CN102496844B

CN102496844B - Complementary metal oxide semiconductor (CMOS) laser driving circuit for fourth generation (4G) radio-over-fiber

Info

Publication number: CN102496844B
Application number: CN 201110402640
Authority: CN
Inventors: 毛陆虹; 李建恒; 张世林; 谢生
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2011-12-07
Filing date: 2011-12-07
Publication date: 2013-07-17
Anticipated expiration: 2031-12-07
Also published as: CN102496844A

Abstract

The invention discloses a complementary metal oxide semiconductor (CMOS) laser driving circuit for fourth generation (4G) radio-over-fiber and relates to the field of radio communication. The CMOS laser driving circuit for the 4G radio-over-fiber is formed by connecting a CMOS analog radio frequency part, a CMOS digital part, an analog-to-digital converter and a laser with a photoelectric detector. The CMOS laser driving circuit for the 4G radio-over-fiber is designed by using an MOS which is low in power consumption and easy to integrate, has an analog pre-distortion function of correcting the non-linearity of the laser, and meets requirements of a standard of new generation (4G) radio communication time-division long term evolution (TD-LTE).

Description

The CMOS drive circuit for laser that is used for the 4G light carrier radio communication

Technical field

The present invention relates to wireless communication field, particularly relate to the CMOS drive circuit for laser for the 4G light carrier radio communication.

Background technology

In October, 2010, International Telecommunication Union determined that TD-LTE-Advanced is the 4th third-generation mobile communication (4G) international standard.The 50M frequency that in April, 2011, Ministry of Industry and Information formally gave an written reply between the 2570MHz-2620MHz is used for China TD-LTE.In order to solve the loss problem that high-frequency signal is propagated, and the requirement of the utilization ratio of frequency, the ROF technology that the convenient, flexible characteristic of a kind of technical characterstic of the low-loss wide bandwidth with optical fiber and wireless communication system combines is arisen at the historic moment.Wherein radio communication and optical fiber interface chip technology are that the drive circuit for laser design is one of key technology in the ROF technology (radio-over-fiber, light carrier radio communication).

In the ROF system, as non-linear dynamic range and the spectrum efficiency for the radio frequency optical transmission chain of the laser of the Primary Component of electric light conversion significant effects is arranged.Along with the increase of laser output power, its non-linear remarkable increase is when adopting the modulation signal modulated laser of certain bandwidth, can produce intermodulation component, cause spread spectrum, the neighboring trace signal be formed disturb, directly have influence on the error rate of the system of acceptance, worsen the performance of communication system.So, the non-linear most important thing that has just become electric light conversion chip research in the research and development 4G communication system of solution laser.

The drive circuit for laser of commercialization seldom has the part of predistortion at present, perhaps be difficult to satisfy the requirement of the high-frequency high-speed of 4G radio communication, and all there be to a certain degree non-linear in general laser, and the difference of this non-linear making material, technology and working temperature along with various lasers and difference.This just requires the design of drive circuit for laser guaranteeing that buffering and enlarging function satisfy under the linear prerequisite, also will design the predistortion circuit of offsetting the laser nonlinear characteristic especially.This predistortion circuit non-linear must be with laser non-linear opposite, and must leave very high flexibility ratio, to satisfy the requirement of different lasers and different operational environment.

Optical communication system is also very high to the requirement of circuit noise, requirement is being satisfied under the condition of high speed operation, because the noise that circuit itself is introduced is enough little, and the degree that the noise of drive circuit and anti-power supply disturb is subjected to the constraint of band-gap reference biasing circuit to a great extent, therefore realizes that the bearing interest reference offset circuit of low noise, high Power Supply Rejection Ratio can strengthen the performance of whole drive circuit for laser widely.

Summary of the invention

In view of this, the objective of the invention is at problems of the prior art, be provided for the CMOS drive circuit for laser of 4G light carrier radio communication.

For this reason, the invention provides the CMOS drive circuit for laser for the 4G light carrier radio communication, this CMOS drive circuit for laser can satisfy the requirement of high-speed transfer, and can be to the non-linear predistortion of carrying out of laser; Also must guarantee low noise, good modulation efficiency and to the applicability of various lasers simultaneously.

The CMOS drive circuit for laser that is used for the 4G light carrier radio communication, described CMOS drive circuit for laser for the 4G light carrier radio communication is by CMOS analog radio frequency part, the cmos digital part, analog to digital converter is formed by connecting with the laser that has photodetector, in described CMOS analog radio frequency part, following buffer every straight matching network with a pair of source electrode is connected, a pair of source electrode is followed buffer and is connected with primary/secondary amplifier, primary/secondary amplifier is connected with modulated current output array circuit, direct current biasing output-stage circuit is connected with modulated current output array circuit by electric capacity, the low-noise gap biasing circuit respectively with every straight matching network, a pair of source electrode is followed buffer and is connected with primary/secondary amplifier; In described cmos digital part, test circuit is connected with modulated current output array circuit, non-linear predistortion/modulation efficiency control circuit is connected with modulated current output array circuit, and power control circuit is connected with direct current biasing output-stage circuit; The laser that has photodetector is connected with power control circuit with non-linear predistortion/modulation efficiency control circuit respectively by analog to digital converter, and modulated current output array circuit is connected with the laser that has photodetector by electric capacity.

Preferably, in described CMOS analog radio frequency part, resistance R 1, capacitor C 1, resistance R 2, capacitor C 2 constitute main circuits every straight matching network, resistance R 9, capacitor C 5, resistance R 10, capacitor C 6 constitute auxiliary circuits every straight matching network, MOS transistor npn npn M4, M5, M6, M7 constitute the buffer of main circuit; MOS transistor npn npn M17, M18, M19, M20 constitute the buffer of auxiliary circuit, and MOS transistor npn npn M1, M2, M3, resistance R 3, resistance R 4 constitute main amplifier; MOS transistor npn npn M13, M14, M15, resistance R 11, resistance R 12 constitute auxilliary amplifier, capacitor C 3, resistance R 6, capacitor C 4, resistance R 5 constitute the high pass network of main circuit, capacitor C 7, resistance R 12, capacitor C 8, resistance R 11 constitute the high pass network of auxiliary circuit, and MOS transistor npn npn M10, M11, M12, M13 constitute the modulated current output array of main circuit; MOS transistor npn npn M21, M22, M23, M24 constitute the modulated current output array of auxiliary circuit, and MOS transistor npn npn M25, M26, M27, M28 constitute the direct current output array.

Preferably, described low-noise gap biasing circuit adopts bandgap reference voltage biasing and current offset, adopts the dual current mirror structure.

Preferably, in described low-noise gap biasing circuit, positive-negative-positive triode PNP1, resistance R 1, resistance R 3, nmos type transistor MN1, MN2, pmos type transistor MP1, MP2, MP3, MP4, MP5, MP6 constitute temperature coefficient and are negative current mirroring circuit, and pmos type transistor MP5, MP6 are start-up circuit; It is positive current mirroring circuit that positive-negative-positive triode PNP2, PNP3, resistance R 2, R4, nmos type transistor MN5, MN6, MN7, pmos type transistor MP9, MP10, MP11, MP12, MP13, MP14 constitute temperature coefficient, and pmos type transistor MP13, MP14 are start-up circuit; Pmos type transistor MP15, MP16, MP17, MP18, resistance R 5, nmos type transistor MN8 constitute the bias voltage output circuit, pmos type transistor MP19, MP20, MP21, MP22, MP23, MP24, MP25, MP26, nmos type transistor MN9, MN10, MN11, MN12, resistance R 6, R7 constitute the noise suppressed current mirroring circuit,, pmos type transistor MP27, MP28, MP29, MP30, MP31, MP32 constitute the bias current output circuit.

The input of described CMOS drive circuit for laser for the 4G light carrier radio communication has a capacitance resistance high pass network, can isolate the direct current biasing of prime module, simultaneously for the input band setting low frequency edge.Resistance wherein is 50 fixing Ω, realizes impedance matching with prime.Capacitance between the load resistance of main drive circuit and the electric current output array has been formed a low-pass network, for the input frequency band provides the high frequency border.

The output stage of described CMOS drive circuit for laser for the 4G light carrier radio communication has designed one group of electric current output array, can be by the cut-in voltage of NMOS pipe in the Dc bias control array be set, realize that the segmented current addition forms the electric current output of approximate quadratic function, offset non-linear in the output characteristic of laser, output saturation characteristic to laser is carried out analog predistortion, guarantees that the transmission characteristic of whole system keeps linear.Reasonably the turn on voltage threshold of design NMOS pipe can freely be set the flex point of segmented current, thereby weakens the signal intermodulation that occurs in the ROF transmission course, reduces noise, improves system signal noise ratio.The switching voltage that is arranged in the switch NMOS pipe of voltage-controlled NMOS pipe below simultaneously can realize that the segmented current output of digital form control NMOS pipe is at the slope delta of I-V (current-voltage) performance diagram, to satisfy the application of the different laser of luminous efficiency.

Described CMOS drive circuit for laser for the 4G light carrier radio communication has adopted bandgap reference voltage biasing and current offset, adopt simple dual current mirror structure, it is positive electric current that one group of current mirror produces temperature coefficient, one group of current mirror produces temperature coefficient and is negative electric current, the two-way electric current is produced temperature independent reference voltage through the mirror image addition through resistance, be used for the input voltage biasing of this drive circuit buffer circuits, can be provided in the free voltage benchmark in the system power supply voltage allowed band.Be different from traditional band-gap reference circuit, because the output reference voltage of this reference circuit does not adopt traditional structure that has activated amplifier, the noise of having avoided activated amplifier to bring, thus make the output of this band-gap reference better than the noise characteristic of traditional band-gap reference.The mirror image circuit that suppresses the special construction of noise has been adopted in current offset output simultaneously, can suppress the noise of current offset output greatly.The stacked PMOS current-mirror structure that adopts can increase the small signal impedance of current mirror, obtains better Power Supply Rejection Ratio (PSRR) performance.

By above technical scheme provided by the invention as seen, the present invention has following technique effect:

1. the analog signal that has predistortion.Substantially all be to adopt the resolution element method in the predistortion circuit of laser in the past, but the resolution element area occupied is big, and is unfavorable for the whole system monolithic integrated.The present invention adopts MOS technology to make, and produces pre-distorted signals by predistortion circuit, can solve the nonlinear problem of laser in the 4G communication.

2. applied widely, the predistortion amplitude is controlled.Because various lasers and different operational environments have caused the non-linear of laser to be not quite similar.In order to satisfy the predistortion requirement of various lasers, the method that employing of the present invention combines with digital circuit by the amplitude of digital control bias current and adjusting, finally produces the pre-distorted signals that is fit to this laser.

Description of drawings

Fig. 1 is the module map of the CMOS drive circuit for laser of 4G light carrier radio communication provided by the invention.

Fig. 2 is the circuit diagram of the CMOS drive circuit for laser of 4G light carrier radio communication provided by the invention.

Fig. 3 is the electric current output array circuit of the CMOS drive circuit for laser of 4G light carrier radio communication provided by the invention.

Fig. 4 is the low-noise gap reference offset circuit of the CMOS drive circuit for laser of 4G light carrier radio communication provided by the invention.

Fig. 5 is the flow chart of predistortion program of the CMOS drive circuit for laser of 4G light carrier radio communication provided by the invention.

Embodiment

In order to make those skilled in the art person understand the present invention program better, the present invention is described in further detail below in conjunction with drawings and embodiments.

The module map of the drive circuit for laser that has predistortion function shown in Figure 1 composed as follows: wherein CMOS simulation, in the radio frequency part every straight matching network, buffer, main, auxilliary amplifier, the modulated current output array, direct current output array and low noise bearing interest reference offset circuit all by standard CMOS 0.18um technology according to simulation, the radio circuit design cycle is made, test circuit in the cmos digital part, non-linear predistortion, modulation efficiency control circuit and power control circuit are all made according to the ASIC design cycle by standard CMOS 0.18um technology, ADC uses standard CMOS 0.18um technology to make, and these three parts realize that monolithic is integrated.

Input signal is at first through being input to buffer every the high pass characteristic of straight matching network with the difference AC signal, and the bias voltage of low noise bearing interest benchmark is received the common mode end points of 50 Ohmic resistances through a buffer simultaneously, for input provides direct current biasing.Differential signal is through buffer, directly drive the main and auxiliary amplifier of wideband, its output is through the grid of modulating tube in the electric capacity driving modulated current output array circuit, and the output modulated current is through the direct current addition drive laser of electric capacity and the output of direct current output array circuit.

Photodetector in the laser changes into the signal of telecommunication with the light signal of laser diode and is transferred to power control circuit and non-linear predistortion, modulation efficiency control circuit respectively through the digital-to-analogue conversion of ADC, the sampled point that provides at test circuit carries out the calculating of power calculation and nonlinear curve, the digital control end of result of calculation FEEDBACK CONTROL direct current output array and modulated current output array is realized automated power control and non-linear predistortion function.

Fig. 2 is the circuit diagram of drive circuit for laser analog radio frequency part main modular, comprises every straight matching network input buffer, main amplifier, modulated current output array, direct current output array and auxiliary circuit; Wherein the first half is main circuit, and the latter half is auxiliary circuit, and the main and auxiliary circuit structure is identical, and just the first half has comprised the direct current output array.

Among Fig. 2, VINP and VINN are differential input ends; VOUTP and VOUTN are difference output ends; AVDD is connected power supply and ground respectively with GND; VBIAS, IBIAS200uA export with the two-way bias current with the bias voltage output that IBIAS1mA is connected low-noise gap reference offset circuit respectively.Resistance R 1, capacitor C 1, resistance R 2, capacitor C 2 constitute main circuits every straight matching network; Resistance R 9, capacitor C 5, resistance R 10, capacitor C 6 constitute auxiliary circuits every straight matching network, the node VBIAS that resistance R 1, R2, R9, R10 connect jointly provides dc offset voltage for the AC differential signal of transmission, and resistance is 50 ohms impedance match of 50 ohm resistance R 1, R2, R9, R10 realization and input port simultaneously.MOS transistor npn npn M4, M5, M6, M7 constitute the buffer of main circuit; MOS transistor npn npn M17, M18, M19, M20 constitute the buffer of auxiliary circuit, in the capacitive load that reduces prime, a very big voltage controlled current is provided, increased the driving force to post-amplifier, the 200uA current mirror that the current mirroring circuit of being made up of MOS transistor npn npn M9, M6, M7, M19, M20 will be imported node IBIAS200uA input is enlarged into buffer circuits provides current offset.MOS transistor npn npn M1, M2, M3, resistance R 3, resistance R 4 constitute main amplifier; MOS transistor npn npn M13, M14, M15, resistance R 11, R12 constitute auxilliary amplifier, adopt the input of large scale difference pipe to be cooperated the structure of linear resistance, guaranteed linear undistorted, very big bandwidth of operation is provided simultaneously, and the 1mA current mirror that the current mirroring circuit of being made up of MOS transistor npn npn M8, M3, M15 will be imported node IBIAS1mA input is enlarged into amplifier circuit provides current offset.Capacitor C 3, resistance R 6, capacitor C 4, resistance R 5 constitute the high pass network of main circuit, capacitor C 7, resistance R 12, capacitor C 8, resistance R 11 constitute the high pass network of auxiliary circuit, and AC regulating voltage is coupled to above the grid that configures direct current biasing.MOS transistor npn npn M10, M11, M12, M13 constitute the modulated current output array of main circuit; MOS transistor npn npn M21, M22, M23, M24 constitutes the modulated current output array of auxiliary circuit, the output modulated current, again by resistance R 7, capacitor C 9, resistance R 8, capacitor C 10, resistance R 13, capacitor C 11, resistance R 14, the coupling network of capacitor C 12 exports output node to, IMODBIAS_A, IMODBIAS_B is respectively the modulated current output array different Dc biases is provided, control is main, the threshold voltage of auxilliary electric current output array, realize piecewise fitting secondary output characteristic, SWITCH_A＜1 〉, SWITCH_A＜0 〉, SWITCH_B＜1 〉, SWITCH_B＜0〉be respectively the modulated current output array switching voltage is provided, the break-make of control binary switch realizes regulating the effect of output voltage gradient.MOS transistor npn npn M25, M26, M27, M28 constitute the direct current output array, are directly connected on the output node IDCBIAS, SWITCHDC＜1 〉, SWITCHDC＜0 be respectively the direct current output array Dc bias and switching voltage be provided.

Fig. 3 is a N level electric current output array circuit diagram.VMOD is modulation voltage input node, and modulation voltage is sent to nmos type transistor MN1, MN2 through the capacitance resistance high pass network ... the grid of MNN, the control output current.VBIAS1, VBIAS2 ... VBIASN is the bias voltage node, control nmos type transistor MN1, MN2 ... the threshold voltage of MNN.Switch1, Switch2 ... SwitchN is switching voltage, control MNS1, MNS2 ... the break-make of MNSN switching tube.IMOD1, IMOD2 ... IMODN is the modulated current output node.

Fig. 4 is low-noise gap reference offset circuit diagram.Wherein positive-negative-positive triode PNP1, resistance R 1, resistance R 3, nmos type transistor MN1, MN2, pmos type transistor MP1, MP2, MP3, MP4, MP5, MP6 constitute the current mirroring circuit of temperature coefficient for bearing, and pmos type transistor MP5, MP6 are start-up circuit; It is positive current mirroring circuit that positive-negative-positive triode PNP2, PNP3, resistance R 2, resistance R 4, nmos type transistor MN5, MN6, MN7, pmos type transistor MP9, MP10, MP11, MP12, MP13, MP14 constitute temperature coefficient, and pmos type transistor MP13, MP14 are start-up circuit; Pmos type transistor MP15, MP16, MP17, MP18, resistance R 5, nmos type transistor MN8 constitute the bias voltage output circuit, current mirror summation with positive temperature coefficient and negative temperature coefficient, become temperature independent electric current, flow through linear resistance R5 and produce temperature independent voltage, wherein nmos type transistor MN8 connects into the form of electric capacity, play filtering and exchange interference, the effect of stable output.Pmos type transistor MP19, MP20, MP21, MP22, MP23, MP24, MP25, MP26, nmos type transistor MN9, MN10, MN11, MN12, resistance R 6, R7 constitute the noise suppressed current mirroring circuit, utilize small-signal behaviour different of resistance and metal-oxide-semiconductor, in the mirror image direct current, suppress the AC noise electric current.Pmos type transistor MP27, MP28, MP29, MP30, MP31, MP32 constitute the bias current output circuit, provide bias current by IBIAS50uA, IBIAS200uA, IBIAS1mA node for other modules respectively.

Fig. 5 is the flow chart of predistortion program.Before the drive circuit for laser work or between the working clearance, need to start the non-linear output characteristic that the predistortion program is corrected laser, concrete steps are as follows: at first, start the system clock in the test circuit or directly utilize the data clock that collects; With counter O reset; Counter carries out initialization; Begin counting, the control level of modulated current output array is along with counter is exported linear change simultaneously; Use the secondary differentiation method to calculate the second dervative of timing point each time, calculate the timing point (timing point of curvature maximum just) of second dervative maximum; The control voltage of this timing point correspondence is saved as the control voltage of modulated current output array; It is full until range to continue counting; Calculate the integral mean of input signal and the ratio of the numerical value sum at counting two ends, the integral mean of the output signal that the calculating photodetector feeds back and the ratio of the numerical value sum of counting two ends, if the difference of the two is within threshold range then finish the predistortion program, if the difference of the two is outside threshold range then prove that the slope of piecewise linearity output can not meet the demands, the switch bit control voltage of modulated current output array is added 1, restarting counting, until meeting the demands, finish the predistortion program.

The above only is preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims

1. the CMOS drive circuit for laser that is used for the 4G light carrier radio communication, it is characterized in that: described CMOS drive circuit for laser for the 4G light carrier radio communication is by CMOS analog radio frequency part, the cmos digital part, analog to digital converter is formed by connecting with the laser that has photodetector, in described CMOS analog radio frequency part, following buffer every straight matching network with a pair of source electrode is connected, a pair of source electrode is followed buffer and is connected with primary/secondary amplifier, primary/secondary amplifier is connected with modulated current output array circuit, direct current biasing output-stage circuit is connected with modulated current output array circuit by electric capacity, the low-noise gap biasing circuit respectively with every straight matching network, a pair of source electrode is followed buffer and is connected with primary/secondary amplifier; In described cmos digital part, test circuit is connected with modulated current output array circuit, non-linear predistortion/modulation efficiency control circuit is connected with modulated current output array circuit, and power control circuit is connected with direct current biasing output-stage circuit; The laser that has photodetector is connected with power control circuit with non-linear predistortion/modulation efficiency control circuit respectively by analog to digital converter, and modulated current output array circuit is connected with the laser that has photodetector by electric capacity.

2. the CMOS drive circuit for laser for the 4G light carrier radio communication according to claim 1, it is characterized in that: in described CMOS analog radio frequency part, resistance R 1, capacitor C 1, resistance R 2, capacitor C 2 constitute main circuits every straight matching network, resistance R 9, capacitor C 5, resistance R 10, capacitor C 6 constitute auxiliary circuits every straight matching network, MOS transistor npn npn M4, M5, M6, M7 constitute the buffer of main circuit; MOS transistor npn npn M17, M18, M19, M20 constitute the buffer of auxiliary circuit, and MOS transistor npn npn M1, M2, M3, resistance R 3, resistance R 4 constitute main amplifier; MOS transistor npn npn M13, M14, M15, resistance R 11, resistance R 12 constitute auxilliary amplifier, capacitor C 3, resistance R 6, capacitor C 4, resistance R 5 constitute the high pass network of main circuit, capacitor C 7, resistance R 12, capacitor C 8, resistance R 11 constitute the high pass network of auxiliary circuit, and MOS transistor npn npn M10, M11, M12, M13 constitute the modulated current output array of main circuit; MOS transistor npn npn M21, M22, M23, M24 constitute the modulated current output array of auxiliary circuit, and MOS transistor npn npn M25, M26, M27, M28 constitute the direct current output array.

3. the CMOS drive circuit for laser for the 4G light carrier radio communication according to claim 1 is characterized in that: described low-noise gap biasing circuit employing bandgap reference voltage biasing and current offset, employing dual current mirror structure.

4. the CMOS drive circuit for laser for the 4G light carrier radio communication according to claim 1, it is characterized in that: in described low-noise gap biasing circuit, positive-negative-positive triode PNP1, resistance R 1, resistance R 3, nmos type transistor MN1, MN2, pmos type transistor MP1, MP2, MP3, MP4, MP5, MP6 constitute temperature coefficient and are negative current mirroring circuit, and pmos type transistor MP5, MP6 are start-up circuit; It is positive current mirroring circuit that positive-negative-positive triode PNP2, PNP3, resistance R 2, R4, nmos type transistor MN5, MN6, MN7, pmos type transistor MP9, MP10, MP11, MP12, MP13, MP14 constitute temperature coefficient, and pmos type transistor MP13, MP14 are start-up circuit; Pmos type transistor MP15, MP16, MP17, MP18, resistance R 5, nmos type transistor MN8 constitute the bias voltage output circuit, pmos type transistor MP19, MP20, MP21, MP22, MP23, MP24, MP25, MP26, nmos type transistor MN9, MN10, MN11, MN12, resistance R 6, R7 constitute the noise suppressed current mirroring circuit,, pmos type transistor MP27, MP28, MP29, MP30, MP31, MP32 constitute the bias current output circuit.