CN104748858B - A kind of InGaAs short-wave infrareds detector signal processing system - Google Patents

Abstract

The invention discloses an InGaAs short-wave infrared detector signal processing system, which comprises an InGaAs short-wave infrared detector, a signal input terminal, a differential single-end conversion circuit, a signal conditioning filter circuit, an analog-to-digital conversion circuit, and a data processing circuit. The system realizes signal impedance matching, amplification, and main-backup interface support through a differential single-ended conversion circuit. The signal is processed by a signal conditioning filter circuit, and then enters an analog-to-digital conversion circuit to output digital data, and finally transmits the data to a data processing circuit. middle. Compared with the traditional InGaAs short-wave infrared detector signal processing system, it has the characteristics of low noise introduced by the circuit, the input terminal supports system main backup, and strong anti-interference ability.

Description

A signal processing system of InGaAs short-wave infrared detector

technical field

The invention relates to a signal processing system, in particular to an InGaAs short-wave infrared detector signal processing system, which belongs to the field of signal processing.

Background technique

InGaAs short-wave infrared detector is a new type of linear array uncooled infrared detector in recent years. Compared with traditional cooled infrared devices, it has the characteristics of small size, low cost and low power consumption with similar performance. , especially suitable for application in the fields of military reconnaissance and aerospace remote sensing. The output signal of the InGaAs short-wave infrared detector has the following characteristics: 1) The output internal resistance is large, usually requiring a smaller load capacitance and a larger load resistance; 2) Higher circuit noise index requirements; 3) Generally, differential analog output is used 4) Each pixel signal maintains a fixed level value after it is established. According to the above signal output characteristics, how to design a signal processing system that can meet the requirements is very critical for the imaging circuit to achieve the ideal imaging effect.

The traditional InGaAs shortwave infrared detector signal processing system usually uses an emitter follower circuit to achieve impedance matching for each channel signal, and then directly amplifies and filters the output analog differential signal through a differential operational amplifier, and finally sends it to the analog The digital converter performs analog-to-digital conversion. This processing method has the following disadvantages: 1) Using the emitter follower circuit to perform impedance matching on the two channels respectively will cause the differential signal to be unbalanced due to the parameter difference of the two channel circuits, especially the parameter difference of the operational amplifier, which is quite Because of the introduction of differential mode noise; 2) The design of the follower circuit is adopted, and the device drift of the two channels has a great influence on the DC level signal, which will cause the image data of the imaging system to be unstable; 3) The design of the follower circuit can only The amplifying link of the analog signal is placed in the rear stage of the analog signal channel, which is not conducive to the suppression of the noise of the entire system circuit; 4) Two channels use two operational amplifiers to form an emitter follower circuit, which will increase additional 5) The traditional design does not consider the support of the main and backup interfaces of the analog signal, which undoubtedly limits the application range of the system and is not conducive to the improvement of system reliability.

Contents of the invention

The problem solved by the technology of the present invention is: to overcome the deficiencies of the prior art, to provide an InGaAs short-wave infrared detector signal processing system, which solves the two-channel signal imbalance existing in the traditional similar system, and the signal amplification link is introduced after the signal channel Additional circuit noise and the problem that traditional systems do not support active and standby interfaces at the input.

The technical solution of the present invention is: an InGaAs short-wave infrared detector signal processing system, including: an InGaAs short-wave infrared detector, a signal input terminal, a differential single-ended conversion circuit, a signal conditioning filter circuit, an analog-to-digital conversion circuit, and a data processing circuit ; wherein the InGaAs short-wave infrared detector is responsible for converting the detected optical signal into a differential electrical signal and sending it to the signal input terminal; the signal input terminal includes a first source terminal resistance R1 and a second source terminal resistance R2;

The signal input terminal, after matching the differential electrical signal through the first source terminal resistance R1 and the second source terminal resistance R2, outputs a differential electrical signal matching the differential single-end conversion circuit as the input of the differential single-end conversion circuit, the first source One end of the end resistance R1 and the second source end resistance R2 are respectively connected to the signal output end of the InGaAs short-wave infrared detector, and the other ends of the first source end resistance R1 and the second source end resistance R2 are used as the input of the differential single-end conversion circuit;

The differential single-ended conversion circuit converts the input differential signal into a single-ended signal and sends it to the signal conditioning filter circuit, and realizes impedance matching for the input differential signal, and amplifies the input differential signal. At the same time, the differential single-ended conversion circuit is also used as a system Primary and backup interfaces;

The signal conditioning filter circuit performs filtering and conditioning on the single-ended signal sent by the differential single-ended conversion circuit, obtains an analog differential signal within the dynamic range input by the analog-to-digital conversion circuit, and sends it to the analog-to-digital conversion circuit;

The analog-to-digital conversion circuit converts the analog differential signal sent by the signal conditioning filter circuit into a parallel digital signal and sends it to the data processing circuit;

The data processing circuit implements digital filtering on the digital signal sent by the analog-to-digital conversion circuit and then performs parallel-to-serial conversion to obtain corresponding serial data, and packs the data into the required data format.

The advantage of the present invention compared with prior art is:

(1) The present invention adopts a differential single-ended operational amplifier with power-off zero output characteristics in the differential single-ended conversion circuit, which can support the main backup interface of the input signal.

(2) The present invention places the amplifying link of the analog signal in the front stage of the system, that is, the differential single-ended conversion circuit, which can effectively avoid the amplification of introducing noise to the subsequent stage circuit.

(3) The impedance matching circuit formed by the differential single-ended operational amplifier used in the differential single-ended conversion circuit of the present invention has better circuit symmetry characteristics than the emitter follower circuit.

(4) Each part of the circuit adopted by the present invention has fewer components, smaller occupied area and lower power consumption.

Description of drawings

Fig. 1 is the schematic diagram of signal processing system of the present invention;

Fig. 2 is a schematic diagram of a differential single-ended conversion circuit of the present invention;

Fig. 3 is a schematic diagram of the signal conditioning filter circuit of the present invention;

FIG. 4 is an actual measurement diagram of the signal-to-noise ratio of the imaging circuit realized by the present invention.

detailed description

The idea of the present invention is: according to the characteristics of the output signal of the InGaAs short-wave infrared detector, firstly, the differential signal output by the detector is converted into a single-ended signal through a differential single-ended conversion circuit and the signal is amplified, and then the signal is conditioned and filtered to complete Analog-to-digital conversion, and finally the converted data is digitally filtered, parallel-to-serial converted, and then packaged into the required data format; at the same time, according to the power-off zero output characteristics of the selected differential single-ended operational amplifier, the main backup interface for the input signal is realized support.

The present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, it is a schematic diagram of an InGaAs short-wave infrared detector signal processing system of the present invention, including an InGaAs short-wave infrared detector, a signal input terminal, a differential single-ended conversion circuit, a signal conditioning filter circuit, an analog-to-digital conversion circuit, A data processing circuit, wherein the data processing circuit is realized by a programmable logic device. The InGaAs short-wave infrared detector converts the detected optical signal into a differential electrical signal and sends it to the signal input terminal; the signal input terminal includes a first source terminal resistance R1 and a second source terminal resistance R2;

The signal input terminal, after matching the differential electrical signal through the first source terminal resistance R1 and the second source terminal resistance R2, outputs a differential electrical signal matching the differential single-end conversion circuit as the input of the differential single-end conversion circuit, the first source One end of the end resistance R1 and the second source end resistance R2 are respectively connected to the signal output end of the InGaAs short-wave infrared detector, and the other ends of the first source end resistance R1 and the second source end resistance R2 are used as the input of the differential single-end conversion circuit;

The differential single-ended conversion circuit converts the input differential signal into a single-ended signal and sends it to the signal conditioning filter circuit, and realizes impedance matching for the input differential signal, and amplifies the input differential signal. At the same time, the differential single-ended conversion circuit is also used as a system Primary and backup interfaces;

The signal conditioning filter circuit performs filtering and conditioning on the single-ended signal sent by the differential single-ended conversion circuit, obtains an analog differential signal within the dynamic range input by the analog-to-digital conversion circuit, and sends it to the analog-to-digital conversion circuit;

The analog-to-digital conversion circuit converts the analog differential signal sent by the signal conditioning filter circuit into a parallel digital signal and sends it to the data processing circuit;

The data processing circuit implements digital filtering on the digital signal sent by the analog-to-digital conversion circuit and then performs parallel-to-serial conversion to obtain corresponding serial data, and packs the data into the required data format.

As shown in FIG. 1, the first source resistor R1, the second source resistor R2 and the equivalent input capacitance of the differential single-ended operational amplifier 221 in the differential single-ended conversion circuit form a low-pass filter circuit. The first source resistors R1, Both ends of the second source resistor R2 are respectively connected to the output terminal of the InGaAs short-wave infrared detector and the input terminals Vi+ and Vi− of the differential single-ended operational amplifier 221 . The selection of the resistance values of the first source terminal resistor R1 and the second source terminal resistor R2 needs to meet the following requirements: 1) The signal symmetry requirement of the differential signal, that is, R1=R2; 2) The source terminal matching requirement, generally select R1=R2< 50Ω. The first source resistor R1 and the second source resistor R2 are mainly used as source matching resistors of the input interface to prevent circuit signal reflection.

The differential single-ended conversion circuit mainly realizes the impedance matching of the differential electrical signal, the amplification of the differential electrical signal and the support function of the main backup interface of the system. Its schematic diagram is shown in Figure 2, including the first resistor R3, the second resistor R4, the third resistor Resistor R5 and differential single-ended operational amplifier 211, differential single-ended operational amplifier 221 includes differential input terminal 1+, differential input terminal 1-, differential input terminal 2+, differential input terminal 2-, output terminal Vs and equivalent input capacitance, The differential input terminal 1+ and the differential input terminal 1- are respectively connected to one end of the first source terminal resistor R1 and the second source terminal resistor R2, and at the same time, one terminal of the first source terminal resistor R1 and the second source terminal resistor R2 is also the same as the differential single-ended The equivalent input capacitance of the operational amplifier 221 is connected. One end of the first resistor R3 is connected to the input terminal 2+ of the differential single-ended operational amplifier 221, and the other end is connected to the circuit ground. One end of the second resistor R4 is connected to the input terminal 2- of the differential single-ended operational amplifier 221, and the other end is connected to the circuit ground. One terminal of the third resistor R5 is connected to the input terminal 2 − of the differential single-ended operational amplifier 221 , and the other terminal is connected to the output terminal Vs of the differential single-ended operational amplifier 221 . The differential single-ended conversion circuit converts the differential signal into a single-ended signal, mainly to remove the common-mode DC level contained in the differential electrical signal. The differential single-ended conversion circuit places the signal amplification link at the front end of the system to avoid the The circuit noise amplification of the subsequent stage takes into account the function of impedance matching. The differential single-ended operational amplifier 211 is a device with an input impedance greater than 750kΩ, an input capacitance less than 15pF, and a power-off zero output characteristic. The characteristics of high input impedance and low input capacitance are In order to meet the matching with the differential electrical signal output by the InGaAs short-wave infrared detector, and the power-off zero output feature is to realize the support for the main backup interface. In order to ensure the balance of the circuit, the first resistor R3, the second resistor R4, and the third resistor The value of R5 should satisfy R3=R4//R5; the circuit gain of the differential single-ended conversion circuit is

The signal conditioning filter circuit includes two parts: a single-end to differential circuit and a low-pass filter circuit. The schematic diagram is shown in FIG. The resistor R8 and the seventh resistor R9; the low-pass filter circuit includes the eighth resistor R10, the ninth resistor R11 and the capacitor C1; the differential operational amplifier 231 includes a non-inverting input terminal, an inverting input terminal, a non-inverting output terminal, an inverting output terminal, Common-mode input terminal V _VCM ; one end of the fourth resistor R6 is connected to the output terminal V _s of the differential single-ended operational amplifier 221, the other end of the fourth resistor R6 is connected to the non-inverting input terminal of the differential operational amplifier 231, and the fifth resistor R7 One end is connected to the circuit ground, the other end of the fifth resistor R7 is connected to the inverting input end of the differential operational amplifier 231, the two ends of the sixth resistor R8 are respectively connected to the non-inverting input end and the inverting output end of the differential operational amplifier 231, and the seventh The two ends of the resistor R9 are respectively connected to the inverting input terminal and the non-inverting output terminal of the differential operational amplifier 231; the common-mode input terminal V _VCM of the differential operational amplifier 231 is connected to the analog-to-digital conversion circuit; one end of the eighth resistor R10 is connected to the differential operational amplifier The inverting output terminal of 231, the other end is used as the inverting input end of the analog-to-digital conversion circuit on the one hand, and one end of the capacitor C1 is connected on the other hand, one end of the ninth resistor R11 is connected to the non-inverting output end of the differential operational amplifier 231, and the other end is a On the one hand, it is used as the non-inverting input terminal of the analog-to-digital conversion circuit, on the other hand, it is connected to the other end of the capacitor C1; due to the requirements of the balance characteristics of the single-ended to differential circuit, the fourth resistor R6, the fifth resistor R7, the sixth resistor R8, and the seventh resistor The resistance value of R9 should satisfy R6=R7=R8=R9=510Ω, and the eighth resistor R10 and the ninth resistor R11 in the low-pass filter circuit should also meet the requirements of the differential circuit balance characteristics, that is, R10=R11. The low-pass filter circuit can filter out part of the high-frequency noise before the signal enters the analog-to-digital conversion circuit, but in order to ensure that the differential electrical signal output by the detector will not lose effective information, the cut-off frequency f _p of the filter should be greater than that of InGaAs The output pixel clock frequency f _s of the SWIR detector is 5 times that of The signal conditioning filter circuit converts the single-ended signal into a differential signal, mainly to meet the interface requirements of the subsequent analog-to-digital conversion circuit, and to filter out noise interference as much as possible before the signal is converted to analog-to-digital.

The analog differential signal output by the signal conditioning filter circuit is converted through the high-resolution (N=14bit), high-speed (80MSPS) differential analog-to-digital converter of the analog-to-digital conversion circuit, and then the analog-to-digital conversion circuit outputs the parallel data to The data processing circuit performs digital filtering and parallel-to-serial conversion on the analog parallel digital signal sent by the analog-to-digital conversion circuit, and then packs the processed data into a required data format.

For example: InGaAs short-wave infrared detector pixel rate is 10Mhz, the output analog signal of a certain pixel is Vi+=1.7V, Vi-=1.3V, if the gain G of the differential single-ended conversion circuit is set to G=5, then the differential single-ended The output of the conversion circuit is Vs=2V, the signal conditioning filter circuit _Vvcm =1V, then the output of the signal conditioning filter circuit V+=2V, V-=0V, the dynamic range of the analog-to-digital conversion circuit is -2.5V～+2.5V , then the corresponding quantized digital signal after conversion is 6554, and each pixel can be re-sampled 8 times. After digital filtering, each pixel is restored to a corresponding 14bits data, and then converted into parallel and serialized and packaged into the required data format. The data of the above pixel can be transmitted to the corresponding terminal for display and further analysis.

According to the InGaAs short-wave infrared detector signal processing system designed in the present invention, when the detector output signal is 80% of the full scale, the actual system signal-to-noise ratio test result is shown in FIG. 4 . Figure 4 is the signal-to-noise ratio on the ordinate, and the pixel position on the abscissa. The solid line is the actual measurement result of the system signal-to-noise ratio, and the dotted line is the theoretical signal-to-noise ratio of the analog-to-digital converter. This value does not include the influence of other circuit noise in the system, that is, The maximum value of the system's theoretical signal-to-noise ratio. It can be seen from Fig. 4 that the measured signal-to-noise ratio of most pixels of the InGaAs short-wave infrared detector signal processing system designed based on the present invention can reach 70dB, which is close to the theoretical value of 74dB of the signal-to-noise ratio of the analog-to-digital converter.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims (10)

1. a kind of InGaAs short-wave infrareds detector signal processing system, it is characterised in that including：InGaAs short-wave infrareds are detected The single-ended change-over circuit of device, signal input part, difference, signal condition filter circuit, analog to digital conversion circuit, data processing circuit；Its Middle InGaAs short-wave infrareds detector, is responsible for the optical signal detected is converted into differential electric signal delivering to signal input part；Letter Number input includes the first source side resistance R1 and the second source side resistance R2；

Signal input part, by differential electric signal after the first source side resistance R1 and the second source side resistance R2 matchings, output and difference The differential electric signal of single-ended change-over circuit matching, is used as the input of the single-ended change-over circuit of difference, the first source side resistance R1 and second Source side resistance R2 one end is respectively connected to InGaAs short-wave infrared detector signal output ends, the first source side resistance R1 and the second source The resistance R2 other end is held as the input of the single-ended change-over circuit of difference；

The single-ended change-over circuit of difference, is converted to single-ended signal by the differential electric signal of input and delivers to signal condition filter circuit, and Differential electric signal to input realizes impedance matching, and the differential electric signal of input is amplified, while the single-ended conversion electricity of difference Road also serves as the interface of system master backup；

Signal condition filter circuit, is filtered and nurses one's health to the single-ended signal that the single-ended change-over circuit of difference is sent, obtain modulus Analog differential electric signal in change-over circuit input dynamic range, delivers to analog to digital conversion circuit；

Analog to digital conversion circuit, parallel data signal is converted to by the analog differential electric signal that signal condition filter circuit is sent, Deliver to data processing circuit；

Data processing circuit, digital filtering is realized to the data signal that analog to digital conversion circuit is sent and then parallel-serial conversion is carried out, obtained To corresponding serial data, and the data are packaged into required data format.

2. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 1, it is characterised in that：It is described The single-ended change-over circuit of difference include：First resistor R3, second resistance R4,3rd resistor R5 and difference single end operational amplifier (221), difference single end operational amplifier (221) includes differential input end 1+, differential input end 1-, differential input end 2+, difference Input 2-, output end Vs and equivalent input capacitance, differential input end 1+, differential input end 1- connect the first source electricity respectively R1 and the second source side resistance R2 one end is hindered, while the first source side resistance R1 and the second source side resistance R2 one end are also with difference list The equivalent input capacitance of operational amplifier (221) is held to be connected；

The ends of first resistor R3 mono- are connected to the input 2+ of difference single end operational amplifier (221), it is another with being connected to circuit, second The ends of resistance R4 mono- are connected to the input 2- of difference single end operational amplifier (221), it is another with being connected to circuit, 3rd resistor R5 mono- It is connected to the input 2- of difference single end operational amplifier (221), output of the other end with difference single end operational amplifier (221) Vs is held to be connected.

3. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 2, it is characterised in that：It is described Difference single end operational amplifier (221) be more than 750k Ω, input capacitance for input impedance and be less than 15pF, and it is zero defeated to possess power-off Go out the device of characteristic, difference single end operational amplifier (221) includes built-in equivalent input capacitance, the first source side resistance R1, the Two source side resistance R2 constitute a low-pass filter circuit with the equivalent input capacitance of difference single end operational amplifier (221).

4. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 1, it is characterised in that：It is described The first source side resistance R1, the second source side resistance R2 resistance be less than or equal to 50 Ω, in order to ensure circuit balancing, the first source electricity The resistance for hindering R1 and the second source side resistance R2 is equal.

5. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 2, it is characterised in that：It is described First resistor R3, second resistance R4,3rd resistor R5 value relatable need to meet R3 value and be equal to R4 and R5 parallel values.

6. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 2, it is characterised in that：It is described The gain of the single-ended change-over circuit of difference be

7. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 1, it is characterised in that：It is described Signal condition filter circuit include single-ended transfer difference circuit and low-pass filter circuit two parts；

Single-ended transfer difference circuit includes differential operational amplifier (231), the 4th resistance R6, the 5th resistance R7, the 6th resistance R8, the Seven resistance R9；

Low-pass filter circuit includes the 8th resistance R10, the 9th resistance R11 and electric capacity C1；

It is defeated that differential operational amplifier (231) includes in-phase input end, inverting input, output end in the same direction, reversed-phase output, common mode Enter to hold V_VCM；

A 4th resistance R6 end is connected to the output end V of difference single end operational amplifier (221)_s, the 4th resistance R6 another termination To the in-phase input end of differential operational amplifier (231), a 5th resistance R7 termination circuit, the 5th resistance R7 other end The inverting input of differential operational amplifier (231) is connected to, the 6th resistance R8 two ends are respectively connected to differential operational amplifier (231) in-phase input end and reversed-phase output, the 7th resistance R9 two ends are respectively connected to the anti-of differential operational amplifier (231) Phase input and in-phase output end；The common mode input V of differential operational amplifier (231)_VCMIt is connected with analog to digital conversion circuit；

8th resistance R10 one end is connected to the reversed-phase output of differential operational amplifier (231), and on the one hand the other end is used as modulus One end of the inverting input of change-over circuit, on the other hand connection electric capacity C1, the 9th resistance R11 one end is connected to calculus of differences and put On the one hand the in-phase output end of big device (231), the other end as the in-phase input end of analog to digital conversion circuit, on the other hand connects electricity Hold the C1 other end.

8. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 7, it is characterised in that：It is described Resistance R6=R7=R8=R9=510 Ω.

9. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 7, it is characterised in that：It is described The cut-off frequency f of low-pass filter circuit_pMore than the output pixel clock frequency f of InGaAs short-wave infrared detectors_s5 times, i.e.,And R10=R11.

10. a kind of InGaAs short-wave infrareds detector signal processing system according to claim 1, it is characterised in that：Institute The analog to digital conversion circuit stated includes high-resolution, high-speed-differential analog-digital converter, i.e. resolution, N=14bits, high-speed-differential mould The switching rate of number converter is 80MSPS.