KR20230102808A - Balanced photodetector and receiver using the same - Google Patents

Abstract

The present invention relates to a balanced photodetector and a receiver using the same. A balanced photodetector according to an embodiment of the present invention includes: a light receiving unit implemented as a pair of four photodiodes that convert optical signals into electrical signals and output them; four transimpedance amplifiers that amplify input signals and remove noise by connecting lines through which the output signals of the photodiodes are transmitted to inputs one by one; an inverting amplifier in which a line through which output signals of two transimpedance amplifiers are combined and transmitted is input to an inverting input to perform inverting amplification; a non-inverting amplifier performing non-inverting amplification by inputting a line through which the output signals of the remaining two transimpedance amplifiers are combined and transmitted is input to a non-inverting input; and a differential amplifier having a first input input to a line through which an output signal of the inverting amplifier is transmitted and a line through which an output signal of the non-inverting amplifier is transmitted is input to a second input, wherein an output of the differential amplifier is to detect information about the optical signal.

Description

BALANCED PHOTODETECTOR AND RECEIVER USING THE SAME

The present invention relates to a balanced photodetector and a receiver using the same, and more particularly, to a balanced photodetector having a performance-enhancing array and structure, and a frequency modulation continuous wave (FMCW) method implemented using the same. It relates to a receiver equipped with a 3D sensor or the like.

A balanced photodetector is a device that detects the difference between two input lights. In the conventional case, a balanced light detector (hereinafter referred to as "the prior art") was implemented using two light receiving elements. That is, the prior art detects the light intensity over time of the light signal received by the two light receiving elements and converts it into a current signal proportional to the light intensity.

In this prior art, as the performances of two light receiving elements match, an excellent Common-Mode Rejection Ratio (CMRR) can be achieved, and noise is reduced accordingly. That is, the overall performance of the balanced photodetector may be determined depending on whether the performances of the two light receiving devices match. However, in the prior art, since two light receiving devices manufactured separately are used, a difference in performance inevitably occurs, and thus the overall performance of the balanced photodetector is deteriorated.

In particular, when the conventional technology having these two light-receiving elements is applied to a 3D sensor-based LiDAR receiver of FMCW (Frequency Modulation Continuous Wave) method, due to the arrangement of the light-receiving elements, the actual transmitted image and the corresponding receiver There may be a large difference between sensed images (ie, received images).

However, the above information merely provides background information on the present invention and does not correspond to previously disclosed technologies.

KR 10-2021-0013076 A

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a balanced photodetector technology having an arrangement and structure for improving optical signal processing performance.

In addition, another object of the present invention is to provide a balanced photodetector applicable to a 3D sensor frequency reception array of FMCW (Frequency Modulation Continuous Wave) method by reducing the difference between transmitted and received images.

However, the problem to be solved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

A balanced photodetector according to an embodiment of the present invention for solving the above problems includes a light receiving unit implemented as a pair of four photodiodes that convert optical signals into electrical signals and output them; four transimpedance amplifiers that amplify input signals and remove noise by connecting lines through which the output signals of the photodiodes are transmitted to inputs one by one; an inverting amplifier in which a line through which output signals of two transimpedance amplifiers are combined and transmitted is input to an inverting input to perform inverting amplification; a non-inverting amplifier performing non-inverting amplification by inputting a line through which the output signals of the remaining two transimpedance amplifiers are combined and transmitted is input to a non-inverting input; and a differential amplifier having a first input input to a line through which an output signal of the inverting amplifier is transmitted and a line through which an output signal of the non-inverting amplifier is transmitted is input to a second input, wherein an output of the differential amplifier is to detect information about the optical signal.

The four photodiodes may be implemented in an integrated manner in one wafer chip.

The four photodiodes may have an array structure of 2 rows and 2 columns (2×2).

Signal phases of output signals of two photodiodes may be inverted through the inverting amplifier, and signal phases of output signals of the remaining two photodiodes may be maintained through the non-inverting amplifier.

In each of the inverting amplifier and the non-inverting amplifier, a feedback resistor may be implemented as a variable resistor.

A ratio between an inverted signal input to the first input and a non-inverted signal input to the second input may be adjusted by adjusting the resistance of each variable resistor.

A receiver according to an embodiment of the present invention is a receiver including a plurality of cells receiving an optical signal of a frequency modulation continuous wave (FMCW), and the plurality of cells are implemented using a plurality of balanced photodetectors. One balanced photodetector includes a light receiving unit implemented as a pair of four photodiodes that convert optical signals into electrical signals and output them; four transimpedance amplifiers that amplify input signals and remove noise by connecting lines through which the output signals of the photodiodes are transmitted to inputs one by one; an inverting amplifier in which a line through which output signals of two transimpedance amplifiers are combined and transmitted is input to an inverting input to perform inverting amplification; a non-inverting amplifier performing non-inverting amplification by inputting a line through which the output signals of the remaining two transimpedance amplifiers are combined and transmitted is input to a non-inverting input; and a differential amplifier having a first input input to a line through which the output signal of the inverting amplifier is transmitted and a line through which the output signal of the non-inverting amplifier is transmitted is input to a second input.

A receiver according to an embodiment of the present invention may be used for LiDAR.

The plurality of cells may implement a 3D sensor or a 4D sensor of the lidar.

The four photodiodes have an array structure of 2 rows and 2 columns (2×2), and may be implemented in an integrated manner within a single wafer chip.

The present invention configured as described above has an advantage of having an arrangement and structure for improving optical signal processing performance.

In addition, the present invention has the advantage of being applicable to a 3D sensor frequency receiving array of FMCW (Frequency Modulation Continuous Wave) method by reducing the difference between transmitted and received images.

In addition, the present invention has an advantage of implementing excellent accuracy and depth resolution for a received signal because four photodiodes are integrated into one wafer chip.

In addition, since the present invention has a 2X2 array structure of four photodiodes, uniform sensing is possible when applied to an optical sensor, and has an advantage of having an array structure applicable to a 3D sensor or a 4D sensor of LiDAR.

That is, the present invention implements a balanced photodetector in which four photodiodes are integrated with a driving circuit as a pair, and when applied to an optical sensor, there is an advantage in that it can exhibit superior performance and function than conventional balanced photodetectors.

In addition, the present invention can amplify the output signal through circuit control of the intensity of the optical signal, which can be weakened by external factors, achieves excellent Common-Mode Rejection Ratio (CMRR), and improves overall performance of the device while reducing noise There are advantages to doing so.

The effects obtainable in the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

1 shows a schematic block diagram of a balanced photodetector 100 according to an embodiment of the present invention.
2 shows a schematic circuit diagram of a balanced photodetector according to an embodiment of the present invention.
3 shows a configuration diagram of a lidar 1 according to an embodiment of the present invention.

The above objects and means of the present invention and the effects thereof will become clearer through the following detailed description in conjunction with the accompanying drawings, and accordingly, those skilled in the art to which the present invention belongs can easily understand the technical idea of the present invention. will be able to carry out. In addition, in describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

Terms used in this specification are for describing the embodiments and are not intended to limit the present invention. In this specification, singular forms also include plural forms in some cases unless otherwise specified in the text. In this specification, terms such as "comprise", "have", "provide" or "have" do not exclude the presence or addition of one or more other elements other than the mentioned elements.

In this specification, terms such as “or” and “at least one” may represent one of the words listed together, or a combination of two or more. For example, "A or B" and "at least one of A and B" may include only one of A or B, or may include both A and B.

In this specification, descriptions following "for example" may not exactly match the information presented, such as cited characteristics, variables, or values, and tolerances, measurement errors, limits of measurement accuracy and other commonly known factors It should not be limited to the embodiments of the present invention according to various embodiments of the present invention with effects such as modifications including.

In this specification, when a component is described as being 'connected' or 'connected' to another component, it may be directly connected or connected to the other component, but there may be other components in the middle. It should be understood that it may be On the other hand, when a component is referred to as 'directly connected' or 'directly connected' to another component, it should be understood that no other component exists in the middle.

In the present specification, when an element is described as being 'on' or 'in contact with' another element, it may be in direct contact with or connected to the other element, but another element may be present in the middle. It should be understood that On the other hand, if an element is described as being 'directly on' or 'directly in contact with' another element, it may be understood that another element in the middle does not exist. Other expressions describing the relationship between components, such as 'between' and 'directly between', can be interpreted similarly.

In this specification, terms such as 'first' and 'second' may be used to describe various elements, but the elements should not be limited by the above terms. In addition, the above terms should not be interpreted as limiting the order of each component, and may be used for the purpose of distinguishing one component from another. For example, a 'first element' may be named a 'second element', and similarly, a 'second element' may also be named a 'first element'.

Unless otherwise defined, all terms used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined.

Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

1 shows a schematic block diagram of a balanced photodetector 100 according to an embodiment of the present invention, and FIG. 2 shows a schematic circuit diagram of the balanced photodetector according to an embodiment of the present invention.

A balanced photodetector 100 according to an embodiment of the present invention is a photodetector having an arrangement and structure for improving performance, and as shown in FIGS. 1 and 2, a light receiving unit 110, a transducer Trans-impedance amplifiers (120, 130, 140, 150), non-inverting amplifiers (160), inverting amplifiers (170) and differential amplifiers (180) , and information on an optical signal received by the optical receiver 110 may be detected using an output of the differential amplifier 180 .

The balanced photodetector 100 may be included in a receiver such as LiDAR, which will be described later. That is, the receiver includes a 3D sensor or 4D sensor that receives and senses an optical signal, and the 3D sensor or 4D sensor includes a plurality of cells, and each cell is implemented using the balanced photodetector 100. can

The light receiving unit 110 receives an optical signal through a light receiving element and converts it into an electrical signal. Accordingly, the light receiving unit 110 includes four photodiodes 111, 112, 113, and 114 implemented as a pair. That is, each of the photodiodes 111, 112, 113, and 114 converts optical signals into electrical signals and outputs them.

These four photodiodes 111, 112, 113, and 114 have an array structure of 2 rows and 2 columns (2×2). Such a 2×2 array structure can act complementary to each other in one cell for an optical signal, enabling uniform sensing when applied to an optical sensor. In addition, the 2×2 array structure implements an array structure applicable to 3D sensors or 4D sensors of lidar, and enables excellent accuracy and depth resolution for optical signals.

On the other hand, in the case of the prior art balanced photodetector, it usually includes two light-receiving elements, and since these two light-receiving elements are separately manufactured, a difference in performance occurs, resulting in a problem in that the overall performance of the balanced photodetector is lowered. there was.

In order to solve this problem, in the present invention, it is preferable that four photodiodes 111, 112, 113, and 114, which are light-receiving elements, are integrated into one wafer chip. Of course, the four photodiodes 111, 112, 113, and 114 may be integrated together with their driving circuits. As the four photodiodes 111, 112, 113, and 114 are integrated into a single wafer chip, the difference in performance between the photodiodes 111, 112, 113, and 114 is reduced, resulting in an excellent common-mode rejection ratio (Common-Mode Rejection). Ratio, CMRR) can be achieved, and thus the overall performance of the fully balanced photodetector 100 can be improved by reducing the noise of the optical signal.

The transimpedance amplifiers 120, 130, 140, and 150 reduce noise while amplifying electrical signals generated by the photodiodes 111, 112, 113, and 114 (hereinafter referred to as "first action"). . At this time, the transimpedance amplifiers 120, 130, 140, and 150 must simultaneously satisfy low noise characteristics and signal amplification characteristics, and then determine characteristics of electrical signals in the circuit. At this time, four transimpedance amplifiers 120, 130, 140, and 150 are provided to be connected to correspond to the photodiodes 111, 112, 113, and 114.

In the transimpedance amplifiers 120, 130, 140, and 150, lines through which output signals of the photodiodes 111, 112, 113, and 114 are transmitted are connected to inputs one by one, and noise is removed while amplifying the input signals. That is, the output signal of the first photodiode 111 is transmitted to the first transimpedance amplifier 120 and the first action occurs, and the output signal of the second photodiode 112 is transmitted to the second transimpedance amplifier 130. is delivered and the first action occurs. In addition, the output signal of the third photodiode 113 is transmitted to the third transimpedance amplifier 130 and the first action occurs, and the output signal of the fourth photodiode 114 is transmitted to the fourth transimpedance amplifier 140. is delivered and the first action occurs.

For example, each of the transimpedance amplifiers 120, 130, 140, and 150 may have an output signal of each photodiode 111, 112, 113, and 114 input to an inverting input, and a non-inverting input may be connected to ground. . In addition, a feedback resistor may be connected between an output and an inverting input of each of the transimpedance amplifiers 120, 130, 140, and 150, and a capacitor may be additionally connected to the feedback resistor. Of course, if necessary, other additional elements such as resistors are provided between the output signal line of each photodiode 111, 112, 113, and 114 and the inverting input of each transimpedance amplifier 120, 130, 140, and 150. may be connected.

Among the four transimpedance amplifiers 120, 130, 140, and 150, the output signals of the two first and second transimpedance amplifiers 120 and 130 are combined and transferred to the non-inverting amplifier 160, and the remaining 2 Each output signal of the third and fourth transimpedance amplifiers 140 and 150 is transferred to the inverting amplifier 170 while being summed.

The non-inverting amplifier 160 performs non-inverting amplification on each output signal of the first and second transimpedance amplifiers 120 and 130 . That is, a line through which the respective output signals of the first and second transimpedance amplifiers 120 and 130 are combined is input to the non-inverting input of the non-inverting amplifier 160 and the inverting input of the non-inverting amplifier 160 is grounded. While connected, non-inverting amplification is performed on the combined output signal. In addition, a feedback resistor R _V1 may be connected between the output and the non-inverting input of the non-inverting amplifier 160 . Of course, other additional elements such as resistors may be connected between the output signal lines of the first and second transimpedance amplifiers 120 and 130 and the non-inverting input of the non-inverting amplifier 160, if necessary.

The inverting amplifier 170 performs inverting amplification on each output signal of the third and fourth transimpedance amplifiers 140 and 150 . That is, the line through which the respective output signals of the third and fourth transimpedance amplifiers 140 and 150 are combined is input to the inverting input of the inverting amplifier 170 and the non-inverting input of the inverting amplifier 170 is connected to the ground. Inversion amplification is performed on the summed output signal. In addition, a feedback resistor R _V2 may be connected between the output and the inverting input of the inverting amplifier 170 . Of course, other additional elements such as resistors may be connected between the output signal lines of the third and fourth transimpedance amplifiers 140 and 150 and the inverting input of the inverting amplifier 170, if necessary.

In the differential amplifier 180, the line through which the output signal of the non-inverting amplifier 160 is transmitted is input to the first input, the line through which the output signal of the inverting amplifier 170 is transmitted is input to the second input, and the first input A voltage difference between the signal and the second input signal is amplified. At this time, one of the inverting input and the non-inverting input of the differential amplifier 180 is the first input and the other is the second input.

Thereafter, a signal output after being differentially amplified by the differential amplifier 180 may be used to detect information about an optical signal received by the optical receiver 110 . For example, the signal processing unit of the LiDAR may process information on the received optical signal by using the output signal of each cell of the receiving unit, that is, the output signal of the differential amplifier 180.

That is, in the present invention, the signal phases of the output signals of two photodiodes are inverted through the inverting amplifier 170, and the signal phases of the output signals of the remaining two photodiodes are maintained through the non-inverting amplifier 160. . As such, the two signals having opposite signal phases may be additionally amplified through the differential amplifier 180 .

Meanwhile, the feedback resistance R _V1 of the non-inverting amplifier 160 and the feedback resistance R _V2 of the inverting amplifier 170 may be implemented as variable resistors, respectively. In this case, the non-inverted signal input to the first input of the differential amplifier 180 and the inverted signal input to the second input of the differential amplifier 180 are obtained by adjusting the resistance of the variable resistors R _V1 and R _V2 . As the ratio is adjusted, the degree of amplification can be easily adjusted. Accordingly, according to the present invention, an output signal can be amplified through circuit control, such as adjusting the resistance of the variable resistors R _V1 and R _V2 , to reduce the intensity of an optical signal that can be weakened due to external factors. In addition, excellent accuracy and deep resolution can be implemented while noise is reduced between the non-inverted signal and the inverted signal through the difference amplifier 180 .

In particular, the optical signal transmitted to the light receiving unit 110 may be a frequency modulation continuous wave (FMCW) optical signal or a LiDAR optical signal.

3 shows a configuration diagram of a lidar 1 according to an embodiment of the present invention.

Meanwhile, the lidar 1 according to an embodiment of the present invention is a sensor device capable of generating information about an object OB using laser light. For example, lidar 1 may be implemented as a driven or non-driven type. In the case of a driving type, it is rotated by a motor and can detect an object OB around it. In the case of a non-driving type, an object OB located within a predetermined range may be detected by optical steering.

In addition, the lidar 1 detects the object OB based on a time of flight (TOF) method or a phase-shift method through laser light, and the position of the detected object OB, the detected object ( OB) and relative speed can be detected. For example, lidar 1 may be disposed at an appropriate location, such as a vehicle, in order to detect an object OB located in the front, rear, or side. In this case, the vehicle may be an autonomous vehicle or may be equipped with an Advanced Driver Assistance System (ADAS), etc., and autonomous driving operation or vehicle driver may be performed using information detected by lidar 1. Auxiliary actions and the like can be performed.

Specifically, lidar 1 may include a transmitter 10, a receiver 20, and a signal processing unit 30, as shown in FIG.

The transmitter 10 is a component that generates laser light such as FMCW (Frequency Modulation Continuous Wave) and transmits it to the object OB. In this case, the transmitter 10 may include a light source unit that generates laser light and an optical system that controls a path of laser light incident from the light source unit. For example, the optical system may include various lenses, mirrors, or scanners, but is not limited thereto.

That is, the light source unit may generate laser lights having the same wavelength or different wavelengths. For example, the light source unit may generate laser light having a specific wavelength or capable of tunable wavelength in various wavelength regions, and may be implemented using a semiconductor laser diode capable of small size and low power, but is not limited thereto.

The receiver 20 is a component that receives light reflected from the object OB. For example, the receiver 20 converts light reflected from the object OB into electricity using a photoelectric conversion element such as a photodiode. It can be converted into a specific signal (current, etc.). In this case, the measurement angle of the receiver 20 may be referred to as Field Of View (FOV). In addition, the receiver 20 may include an optical system for adjusting a path of reflected and received light. For example, the optical system may include various lenses or mirrors, but is not limited thereto.

The signal processing unit 30 is a component that processes signals for light of the transmitter 10 and the receiver 20 . That is, the signal processing unit 30 may include a processor that is electrically connected to the transmitter 10 and the receiver 20, processes a received signal, and generates data for the object OB based on the processed signal. can At this time, the signal processing unit 30 may calculate the separation distance of the object OB by collecting and processing data according to the corresponding light.

For example, the signal processor 30 may detect the distance, shape, etc. of the object OB by performing signal processing on the changed data using a time-of-flight (TOF) method, a phase-shift method, or the like. .

At this time, the TOF method measures the time for the pulse signal reflected from the object OB within the detection range to arrive at the receiver 20 after the laser pulse signal is emitted from the transmitter 10, thereby measuring the separation distance from the object OB. a way to measure In addition, the phase-shift method measures the amount of phase change of the signal reflected from the object OB within the detection range after emitting a laser beam that is continuously modulated with a specific frequency from the transmitter 10, It is a way to calculate the separation distance.

In particular, the balanced photodetector 100 described above according to FIGS. 1 and 2 may be included in the receiver 20 of the lidar 1 . That is, the receiver 20 may include a 3D sensor or a 4D sensor that receives and detects an optical signal reflected from the object OB. Such a 3D sensor or 4D sensor includes a plurality of cells, and each cell may be implemented using the balanced photodetector 100 .

In the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention is not limited to the described embodiments, and should be defined by the following claims and equivalents thereof.

1: lidar 10: transmitter
20: receiver 30: signal processing unit
100: balanced light detector 110: light receiving unit
111, 112, 113, 114: photodiode
120, 130, 140, 150: transimpedance amplifier
160: non-inverting amplifier 170: inverting amplifier
180: differential amplifier

Claims (10)

an optical receiver implemented as a pair of four photodiodes that convert optical signals into electrical signals and output them;
four transimpedance amplifiers that amplify input signals and remove noise by connecting lines through which the output signals of the photodiodes are transmitted to inputs one by one;
an inverting amplifier in which a line through which output signals of two transimpedance amplifiers are combined and transmitted is input to an inverting input to perform inverting amplification;
a non-inverting amplifier performing non-inverting amplification by inputting a line through which the output signals of the remaining two transimpedance amplifiers are combined and transmitted is input to a non-inverting input; and
A differential amplifier having a first input input to a line through which the output signal of the inverting amplifier is transmitted and a line through which the output signal of the non-inverting amplifier is transmitted is input to a second input,
A balanced photodetector for detecting information about the optical signal using an output of the differential amplifier.
According to claim 1,
A balanced photodetector in which the four photodiodes are integrated in one wafer chip.
According to claim 1,
The four photodiodes have a balanced photodetector having an array structure of 2 rows and 2 columns (2×2).
According to claim 1,
A balanced photodetector in which signal phases of output signals of two photodiodes are inverted through the inverting amplifier, and signal phases of output signals of the remaining two photodiodes are maintained through the non-inverting amplifier.
According to claim 4,
The inverting amplifier and the non-inverting amplifier are each a balanced photodetector in which a feedback resistor is implemented as a variable resistor.
According to claim 5,
A balanced photodetector in which a ratio between an inverted signal input to the first input and a non-inverted signal input to the second input is adjusted by adjusting the resistance of each variable resistor.
A receiver including a plurality of cells for receiving an optical signal of FMCW (Frequency Modulation Continuous Wave),
The plurality of cells are implemented using a plurality of balanced photodetectors,
One balanced photodetector,
an optical receiver implemented as a pair of four photodiodes that convert optical signals into electrical signals and output them;
four transimpedance amplifiers that amplify input signals and remove noise by connecting lines through which the output signals of the photodiodes are transmitted to inputs one by one;
an inverting amplifier in which a line through which output signals of two transimpedance amplifiers are combined and transmitted is input to an inverting input to perform inverting amplification;
a non-inverting amplifier in which a line through which the output signals of the remaining two transimpedance amplifiers are combined and delivered is input to a non-inverting input to perform non-inverting amplification; and
A differential amplifier having a first input input to a line through which the output signal of the inverting amplifier is transmitted and a line through which the output signal of the non-inverting amplifier is transmitted is input to a second input,
A receiver for detecting information on the optical signal using an output of the differential amplifier.
According to claim 7,
A receiver used for the purpose of LiDAR.
According to claim 8,
The plurality of cells is a receiver implementing a 3D sensor or a 4D sensor of the lidar.
According to claim 7,
The four photodiodes have an array structure of 2 rows and 2 columns (2×2) and are implemented in an integrated manner in one wafer chip.

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