KR0178317B1 - Tuner output controlling method & device - Google Patents

Abstract

Disclosed are a tuner output control method for detecting an intermediate frequency output from a mixer and adjusting a conversion gain of the mixer according to the detected intermediate frequency, and an apparatus for performing the same. Among the plurality of high frequency signals received through the antenna, only a high frequency signal of a band corresponding to a specific channel is extracted, the extracted high frequency signal is amplified, and the amplified signal is demodulated. The local oscillation frequency is mixed with the double-tuned high frequency signal through a mixer and converted into an intermediate frequency signal. If the intermediate frequency signal is detected and the intermediate frequency signal is not normal, the gain of the mixer is adjusted, and the amplification rate is adjusted by feeding back the intermediate frequency signal level output from the mixer to the AGC circuit. The intermediate frequency signal output from the mixer is detected, and the conversion gain of the mixer is adjusted according to the detected intermediate frequency signal so that the stable intermediate frequency signal is output from the mixer.

Description

Tuner output control method and apparatus for performing the same

The present invention relates to a method for controlling the output of a tuner and an apparatus for performing the same, and more particularly, to a method for controlling the output of a tuner for detecting an intermediate frequency output from a mixer and adjusting a conversion gain of the mixer according to the detected intermediate frequency. An apparatus for carrying out is provided.

In general, a tuner of a television selects a high frequency signal allocated to a broadcast channel to be received from a plurality of high frequency signals induced by an antenna of a television receiver from a broadcasting station, and makes an intermediate frequency signal (IF) easy to amplify the frequency of the selected high frequency signal. Signal; an intermediate frequency signal). That is, the tuner selects and amplifies a high frequency signal of a channel to be received from a high frequency signal transmitted from a broadcasting station, converts the local oscillation frequency into an amplified radio frequency signal and converts it into an intermediate frequency signal of 45.75 MHz.

The tuner is typically a tuning circuit for selecting a specific high frequency band among the received high frequencies, an amplifying circuit for amplifying the selected specific high frequency band, a local oscillator for generating a local oscillation frequency, and amplified by the amplifying circuit. It consists of a device such as a mixer for mixing the local oscillation frequency generated by the local oscillation device to a specific frequency and converts it into an intermediate frequency signal.

1 is a block diagram for explaining the operation of a tuner of a general television. As shown in Fig. 1, the television tuner has a tuning circuit 20 connected to an output side of an antenna 10 that receives a plurality of high frequency signals transmitted from broadcasting stations. The tuning circuit 20 selects a specific high frequency corresponding to a channel input by a user among a plurality of high frequencies input through the antenna 10. An output terminal of the tuning circuit 20 is connected to a radio frequency amplifier 30 for amplifying and outputting a selected high frequency frequency. A double tuner circuit 40 is connected to the output side of the radio frequency amplifier 20. The double tuning circuit 40 amplifies the entire band of the high frequency signal of the selected channel. The mixing circuit 50 is connected to the output terminal of the double tuning circuit 40. The mixing circuit 50 generates a local oscillation device 52 for generating a local oscillation frequency and a local oscillation device generated by the local oscillation device 52 at a frequency of a specific signal band amplified by the radio frequency amplification unit 30. And a mixer 54 for mixing the frequencies and converting them into intermediate frequency signals.

Therefore, the high frequency frequency of the specific channel band amplified by the radio frequency amplifier 30 is mixed with the local oscillation signal generated from the local oscillation device 52 in the mixer 54 and converted into an intermediate frequency signal. The local oscillator 40 generates a local oscillation signal obtained by adding an intermediate frequency to the carrier frequency of the currently received channel and inputs it to the mixer 52.

The video and audio signal processing device 60 is connected to the output terminal of the mixing circuit 50. The video and audio processing device 60 processes the intermediate frequency signal output from the mixing circuit 50 so that video and audio signals can be reproduced on a television. An AGC (Automatic Gain Control) circuit 70 is connected to the output terminal of the video and audio signal processing device 60. The AGC circuit 70 is configured to receive an intermediate frequency signal output to the video and audio signal processing device 60.

Therefore, the intermediate frequency signal output to the video and audio signal processing device 60 is detected, and a control signal is output to the radio frequency amplifier 30 according to the detected intermediate frequency signal to adjust the gain of the intermediate frequency signal. .

In the conventional television tuner configured as described above, a plurality of high frequency signals transmitted from broadcasting stations are received by the antenna 10 and applied to the tuning circuit 20. A plurality of high frequency signals applied to the tuning circuit 20 are tuned to extract only high frequency signals of a specific band corresponding to a channel input by the user. The high frequency of the specific band extracted by the tuning circuit 20 is applied to the radio frequency amplifier 30 and amplified. The high frequency signal of a specific band output from the radio frequency amplifier 20 is input to the demodulation circuit 40 to amplify the entire signal band. The high frequency signal output from the double tuning circuit 40 is applied to the mixing circuit 50. The mixing circuit 50 converts the local oscillation frequency generated by the local oscillation device 52 and the high frequency output from the demodulation circuit 40 through the mixer 54 and converts it into an intermediate frequency signal.

The intermediate frequency signal output from the mixing circuit 50 is signal-processed so that the video and audio signals can be reproduced on a television by the video and audio signal processing device 60. The intermediate frequency signal outputted to the video and audio signal processing device 60 is fed back to the AGC circuit 70. The AGC circuit 70 detects the intermediate frequency signal and adjusts the amplification ratio of the RF amplifier by outputting a control signal to the RF amplifier 30 according to the detected intermediate frequency signal.

In such a television tuner, the output of an intermediate frequency signal may vary according to frequency, power supply voltage, and temperature change. However, in the conventional tuner of the television, the output of the intermediate frequency is completely dependent on the adjustment of the amplification factor of the radio frequency amplification unit, and thus there is a problem in that a perfect intermediate frequency signal is output.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and a first object of the present invention is to add a detection device for detecting an intermediate frequency to a mixer of a television tuner so that the output of the intermediate frequency varies according to frequency, power supply voltage and temperature change. This provides a tuner's output control method that adjusts the mixer's conversion gain to maintain a stable mid-frequency from the mixer.

It is also a second object of the present invention to provide an apparatus suitable for performing the above-described tuner output control method.

1 is a block diagram for explaining the operation of a tuner of a general television.

2 is a block diagram illustrating an apparatus for controlling output of a tuner according to an embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating a mixing circuit in the tuner shown in FIG. 2.

* Description of the symbols for the main parts of the drawings *

102: antenna 104: tuning circuit

106: radio frequency amplifier 108: double-tuning circuit

200: mixing device 210: local oscillation device

220: mixer 240: intermediate frequency output control device

242: intermediate frequency detector 244: bias voltage output unit

R1 to R6: resistors Q1 to Q6, Q10: transistors

The output control method of the tuner according to the present invention for realizing the above first object,

Extracting only a high frequency signal of a band corresponding to a specific channel among a plurality of high frequency signals received through an antenna, amplifying the extracted high frequency signal, and demodulating the amplified signal;

Mixing the local oscillation frequency with a double-tuned high frequency signal through a mixer and converting it into an intermediate frequency signal;

Detecting an intermediate frequency signal and adjusting the gain of the mixer if the intermediate frequency signal is not normal; And,

The intermediate frequency signal level output from the mixer is fed back into the AGC circuit to adjust the amplification factor.

Further, the output control apparatus of the tuner according to the present invention for realizing the second object of the present invention described above,

A tuning circuit connected to the output of the antenna for selecting a high frequency signal of a specific band, a radio frequency amplifier for amplifying the selected high frequency by being connected to the output of the tuning circuit, and an output side of the radio frequency amplifying unit connected to the output of the high frequency signal of the selected channel A television tuner having a double tuning circuit for amplifying a signal,

It is connected to the output terminal of the double-tuning circuit, and consists of a local oscillation device and a mixer to convert the local oscillation frequency generated by the local oscillation device to a frequency of a specific signal band input from the double-tuning circuit through a mixer to convert into an intermediate frequency signal. Mixing circuit;

An intermediate frequency output control device connected to an output end of the mixing circuit for detecting an intermediate frequency output from the mixing circuit, and adjusting the gain of the mixer if the detected intermediate frequency signal is not normal; And,

AGC circuit for adjusting the amplification rate of the RF amplifier by receiving the intermediate frequency signal output to the audio and video signal processing device that receives the intermediate frequency signal output from the mixing circuit and the signal processing.

The intermediate frequency signal output from the mixer is detected, and the conversion gain of the mixer is adjusted according to the detected intermediate frequency signal so that the stable intermediate frequency signal is output from the mixer.

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

FIG. 2 is a block diagram showing an output control apparatus of a tuner according to the present invention, and FIG. 3 is a circuit diagram showing a mixed circuit among the tuners shown in FIG.

As shown in FIG. 2, the television tuner according to the exemplary embodiment has a configuration in which an intermediate frequency output control device 240 is connected to an output terminal of the mixing circuit 200. As illustrated in FIG. 3, the intermediate frequency output control device 240 is an intermediate frequency detector 242 and the intermediate frequency detector 242 for detecting an intermediate frequency output from the mixer 220 by branching from an output terminal of the mixer 220. And a bias voltage output unit 244 connected to the output terminal of 242 to adjust the output of the mixer 220 according to the detected intermediate frequency.

Referring to FIG. 2 again, in a tuner according to an embodiment of the present invention, a tuning circuit 104 is connected to an output side of an antenna 102 that receives a plurality of high frequency signals transmitted from a broadcasting station. An output terminal of the tuning circuit 104 is connected to a radio frequency amplifier 106 for amplifying and outputting selected high frequencies. A demodulation circuit 108 for amplifying the entire band of the high frequency signal of the selected channel is connected to the output side of the radio frequency amplifying unit 106. The mixing circuit 200 is connected to the output terminal of the double tuning circuit 108. The mixing circuit 200 generates a local oscillation frequency generated by the local oscillation device 210 at a frequency of a specific signal band inputted by the local oscillation device 210 and the demodulation circuit 108 to generate a local oscillation frequency. It is composed of a mixer 220 to mix and convert the intermediate frequency signal.

The output terminal of the mixing circuit 200 is connected to the video and audio signal processing device 230 for signal processing the intermediate frequency signal. The output terminal of the video and audio signal processing unit 230 is connected to the AGC circuit 250 for receiving the output intermediate frequency signal.

As shown in FIG. 3, the mixer 220 has a first differential amplifier stage 222 and a second differential amplifier stage 224 connected in two stages, and a first differential amplifier stage 222 and a second differential amplifier stage ( The mixer gain adjusting stage 226 is connected to one side of the 224. The first differential amplifier stage 222 is connected such that the first transistor Q1 and the second transistor Q2, which perform an amplification role, are symmetrically from side to side, and the base terminal and the second transistor of the first transistor Q1 are symmetrical to each other. Base terminals of Q2 are connected to the output side of the local oscillation device 210, respectively. The collector terminal of the first transistor Q1 and the collector terminal of the second transistor Q2 are connected to the driving power supply Vcc through the first resistor R1 for bias and the second resistor R2 for bias.

In addition, the output terminals a and b of the mixer 220 branch from the collector terminal of the first transistor Q1 and the collector terminal of the second transistor Q2.

The second differential amplifier stage 224 is connected such that the third transistor Q3 and the fourth transistor Q4, which perform an amplification role, are symmetrically from side to side, and the base terminal and the fourth transistor of the third transistor Q3 are connected to each other. The base terminal of Q4 is connected to the output side of the local oscillation device 210, respectively. The collector terminal of the third transistor Q3 and the collector terminal of the fourth transistor Q4 are output terminals of the mixer 220 branched from the collector terminal of the first transistor Q1 and the collector terminal of the second transistor Q2. It is connected to (a, b).

The emitter terminal of the first transistor Q1 and the emitter terminal of the second transistor Q2 are connected in common and are connected to the collector terminal of the fifth transistor Q5 in the mixer gain control stage 226. The emitter terminal of the third transistor Q3 and the emitter terminal of the fourth transistor Q4 are connected in common and are connected to the collector terminal of the sixth transistor Q6 in the mixer gain control stage 226. The base terminal of the fifth transistor Q5 and the sixth transistor Q6 is configured to receive a radio frequency signal of a specific band output from the double tuning circuit 108.

In addition, the emitter terminals of the fifth transistor Q5 and the sixth transistor Q6 are commonly connected to each other through the bias fourth resistor R4 and the fifth resistor R5 so that the mixer gain control transistor Q10 can be connected. It is connected to the collector terminal. The emitter terminal of the mixer gain adjusting transistor Q10 is grounded through the sixth resistor R6 for bias. In addition, one end of the fourth resistor R4 and the fifth resistor R5 is connected through the third resistor R3 for bias. Here, the intermediate frequency detector 242 of the intermediate frequency output control device 240 is branched at the output terminals a and b of the mixer 220. A bias voltage output unit 244 is connected to an output terminal of the intermediate frequency detector 242, and an output terminal of the bias voltage output unit 244 is connected to a base terminal of the mixer gain control transistor Q10.

Referring to the detailed operation of the tuner according to an embodiment of the present invention configured as described above are as follows.

A plurality of high frequency signals transmitted from broadcasting stations are received at the antenna 102 and applied to the tuning circuit 104. The tuning circuit 104 extracts only a high frequency signal of a specific band corresponding to a channel input by a user. That is, when the user changes the channel of the television, the tuning voltage is varied and input to the tuning circuit 104. The tuning circuit 104 adjusts the current level of the output frequency in accordance with the externally selected tuning voltage to extract a radio frequency band from a specific band. The high frequency of the specific band extracted by the tuning circuit 104 is applied to the radio frequency amplifier 106 and amplified. The high frequency signal of a specific band output from the radio frequency amplifier 106 is input to the demodulation circuit 108 to amplify the entire signal band. The high frequency signal output from the double tuning circuit 108 is amplified by about 20 kHz and applied to the mixing circuit 200 compared to the signal induced by the antenna 102.

In the mixed circuit 200, the local oscillation frequency applied by the local oscillator 210 is input to the first terminal Q1 of the first differential amplifier stage 222 and the base terminal of the second transistor Q2, and the second The third transistor Q3 of the differential amplifier stage 224 and the base terminal of the fourth transistor Q4 are input. In addition, a high frequency signal double-modulated by the double-tuning circuit 108 is applied to the base terminals of the fifth transistor Q5 and the sixth transistor Q6 in the mixer gain control stage 226.

Voltages of the output terminals a and b of the first differential amplifier stage 222 and the second differential amplifier stage 224 are current flowing through the fifth transistor Q5 and the sixth transistor Q6 of the mixer gain control stage 226. Proportional to That is, when a local oscillation frequency is applied to the base terminal of the first transistor Q1 of the first differential amplifier stage 222 and the base terminal of the second transistor Q2, the first transistor Q1 of the first differential amplifier stage 222 is applied. ) And a first resistor R1 and a second resistor R2 for bias to the collector terminals of the first transistor Q1 and the second transistor Q2 through a common connected emitter terminal of the second transistor Q2. The driving power source Vcc applied through the flows.

Similarly, when a local oscillation frequency is applied to the base terminal of the third transistor Q3 and the base terminal of the fourth transistor Q4 of the second differential amplifier stage 224, the bias terminal is applied to the collector terminal through a commonly connected emitter terminal. The driving power source Vcc applied through the first resistor R1 and the second resistor R2 flows.

The current flowing through the commonly connected emitter terminals of the first differential amplifier stage 222 and the second differential amplifier stage 224 is the base of the fifth transistor Q5 and the sixth transistor Q6 in the mixer gain control stage 226. It varies according to the radio frequency applied to the terminal. That is, when a radio frequency is applied to the base terminals of the fifth transistor Q5 and the sixth transistor Q6 in the mixer gain control stage 226, the emitter terminals of the fifth transistor Q5 and the sixth transistor Q6 are provided. At the emitter terminal commonly connected to the first differential amplifier 222 and the second differential amplifier 224 to the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 connected to the Current is applied.

As a result, the current of the output terminals (a, b) branched from the collector stages of the first differential amplifier stage 222 and the second differential amplifier stage 224 is equal to that of the first differential amplifier stage 222 and the second differential amplifier stage 224. This is the difference between collector currents. In this manner, the intermediate frequency output from the mixing circuit 200 has a value obtained by subtracting the double-tuned frequency from the local oscillation frequency.

Here, the intermediate frequency detector 242 of the intermediate frequency output control device 240 branched at the output terminals a and b of the mixing circuit 200 detects the intermediate frequency output from the mixing circuit 200. The signal level of the intermediate frequency output from the mixing circuit 200 is ideally about 100mV. The intermediate frequency detector 242 detects whether the signal level of the intermediate frequency output from the mixing circuit 200 is about 100 mV. The intermediate frequency detector 242 may use an AM frequency detection circuit. If it is determined that the intermediate frequency output from the mixer 220 is not normal, the intermediate frequency detector 242 outputs a signal to the bias voltage output unit 244. The bias voltage output unit 244 may be configured as a comparator.

The bias voltage output unit 244 compares the signal output from the intermediate frequency detector 242 with a reference signal and outputs a predetermined signal to the base terminal of the mixer gain control transistor Q10. For example, when the signal output from the intermediate frequency detector 242 is smaller than the reference signal, the bias voltage output unit 244 outputs a signal to the base terminal of the mixer gain adjusting transistor Q10 to give the mixer gain. The control transistor Q10 is turned on to increase the current output from the emitter stages of the transistors Q1 to Q4 constituting the first differential amplifier stage 222 and the second differential amplifier stage 224. Therefore, the magnitude of the voltage output from the collector terminals of the first differential amplifier stage 222 and the second differential amplifier stage 224 increases. As a result, the intermediate frequency signal level output from the mixer 220 is detected to adjust 15 kHz, which is an average gain of the mixer 220.

In addition, the intermediate frequency signal output from the mixing circuit 200 is signal-processed so that the video and audio signals can be reproduced on a television in the video and audio signal processing apparatus 230. The intermediate frequency signal output to the video and audio signal processing apparatus 2300 is fed back to the AGC circuit 230. The AGC circuit 230 detects an intermediate frequency signal and adjusts the gain of the intermediate frequency signal by outputting a control signal to the RF amplifier 106 according to the detected intermediate frequency signal.

The present invention detects the intermediate frequency signal level output from the mixer 220 to adjust the gain of the mixer 220 and at the same time to adjust the amplification rate of the radio frequency amplification unit 106 using the AGC circuit 230 Maintain a stable intermediate frequency signal level.

The present invention can stably maintain the intermediate frequency output from the mixer by detecting the intermediate frequency output from the mixer used in the television tuner and adjusting the conversion gain of the mixer when the output of the intermediate frequency is varied.

Although the present invention has been described in detail with reference to the accompanying drawings, the present invention is not limited thereto, and modifications and improvements are possible within the scope of ordinary knowledge of those skilled in the art.

Claims (7)

I) extracting only a high frequency signal of a band corresponding to a specific channel among a plurality of high frequency signals received through the antenna, amplifying the extracted high frequency signal, and demodulating the amplified signal; (II) mixing a local oscillation frequency into the intermediate frequency signal by mixing the double oscillated high frequency signal through a mixer; III) detecting the intermediate frequency signal and adjusting the gain of the mixer if the intermediate frequency signal is not normal; And, Ⅳ) a method of controlling the output of the tuner, comprising adjusting the amplification factor by feeding back the intermediate frequency signal level output from the mixer to an AGC circuit. The method of claim 1, wherein the step III comprises: i) detecting the signal level of the intermediate frequency; ii) comparing the signal level of the detected intermediate frequency with a reference signal; If less, the step of increasing the intermediate frequency signal level output from the mixer. The method of claim 2, wherein the step ii is a step of comparing whether the signal level of the intermediate frequency is 100mV. A tuning circuit 104 connected to an output side of the antenna 102 to select a high frequency signal of a specific band, a radio frequency amplifier 106 connected to an output terminal of the tuning circuit 104 to amplify the selected high frequency, and the radio frequency In the tuner of the television which is connected to the output side of the amplification part 106, and has the double-tuning circuit 108 which amplifies the whole band of the high frequency signal of a selected channel, The local oscillator 210 is connected to an output terminal of the double tuner circuit 108 and includes a local oscillator 210 and a mixer 220 at a frequency of a specific signal band input from the double tuner circuit 108. A mixing circuit (200) for mixing the generated local oscillation frequency through the mixer (220) to convert it into an intermediate frequency signal; Intermediate frequency output control for detecting an intermediate frequency embedded in the mixing circuit 200 and outputting from the mixer 220, and adjusting the signal level output from the mixer 220 if the detected intermediate frequency signal is not normal. Device 240; And, Adjusting the amplification ratio of the radio frequency amplifier 106 by receiving the intermediate frequency signal output from the audio and video signal processor 230 that receives the intermediate frequency signal output from the mixing circuit 200 and processes the signal. Tuner output control device, characterized in that configured for the AGC circuit (250). 5. The apparatus of claim 4, wherein the intermediate frequency output control device (240) comprises: an intermediate frequency detector (242) for detecting an intermediate frequency output from the mixing circuit (200); A base terminal is connected to an output terminal of the bias voltage output unit 244 and a bias voltage output unit 244 that are connected to an output terminal of the intermediate frequency detector 242 to output a signal for adjusting the gain of the mixer 220. The collector terminal is connected to a common connected emitter terminal of paired transistors Q5 and Q6 for receiving a radio frequency applied from the double-tuning circuit 108 as a base terminal, and the emitter terminal is a bias resistor. And an output control device of the tuner, characterized in that it is configured to be grounded through (R6) and configured with a mixer gain adjusting transistor (Q10) for adjusting the output voltage of the mixer (220). 6. The tuner's output control device according to claim 5, wherein the intermediate frequency detection section (242) comprises an AM frequency detection circuit. The apparatus of claim 5, wherein the bias voltage output unit (242) comprises a comparator.