CN105610502A - Special visible light communication based integrated circuit for receiver - Google Patents

Abstract

The invention relates to a special visible light communication based integrated circuit for a receiver, which comprises a trans-impedance amplifier and a limiting amplifier, wherein the trans-impedance amplifier and the limiting amplifier are sequentially connected; the trans-impedance amplifier is used for converting an obtained current signal into a voltage signal and carrying out amplification; the limiting amplifier is used for amplifying the voltage signal output by the trans-impedance amplifier to a digital voltage level; an input end of the trans-impedance amplifier is connected with an output end of a front balancing unit for carrying out compensation on a current received from a photodiode; an output end of the limiting amplifier is connected with an input end of a rear balancing unit for carrying out secondary compensation on a voltage signal output from the limiting amplifier; an output end of the rear balancing unit is connected with an input end of a comparator for signal decision; and an output of the comparator forms an output of the special visible light communication based integrated circuit for the receiver. According to the special visible light communication based integrated circuit for the receiver, which is disclosed by the invention, the volume is effectively reduced and an error brought in when each module is cascaded is reduced. The special visible light communication based integrated circuit for the receiver has the advantages of low power consumption, high integration level, low cost, easiness for large-scale production and the like.

Description

A kind of receiver special IC based on visible light communication

Technical field

The present invention relates to a kind of integrated circuit. Particularly relate to the special integrated electric of a kind of receiver based on visible light communicationRoad.

Background technology

In recent years, along with the high speed development of electronics technology, the total number of users of smart machine and popularity rate significantly increase year by yearAdd, what increase is the demands of people to high-speed wideband multimedia communication thereupon. Now conventional radio frequency communication occurs that frequency spectrum resource is tightSituation, the limitation of the factor such as electromagnetic interference, and people's pay attention to day by day radiation is in addition on healthy impact, shortHaving made to produce a kind of resource that can widen frequency spectrum, is the communication mode of transmission base station by the LED lamp of green energy conservation---canSee optic communication. In recent years, be accompanied by the development of white light LEDs technology, the potentiality that VLC technology is applied to various scenes start to show,Obtain paying close attention to more and more widely both at home and abroad.

Compare infrared radio optical communication system, the light that in VLC system, white light LEDs sends, to eye-safe, is therefore launched meritRate can be very high, but because the light-emitting mode of LED is followed lambert's divergent mode, from light source compared with distant location, even if having higherTransmitting power, light intensity is still very weak. VLC system is designed to light intensity modulation, direct-detection system (Intensity mostlyModulation/directdetection, IM/DD), the power of the optical signal that receiver photoelectricity testing part receives will be straightCan connect decision whole system work normally. High Speed Modulation that what simultaneously LED sent only pass through, the bandwidth of receiver and soundAnswer speed to match with modulation signal light source. Therefore, design and meet performance requirement and the lower reception of costMachine is the key that visible light communication technology is able to extensive use.

The research of receiver in visible light communication was just being risen over the past two years. Aspect design technology, adopt in the past moreRealize with GaAs or bipolarity silicon technology, but they have the shortcoming that cost is high, power consumption is large, integrated level is low. In addition, due toReceiving device property difference is larger, and the contained module of entire system structure is more, between influence each other comparatively complicated, existing researchBe mainly the research based on its feasibility aspect, it is all also that commercial discrete device is with practical function that receiver is built used. CauseThis, be designed for the overall independent receivers special IC of visible light communication system in innovation development, this aspectAlso rarely has report.

Summary of the invention

Technical problem to be solved by this invention is, effectively reduced volume while reducing each module-cascade of one is providedBring the receiver special IC based on visible light communication of error into.

The technical solution adopted in the present invention is: a kind of receiver special IC based on visible light communication, comprisesHave successively connect for the current signal obtaining being converted into voltage signal the trans-impedance amplifier amplifying and for willThe voltage signal of trans-impedance amplifier output is amplified to the limiting amplifier of digital voltage level, the input of described trans-impedance amplifierConnect the output for balanced unit the electric current receiving from photodiode is compensated, described limiting amplifierOutput connect for to the input that carries out the post-equalization unit of second compensation from the voltage signal of limiting amplifier output,The output of described post-equalization unit connects the input as the comparator of signal decision, and the output of described comparator forms baseIn the output of the receiver special IC of visible light communication.

Described front balanced unit includes: the current source being in parallel and the first electric capacity, described current source and the first electric capacityOne end connect voltage VDD, described current source and the other end of the first electric capacity be connected respectively the first resistance one end, inductance oneThe grid of end and a NMOS pipe, the other end of described inductance is by the second resistance eutral grounding, the other end of described the first resistanceJointly be connected the source electrode of the 2nd NMOS pipe with the drain electrode of a NMOS pipe, this end of the first resistance and the drain electrode of a NMOS pipe withAnd the source electrode of the 2nd NMOS pipe also forms the input of the output connection trans-impedance amplifier of front balanced unit, described second jointlyThe drain electrode of NMOS pipe connects voltage VDD, and grid connects voltage VDD by the 3rd resistance.

Described post-equalization unit includes the second electric capacity and the 4th resistance, described the second electric capacity and the 4th electricity that are in parallelThe common output that connects described limiting amplifier in one end of resistance, the other end of described the second electric capacity and the 4th resistance is by oneLoad resistance ground connection, output that described the second electric capacity and this end of the 4th resistance also form post-equalization unit is connected comparatorInput.

A kind of receiver special IC based on visible light communication of the present invention, by new system topology,Before using, balanced and post-equalization skill upgrading bandwidth, in a slice, has dwindled volume by photoreceiver over all Integration effectively simultaneouslyAnd the error of bringing into while having reduced each module-cascade. The CMOS technique monolithic of entirety employing standard is integrated, realizes at visible ray lightAccording to the receiver function of high-speed data under environment, there is low-power consumption, integrated level is high, cost is low, be easy to large-scale production etc. simultaneouslyAdvantage. Tool of the present invention has the following advantages:

1. the visible light communication technology based on emerging, has realized the data receiver function under visible ray environment, with traditionalTechnology for radio frequency is compared, and has applicability wide, anti-interference strong security, and the advantage such as electromagnetic-radiation-free is harmless, in dangerDanger product are deposited with Code in Hazardous Special Locations Articles detecting aspect many advantages.

2. visible ray receiver chip. Use comparatively ripe CMOS technique to manufacture, replace existing each several partDiscrete device system architecture, has realized Highgrade integration, reduces volume, has reduced cost. Establish for researching and developing miniature visible ray detectionStandby and spread provides may.

3. in circuit structure, added front equilibrium and post-equalization circuit structure simultaneously, the overall bandwidth of receiver is obtainedLifting, improved the information data transmission ability of receiver. For overall visible light communication integrated system is carried out large dataTransmission provides the foundation.

4. this circuit adopts the design of low-power consumption, effectively controls the energy consumption of overall photoreceiver chip, with existingReceiver is compared only needs to provide the energy of milliwatt rank just can work, and has improved the continuous firing ability of receiving system, significantlyAlleviate the energy resource consumption problem in practice.

In sum, the present invention proposes receiver integrated circuit structure special and implementation method based on visible light communicationHave a good application prospect.

Brief description of the drawings

Fig. 1 is the structural representation of the present invention in the application of visible ray receiving terminal system;

Fig. 2 is that the receiver special IC that the present invention is based on visible light communication forms block diagram;

Fig. 3 a is the circuit theory diagrams of front balanced unit in the present invention;

Fig. 3 b is the equivalent circuit of shunt-resonant circuit in the front balanced unit of the present invention;

Fig. 3 c is RLC network equivalent circuit diagram in the front balanced unit of the present invention;

Fig. 4 is the circuit theory diagrams of post-equalization unit in the present invention.

In figure

1: blue color filtered sheet 2: IC chip

3: digital end or oscillograph 21: front balanced unit

22: trans-impedance amplifier 23: limiting amplifier

24: post-equalization unit 25: comparator

Detailed description of the invention

Below in conjunction with implementation process and accompanying drawing to the special integrated electric of a kind of receiver based on visible light communication of the present inventionRoad is described in detail.

Fig. 1 has provided the applied visible ray receiving terminal system of the present invention structural representation. Use as shown in Figure 1 silicon PINPhotodiode PD, as visible-light detector, sees through blue by the visible ray that is loaded with 0/1 signal of front end white light LEDs transmittingFilter plate 1 is converted into current signal, then will by the receiver dedicated IC chip 2 based on visible light communication of the present inventionThis Weak current signal is converted into the voltage signal of digital voltage level.

As shown in Figure 2, a kind of receiver special IC based on visible light communication of the present invention, includes successively and connectsConnect for the trans-impedance amplifier 22 that the current signal obtaining is converted into voltage signal and amplify with for putting across resistanceThe large very little voltage signal of device 22 output amplitudes is amplified to the limiting amplifier 23 of digital voltage level, described trans-impedance amplifier 22Input connect for the output of balanced unit 21 electric current receiving from photodiode PD is compensated, instituteState limiting amplifier 23 output connect for the voltage signal of exporting from limiting amplifier 23 is carried out second compensationThe input of balanced unit 24, the output of described post-equalization unit 24 connects the input as the comparator 25 of signal decisionEnd, the output that the output of described comparator 25 forms the receiver special IC based on visible light communication is connected to numeralEnd modulation or connection oscillograph 3.

Received visible light signal flows out from PIN photodiode PD with faint current forms, through front equilibriumThe compensation of module enters in trans-impedance amplifier, is converted into voltage small-signal by electric current. Carry out through multistage limiting amplifier againSignal amplifies, and carries out second compensation by what obtain compared with long arc voltage signal through post-equalization. Due to detector self junction capacityOften relatively large, add the parasitic effects of circuit generations at different levels, the signal that now obtained has produced distortion, after being unfavorable forTerminal number word modules carries out modulation treatment, therefore after post-equalization, adds hysteresis comparator, and waveform is processed, and reaches adjustment rippleThe object of shape, makes to export the original signal that reverts to digital voltage level, completes the transmission object of visible light signal. Output alsoAccessible oscillograph carrys out the signal that observation station receives.

Front equilibrium refers to that the photoproduction input current signal producing at photodetector enters before transimpedance preamplifier, passes throughAdopt the means of compensation, improve the electric bandwidth of input signal, with the radio-frequency component in restoring signal, avoid high-frequency signal through amplifyingAfter circuit because losing excessive cannot recovery. It is real that front balance module in the present invention adopts shunt-resonant circuit peaking techniqueExisting.

As shown in Figure 3 a, described front balanced unit 21 includes: the current source I being in parallel_sWith the first capacitor C_pd, described inCurrent source I_sWith the first capacitor C_pdOne end connect voltage VDD, described current source I_sWith the first capacitor C_pdThe other end connect respectivelyConnect the first resistance R_fAOne end, inductance L_eqOne end and NMOS pipe n_A1Grid, described inductance L_eqThe other end pass throughThe second resistance R_eqGround connection, described the first resistance R_fAThe other end and NMOS pipe n_A1Common the 2nd NMOS pipe that connects of drain electrodeThe source electrode of nA2, the first resistance R_fAThis end and NMOS pipe n_A1Drain electrode and the 2nd NMOS pipe n_A2Also common structure of source electrodeBefore becoming, the output of balanced unit 21 connects the input of trans-impedance amplifier 22, described the 2nd NMOS pipe n_A2Drain electrode connect voltageVDD, grid is by the 3rd resistance R_dAConnect voltage VDD.

Wherein photodiode PD, current source I_sWith the first capacitor C_pdThe equivalent electric of formation photodetector parallel with one anotherRoad, they are respectively photogenerated current and the junction capacity of desired light electric diode, photodetector. Inductance L_eqWith the second resistance R_eqBe respectively on-chip inductor and resistance, the input capacitance C of they and transimpedance preamplifier_in(approximate NMOS pipe n_A2Grid source electricityHold C_gs,A2), input resistance R_in，AForm a shunt-resonant circuit (as Fig. 3 b).

Because the LR part impedance of series and parallel connections equates there is following relation:

${\mathrm{j\ω}}_0{L}_s+R_s=\[\left({\mathrm{j\ω}}_0{L}_P\right)\left|\right|R_P\]=\frac{{\left({\mathrm{\ω}}_0{L}_P\right)}^2{R}_P+{\mathrm{j\ω}}_0{L}_P{R_P}^2}{{R_P}^2+{\left({\mathrm{\ω}}_0{L}_P\right)}^2}$

Wherein Q=R_P/ω₀L_P＝ω₀L_S/R_S, can obtain:

R_P＝R_S(Q²+1)

$L_P=L_S\left(\frac{Q^2+1}{Q^2}\right)$

By this circuit equivalent be typical RLC network (Fig. 3 c), wherein:

R＝[R_eq(1+Q²)]||R_in,A

$L=L_{eq}\left(\frac{Q^2+1}{Q^2}\right)$

C＝C_pd+C_gs,A2

The resonant frequency of this resonant tank is

In addition the load of transimpedance preamplifier the one NMOS pipe n,_A1With the 3rd resistance R_dAForm an active inductance, itAlso form a shunt-resonant circuit with input capacitance and the input resistance of next stage. Make these two by parameter optimization adjustmentThe resonance peak that resonant tank produces is mutually overlapping, can effectively improve the bandwidth of Trans-impedance preamplifier. In addition, by significantly increasingAs the first resistance R across resistance_fAWith the second resistance R as pre-resistor_eqResistance can also increase the input of photoreceiverResistance, reduces the first resistance R_fAWith the second resistance R_eqThe noise current of introducing.

As shown in Figure 4, described post-equalization unit 24 includes the second capacitor C and the 4th resistance R that are in parallel, and describedOne end of two capacitor C and the 4th resistance R is connected the output of described limiting amplifier 13, described the second capacitor C and the 4th jointlyThe other end of resistance R is by a load resistance R_LGround connection, this end of described the second capacitor C and the 4th resistance R also forms rear equalThe output of weighing apparatus unit 24 connects the input of comparator 25.

The frequency response transfer function of this balanced device is

$H_e\left(\mathrm{\ω}\right)=\frac{1}{k}\×\frac{1+j\mathrm{\ω}T}{1+j\mathrm{\ω}T/k}---\left(1\right)$

Wherein, 1/k=R_L/(R+R_L),T＝RC,R_LBe load resistance, 1/k is the DC coefficient (ω=0) of balanced device. ?Its amplitude response is

$\left|H_e\left(\mathrm{\ω}\right)\right|=\frac{1}{k}\×\sqrt{\frac{1+{\mathrm{\ω}}^2{T}^2}{1+{\mathrm{\ω}}^2{T}^2/k^2}}---\left(2\right)$

The 3dB point result of calculation of this balanced device is

${\mathrm{\ω}}_{3dB}=\frac{1}{T}\sqrt{\frac{1}{1-2/k^2}}---\left(3\right)$

WhenTime, this 3dB point exists. Near this 3dB point, | H_e(ω) | be approximately linear. Equalizer frequency responseSlope s_eCan approximate representation be

$s_e=\frac{6\mathrm{\π}T}{\sqrt{\frac{1}{1-2/k^2}}}---\left(4\right)$

In order to make the gain balance of blue light components high band and low-frequency range, the response of balanced device requires s_e＝－s_b，s_bFor notWhile adding equilibrium, the frequency response curve slope of blue light components, is approximately-0.24dB/MHz. Adopt desired bandwidth balanced and that obtainCan approximate evaluation be

$W_{max}\≤\frac{20\lg k}{-s_b}---\left(5\right)$

Can be found out by (4) formula and (5) formula, the selection of T and k will determine the gain of balanced bandwidth and equalizing signal.Select a larger k value, will obtain higher modulation bandwidth.

Claims (3)

1. the receiver special IC based on visible light communication, include successively connect for by the electric current obtainingSignal is converted into voltage signal and the trans-impedance amplifier (22) that amplifies and for by the voltage of trans-impedance amplifier (22) outputSignal is amplified to the limiting amplifier (23) of digital voltage level, it is characterized in that the input of described trans-impedance amplifier (22)Connect the output for balanced unit (21) the electric current receiving from photodiode (PD) is compensated, described limitThe output of width amplifier (23) connect for to carry out from the voltage signal of limiting amplifier (23) output second compensationThe input of balanced unit (24), the output of described post-equalization unit (14) connects as the comparator (25) of signal decisionInput, the output of described comparator (25) forms the output of the receiver special IC based on visible light communication.

2. a kind of receiver special IC based on visible light communication according to claim 1, is characterized in that instituteThe front balanced unit (21) of stating includes: the current source (I being in parallel_s) and the first electric capacity (C_pd), described current source (I_s) and theOne electric capacity (C_pd) one end connect voltage VDD, described current source (I_s) and the first electric capacity (C_pd) the other end connect respectively firstResistance (R_fA) one end, inductance (L_eq) one end and NMOS pipe (n_A1) grid, described inductance (L_eq) the other end logicalCross the second resistance (R_eq) ground connection, described the first resistance (R_fA) the other end and NMOS pipe (n_A1) drain electrode common connect theTwo NMOS pipe (n_A2) source electrode, the first resistance (R_fA) this end and NMOS pipe (n_A1) drain electrode and the 2nd NMOS pipe(n_A2) source electrode also jointly form before balanced unit (21) output connect trans-impedance amplifier (22) input, described secondNMOS manages (n_A2) drain electrode connect voltage VDD, grid is by the 3rd resistance (R_dA) connection voltage VDD.

3. a kind of receiver special IC based on visible light communication according to claim 1, is characterized in that instituteThe post-equalization unit (24) of stating includes the second electric capacity (C) and the 4th resistance (R) that are in parallel, described the second electric capacity (C) andCommon output, described the second electric capacity (C) and the 4th resistance that connects described limiting amplifier (23) in one end of four resistance (R)(R) the other end is by a load resistance (R_L) ground connection, this end of described the second electric capacity (C) and the 4th resistance (R) also formsThe output of post-equalization unit (24) connects the input of comparator (25).