KR810001207Y1 - Transducer of automatic sound intermediate frequency - Google Patents

Abstract

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Description

Automatic voice intermediate frequency converter

1 is a circuit diagram of the present invention.

The present invention relates to a voice intermediate frequency converter used in a TV receiver, and in particular, to listen to broadcasts of two kinds of broadcasting systems having different TV voice second intermediate frequencies without using a switch or other complicated conversion device in the TV receiver. It relates to a converter circuit.

Southeast Asian empires, etc., broadcast TV in two ways in one country. In other words, the TV stations of the system M system and system B system specified by the CCIR (International Radio Communication Advisory Committee) are installed together. Accordingly, when broadcasting in two ways, there is a problem to listen to the broadcast with one TV receiver. When watching a system B type broadcast with a TV receiver produced by the system M type, the screen is displayed but no audio is heard.

The present invention has been devised in view of the above advantages, and is due to the difference in the broadcasting method, and the second intermediate frequency (for example, 6 MHz or 6.5 MHz, 5.5 MHz and 6.0 MHz, 5.5 MHz and 6.5 MHz, 4.5 MHz and 5.5) MHz, 4.5MHz and 6MHz, 4.5MHz and 6.5MHz, etc.), a circuit consisting of an oscillation circuit and a transformer having a different resonance frequency between the conventional voice intermediate frequency transformer and the FM demodulation circuit is constructed, By changing the channel, you can listen to the desired broadcast.

Referring to the circuit of the automatic TV voice intermediate frequency converter according to the present invention in detail as follows.

1 is a frequency automatic conversion circuit according to the present invention, which includes a transistor Q1, a transformer T2, a capacitor C4, and a resistor R3 between an intermediate frequency transformer T1 and an FM demodulation circuit (not shown). The oscillating circuit of the back is connected to the secondary side of the intermediate frequency transformer T1, one terminal of the transformer T2 is connected to the primary side of the transformer T3 through the resistor R4, and The secondary side is connected to the FM demodulation circuit. In addition, a capacitor C6 was configured between the input terminal and the primary side of the transformer T3.

The capacitors C1 and C6 in the circuit are DC blocking coupled capacitors, and the capacitor C3 is for bypass. The capacitors C2, transformer T1 and capacitors C7 and transformer T3 are parallel resonant circuits. For example, at 5.5 MHz, the transformer T3 is resonated at 4.5 MHz, respectively. In addition, the transformer T2 is an oscillating transformer to oscillate precisely at 1 MHz, and the capacitor C4 is an oscillating capacitor. Resistors R1, R2, and R3 are resistors for bias, respectively. The FM demodulation circuit (not shown) after the parallel resonant circuit consisting of the capacitor C7 and the transformer T3 is adjusted to demodulate the frequency modulated component centered on the 4.5 MHz into the audio signal.

Now, for example, if a channel is tuned to a broadcasting station of system M of CCIR, in this case, a frequency component modulated around 4.5 MHz is obtained as a second intermediate frequency of speech in a circuit in which video and audio are separated. In the intermediate frequency transformer T1 resonated at MHz, no signal component is mixed at all, and it is induced on the primary side of the transformer T3 resonated at 4.5 MHz through the capacitor C6 and appears at the secondary side. The demodulator is then demodulated in the FM demodulation circuit after T3 and converted into an audible signal.

On the other hand, if the channel is finished to the broadcasting station of system B, a signal component whose frequency is modulated about 5.5 MHz is obtained similarly to the case of system M. Therefore, the transformer T3 resonates at 4.5 MHz via the capacitor C6. It is not mixed at all, and is introduced to the left side of the intermediate frequency transformer T1 resonated at 5.5 MHz through the capacitor C1.

Therefore, if the oscillation circuits of transistors Q1 and T2 operating in class C oscillate at exactly 1 MHz, the Fourier (Fourier) is added between the 5.5 MHz signal component on the secondary side of the transformer T1 and the oscillated frequency 1 MHz. ) Numerous frequencies can occur and appear on the primary side of transformer T3 through resistor R4, but since transformer T3 is resonant at 4.5 MHz, the frequency difference between the two frequencies (5.5 MHz-1 MHz) Since only the signal component coincides with the resonance frequency of the transformer T3, the signal appearing on the secondary side of the transformer T3 has only a component of 4.5 MHz. Therefore, when the signal component is added to the 4.5 MHz FM demodulation circuit converting to an audible frequency, the signal is converted into an audio signal.

The circuit is not only 4.5MHz and 5.5MHz, but also changes according to the resonant frequency of T1 and T3 and the oscillation frequency of T2 as described above, and listens to all other TV broadcasting methods such as 6MHz, 6.5MHz, 4.5MHz and 6MHz. You can do Of course, this circuit is limited to the audio portion, so when watching systems B and M where the number of horizontal and vertical lines of the TV is different, it is necessary to adjust the video portion of the TV separately.

As such, the present invention automatically selects the second intermediate frequency of the broadcasting frequencies by two different broadcasting systems so that only the channels are exchanged without the use of other special devices, thereby automatically selecting and listening to the voice according to each broadcasting system. It's a very practical automatic voice intermediate frequency converter that doesn't have to have each set.

Claims (1)

Between the conventional intermediate frequency transformer T1 and the FM demodulation circuit, a common oscillation circuit composed of a transistor Q1, a transformer T2, a capacitor C4, a resistor R3, or the like is used as an intermediate frequency transformer T1. The other end of the transformer T2 is connected to the primary side of the transformer T3 through a resistor R4 such that the difference frequency between the resonant frequency and the oscillation frequency of the intermediate frequency transformer is resonated. An automatic voice intermediate frequency converter for selectively listening to two voice frequencies by means of a differently resonant transformer by connecting a capacitor (C6) between the primary side of the transformer (T3) and the input of the intermediate frequency transformer.