CN210297704U

CN210297704U - High-speed visible light communication optical transmitter based on multi-quantum well blue light micro LED

Info

Publication number: CN210297704U
Application number: CN201920702197.1U
Authority: CN
Inventors: 魏正军; 管晓军; 陶志远; 顾佳美; 王桂发; 尹以安
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2020-04-10
Anticipated expiration: 2029-05-16

Abstract

The utility model relates to a high-speed visible light communication optical transmitter based on little LED of multiple quantum well blue light, include: the multi-quantum well blue light micro LED is used as a light source; the pre-emphasis circuit is used for pre-compensating the high-frequency component of the signal to be transmitted at the transmitting end; the pre-amplifier circuit is used for compensating gain attenuation brought by the pre-emphasis circuit; the LED driving circuit is used for performing voltage gain on a signal output by the preceding stage amplifying circuit and providing modulation current for the multi-quantum well blue light micro LED; the impedance matching circuit is used for carrying out impedance matching on the LED driving circuit and the multi-quantum well blue light micro LED; the constant current source circuit is used for providing constant direct current bias current for the multi-quantum well blue light micro LED; the pre-emphasis circuit, the preceding-stage amplification circuit LED drive circuit, the impedance matching circuit, the multi-quantum well blue light micro LED and the constant current source circuit are connected in sequence. The scheme can realize long-distance high-speed real-time visible light communication through the LED.

Description

High-speed visible light communication optical transmitter based on multi-quantum well blue light micro LED

Technical Field

The utility model belongs to the technical field of the photoelectric technology and specifically relates to a high-speed visible light communication optical transmitter based on little LED of multiple quantum well blue light is related to.

Background

At present, the conventional wireless communication method is mainly radio frequency wireless communication. The major drawbacks of radio frequency wireless communication are two. On one hand, radio frequency wireless communication can generate electromagnetic radiation, and the battery radiation can greatly pollute the production or living environment of people. The harm to human health mainly comprises: nerve damage, heart dysfunction, hematopathy, memory deterioration, cataract, brain tumor, breast cancer, etc. On the other hand, with the use of a large amount of radio frequency communication, radio frequency band resources are increasingly tense, a frequency band is required to be applied for the application of wireless communication, and the random use of radio frequency communication is highly likely to interfere with peripheral communication systems, such as an interfering broadcast station, an aircraft navigation control system, or an interfering military radar. Therefore, new wireless communication methods are required to replace or supplement the conventional wireless radio frequency communication.

Compared with the traditional radio frequency wireless communication technology, the visible light communication has the advantages of high communication speed, no need of radio frequency spectrum authentication, no electromagnetic radiation, no electromagnetic interference, high confidentiality and the like. At present, the main visible light communication technology mainly uses a white light LED, and mainly uses a fluorescent LED, and the fluorescent LED has the advantages of simple manufacture, mature process and the like, but the modulation bandwidth of the existing fluorescent LED is very low and is only a few megahertz, so that the bandwidth of a visible light communication system is severely limited, and the application of a higher-speed occasion cannot be met. In addition, in the existing application scenario, because the impedance of the LED is not matched with the internal resistance of the driver, the output power of the driver cannot be completely loaded on the LED due to the existence of the power reflection phenomenon. Therefore, the adoption of the LED with high response rate to replace the existing fluorescent LED and the design of the corresponding impedance matching circuit become the urgent problem to be solved on the development road of the visible light communication technology.

SUMMERY OF THE UTILITY MODEL

In view of the above, there is a need to provide a high-speed visible light communication optical transmitter based on a multi-quantum well blue micro LED, which can implement long-distance high-speed real-time visible light communication through the LED, and has the advantages of high modulation bandwidth, high transmission rate, and low communication error rate.

A high-speed visible light communication optical transmitter based on a multi-quantum well blue light micro LED comprises: the multi-quantum well blue light micro LED is used as a light source; the pre-emphasis circuit is used for pre-compensating the high-frequency component of the signal to be transmitted at the transmitting end; the pre-amplifier circuit is used for compensating gain attenuation brought by the pre-emphasis circuit; the LED driving circuit is used for performing voltage gain on a signal output by the preceding stage amplifying circuit and providing modulation current for the multi-quantum well blue light micro LED; the impedance matching circuit is used for carrying out impedance matching on the LED driving circuit and the multi-quantum well blue light micro LED; the constant current source circuit is used for providing constant direct current bias current for the multi-quantum well blue light micro LED; the pre-emphasis circuit, the pre-stage amplification circuit, the LED drive circuit, the impedance matching circuit, the multi-quantum well blue light micro LED and the constant current source circuit are connected in sequence.

The modulation bandwidth of the multi-quantum well blue light micro LED is 65 MHz.

The pre-emphasis circuit is a T-shaped pre-emphasis circuit consisting of a resistor, a capacitor and an inductance passive device, and the gain compensation is 19 dB.

The pre-stage amplifying circuit includes a high-speed operational amplifier THS3201 and peripheral devices thereof.

The LED driving circuit includes an operational amplifier THS3491 and peripheral devices thereof.

The impedance matching circuit is a lumped parameter impedance matching circuit consisting of passive devices such as resistors, capacitors and inductors.

The constant current source circuit comprises a radio frequency transistor BLT81, an operational amplifier AD8009 and peripheral devices thereof.

The utility model provides a high-speed visible light communication optical transmitter based on little LED of multi-quantum well blue light adopts little LED of multi-quantum well blue light as the light source, deploys pre-emphasis circuit, preceding stage amplifier circuit, LED drive circuit, impedance matching circuit and constant current source circuit around the light source, compares current fluorescence type LED visible light communication, has the modulation broadband height, transmission rate is high, the advantage that communication error rate is low.

Drawings

Fig. 1 is a schematic circuit diagram of a high-speed visible light communication optical transmitter based on multiple quantum well blue light micro LED according to the present invention;

fig. 2 is a schematic diagram of a connection structure for performance testing of a high-speed visible light communication optical transmitter based on a multi-quantum well blue light micro LED according to the present invention;

fig. 3 is a frequency response diagram of InGaN/GaN multi-quantum well blue light micro LED in the high-speed visible light communication optical transmitter based on multi-quantum well blue light micro LED of the present invention;

fig. 4 is a frequency response diagram of a pre-emphasis circuit in a high-speed visible light communication optical transmitter based on multiple quantum well blue light micro LEDs according to the present invention;

fig. 5 is a system frequency response diagram of the high-speed visible light communication optical transmitter based on the multiple quantum well blue light micro LED of the present invention;

fig. 6 is an eye diagram test chart of the high-speed visible light communication optical transmitter based on multiple quantum well blue light micro LED of the present invention when the input signal is random codes with different rates;

fig. 7 is the high-speed visible light communication optical transmitter based on little LED of multiple quantum well blue light under 2 m's communication distance, the eye chart test chart of system when the input signal is 622 Mbps's random code.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the disclosure of the present specification, and the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

Specifically, referring to fig. 1, the utility model provides a high-speed visible light communication optical transmitter based on little LED of multiple quantum well blue light, include: a multi-quantum well blue micro LED (5-1) used as a light source; a pre-emphasis circuit (1) for pre-compensating the high-frequency component of the signal to be transmitted at the transmitting end; a pre-amplifier circuit (2) for compensating gain attenuation caused by the pre-emphasis circuit; the LED driving circuit (3) is used for carrying out voltage gain on signals output by the pre-stage amplifying circuit (2) and providing modulation current for the multi-quantum well blue light micro LED (5-1); the impedance matching circuit (4) is used for carrying out impedance matching on the LED driving circuit (3) and the multi-quantum well blue light micro LED (5-1); and a constant current source circuit (5) for providing a constant direct current bias current to the multiple quantum well blue light micro LED (5-1); the pre-emphasis circuit (1), the pre-stage amplification circuit (2), the LED drive circuit (3), the impedance matching circuit (4), the multi-quantum well blue light micro LED (5-1) and the constant current source circuit (5) are connected in sequence.

The light source adopted by the embodiment can be an InGaN/GaN multi-quantum well blue light micro LED, the modulation bandwidth of which is 65MHz and is far higher than that of the existing fluorescent LED.

The pre-emphasis circuit (1) is a T-shaped pre-emphasis circuit mainly composed of passive devices such as resistors, capacitors and inductors. The C1 and the L1 determine the high-frequency cut-off frequency and the gain amplitude of the circuit, and simultaneously control the rising trend of the low-frequency gain of the amplitude-frequency characteristic curve, the R1 and the R4 are used for adjusting the initial amplitude of the low frequency of the amplitude-frequency characteristic curve, and parameters of each component in the circuit can be adjusted according to the frequency response characteristic of the LED. In the embodiment of the present invention, since the modulation bandwidth of the selected LED is 65MHz (as shown in fig. 3), the values of the components are C1 ═ 18nF, L1 ═ 33nH, R1 ═ 1k, R4 ═ 10 Ω, C2 ═ 22pF, L2 ═ 5.1nH, and R2 ═ R3 ═ RT1 ═ 50 Ω. The gain compensation is 19dB as shown in fig. 4.

The pre-stage amplifying circuit (2) is composed of an operational amplifier THS3201 and peripheral devices thereof. THS3201 belongs to a current feedback type high-speed operational amplifier, the gain bandwidth product of the THS3201 is up to 1.8GHz, the slew rate is up to 6700V/mu s, the output current of the THS3201 can reach 100mA at the working voltage of plus or minus 5V, and the THS 320has strong load driving capacity, so that the THS3201 is often used as a radio frequency amplifier by electronic engineers. In the embodiment of the present invention, since the pre-emphasis circuit brings about the gain attenuation of nearly 29dB, the gain of the pre-stage amplifier circuit is designed to be about 20 dB. Since the input of the operational amplifier is in a high impedance state when it is used as a cascode amplifier, a 50 Ω resistor needs to be pulled down to ground, i.e. RT2 in the figure, at the cascode terminal of THS3201 in order to match the 50 Ω internal resistance of the signal source. The capacitor CF1 and resistor Riso prevent high frequency oscillations from occurring in the circuit, since the impedance of CF1 is much smaller than RF1 at high frequencies, the feedback signal flows directly from CF1, and Riso isolates the load from the output of THS 3201. Co1 provides a gain peak to the circuit so that high frequency roll-off can be compensated.

The LED drive circuit (3) is composed of an operational amplifier THS3491 and peripheral devices thereof. THS3491 belongs to a high-Power output current feedback type high-speed operational amplifier with Power down function, the slew rate is as high as 8000V/mus, the output signal slew can reach 28VPP under the working voltage of plus or minus 15V, the output current can reach plus or minus 500mA to the maximum extent, the packaging design with PowerPAD has strong driving load capacity, and the heat dissipation problem is well solved. The LED has large junction capacitance, and the characteristics of THS3491 high voltage swing, wide output swing and large output current are very suitable for driving the LED. In the embodiment of the utility model provides, provide certain voltage gain simultaneously in order to guarantee the steady operation of driver, set up its gain into 20dB, the design of input is unanimous with the preceding stage amplification, and homodromous input drop-down 50 omega's resistance RT4 for match THS 3201's output resistance Ro 1. In addition, a direct current bias is added to the same-direction input end of the THS3491 in an alternating current coupling mode, a direct current bias voltage is obtained by dividing a power supply voltage through two high-precision resistors, and in order to avoid the bias voltage from being amplified, a direct current blocking capacitor Cg is added, and the value of the direct current blocking capacitor Cg is set to be 1 muF.

The impedance matching circuit (4) mainly comprises passive devices such as a resistor, a capacitor, an inductor and the like, and is a lumped parameter impedance matching circuit. The impedance of the LED is generally much larger than the output impedance of the driver, and according to the principle of maximum load power, the LED can obtain maximum power from the driver only when the output impedance of the driver is equal to the impedance of the LED. The embodiment of the utility model provides an in, lumped parameter impedance matching circuit (4) mainly include the three part, wherein (4-1) can make S11 curve track toward the centre of a circle convergence, (4-2) then can make S11 curve track turn left translation, (4-3) be 4 th order band-pass filter circuit, the band-pass network can reduce the Q value, thereby increase the bandwidth, generally can be through changing the number of knots n of band-pass type impedance transformation network, and then change the Q value of circuit, the value of n is bigger, the Q value is smaller, the bandwidth is bigger, the embodiment of the utility model provides an n sets up to 2, each components and parts parameter setting is as follows in the circuit: c3 ═ 20pF, L3 ═ 12nH, C4 ═ 47pF, L4 ═ 100nH, C5 ═ 220pF, L5 ═ 180nH, C6 ═ 36pF, L6 ═ 36 nH. In the embodiment, the S11 parameter of the LED is successfully reduced from-8 dB to below-15 dB through the impedance matching circuit.

The radio frequency transistor constant current source circuit (5) mainly comprises a radio frequency transistor BLT81 and an operational amplifier AD8009, wherein BLT81 is an ultrahigh frequency power transistor produced by Emuzpu, the maximum working current of the ultrahigh frequency power transistor can reach 500mA, the maximum working frequency is above 900MHz, and the ultrahigh frequency power transistor constant current source circuit has a very small junction capacitance and is suitable for being used in high frequency. In the present embodiment, the current source is designed to sink current, bias current flows from the power source VLED through the LED (5-1) into the current source, and the modulation signal is coupled to the cathode of the LED (5-1) through a 1 μ F capacitor C7. The direct current of the current source is constant and adjustable, the modulation bandwidth of the LED is generally related to the magnitude of the bias current, and the bias current of the LED used in the embodiment is set to be 50 mA. In the current source circuit diagram (5), a potentiometer connected to the base of a radio frequency transistor can realize adjustment of the magnitude of bias current, current in a loop is converted into voltage through a sampling resistor Re connected in series to the emitter of the transistor and then is connected to the reverse input end of an AD8009, the output end of the AD8009 is connected to the base of the transistor through a reverse diode to form closed loop feedback, and due to the fact that the diode has a voltage clamping function, maximum output limitation of the loop current can be realized through adjustment of the potentiometer connected to the same-direction input end of the AD 8009. Lc1, Lc2, Rc1, and Rc2 can improve low frequency characteristics of the circuit.

The high-speed visible light communication optical transmitter based on the multi-quantum well blue light micro LED performs high-frequency compensation and amplification on a signal to be transmitted, then is superposed with a direct current bias driving LED to be transmitted through a driving circuit, and finally is quantized and judged through a waveform shaping circuit at a receiving end by using a Newport 1601 as a photoelectric converter, so that long-distance high-speed real-time wireless visible light optical communication is realized. High-speed visible light communication optical transmitter based on little LED of multiple quantum well blue light can realize the broadband analog modulation to LED, under 2 meters communication distance, 3-dB modulation bandwidth reaches more than 450MHz, data transmission rate is more than 800Mbps, under 622 Mbps's communication rate, it is 3.02x10-12 to record real-time communication bit error rate BER, the limit BER that is far less than Forward Error Correction (FEC) threshold value is 3.8x10-3, satisfy completely in the high quality communication protocol about the BER be less than or equal to 10-10 the requirement. As far as we know, the communication error rate is the lowest that can be realized in a visible light communication system based on an NRZ-OOK modulation mode, so that the high-speed visible light communication optical transmitter based on the multiple quantum well blue light micro LED can be judged to completely support high-quality high-speed communication.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A high-speed visible light communication optical transmitter based on a multi-quantum well blue light micro LED is characterized by comprising: the multi-quantum well blue light micro LED is used as a light source; the pre-emphasis circuit is used for pre-compensating the high-frequency component of the signal to be transmitted at the transmitting end; the pre-amplifier circuit is used for compensating gain attenuation brought by the pre-emphasis circuit; the LED driving circuit is used for performing voltage gain on a signal output by the preceding stage amplifying circuit and providing modulation current for the multi-quantum well blue light micro LED; the impedance matching circuit is used for carrying out impedance matching on the LED driving circuit and the multi-quantum well blue light micro LED; the constant current source circuit is used for providing constant direct current bias current for the multi-quantum well blue light micro LED; the pre-emphasis circuit, the pre-stage amplification circuit, the LED drive circuit, the impedance matching circuit, the multi-quantum well blue light micro LED and the constant current source circuit are connected in sequence.

2. The multiple quantum well blue light micro LED based high speed visible light communication optical transmitter of claim 1, wherein the modulation bandwidth of the multiple quantum well blue light micro LED is 65 MHz.

3. The high-speed visible light communication optical transmitter based on the multiple quantum well blue light micro-LED as claimed in claim 2, wherein the pre-emphasis circuit is a T-shaped pre-emphasis circuit composed of passive devices of resistors, capacitors and inductors, and the gain compensation is 19 dB.

4. The high-speed visible light communication optical transmitter based on the multiple quantum well blue micro LED according to claim 2, wherein the pre-amplifier circuit comprises a high-speed operational amplifier THS3201 and its peripheral devices.

5. The high-speed visible light communication optical transmitter based on the multiple quantum well blue micro LED according to claim 2, wherein the LED driving circuit comprises an operational amplifier THS3491 and its peripheral devices.

6. The high-speed visible light communication optical transmitter based on the multiple quantum well blue light micro LED according to claim 5, wherein the impedance matching circuit is a lumped parameter impedance matching circuit composed of passive devices of resistance, capacitance and inductance.

7. The multi-quantum-well blue-light micro-LED based high-speed visible light communication optical transmitter according to claim 2, wherein the constant current source circuit comprises a radio frequency transistor BLT81, an operational amplifier AD8009 and its peripheral devices.