Signal amplitude gain control circuit and method during photoelectric conversion

Abstract

The invention relates to the technical field of optical communication, and discloses a signal amplitude gain control circuit and method during photoelectric conversion, and the circuit comprises a photoelectric conversion circuit, a signal gain circuit, an adjustable attenuation circuit, a balance-unbalance converter, a radio frequency detection circuit, and a central controller. Wherein the balance-unbalance converter is used for converting the attenuated differential radio-frequency signals into A and B paths of completely equivalent single-ended radio-frequency signals, and the A path of single-ended radio-frequency signals serve as radio-frequency output signals; the radio frequency detection circuit is used for detecting the output amplitude of the B-path single-ended radio frequency signal; the central controller is used for outputting an attenuation control signal through a proportional-integral-differential control method according to the receiving optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit so as to control the adjustable attenuation circuit and control the output amplitude of the radio frequency output signal within a preset range; therefore, accurate control of the output amplitude of each frequency band signal is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a signal amplitude gain control circuit and method during photoelectric conversion. Background Art

[0002] According to the requirements of CATV (cable television), the analog video and voice signals are transmitted to users through optical fiber downlink transmission. 210 FM signals can be transmitted, among which the frequency band ranges from 47MHz to 870MHz. The output amplitude varies according to the requirements of each device, and is generally required to be controlled at 19dbmV-23dbmV. Because according to the protocol requirements, the average power of the input light is +2dbm to -8dbm, and the modulation of the transmitter is also different, and the responsiveness of the photodetector is also different. Therefore, in order to keep the amplitude of the restored output electrical signal within a fixed range, it is necessary to realize the automatic adjustment and control of the amplitude of the receiving end electrical signal.

[0003] At present, many optical receiver manufacturers use optical AGC (Automatic Gain Control) based on the received optical power to achieve output level stability. The function of optical AGC means that the overall gain of the optical receiver is controlled by the received optical power, and the output level can be kept basically unchanged regardless of how it changes within the optical power control range. Since the received optical power dBm and the output level dBμV change in a 1:2 relationship, within the normal range, if the optical power increases by 1dB, the output level increases by 2dB. The principle of optical AGC is to change the attenuation value of the adjustable attenuator synchronously with the change of optical power. If the optical power decreases by 1dB, the attenuation value of the adjustable attenuator is reduced by 2dB, thereby ensuring the stability of its output level. The larger the controllable range of optical AGC, the greater the gain of the inter-stage amplification, so as to compensate for the problem of reduced output signal caused by reduced optical power.

[0004] The existing optical AGC circuit structure is as follows Figure 1 As shown, this circuit design has the following problems: (1) Since the optical AGC mainly controls the output amplitude by sampling the average power, if the input light power is the same, the optical modulation index M is different, and the output amplitude may also be greatly different. The calculation formula of the optical modulation index M is as follows: M=(Θ h -Θ l ) / ( Θ h +Θ l ) Among them, Θ h is the instantaneous maximum power of the modulated optical signal, Θ l It is the instantaneous minimum power of the modulated optical signal.

[0005] (2) Since the signal frequency band is 46MHz-870MHz, the attenuation response of signals of different frequencies passing through the amplifier and attenuation circuit will be quite different. If the output amplitude is controlled only by the size of the optical power, the final output of signals of different frequencies will have a large amplitude deviation. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a signal amplitude gain control circuit and method during photoelectric conversion, which combines optical AGC and electrical AGC and adopts a coarse adjustment plus fine adjustment algorithm to take into account both control time efficiency and control accuracy.

[0007] The technical solution adopted by the present invention is as follows: A signal amplitude gain control circuit for photoelectric conversion, comprising: A photoelectric conversion circuit is configured to convert a target optical signal into an AC analog current signal; A signal gain circuit, configured to convert the AC analog current signal into a voltage signal, and amplify the voltage signal into a differential radio frequency signal with a preset gain; An adjustable attenuation circuit, configured to perform amplitude attenuation control on the differential radio frequency signal; A balun is configured to convert the attenuated differential RF signal into two completely equivalent single-ended RF signals, A and B, wherein the single-ended RF signal A is used as the RF output signal; The radio frequency detection circuit is configured to detect the output amplitude of the single-ended radio frequency signal of channel B; The central controller is configured to output an attenuation control signal to control the adjustable attenuation circuit through a proportional-integral-differential control method based on the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit, thereby controlling the output amplitude of the radio frequency output signal within a preset range.

[0008] Further, the outputting of the attenuation control signal based on the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit through a proportional-integral-differential control method to control the adjustable attenuation circuit includes: Based on the current received optical power sampling current value of the photoelectric conversion circuit, the current received optical power sampling current value is compared with the preset optical power sampling current value, and the attenuation of the adjustable attenuation circuit is adjusted proportionally; Based on the output amplitude detected by the RF detection circuit, the difference between the output amplitude sampling value and the output amplitude setting value is calculated, and the adjustable attenuation circuit is adjusted based on the proportional-integral-differential control method so that the output amplitude sampling value is within the output amplitude setting range.

[0009] Furthermore, the signal gain circuit includes a transimpedance amplifier and a radio frequency amplifier, the transimpedance amplifier is used to convert the AC analog current signal into a voltage signal, and the radio frequency amplifier is used to amplify the voltage signal into a differential radio frequency signal with a preset gain; the signal input end of the transimpedance amplifier is connected to the signal output end of the photoelectric conversion circuit, the signal output end of the transimpedance amplifier is connected to the signal input end of the radio frequency amplifier, and the signal output end of the radio frequency amplifier is connected to the signal input end of the adjustable attenuation circuit.

[0010] Furthermore, the adjustable attenuation circuit includes a radio frequency diode network, a signal input end of the radio frequency diode network is connected to a signal gain circuit and a signal output end of a central controller, and a signal output end of the radio frequency diode network is connected to a signal input end of a balanced-unbalanced converter.

[0011] Furthermore, the photoelectric conversion circuit includes a photodiode, and a signal output end of the photodiode is connected to a signal gain circuit and a signal input end of a central controller.

[0012] A method for controlling signal amplitude gain during photoelectric conversion, comprising: The target optical signal is converted into an AC analog current signal through a photoelectric conversion circuit; The AC analog current signal is converted into a voltage signal through a signal gain circuit, and amplified into a differential radio frequency signal with a preset gain; Performing amplitude attenuation control on the differential radio frequency signal through an adjustable attenuation circuit; The attenuated differential radio frequency signal is converted into two completely equivalent single-ended radio frequency signals A and B by a balanced-unbalanced converter, wherein the single-ended radio frequency signal A is used as the radio frequency output signal; The output amplitude of the single-ended RF signal of channel B is detected by the RF detection circuit; The received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit are sampled by a central controller, and an attenuation control signal is output through a proportional-integral-differential control method to control the adjustable attenuation circuit, thereby controlling the output amplitude of the radio frequency output signal within a preset range.

[0013] Furthermore, the central controller samples the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit, and outputs an attenuation control signal to control the adjustable attenuation circuit through a proportional-integral-differential control method, including: Based on the current received optical power sampling current value of the photoelectric conversion circuit, the current received optical power sampling current value is compared with the preset optical power sampling current value, and the attenuation of the adjustable attenuation circuit is adjusted proportionally; Based on the output amplitude detected by the RF detection circuit, the difference between the output amplitude sampling value and the output amplitude setting value is calculated, and the adjustable attenuation circuit is adjusted based on the proportional-integral-differential control method so that the output amplitude sampling value is within the output amplitude setting range.

[0014] Furthermore, the signal gain circuit includes a transimpedance amplifier and a radio frequency amplifier, the transimpedance amplifier is used to convert the AC analog current signal into a voltage signal, and the radio frequency amplifier is used to amplify the voltage signal into a differential radio frequency signal with a preset gain; the signal input end of the transimpedance amplifier is connected to the signal output end of the photoelectric conversion circuit, the signal output end of the transimpedance amplifier is connected to the signal input end of the radio frequency amplifier, and the signal output end of the radio frequency amplifier is connected to the signal input end of the adjustable attenuation circuit.

[0015] Furthermore, the adjustable attenuation circuit includes a radio frequency diode network, a signal input end of the radio frequency diode network is connected to a signal gain circuit and a signal output end of a central controller, and a signal output end of the radio frequency diode network is connected to a signal input end of a balanced-unbalanced converter.

[0016] Furthermore, the photoelectric conversion circuit includes a photodiode, and a signal output end of the photodiode is connected to a signal gain circuit and a signal input end of a central controller.

[0017] The beneficial effects of the present invention are: 1. The present invention utilizes a balanced-unbalanced converter and a radio frequency detection circuit to achieve precise control of the sampled radio frequency amplitude without interfering with the original radio frequency output.

[0018] 2. The present invention does not completely abandon the traditional optical AGC sampling method, but combines optical AGC with electrical AGC, adopts a coarse adjustment plus fine adjustment algorithm, and takes into account both control time efficiency and control accuracy.

[0019] 3. The present invention can solve the problems of poor control accuracy and large deviation of traditional optical AGC, and can achieve precise control of the signal output amplitude of each frequency band.

[0020] 4. The present invention adopts a coarse adjustment plus fine adjustment method, which effectively shortens the time required for the proportional-integral-differential control method and improves the efficiency and real-time performance of signal control. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the existing optical AGC circuit structure.

[0022] Figure 2 It is a schematic diagram of the structure of a signal amplitude gain control circuit during photoelectric conversion according to Embodiment 1 of the present invention.

[0023] Figure 3 This is a control flow chart of the central controller of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0025] Example 1 Since the optical AGC mainly controls the output amplitude by sampling the average power, if the input optical power is the same, the output amplitude may also be greatly different if the optical modulation index M is different. In addition, since the attenuation response of signals of different frequencies passing through the amplifier and attenuation circuit will be greatly different, if the output amplitude is controlled only by the size of the optical power, the final output of signals of different frequencies will have a large amplitude deviation.

[0026] Based on this, this embodiment provides a signal amplitude gain control circuit during photoelectric conversion, such as Figure 2 As shown, it includes a photoelectric conversion circuit, a signal gain circuit, an adjustable attenuation circuit, a balanced-unbalanced converter, a radio frequency detection circuit and a central controller, wherein: The photoelectric conversion circuit is used to convert the target optical signal into an AC analog current signal.

[0027] The signal gain circuit is used to convert the AC analog current signal into a voltage signal and amplify it into a differential radio frequency signal with a preset gain.

[0028] The adjustable attenuation circuit is used to control the amplitude attenuation of the differential radio frequency signal.

[0029] The balanced-unbalanced converter (also called a balancer) can realize the conversion from differential signals to single-ended signals. It is specifically used to convert the attenuated differential RF signal into two completely equivalent single-ended RF signals A and B. The single-ended RF signal on channel A is used as the RF output signal and can be output to the TV playback terminal through the RF interface.

[0030] The radio frequency detection circuit is used to detect the output amplitude of the single-ended radio frequency signal of channel B.

[0031] The central controller is used to output an attenuation control signal to control the adjustable attenuation circuit through a proportional-integral-differential control method according to the received optical power of the photoelectric conversion circuit and the output amplitude detected by the RF detection circuit, so as to control the output amplitude of the RF output signal within a preset range, thereby achieving stable control of the output amplitude.

[0032] It should be noted that, by using a balanced-unbalanced converter and a radio frequency detection circuit, this embodiment can achieve precise control of the sampling radio frequency amplitude without interfering with the original radio frequency output.

[0033] Preferably, if Figure 3 As shown, the central controller uses coarse adjustment + fine adjustment to control: Coarse adjustment: based on the current received optical power sampling current value of the photoelectric conversion circuit, compare it with the preset optical power sampling current value, and adjust the attenuation of the adjustable attenuation circuit in proportion; Fine adjustment: Based on the output amplitude detected by the RF detection circuit, the difference between the output amplitude sampling value and the output amplitude setting value is calculated, and the adjustable attenuation circuit is adjusted based on the proportional-integral-differential control method to make the output amplitude sampling value within the output amplitude setting range.

[0034] It should be noted that this embodiment combines optical AGC and electrical AGC and adopts a coarse adjustment + fine adjustment method, which effectively shortens the time required for the proportional-integral-differential control method and improves the efficiency and real-time performance of signal control.

[0035] Preferably, the signal gain circuit includes a transimpedance amplifier and a radio frequency amplifier, the transimpedance amplifier is used to convert the AC analog current signal into a voltage signal, and the radio frequency amplifier is used to amplify the voltage signal into a differential radio frequency signal with a preset gain. The signal input end of the transimpedance amplifier is connected to the signal output end of the photoelectric conversion circuit, the signal output end of the transimpedance amplifier is connected to the signal input end of the radio frequency amplifier, and the signal output end of the radio frequency amplifier is connected to the signal input end of the adjustable attenuation circuit.

[0036] Preferably, the adjustable attenuation circuit may adopt a radio frequency diode network, the signal input end of the radio frequency diode network is connected to the signal gain circuit and the signal output end of the central controller, and the signal output end of the radio frequency diode network is connected to the signal input end of the balanced-unbalanced converter.

[0037] Preferably, the photoelectric conversion circuit may adopt a photodiode, and the signal output end of the photodiode is connected to the signal gain circuit and the signal input end of the central controller.

[0038] Example 2 This embodiment provides a method for controlling signal amplitude gain during photoelectric conversion, including: The target optical signal is converted into an AC analog current signal through a photoelectric conversion circuit; The AC analog current signal is converted into a voltage signal through a signal gain circuit, and amplified into a differential RF signal with a preset gain; Amplitude attenuation of the differential radio frequency signal is controlled by an adjustable attenuation circuit; The attenuated differential RF signal is converted into two completely equivalent single-ended RF signals A and B through a balanced-unbalanced converter, wherein the single-ended RF signal A is used as the RF output signal; The output amplitude of the single-ended RF signal of channel B is detected by the RF detection circuit; The central controller samples the received optical power of the photoelectric conversion circuit and the output amplitude detected by the RF detection circuit, and outputs an attenuation control signal through a proportional-integral-differential control method to control the adjustable attenuation circuit, thereby controlling the output amplitude of the RF output signal within a preset range.

[0039] Preferably, the central controller samples the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit, and outputs an attenuation control signal through a proportional-integral-differential control method to control the adjustable attenuation circuit, including: Based on the current received optical power sampling current value of the photoelectric conversion circuit, the current received optical power sampling current value is compared with the preset optical power sampling current value, and the attenuation of the adjustable attenuation circuit is adjusted proportionally; Based on the output amplitude detected by the RF detection circuit, the difference between the output amplitude sampling value and the output amplitude setting value is calculated, and the adjustable attenuation circuit is adjusted based on the proportional-integral-differential control method to make the output amplitude sampling value within the output amplitude setting range.

[0040] Preferably, the signal gain circuit includes a transimpedance amplifier and a radio frequency amplifier, the transimpedance amplifier is used to convert the AC analog current signal into a voltage signal, and the radio frequency amplifier is used to amplify the voltage signal into a differential radio frequency signal with a preset gain; the signal input end of the transimpedance amplifier is connected to the signal output end of the photoelectric conversion circuit, the signal output end of the transimpedance amplifier is connected to the signal input end of the radio frequency amplifier, and the signal output end of the radio frequency amplifier is connected to the signal input end of the adjustable attenuation circuit.

[0041] Preferably, the adjustable attenuation circuit comprises a radio frequency diode network, a signal input end of the radio frequency diode network is connected to the signal gain circuit and the signal output end of the central controller, and a signal output end of the radio frequency diode network is connected to the signal input end of the balanced-unbalanced converter.

[0042] Preferably, the photoelectric conversion circuit comprises a photodiode, and a signal output terminal of the photodiode is connected to a signal gain circuit and a signal input terminal of the central controller.

[0043] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

Claims

1. A signal amplitude gain control circuit for photoelectric conversion, characterized in that: include: A photoelectric conversion circuit is configured to convert a target optical signal into an AC analog current signal; A signal gain circuit, configured to convert the AC analog current signal into a voltage signal, and amplify the voltage signal into a differential radio frequency signal with a preset gain; An adjustable attenuation circuit, configured to perform amplitude attenuation control on the differential radio frequency signal; A balun is configured to convert the attenuated differential RF signal into two completely equivalent single-ended RF signals, A and B, wherein the single-ended RF signal A is used as the RF output signal; The radio frequency detection circuit is configured to detect the output amplitude of the single-ended radio frequency signal of channel B; The central controller is configured to output an attenuation control signal to control the adjustable attenuation circuit through a proportional-integral-differential control method based on the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit, thereby controlling the output amplitude of the radio frequency output signal within a preset range.

2. The signal amplitude gain control circuit for photoelectric conversion according to claim 1, characterized in that: The method outputs an attenuation control signal based on the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit to control the adjustable attenuation circuit through a proportional-integral-differential control method, including: Based on the current received optical power sampling current value of the photoelectric conversion circuit, the current received optical power sampling current value is compared with the preset optical power sampling current value, and the attenuation of the adjustable attenuation circuit is adjusted proportionally; Based on the output amplitude detected by the RF detection circuit, the difference between the output amplitude sampling value and the output amplitude setting value is calculated, and the adjustable attenuation circuit is adjusted based on the proportional-integral-differential control method so that the output amplitude sampling value is within the output amplitude setting range.

3. The signal amplitude gain control circuit for photoelectric conversion according to claim 1, characterized in that: The signal gain circuit includes a transimpedance amplifier and a radio frequency amplifier, the transimpedance amplifier is used to convert an AC analog current signal into a voltage signal, and the radio frequency amplifier is used to amplify the voltage signal into a differential radio frequency signal with a preset gain; the signal input end of the transimpedance amplifier is connected to the signal output end of the photoelectric conversion circuit, the signal output end of the transimpedance amplifier is connected to the signal input end of the radio frequency amplifier, and the signal output end of the radio frequency amplifier is connected to the signal input end of the adjustable attenuation circuit.

4. The signal amplitude gain control circuit for photoelectric conversion according to claim 1, characterized in that: The adjustable attenuation circuit comprises a radio frequency diode network, a signal input end of the radio frequency diode network is connected to a signal gain circuit and a signal output end of a central controller, and a signal output end of the radio frequency diode network is connected to a signal input end of a balanced-unbalanced converter.

5. The signal amplitude gain control circuit for photoelectric conversion according to claim 1, characterized in that: The photoelectric conversion circuit comprises a photodiode, and a signal output end of the photodiode is connected to a signal gain circuit and a signal input end of a central controller.

6. A method for controlling signal amplitude gain during photoelectric conversion, characterized in that: include: The target optical signal is converted into an AC analog current signal through a photoelectric conversion circuit; The AC analog current signal is converted into a voltage signal through a signal gain circuit, and amplified into a differential radio frequency signal with a preset gain; Performing amplitude attenuation control on the differential radio frequency signal through an adjustable attenuation circuit; The attenuated differential radio frequency signal is converted into two completely equivalent single-ended radio frequency signals A and B by a balanced-unbalanced converter, wherein the single-ended radio frequency signal A is used as the radio frequency output signal; The output amplitude of the single-ended RF signal of channel B is detected by the RF detection circuit; The received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit are sampled by a central controller, and an attenuation control signal is output through a proportional-integral-differential control method to control the adjustable attenuation circuit, thereby controlling the output amplitude of the radio frequency output signal within a preset range.

7. The method for controlling signal amplitude gain during photoelectric conversion according to claim 6, characterized in that: The method of sampling the received optical power of the photoelectric conversion circuit and the output amplitude detected by the radio frequency detection circuit through the central controller, and outputting an attenuation control signal to control the adjustable attenuation circuit through a proportional-integral-differential control method, comprises: Based on the current received optical power sampling current value of the photoelectric conversion circuit, the current received optical power sampling current value is compared with the preset optical power sampling current value, and the attenuation of the adjustable attenuation circuit is adjusted proportionally; Based on the output amplitude detected by the RF detection circuit, the difference between the output amplitude sampling value and the output amplitude setting value is calculated, and the adjustable attenuation circuit is adjusted based on the proportional-integral-differential control method so that the output amplitude sampling value is within the output amplitude setting range.

8. The method for controlling signal amplitude gain during photoelectric conversion according to claim 6, characterized in that: The signal gain circuit includes a transimpedance amplifier and a radio frequency amplifier, the transimpedance amplifier is used to convert an AC analog current signal into a voltage signal, and the radio frequency amplifier is used to amplify the voltage signal into a differential radio frequency signal with a preset gain; the signal input end of the transimpedance amplifier is connected to the signal output end of the photoelectric conversion circuit, the signal output end of the transimpedance amplifier is connected to the signal input end of the radio frequency amplifier, and the signal output end of the radio frequency amplifier is connected to the signal input end of the adjustable attenuation circuit.

9. The method for controlling signal amplitude gain during photoelectric conversion according to claim 6, characterized in that: The adjustable attenuation circuit comprises a radio frequency diode network, a signal input end of the radio frequency diode network is connected to a signal gain circuit and a signal output end of a central controller, and a signal output end of the radio frequency diode network is connected to a signal input end of a balanced-unbalanced converter.

10. The method for controlling signal amplitude gain during photoelectric conversion according to claim 6, characterized in that: The photoelectric conversion circuit comprises a photodiode, and a signal output end of the photodiode is connected to a signal gain circuit and a signal input end of a central controller.

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