JP2013005326A - Amplifier circuit - Google Patents

Amplifier circuit Download PDF

Info

Publication number
JP2013005326A
JP2013005326A JP2011136303A JP2011136303A JP2013005326A JP 2013005326 A JP2013005326 A JP 2013005326A JP 2011136303 A JP2011136303 A JP 2011136303A JP 2011136303 A JP2011136303 A JP 2011136303A JP 2013005326 A JP2013005326 A JP 2013005326A
Authority
JP
Japan
Prior art keywords
stage amplifier
signal
component
circuit
amplifier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2011136303A
Other languages
Japanese (ja)
Inventor
Takao Nakagawa
隆夫 中川
Original Assignee
Seiwa Electric Mfg Co Ltd
星和電機株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Seiwa Electric Mfg Co Ltd, 星和電機株式会社 filed Critical Seiwa Electric Mfg Co Ltd
Priority to JP2011136303A priority Critical patent/JP2013005326A/en
Publication of JP2013005326A publication Critical patent/JP2013005326A/en
Pending legal-status Critical Current

Links

Images

Abstract

In an amplifier circuit having a first stage amplifier for amplifying an output signal of a light receiving element (photodiode), an amplification factor of the first stage amplifier is increased.
A first-stage amplifier 31 extracts a DC component included in an output signal of a first-stage amplifier 31 that amplifies an electric signal photoelectrically converted by a photodiode 2 and cancels the extracted DC component. The bias current is fed back to the input side. By flowing a bias current to the input side of the first stage amplifier 31 in this way, a DC component (signal component such as illumination light) input to the first stage amplifier 31 can be removed, and the amplification of the first stage amplifier 31 is performed. It becomes possible to increase the rate.
[Selection] Figure 1

Description

  The present invention relates to an amplifier circuit used in a receiver that receives an optical modulation signal in visible light communication or the like.
  In recent years, a visible light communication system has been developed that performs data communication using visible light output from a light source such as an LED (light emitting diode).
  As an example of a visible light communication system, a transmitter that superimposes a light modulation signal on illumination light (visible light) by controlling blinking of a light source such as a lighting device according to transmission data, and transmits from this transmitter And a receiver that receives the visible light signal (light modulation signal) and demodulates the received light modulation signal to obtain communication data (see, for example, Patent Document 1). In such a visible light communication system or the like, a receiver that receives a light modulation signal includes a light receiving element (for example, a photodiode) that converts the light modulation signal into an electric signal, an amplification circuit that amplifies the output signal of the light receiving element, And a demodulating circuit for demodulating the received signal (see, for example, Patent Documents 2 to 4).
  An amplifier circuit used in this type of receiver includes, for example, a first-stage amplifier that amplifies an electrical signal (current signal) photoelectrically converted by a light receiving element, and an optical modulation signal (from the electrical signal amplified by the first-stage amplifier). A band-pass filter that extracts frequency components corresponding to communication data), and an AGC (Auto Gain Control) circuit that adjusts the gain of the electrical signal extracted by the band-pass filter to make the signal amplitude constant. Etc.
JP 2008-252465 A JP 2008-117206 A JP 2009-118180 A JP 2010-136167 A
  Incidentally, in the above-described amplifier circuit, the output of the first-stage amplifier that amplifies the electrical signal photoelectrically converted by the light receiving element includes two signal components such as a light modulation signal (communication data) and illumination light ( (See FIG. 4).
  Here, in this type of amplifier circuit, increasing the amplification factor with the first-stage amplifier can cope with reception of weak light modulation signals, for example, and can widen the dynamic range of reception of light modulation signals. It is advantageous in that it is. However, as described above, the output of the first stage amplifier includes two signal components, that is, a light modulation signal and illumination light. Therefore, if the amplification factor of the first stage amplifier is increased, the signal component of the illumination light (approximately DC) Component) is greatly amplified, and the output of the first stage amplifier is saturated. For this reason, the amplification factor of the first stage amplifier cannot be increased.
  The present invention has been made in consideration of such a situation, and in an amplifier circuit having a first-stage amplifier that amplifies an electrical signal photoelectrically converted by a light receiving element, a configuration capable of increasing the amplification factor of the first-stage amplifier. It aims to be realized.
  The present invention is an amplifying circuit that is applied to a light receiving element that converts an optical signal into an electric signal and outputs the electric signal, and has an initial stage amplifier that amplifies the electric signal output from the light receiving element, and the electric signal output from the first stage amplifier A DC component detecting means (for example, a low-pass filter) for detecting a DC component included in the signal, and a bias means for feeding back a bias current to the input side of the first-stage amplifier so as to cancel the DC component. Characteristic.
  According to the present invention, since a bias current that cancels the DC component (makes the DC component zero) flows on the input side of the first-stage amplifier, the DC component included in the electrical signal output from the first-stage amplifier, that is, the illumination light Etc. can be removed. As a result, the amplification factor of the first stage amplifier can be increased.
  In the present invention, as an example of a DC component detecting means for detecting a DC component included in an electrical signal output from the first stage amplifier, only a DC component included in the electrical signal output from the first stage amplifier is extracted from a resistor and a capacitor. A low pass filter can be mentioned. When such a low-pass filter is used, a direct current component can be detected with a simple circuit configuration.
  According to the present invention, in the amplifier circuit having the first stage amplifier that amplifies the electric signal output from the light receiving element, the amplification factor of the first stage amplifier can be increased.
It is a block diagram which shows an example of the receiver provided with the amplifier circuit to which this invention is applied. It is a figure which shows an example of a low-pass filter. It is a block diagram which shows an example of the transmitter which comprises an optical communication system. It is a wave form diagram of the output signal (signal containing a direct-current component) of the first stage amplifier which amplifies the output signal of a photodiode.
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
  In this embodiment, an example in which the present invention is applied to an amplifier circuit provided in a receiver in an optical communication system including a transmitter and a receiver that perform data communication by visible light communication will be described.
  First, an example of the transmitter 100 configuring the optical communication system will be described with reference to FIG. The transmitter 100 in this example includes a modulation circuit 101, an LED drive circuit 102, an LED (light emitting diode) 103 that is a light source of a lighting device, and the like.
  The modulation circuit 101 modulates communication data (data superimposed on the illumination light) and outputs the modulated communication data to the LED drive circuit 102. The signal modulation method of the modulation circuit 101 may be a modulation method generally used in optical communication or the like. For example, an ASK method (Amplitude Shift Keying) method or a PPM (Pulse Position Modulation) method is used. ) Method. In addition, an orthogonal modulation / demodulation method such as a QPSK (quadture phase shift keying) method may be used.
  The LED drive circuit 102 blinks the LED 103 at high speed based on the modulation data modulated by the modulation circuit 101. As a result, a light modulation signal (communication data) is output superimposed on the illumination light. The output optical modulation signal is received by the receiver 1.
-Receiver-
Next, the receiver 1 will be described with reference to FIG.
  The receiver 1 receives a light modulation signal (communication data) output from the transmitter 100 and converts the light modulation signal into an electrical signal (current signal) 2. The photodiode 2 Are provided with an amplification circuit 3 for amplifying the electric signal photoelectrically converted in (4) and a demodulation circuit 4 for demodulating the electric signal (light modulation signal) that has passed through the amplification circuit 3.
  The amplifier circuit 3 includes a first stage amplifier (photodiode light receiving circuit) 31, a band pass filter 32, a variable gain amplifier 33, a low pass filter 34, an AD converter 35, a processing control unit 36, a bias circuit 37, and the like.
  The first stage amplifier 31 is an amplifier (IV converter) composed of an operational amplifier 31a and a feedback resistor 31b, and amplifies the electrical signal photoelectrically converted by the photodiode 2. The electric signal amplified by the first stage amplifier 31 is input to the band pass filter 32.
  Since the first stage amplifier (IV conversion circuit) 31 is an inverting amplifier circuit using the operational amplifier 31a, the output voltage V of the operational amplifier 31a is [V = −Ipd × R Ipd: the output current R of the photodiode 2 R: Resistance value of the feedback resistor 31b], and a direct current component (see FIG. 4) described later has a negative value.
  The bandpass filter 32 is, for example, a filter having a three-stage Butterworth characteristic (amplitude flatness characteristic), and removes a noise component included in the electric signal output from the first-stage amplifier 31 to provide an optical modulation signal (communication data). Extract only. The gain of the optical modulation signal extracted by the bandpass filter 32 is adjusted by the variable gain amplifier 33. The variable gain amplifier 33 is A / D converted by the AD converter 35 and then input to the processing control unit 36.
  The processing control unit 36 performs predetermined signal processing on the optical modulation signal (communication data) extracted by the bandpass filter 32 and passed through the variable gain amplifier 33 and the AD converter 35 and outputs the result to the demodulation circuit 4. Specifically, the optical modulation signal is sampled by the AD converter 35 at a frequency higher than twice that of the optical modulation signal, and the optical modulation signal is converted into a digital signal (sampling theorem). Next, the converted data is passed through a moving average filter to remove noise and output to the demodulation circuit 4. The demodulating circuit 4 demodulates the optical modulation signal from the processing control unit 36 to obtain communication data.
  In addition, the process control unit 36 adjusts the amplification factor of the variable gain amplifier 33 so that the output value (AD value) of the AD converter 35 falls within a preset specified range. By such AGC gain control, the amplitude of the signal that has passed through the bandpass filter 32 can be made uniform.
  Further, the processing control unit 36 outputs a bias signal (digital signal) for canceling a DC component described later to the bias circuit 37 based on the signal (after A / D conversion) extracted by the low-pass filter 34. .
-Feature part-
Next, the characteristic part of this embodiment is demonstrated.
  First, when the amplifier circuit 3 shown in FIG. 1 does not include the features of the present embodiment (such as the low-pass filter 34 and the bias circuit 37), the output signal of the first stage amplifier 31 has a waveform as shown in FIG. As can be seen from FIG. 4, the output signal of the first-stage amplifier 31 includes an optical modulation signal (communication data) and two signal components such as illumination light. For this reason, the amplification factor of the first stage amplifier 31 cannot be increased. That is, when the amplification factor of the first stage amplifier 31 is increased, the signal component (substantially a direct current component) such as illumination light is also greatly amplified, and the output of the first stage amplifier 31 is saturated.
  In consideration of such points, in this embodiment, a DC component included in the output signal of the first-stage amplifier 31 is extracted, and a bias current is fed back to the input side of the first-stage amplifier 31 so as to cancel this DC component. The direct current component of the electric signal input to the first stage amplifier 31 is removed. The specific configuration will be described below.
  First, in the present embodiment, as shown in FIG. 1, a low-pass filter 34 that removes a light modulation signal (communication data) included in the output signal of the first-stage amplifier 31 and extracts a DC component (signal component such as illumination light). And a bias circuit 37 composed of a DA converter 37a and a resistor 37b. An output terminal (resistor 37b) of the bias circuit 37 is connected to the input side of the first stage amplifier 31 (between the photodiode 2 and the first stage amplifier 31). ) Is connected.
  The DC component extracted by the low-pass filter 34 is A / D converted by the AD converter 35 and then input to the processing control unit 36. The processing control unit 36 temporarily stores the DC component (digital signal after A / D conversion) extracted by the low-pass filter 34, and cancels the DC component (DC component becomes zero). Signal) to the bias circuit 37. In the bias circuit 37, the bias signal (digital signal) from the processing control unit 36 is converted into an analog signal (bias current) by the DA converter 37a, and is fed back to the upstream side of the first stage amplifier 31 through the resistor 37b.
  In this way, by supplying a bias current that cancels the DC component to the input side of the first-stage amplifier 31, the DC component (signal component such as illumination light) of the electrical signal input to the first-stage amplifier 31 can be removed. The amplification factor of the first stage amplifier 31 can be increased. Thereby, for example, a weak light modulation signal can be received, and the dynamic range of reception of the light modulation signal can be expanded.
  Here, for example, each time the transmission data from the transmitter 100 is received, the processing control unit 36 captures (temporarily stores) the DC component included in the output signal of the first-stage amplifier 31, and the DC component. So as to cancel the operation, an operation of outputting a bias signal to the bias circuit 37 (an operation of supplying a bias current to the input side of the first-stage amplifier 31) may be sequentially repeated.
  The bias means of the present invention is realized by the processing control unit 36 and the bias circuit 37 described above.
-Low-pass filter-
Next, an example of the low-pass filter 34 used in the present embodiment will be described with reference to FIG. The low-pass filter 34 shown in FIG. 2 is a filter having a simple circuit configuration including one resistor 34a and one capacitor 34b.
  The low-pass filter 34 used in the present embodiment is intended to extract only the DC component of the electrical signal output from the first stage amplifier 3 as described above, and therefore the cut-off frequency fc is set to a small value. For example, in this example, the resistance value R of the resistor 34a shown in FIG. ] Is set.
  When such a low-pass filter 34 is used, the light modulation signal (communication data) included in the output signal of the first-stage amplifier 31 is removed and only the DC component (signal component such as fluorescent lamp light) is extracted with a simple circuit configuration. (Detection) becomes possible.
-Other embodiments-
In the above embodiment, the low-pass filter 34 is used as means for detecting the DC component included in the output signal of the first-stage amplifier 31, but the present invention is not limited to this and is included in the output signal of the first-stage amplifier 31. Any other circuit configuration detection means may be used as long as it can detect the direct current component.
  In the above embodiment, an optical communication system for one-way communication including the transmitter 100 having the modulation circuit 101, the LED 103, and the like, and the receiver 1 having the photodiode 2, the amplification circuit 3, the demodulation circuit 4, and the like is taken as an example. Although described above, the present invention is not limited to this, and light for bidirectional communication in which both the transmission side and the reception side are provided with an LED drive circuit system (modulation circuit, etc.) and a light reception circuit system (demodulation circuit, etc.). The present invention can also be applied to an amplifier circuit used in a communication system.
  In the above embodiment, the visible light communication system that performs data communication using the visible light output from the LED has been described as an example. However, the present invention is not limited thereto, for example, a discharge lamp such as a fluorescent lamp, The present invention is also applicable to an amplifier circuit used in a visible light communication system that performs data communication using visible light output from a light source such as an organic EL or an inorganic EL.
  INDUSTRIAL APPLICABILITY The present invention can be used for an amplifier circuit used in a receiver that receives an optical modulation signal in visible light communication or the like, and more specifically, an amplifier circuit having a first-stage amplifier that amplifies an electric signal photoelectrically converted by a light receiving element. Therefore, it can be effectively used for a technique for increasing the amplification factor of the first stage amplifier.
1 Receiver 2 Photodiode (light receiving element)
DESCRIPTION OF SYMBOLS 3 Amplifier circuit 31 First stage amplifier 31a Operational amplifier 31b Feedback resistor 32 Band pass filter 33 Variable gain amplifier 34 Low pass filter (DC component detection means)
35 AD converter 36 Processing control unit 37 Bias circuit 37a DA converter 37b Resistor 4 Demodulator circuit 100 Transmitter 101 Modulator circuit 102 LED drive circuit 103 LED

Claims (2)

  1. An amplification circuit that is applied to a light receiving element that converts an optical signal into an electric signal and outputs the electric signal, and that has an initial stage amplifier that amplifies the electric signal output from the light receiving element,
    DC component detection means for detecting a DC component included in an electrical signal output from the first stage amplifier, and bias means for feeding back a bias current to the input side of the first stage amplifier so as to cancel the DC component. An amplifier circuit characterized by the above.
  2. The amplifier circuit according to claim 1,
    2. The amplifier circuit according to claim 1, wherein the DC component detecting means is a low-pass filter that includes a resistor and a capacitor and extracts only a DC component contained in an electric signal output from the first-stage amplifier.
JP2011136303A 2011-06-20 2011-06-20 Amplifier circuit Pending JP2013005326A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2011136303A JP2013005326A (en) 2011-06-20 2011-06-20 Amplifier circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2011136303A JP2013005326A (en) 2011-06-20 2011-06-20 Amplifier circuit

Publications (1)

Publication Number Publication Date
JP2013005326A true JP2013005326A (en) 2013-01-07

Family

ID=47673383

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2011136303A Pending JP2013005326A (en) 2011-06-20 2011-06-20 Amplifier circuit

Country Status (1)

Country Link
JP (1) JP2013005326A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015081162A (en) * 2013-10-22 2015-04-27 モリテックスチール株式会社 Storage body for long object
CN106059640A (en) * 2016-06-30 2016-10-26 东南大学 Design method of transmitting terminal of VLC (Visible Light Communication) secure communication system based on QoS (Quality of Service)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10135746A (en) * 1996-10-31 1998-05-22 Sharp Corp Light receiving circuit for optical free-space transmission
JPH10290024A (en) * 1997-04-11 1998-10-27 Seiko Instr Inc Light emitting detecting circuit
JPH1141301A (en) * 1997-05-23 1999-02-12 Fuji Xerox Co Ltd Optical signal transmission method and device therefor and optical signal receiving device and method for adjusting the same
JP2007028264A (en) * 2005-07-19 2007-02-01 Stanley Electric Co Ltd Optical communication device
JP2010226627A (en) * 2009-03-25 2010-10-07 Nec Corp Burst signal identifier, burst light receiver, burst signal identifying method and burst light receiving method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10135746A (en) * 1996-10-31 1998-05-22 Sharp Corp Light receiving circuit for optical free-space transmission
JPH10290024A (en) * 1997-04-11 1998-10-27 Seiko Instr Inc Light emitting detecting circuit
JPH1141301A (en) * 1997-05-23 1999-02-12 Fuji Xerox Co Ltd Optical signal transmission method and device therefor and optical signal receiving device and method for adjusting the same
JP2007028264A (en) * 2005-07-19 2007-02-01 Stanley Electric Co Ltd Optical communication device
JP2010226627A (en) * 2009-03-25 2010-10-07 Nec Corp Burst signal identifier, burst light receiver, burst signal identifying method and burst light receiving method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015081162A (en) * 2013-10-22 2015-04-27 モリテックスチール株式会社 Storage body for long object
CN106059640A (en) * 2016-06-30 2016-10-26 东南大学 Design method of transmitting terminal of VLC (Visible Light Communication) secure communication system based on QoS (Quality of Service)

Similar Documents

Publication Publication Date Title
AU2010286576B2 (en) Power line communications apparatus
US7953328B2 (en) Optical DQPSK transmitter phase monitor and control
EP1913713B1 (en) Phase monitor apparatus, phase control apparatus and methods thereof for optical dqpsk receiver
US9325361B2 (en) Receiver system
JP4440855B2 (en) RZ-DPSK optical receiver circuit
US7295073B2 (en) Automatic gain control apparatus
Căilean et al. Novel receiver sensor for visible light communications in automotive applications
KR100900205B1 (en) Wide dynamic range transimpedance amplifier
FI102991B (en) Electronic arrangement for receiving a modulated carrier signal
JP4935422B2 (en) Preamplifier and optical receiver using the same
CN104485993B (en) Vehicular visible light wireless digital voice communication system
US6774728B2 (en) Transimpedance amplifier
DE19882819B4 (en) Optical receiving device
US7212747B2 (en) Optical transmission device and optical transmission method for transmitting a burst radio signal
JP3434806B2 (en) Receiver for processing an input data signal in an optical network system and method for determining a data transmission rate of an input data signal in an optical network
US20090212926A1 (en) Baby Monitor
EP1764935A3 (en) Optical transmission system
TWI294210B (en) System,apparatus and method for data communication
EP1617578A4 (en) Optical receiver and optical transmission system
WO2007120403A2 (en) Feedback-controlled coherent optical receiver with electrical compensation/equalization
JP2015536627A5 (en)
TWI573411B (en) Circuit, module and method of closed loop optical modulation amplitude control
KR20100081996A (en) I/q calibration techniques
CN101335503B (en) Preamplifier and light receiving device
JP2005159553A (en) Dispersion compensating method, wdm optical transmission system, optical transmission system, and optical transmission apparatus

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20130401

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20140218

A02 Decision of refusal

Free format text: JAPANESE INTERMEDIATE CODE: A02

Effective date: 20140624