JP2010010817A - Pulse communication reception circuit, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a backward signal or to ensure that such a signal rarely arises, in order to prevent malfunction. <P>SOLUTION: The pulse communication reception circuit 100 includes a low frequency cut filter 104, a voltage amplifier 105, a low frequency cut filter 106, a low frequency cut filter 108, an adder 110, and a binarization circuit 111. The low frequency cut filter 104 removes a low frequency component of an input signal based on a first low pass cut-off frequency. The voltage amplifier 105 amplifies the signal from which the low frequency component is removed. The low frequency cut filter 106 removes a low frequency component of the amplified signal based on a second low pass cut-off frequency. The low frequency cut filter 108 removes a low frequency component of input signal based on a third low pass cut-off frequency. The adder 110 adds a signal of which the low frequency component is removed by the low frequency cut filter 106 and a signal of which the low frequency component is removed by the low frequency cut filter 108. The binarization circuit 111 compares the signal added by the adder 110 with a threshold to create a binarized pulse signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pulse communication receiving circuit used in a pulse communication system such as digital communication, and an electronic apparatus including the same, and more particularly to a pulse receiving technique of a wireless communication system.

  In transmission of a digital signal in a wireless communication system such as optical communication, the signal level input to the receiving element is not constant and usually has a width of 5 digits or more. Therefore, the receiver is required to be devised so as not to saturate even an excessive input while being required to have a gain that can cope with a weak signal input. Various methods have been considered in this regard, and one of them is known as a method for generating a received pulse by detecting only the edge of an input optical pulse signal as shown in FIG. Yes.

  FIG. 8 is a diagram illustrating signal waveforms of a method for generating a reception pulse using pulse edge detection.

  In this method, first, the low frequency component of the input signal is removed, and only the edge is extracted. Next, in order to be able to respond to a weak signal, the extracted edge is amplified by a high gain amplifier. Finally, the amplified signal is binarized by comparing with preset threshold values + Vth and −Vth. As a result, by not using the amplitude information of the input signal, it is possible to generate a received pulse without saturating the amplifier even at a large input.

  However, an amplifier always has an offset voltage (DC offset). The offset voltage appears in the output signal such that the higher the amplifier, the greater the signal level difference. For this reason, even if the output signal of the high gain amplifier is directly compared with the threshold value, variation occurs due to the influence of the offset voltage, and normal operation cannot be expected.

  A technique for canceling the offset voltage of the amplifier is described in Patent Document 1, for example. In other words, in order to cancel the offset voltage of the amplifier, it is necessary to remove the low frequency component including the direct current component of the signal from the output signal of the high gain amplifier and compare it with the threshold value. Therefore, the low frequency component is removed twice.

  However, by removing the low frequency component twice, as shown in FIG. 9, an edge in the reverse direction is generated, and if the signal exceeds the threshold value, a malfunction (reduction in the pulse width of the output signal, There was a new problem of generating false pulses.

To deal with this problem, for example, in Patent Document 2, by adding a part of the signal before the removal to the signal from which the first low-frequency component was removed, compared to the amplitude at the rising edge of the edge signal, A technique for reducing the amplitude at the time of falling is described. Thereby, the amplitude of the signal generated in the reverse direction is suppressed by removing the low-frequency component for the second time, and malfunction is suppressed.
JP 2002-232271 A (released on August 16, 2002) JP 2003-204253 A (published July 18, 2003)

  However, the technique described in Patent Document 2 has a problem in that the signal generated in the reverse direction is suppressed but cannot be eliminated, and the generation amount cannot be controlled. ing. Because of this problem, in order to prevent malfunction, it is necessary to provide a margin for the threshold value, and the reception sensitivity cannot be improved.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to eliminate a signal generated in the reverse direction, or control the pulse so as to be equal to none, thereby preventing a malfunction. An object of the present invention is to provide a communication receiving circuit and an electronic device including the communication receiving circuit.

  In order to solve the above problems, a pulse communication receiving circuit of the present invention includes a first filter circuit that removes a low-frequency component of an input signal based on a first low-frequency cutoff frequency, and a low-frequency component by the first filter circuit. A first amplifier that amplifies the signal from which the signal has been removed, a second filter circuit that removes a low-frequency component of the signal amplified by the first amplifier based on a second low-frequency cutoff frequency, and the second filter circuit A pulse communication receiving circuit comprising: a binarization circuit that generates a binarized pulse signal by comparing a signal from which a low frequency component has been removed with a threshold value; A third filter circuit for removing based on the three low-frequency cut-off frequencies, and a signal from which the low-frequency component has been removed by the third filter circuit is supplied to the binarization circuit by the second filter circuit. It is characterized by being summed on the signal low-frequency components removed.

  According to the above configuration, the pulse signal is created using only the edge of the input signal detected by the first filter circuit. Further, the output signal of the first filter circuit is amplified by the first amplifier. Thus, for example, when used in a communication system in which the amplitude level of the input signal changes significantly, such as an optical communication system, prevention of pulse width distortion due to amplifier saturation when the input signal strength is large, and the strength of the input signal It becomes possible to achieve both sensitivity ensuring when small.

  In addition, an offset voltage due to amplification is generated in the output signal of the first amplifier, but the offset voltage is removed by the second filter circuit. Further, the signal from which the low-frequency component has been removed by the second filter circuit includes a signal component that is generated in the reverse direction by performing the low-frequency removal twice, but the third filter circuit Thus, the signal from which the low frequency component has been removed is canceled by being added to the signal from which the low frequency component has been removed by the second filter circuit supplied to the binarization circuit. That is, the third filter circuit cancels the signal component generated in the reverse direction by generating a signal having the same component as the signal component generated in the reverse direction by the two low frequency removals. As a result, when binarizing, the signal to be compared with the threshold does not have a signal component generated in the reverse direction, so that malfunction can be prevented.

  In order to solve the above-described problem, the pulse communication receiving circuit of the present invention has a first filter circuit that removes a low-frequency component of an input signal based on a first low-frequency cutoff frequency, and a low frequency by the first filter circuit. A first amplifier that amplifies the signal from which the frequency component has been removed; a second filter circuit that removes a low-frequency component of the signal amplified by the first amplifier based on a second low-frequency cutoff frequency; and the second filter. A pulse communication receiving circuit comprising: a binarization circuit that creates a binarized pulse signal by comparing a signal from which a low frequency component has been removed by a circuit with a threshold value, the low frequency component of the input signal Is removed based on the third low-frequency cutoff frequency, and the voltage level of the signal from which the low-frequency component is removed by the third filter circuit is the threshold voltage used by the binarization circuit. It is characterized by being subtracted from the bell.

  According to the above configuration, the pulse signal is created using only the edge of the input signal detected by the first filter circuit. Further, the output signal of the first filter circuit is amplified by the first amplifier. Thus, for example, when used in a communication system in which the amplitude level of the input signal changes significantly, such as an optical communication system, prevention of pulse width distortion due to amplifier saturation when the input signal strength is large, and the strength of the input signal It becomes possible to achieve both sensitivity ensuring when small.

  In addition, an offset voltage due to amplification is generated in the output signal of the first amplifier, but the offset voltage is removed by the second filter circuit. Further, the signal from which the low-frequency component has been removed by the second filter circuit includes a signal component that is generated in the reverse direction by performing the low-frequency removal twice, but the third filter circuit By subtracting the voltage level of the signal from which the low-frequency component has been removed by the threshold voltage level used by the binarization circuit, the threshold value changes following the signal component in the reverse direction.

  Thereby, even if there is a signal component generated in the reverse direction, the signal component generated in the reverse direction does not exceed the threshold value. Therefore, when binarization is performed, the signal to be compared with the threshold value is equal to the absence of a signal component generated in the reverse direction, so that malfunction can be prevented.

  The pulse communication receiving circuit of the present invention further includes a second amplifier for amplifying the input signal, and the signal amplified by the second amplifier is supplied to the first filter circuit and the third filter circuit. Preferably it is.

  According to the above configuration, the overall gain can be further increased. In particular, when the input signal has insufficient driving capability with respect to the input impedances of the first filter circuit and the third filter circuit, the input signal is buffered by the second amplifier, so that the first filter circuit and the first filter circuit This is very useful because it is less susceptible to the input impedance of the three-filter circuit.

  However, in the configuration including the second amplifier, when a DC component is on the input signal, the dynamic range of the second amplifier may be narrowed by the DC component. Therefore, in the pulse communication receiving circuit of the present invention, the output terminal of the second amplifier, the input terminal of which is connected to the output terminal of the second amplifier and the output terminal of which is connected to the input terminal of the second amplifier. It is desirable to further include a third amplifier that extracts and amplifies the direct current component and the low frequency component based on the high frequency cutoff frequency.

  According to the above configuration, it is possible to remove the DC component superimposed on the input signal by subtracting the DC component and low frequency component of the output signal of the second amplifier from the input signal input to the second amplifier. Become. Thereby, it is possible to prevent the dynamic range of the second amplifier from being narrowed.

  In the pulse communication receiving circuit of the present invention, it is preferable that the high frequency cutoff frequency of the third amplifier is set to a frequency that is one digit lower than the frequency of the input signal. As a result, since the frequency component to be removed by the third amplifier substantially does not include the signal component, it is possible to prevent deterioration of the input signal itself due to the addition of the third amplifier.

  Alternatively, in the pulse communication receiving circuit of the present invention, the high frequency cutoff frequency of the third amplifier is lower than the first low frequency cutoff frequency of the first filter circuit and the second low frequency cutoff frequency of the second filter circuit. The frequency may be set to be one digit lower than the other frequency. As a result, the frequency component removed from the input signal by the third amplifier has a frequency that does not substantially function for the first filter circuit and the second filter circuit, thereby affecting the waveform operation by the first filter circuit and the second filter circuit. It is possible not to give.

  In addition, the pulse communication receiving circuit of the present invention removes the low frequency component by the second filter circuit in order to suitably control and exhibit the effect of adding and canceling, or the effect of changing the threshold value by subtracting. The amplified signal is preferably amplified. Furthermore, it is desirable that the signal from which the low frequency component is removed by the third filter circuit is amplified.

  In the pulse communication receiver circuit of the present invention, the third low-frequency cutoff frequency of the third filter circuit is the first low-frequency cutoff frequency of the first filter circuit and the second low-frequency cutoff frequency of the second filter circuit. It is preferable that the same frequency as the lower frequency is set. As a result, the time constant of the signal from which the low-frequency component has been removed by the third filter circuit can be made to coincide with the time constant of the signal component generated in the reverse direction, and the above-described effects can be optimized. Become.

  Alternatively, in the pulse communication receiving circuit of the present invention, the third low frequency cutoff frequency of the third filter circuit is the first low frequency cutoff frequency of the first filter circuit and the second low frequency cutoff frequency of the second filter circuit. Of these, the lower frequency may be set. As a result, even when the time constant of the signal component generated in the reverse direction changes due to fluctuations in the waveform of the input signal or amplifier characteristics, correction is performed with the fluctuation waveform for a longer time. It is possible to reduce the change of.

  Further, in the pulse communication receiving circuit of the present invention, the first filter circuit, the second filter circuit, and the third filter circuit are capacitors in which elements for setting the respective low-frequency cutoff frequencies are created in the same manufacturing process. It is preferable that it is comprised by the element and resistance. As a result, the relative error between the elements can be minimized, and the relative deviation of the low-frequency cutoff frequencies of the first filter circuit, the second filter circuit, and the third filter circuit can be suppressed. It is possible to maintain the same relationship or the magnitude relationship.

  Alternatively, in the pulse communication receiving circuit of the present invention, the first filter circuit, the second filter circuit, and the third filter circuit are capacitors in which elements for setting the respective low-frequency cutoff frequencies are created in the same manufacturing process. You may comprise by the element and the current source with the same characteristic produced | generated from one current source circuit. As a result, it is possible to suppress the relative deviation of the low cutoff frequency determined from the time constant determined according to the capacitance and current value of the first filter circuit, the second filter circuit, and the third filter circuit. Thus, it is possible to match the time constants or maintain the magnitude relationship.

  In addition, an electronic device according to the present invention has a wireless or wired communication function and includes the pulse communication receiving circuit.

  According to the above configuration, since the pulse communication receiving circuit creates a normal pulse signal according to the width of the received optical pulse signal, the reception sensitivity is improved when used in a digital transmission system having a pulse width of information. Can be expected. In particular, since the receiving sensitivity can be improved, it is useful for improving the communication distance in infrared communication. Further, when used in a wireless communication system such as optical communication, a pulse signal can be suitably created even if the received signal level has a large range.

  As described above, the pulse communication receiving circuit of the present invention includes the third filter circuit that removes the low-frequency component of the input signal based on the third low-frequency cutoff frequency, and the low-frequency component is removed by the third filter circuit. This signal is added to the signal from which the low frequency component has been removed by the second filter circuit supplied to the binarization circuit.

  Therefore, the signal from which the low frequency component has been removed by the second filter circuit includes a signal component that is generated in the reverse direction by performing the low frequency removal twice. The signal from which the low frequency component has been removed by the circuit is canceled by being added to the signal from which the low frequency component has been removed by the second filter circuit supplied to the binarization circuit. Therefore, when binarization is performed, the signal to be compared with the threshold value has no signal component generated in the reverse direction, so that it is possible to prevent malfunction.

  The pulse communication receiving circuit of the present invention further includes a third filter circuit that removes a low frequency component of the input signal based on the third low-frequency cutoff frequency, and the signal of which the low frequency component has been removed by the third filter circuit. The voltage level is subtracted from the threshold voltage level used by the binarization circuit.

  Therefore, the signal from which the low frequency component has been removed by the second filter circuit includes a signal component that is generated in the reverse direction by performing the low frequency removal twice. Since the voltage level of the signal from which the low frequency component has been removed by the circuit is subtracted from the threshold voltage level used by the binarization circuit, the threshold value changes following the signal component in the reverse direction. Therefore, even if there is a signal component generated in the reverse direction, the signal component generated in the reverse direction does not exceed the threshold value. Accordingly, when binarization is performed, the signal to be compared with the threshold value is equal to the absence of a signal component generated in the reverse direction, so that it is possible to prevent malfunction.

  In addition, an electronic apparatus according to the present invention has a wireless or wired communication function and includes the pulse communication receiving circuit.

  Therefore, since the pulse communication receiver circuit creates a normal pulse signal according to the width of the received optical pulse signal, it should be expected to improve reception sensitivity when used in a digital transmission system in which the pulse width has information. There is an effect that can be. This is also useful for improving the communication distance in infrared communication. Furthermore, when used in a wireless communication system such as optical communication, there is an effect that a pulse signal can be suitably created even if the received signal level has a large range.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

(Configuration of pulse communication receiver circuit)
FIG. 1 is a circuit diagram showing a configuration example of the pulse communication receiving circuit 100 of the present embodiment.

  As shown in FIG. 1, the pulse communication receiving circuit 100 includes a photodiode 101, a first-stage amplifier 102 (second amplifier), a high-frequency cutoff amplifier 103 (third amplifier), a low-frequency cut filter 104 (first filter circuit), Voltage amplifier 105 (first amplifier), low frequency cut filter 106 (second filter circuit), voltage amplifier 107, low frequency cut filter 108 (third filter circuit), voltage amplifier 109, adder 110, binarization circuit 111 , A first fixed power source 112, a second fixed power source 113, and an output terminal 114.

  The photodiode 101 receives an optical pulse signal transmitted from a transmitter (not shown). The photodiode 101 passes a current signal by receiving (inputting) an optical pulse signal. This current signal is output to the first stage amplifier 102.

  The first stage amplifier 102 is an amplifier that converts the current signal output from the photodiode 101 into a voltage signal and amplifies it. The first stage amplifier 102 outputs the amplified voltage signal to the low frequency cut filter 104 and also to the low frequency cut filter 108.

  The high-frequency cutoff amplifier 103 is an amplifier that extracts and amplifies the DC component and low-frequency component of the voltage signal output from the first-stage amplifier 102 based on a predetermined high-frequency cutoff frequency. The high-frequency cutoff amplifier 103 has an input terminal connected to the output terminal of the first stage amplifier 102, an output terminal connected to the input terminal of the first stage amplifier 102, and an input to the first stage amplifier 102 based on the output voltage of the first stage amplifier 102. The current signal generated so as to cancel the DC component of the current signal is fed back to the input of the first stage amplifier 102.

  Further, the high-frequency cutoff frequency of the high-frequency cutoff amplifier 103 is one or more orders of magnitude lower than the frequency of the optical pulse signal, or the low-frequency cutoff frequency fc4 of the low-frequency cutoff filter 104 and the low-frequency cutoff filter 108 are low. It is set to a frequency one digit or more lower than the lower one of the band cutoff frequencies fc8.

  The low-frequency cut filter 104 is a filter that removes a low-frequency component of the voltage signal based on the inherent low-frequency cutoff frequency fc4, and is provided to detect a rising edge and a falling edge of the voltage signal. The low frequency cut filter 104 passes the high frequency component of the voltage signal output from the first stage amplifier 102 and outputs the high frequency component to the voltage amplifier 105.

  The voltage amplifier 105 amplifies the voltage signal output from the low frequency cut filter 104 and outputs it to the low frequency cut filter 106. The gain (gain) of the voltage amplifier 105 is set so as to be sensitive even when the intensity of the optical pulse signal input to the photodiode 101 is small and the voltage signal output from the low-frequency cut filter 104 is weak. ing.

  The low-frequency cut filter 106 is a filter that removes a low-frequency component including a DC component of the voltage signal based on the inherent low-frequency cutoff frequency fc6, and eliminates the influence of the offset voltage generated by the voltage amplifier 105. Is provided. The low frequency cut filter 106 passes the high frequency component of the voltage signal output from the voltage amplifier 105 and outputs it to the voltage amplifier 107.

  The voltage amplifier 107 amplifies the voltage signal output from the low frequency cut filter 106 and outputs it to the adder 110. The gain of the voltage amplifier 107 is set to be lower than the gain of the voltage amplifier 105, for example, as long as it can be sufficiently used in the binarization circuit 111.

  The low-frequency cut filter 108 is a filter that removes a low-frequency component of the voltage signal based on the inherent low-frequency cutoff frequency fc8, and is generated in the reverse direction included in the voltage signal supplied to the binarization circuit 111. It is provided in order to eliminate the influence of the signal component. The low frequency cut filter 108 passes the high frequency component of the voltage signal output from the first stage amplifier 102 and outputs the high frequency component to the voltage amplifier 109.

  The voltage amplifier 109 amplifies the voltage signal output from the low frequency cut filter 108 and outputs the amplified signal to the adder 110. The gain of the voltage amplifier 109 is set in accordance with the gains of the voltage amplifiers 105 and 107 as will be described later.

  The adder 110 adds (adds) the voltage signal output from the voltage amplifier 107 and the voltage signal output from the voltage amplifier 109. The adder 110 outputs the added voltage signal to the binarization circuit 111.

  The binarization circuit 111 compares the voltage signal output from the adder 110 with the threshold voltage + Vth supplied from the first fixed power supply 112 and the threshold voltage −Vth supplied from the second fixed power supply 113, respectively. Thus, a binarized pulse signal is created. The first fixed power supply 112 has a plus terminal connected to the binarization circuit 111 and a minus terminal grounded. The second fixed power supply 113 has a minus terminal connected to the binarization circuit 111 and a plus terminal grounded. The binarization circuit 111 outputs the created pulse signal to the output terminal 114.

  The low-frequency cut filters 104, 106, and 108 preferably have the same configuration as will be described later. A detailed configuration of the low-frequency cut filters 104, 106, and 108 will be described.

  FIG. 3 is a circuit diagram showing a simple example of a low-frequency cut filter. As shown in FIG. 3, the low frequency cut filter includes an input unit 151, a capacitor 152 (capacitance element) having a capacitance C, a resistor 153 having a resistance R, and an output unit 154. The capacitor 152 has one terminal connected to the input unit 151 and the other terminal connected to the output unit 154. The resistor 153 has one terminal connected to the other terminal of the capacitor 152 and the other terminal grounded. In the low-frequency cut filter shown in FIG. 3, the time constant is “C · R”, and the low-frequency cutoff frequency is “f = 1 / (2π · C · R)”.

  FIG. 4 shows another example of the low frequency cut filter. As shown in FIG. 4, the low-frequency cut filter includes an input unit 161, a bipolar transistor 162, a constant current source 163 (current source) that generates a current i, a capacitor 164 (capacitance element) having a capacitance C, and an output unit 165. It is comprised by. The bipolar transistor 162 has a base connected to the input unit 161, a collector connected to the output unit 165, and an emitter connected to the constant current source 163 and the capacitor 164. The other end of the capacitor 164 is grounded.

  In the low-frequency cut filter shown in FIG. 4, the time constant is “Vt · C / i” (Vt: thermal voltage of semiconductor). Thereby, the time constant can be controlled by the current flowing through the bipolar transistor 162.

(Signal processing operation of pulse communication receiver circuit)
Next, the signal processing operation of the pulse communication receiving circuit 100 will be described with reference to FIGS.

  FIG. 2 is a diagram illustrating each signal waveform of the pulse communication receiving circuit 100.

  When the optical pulse signal is received by the photodiode 101, a current signal is output from the photodiode 101 to the first stage amplifier 102, and a voltage signal V1 is output from the first stage amplifier 102. The voltage signal V1 has a signal waveform having the same width as that of the optical pulse signal. The voltage signal V1 is output to the low frequency cut filter 104 and the low frequency cut filter 108, respectively.

  Note that the current signal is buffered by the first stage amplifier 102 even when the optical pulse signal (that is, the current signal) is not sufficiently drivable with respect to the input impedance of the low frequency cut filter 104 and the low frequency cut filter 108. As a result, the voltage signal output from the first-stage amplifier 102 is less affected by the input impedance. Therefore, providing the first stage amplifier 102 is very useful.

  However, by providing the first stage amplifier 102, when a direct current component is on the current signal, the dynamic range of the first stage amplifier 102 may be narrowed by the direct current component. In such a case, the high-frequency cutoff amplifier 103 subtracts the DC component and low-frequency component of the output signal of the first stage amplifier 102 from the input signal input to the first stage amplifier 102, thereby superimposing the DC component on the input signal. Can be removed. Therefore, it is possible to prevent the dynamic range of the first stage amplifier 102 from being narrowed.

  At this time, when the high-frequency cutoff frequency of the high-frequency cutoff amplifier 103 is set to a frequency that is one digit or more lower than the frequency of the optical pulse signal, the high-frequency cutoff amplifier 103 has a frequency component to be removed. Since almost no signal component is included, it is possible to prevent deterioration of the optical pulse signal itself due to the provision of the high-frequency cutoff amplifier 103.

  Alternatively, the high-frequency cutoff frequency of the high-frequency cutoff amplifier 103 is one digit or more higher than the lower one of the low-frequency cutoff frequency fc4 of the low-frequency cutoff filter 104 and the low-frequency cutoff frequency fc8 of the low-frequency cutoff filter 108. When the frequency is set to a low frequency, the frequency component removed from the current signal by the high-frequency cutoff amplifier 103 becomes a frequency that does not substantially function for the low-frequency cut filter 104 and the low-frequency cut filter 108. It is possible to prevent the waveform operation by the filter 104 and the low frequency cut filter 108 from being affected.

  Subsequently, the low frequency component is removed from the voltage signal V1 output to the low frequency cut filter 104 by the low frequency cut filter 104, and the voltage signal V2 is output from the voltage amplifier 105. Here, it is assumed that the rise time and fall time of the voltage signal V1 are sufficiently higher than the low-frequency cutoff frequency fc4 of the low-frequency cut filter 104. In this case, the rising component and falling component of the voltage signal V1 are not affected by the low-frequency cut filter 104, but the DC component of the voltage signal V1 is attenuated according to the low-frequency cutoff frequency fc4.

  As a result, the voltage amplifier 105 only amplifies the output signal of the low frequency cut filter 104, so that the voltage signal V2 becomes a signal waveform based on the waveform formed by the low frequency cut filter 104. That is, as shown in FIG. 2, a signal waveform is detected in which the rising edge and falling edge of the voltage signal V1 are detected. An attenuation curve corresponding to the low-frequency cutoff frequency fc4 is drawn between the rising edge and the falling edge.

  The low-frequency component including a direct current component is removed from the voltage signal V2 output from the voltage amplifier 105 by the low-frequency cut filter 104, and is output from the voltage amplifier 107 to the adder 110 as the voltage signal V3. The voltage signal V2 has an offset voltage generated by amplification by the voltage amplifier 105, but the low-frequency cut filter 104 eliminates the influence of the offset voltage on the voltage signal V3.

  Here, similarly to the low-frequency cut filter 104, the low-frequency cutoff frequency fc6 of the low-frequency cut filter 106 is sufficiently lower than the frequency of the rise time and fall time of the voltage signal V1. In this case, the rising and falling components of the voltage signal V1 appearing in the voltage signal V2 are not affected by the low-frequency cut filter 106, but are attenuated according to the low-frequency cutoff frequency fc4 appearing in the voltage signal V2. The components are spurred to be attenuated by the low-frequency cut filter 106.

  As a result, the voltage amplifier 107 only amplifies the output signal of the low frequency cut filter 106, so that the voltage signal V3 becomes a signal waveform based on the waveform formed by the low frequency cut filter 106. That is, as shown in FIG. 2, a signal waveform is detected in which the rising edge and the falling edge of the voltage signal V1 are detected, but the signal is generated in the opposite direction between the rising edge and the falling edge. Between the rising edge and the falling edge, an attenuation curve substantially corresponding to the low cut-off frequency fc6 is drawn.

  Here, if the frequency of the rise time and fall time of the voltage signal V1 is sufficiently higher than the low cut-off frequencies fc4 and fc6 of the low frequency cut filters 104 and 106, the voltage signal V1 is regarded as a rectangular wave. Can do. In this case, the voltage signal V3 after passing through the low-frequency cut filters 104 and 106 is expressed by the following equation (1).

V3 = τ6 / (τ6-τ4) · exp (−t / τ4)
−τ4 / (τ6-τ4) · exp (−t / τ6) (1)
τ4: Time constant corresponding to the low-frequency cutoff frequency fc4 of the low-frequency cut filter 104 τ6: Time constant corresponding to the low-frequency cutoff frequency fc6 of the low-frequency cutoff filter 106 t: When the time for the voltage signal V1 to rise is zero Note that the expression (1) is an expression expressing the voltage signal V1 from the rise at t = 0 to the point before the fall, and the gain in the voltage amplifiers 105 and 107 is not taken into consideration.

  It is desirable that the value of τ4 be equal to or smaller than the minimum pulse width of the received optical pulse signal. That is, τ4 increases as the low-frequency cutoff frequency fc4 of the low-frequency cut filter 104 decreases. That is, the attenuation curve becomes gentle. For this reason, the purpose of the low-frequency cut filter 104 is to detect the edge of the input signal. However, when the attenuation curve becomes gentle, it does not converge at the time of falling of the input signal, and the amplitude of the falling waveform becomes small. The problem occurs. Further, since the same occurs even when the input signal rises, as a result, the amplitude of the voltage signal V2 becomes small. Therefore, in order to prevent this, it is desirable to set the value of τ4 to be equal to or smaller than the minimum pulse width of the received optical pulse signal.

  Further, since the low-frequency cut filter 106 is intended to remove the offset voltage of the voltage amplifier 105, the low-frequency cut-off frequency fc6 needs to be as small as possible in manufacturing, that is, τ6 must be large. Therefore, τ4 << τ6 (fc4 >> fc6) is usually obtained.

  In the case of τ4 << τ6, in the equation (1), the term on the left side of the equation is dominant and the term on the right side is almost a constant when 0 << t <τ4. On the other hand, when t> τ4, the term on the left side of the equation is almost 0, and the term on the right side of the equation becomes dominant. Therefore, the right side of the equation is a subtraction term, and the left side term is almost 0. Therefore, when t> τ4, the voltage signal V3 takes a negative value. This means that a signal is generated in the reverse direction.

  On the other hand, the low frequency component of the voltage signal V1 output to the low frequency cut filter 108 is removed by the low frequency cut filter 108, and the voltage signal 109 is output to the adder 110 as the voltage signal V4. Here, similarly to the low-frequency cut filter 104, the low-frequency cutoff frequency fc8 of the low-frequency cut filter 108 is sufficiently lower than the frequency of the rise time and fall time of the voltage signal V1. In this case, the rising component and falling component of the voltage signal V1 are not affected by the low-frequency cut filter 108, but the DC component of the voltage signal V1 is attenuated according to the low-frequency cutoff frequency fc8.

  Thus, since the voltage amplifier 109 only amplifies the output signal of the low frequency cut filter 108, the voltage signal V4 detects the rising edge and the falling edge of the voltage signal V1, as shown in FIG. It becomes a signal waveform. An attenuation curve corresponding to the low-frequency cutoff frequency fc8 is drawn between the rising edge and the falling edge. 2 shows a case where the gain of the voltage amplifier 109 is set lower than the gain of the voltage amplifier 105. The voltage signal V4 shown in FIG.

  Here, the voltage signal V4 is represented by the following equation (2).

V4 = exp (−t / τ8) (2)
τ8: Time constant corresponding to the low cut-off frequency fc8 of the low-frequency cut filter 108 t: Elapsed time when the time when the voltage signal V1 rises is set to 0 Note that the voltage signal V1 is t = 0 This is an expression that expresses from before rising to before falling, and the gain at the voltage amplifier 109 is not taken into consideration.

  Subsequently, the voltage signal V3 output from the voltage amplifier 107 and the voltage signal V4 output from the voltage amplifier 109 are added by the adder 110 and output as the voltage signal V5. At this time, in the case of τ4 << τ6 (fc4 >> fc6), the low-frequency cutoff frequency fc8 of the low-frequency cut filter 108 is made equal to the low-frequency cutoff frequency fc6 of the low-frequency cut filter 106 (fc6 = fc8), and the voltage signal When V3 and the voltage signal V4 are added together, the time constant of the term on the right side of the expression (1) indicating the voltage signal V3 and the time constant of the expression (2) indicating the voltage signal V4 are both τ6 (= τ8). Therefore, the term on the right side of equation (1) and equation (2) can be offset.

  Therefore, if the gain of the voltage amplifier 109 is adjusted in accordance with the gains of the voltage amplifiers 105 and 107, a signal is generated in the right side of the expression (1) indicating the voltage signal V3, that is, in the reverse direction of the voltage signal V5. It becomes possible to remove components.

  Subsequently, the voltage signal V5 output from the adder 110 is compared with the threshold voltage + Vth and the threshold voltage −Vth by the binarization circuit 111, respectively. The binarization circuit 111 switches between a high level and a low level when the voltage signal V5 exceeds the threshold voltage + Vth, and changes between a high level and a low level when the voltage signal V5 exceeds the threshold voltage −Vth. To create a binary pulse signal.

  Since the voltage signal V5 has no signal generated in the reverse direction, the binarization circuit 111 can output a pulse signal (voltage pulse) corresponding to the received optical pulse signal without malfunction. As a result, a normal pulse signal is output from the output terminal 114.

  As described above, in the pulse communication receiving circuit 100, the pulse signal is created using only the edge of the optical pulse signal detected by the low frequency cut filter 104. Further, the output signal of the low frequency cut filter 104 is amplified by the voltage amplifier 105. Accordingly, when the pulse communication receiving circuit 100 is used in a communication system in which the amplitude level of the optical pulse signal changes significantly, such as an optical communication system, for example, pulse width distortion due to amplifier saturation when the intensity of the optical pulse signal is large It is possible to achieve both prevention of the above and ensuring the sensitivity when the intensity of the optical pulse signal is small.

  In addition, an offset voltage due to amplification is generated in the voltage signal V <b> 2 output from the voltage amplifier 105, but the offset voltage is removed by the low frequency cut filter 106. Further, the voltage signal V3 output from the voltage amplifier 107 includes a signal component generated in the reverse direction due to the two low-frequency removals, but the voltage signal V3 is added by the adder 110. Since the voltage signal V4 is added together, it is canceled out.

  That is, the low frequency cut filter 108 generates a signal having the same component as the signal component generated in the reverse direction by the two low frequency removals, thereby canceling the signal component generated in the reverse direction. As a result, when the binarization circuit 111 binarizes, the voltage signal V5 has no signal component generated in the reverse direction, so that it is possible to prevent malfunction.

  In the pulse communication receiving circuit 100 described above, the voltage amplifier 109 is provided. However, the configuration is not limited to this, and the voltage amplifier 109 may be omitted if the gains of the voltage amplifiers 105 and 107 are adjusted. . The voltage amplifier 107 can also be omitted. This makes it possible to reduce the size of the circuit and reduce the load in the production process.

  The low frequency cutoff filter fc6 of the low frequency cut filter 108 and the low frequency cutoff frequency fc8 of the low frequency cut filter 108 are not limited to the same setting. The frequency may be set slightly lower than the low-frequency cutoff frequency fc6 of the cut filter 106 (fc8 <fc6).

  In this case, since τ8> τ6, the result of adding the voltage signal V3 and the voltage signal V4 in the region of t> τ4 where the right term of the equation (1) is dominant does not cancel, but somewhat It becomes possible to take a positive value. In an actual device, it is difficult to completely match τ6 and τ8. Therefore, it is useful to suppress the generation of signals in the reverse direction by making τ8 slightly larger than τ6.

  Furthermore, even when the time constant of the signal component generated in the reverse direction (term on the right side of Equation (1)) changes due to the fluctuation of the waveform of the optical pulse signal or the characteristic of the amplifier, the waveform of fluctuation for a longer time. Since the correction is performed at, the change in the waveform after correction can be reduced.

  As is clear from equation (1), even if τ4 and τ6 are interchanged, the same equation is obtained. Therefore, the low frequency cutoff frequency fc4 of the low frequency cut filter 104 and the low frequency cutoff of the low frequency cut filter 106 are obtained. The frequency fc6 is not limited by the magnitude relationship.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  FIG. 5 is a circuit diagram showing a configuration example of the pulse communication receiving circuit 200 of the present embodiment.

  As shown in FIG. 5, the pulse communication receiving circuit 200 of the present embodiment includes a subtracter 201 in addition to the configuration of the pulse communication receiving circuit 100 of the first embodiment except for the adder 110. ing.

  The subtractor 201 subtracts (subtracts) the voltage level of the voltage signal output from the voltage amplifier 109 from the threshold voltage + Vth and threshold voltage −Vth supplied to the binarization circuit 111. The subtractor 201 receives the voltage signal output from the voltage amplifier 109 and is connected and inserted between the first fixed power source 112 and the second fixed power source 113 and the ground.

  FIG. 6 is a diagram illustrating each signal waveform of the pulse communication receiving circuit 200.

  In the pulse communication receiving circuit 100 shown in FIG. 1, the voltage signal V3 supplied to the binarization circuit 111 is added with the voltage signal V4 to eliminate a signal generated in the reverse direction, thereby preventing malfunction. In the pulse communication receiving circuit 200 shown in FIG. 5, the voltage signal V3 output from the voltage amplifier 107 is directly input to the binarization circuit 111, while the voltage signal from the threshold voltage supplied to the binarization circuit 111 is obtained. By subtracting the voltage level of V4, malfunction is prevented.

  That is, by providing the subtractor 201, the threshold voltage + Vth and the threshold voltage −Vth obtained by subtracting the voltage level of the voltage signal V4 are supplied to the binarization circuit 111 as shown in FIG.

  Here, the voltage signal V4 is attenuated according to the attenuation characteristic at the low cut-off frequency fc8. The signal component generated in the reverse direction of the voltage signal V3 is attenuated according to the attenuation characteristic at the low-frequency cutoff frequency fc6. Therefore, if fc6 = fc8, the threshold voltage applied to the binarization circuit 111 changes following the signal component in the reverse direction of the voltage signal V3.

  Therefore, even if the voltage signal V3 has a signal component generated in the reverse direction, the signal component generated in the reverse direction does not exceed the threshold voltage as shown in FIG. Therefore, when the binarization circuit 111 binarizes, the voltage signal to be compared with the threshold value is equal to the absence of a signal component generated in the reverse direction, so that malfunction can be prevented.

  In order to ensure the effect of the pulse communication receiving circuit 200, the low-frequency cutoff frequency fc8 of the low-frequency cut filter 108 is made equal to the low-frequency cutoff frequency fc6 of the low-frequency cut filter 106, or the ratio is accurately set. It is important to keep on. Therefore, it is desirable that the low-frequency cut filters 104, 106, and 108 are composed of elements made in the same manufacturing process.

  For example, in the configuration shown in FIG. 3, it is preferable to use elements created in the same manufacturing process as the capacitor 152 and the resistor 153. In the configuration shown in FIG. 4, a capacitor created in the same manufacturing process is used as the capacitor 164, and a current source having the same characteristics generated from one current source circuit is used as the constant current source 163. It is preferable to use it.

  As a result, even if the absolute value of the time constant “CR” or the time constant “Vt · C / i” shifts due to variations in the manufacturing process, the relative shift of the low-frequency cutoff frequency is minimized. The time constants can be matched or the magnitude relationship can be maintained. For example, the low-frequency cutoff frequency fc8 can be made equal to the low-frequency cutoff frequency fc6 or the ratio can be kept accurate regardless of variations in the absolute value of the low-frequency cutoff frequency fc6.

[Embodiment 3]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first and second embodiments. For convenience of explanation, members having the same functions as those shown in the drawings of Embodiments 1 and 2 are given the same reference numerals, and explanation thereof is omitted.

  FIG. 7 is a circuit diagram illustrating a configuration example of the communication device 300 according to the present embodiment.

  The communication device 300 is an electronic device having a function applicable to a wireless communication system such as infrared communication or a wired communication system using an optical fiber cable, for example, a mobile phone that performs optical communication, a remote controller, and infrared communication. TV.

  As illustrated in FIG. 7, the communication device 300 includes a pulse communication reception circuit 301 and a data conversion circuit 302. The remaining part (not shown) of the communication device 300 can be realized by a conventional general configuration corresponding to the application. For example, a CPU, an application processor, and the like (not shown) are provided in the subsequent stage of the data conversion circuit 302.

  The pulse communication receiving circuit 301 is the pulse communication receiving circuit 100 shown in FIG. 1 or the pulse communication receiving circuit 200 shown in FIG. When the photodiode 101 receives an optical pulse signal transmitted from a transmitter (not shown), the pulse communication reception circuit 301 creates a pulse signal corresponding to the received optical pulse signal without malfunction, and outputs the output terminal 114. Output from.

  The data conversion circuit 302 converts the pulse signal output from the pulse communication reception circuit 301 into data. Various conventional methods can be suitably used as the conversion method. The data is output to a CPU, an application processor, or the like and processed, whereby communication is successful.

  As described above, in the communication device 300, the pulse communication reception circuit 301 creates a normal pulse signal according to the width of the received optical pulse signal. It is possible to expect an improvement in sensitivity. This is particularly useful for improving the communication distance in infrared communication.

  Furthermore, when used in a wireless communication system such as optical communication, a pulse signal can be suitably created even if the signal level input to the photodiode 101 has a large range.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used not only in a field related to a receiving circuit that creates a pulse signal in response to an optical pulse signal received via wireless communication or wired communication, but also preferably in a field related to a method for manufacturing a receiving circuit. Further, it can be widely used in the field of telecommunication equipment including a receiving circuit, for example, a portable device that performs optical communication and a receiver that performs infrared communication with a remote controller.

It is a circuit diagram which shows one Embodiment of the pulse communication receiver circuit in this invention. It is a figure which shows each signal waveform of the said pulse communication receiving circuit. It is a circuit diagram which shows one structural example of the low frequency cut filter in the said pulse communication receiving circuit. It is a circuit diagram which shows the other structural example of the low frequency cut filter in the said pulse communication receiving circuit. It is a circuit diagram which shows other embodiment of the pulse communication receiver circuit in this invention. It is a figure which shows each signal waveform of the said pulse communication receiving circuit. It is a circuit diagram which shows one Embodiment of the electronic device in this invention. It is a figure which shows each signal waveform when producing | generating a reception pulse using the pulse edge detection in the past. It is a figure which shows each signal waveform when malfunctioning generate | occur | produces when producing | generating a reception pulse using the pulse edge detection in the past.

Explanation of symbols

100, 200 Pulse communication receiving circuit 101 Photo diode 102 First stage amplifier (second amplifier)
103 High-frequency cutoff amplifier (third amplifier)
104 Low-frequency cut filter (first filter circuit)
105 Voltage amplifier (first amplifier)
106 Low frequency cut filter (second filter circuit)
107 voltage amplifier 108 low frequency cut filter (third filter circuit)
109 Voltage Amplifier 110 Adder 111 Binary Circuit 112 First Fixed Power Supply 113 Second Fixed Power Supply 114 Output Terminal 152 Capacitor (Capacitance Element)
153 Resistance 162 Bipolar transistor 163 Constant current source (current source)
164 Capacitor (capacitance element)
201 Subtractor 300 Communication equipment (electronic equipment)
301 pulse communication receiving circuit 302 data conversion circuit

Claims (13)

A first filter circuit that removes a low-frequency component of an input signal based on a first low-frequency cutoff frequency; a first amplifier that amplifies the signal from which the low-frequency component has been removed by the first filter circuit; and the first amplifier. A second filter circuit that removes a low-frequency component of the signal amplified by step (b) based on the second low-frequency cutoff frequency, and a binary value obtained by comparing the signal from which the low-frequency component has been removed by the second filter circuit with a threshold value. A pulse communication receiving circuit comprising a binarization circuit for creating a digitized pulse signal,
A third filter circuit for removing a low-frequency component of the input signal based on a third low-frequency cutoff frequency;
The signal from which the low frequency component has been removed by the third filter circuit is added to the signal from which the low frequency component has been removed by the second filter circuit supplied to the binarization circuit. Pulse communication receiver circuit. A first filter circuit that removes a low-frequency component of an input signal based on a first low-frequency cutoff frequency; a first amplifier that amplifies the signal from which the low-frequency component has been removed by the first filter circuit; and the first amplifier. A second filter circuit that removes a low-frequency component of the signal amplified by step (b) based on the second low-frequency cutoff frequency, and a binary value obtained by comparing the signal from which the low-frequency component has been removed by the second filter circuit with a threshold value. A pulse communication receiving circuit comprising a binarization circuit for creating a digitized pulse signal,
A third filter circuit for removing a low-frequency component of the input signal based on a third low-frequency cutoff frequency;
The pulse communication receiving circuit, wherein the voltage level of the signal from which the low frequency component is removed by the third filter circuit is subtracted from the threshold voltage level used by the binarization circuit. A second amplifier for amplifying the input signal;
3. The pulse communication receiving circuit according to claim 1, wherein the signal amplified by the second amplifier is supplied to the first filter circuit and the third filter circuit. 4.   A DC component and a low frequency component of the output signal of the second amplifier, the input terminal of which is connected to the output terminal of the second amplifier and the output terminal of which is connected to the input terminal of the second amplifier. The pulse communication receiving circuit according to claim 3, further comprising a third amplifier that extracts and amplifies the signal based on the signal.   5. The pulse communication receiving circuit according to claim 4, wherein a high-frequency cutoff frequency of the third amplifier is set to a frequency that is lower by one digit or more than a frequency of the input signal.   The high-frequency cutoff frequency of the third amplifier is a frequency one digit or more lower than the lower one of the first low-frequency cutoff frequency of the first filter circuit and the second low-frequency cutoff frequency of the second filter circuit. The pulse communication receiving circuit according to claim 4, wherein the pulse communication receiving circuit is set.   3. The pulse communication receiving circuit according to claim 1, wherein the signal from which the low frequency component has been removed by the second filter circuit is amplified.   3. The pulse communication receiving circuit according to claim 1, wherein the signal from which the low frequency component has been removed by the third filter circuit is amplified.   The third low frequency cutoff frequency of the third filter circuit is set to the same frequency as the lower one of the first low frequency cutoff frequency of the first filter circuit and the second low frequency cutoff frequency of the second filter circuit. The pulse communication receiver circuit according to claim 1, wherein the pulse communication receiver circuit is provided.   The third low frequency cutoff frequency of the third filter circuit is lower than the lower one of the first low frequency cutoff frequency of the first filter circuit and the second low frequency cutoff frequency of the second filter circuit. The pulse communication receiving circuit according to claim 1, wherein the pulse communication receiving circuit is set.   In the first filter circuit, the second filter circuit, and the third filter circuit, elements for setting the respective low-frequency cutoff frequencies are configured by capacitive elements and resistors created in the same manufacturing process. The pulse communication receiving circuit according to claim 1 or 2.   In the first filter circuit, the second filter circuit, and the third filter circuit, elements for setting the respective low-frequency cutoff frequencies are generated from a capacitive element created in the same manufacturing process and one current source circuit. The pulse communication receiving circuit according to claim 1, wherein the pulse communication receiving circuit comprises a current source having the same characteristics. Has a wireless or wired communication function,
An electronic apparatus comprising the pulse communication receiving circuit according to claim 1.

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