is only possible to discriminate between PAL or SECAM methods, and other broadcast methods cannot be discriminated. Only PAL / SECAM switching can be automatically selected, and other manual selections must be made. You will be inconvenienced.

The present invention has a square wave converting means for amplifying and converting an FM audio signal into a square wave by detecting all broadcasting schemes and automatically switching them, and having a counting means for counting one cycle of the square wave, and counting the values in the counting means. It is provided with a comparison means for comparing with a reference value and the average value extraction means for determining the broadcast method by extracting the comparison output of the standing comparison means as an average value.

That is, the present invention for measuring the period of the FM audio signal to automatically detect the broadcast method will be described in detail based on the accompanying drawings.

1 is a circuit diagram of the present invention.

The present invention is a square wave conversion unit 100 for converting an FM audio signal into a square wave,

A counting unit 200 for counting one period of the square wave at a specific frequency;

A comparison unit 300 for comparing the count value of the count unit 200 with a predetermined reference value,

An average value extracting unit 400 extracts a comparison output of the comparing unit 300 as an average value and outputs a determination signal for a broadcasting method.

The square wave converter 100 includes a preamplifier 110 and an amplifier 120, and extracts only an FM audio signal extracted from the preamplifier 110 from the 4 to 7 MHz band, and the amplifier 120 is a preamplifier 110. Amplified FM audio signal is greatly amplified and outputs a saturated square wave.

The counting unit 200 includes a flip-flop 210, a counter 220, and a buffer 230, and the flip-flop 210 receives one pulse per cycle of the square wave pulse applied from the square wave converter 110. The counter 220 is reset and the counter 220 is reset by the pulse of the flip-flop 210. One cycle of the square pulse is counted at a specific frequency (100 MHz), and the buffer 230 is a square wave converter ( It is enabled by the output of 100 and delivers the output of the counter 220.

The comparator 300 is composed of comparators 310-340 and compares the output of the counter 200 with a predetermined value and is reset by the output of the square wave converter 100.

In this case, the predetermined values of the comparators 310 to 340 are set according to a specific frequency applied to the counter 220.

Average value extraction unit 400 is composed of a comparator 460 of the counter (410-450) and the counter (420-450) counts the output of the comparator (310-340) and applies a count value to the comparator (460) The comparator 460 outputs a broadcast method selection signal having a maximum value among the outputs of the counters 420-450, and the counter 410 resets the counters 420-450 by counting the output of the square wave converter 100. In addition, a clock signal is applied to the comparator 460.

The present invention of such a configuration is intended to output a broadcast method selection signal by counting one cycle of the FM audio signal because the duty of the FM audio signal is different for each broadcast method.

In other words, NTSC has 4.5MHZ for FM carrier frequency, 5.5MHZ for PAL B / G, 6.0MHZ for PAL I and 6.0MHZ for PAL G / K. It will not escape.

Therefore, since the period of the FM audio signal is measured, it is possible to know what broadcasting method the inputted FM audio signal is.

For example, the period of the NTSC FM audio signal is (1 / 4.5M) + SEC, where △ is very small and is ignored.

NTSC system has a period of (1 / 4.5M) SEC, PAL B / G system has (1 / 5.5M) SEC, PAL I system has (116.0M) SEC, and PAL G / K system has (1 / 6.5M) It becomes SEC.

As described above, the method of measuring different periods for each broadcasting method has a small number of input FM signals and is likely to be mixed with several frequencies. Therefore, only the 4MHZ-7MHZ frequency band is extracted through the preamplifier 110 and then amplified by the amplifier 120. Create a saturized square wave.

That is, the square wave converter 100 converts the FM audio signal into square waves as shown in FIG. 2A. The square wave converted by the square wave converter 100 is applied to the count unit 200 while the inverter 301 Inverted in the ()) is applied to the comparator 300 and the average value extraction unit 400.

The counting unit 200 is short such that the flip-flop 210 generates a pulse as shown in FIG. 2B by inputting a square wave pulse as shown in FIG. 2A and applies it to the reset input of the counter 220. .

The output pulse width of the flip-flop 210 is determined by the number of the gate elements 201 and 202.

The counter 220 is reset by the pulse of the flip-flop 210 and counts a specific frequency (100 MHz).

That is, the counter 220 counts one cycle of the FM audio signal as 100 MHz, and accordingly, 100 / 4.5 = 22.2 is counted in the NTSC method, 100 / 5.5 = 18.1 is counted in the PAL B / G method, and the PAL I method is counted. In the case of 100 / 6.0 = 16.6, 100 / 6.5 = 15.4 is counted in the PAL G / K method.

The value counted by the counter 220 is applied to the comparator 300 through the buffer 230 which is enabled by the square and the pulse of the square wave converter 100.

Comparator 300 is composed of four comparators (310-340), each comparator (310-340) counts a predetermined value, the comparator 310 when the count unit 200 has more than 20 count pulses One pulse is output and the comparator 320 outputs a pulse when there are 17-20, and the comparator 330 outputs a pulse when 16-17 and the comparator 340 are 16 or less.

Here, the comparison values of the comparators 310 to 340 are determined by the specific frequency 100MHZ applied to the counter 220.

Therefore, when the high level pulse is output from the comparator 310, the NTSC method, the PAL B / G method when the high level pulse is output from the comparator 320, and the PAL I method, the comparator 340 when the high level pulse is output from the comparator 330 ), High level pulse output means PAL G / K type.

For example, when the value counted by the counter 220 is 21, 22, 20, and 21 as shown in FIG. 2C, the output of the comparator 310 is output as shown in FIG. ) Is output as shown in (F) of FIG. 2 and the outputs of the comparators 330 and 340 are low level as shown in (G) of FIG.

At this time, the part indicated by the dotted line in (E) of FIG. 2 becomes an error (compared to the PAL B / G method despite the NTSC method).

In order to prevent such an error, the outputs of the comparators 310-340 are applied to the counters 420-450 so that the counters 420-450 count the output pulses of the comparators 310-340.

Then, a center for counting the largest value among the counters 420-450 is generated, and the comparator 460 outputs a broadcast mode selection signal according to the value of the counters 420-450 representing the largest value.

That is, as shown in the example, when the output pulses of the comparator 310 are the most, the count value of the counter 420 is the largest, and the comparator 460 recognizes this and outputs an NTSC broadcast selection signal at a high level. Allow automatic selection.

If the output of the counter 430 is the highest, the comparator 460 outputs the PAL B / G broadcast selection signal to a high level to automatically select the PAL B / G broadcast.

Therefore, even if an error occurs as shown in (E) of FIG. 2, the correct broadcast method can be selected.

On the other hand, the square wave pulse as shown in (D) of FIG. 2 inverted by the inverter 301 is applied as a clock signal of the counter 410, and the counter 420 outputs a pulse as shown in (H) of FIG. 2 in the counter 410. At the same time as the reset signal of -450 and at the same time as the clock signal of the comparator 460 to repeat the above-described operation every predetermined period.

Therefore, when the output of the comparator 460 is applied to a multi-audio processor integrated device that demodulates an FM audio signal regardless of a broadcasting method, the output of the comparator 460 may be automatically selected without the inconvenience of selecting the audio signal according to the broadcasting method.

As described above, the present invention is used in a multi-system broadcast receiver by automatically selecting and demodulating the FM audio signal regardless of the broadcast method.

Claims (5)

In a multi-system broadcast receiver, a square wave converter 100 for converting an FM audio signal into a square wave, a count unit 200 for counting one cycle of the square wave at a specific frequency, and a count value of the count unit 200. Is detected by a comparison unit 300 for comparing the reference value with a predetermined reference value, and an average value extraction unit 400 for outputting a broadcast method determination signal by extracting the comparison output of the comparison unit 300 as an average value. Circuit. The square wave converter 100 of claim 1, wherein the square wave converter 100 extracts and amplifies only a specific band of an FM audio signal, and a square wave is amplified by greatly amplifying the FM audio signal extracted from the preamplifier 110. An audio detection circuit for each broadcasting system, characterized in that the amplifier 120 for outputting a pulse. The flip-flop 210 and the reset of the flip-flop 210 according to claim 1, wherein the counting unit 200 receives a square wave pulse of the square wave converting unit 100 and outputs one reset pulse per cycle. A counter 220 reset by a pulse and counting a specific frequency, and a buffer 230 for outputting the output of the counter 220 to a square wave pulse of the square wave converter 100. Audio detection circuit for each broadcast system. The apparatus of claim 1, wherein the comparator 300 includes comparators 310-340 for outputting a comparison pulse by comparing the counter 200 with a predetermined value, and the comparators 310-340 are square wave transforms. The audio detection circuit for each broadcasting method, which is reset by the square wave pulse of the unit (100). The method of claim 1, wherein the average value extracting unit 400 compares the pulses of the comparators 310-340 with the counters 420-450 and the counters of the counters 420-450 to have a maximum value. A counter for resetting the counters 420-450 by using the comparator 460 for outputting the selected broadcast method selection signal and the square wave pulse of the square wave converter 100 as a clock input, and applying a clock signal to the comparator 460 ( Audio detection circuit for each broadcasting method, characterized in that consisting of 410.