KR20040004031A - Infrared-ray recceiver capable of removing noise - Google Patents

Abstract

PURPOSE: An infrared ray receiver having a noise cancellation function is provided to effectively suppress or remove various kinds of noise components inputted. CONSTITUTION: An infrared ray receiver having a noise cancellation function comprises an AGC(Automatic Gain Control) controller, a comparator block, a demodulator block, and an output circuit block. The AGC controller to adjust the gain of an AGC amplifier outputs Vagc voltage toward a direction to reduce the gain of the AGC amplifier, when an optical signal supplied to the infrared ray receiver is noise, so that the noise signal can be suppressed internally. The comparator block, composed of two comparators, compares the output signals of a BPF(Band Pass Filter) with reference voltages. The demodulator block demodulates the output signals of the comparator block. The output circuit block outputs the output of the demodulator block to the external of the infrared ray receiver.

Description

[0001] INFRARED-RAY RECEIVER CAPABLE OF REMOVING NOISE [0002]

The present invention relates to an infrared ray receiving apparatus for receiving and processing an infrared ray signal from an infrared remote controller or other infrared data transmitting apparatus used in household appliances such as TVs and VCRs. More particularly, to a technique for determining whether an input signal is a noise or a normal signal according to characteristics of a signal input to an infrared ray receiving apparatus.

1 is a block diagram of a conventional infrared ray receiving apparatus. Although FIG. 1 does not completely show all types of infrared ray receiving apparatuses, the infrared ray receiving apparatuses are generally shown in FIG. 1. The operation of the conventional infrared ray receiving apparatus will be described with reference to FIG.

First, the photodiode 10 senses an infrared signal from the outside and converts the infrared signal into an electric signal. Since the electric signal is a weak signal, the signal is amplified to a proper value through the first amplifier AV1 (11). The signal output from the first amplifier is transmitted to the second amplifier, that is, the limiter amplifier AV2 (12) via the first coupling capacitor C11. The signal amplified again by the limiter amplifier passes through the second coupling capacitor C12 again. The role of the first and second capacitors is to properly filter the DC (DC) signal components that the output of each amplifier may contain or contain. A signal having passed through the second coupling capacitor is filtered by a signal having an appropriate frequency bandwidth through a band pass filter (BPF) The output signal of the band-pass filter is again connected to the input of the comparator 14. Another input of the comparator is connected to the comparator reference voltage and the comparator compares the comparator reference voltage with the voltage of the output signal of the band pass filter. The output of the comparison unit 14 is connected to the demodulation unit 15 and the output signal of the demodulation unit is transmitted to the output circuit unit via the Schmitt trigger 16. The output circuit is composed of an output transistor TR11 and a pull-up resistor R11. The output transistor is usually connected to the base as an input, and the collector is connected to a pull- Structure. The output of the output circuit unit is usually connected to a microprocessor control unit (MCU) outside the infrared receiver.

In the prior art, the output from the photodiode 10 is input to a band-pass filter having a center frequency of approximately several tens of kHz (in the present invention, 38 kHz) after passing through two coupling capacitors and two amplifiers . The comparator reference voltage signal, which is another input of the comparator, is determined to have a voltage slightly higher than the average voltage of the bandpass filter output (e.g., on the order of several hundreds of mV). The comparator converts the signal into a TTL level signal when a voltage higher than the reference voltage is input from the bandpass filter and outputs the converted signal. This output signal is again demodulated in the demodulator 15 by removing the carrier frequency and leaving only the part called the "envelope" of the signal. The demodulated signal is finally output through the schmitt circuit section 16. [

On the other hand, an input signal to an infrared receiving apparatus coming from the outside usually includes not only an infrared component but also unwanted disturbance light such as fluorescent light or sunlight. Such a disturbance light eventually becomes a noise component, and such a noise component is also transmitted to the final output through a circuit inside the infrared ray receiving apparatus, which increases the possibility of malfunction due to noise. There is a kind of a device for removing such external noise in order to perform a reliable operation of the infrared ray receiving apparatus. Korean Patent Registration No. 322520, for example, additionally uses an Automatic Gain Controller (AGC) to remove such a noise component. Such a conventional patented invention is based on the idea that the infrared signal and the noise signal have different duty ratios. According to the conventional patented invention, as shown in FIG. 5, in the case of a normal signal, a period in which a signal is input is included in a carrier signal after being already modulated in a remote controller or the like, gap time). In the case of the normal signal, the ratio of the burst signal section to the entire section, that is, the duty ratio does not exceed 50%. In the conventional patented invention, a method of controlling the gain of the automatic gain control amplifier in the receiving device by using the voltage across the capacitor after charging and discharging the specific capacitor inside the infrared receiving device during the burst signal period and the rest period, Noise is suppressed. However, in such a conventional infrared ray receiving apparatus, when a noise signal that is larger than the reference voltage level of the comparator is received, there is a disadvantage that an output due to noise is generated in the comparator. If such an abnormal output is generated, the infrared ray receiving apparatus may malfunction, resulting in a reduction in the performance of the product or a reliability problem of the product. In addition, this method divides the signal and the noise by using the duty ratio of the signal and the noise. Therefore, when the duty ratio between the signals is not clearly distinguished, it is also difficult to distinguish the signal from the noise.

As the function of electronic devices becomes more complicated and diversified, infrared remote controllers and infrared receiving devices need to process complicated and various signals. Considering the trend of the present technology development, in which the duty ratio of the signal is diversified as the infrared signal input from the outside gradually becomes diversified, the conventional method of distinguishing the signal from the noise by the duty ratio gradually decreases the noise removing or suppressing effect .

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a reliable infrared receiver apparatus by effectively suppressing or eliminating noise components introduced into an infrared receiver apparatus.

Another object of the present invention is to ensure reliable operation of an electronic device in which the receiving apparatus of the present invention is incorporated due to such a reliable receiving apparatus.

Fig. 1 - Conventional infrared ray receiver

2 - Infrared receiving device of the present invention

3 is a detailed circuit diagram showing a gain control unit, a comparison unit, a demodulation unit, and an output circuit unit in the infrared ray receiving apparatus according to the present invention;

4 is a flowchart showing the operation of the infrared ray receiving apparatus according to the present invention;

5 shows an example of a normal signal inputted to the infrared ray receiving apparatus and a signal obtained by demodulation

Fig. 6 - An example of a fluorescent lamp noise signal that is radiated into the infrared receiver

7 shows another example of a fluorescent lamp noise signal which has been modulated so as to flow into the infrared ray receiving apparatus

8 - Brief circuit diagram of the AGC interface part

Figures 9 - 8 show timing diagrams

10 - Graph of the relationship between the gain of the automatic gain control amplifier and the regulated voltage

Description of the Related Art

10: photodiode 11: first amplifier (AV1)

12: a second amplifying unit (AV2) or an automatic gain control amplifier (AGC amp)

13: band pass filter (BPF) 14: comparator block

15: demodulator block 16: schmitt circuit

17: Gain control section (AGC) TR11: Final output transistor

R11: pull up resistance

The configuration and operation of the present invention will be described with reference to FIG. 2, which shows the infrared ray receiving apparatus of the present invention in a block diagram format. It should be noted that the symbols attached to the components of the present invention shown in FIG. 2 are the same as those of the components of the conventional infrared receiver shown in FIG. For convenience, coupling capacitors as shown in FIG. 1 are omitted in FIG. The role of these capacitors is as described above.

2, a photodiode 10 for detecting an infrared signal inputted from the outside and converting it into an electrical signal, a first amplifier 11 for amplifying the converted electrical signal into a signal of a predetermined size, An automatic gain control amplifier (AGC Amp) 12 whose gain is controlled by a gain controller 17 and which corresponds to a second amplifier for automatically re-amplifying the output signal of the first amplifier, A band pass filter (BPF) 13 for receiving a signal from the amplifier and passing only a signal having a constant frequency bandwidth, a comparator 14 for comparing the bandpass filter and the comparator reference voltages with each other, And an output circuit unit R11 and TR11 for outputting the output of the demodulation unit to the outside of the infrared ray receiving apparatus.

The operation of the gain adjustment unit 17, which is one of the essential components of the present invention, is a circuit for adjusting the gain of the automatic gain control amplifier 12 as described above. When the optical signal inputted to the infrared ray receiving device is noise, the Vagc voltage is outputted in the direction of reducing the gain of the automatic gain control amplifier 12 to suppress the noise signal in the infrared ray receiving device and increase the gain of the amplifier in other cases , Or keeps the Vagc voltage in the holding direction.

Hereinafter, operation and operation characteristics of each component of the present invention will be described with reference to FIG.

3 shows in detail the gain adjusting unit 17, the comparing unit 14, the demodulating unit 15, and the output circuit unit shown in FIG. The comparator located at the lower left of FIG. 3 is composed of two comparators. An output signal BPFOut of the bandpass filter and a first reference voltage Vthigh are connected to the lower comparator. An output signal BPFOut of the bandpass filter and a second reference voltage Vtlow are connected to the upper comparator input. The two output signals output from the comparator are input to the demodulator. The demodulator is also composed of two demodulators. Each of the two demodulators has two comparator outputs connected to it. The lower demodulator is electrically connected to the lower comparator and the upper demodulator is electrically connected to the upper comparator. The output Vhigh_demod of the bottom demodulator is connected to the input of the output circuitry. The gain control unit determines whether the signal received from the demodulation unit is a noise signal or a normal signal. If the signal is a noise signal, the gain control unit reduces the gain of the automatic gain control amplifier. If the signal is a normal signal, the gain control unit maintains the gain of the automatic gain control amplifier. The gain of the automatic gain control amplifier is increased so that the noise signal is effectively attenuated, suppressed or eliminated in the automatic gain control amplifier.

The operation of each block in the gain controller shown in FIG. 3 is as follows. The clock generator block generates various kinds of internal clock signals (clock1 to clockN) by receiving the output of the oscillator block.

The Gap Time Detection Block outputs GapTimeSig, which is an output signal, immediately when the idle period included in the signal output from the demodulator is longer than a predetermined period (for example, 25 ms) I make it.

As shown in the waveform of the normal signal shown in FIG. 5, a normal signal includes a burst section, which is an interval in which information is carried in the carrier signal, and a so-called idle period (gap period) . The characteristic of the normal signal coming from the remote controller is that the pausing period is several tens of milliseconds (ms), which is relatively longer than the noise signal. However, as shown in FIG. 6, when an example of a fluorescent lamp noise signal that is strongly modulated and introduced into the infrared receiver is a relatively non-resonant light noise signal, Quot; low " Referring to FIG. 6, a noise signal having a signal amplitude of about 4 ms is considered as a relatively small section, that is, a section that can be regarded as a dormant section. Using the difference in the duration of such a pause, it is possible to distinguish whether the signal input to the infrared receiver is noise or a normal signal. Fig. 7 shows a signal input from the fluorescent lamp. The feature of FIG. 7 does not specifically indicate the section that can be regarded as the rest period of the signal.

As described above, the noise signal has a relatively short rest period as compared with the normal signal. The signal detection block discriminates whether the output signal of the demodulation unit is a normal signal or a noise signal. 5, the "low" period of the demodulated signal corresponds to the burst period of the photodiode input signal and the "high" period of the demodulated signal corresponds to the remaining period of the photodiode input signal Section. If the " low "section of the demodulated signal is shorter than the predetermined width, the signal detecting section determines that the signal is noise and changes the output signal NOSIG of the signal detecting section to &Quot; low ". To summarize this again, the output signal of the signal detector varies according to the duration of the pause period included in the input signal of the signal detector.

The NOPULSE Detection Block outputs the output signal NOPULSE signal as "high" when the input signal is continuously "high" or continues to be "low," and when the pulse type signal continuously enters the input, the NOPLUSE signal It is the block that makes it "low". That is, it is a circuit in which the "high / low" state of the output signal is determined according to the characteristics of the input signal.

As shown in FIG. 3, the charge / discharge control unit receives the outputs of the pause detector, the signal detector, and the no pulse detector, and outputs a reset signal C_ch, C_dis, which is necessary for controlling the operation of the AGC interface, (reset) signal GapTimeRst.

The operation of the charging / discharging circuit and the operation of the AGC interface will be described with reference to a simplified circuit diagram and operation timing diagram of the AGC interface shown in FIGS. 8 and 9. FIG. 8 is a simplified symbol representation of a circuit for charge / discharge operation of a capacitor. When the signal input from the outside of the infrared receiver is noise, GapTimeSig, which is the output of the pause detector, will also generate "low ", so that the AGC interface unit generates" high " (C in Fig. 8) to increase the Vagc voltage, which is the output signal of the AGC interface unit. When GapTimeSig is "high" and the NOSIG signal is "high", there are two cases as follows. The first is when a noise input is input. At this time, the NOPULSE signal is "low". In this case, the C-ch signal becomes "high" so that the capacitor provided in the AGC interface unit is charged. Second, NOPULSE = "high" and C_dis signal is "high" when no input is inputted from the outside, so that the capacitor inside the AGC interface unit is discharged. If GapTimeSig = "high" and NOSIG = "low", it indicates that the signal coming from the outside of the infrared receiver is a normal signal. In this case, both the C-ch and C-dis signals are kept in a "low" state, so that the capacitors in the AGC interface do not charge or discharge, so that the gain of the automatic gain control amplifier is kept unchanged.

The operation of the AGC interface unit of FIG. 3 can be summarized again to generate a control voltage Vagc for receiving the C_ch and C_dis output signals of the charge / discharge control unit and controlling the gain of the automatic gain control amplifier. In the present invention, the case where the gain of the automatic gain control amplifier is reduced when the Vagc voltage increases is described as an example. However, there are various modified design types for the automatic gain control amplifier. It is also possible to increase the number of amplification stages used in the receiving apparatus of the present invention as needed.

The circuit operation of the present invention described above mainly explains the functions and interactions of the respective blocks with reference to FIG. 3, which is shown in FIG. 4 as a flowchart.

10 shows the relationship between the gain of the automatic gain control amplifier and the automatic gain control voltage Vagc. It can be seen that the gain of the amplifier is designed to decrease as the Vagc increases.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it should be understood that the same is by way of illustration and example only and is not for the purpose of limitation. For example, it is possible to detect a resting period of 20 to 25 ms or less in the detector of the pausing period, to change the reference during the detection operation of the signal detecting section or the no-pulse detecting section, or to change the reference voltage of the comparing section, Various changes and modifications may be made without departing from the spirit of the invention.

In consideration of the characteristics of the input signal, that is, the characteristics of the noise signal and the normal input, in processing the input signal of the infrared receiver, unlike the conventional method, the amplifier gain in the infrared receiver is converted into the noise signal And if it is a normal signal, it can be adjusted differently. According to the present invention, it is possible to provide a reliable infrared ray receiving apparatus and to improve the reliability of an electronic apparatus having an infrared ray receiving apparatus.

Claims (3)

Converts an optical signal into an electrical signal, Amplifying the converted signal, Filtering the amplified signal to filter out a specific component, Comparing the filtered signals with predetermined reference voltages, Demodulating a signal of a specific component from the compared signal, And outputs the demodulated signal to the outside, Wherein feedback control is used to control amplification magnitude of the converted signal according to a state of the demodulated signal, wherein the feedback control is performed based on a voltage increase / decrease of a specific capacitor. A receiver for receiving an optical signal; An amplifying unit for amplifying the received optical signal; A filter unit for filtering the amplified signal; A comparator for comparing the filtered signal with a predetermined reference voltage signal; A demodulator for demodulating the compared result; And a gain control unit using feedback control to control the gain of the amplifier according to the state of the demodulated signal and a circuit for controlling the operation of the specific capacitor and the capacitor for the feedback control And a light receiving device for receiving the light. 3. The method according to claim 1 or 2, Wherein the feedback control uses a switch circuit and a current source circuit for charging / discharging the capacitor.