Optical detection circuit, wireless communication base station and system, and signal processing method

Abstract

Embodiments of the present application relate to the technical field of wireless communications, and provide an optical detection circuit, a wireless communication base station and system, and a signal processing method, for use in improving the fallback efficiency of the optical detection circuit. The optical detection circuit comprises a main circuit and an auxiliary circuit, the main circuit is closed, and the auxiliary circuit is closed under the control of a power amplifier only when the power is larger than a set value, so that a turn-on voltage effect similar to that of a triode can be achieved, and the output power of the optical detection circuit is improved. Moreover, an impedance modulation network is used to carry out output load modulation on an optical detector in the main circuit and an optical detector in the auxiliary circuit, to achieve dynamic load transformation from a fallback point to a maximum output point, so that the optical detector in the main circuit and the optical detector in the auxiliary circuit can maintain high output efficiency in the range between the maximum power point and the fallback point, thereby achieving the purpose of improving the fallback efficiency of the optical detection circuit.

Description

Optical detection circuit, wireless communication base station and system, and signal processing method

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 16, 2023, with application number 202311540603.6 and application name “Optical detection circuit, wireless communication base station and system, signal processing method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of wireless communication technology, and in particular to a light detection circuit, a wireless communication base station and system, and a signal processing method. Background Art

[0003] Entering the era of fifth-generation (5G) communications systems, the application of massive multiple input, multiple output (Massive MIMO) antenna technology has significantly increased the capacity and peak data rates of wireless base stations. Compared to the high-power outdoor macro base stations of the fourth-generation (4G) communications systems, 5G base stations based on Massive MIMO's active antenna unit (AAU) architecture eliminate physical feeder ports, increase the number of channels, and enhance antenna directional gain. This reduces the required single-channel RF output power to less than 10W while maintaining the same coverage range. As operating frequency bands expand from sub-6GHz to higher frequency bands and Massive MIMO technology continues to develop, the number of channels contained in a single AAU will increase, further reducing the single-channel RF output power to the hundreds of milliwatts.

[0004] RF photonic base stations utilize optoelectronic fusion technology to address the performance bottlenecks of purely electric systems, thereby enabling ultra-wideband, miniaturized, and low-power wireless communication systems. When the RF output power of a single channel is reduced to the hundreds of milliwatts, a high-power photodiode (HPD) directly driven antenna solution based on an RF photonic architecture offers significant size and power consumption advantages over traditional power amplifier (PA) solutions. This architecture not only simplifies the RF link and power supply solution, but also, thanks to the HPD's inherent wide bandwidth, enables ultra-wideband RF headends. However, HPD's fallback efficiency has been a significant factor limiting its commercial adoption.

[0005] Summary of the Invention

[0006] Embodiments of the present application provide a light detection circuit, a wireless communication base station and system, and a signal processing method for improving the fallback efficiency of the light detection circuit.

[0007] To achieve the above objectives, this application adopts the following technical solutions:

[0008] According to a first aspect of an embodiment of the present application, there is provided an optical detection circuit, comprising: an optical input terminal, an RF output terminal, a first branch, a second branch, and an impedance modulation network. The optical input terminal is used to input an optical signal, and the optical signal includes a first optical signal and a second optical signal. The first branch includes a first optical detector, and the first optical detector is used to receive the first optical signal and output a first RF signal. The second branch includes a second optical detector and a first power amplifier, and the second detector is used to receive the second optical signal and output a second RF signal; the first power amplifier is coupled between the second optical detector and the impedance modulation network, and is used to amplify the second RF signal and control the on-off between the second optical detector and the impedance modulation network. The impedance modulation network is used to perform output impedance transformation on the first optical detector and the second optical detector, and couple the output terminal of the first optical detector and the output terminal of the second optical detector to the RF output terminal.

[0009] In the optical detection circuit provided by the embodiments of the present application, a first optical detector and a second optical detector are connected in parallel, and the connectivity of the branch containing the second optical detector depends on whether the second RF signal is greater than the threshold turn-on voltage of the first power amplifier PA1. This circuit structure, in which the branch containing the first optical detector is continuously conductive and the branch containing the second optical detector is only conductive when the second RF signal reaches a set peak, achieves a turn-on voltage effect similar to that of a transistor, thereby increasing the output power of the optical detection circuit. Furthermore, the use of an impedance modulation network to combine the branches containing the first and second optical detectors achieves a load modulation effect when the input power varies, thereby achieving dynamic load conversion from the back-off point to the maximum output point. This facilitates maintaining high output efficiency for both the first and second optical detectors within the range between the maximum power point and the back-off point, thereby improving the back-off efficiency of the optical detection circuit.

[0010] In one possible implementation, the first power amplifier is specifically configured to disconnect the second optical detector from the impedance modulation network when the second RF signal is less than a set value, and to connect the second optical detector to the impedance modulation network when the second RF signal is greater than or equal to the set value. This allows the optical detection circuit to operate at its optimal efficiency when the second optical detection branch is disabled (when the input RF signal power is low). When the second optical detection branch is enabled (when the input RF signal power is high), the optical detection circuit operates at its optimal output power.

[0011] In one possible implementation, the optical detection circuit further includes an optical attenuator, and the second optical signal is attenuated by the optical attenuator and then transmitted to the second optical detector. By adjusting the power of the second optical signal with the optical attenuator, the power of the first optical signal can be greater than that of the second optical signal, and the amplitude of the corresponding output first RF signal can be greater than that of the second RF signal. After the second RF signal is amplified by the first power amplifier, the amplitude of the RF signal output by the first branch can be equal to the amplitude of the RF signal output by the second branch, thereby reducing problems such as reduced efficiency and deteriorated signal quality caused by inconsistent amplitudes when the two signals are combined. Furthermore, the optical attenuator has high accuracy in adjusting the power of the optical signal.

[0012] In one possible implementation, the optical detection circuit further includes an electrical attenuator coupled between the second optical detector and the first power amplifier. By adjusting the power of the second RF signal with the electrical attenuator, the amplitude of the first RF signal can be made greater than the amplitude of the second RF signal. After the second RF signal is amplified by the first power amplifier, the amplitude of the RF signal output by the first branch can be made equal to the amplitude of the RF signal output by the second branch, thereby reducing problems such as reduced efficiency and degraded signal quality caused by inconsistent amplitudes when the two signals are synthesized. Furthermore, the electrical attenuator is easy to integrate and has low cost.

[0013] In one possible implementation, the optical detection circuit further includes a first optical delay device; the first optical signal is phase-shifted by the first optical delay device and then transmitted to the first optical detector. By placing the first optical delay device before the first optical detector, the phase of the first optical signal is adjusted through optical modulation, enabling the optical detection circuit to support phase modulation of broadband signals. The optical delay device structure has high phase adjustment accuracy, wide bandwidth, and fast switching capabilities.

[0014] In one possible implementation, the optical detection circuit further includes a second optical delay device; the second optical signal is phase-shifted by the second optical delay device and then transmitted to the second optical detector. By placing the second optical delay device before the second optical detector and adjusting the phase of the second optical signal through optical modulation, the optical detection circuit supports phase modulation of broadband signals. The optical delay device structure has high phase adjustment accuracy, wide bandwidth, and supports fast multi-band true delay switching.

[0015] In one possible implementation, the optical detection circuit further includes a first phase shifter coupled between the first optical detector and the impedance modulation network. By placing the first phase shifter after the first optical detector and electrically adjusting the phase of the first RF signal, the optical detection circuit supports phase adjustment of broadband signals, while also simplifying and reducing the cost of integrating the electrical phase shifter.

[0016] In one possible implementation, the optical detection circuit further includes a second phase shifter coupled between the second optical detector and the first power amplifier. By providing the second phase shifter after the second optical detector, the phase of the second RF signal is electrically adjusted, enabling the optical detection circuit to support phase adjustment of broadband signals. Furthermore, the integration of the electrical phase shifter is simplified and cost-effective.

[0017] In one possible implementation, the optical detection circuit further includes a third optical detector and a second power amplifier; the third optical detector is configured to receive a third optical signal and output a third radio frequency signal; and the second power amplifier is coupled between the third optical detector and the impedance modulation network and is configured to control the on / off state between the third optical detector and the impedance modulation network. By providing multiple conditionally enabled circuits within the optical detection circuit, the optical detection circuit can have multiple efficiency optima within the backoff interval, thereby improving the average efficiency of the entire backoff interval. For example, the optical detection circuit has an efficiency optimum when the first branch operates independently, an efficiency optimum when the first and second branches operate synchronously, an efficiency optimum when the first and third branches operate synchronously, and an efficiency optimum when the first, second, and third branches operate synchronously.

[0018] In one possible implementation, the first power amplifier has a different threshold voltage than the second power amplifier, so that the second and third light detector branches provide different efficiency optima, thereby improving the average efficiency in the backoff interval.

[0019] In one possible implementation, the power of the first optical signal is equal to the power of the second optical signal. In this way, the first optical signal and the second optical signal can be generated using mature devices, without the need to develop new devices, and are easy to implement.

[0020] In one possible implementation, the power of the first optical signal is greater than the power of the second optical signal. This eliminates the need for the optical detection circuit to include the aforementioned power adjustment structure to boost the power of the first RF signal. By simply including a phase adjustment structure, the first and second branches can output RF signals of equal amplitude and phase, simplifying the structure of the optical detection circuit.

[0021] In one possible implementation, the optical detection circuit further includes an optical splitter; the optical splitter is configured to receive an optical signal and split the optical signal into a first optical signal and a second optical signal. In this case, the optical detection circuit only requires a single optical input terminal, with the optical splitter performing power splitting of the optical signal and outputting the first and second optical signals. Compared to requiring two independent optical input terminals, this simplifies the number of input interfaces in the optical detection circuit, achieving increased power and efficiency without increasing the cost and complexity of the optical detection circuit.

[0022] In one possible implementation, the optical detection circuit further includes an impedance matching network coupled between the second optical detector and the first power amplifier. The impedance matching network can match the output impedance of the second optical detector with the input impedance of the first power amplifier to reduce excessive insertion loss caused by impedance mismatch when the second optical detector and the first power amplifier are cascaded.

[0023] In one possible implementation, the light detection circuit further includes a first capacitor and a second capacitor; the first capacitor is coupled between the first light detector and the impedance modulation network, and the second capacitor is coupled between the second light detector and the first power amplifier. The first capacitor and the second capacitor can filter out DC signals to remove interference signals.

[0024] In a second aspect of an embodiment of the present application, a photoelectric conversion module is provided, comprising a light detection circuit and an electro-optical conversion circuit; the light detector is used to convert a received light signal into an electrical signal, and the electro-optical conversion circuit is used to convert a received electrical signal into an optical signal; the light detection circuit comprises any light detection circuit of the first aspect.

[0025] In a third aspect of the embodiments of the present application, a photoelectric conversion chip is provided. The photoelectric conversion chip can be a bare chip, a packaged bare chip, or a chip system comprising multiple chips (bare chips or packaged chips). The photoelectric conversion chip includes a light detection circuit and an electro-optical conversion circuit; the light detector is configured to convert a received light signal into an electrical signal, and the electro-optical conversion circuit is configured to convert a received electrical signal into an optical signal; the light detection circuit includes any of the light detection circuits described in the first aspect.

[0026] According to a fourth aspect of an embodiment of the present application, a wireless communication base station is provided, comprising a photoelectric conversion module and an antenna unit, wherein the photoelectric conversion module is coupled to the antenna unit; the photoelectric conversion module comprises the photoelectric conversion module of the second aspect or the photoelectric conversion chip of the third aspect.

[0027] According to a fifth aspect of an embodiment of the present application, a wireless communication system is provided, comprising a baseband processing unit, a wireless communication base station and an optical fiber, wherein the baseband processing unit and the wireless communication base station are connected via the optical fiber; the wireless communication base station comprises the wireless communication base station according to the fourth aspect.

[0028] In a sixth aspect of an embodiment of the present application, a signal processing method is provided, comprising: a first optical detector receives a first optical signal and performs photoelectric conversion on the first optical signal to generate a first radio frequency signal; a second optical detector receives a second optical signal and performs photoelectric conversion on the second optical signal to generate a second radio frequency signal; a first power amplifier is turned on or off under the control of the second radio frequency signal, and amplifies the second radio frequency signal when the first power amplifier is turned on; an impedance modulation network performs output impedance transformation on the first optical detector and the second optical detector, and combines the first radio frequency signal and the amplified second radio frequency signal for output. The beneficial effects of the signal processing method provided in the embodiment of the present application are the same as those of the above-mentioned optical detection circuit, and will not be repeated here.

[0029] In one possible implementation, the first power amplifier is turned off when the second RF signal is less than a set value and turned on when the second RF signal is greater than or equal to the set value. This allows the first photodetector to operate at its optimal efficiency point when the second RF signal is low. When the second RF signal is high, both the first and second photodetectors operate at their optimal output power points.

[0030] In a possible implementation, the signal processing method further includes: performing phase sum modulation on the first optical signal, which helps ensure that the first radio frequency signal and the amplified second radio frequency signal are radio frequency signals of equal amplitude and phase, thereby reducing loss.

[0031] In one possible implementation, the signal processing method further includes: performing phase and / or amplitude modulation on the second optical signal, which helps ensure that the first RF signal and the amplified second RF signal have equal amplitude and phase, thereby reducing loss.

[0032] In a possible implementation, the signal processing method further includes: performing phase modulation on the first radio frequency signal, which helps ensure that the first radio frequency signal and the amplified second radio frequency signal are radio frequency signals of equal amplitude and phase, thereby reducing loss.

[0033] In one possible implementation, the signal processing method further includes: performing phase and / or amplitude modulation on the second RF signal. This helps ensure that the first RF signal and the amplified second RF signal have equal amplitude and phase, thereby reducing losses.

[0034] In a possible implementation, the signal processing method further includes: receiving an optical signal, and processing the optical signal to generate a first optical signal and a second optical signal. In this way, only one optical signal can be received, simplifying the optical receiving path. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is an architecture diagram of a wireless communication system provided in an embodiment of the present application;

[0036] FIG2 is an architecture diagram of a wireless communication base station provided in an embodiment of the present application;

[0037] FIG3 is a graph showing the relationship between the power conversion efficiency and the output power of a high-power photodetector provided in an embodiment of the present application;

[0038] FIG4 is a schematic diagram of the topological structure of a balanced photodetector provided in an embodiment of the present application;

[0039] FIG5 is a schematic diagram of a topological structure of a light detection circuit provided in an embodiment of the present application;

[0040] FIG6 is a graph showing a change in efficiency versus input power according to an embodiment of the present application;

[0041] 7A and 7B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application;

[0042] 8A and 8B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application;

[0043] 9A and 9B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application;

[0044] 10A and 10B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application;

[0045] FIG11 is a schematic diagram of a topological structure of a light detection circuit provided in an embodiment of the present application;

[0046] 12A-12C are schematic diagrams of the topological structure of a light detection circuit provided in an embodiment of the present application;

[0047] FIG13 is a schematic structural diagram of a first light detector provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0049] Hereinafter, the terms "second," "first," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature qualified as "second," "first," etc., may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0050] In addition, in the embodiments of the present application, directional terms such as "up", "down", "left", and "right" may be defined including but not limited to the orientation relative to the schematic placement of the components in the drawings. It should be understood that these directional terms may be relative concepts, which are used for relative descriptions and clarifications, and may change accordingly according to changes in the orientation of the components in the drawings.

[0051] In the embodiments of this application, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, "connection" can mean fixed connection, detachable connection, or integration; it can mean direct connection or indirect connection through an intermediate medium. In addition, the term "coupling" can mean direct electrical connection or indirect electrical connection through an intermediate medium. The term "contact" can mean direct contact or indirect contact through an intermediate medium.

[0052] In the embodiments of the present application, "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0053] The optical detection circuit provided in the embodiments of this application can be applied to base station systems, satellite communication systems, radar systems, optical sensing systems, and the like. For example, when the optical detection circuit is applied to a base station system, it can be part of the circuit structure of the base station's optoelectronic conversion module, used to implement optoelectronic conversion of signals within the base station. The embodiments of this application do not limit the specific application scenarios of the optical detection circuit.

[0054] The following uses the photoelectric conversion module in a base station system as an example application scenario. As a core component of wireless communication systems, the performance of the photoelectric conversion module directly affects the signal transmission distance and quality. Therefore, it is necessary to consider indicators such as linearity and current efficiency to meet the application requirements of the base station system.

[0055] FIG1 is an architecture diagram of a wireless communication system provided in an embodiment of the present application.

[0056] An embodiment of the present application provides a wireless communication system, as shown in Figure 1, the wireless communication system includes a baseband unit (BBU), an optical fiber and a wireless communication base station. The BBU is connected to the wireless communication base station via an optical fiber, and the optical fiber is used to achieve the remote transmission of radio frequency optical signals.

[0057] The BBU is primarily responsible for processing the Radio Link Control (RLC) protocol, the Medium Access Control (MAC) protocol, some Port Physical Layer (PHY) functions, the Radio Resource Control (RRC) protocol, and the Packet Data Convergence Protocol (PDCP). For example, the BBU is also responsible for receiving radio frequency signals, performing electrical-to-optical conversion on the received radio frequency signals, and transmitting them via optical fiber.

[0058] The wireless communication base station is connected to the BBU. The wireless communication base station is mainly used to perform photoelectric conversion, transmission, and radiation of the received optical radio frequency signals to establish a downlink from the base station to the terminal equipment, and to receive, transmit, and perform electro-optical conversion of the uplink signals from the terminal equipment to establish an uplink from the terminal equipment to the base station.

[0059] A wireless communication base station can be a base transceiver station (BTS) in a global system for mobile communication (GSM) system or a code division multiple access (CDMA) network, a 3G base station NodeB in a wideband code division multiple access (WCDMA) system, or an evolutionary NodeB (eNB or eNodeB) in a long term evolution (LTE) system.

[0060] FIG2 is an architecture diagram of a wireless communication base station provided in an embodiment of the present application.

[0061] The present invention provides a wireless communication base station. For example, the wireless communication base station can be a radio frequency photon base station architecture based on optical radio frequency remote (RFR) technology. As shown in Figure 2, the wireless communication base station includes an optical detection circuit 10, an electro-optical conversion circuit 20, a low noise amplifier (LNA), and an antenna unit 30. The wireless communication base station provided in the present invention simplifies the remote radio unit (RRU) on the basis of the traditional RRU architecture, moving the digital signal processing unit, digital-to-analog conversion unit, etc. to the base unit (BBU) side under the tower.

[0062] The optical detection circuit 10 is primarily used to achieve high-efficiency optoelectronic conversion of optical signals in the transmit link into electrical signals. The electro-optical (EO) conversion circuit 20 is primarily used to achieve conversion of electrical signals into optical signals in the receive link. The electro-optical conversion circuit 20 may include, for example, a directly modulated laser or an externally modulated laser. The LNA is primarily used to achieve low-noise amplification of small signals received in the receive link. The antenna unit 30 is primarily used to achieve functions such as isolation, bidirectional transmission, filtering, and radiation of uplink and downlink signals. Antenna unit 30 is, for example, a filtering antenna unit.

[0063] Of course, the wireless communication base station may also include a switch unit or a duplexer to isolate the transmit link from the receive link to ensure that both transmit and receive can function normally at the same time. The switch unit or duplexer may be independently provided or integrated into the antenna unit 30.

[0064] In some embodiments, the optical detection circuit 10, the electro-optical conversion circuit 20, and the LNA can be integrated into a single module, as a photoelectric conversion module provided in embodiments of the present application for use in a wireless communication base station. For example, the optical detection circuit 10, the electro-optical conversion circuit 20, and the LNA can exist in the form of devices.

[0065] In other embodiments, the optical detection circuit 10, the electro-optical conversion circuit 20, and the LNA may be integrated into one chip, and applied to a wireless communication base station as an electro-optical conversion chip provided in an embodiment of the present application.

[0066] The photoelectric conversion chip can be a bare chip, for example, the light detection circuit 10, the electro-optical conversion circuit 20 and the LNA are integrated on the same wafer. The photoelectric conversion chip can also be a chip packaged from a bare chip.

[0067] The optoelectronic conversion chip can also be a chip formed by sealing multiple chips (bare chips or packaged chips). In this case, the optoelectronic conversion chip can also be understood as an optoelectronic conversion chip system, which includes multiple chips in the form of bare chips and / or packaged chips. For example, the light detection circuit 10 and the electro-optical conversion circuit 20 are two independent chips that are then sealed together with the LNA to form the optoelectronic conversion chip of this application. Of course, the LNA can exist in the form of a device or a chip.

[0068] In some embodiments, a conventional PIN photodetector is used as the light detection circuit 10. Traditional PIN photodetectors based on germanium have a response speed exceeding 2 GHz, becoming the prototype of modern high-speed photodetectors. With the maturity of the indium phosphide (InP) material system, the bandwidth of conventional PIN photodetectors has been rapidly improved through continuous optimization of the material epitaxial structure and device architecture.

[0069] As the demand for photodetector response speed increases, device size becomes smaller and smaller, while the current density within the device increases. As a result, the devices are increasingly affected by space charge and thermal effects. The collapse of the electric field within the depletion region not only reduces bandwidth but also saturates the device's microwave output power. The saturation power of a photodetector affects the gain, noise figure, and dynamic range of microwave photonic links. Therefore, while maintaining bandwidth, the saturation power of traditional PIN photodetectors can no longer meet the high-speed and high-power requirements.

[0070] FIG3 is a graph showing the relationship between the power conversion efficiency and the output power of a high-power photodetector provided in an embodiment of the present application.

[0071] In some embodiments, a charge-compensated modified uni-travelling-carrier high-power photodiode (CC-MUTC-HPD) is used as the light detection circuit 10. Currently, in the 10 GHz frequency band, the CC-MUTC-HPD has a peak efficiency of 50.7% to 60% when its RF output power is 27.8 dBm.

[0072] For the scenario where a high-power photodiode (HPD) directly drives the antenna unit 30, the RF output power of the HPD is generally in the range of 20dBm-25dBm, and the peak-to-average ratio of the modulated signal is usually around 8dB-10dB. After the backoff, the efficiency of the HPD will be greatly reduced. For example, as shown in Figure 3, the power conversion efficiency (PCE) changes with the output power of the HPD when the output power is in the range of 17dBm-27dBm and the bias voltage remains unchanged. It can be seen that when the saturated output power is close to 27dBm, the PCE of the HPD can reach 29.6%. However, when the signal backs off by 8dB, the PCE is only 4.7%.

[0073] In practice, due to the high peak-to-average ratio of the modulated signal, the HPD's average output power needs to be backed off by 6dB-10dB from the peak value to maintain peak linearity. This 6dB-10dB peak-to-average ratio backoff makes it difficult for the HPD's RF output power to reach 20dBm, significantly reducing the corresponding backoff efficiency. However, to reduce tower-mounted RRU power consumption, it is necessary to meet the peak linearity requirement while also improving the HPD's backoff efficiency.

[0074] FIG4 is a schematic diagram of the topological structure of a balanced photodetector provided in an embodiment of the present application.

[0075] In some embodiments, a balanced photo detector (BPD) is used as the light detection circuit 10 .

[0076] BPD is widely used in space optical communications due to its high sensitivity and low noise. BPD uses dual photodiodes to input optical signals and suppress or eliminate common-mode noise in the signal. It is one of the core components of coherent optical communications. According to the different chip connection structures, it can be divided into current self-subtraction structure and differential amplifier structure. Figure 4 shows a BPD with a differential amplifier structure. The BPD includes a differential amplifier, two photodiodes (PD), two capacitors C and two resistors R. The differential amplifier is, for example, a trans-impedance amplifier (TIA) with dual input terminals. The resistor R, capacitor C, and PD form a current arm. The current difference between the two arms is obtained through the TIA and a differential voltage output is achieved.

[0077] Differentially amplified BPDs can also be categorized as fiber-coupled and spatially coupled, depending on the optical coupling method. Waveguide-based BPDs can resolve the conflicting constraints between light absorption efficiency and carrier transit time and are easily integrated with other photonic components. While BPDs offer these advantages and can amplify differential signals and improve sensitivity, a BPD that combines the high RF power of a vertically illuminated structure with the high bandwidth of a waveguide structure has yet to be developed. Vertically illuminated BPDs can achieve high RF power, but the bandwidth is limited. Waveguide-integrated BPDs can achieve significant bandwidth, but the RF power does not reach the level of a vertically illuminated structure.

[0078] Based on this, although there are currently various structures of the light detection circuit 10, they all have shortcomings, and optimizing the structure of the light detection circuit 10 remains a difficult problem for those skilled in the art. The present embodiment of the present application aims to propose an unbalanced light detection circuit 10 to optimize the fallback efficiency of the light detection circuit 10.

[0079] FIG5 is a schematic diagram of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0080] An embodiment of the present application provides a light detection circuit 10. As shown in Figure 5, light detection circuit 10 includes an optical input terminal I, a first branch, a second branch, an impedance modulation network 13, and a radio frequency output terminal Ro. The first branch and the second branch are connected in parallel and combined at the input terminal of the impedance modulation network 13. The output terminal of the impedance modulation network 13 is coupled to the radio frequency output terminal Ro. The radio frequency signals output by the first branch and the second branch are combined to form a final output radio frequency signal, which is output from the radio frequency output terminal Ro. The radio frequency output terminal Ro is configured to couple to a load, which may include, for example, a resistor, a capacitor, an inductor, or an antenna unit 30.

[0081] The optical input terminal I is used to input an optical signal, which includes a first optical signal and a second optical signal. For example, as shown in FIG5 , the optical input terminal I includes a first optical input terminal I1 and a second optical input terminal I2 . The first optical input terminal I1 is used to input the first optical signal, and the second optical input terminal I2 is used to input the second optical signal.

[0082] The first branch includes a first optical detector 11, which is used to receive a first optical signal and output a first radio frequency signal. For example, the first optical detector 11 includes a first input end and a first output end, the first input end is used to receive the first optical signal, and the first output end is used to output the first radio frequency signal.

[0083] The second branch includes a second photodetector 12 and a first power amplifier PA1. The second photodetector 12 is used to receive a second optical signal and output a second radio frequency signal. For example, the second photodetector 12 includes a second input terminal and a second output terminal. The second input terminal is used to receive the second optical signal, and the second output terminal is used to output the second radio frequency signal. The first power amplifier PA1 is coupled between the second photodetector 12 and the impedance modulation network 13, and is used to amplify the second radio frequency signal and control the connection between the second photodetector 12 and the impedance modulation network 13. For example, the first power amplifier PA1 includes a third input terminal and a third output terminal. The third input terminal is coupled to the second output terminal of the second photodetector 12, and the third output terminal is connected to the fourth input terminal of the impedance modulation network 13. In addition to amplifying the second radio frequency signal, the first power amplifier PA1 also controls the connection between the second output terminal and the third input terminal.

[0084] In this embodiment of the present application, the first power amplifier PA1 operates as a Class C amplifier. The gate voltage of the first power amplifier PA1 can be adjusted so that it is turned on when the second RF signal is greater than a certain threshold and turned off when the second RF signal is less than the threshold. The second photodetector 12 is used to drive the first power amplifier PA1 to achieve the threshold turn-on effect of the phototransistor.

[0085] The first optical signal and the second optical signal are two optical signals obtained by processing the input radio frequency signal. For example, the input radio frequency signal undergoes branching, electro-optical conversion, and amplification to obtain the first and second optical signals. The first and second optical signals can have equal or unequal powers. They can also have the same or different phases.

[0086] The impedance modulation network 13 is configured to transform the output impedance of the first photodetector 11 and the second photodetector 12, and couple the outputs of the first photodetector 11 and the second photodetector 12 to the RF output Ro. For example, the impedance modulation network 13 includes a fourth input and a fourth output. The first output of the first photodetector 11 and the third output of the first power amplifier PA1 are coupled to the fourth input, and the fourth output is coupled to the RF output Ro. The impedance modulation network 13 is configured to adjust the impedance load presented at the outputs of the first photodetector 11 and the second photodetector 12 based on the power of the first and second optical signals.

[0087] The impedance modulation network 13 is, for example, a microstrip line structure. For example, the impedance modulation network 13 may be a 1 / 4 wavelength impedance converter or the like.

[0088] For example, the first power amplifier PA1 is configured to disconnect the second optical detector 12 from the impedance modulation network 13 when the second RF signal (e.g., the amplitude of the second RF signal) is less than a set value. For example, when the frequency of the second optical signal is low, the power of the second RF signal output by the second optical detector 12 is also low, and the second RF signal is insufficient to turn on the first power amplifier PA1. Turning off the first power amplifier PA1 causes a disconnection between the second optical detector 12 and the impedance modulation network 13. The first branch includes the first optical detector 11, and the first branch is a normally-on circuit. In this case, the impedance of the impedance modulation network 13 serves entirely as the output impedance of the first optical detector 11, and the impedance modulation network 13 acts as the equivalent load for the first branch. For example, if the impedance of the impedance modulation network 13 is 100 ohms, the equivalent load of the first branch is increased to 100 ohms. In this scenario, the voltage of the first branch reaches saturation, the second branch disconnects, and the optical detection circuit 10 operates at its optimal efficiency point.

[0089] The first power amplifier PA1 is used to control the connection between the second light detector 12 and the impedance modulation network 13 when the second RF signal (e.g., the amplitude of the second RF signal) is greater than or equal to a set value. For example, when the frequency of the second light signal is relatively high, the power of the second RF signal output by the second light detector 12 is also relatively high. The second RF signal turns on the first power amplifier PA1, and the turning on of the first power amplifier PA1 causes a connection state to be established between the second light detector 12 and the impedance modulation network 13. In this scenario, the first branch and the second branch are connected in parallel with the impedance modulation network 13, and the impedance modulation network 13 serves as a shared equivalent load for the first branch and the second branch. At this time, the equivalent load of the first branch decreases. For example, as the equivalent load of the first branch gradually decreases from 100 ohms, the current in the first branch gradually increases. Meanwhile, the load of the second branch decreases from an open circuit state, and the current in the second branch also gradually increases. When the intensity of the second optical signal reaches the saturation output point (or peak operating point) of the second branch, the first and second branches evenly divide the impedance of the impedance modulation network 13, so that the loads of the first and second branches are both 50 ohms. At this point, the currents in the first and second branches both reach their maximum values ​​and become equal. When the phases of the first and second branches are equal, the output power of the optical detection circuit 10 reaches its maximum.

[0090] FIG6 is a graph showing a change in efficiency with input power according to an embodiment of the present application.

[0091] The dashed line in Figure 6 shows the efficiency of a light detection circuit (conventional light detection circuit) that includes only the first light detector 11 as a function of input power. The solid line in Figure 6 shows the efficiency of the light detection circuit 10 provided in the present application as a function of input power. The horizontal axis in Figure 6 represents input power, and the vertical axis represents efficiency. As can be seen from Figure 6, the conventional light detection circuit achieves a power conversion efficiency of approximately 59% at an input power of 25dBm. However, when the input power falls back to 17dBm, the fallback efficiency only reaches approximately 25%. In contrast, the light detection circuit 10 provided in the present embodiment achieves a power conversion efficiency of approximately 54.5% at an input power of 25dBm, and a fallback efficiency of approximately 41% when the input power falls back to 17dBm.

[0092] In the optical detection circuit 10 provided in the embodiment of the present application, a first optical detector 11 and a second optical detector 12 are connected in parallel, and the connectivity of the branch containing the second optical detector 12 depends on whether the second RF signal is greater than the threshold turn-on voltage of the first power amplifier PA1. This circuit structure, in which the branch containing the first optical detector 11 is continuously conductive, while the branch containing the second optical detector 12 is only conductive when the second RF signal reaches a set peak, achieves a transistor-like turn-on voltage effect, thereby increasing the output power of the optical detection circuit 10. Furthermore, the use of an impedance modulation network 13 to combine the branch containing the first optical detector 11 and the branch containing the second optical detector 12 enables load modulation when the input power varies, thereby achieving dynamic load transformation from the back-off point to the maximum output point. This facilitates maintaining high output efficiency for both the first and second optical detectors 11, 12 within the range between the maximum power point and the back-off point, thereby improving the back-off efficiency of the optical detection circuit 10.

[0093] Regarding the method for making the phases of the first branch and the second branch equal, in some embodiments, the phases of the first optical signal and the second optical signal are adjusted before being input to the optical detection circuit 10. Then, the first optical signal and the second optical signal received by the optical detection circuit 10 are optical signals with the same phase.

[0094] In other embodiments, the first optical signal and the second optical signal are optical signals with different phases, and a phase adjustment structure is provided in the optical detection circuit 10 so that the phases of the first RF signal and the second RF signal are the same.

[0095] 7A and 7B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0096] In some embodiments, as shown in FIG7A , the optical detection circuit 10 further includes a first capacitor C1 and a second capacitor C2. The first capacitor C1 is coupled between the first optical detector 11 and the impedance modulation network 13, and the second capacitor C2 is coupled between the second optical detector 12 and the first power amplifier PA1. The first capacitor C1 and the second capacitor C2 are used to pass the AC signal and filter out the DC signal.

[0097] In some embodiments, as shown in FIG. 7A , the optical detection circuit 10 further includes a first optical delay device 14 . The first optical signal is phase-shifted by the first optical delay device 14 and then transmitted to the first optical detector 11 .

[0098] By adjusting the phase of the first optical signal with the help of the first optical delay device 14, the first optical signal and the second optical signal can be made into in-phase optical signals, and the corresponding output first radio frequency signal and the second radio frequency signal are also made into in-phase radio frequency signals, so as to reduce the problems of reduced efficiency and deterioration of signal quality caused by the phase inconsistency when the two signals are synthesized.

[0099] In some other embodiments, as shown in FIG. 7B , the optical detection circuit 10 further includes a second optical delay device 15 , and the second optical signal is phase-shifted by the second optical delay device 15 and then transmitted to the second optical detector 12 .

[0100] By adjusting the phase of the second optical signal with the help of the second optical delay device 15, the first optical signal and the second optical signal can be made into in-phase optical signals, and the corresponding output first radio frequency signal and the second radio frequency signal are also made into in-phase radio frequency signals, so as to reduce the problems of reduced efficiency and deterioration of signal quality caused by the phase inconsistency when the two signals are synthesized.

[0101] In some other embodiments, the optical detection circuit 10 includes a first optical delay device 14 and a second optical delay device 15. The first optical delay device 14 adjusts the phase of the first optical signal, and the synchronized second optical delay device 15 adjusts the phase of the second optical signal. This can ensure that the first optical signal and the second optical signal are in-phase optical signals, and the corresponding output first radio frequency signal and the second radio frequency signal are also in-phase radio frequency signals, thereby reducing problems such as reduced efficiency and deteriorated signal quality caused by phase inconsistency when the two signals are synthesized.

[0102] The optical detection circuit 10 provided in the embodiment of the present application, by providing an optical delay device before the first optical detector 11 and / or the second optical detector 12, adjusts the phase of the first optical signal and / or the second optical signal through optical adjustment, so that the optical detection circuit 10 supports phase adjustment of broadband signals, and the phase adjustment of the optical delay device structure has high phase adjustment accuracy, large bandwidth, and fast switching.

[0103] The first optical delay device 14 and the second optical delay device 15 can be adjustable optical delay devices, or they can be non-adjustable optical delay devices. The embodiment of the present application does not limit the structure of the first optical delay device 14 and the second optical delay device 15, and the optical delay devices in the related art are all applicable to the embodiment of the present application.

[0104] 8A and 8B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0105] In some embodiments, as shown in FIG. 8A , the light detection circuit 10 further includes a first phase shifter 16 , which is coupled between the first light detector 11 and the impedance modulation network 13 .

[0106] By adjusting the phase of the first RF signal with the help of the first phase shifter 16, the first RF signal and the second RF signal can be made into RF signals with the same phase, thereby reducing the problems of reduced efficiency and deterioration of signal quality caused by phase inconsistency when the two signals are synthesized.

[0107] In some other embodiments, as shown in FIG8B , the light detection circuit 10 further includes a second phase shifter 17 , which is coupled between the second light detector 12 and the first power amplifier PA1 .

[0108] By adjusting the phase of the second RF signal with the help of the second phase shifter 17, the first RF signal and the second RF signal can be made into RF signals with the same phase, thereby reducing the problems of reduced efficiency and poor signal quality caused by phase inconsistency when the two signals are synthesized.

[0109] In some other embodiments, the optical detection circuit 10 includes a first phase shifter 16 and a second phase shifter 17. The first phase shifter 16 adjusts the phase of the first RF signal, and the synchronized second phase shifter 17 adjusts the phase of the second RF signal, so that the first RF signal and the second RF signal can be RF signals with the same phase, thereby reducing problems such as reduced efficiency and deterioration of signal quality caused by phase inconsistency when the two signals are synthesized.

[0110] The optical detection circuit 10 provided in the embodiment of the present application provides a phase shifter after the first optical detector 11 and / or the second optical detector 12, and adjusts the phase of the first RF signal and / or the second RF signal by electrical adjustment, so that the optical detection circuit 10 supports phase adjustment of broadband signals, and the integration difficulty and cost of the electrical phase shifter are low.

[0111] The first phase shifter 16 and the second phase shifter 17 can be adjustable phase shifters, or they can be non-adjustable phase shifters. The embodiment of the present application does not limit the structure of the first phase shifter 16 and the second phase shifter 17, and all phase shifters in related arts are applicable to the embodiment of the present application.

[0112] In the first scenario, the power of the first optical signal is equal to the power of the second optical signal.

[0113] Then, the amplitude of the first RF signal is equal to the amplitude of the second RF signal. However, the amplitude of the amplified RF signal output after the second RF signal is amplified by the first power amplifier PA1 is different from the amplitude of the first RF signal.

[0114] In the second scenario, the power of the first optical signal is less than the power of the second optical signal.

[0115] Then, the amplitude of the first RF signal is smaller than the amplitude of the second RF signal, and the amplitude of the amplified RF signal output after the second RF signal is amplified by the first power amplifier PA1 is greater than the amplitude of the first RF signal.

[0116] In some embodiments, the optical detection circuit 10 further includes a power adjustment structure for making the amplitude of the first radio frequency signal equal to the amplitude of the amplified radio frequency signal output by the first power amplifier PA1.

[0117] 9A and 9B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0118] In some embodiments, as shown in FIG. 9A , the optical detection circuit 10 further includes an optical attenuator 18 , and the second optical signal is attenuated by the optical attenuator 18 and then transmitted to the second optical detector 12 .

[0119] By adjusting the power of the second optical signal using optical attenuator 18, the power of the first optical signal can be increased relative to the power of the second optical signal, resulting in a corresponding increase in the amplitude of the first RF signal. After amplification of the second RF signal by first power amplifier PA1, the amplitude of the RF signal output from the first branch is equal to the amplitude of the RF signal output from the second branch. This reduces the inefficiency and signal quality degradation caused by amplitude mismatches when the two signals are combined. Furthermore, optical attenuator 18 provides high precision in adjusting the power of the optical signal.

[0120] The optical attenuator 18 may be an adjustable optical attenuator or a non-adjustable optical attenuator. The embodiment of the present application does not limit the structure of the optical attenuator 18. All optical attenuators in related technologies are applicable to the embodiment of the present application.

[0121] In some other embodiments, as shown in FIG. 9B , the light detection circuit 10 further includes an electrical attenuator 19 , which is coupled between the second light detector 12 and the first power amplifier PA1 .

[0122] By adjusting the power of the second RF signal with the aid of electrical attenuator 19, the amplitude of the first RF signal can be made greater than that of the second RF signal. After the second RF signal is amplified by first power amplifier PA1, the amplitude of the RF signal output by the first branch can be made equal to the amplitude of the RF signal output by the second branch, thereby reducing problems such as reduced efficiency and poor signal quality caused by inconsistent amplitudes when the two signals are synthesized. Furthermore, electrical attenuator 19 is easy to integrate and has low cost.

[0123] In some other embodiments, the optical detection circuit 10 includes an optical attenuator 18 and an electrical attenuator 19. The optical attenuator 18 adjusts the power of the second optical signal before the second optical detector 12, and the electrical attenuator 19 adjusts the power of the second RF signal after the second optical detector 12. Ultimately, the first RF signal and the amplified RF signal can be made into RF signals of equal amplitude to reduce loss.

[0124] In some further embodiments, the optical detection circuit 10 includes an optical enhancer and / or an electrical enhancer, wherein the optical enhancer is arranged before the first optical detector 11, and the electrical enhancer is arranged after the first optical detector 11, and is used to make the amplitude of the radio frequency signal output by the first branch equal to the amplitude of the radio frequency signal output by the second branch.

[0125] In the third scenario, the power of the first optical signal is greater than the power of the second optical signal.

[0126] Then, the amplitude of the first RF signal is greater than the amplitude of the second RF signal, and the amplitude of the amplified RF signal output by the first power amplifier PA1 after the second RF signal is amplified can be exactly equal to the amplitude of the first RF signal. In this scenario, the light detection circuit 10 does not need to include a power adjustment structure, which can simplify the structure of the light detection circuit 10.

[0127] 10A and 10B are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0128] In some embodiments, as shown in FIG. 10A , the optical detection circuit 10 further includes a third branch, which includes a third optical detector 12 ′ and a second power amplifier PA2 .

[0129] The optical input terminal I further includes a third optical input terminal I3, and the third optical input terminal I3 is used to input a third optical signal.

[0130] The third photodetector 12 ′ is configured to receive a third optical signal and output a third radio frequency signal. The second power amplifier PA2 is coupled between the third photodetector 12 ′ and the impedance modulation network 13 and is configured to control the connection between the third photodetector 12 ′ and the impedance modulation network 13 .

[0131] In addition to the first and second branches, optical detection circuit 10 may also include one or more third branches, with the third branch and the second branch both being conditionally enabled. The RF signals output by the first, second, and third branches are phase-matched and combined for output via impedance modulation network 13.

[0132] In some embodiments, the third branch may also include structures such as an optical delay device, a phase shifter, an optical attenuator, and an electrical attenuator. The arrangement of the aforementioned structures in the third branch can refer to the above description of the structure in the second branch and will not be repeated here.

[0133] For example, as shown in Figure 10B, the first branch in the optical detection circuit 10 includes a first optical detector 11 and a first phase shifter 16, the second branch includes a second optical detector 12, a second phase shifter 17 and a first power amplifier PA1, and the third branch includes a third optical detector 12', a third phase shifter 17' and a second power amplifier PA2. The output end of the first phase shifter 16, the output end of the first power amplifier PA1, and the output end of the second power amplifier PA2 are combined at the input end of the impedance modulation network 13.

[0134] By providing multiple conditionally enabled circuits within the optical detection circuit 10, the optical detection circuit 10 can have multiple efficiency optima within the backoff interval, thereby improving the average efficiency of the entire backoff interval. For example, the optical detection circuit 10 has an efficiency optimum when the first branch operates independently, an efficiency optimum when the first and second branches operate synchronously, an efficiency optimum when the first and third branches operate synchronously, and an efficiency optimum when the first, second, and third branches operate synchronously.

[0135] In some embodiments, the turn-on voltage of the first power amplifier PA1 is not equal to the turn-on voltage of the second power amplifier PA2 .

[0136] In this way, the branch where the second light detector 12 is located and the branch where the third light detector 12 ′ is located provide different efficiency optimum points, thereby improving the average efficiency in the back-off interval.

[0137] FIG11 is a schematic diagram of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0138] In some embodiments, as shown in FIG. 11 , the optical detection circuit 10 further includes an impedance matching network 40 . The impedance matching network 40 is coupled between the second optical detector 12 and the first power amplifier PA1 .

[0139] The impedance matching network 40 can be, for example, a 1 / 4 microstrip line or a resistor-capacitor (RC) matching network. The impedance matching network 40 is used to match the output impedance of the second photodetector 12 with the input impedance of the first power amplifier PA1 to reduce the excessive insertion loss caused by impedance mismatch when the second photodetector 12 is cascaded with the first power amplifier PA1.

[0140] The optical detection circuit 10 shown in Figures 5-11 is configured to receive a first optical signal and a second optical signal. The optical detection circuit 10 includes two optical input ports, each of which is an optical port. These optical input ports can be, for example, pigtailed or pluggable fiber ports. The optical detection circuit 10 includes two unbalanced links, which are ultimately combined to the RF output port Ro via an impedance modulation network 13. The RF output port Ro is used to output RF signals and can be connected to other circuits via coaxial connectors, pin soldering, or surface mount soldering.

[0141] 12A-12C are schematic diagrams of a topological structure of a light detection circuit provided in an embodiment of the present application.

[0142] In some embodiments, as shown in FIG12A , the optical detection circuit 10 further includes an optical splitter 50 , which is configured to split the received optical signal (optical radio frequency signal) into a first optical signal and a second optical signal.

[0143] In this case, as shown in Figure 12A , the optical detection circuit 10 includes an optical input port I, which is an optical port. An optical splitter 50 splits the optical signal power, outputting a first optical signal and a second optical signal. Compared to requiring two independent optical input ports, this simplifies the number of input interfaces in the optical detection circuit 10, achieving increased power and efficiency without increasing the cost or complexity of the optical detection circuit 10.

[0144] In some embodiments, as shown in FIG12B , the optical splitter 50 is a uniform power splitter.

[0145] The input RF signal is converted into an optical signal by a photodiode, and the optical signal is transmitted to the optical splitter 50 in the optical detection circuit 10 through an optical fiber. The optical splitter 50 splits the received signal into a first optical signal and a second optical signal in a 1:1 ratio.

[0146] In this way, any optical splitter 50 capable of achieving proportional power division in the related art is applicable to the embodiments of the present application. The technology of the optical splitter 50 is mature and easy to implement. In this case, for example, the optical detection circuit 10 also includes the above-mentioned power adjustment structure (such as the electrical attenuator 19 in Figure 12B) to ensure that the first branch and the second branch output RF signals of equal amplitude and phase.

[0147] In other embodiments, as shown in FIG. 12C , the optical splitter 50 is a non-uniform power splitter.

[0148] The optical splitter 50 splits the received optical signal into a first optical signal and a second optical signal in non-uniform proportions. For example, the proportion of the first optical signal is greater than the proportion of the second optical signal.

[0149] In this way, the optical detection circuit 10 does not need to include the above-mentioned power adjustment structure. As long as it includes a phase adjustment structure (such as the first phase shifter 16 and the second phase shifter 17 in Figure 12C), the first branch and the second branch can output radio frequency signals of equal amplitude and phase, which can simplify the structure of the optical detection circuit 10.

[0150] Regardless of whether the optical splitter 50 is a uniform power splitter or a non-uniform power splitter, after the distribution ratio of the optical splitter 50 is determined, the gate voltage of the first power amplifier PA1 can be adjusted so that when the power of the optical radio frequency signal received by the optical splitter 50 is greater than or equal to the average power, the first power amplifier PA1 is turned on. When the power of the optical radio frequency signal received by the optical splitter 50 is less than the average power, the first power amplifier PA1 is turned off.

[0151] It should be noted that when the power adjustment structure in the optical detection circuit 10 is an optical attenuator 18, and the phase adjustment structure in the optical detection circuit 10 is a first optical delay device 14 or a second optical delay device 15, one or more of the optical attenuator 18, the first optical delay device 14, and the second optical delay device 15 can be integrated in the optical splitter 50.

[0152] Regarding the structures of the first light detector 11 and the second light detector 12 , in some embodiments, the first light detector 11 and the second light detector 12 are high power photodetectors (HPDs).

[0153] FIG13 is a schematic structural diagram of a first light detector provided in an embodiment of the present application.

[0154] For example, as shown in FIG13 , the first photodetector 11 includes an anti-reflection coating (ARC), a substrate, an N contact layer, a drift layer, a cliff layer, a depleted absorption layer, an undoped absorption layer, an N metal layer, a coplanar waveguide signal region, a coplanar waveguide ground (GND), and a diamond submount. Of course, the structure of the first photodetector 11 shown in FIG13 is merely illustrative and does not constitute a limitation.

[0155] A first optical signal is incident on the side of the anti-reflection coating and enters the first photodetector 11. Photoelectric conversion is achieved within the first photodetector 11 using the internal photoelectric effect of the semiconductor material. Absorbing photons generates electron-hole pairs, which in turn generates a photocurrent in the external circuit. When the incident light is an RF optical carrier signal, the output photocurrent contains both DC and RF components. The RF component is output through the coplanar waveguide signal region to form a first RF signal. The coplanar waveguide signal region is coupled to the impedance modulation network 13, and the coplanar waveguide ground is coupled to the reference ground voltage terminal.

[0156] In some embodiments, the structure of the second light detector 12 is the same as that of the first light detector 11 , and will not be further described here.

[0157] The embodiment of the present application further provides a signal processing method, which can be performed by the above-mentioned light detection circuit 10. The signal processing method includes the following steps:

[0158] The first photodetector 11 receives a first optical signal and performs photoelectric conversion on the first optical signal to generate a first radio frequency signal. The second photodetector 12 receives a second optical signal and performs photoelectric conversion on the second optical signal to generate a second radio frequency signal.

[0159] The first optical signal and the second optical signal are two optical signals obtained after processing the input RF signal. Referring to the above description, the first optical signal and the second optical signal can be optical signals that have been split and processed before entering the optical detection circuit 10, or they can be signals generated by processing after entering the optical detection circuit 10. In this case, the signal processing method also includes receiving the optical signal and processing the optical signal (e.g., power splitting) to generate the first optical signal and the second optical signal. This step can be performed, for example, by the aforementioned optical splitter 50.

[0160] The first power amplifier PA1 is turned on or off under the control of the second radio frequency signal, and amplifies the second radio frequency signal when the first power amplifier PA1 is turned on.

[0161] For example, the first power amplifier PA1 is turned off when the second RF signal is less than a set value, and the amplified second RF signal output by the first power amplifier PA1 can be understood as 0. The first power amplifier PA1 is turned on when the second RF signal is greater than or equal to the set value.

[0162] The impedance modulation network 13 performs output impedance transformation on the first photodetector 11 and the second photodetector 12 , and combines the first radio frequency signal and the amplified second radio frequency signal for output.

[0163] The impedance modulation network 13 transforms the output impedance of the first photodetector 11 and the second photodetector 12 according to the power of the first RF signal and the power of the second RF signal. The specific process can be referred to the above description of the impedance modulation network 13 and will not be repeated here.

[0164] In some embodiments, the signal processing method further includes: performing phase modulation on the first optical signal. For example, the first optical delay device 14 is used to perform phase modulation on the first optical signal.

[0165] In some embodiments, the signal processing method further includes: performing phase modulation on the second optical signal. For example, the second optical delay device 15 described above is used to perform phase modulation on the second optical signal.

[0166] In some embodiments, the signal processing method further includes: performing amplitude modulation on the second optical signal. For example, the above-mentioned optical attenuator 18 is used to perform amplitude modulation on the second optical signal.

[0167] In some embodiments, the signal processing method further includes: performing phase modulation on the first radio frequency signal. For example, the first phase shifter 16 is used to perform phase modulation on the first radio frequency signal.

[0168] In some embodiments, the signal processing method further includes: performing phase modulation on the second radio frequency signal. For example, the second phase shifter 17 is used to perform phase modulation on the second radio frequency signal.

[0169] In some embodiments, the signal processing method further includes: performing amplitude modulation on the second radio frequency signal. For example, the above-mentioned electric attenuator 19 is used to perform amplitude modulation on the second radio frequency signal.

[0170] In this application, under the premise that there is no logical contradiction, the various embodiments may reference each other, for example, the methods and / or terms between method embodiments may reference each other, for example, the functions and / or terms between device embodiments may reference each other, for example, the functions and / or terms between device embodiments and method embodiments may reference each other.

[0171] The above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A light detection circuit, characterized in that: include: An optical input end, used for inputting an optical signal, wherein the optical signal includes a first optical signal and a second optical signal; RF output terminal; a first optical detector, configured to receive the first optical signal and output a first radio frequency signal; a second optical detector, configured to receive the second optical signal and output a second radio frequency signal; an impedance modulation network, configured to transform the output impedance of the first photodetector and the second photodetector, and couple the output end of the first photodetector and the output end of the second photodetector to the radio frequency output end; The first power amplifier is coupled between the second photodetector and the impedance modulation network, and is used for amplifying the second radio frequency signal and controlling the connection between the second photodetector and the impedance modulation network.

2. The light detection circuit according to claim 1, characterized in that: The first power amplifier is specifically used to control the second light detector and the impedance modulation network to be disconnected when the second RF signal is less than a set value; and to control the second light detector and the impedance modulation network to be connected when the second RF signal is greater than or equal to the set value.

3. The light detection circuit according to claim 1 or 2, characterized in that: It also includes an optical attenuator, and the second optical signal is attenuated by the optical attenuator and then transmitted to the second optical detector.

4. The light detection circuit according to any one of claims 1 to 3, characterized in that: The invention also includes an electric attenuator coupled between the second photodetector and the first power amplifier.

5. The light detection circuit according to any one of claims 1 to 4, characterized in that: The optical detection circuit further includes a first optical delay device; the first optical signal is phase-shifted by the first optical delay device and then transmitted to the first optical detector; and / or, The optical detection circuit also includes a second optical delay device; the second optical signal is phase-shifted by the second optical delay device and then transmitted to the second optical detector.

6. The light detection circuit according to any one of claims 1 to 4, characterized in that: The optical detection circuit further includes a first phase shifter; the first phase shifter is coupled between the first optical detector and the impedance modulation network; and / or, The optical detection circuit further includes a second phase shifter; the second phase shifter is coupled between the second optical detector and the first power amplifier.

7. The light detection circuit according to any one of claims 1 to 6, characterized in that: Also included is a third photodetector and a second power amplifier; The third optical detector is used to receive a third optical signal and output a third radio frequency signal; The second power amplifier is coupled between the third photodetector and the impedance modulation network, and is used to control the connection between the third photodetector and the impedance modulation network.

8. The light detection circuit according to claim 7, characterized in that: A turn-on voltage of the first power amplifier is not equal to a turn-on voltage of the second power amplifier.

9. The light detection circuit according to any one of claims 1 to 8, characterized in that: The power of the first optical signal is greater than or equal to the power of the second optical signal.

10. The light detection circuit according to any one of claims 1 to 9, characterized in that: It also includes an optical splitter; the optical splitter is used to receive the optical signal and split the optical signal into the first optical signal and the second optical signal.

11. The light detection circuit according to any one of claims 1 to 10, characterized in that: The device also includes an impedance matching network coupled between the second photodetector and the first power amplifier.

12. The light detection circuit according to any one of claims 1 to 11, characterized in that: Also includes a first capacitor and a second capacitor; The first capacitor is coupled between the first photodetector and the impedance modulation network, and the second capacitor is coupled between the second photodetector and the first power amplifier.

13. A photoelectric conversion module, characterized in that: It comprises a light detection circuit and an electro-optical conversion circuit; the light detector is used to convert a received light signal into an electrical signal, and the electro-optical conversion circuit is used to convert a received electrical signal into an optical signal; the light detection circuit comprises the light detection circuit according to any one of claims 1 to 12.

14. A photoelectric conversion chip, characterized in that: It comprises a light detection circuit and an electro-optical conversion circuit; the light detector is used to convert a received light signal into an electrical signal, and the electro-optical conversion circuit is used to convert a received electrical signal into an optical signal; the light detection circuit comprises the light detection circuit according to any one of claims 1 to 12.

15. A communication device, characterized in that: It comprises a photoelectric conversion module and an antenna unit, wherein the photoelectric conversion module is coupled to the antenna unit; the photoelectric conversion module comprises the photoelectric conversion module according to claim 13 or the photoelectric conversion chip according to claim 14.

16. A wireless communication system, characterized in that: It comprises a baseband processing unit, a communication device and an optical fiber, wherein the baseband processing unit and the communication device are connected via the optical fiber; the communication device comprises the communication device according to claim 15.

17. A signal processing method, characterized in that: include: The first photodetector receives a first optical signal and performs photoelectric conversion on the first optical signal to generate a first radio frequency signal, and the second photodetector receives a second optical signal and performs photoelectric conversion on the second optical signal to generate a second radio frequency signal; The first power amplifier is turned on or off under the control of the second radio frequency signal, and amplifies the second radio frequency signal when the first power amplifier is turned on; The impedance modulation network transforms the output impedance of the first photodetector and the second photodetector, and combines the first radio frequency signal and the amplified second radio frequency signal for output.

18. The signal processing method according to claim 17, characterized in that: The first power amplifier is turned off when the second radio frequency signal is less than a set value, and is turned on when the second radio frequency signal is greater than or equal to the set value.

19. The signal processing method according to claim 17 or 18, characterized in that: Also includes: performing phase sum modulation on the first optical signal; and / or, performing phase and / or amplitude modulation on the second optical signal; and / or, performing phase modulation on the first radio frequency signal; and / or, The second radio frequency signal is phase and / or amplitude modulated.

20. The signal processing method according to any one of claims 17 to 19, characterized in that: Also includes: An optical signal is input, and the optical signal is processed to generate the first optical signal and the second optical signal.

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